DESC:FIELD OF THE INVENTION

The present disclosure pertains to the realm of cryogenics and low-temperature physics. Specifically, it revolves around an apparatus designed for the efficient liquefaction of specific gases, including helium, hydrogen, and neon. Central to this apparatus is the utilization of a twin cold finger mechanical drive Gifford-McMahon (GM) cryocooler, an advanced refrigeration mechanism adept at achieving ultra-low temperatures. The invention amalgamates principles from various disciplines and technologies, encompassing cryocoolers, GM cryocoolers, gas liquefaction techniques, gas purification techniques, and heat exchanger systems. Its primary purpose is to harness the intricate properties of helium, hydrogen, and neon, facilitating their transition from gaseous to liquid states. In essence, the invention stands at the crossroads of cryogenic refrigeration, heat exchange methods, and the broader field of low-temperature physics.

BACKGROUND OF THE INVENTION

The contents discussed in these inventions related to a small-scale helium/ hydrogen/ neon liquefier using a twin cold finger mechanical drive GM cryocooler.
The current invention pertains to the field of a twin cold finger GM cycle cryocooler to produce liquid helium, liquid hydrogen, and liquid neon.
Liquid helium, liquid hydrogen, and liquid neon are essential for many laboratory and industrial applications. Helium gas is a by-product of natural gas production and has two isotopes namely Helium-4 and Helium-3. Helium-4 is the primary constituent of helium sources available on the Earth. Liquid helium is an essential cooling medium for several low-temperature applications including superfluid helium droplet spectroscopy, superconducting quantum interference devices, particle accelerators, construction of high-accuracy gyroscopes, etc. Moreover, major laboratory-based applications of liquid helium include cooling of low Tc superconducting magnets, MRI, Nuclear magnetic resonance (NMR), superconducting quantum infrared detectors (SQUIDs), infrared sensors, etc. A significant part of helium is produced in the USA and Russia, and is transported to other parts of the earth. As the quantity of helium is limited, its price is high and has increasing considerably over the past decades. Therefore, it is crucial to reliquefy and recondense the evaporated helium back to its liquid state and keep it safe for particular applications by minimizing the boil-off rate. The global deficiency of helium will create an adverse effect on low-temperature physics research, cryogenics research, space applications, military applications, and medical science activities, especially in MRI, fiber optics, space exploration, military rockets, etc.
Similarly, neon has three stable isotopes such as Ne20, Ne21, and Ne22. Stable isotopes of neon are produced in stars and have a wide variety of industrial applications. Liquid neon can be used as a cryogenic refrigerant in place of helium for gases whose normal boiling point is over 27.1 K. Liquid neon is also used as an intermediate cooling fluid for liquid helium and liquid hydrogen storage chambers to reduce the boil-off rate as discussed in US patent “US5005362A”. Liquid hydrogen is used as a green fuel for spacecraft, cars, buses, trucks, trains, etc. to avoid the emission of greenhouse gases. The hydrogen after combustion with oxygen does not radiate any harmful emissions into the atmosphere and releases water vapour as a by-product. Therefore, global interest is growing to use hydrogen as an alternative fuel, and liquid hydrogen has a higher volumetric energy density in comparison with compressed hydrogen, cryocompressed hydrogen storage, and solid storage hydrogen methods. Small quantities of hydrogen are also crucial for many laboratory experiments. Liquid hydrogen is more energy efficient in comparison with ammonia and results in fewer carbon footprints. Liquid hydrogen is also used as a fuel in cryogenic rocket engines since the beginning of the space programme. Therefore, it is essential to develop robust, reliable helium/ hydrogen/ neon liquefiers. Mostly, Collin cycle-based cryogenic plants are used for the production of liquid helium, and these plants produce higher quantities of liquid helium to meet the demand of laboratories. These Collin cycle plants and modified Claude cycle plants are installed in academic, R&D laboratories, and industries at a central facility to produce liquid helium and are transported into individual laboratories by small storage Dewar’s. The evaporated helium is collected in a gas storage balloon, purified, and again used in liquefiers. This will eliminate the wastage of helium. Precooled Linde-Hampson cycle and Claude cycle based large liquefaction plants are designed for the liquefaction of hydrogen. Liquid hydrogen produced in those plants mostly opted for space applications. These plants are coming under recuperative cryogenic refrigeration cycles. Also, small-scale helium, hydrogen, and neon liquefiers are developed using a two-stage GM cryocooler, pulse tube cryocooler, and hybrid GM-JT machines to produce liquid helium, liquid hydrogen, and liquid neon for small-scale applications. In this work, small-scale helium, hydrogen, and neon liquefier are described using a twin cold-finger GM cryocooler. As the twin cold finger GM cryocooler has two cold fingers, and both are driven by a common drive mechanism, this liquefier is expected to double the liquefaction rate with relatively small space. The major components of the liquefier are the gas supply line, cryogenic transfer lines, precooler unit, liquefaction unit, and an external liquid storage unit. The liquefaction unit adopts the twin cold finger GM cryocooler, which produces the desired refrigeration effect to refrigerate and ultimately liquefy the gas and constitute the heart of the liquefier. The proposed liquefier will also operate as liquefaction cum recondensation device, in which one cold finger act like liquefier and another act like recondensor. Additionally, a compact, reliable and portable liquid hydrogen generator has been designed, in which ultra-pure liquid hydrogen is directly produced from water by using both gas production and liquefaction mechanism.
In view of the foregoing discussion, it is portrayed that there is a need to have an apparatus for liquefaction of helium/hydrogen/neon using a twin cold finger mechanical drive GM cryocooler.

SUMMARY OF THE INVENTION

The present disclosure seeks to provide an apparatus for liquefaction of helium/hydrogen/neon using a twin cold finger mechanical drive GM cryocooler. The present invention is related to the development of a compact, robust small-scale liquid helium, liquid hydrogen, and liquid neon plant using a simple twin cold finger mechanical drive GM cryocooler. The liquefier contains four major components such as a gas supply unit, a pre-cooling unit, a liquefaction unit, and a liquid storage unit. Sometimes, the precooling unit may be avoided to make the overall system robust and eliminate the requirement for liquid nitrogen. Rather, precooling happens at the first stages of both upper and lower cold fingers of the twin cold finger GM cryocooler itself. The twin cold finger GM cryocooler produces the desired cooling effect at the refrigeration temperature to liquefy the gas. The liquefied gas is further collected and stored in an additional bulk storage Dewar and supplied to the end users. Further, different arrangements have been discussed to effectively transfer the refrigeration effect from the cryocooler to the cooling gas by using a coiled tube arrangement and fin-shaped arrangement. Also, a novel compact, portable liquid hydrogen generator concept has been proposed that can be used first to produce gaseous hydrogen from water by electrolysis, purification of hydrogen gas by removing moisture and oxygen traps, and then production of liquid hydrogen from gaseous hydrogen by the liquefaction unit. The major components of this plant are an electrolyzer, moisture, oxygen traps, precooler, liquefaction unit, and liquid hydrogen storage unit. Additionally, a liquefier cum recondensor concept has been proposed using a twin cold finger mechanically driven GM cryocooler, where the cooling capacity of the lower cold finger is used to liquefy the gas and the refrigeration capacity of the upper cold finger is used to recondense the evaporated gas from the external liquid storage Dewar.

In an embodiment, an apparatus for liquefaction of helium/hydrogen/neon using a twin cold finger mechanical drive GM cryocooler is disclosed. The apparatus includes a gas supply unit configured to supply pure gas from a pure gas cylinder or a production and purification unit selected from a group consisting of an electrolyzer and moisture and oxygen trap for pure hydrogen gas.
The apparatus further includes a precooling unit to cool the gas from ambient conditions to the liquid nitrogen temperature using LN2 as precooling fluid. The precooling happens either by adopting a single-stage twin cold finger mechanical drive GM cryocooler (which is a cryogen-free device) or by adopting a precooler Dewar. The precooler Dewar further contains two containers, an outer container, and an inner container. The annular gap between them is filled with several layers of MLI and vacuum insulation to reduce the convection and radiation heat load. The outer Dewar is made up of SS304 and provides support to the inner container. The inner Dewar contains the precooling fluid, preferably LN2. Spacers are provided in between the outer and inner container to provide the necessary structural support and are normally poor thermal conducting materials like Hylam/FRP. A coiled tube heat exchanger is placed inside the inner container, within which the gas passes and gets cooled. An intermediate flange may be used to reduce heat loss by conduction, and the intermediate flange is made up of low thermal conductivity materials like G-10. The upper flange further contain passages for the supply of LN2 to the inner container and a passage for the removal of evaporated LN2, two passages for the inlet and outlet of gas to and from the precooler Dewar, feed through for sensors, burst discs, safety valves, etc. In the case of hydrogen liquefaction, the coil tube heat exchanger needs to be filled with a catalyst to reduce the rate of energy liberation due to exothermic reaction because of ortho-para conversion of hydrogen. This is an additional requirement for hydrogen liquefaction plant and is not required for helium/ neon liquefaction plant.
The apparatus further includes a liquefaction unit, which contains a lower liquefaction Dewar, an upper liquefaction Dewar, a twin cold finger mechanically driven GM cryocooler, a helium compressor, and a water chillier. The lower liquefaction Dewar contains two containers, such as: an outer container, and an inner container, the interspace between them are filled with MLI and vacuum insulation to reduce the radiation heat loads. Similarly, the upper liquefaction Dewar contains two containers, such as: an outer container, and an inner container, the interspace between them are filled with MLI and vacuum insulation. The twin cold finger GM cryocooler contains a first-stage displacer housing, first-stage regenerator, first-stage heat exchanger, second-stage displacer housing, second-stage regenerator, second-stage heat exchanger, associated gas spaces, and related drive mechanisms as discussed in detail in German utility model “DE202023101843U1”. A supplementary heat exchanger is also adopted at the first stage heat exchangers of both lower and upper cold fingers to enhance the heat transfer area, and two condensers are attached at the second stage heat exchangers of both upper and lower cold fingers to condense the gas and produce the liquid. Different arrangements (e.g., coiled tube and fins) have been made to efficiently transfer the refrigeration effect from the cryocooler to the gas to enhance the cooling rate. This unit liquefies the gas.
The apparatus further includes a series of bare cryogenic transfer lines, insulated and vacuum-insulated cryogenic transfer lines to transfer the gas from one unit to another unit of the liquefaction system. A bare transfer line is used to transfer the gas from the supply unit to the precooler unit. Insulated cryogenic transfer lines are used to transfer the liquid between precooler Dewar to liquefaction Dewars, and liquefaction Dewars to bulk liquid storage Dewar.
The apparatus further includes a plurality of safety and regulatory components selected from a number of safety valves, burst discs, relief valves, regulatory valves, V-J regulatory valves, level sensors, temperature sensors, needle valves, pressure sensors, flow meters, and depressurization valves at different locations of the liquefaction system.
The apparatus further includes an external bulk liquid storage unit that stores the liquid product (i.e., liquid helium /hydrogen /neon) after its liquefaction. This also contains two containers, such as an outer container and an inner container. The interspace between them is filled with MLI and vacuum insulation to reduce the convective and radiative heat load. This unit stores the liquid cryogen and is delivered to the end user upon requirement. This Dewar can also be three container configuration and intermediate layer hold liquid nitrogen to reduce the boil-off rate.
The liquefier discussed above can also be modified to use as a cryogen-free system. This can be made by removing the precooler Dewar; this eliminates the requirement of LN2. The precooling and liquefaction happen at both upper and lower liquefaction Dewars by absorbing the refrigeration capacities of both upper and lower cold fingers of twin cold finger mechanically driven GM cryocooler at the respective first-stage heat exchangers. As certain cooling capacities of the cryocooler will be utilized for the precooling, its cooling performance will be lower compared to the previous liquefaction plant. However, the theoretical simulation shows that its effect will be minimum.
The liquefier can further be modified to use two precooling Dewars. Both precooling Dewar are similar in structural configuration. One precooling Dewar will be used to cool the gas for the lower liquefaction Dewar and another precooling Dewar will be used to cool the gas for the upper liquefaction Dewar. This will enhance the complexity of the system but does not create significant enhancement in the yield rate of the overall system as evident from theoretical simulation.
The liquefier can be further modified by replacing the two-stage twin cold finger GM cryocooler of the liquefaction unit with a single-stage twin cold finger high-capacity mechanically driven GM cryocooler. Heat pipes and heat exchangers can be attached at the cold heat exchangers of both upper and lower cold fingers to enhance the rate of heat transfer and this unit will not be able to produce liquid helium. But, this can produce liquid neon and liquid hydrogen based on the cooling capacity of the cold fingers of cryocooler.
The liquefier can be further modified by replacing the LN2 precooled precooling Dewar with another single-stage twin cold finger mechanically driven GM cryocooler and vacuum chambers for both lower and upper cold finger units. Here, the gas will be pre-cooled by absorbing the refrigeration capacity of the first stage lower cold finger and first stage upper cold finger for lower liquefaction Dewar and upper liquefaction Dewar respectively.
The liquefier can be further modified by replacing the second-stage condenser of upper liquefaction Dewar. Thus, the gas can be cooled in the upper cold finger of the twin cold finger of the mechanically driven GM cryocooler, and after cooling it will be supplied to the lower liquefaction Dewar for liquefaction in the lower condenser. Thus, the plant can be oriented in the vertical direction; however, it will increase the load on the bottom condenser and this needs to be designed carefully.
The liquefier can further be modified as a liquefaction-recondensation unit. Here, the lower cold finger will act as a liquefier to liquefy the gas, and the upper cold finger will act as a recondenser to recondense the evaporated liquid from the bulk liquid storage container and convert it to liquid and resend it to the external storage Dewar. This will be able to minimize the boil-off loss of the external bulk storage container and helps to keep the model in a vertical orientation.
The liquefier further contains valves in the supply lines, through which the liquefaction rates of lower and upper liquefaction Dewar can be controlled by adjusting the opening and closing of regulating valves.
A robust portable hydrogen liquefaction plant produces a small quantity of ultrapure liquid hydrogen from water using both an electrolyzer and a liquefaction unit. This proposed machine uses both inbuilt pure hydrogen gas production and liquefaction units. The hydrogen gas production unit consists of an on-board electrolyzer that produces hydrogen and oxygen from water via/by electrolysis. The oxygen that is produced from the electrolysis gets trapped by an oxygen trap and eliminates/removes from the system. A moisture trap is also provided to trap the moisture which is produced from electrolysis. Moisture concentration and oxygen concentration measuring sensors are adopted to measure the moisture and oxygen level. A hydrogen purity meter is kept to detect the purity level of hydrogen and if it is found within the required purity level, then hydrogen is allowed to pass through the liquefaction unit, otherwise, it will be stored in the gas storage space. The liquefaction unit is any one of the liquefaction arrangements as described in this invention, however only two has been presented to minimize the length of report. The liquefaction unit consists of a precooler unit, a liquefaction unit, and a bulk liquid storage unit. The pre-cooling unit can also be removed from the system to make it a cryogen-free portable hydrogen liquefier. In the absence of precooling Dewar, gas will get precooled at the first stage of the cylinder and first-stage heat exchanger by absorbing certain refrigeration capacity. However, this will create certain adverse effect on the liquefaction rate by reducing its performance. The pre-cooling unit consists of an inner container, an outer container, a coiled tube for gas passages, an upper flange, an intermediate flange, measuring sensors, and safety equipment. The liquefaction unit consists of a two-stage twin cold finger mechanically driven GM cryocooler, a helium compressor, a water chillier, a lower liquefaction Dewar, and an upper liquefaction Dewar. Lower and upper liquefaction Dewars contains an inner container, an outer container, adequate gas flow passages, safety valves, vacuum ports, etc. The liquid hydrogen from both the upper and lower liquefaction Dewar will be transported to an external bulk hydrogen storage Dewar and stored for end users. The external bulk hydrogen storage Dewar also consists of an outer Dewar and an inner Dewar, and the interspace among them is filled with vacuum insulation and MLI to reduce external heat leakage by convection and radiation. Appropriate cryogenic transfer lines and a series of different regulating valves, needle valves, safety valves, etc. are provided at different locations of the plant to regulate the flow rate, safety measures, monitor the gas flow rates, etc.
The hydrogen liquefaction plant can be converted into hydrogen liquefaction and recondensation unit by replacing the upper liquefaction unit to as recondensation unit. Here, the lower cold finger will liquefy the gas and the upper cold finger will recondense the evaporated hydrogen to liquid hydrogen.
An object of the present disclosure is to introduce a pioneering approach in creating a small-scale cryogenic plant that leverages a twin cold finger mechanical drive GM cryocooler for the efficient liquefaction of helium, hydrogen, and neon gases.
Another object of the present disclosure is to innovate a compact helium, hydrogen, and neon liquefaction and recondensation unit, driven by the precision and efficiency of a twin cold finger mechanical GM cryocooler, paving the way for enhanced scalability in cryogenic operations.
Another object of the present disclosure is to conceptualize and realize a compact, portable liquid hydrogen generator, capable of initiating an end-to-end process that starts with hydrogen gas production from water through electrolysis, purification of the produced gas, and culminates in its liquefaction, all enabled by the twin cold-finger mechanical drive GM cryocooler-based hydrogen gas liquefier.
Yet another object of the present invention is to deliver an expeditious and cost-effective dedicated liquefaction unit or cold box that stands as the epicenter for the conversion of helium, hydrogen, and neon gases into their liquid states, ensuring high efficiency and purity in the liquefaction process.
To further clarify the advantages and features of the present disclosure, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail in the accompanying drawings.

BRIEF DESCRIPTION OF FIGURES

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read concerning the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustrates a schematic of a basic architecture cryogenic liquefaction apparatus, in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a schematic of a helium/ hydrogen/ neon liquefier using coiled tube heat exchanger mechanism (the radiation shield is attached at the top flange of the liquefier Dewar);
Figure 3 illustrates a schematic of a helium/ hydrogen/ neon liquefier using coiled tube heat exchanger mechanism (the radiation shield is attached at the first-stage heat exchanger of the liquefier Dewar);
Figure 4 illustrates a schematic of a helium/ hydrogen/ neon liquefier using fin heat exchanger mechanism (the radiation shield is attached at the top flange of the liquefier Dewar);
Figure 5 illustrates a schematic of a helium/ hydrogen/ neon liquefier using fin heat exchanger mechanism (the radiation shield is attached at the first-stage heat exchanger of the liquefier Dewar);
Figure 6 illustrates a schematic of a hydrogen/ neon liquefier using single-stage twin cold finger GM cryocooler and heat transfer enhancement mechanism;
Figure 7 illustrates a schematic of a helium/ hydrogen/ neon liquefaction and recondensation unit using twin cold-finger GM cryocooler (coiled tube arrangement in bottom liquefier);
Figure 8 illustrates a schematic of a helium/ hydrogen/ neon liquefier without using pre-cooler unit and using coiled tube heat exchanger mechanism;
Figure 9 illustrates a schematic of a helium/ hydrogen/ neon liquefier without using pre-cooler unit and using fin heat exchanger mechanism;
Figure 10 illustrates a schematic of a helium/ hydrogen/ neon liquefier without using pre-cooler unit and single condenser;
Figure 11 illustrates a schematic of a helium/ hydrogen/ neon liquefier using coiled tube heat exchanger mechanism and two precooler units;
Figure 12 illustrates a schematic of a helium/ hydrogen/ neon liquefier using fin heat exchanger mechanism and two precooler units;
Figure 13 illustrates a schematic of a helium/ hydrogen/ neon liquefaction and recondensation unit using twin cold-finger GM cryocooler (Fin type heat exchanger arrangement);
Figure 14 illustrates a schematic of a helium/ hydrogen/ neon liquefier using coiled heat exchanger mechanism and single-stage twin cold finger GM cryocooler as a precooler unit. (Two single stage GM cryocoolers can also be utilized as precoolers);
Figure 15 illustrates a schematic of a helium/ hydrogen/ neon liquefier using finned heat exchange mechanism and single-stage twin cold finger GM cryocooler as a precooler unit;
Figure 16 illustrates a compact liquid hydrogen generator with two LN2 precooler;
Figure 17 illustrates a compact liquid hydrogen generator using single-stage twin cold finger GM cryocooler as precooler;
Figure 18 illustrates an architectural model of a two-stage twin cold finger mechanically driven GM cryocooler;
Figure 19 illustrates an architectural model of a typical LN2-cooled precooler (safety valve, burst disc, and sensors are not shown in assembly drawings);
Figure 20 illustrates an architectural model of a typical single-stage twin cold finger driven mechanical drive GM cryocooler as a cryogen-free precooler (compressor and water chiller are not shown);
Figure 21 illustrates an architectural model of a typical liquefaction unit/cold box (compressor and water chiller are not shown);
Figure 22 illustrates an architectural model of some essential parts of the cold box. Outer container, inner container, two-stage twin cold finger driven mechanical drive GM cryocooler with condensers at both cold fingers;
Figure 23 illustrates an architectural model of some typical condensers used in second-stage heat exchangers of twin cold finger mechanical drive GM cryocoolers;
Figure 24 illustrates an architectural model of a typical liquefaction unit/cold box unit for vertical orientation, liquefaction-recondensation plant (compressor and water chiller are not shown); and
Figure 25 illustrates an architectural model of a typical external liquid storage Dewar and its components.

Further, skilled artisans will appreciate those elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

DETAILED DESCRIPTION:

To promote an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present disclosure will be described below in detail concerning the accompanying drawings.

Referring to Figure 1, a block diagram of schematics of a basic cryogenic liquefaction device is illustrated in accordance with an embodiment of the present disclosure. The apparatus 100 includes a gas supply unit 102 configured to supply pure gas from a high-pressure storage cylinder 102A or a gas production and purification unit (102B) selected from a group consisting of an electrolyzer and moisture and oxygen trap for pure hydrogen gas.

In an embodiment, a precooling unit (104) is connected with the gas supply unit and operable to cool received gas from ambient conditions to a liquid nitrogen temperature using liquid nitrogen (LN2) as a precooling fluid (104A).
The precooling unit (104) comprising a single-stage twin cold finger mechanical drive Gifford-McMahon (GM) cryocooler (104B), or a precooler Dewar comprising an outer container and an inner container with an annular gap filled with multilayer insulation (MLI) and vacuum insulation, the inner container holding LN2 and a coiled tube heat exchanger for gas cooling.
In one embodiment, a plurality of spacers is provided in between the outer and inner container to provide structural support and normally poor thermal conducting materials preferably Hylam/FRP.
In one embodiment, a coiled tube heat exchanger is placed inside the inner container, within which the gas passes and gets cooled.
In one embodiment, an intermediate flange reduces heat loss by conduction, the flange further contains passages for the supply of LN2 to the inner container and a passage for removal of evaporated LN2, two passages for the inlet and outlet of gas to and from the precooler Dewar, feed through for sensors, burst discs, and safety valves, wherein in case of hydrogen liquefaction, the heat exchanger needs to be filled with a catalyst to reduce a rate of energy liberation due to exothermic reaction because of ortho-para conversion of hydrogen.

In an embodiment, a liquefaction unit (106) comprising an upper and lower liquefaction Dewar, each having an outer container and an inner container with interspaces filled with MLI and vacuum insulation to reduce radiation heat loads.
In one embodiment, a twin cold finger is mechanically driven GM cryocooler (104B) contains a first-stage displacer housing, first-stage regenerator, first-stage heat exchanger, second-stage displacer housing, second-stage regenerator, second-stage heat exchanger, associated gas spaces, and related drive mechanisms.
In one embodiment, a supplementary heat exchanger is adopted at the first stage heat exchangers of both lower and upper cold fingers to enhance heat transfer area, and two condensers are attached at the second stage heat exchangers of both upper and lower cold fingers to condense gas and produce the liquid.
In one embodiment, a helium compressor, and a water chillier, wherein different arrangements selected from coiled tubes and fins have been made to efficiently transfer the refrigeration effect from the cryocooler (104B) to the gas to enhance a cooling rate.

In an embodiment, a series of transfer lines, comprising bare, insulated, and vacuum-insulated lines, to transfer gas between units of the liquefaction unit (106), wherein the bare transfer line is used to transfer the gas from the supply unit to the precooler unit, the insulated cryogenic transfer lines are used to transfer the liquid between precooler Dewar to liquefaction Dewars, and liquefaction Dewars to bulk liquid storage Dewar.

In one embodiment, a plurality of safety and regulatory components are selected from a number of safety valves, burst discs, relief valves, regulatory valves, V-J regulatory valves, level sensors, temperature sensors, needle valves, pressure sensors, flow meters, and depressurization valves at different locations.

In one embodiment, an external bulk liquid storage unit (108) that stores the liquid product including helium, hydrogen, and neon after liquefaction, wherein the external bulk liquid storage unit (108) contains two containers, such as an outer container and an inner container, wherein an interspace between the outer and inner container is filled with MLI and vacuum insulation to reduce a convective and radiative heat load, wherein the external bulk liquid storage unit (108) stores liquid cryogen and is delivered to an end user upon requirement.

In another embodiment, the precooler Dewar is removed to configure the apparatus as a cryogen-free system, thereby eliminating usage of LN2, wherein the precooling and liquefaction processes are performed in both upper and lower liquefaction Dewars by utilizing refrigeration capacities from the upper and lower cold fingers of a twin cold finger mechanically driven GM cryocooler (104B), specifically at first-stage heat exchangers, wherein a portion of the cryocooler's cooling capacity is allocated for a precooling process, resulting in a reduction in overall cooling performance, wherein any reduction in cooling performance due to allocation of a cryocooler's cooling capacity for precooling is substantively offset, as evidenced by theoretical simulations indicating minimal adverse effect.

In another embodiment, the apparatus further modified to comprise two precooling Dewars, each having a similar structural configuration, wherein one of the precooling Dewars is dedicated to cooling gas for the lower liquefaction Dewar, and another precooling Dewar is dedicated to cooling gas for an upper liquefaction Dewar, wherein incorporation of two precooling Dewars results in an increased system complexity, wherein a modification leading to the increased complexity does not significantly enhance a cooling rate.

In another embodiment, the two-stage twin cold finger GM cryocooler (104B) of the liquefaction unit (106) is replaced by a single-stage twin cold finger high-capacity mechanically driven GM cryocooler (104B), wherein heat pipes and heat exchangers attached to cold heat exchangers of both upper and lower cold fingers, the configuration being adapted to enhance a rate of heat transfer, wherein a modified apparatus is not configured to produce liquid helium, wherein the apparatus is capable of producing liquid neon and liquid hydrogen, the production being contingent upon a cooling capacity of the cryocoolers.

In another embodiment, the LN2 precooled precooling Dewar is replaced by a single-stage twin cold finger mechanically driven GM cryocooler (104B), wherein the precooling Dewar further comprising vacuum chambers associated with both the lower and upper cold finger units, wherein gas pre-cooling occurs through absorption of a refrigeration capacity from the first stage of the lower cold finger for the lower liquefaction Dewar, and the first stage of the upper cold finger for the upper liquefaction Dewar.

In another embodiment, the second-stage condenser of the upper liquefaction Dewar is replaced, facilitating cooling of the gas in the upper cold finger of the twin cold finger mechanically driven GM cryocooler, wherein, post-cooling in the upper cold finger, the gas is supplied to the lower liquefaction Dewar for subsequent liquefaction within the lower condenser, wherein a configuration permits a vertical orientation of the plant, wherein vertical orientation results in an increased load on a bottom condenser.

In another embodiment, the apparatus further configured as a liquefaction-recondensation unit, wherein the lower cold finger functions as a liquefier to convert the gas to a liquid state, and the upper cold finger operates as a condenser, designed to recondense evaporated liquid originating from the bulk liquid storage container, converting it back to liquid form and directing it to an external storage Dewar, such a configuration being conducive to minimizing boil-off loss from an external bulk storage container and allowing for a vertical orientation of the apparatus.

In another embodiment, the apparatus further comprises valves positioned within supply lines, wherein liquefaction rates of both the lower and upper liquefaction Dewars are adjustable through a modulation of the regulating valves.

In another embodiment, the apparatus further comprises a portable hydrogen liquefaction plant system, adapted to derive a specific quantity of liquid hydrogen from water comprises an on-board electrolyzer configured to electrolytically dissociate water, producing hydrogen and oxygen.
In one embodiment, an oxygen trap functionally is designed to capture the produced oxygen and remove it from the system.
In one embodiment, a moisture trap is used to sequester moisture resulting from an electrolysis process.
In one embodiment, sensors are used to determine moisture and oxygen concentrations, providing feedback on system status.
In one embodiment, a hydrogen purity meter is used to detect a purity of the produced hydrogen, wherein if purity meets a user-defined criteria, the hydrogen is directed to the liquefaction unit (106), otherwise, it's stored in a designated gas storage space, wherein the liquefaction unit (106), which may be in line with previously described liquefaction configurations, comprising a precooler unit, which may optionally be excluded for a cryogen-free configuration, further consisting of an inner container, an outer container, a coiled tube for gas flow, an upper flange, an intermediate flange, measurement sensors, and safety mechanisms.
In one embodiment, a primary liquefaction system, inclusive of a two-stage twin cold finger mechanically driven GM cryocooler (104B), a helium compressor, a water chiller, and both lower and upper liquefaction Dewars, each Dewar consisting of an inner and outer container, gas flow pathways, safety valves, and vacuum ports;
In one embodiment, an external bulk hydrogen storage Dewar, equipped with outer and inner containers separated by a space filled with vacuum insulation and MLI to minimize external heat leakage, configured to store the liquefied hydrogen for subsequent use, wherein cryogenic transfer lines and a series of different regulating valves, needle valves, and safety valves are provided at different locations of the plant to regulate a flow rate, safety measures, and monitor the gas flow rates.

In another embodiment, the system is converted into hydrogen liquefaction and recondensation unit by replacing the liquefaction unit (106), wherein the lower cold finger liquefies the gas and the upper cold finger recondenses evaporated hydrogen to liquid hydrogen, wherein the liquefaction unit (106) of the hydrogen plant replaced by the liquefaction unit to make it cryogen-free, and reliable operation.

It consists of a gas supply unit 102, a pre-cooling unit, a liquefaction unit (106), and a storage unit (108). All units are connected among themselves by employing cryogenic transfer lines. The transfer line may be a rigid transfer line, a flexible transfer line, a bare transfer line, an insulated transfer line, a super-insulated transfer line, or vacuum jacket insulated transfer line depending upon its requirement. For example, a bare transfer line is used for the transfer of helium/ nitrogen gas; however, an insulated cryogenic transfer line is used for the transfer of liquid helium, liquid nitrogen, etc. The gas supply unit 102 will supply the pure gas, which will be liquefied. The pre-cooling unit will cool the working gas before its entry to the main liquefaction unit. Therefore, the gas will be cooled from ambient temperature to liquid nitrogen temperature (if liquid nitrogen is used as precooling fluid 104A) and will reduce the extra cooling load on the liquefaction unit. The liquefaction unit holds the cryocooler (i.e., the twin-cold finger mechanically driven GM cryocooler in this liquefaction plants) to produce the required cooling effect to liquefy the gas. After liquefaction, the liquefied gas will be collected and stored in the liquefaction container associated with the liquefaction unit. The liquefied cryogenic fluid will be subsequently transferred to the external storage Dewar for its storage and distribution to the end users. The gas supply unit 102 may be either a high-pressure cylinder that is filled with pure gas (purity level~99.999), or a comprehensive system consisting of a gas production and purification unit (102B) to generate the gas at desired purity level. The earlier liquefier reported in reference “Helium liquefaction with a commercial 4 K Gifford-McMahon cryocooler. Cryogenics, 2006, 46(11), 799-803; Experimental study on small-scale hydrogen liquefaction of 0.5 L/h. International Journal of Hydrogen Energy, 2022, 47(90), 38258-38270; Initial test results of laboratory scale hydrogen liquefaction and densification system. In AIP Conference Proceedings, 2006, Vol. 823, No. 1, pp. 1530-1537) ” uses a single GM cryocooler to produce the desired cooling effect to produce liquid hydrogen, and liquid helium. However, the current invention adopts the novel twin cold finger GM cryocooler to produce the desired cooling effect for the liquefaction of gas. As mentioned earlier, the twin cold finger cryocooler has two cooling stations positioned in an axially opposite direction, thus, it will double the liquefaction rate.

Figure 2 illustrates schematics of a helium/ hydrogen/ neon liquefier using a coiled tube heat exchanger mechanism (the radiation shield is attached at the top flange of the liquefier Dewar). This is a two-stage cryocooler, which has certain refrigeration capacity at a temperature of 4.2 K. The boiling point of helium, hydrogen and neon are 4.2 K, 20.28 K and 27.1 K respectively in ambient pressure conditions. Thus, these gases can be easily liquefied by using the current liquefier. However, the liquefaction mechanism of only helium and hydrogen is explained in detail here, and the liquefaction of other gases like neon will follow a similar process with helium. The gas cylinder 1, which is at high pressure, is depressurized through a pressure reducing valve 2 to reduce its pressure to the desired operating pressure. It is assumed that the gas is at a purity of ~99.999%. Then it passes through a flow meter 3 to measure its flow rate. Additionally, the gas will pass through the needle valve 4, cut-off valve 5, and other regulating valves upon requirement before it enters the precooler unit 6. In between those lines, a gas purity meter may be positioned (not shown here) to show the purity level of the gas, and if its value falls to the desired level, the unit may be shut off by showing an error message in the central PLC circuit. The precooler 6 is a double-walled vacuum-insulated Dewar used to cool the incoming gas. The inner container 6b stores the liquid nitrogen (liquid nitrogen is used as precooling fluid 104A) and a coil tube heat exchanger 7 through which the gas flows. When the gas flows through the heat exchanger it gets cooled. If the gas is hydrogen, then the coil tube heat exchanger 7 is filled with a catalyst. A liquid nitrogen supply line and discharge line 8 is provided through which LN2 is communicated to the precooled Dewar 6 from external sources. The outer container 6a supports the inner container. In between both inner and outer Dewar, MLI is provided to reduce the radiation heat loss, and vacuum insulation (by vacuum pump 29) is opted to reduce the convection heat loss. Supporting spacers of Hylam will be used in between outer and inner container and is not shown in the figure. A level sensor and temperature sensor stick will be attached to this Dewar to detect the level of LN2 and temperature at different locations. After cooling, the cooled gas will exit through a vacuum jacket-insulated transfer line 9, to reduce any external heat leakage from the cooling fluid. From here the transfer line is divided into two vacuum jacket transfer lines by a T- joint. One part of the cooling fluid will flow to the lower/bottom liquefaction Dewar 12 and the other to the upper/top liquefaction Dewar 32. The flow rates of gas to the lower and upper liquefier Dewar are controlled by valves 10 and 11 respectively. Both valves are vacuum-jacketed valves and their operation can be controlled manually, or by replacing automated solenoid valves. Both lower and upper liquefaction Dewar’s are similar in structural configuration and are placed in an opposite direction. The lower Dewar contains the refrigeration unit 13 of the lower cold finger and the upper liquefier Dewar contains the refrigeration unit 34 of the upper cold finger. Both Dewar’s are similar in structural configuration, hence the configuration of only lower Dewar is discussed below. The lower liquefier Dewar 12 contains two containers, such as the inner container 12b and outer container 12a, and the annular gap between them is filled with multi-layer insulation and vacuum insulation. The multilayer insulation is provided by aluminized Mylar which reduces the radiation heat loss, and the vacuum insulation is provided by a vacuum pump 30 to reduce the convection heat loss. Spacers of lower thermal conductivity material like Hylam are kept as supporting material and are not shown in figure. The inner container 12b further contains a safety valve, relief valve, burst disk, vent valve, level sensor, and temperature sensors in a stick, and these are not shown in the figure. The liquefier Dewar 12b contains the room temperature portion of the cryocooler 19 through the upper vacuum flange. The upper flange can be replaced with an intermediate vacuum flange, which contains some low-thermal conductivity material to reduce heat loss. The lower refrigeration portion 13 of the GM cryocooler consists of a first-stage lower cylinder 14, first-stage lower cold heat exchanger 15, second-stage lower cylinder 16, and second-stage lower cold heat exchanger 17. The first-stage lower cylinder heat exchanger 15 is further attached to a heat exchanger (not shown in the figure) to enhance the heat transfer area. The second-stage lower cylinder heat exchanger 17 is attached to a lower condenser 18 to condense the fluid to produce the liquid. The precooled gas from the precooler is directly sent to the first-stage cold heat exchanger through a small pipe (of typical diameter 2.4 mm) to get further cooled, and then it passes over a coiled tube wound over the second-stage cylinder (it is soldered over the second stage lower cylinder). Thus, the gas gets further cooled, and finally, it is cooled over the second-stage heat exchanger and passes through the condenser. At the condenser, the gas is liquefied and the liquid is collected and stored in the inner Dewar 12b. A radiation shield 22 is attached at the neck of the inner Dewar to reduce the radiation heat leak. The liquid is then transferred from the lower liquefier Dewar 12b to the bulk liquid storage Dewar 25 through the vacuum-insulated cryogenic transfer line 23, and the flow rate is controlled by valve 24. The upper liquefier Dewar 32 contains the upper refrigeration portion 34 of the twin-cold finger GM cryocooler, which includes the upper first-stage cylinder 35, upper-first stage heat exchanger 36, upper second-stage cylinder 37, and upper second-stage cold heat exchanger 38 and upper condenser 39. The upper-first stage heat exchanger 36 is also attached with an additional heat exchanger (not shown in figure) to increase the heat transfer area. The warm ends of both the upper refrigeration portion and lower refrigeration portion are connected with the common driving mechanism within the room temperature portion of the cryocooler 19. The common drive mechanism further holds the gear drive mechanism to generate the displacer movement, and the valve unit (which is either a rotary valve or solenoid valves) to generate the pressure pulses in both the lower and upper gas chambers. The warm end portion is also attached with a helium compressor 20 to get compressed helium gas. The helium compressor further contains a scroll helium capsule, oil separator, adsorbers, heat exchangers, and associated valves. The cooling water to the helium compressor is provided by external water chillier 21. The cold heads of both cryocoolers contain displacers, compression chambers, expansion chambers, etc. and are well known to the researchers of this field. A portion of the cooling gas from the precooler 6 passes to the upper liquefaction storage Dewar 32 through a vacuum-jacketed cryogenic transfer line, and then to the first stage of the upper heat exchanger, and the gas gets cooled there. Then, it flows over the coil tube which is wound over the second-stage cylinder of the upper refrigeration portion, and the gas gets further cooled by absorbing refrigeration from the refrigerant. The coil tube is soldered over the second stage lower cylinder. The gas is subsequently cooled and liquid is produced at the condenser and stored in the upper liquefier 32b. The outer container 32a of upper liquefaction Dewar provides structural support to the inner Dewar 32b. Vacuum pump 33 provided vacuum insulation to upper liquefaction Dewar 32, which further contains an outer container 32a and an inner container 32b. The upper liquefier further contains, a plate 40 (preferably insulating material like G-10) to restrict the flow of liquid from the upper liquefier. A radiation shield 41 is also attached with upper liquefaction Dewar. The upper and lower liquefaction Dewar are attached with connecting flanges and couplings (i.e., structural supports 44 and 45) to retain it in its position at an angle rather than pure vertical orientations. The cooling liquid from the upper liquefaction Dewar is transferred into the external storage Dewar through a vacuum-jacketed transfer line 42, which also contains a vacuum-jacketed valve 43 to adjust the flow rate of liquid cryogen. The bulk liquid storage Dewar / external Dewar 25 consists of two containers like precooler and liquefaction Dewar, such as an outer container 25a and an inner container 25b. The interspace between the inner Dewar and outer Dewar is filled with an insulating material and vacuum insulation (provided by vacuum pump 31). Intermediate spacers are provided in between the inner container and outer container in all Dewar’s, such as: precooling Dewar, upper and lower liquefaction Dewar and external storage Dewar with materials like Hylam and are not shown in any figure. The inner Dewar will store the cryogenic fluid, and the outer Dewar will provide support to the inner container. A radiation shield 27 is attached inside the inner container to reduce the radiation heat loss. The Dewar also contains a level sensor, and temperature sensors to measure the liquid level and temperature of the fluid. A pressure gauge is also attached to detect the pressure of the container. Additionally, all the Dewar’s contains basic safety constraints like a relief valve, burst disc, vent valve, etc., and this is known to cryogenic engineers skilled in this field. This inner container 25b stores the liquid cryogens from both upper and lower liquefaction Dewar’s and transfers them to external useable Dewar’s via the transfer line 26 and regulating valve 28.

Figure 3 shows another embodiment of the proposed liquefier. This is basically similar to the device mentioned in Figure 2; the only difference is the location of the radiation shield. Here, the radiation shield 22 and 41 in the liquefaction Dewar is attached at the first stage heat exchangers in both the upper and lower liquefaction Dewars. It is noted that the radiation shield can be attached at any location, may be at the neck of the Dewar, at the first-stage cold heat exchanger, or at the second-stage cold heat exchanger, etc. At the upper neck portion of the inner container, radiation shields are also provided to reduce the radiation heat load.

Figure 4 shows another embodiment of the proposed liquefier. Here, the coil tube which is wound over the first-stage heat exchanger, second-stage heat exchanger, and second-stage cylinder as illustrated in Figure 2 is replaced by a series of fins. The fins are attached to the outer surface of the second-stage cylinder and heat transfer occurs from the gas chambers to the cooling fluid to reduce its temperature, and the fluid after cooling at the fins finally reaches the condensers which are attached to the second-stage cold heat exchanger of both lower and upper liquefier Dewar. Fins can also attached at the outer surface of first and second stage heat exchangers to enhance the rate of heat transfer and are not shown in this figure and other following figures of this type arrangement. The fluid gets cooled and the liquid gets collected inside the inner containers 12b and 32b of the liquefaction chamber. The process of supplying cryogenic gas to both upper and lower liquefaction Dewar is similar to that discussed in Fig. 2 and the process of removal of liquid cryogen from both lower and upper liquefier Dewar to the external storage Dewar is also similar to that discussed in Fig. 2.

Figure 5 shows another embodiment of the current liquefier, which is structurally similar to that of the device explained in Fig. 4. Here, the location of the radiation shield 22 and 41 used inside the upper and lower liquefaction Dewar i.e., 32b and 12b is different. In Fig. 4, the radiation shield is positioned at the upper flange of both upper and lower liquefaction Dewar, on the other hand, in Fig. 5 the radiation shield is attached at the first stage cold heat exchanger of both upper and lower liquefaction Dewar. It is also stated here that, the radiation shield can be placed at any location, i.e., at the upper flange, first-stage heat exchanger, second-stage heat exchanger etc. It is also possible to place a radiation shield at the outer surface of the inner container.

Figure 6 is similar to that of Figure 2, but here the two-stage twin cold finger GM cryocooler is replaced by a single-stage twin-cold finger GM cryocooler with a higher cooling capacity at the first stage cooling head. On the cooling head of the lower cold finger and upper cold finger, the lower heat pipe 46 and upper heat pipe 48 are attached to enhance the heat transfer area. Lower condenser 47 and upper condenser 49 heat exchangers are additionally filled with catalysts for hydrogen liquefaction. Thus, the gas can be cooled from the temperature of the first-stage heat exchanger to the liquefaction temperature of the cryogenic fluid. The cooling mechanism is similar to that of Figure 2; however, the cooling that occurs with the second stage cold heat exchanger is occurred by the heat pipe in this case. This method of liquefaction is helpful for neon/ hydrogen, but may not recommend for helium liquefaction due to poor refrigeration performance. Also, the single-stage twin cold finger GM cryocooler designed in this work is not capable of achieving the desired cooling capacity required for gas liquefaction at the first stage and the idea is only possible upon the development of high cooling capacity mechanical drive single-stage twin cold finger mechanical drive GM cryocooler.

Figure 7 is a novel system, in which the refrigeration unit of the lower cold finger 13 acts as a liquefier, whereas the refrigeration unit of upper cold-finger 34 acts like a recondensation unit. Cryogenic fluids like helium and hydrogen have lower boiling points. Thus, a small heat leak leads to the boil-off of these fluids. To avoid this boil-off, cryocoolers are provided in some cryogenic Dewars. The cryocooler will produce the necessary cooling power to recondense the evaporated cryogenic fluid (helium/ hydrogen). Here, the upper cold-finger acts like a recondenser unit, as it recondenses the evaporated liquid cryogen. The working mechanism of this novel system is explained as follows. The compressed gas (helium/ hydrogen) passes over a pressure reducing valve 2 to reduce its pressure, then it passes through a flow meter 3, valves (4, 5), and finally reaches the precooler 6. At the precooler, LN2 is supplied from an external source 8 to cool the gas from ambient temperature to room temperature. After cooling, it flows through an insulated cryogenic transfer line 9 to the lower liquefaction Dewar 12. The lower liquefaction Dewar contains two containers such as an inner container 12b and an outer container 12a. The gaps between both containers are filled with radiation shield to reduce radiation heat loss and vacuum insulation (by vacuum pump 30) is provided to reduce the convection loss. The Dewar contains an upper flange within which the lower refrigeration unit 13 of the cryocooler is located; the cooling part of the cryocooler is placed inside the Dewar, whereas the room temperature portion 19 of the cryocooler is placed outside the Dewar. The cooling fluid is further cooled by extracting the refrigeration effect produced by the lower cold finger 13 of the twin-cold finger GM cryocooler and then liquefied at the condenser 18 that is attached at the second stage 17 of the GM cryocooler. At the condenser 18, the gas gets cooled, and liquid droplets are produced and collected inside the inner container 12b of the Dewar. The liquid cryogen is transmitted from the liquefaction Dewar 12b to the bulk external liquid storage Dewar 25 via the vacuum-jacketed cryogenic transfer line 23. A radiation shield 22 is provided inside the lower liquefaction Dewar 12 to overcome the radiation heat loss. The storage Dewar 25 stores the liquefied cryogenic fluid. A special transfer line 50 is designed, via which the evaporated fluid is taken from the external storage Dewar 25 to the upper cryogenic Dewar 32, here this transfer line is coiled over the cold head of the second-stage heat exchanger 38, therefore the evaporated fluid gets liquefied, and this liquefied fluid is taken back again to the storage Dewar 25 by transfer line 51. The valve 43 may be a single valve or multiple valves (not shown here) to adjust the flow rate of gas through 50 and 51. All the transfer lines are well-insulated and arranged together in a compact fashion with further insulation. In this manner, the lower cold finger 13 acts like a liquefaction unit, and the generated cooling power is used for the liquefaction of the gas, and the upper cold finger 34 acts like a recondensation unit, which helps to reliquary the evaporated fluid.

Figure 8 illustrates a helium/ hydrogen/ neon liquefier without using a pre-cooler unit and using a coiled tube heat exchanger mechanism. From an energy balance calculation, it has been noticed that the precooling process has a small effect on the ultimate yield of this type of liquefaction plant. Therefore, it has been decided to remove the precooler from the liquefaction plant. Figure 8 shows a typical cryogen-free liquefaction system which does not contain precooler Dewar 6. Here, as the precooler is not present, the requirement of LN2 from an external source 8 is not required. The liquefaction system discussed in Fig. 6 is similar to that of Fig. 2 but it does not contain a precooler Dewar. The gas reaches directly at both the upper and lower liquefaction Dewar (32 and 12) from the supply cylinder 1 through 2, 3, 4 and 5. Thus, no need for a vacuum-jacketed cryogenic transfer line and the gas can be transferred by a bare cryogenic transfer line. The flow rate to the lower liquefaction Dewar 12 via cryogenic transfer line can be controlled by valve 10, and the flow rate to the upper liquefaction Dewar 32 by cryogenic transfer line can be controlled by valve 11. The valves 10 and 11 also not vacuum jacketed vales. After the gas is supplied to the lower transfer line, it gets cooled by passing it over the first-stage lower cylinder 14, then the first-stage lower cold heat exchanger 15, second-stage lower cylinder 16, and second-stage lower cold heat exchanger 17. The coil tubes are soldered over the first and second-stage cylinders of the cryocooler. While passing over the cylinder, the gas gets cooled by extracting heat from the refrigerant of the cryocooler, and then it passes to the condenser 18 that is attached to the second-stage heat exchanger. Here, the gas gets cooled; liquid droplets are produced and stored in the inner container 12b of the lower Dewar. The process of transfer of liquid cryogen from lower liquefaction Dewar 12b to the external Dewar 25 is similar to that of earlier models. The gas reaches the upper liquefaction Dewar 32, and it gets cooled after passing through the coil tube over the first-stage upper cylinder 35, first-stage upper heat exchanger 36, second-stage upper cylinder 37, and second-stage upper heat exchanger 38. Then, the gas gets liquefied over the upper condenser 39, and liquid cryogen gets collected in the upper liquefaction Dewar 32b. The liquid cryogen from the upper liquefaction Dewar 32 can be transferred to the external storage Dewar 25 in a similar fashion as discussed in earlier illustrations. It is necessary to state that the liquefaction rate of the cryogenic fluid in this liquefier is less than that of earlier, as a small quantity of cooling power is used to cool the gas from 300 K to the liquefaction temperature of nitrogen (77 K). On the other hand, this illustration does not depend on the supply of external cryogenic fluid like LN2, and thereby increases the reliability of the system.

Figure 9 shows another embodiment of a cryogen-free liquefaction system discussed in Fig. 8, but here fins are attached over the first and second-stage cylinders (14, 16, 35 and 37) to cool the gas in place of a soldered coil tube. Fins are also attached in first and second-stage heat exchangers but not shown in figures. Thus, the cooling efficiency of this proposed system depends upon the efficiency of the fin and the rate of effective cooling, cooling capacity of the cryocoolers. Here, radiation shields (41 and 22) in both the upper and lower liquefier Dewar (32 and 12) are attached at the upper flange of the Dewar, but it can be attached at any location like a first-stage heat exchanger (15 and 36), second-stage heat exchanger (17 and 39), etc.

Figure 10 shows another embodiment of a cryogen-free liquefaction system without using a top condenser and is similar to that discussed in Fig. 8. Here, the top condenser 39 has been removed, and the gas after cooling through the upper refrigeration unit 34 brings back to the lower liquefaction Dewar via cryogenic transfer line 42 and gets cooled at the bottom condenser 18, and liquid gets collected at the bottom liquefaction Dewar 12 and then transferred to the bulk fluid storage Dewar 25. Thus, this plant can be kept in a vertical orientation. However, the load on the bottom condenser will increase and hence this design will be different from earlier models.

Figure 11 shows another embodiment of the current invention of the proposed liquefier. This model is similar to that of the model illustrated in Figure 2, but here two precoolers are attached in place of a single precooler to accelerate the rate of pre-cooling. This will increase the complexity and requirement of LN2. The gas from cylinder 1 passes through the pressure-reducing valve 2, flow meter 3, needle valve 4, and cut-off valve 5. Then it splitted into two parts, one part passes to precooler Dewar 53, and the gas after precooling from ambient condition to 77 K, passes to the upper liquefaction Dewar 32 through vacuum jacketed cryogenic transfer line, and its flow rate can be controlled by regulating valve 11. The precooled gas is then cooled through the cooling effect produced by the upper refrigeration unit 34 of the twin cold finger mechanically driven GM cryocooler. After cooling, the gas is liquefied over the upper condenser 39 and liquid cryogen is collected in the inner container of the upper liquefier 32b. The precooler Dewar 53 consists of two containers, such as an inner container 53b and an outer container 53a. The interspace between them is filled with MLI and vacuum insulation, which is provided by vacuum pump 54. The flow rate to this precooler can be controlled by valve 55. The coiled tube heat exchanger 52, which is present inside the precooling Dewar 53b, cools the gas by absorbing the cooling effect from LN2 supplied from external source 8. The remaining gas after cut-off valve 5 gets cooled in precooler Dewar 6, after precooling it passes to the lower liquefaction Dewar 12. In the lower liquefaction Dewar 12, the gas gets cooled by the refrigeration effect produced by the lower cold finger 13 of the twin cold finger mechanically driven GM cryocooler. After liquefaction, the liquid cryogen is stored in the lower liquefaction Dewar 12b, and then it is transferred to the external Dewar 25 via the vacuum jacketed transfer line as discussed in Fig. 2. The gas flow rate to precooler Dewar 6 has been controlled by regulating valve 56.

Figure 12 illustrates schematics of a helium/ hydrogen/ neon liquefier using a fin heat exchanger mechanism and two pre-cooler units. Figure 12 is another embodiment of the current invention, which is a modification of the liquefier discussed in Fig. 11. This configuration also contains two precooler Dewars (such as 53 and 6) one for the upper liquefaction Dewar (32) and another for the lower liquefaction Dewar (12). However, the method of extraction of refrigeration effects from both cold heads of twin cold finger GM cryocooler is different. Here, fins are attached over the cylinders of second-stage in lower and upper cold fingers (16 and 37) to extract the cooling from refrigeration gas to the cooling gas; on the other hand, a soldering coil tube arrangement has been made over the second-stage cylinders of lower and upper stages (16 and 37) of GM cryocooler to get the refrigeration effect from the refrigerating fluid as in Fig. 11.

Figure 13 is a liquefaction and recondensation unit similar to that discussed in Fig. 7. Only difference is the mode of a heat exchange between the cooling gas and refrigeration unit. The coil tube heat exchange mode between the gas and cryocooler in Figure 7 is replaced by a fin-type arrangement in Figure 13. In a clearer manner, fins are attached over the second-stage cylinder of the lower cold finger to extract the refrigeration effect, which helps to liquefy the cooling fluid. The remaining working process is similar to that explained in Figure 7. This plant can also be made cryogen free by removing the precooler and extracting the refrigeration at the first stage heat exchanger of cryocoolers.

Figure 14 shows another embodiment of the present invention for the liquefaction of cryogenic gas like neon, helium, and hydrogen. Here, the arrangement looks similar to that of the liquefier discussed in Fig. 2, but the precooler is a cryogen-free device (i.e., the precooler is another twin cold finger GM cryocooler). The liquid nitrogen Dewar and its accessories are replaced by a single-stage twin cold-finger GM cryocooler. However, this cryogen free precooler may be two different single-stage single cold finger GM cryocooler. This cryocooler consists of a lower cold finger 61, lower heat exchanger 62, room temperature portion 65, upper cold finger 63, and upper heat exchanger 64. Radiation shields 68 and 69 are attached at the lower and upper cold fingers of the single-stage twin cold finger mechanical drive GM cryocooler respectively. Vacuum pumps 58 and 60 provide the vacuum insulation to the lower and upper vacuum chambers respectively. Helium compressor 66 provides the compressed refrigerant to the cold head of the twin cold finger GM cryocooler, and is cooled by water chillier 67. The gas flow rate to the lower and upper chambers is controlled by valves 71 and 70 respectively. The gas after passing through valve 5 split into two parts, one portion is for the upper liquefaction Dewar and the other is for the lower liquefaction Dewar. The part of the gas for the lower liquefaction Dewar passes to the lower vacuum chamber 57, at which the gas gets cooled at the first-stage cold heat exchanger 62 of the lower twin cold finger GM cryocooler. After the cooling, the gas passes through the transfer line to the lower liquefaction Dewar 12, and here it gets cooled and liquefied in a similar process as discussed earlier. The liquid cryogen is then transmitted to the external cylinder 25 through an insulated cryogenic transfer line. Similarly, the other portion of the gas gets cooled first by absorbing the heat from the cold heat exchanger of the upper cold finger 64, and then it flows to the upper liquefaction Dewar 32. In the upper liquefaction Dewar 32, the gas gets cooled, liquefied, and stored in the inner container 32b of upper liquefaction Dewar 32. The liquid is then transmitted into the large fluid storage Dewar 25 in a similar process as discussed earlier.

Figure 15 shows the schematics of another embodiment of the liquefier plant shown in Figure 14, here fins are attached at the second stages of the twin cold finger GM cryocooler present in the liquefaction unit to extract the heat load and liquefy the gas. The remaining working process is similar to that discussed in Fig. 14.

Figure 16 shows the schematic of a complete robust, compact, and portable hydrogen liquefier. This unit uses an electrolyser 72 to produce the hydrogen and oxygen from water via electrolysis. After the electrolyser, moisture trap 73 and oxygen trap 74 are adopted to trap the moisture and oxygen respectively, therefore only hydrogen will be allowed to pass through the liquefaction unit. The liquefaction unit is based on the twin-cold finger mechanically driven GM cryocooler as discussed above. After the moisture trap and oxygen trap appropriate sensors are adopted to measure the moisture and oxygen concentration. If the concentration of oxygen and moisture is the above-desired limit, then an electronic control valve 2 will be closed. Therefore, hydrogen gas will not be allowed to flow to the main liquefaction system, and will be stored in a gas container 76, and its flow rate is further controlled by 75. The gas storage container 76 further contains safety valves, sensors, burst discs etc. Before the control valve 2, a hydrogen purity meter is placed to measure the purity of hydrogen that flows into the system and this will be shown to the operator via an electronic unit. A flow meter 3, needle valve 4, cut-off valve 5 are used to measure the flow rate, and adjust the flow of working fluid respectively, and then the hydrogen gas is allowed to split into two parts, one to the precooler 53 and other to 6 for upper and lower liquefaction Dewar respectively. The depressurization valve is an optional part of this equipment and may be used for some time and may not be used for some time. LN2 is supplied from an external source 8 to precool the gas from 300 K to 77 K. It may be noted that the normal hydrogen at room temperature is a combination of 75% orthohydrogen and 25% parahydrogen. If the temperature value increases above the room temperature, then this composition remains unchanged, and when the temperature drops, the parahydrogen becomes the most stable form. Therefore, while cooling the hydrogen gas, orthohydrogen gets converted into the parahydrogen form. This conversation is an exothermic reaction and releases heat. Unfortunately, the heat released during this conversion is greater than the latent heat of vaporization. Thus, the liberated heat leads to the boil-off of the liquid hydrogen. Therefore, catalysts are used during the conversion process, and the coiled heat exchanger 52 and 7 used inside the precoolers is filled with catalysts to reduce the rate of reaction. Some of the most used catalysts are metals such as tungsten, nickel, paramagnetic oxides like chromium or gadolinium oxides, etc. After 6, cooled hydrogen will transfer fluid to the lower liquefaction Dewar 12 and from precooler 53; it will be transferred to the upper liquefaction Dewar 32. In lower liquefaction Dewar 12, the gas will be further cooled in the first-stage heat exchanger 15, second-stage cylinder 16, and second-stage heat exchanger 17. The coil tube that carries hydrogen gas is also filled with the catalyst to reduce the rate of reaction. The hydrogen is then liquefied at the condenser 18 and the liquid hydrogen gets collected inside the inner container of the lower liquefaction Dewar 12b. The liquid hydrogen is then transported from the lower liquefaction Dewar 12 to the external storage Dewar 25 through the vacuum-jacketed cryogenic transfer line as discussed earlier. Similarly, the remaining part of the hydrogen gas comes out from precooled Dewar 53 and gets cooled by absorbing the refrigeration effect from the upper refrigeration system 34 of the twin cold-finger GM cryocooler at the upper liquefaction Dewar. The fluid gets cooled and liquefied at the upper condenser 39 and stored in the upper liquefaction Dewar 32b. After liquefaction, the fluid flows through the insulated cryogenic transfer line to the external storage Dewar 25. Both upper and lower liquefier Dewar does contain radiation shields to reduce radiation loss. The radiation shield may be used outside the inner containers or inside the inner containers. The liquid hydrogen is then stored in the external hydrogen storage Dewar 25, which is also a double-walled configuration and the interspace is filled with vacuum insulation and aluminized Mylar to reduce the convection and radiation heat loss respectively. It may be noted that an extra coaxial fluid chamber filled with liquid nitrogen may be placed outside inner container and inside the outer container to reduce the rate of boil-off of helium/ hydrogen. The liquid hydrogen can be transferred to the end user by another transfer line 26 and valve 28 as shown in Fig. 16. It may be noted that the cooling coil of both the upper and lower cold fingers may be replaced by fins in this configuration and the details are not discussed here. Also, any liquefaction and recondensation unit discussed above from Fig. 2 to Fig 15 can be used here to liquefy the hydrogen gas.

Figure 17 shows another embodiment of the current invention used to produce liquid hydrogen. Here precooling happens to the hydrogen gas by a single-stage twin cold finger mechanical drive GM cryocooler rather than precooling Dewars discussed in Fig. 16, and the remaining process is similar to that explained earlier. The hydrogen gas flow pipe should be filled with catalysts to slow the rate of reaction.
The invention reported earlier can be placed at a certain angle to avoid the flow of liquid in a vertically downward direction if the gas liquefies at the upper liquefaction Dewar.

Figure 18 illustrates an architectural model of a two-stage twin cold finger mechanically driven GM cryocooler. Figure 18 shows the Solidworks model of the typical twin cold finger mechanically driven two-stage GM cryocooler, and its detailed components.

Figure 19 illustrates an architectural model of a typical LN2-cooled precooler (safety valve, burst disc, and sensors are not shown in assembly drawings). Figure 19 shows the typical Solidworks model of the precooler Dewar (either 6 or 52, as both are similar in structural configuration), which consists of an outer container (6a), an inner container (6b), coiled heat exchanger (7) and upper flange (individual part is not shown in figure). The upper flange further contains appropriate passages for the supply of LN2, its evaporation line, gas supply line, and cooled gas withdrawal line, feed through for entrance of level sensors, temperature sensors, burst disc, relief valve, etc. Vacuum passages are also provided at the outer container. A coiled tube 7 is placed inside the inner Dewar through which the gas passes. It may be noted that the coiled tube is filled with a catalyst in case of the hydrogen liquefaction process.

Figure 20 illustrates an architectural model of a typical single-stage twin cold finger-driven mechanical drive GM cryocooler as a cryogen-free precooler. Figure 20 shows the Solidworks model of a typical cryogen-free precooler that uses a single-stage twin cold finger mechanical drive GM cryocooler, and its components. Here, 57 is the lower vacuum chamber, 59 is the upper vacuum chamber and 65 indicate the room temperature portion of the cryocooler.

Figure 21 illustrates an architectural model of a typical liquefaction unit/cold box (compressor and water chiller are not shown). Figure 21 shows the typical liquefaction unit/ cold box of the liquefier, and this is the heart of the liquefaction unit. The sole performance/ yield rate depends on the efficiency of this unit.

Figure 22 illustrates an architectural model of some essential parts of the cold box. Outer container, inner container, two-stage twin cold finger driven mechanical drive GM cryocooler with condensers at both cold fingers. Figure 22 shows a typical outer container 12a/32a, the inner container 12b/32b, and twin cold finger mechanical drive GM cryocooler and its components of the liquefaction unit/cold box. In a coiled tube arrangement, a coiled tube can be coiled over cylinders to extract the refrigeration effect and fin heat exchanger; fins can be connected to extract the refrigeration effect.

Figure 23 illustrates an architectural model of some typical condensers used in second-stage heat exchangers of twin cold finger mechanical drive GM cryocoolers. The different condensers are used at the second stage of the GM cryocooler.

Figure 24 illustrates an architectural model of the liquefaction and recondensation unit of the liquefaction plant; here the upper liquefaction Dewar contains a simple vacuum chamber 32 and radiation shield with several layers of MLI. A special heat exchanger is designed for the upper second-stage heat exchanger to cool the evaporated gas back to its liquid state. Figure 25 illustrates the architectural model of a typical external liquid storage Dewar and its components. The external storage Dewar 25 consists of an outer container (consisting of three parts), an inner container 25b. An intermediate flange may/may not be kept in between the lower and upper flange. The outer container contains handles and flanges for vacuum and other spaces; whereas, the inner container contains radiation shields and appropriate connections for the fill/drain line, evacuation line, rupture disc, relief valve, pressure gauge, and level sensor/temperature sensor connection pipes. The upper neck portion of the inner container contains special bellows.

The liquefier that is capable of liquefying helium/ hydrogen/ neon gas consists of a gas supply unit 102 that supplies pure gas either from a pure gas cylinder or from a gas production and purification unit (102B) (e.g. electrolyzer and moisture and oxygen trap for pure hydrogen gas).
The precooling unit (104) to cool the gas from ambient conditions to the liquid nitrogen temperature using LN2 as precooling fluid (104A). The precooling happens either by adopting a single-stage twin cold finger mechanical drive GM cryocooler (which is a cryogen-free device) or by adopting a precooler Dewar. The precooler Dewar further contains two containers, an outer container, and an inner container. The annular gap between them is filled with several layers of MLI and vacuum insulation to reduce the convection and radiation heat load. The outer Dewar is made up of SS304 and provides support to the inner container. The inner Dewar contains the precooling fluid (104A), preferably LN2. Spacers are provided in between the outer and inner container to provide the necessary structural support and are normally poor thermal conducting materials like Hylam/FRP. A coiled tube heat exchanger is placed inside the inner container, within which the gas passes and gets cooled. An intermediate flange may be used to reduce heat loss by conduction, and the intermediate flange is made up of low thermal conductivity materials like G-10. The upper flange further contain passages for the supply of LN2 to the inner container and a passage for the removal of evaporated LN2, two passages for the inlet and outlet of gas to and from the precooler Dewar, feed through for sensors, burst discs, safety valves, etc. In the case of hydrogen liquefaction, the heat exchanger needs to be filled with a catalyst to reduce the rate of energy liberation due to exothermic reaction because of ortho-para conversion of hydrogen. This is an additional requirement for hydrogen liquefaction plant.
The liquefaction unit, which contains a lower liquefaction Dewar, a upper liquefaction Dewar, a twin cold finger mechanically driven GM cryocooler, a helium compressor, and a water chillier. The lower liquefaction Dewar contains two containers, such as: an outer container, and an inner container, the interspace between them are filled with MLI and vacuum insulation to reduce the radiation heat loads. Similarly, the upper liquefaction Dewar contains two containers, such as: an outer container, and an inner container, the interspace between them are filled with MLI and vacuum insulation. The twin cold finger GM cryocooler contains a first-stage displacer housing, first-stage regenerator, first-stage heat exchanger, second-stage displacer housing, second-stage regenerator, second-stage heat exchanger, associated gas spaces, and related drive mechanisms. A supplementary heat exchanger is also adopted at the first stage heat exchangers of both lower and upper cold fingers to enhance the heat transfer area, and two condensers are attached at the second stage heat exchangers of both upper and lower cold fingers to condense the gas and produce the liquid. Different arrangements (e.g., coiled tube and fins) have been made to efficiently transfer the refrigeration effect from the cryocooler to the gas to enhance the cooling rate. This unit liquefies the gas.
The series of bare cryogenic transfer lines, insulated and vacuum-insulated cryogenic transfer lines can be used to transfer the gas from one unit to another unit of the liquefaction system. A bare transfer line is used to transfer the gas from the supply unit to the precooler unit. Insulated cryogenic transfer lines are used to transfer the liquid between precooler Dewar to liquefaction Dewars, and liquefaction Dewars to bulk liquid storage Dewar.
The number of safety valves, burst discs, relief valves, regulatory valves, V-J regulatory valves, level sensors, temperature sensors, needle valves, pressure sensors, flow meters, and depressurization valves have been used at different locations of the liquefaction system.
The external bulk liquid storage unit (108) that stores the liquid product (i.e., helium /hydrogen /neon) after its liquefaction. This also contains two containers, such as an outer container and an inner container. The interspace between them is filled with MLI and vacuum insulation to reduce the convective and radiative heat load. This unit stores the liquid cryogen and is delivered to the end user upon requirement.

The liquefier can also be modified to be used as a cryogen-free system. This can be made by removing the precooler Dewar; this eliminates the requirement of LN2. The precooling and liquefaction happen at both upper and lower liquefaction Dewars by absorbing the refrigeration capacities of both upper and lower cold fingers of twin cold finger mechanically driven GM cryocooler at the respective first-stage heat exchangers. As certain cooling capacities of the cryocooler will be utilized for the precooling, its cooling performance will be lower compared to the previous liquefaction plant. However, the theoretical simulation shows that its effect will be minimum.
The liquefier can further be modified to use two precooling Dewars. Both precooling Dewar are similar in structural configuration. One precooling Dewar will be used to cool the gas for the lower liquefaction Dewar and another precooling Dewar will be used for the cooling of gas for the upper liquefaction Dewar. This will enhance the complexity of the system but does not create significant enhancement in the cooling rate of the overall system as evident from theoretical simulation.
The liquefier can be further modified by replacing the two-stage twin cold finger GM cryocooler of the liquefaction unit with a single-stage twin cold finger high-capacity mechanically driven GM cryocooler. Heat pipes and heat exchangers can be attached at the cold heat exchangers of both upper and lower cold fingers to enhance the rate of heat transfer and this unit will not be able to produce liquid helium. But, this can produce liquid neon and liquid hydrogen based on the cooling capacity of the cryocoolers.
The liquefier can be further modified by replacing the LN2 precooled precooling Dewar with another single-stage twin cold finger mechanically driven GM cryocooler and vacuum chambers for both lower and upper cold finger units. Here, the gas will be pre-cooled by absorbing the refrigeration capacity of the first stage lower cold finger and first stage upper cold finger for lower liquefaction Dewar and upper liquefaction Dewar respectively.
The liquefier can be further modified by replacing the second-stage condenser of upper liquefaction Dewar. Thus, the gas can be cooled in the upper cold finger of the twin cold finger of the mechanically driven GM cryocooler, and after cooling it will be supplied to the lower liquefaction Dewar for liquefaction in the lower condenser. Thus, the plant can be oriented in the vertical direction; however, it will increase the load on the bottom condenser.
The liquefier can further be modified as a liquefaction-recondensation unit. Here, the lower cold finger will act as a liquefier to liquefy the gas, and the upper cold finger will act as a recondenser to recondense the evaporated liquid from the bulk liquid storage container and convert it to liquid and resend it to the external storage Dewar. This will be able to minimize the boil-off loss of the external bulk storage container and helps to keep the model in a vertical orientation.
The liquefier further contains valves in the supply lines, through which the liquefaction rates of lower and upper liquefaction Dewar can be controlled by adjusting the opening and closing of regulating valves.
A robust portable hydrogen liquefaction plant produces a small quantity of liquid hydrogen from water using both an electrolyzer and a liquefaction unit. This proposed machine uses both inbuilt pure hydrogen gas production and liquefaction units. The hydrogen gas production unit consists of an on-board electrolyzer that produces hydrogen and oxygen from water via/by electrolysis. The oxygen that is produced from the electrolysis gets trapped by an oxygen trap and eliminates/removes from the system. A moisture trap is also provided to trap the moisture which is produced from electrolysis. Moisture concentration and oxygen concentration measuring sensors are adopted to measure the moisture and oxygen level. A hydrogen purity meter is kept to detect the purity level of hydrogen and if it is found within the required purity level, then hydrogen is allowed to pass through the liquefaction unit, otherwise, it will be stored in the gas storage space. The liquefaction unit is any one of the liquefaction arrangements as described above, however only two has been presented. The liquefaction unit consists of a precooler unit, a liquefaction unit, and a bulk liquid storage unit. The pre-cooling unit can also be removed from the system to make it a cryogen-free portable hydrogen liquefier. In the absence of precooling Dewar, gas will get precooled at the first stage of the cylinder and first-stage heat exchanger by absorbing certain refrigeration capacity. However, this will create a certain adverse effect on the liquefaction rate by reducing its performance. The pre-cooling unit consists of an inner container, an outer container, a coiled tube for gas passages, an upper flange, an intermediate flange, measuring sensors, and safety equipment. The liquefaction unit consists of a two-stage twin cold finger mechanically driven GM cryocooler, a helium compressor, a water chillier, a lower liquefaction Dewar, and a upper liquefaction Dewar. Lower and upper liquefaction Dewars contains an inner container, an outer container, adequate gas flow passages, safety valves, vacuum ports, etc. The liquid hydrogen from both the upper and lower liquefaction Dewar will be transported to an external bulk hydrogen storage Dewar and stored for end users. The external bulk hydrogen storage Dewar also consists of an outer Dewar and an inner Dewar, and the interspace among them is filled with vacuum insulation and MLI to reduce external heat leakage by convection and radiation. Appropriate cryogenic transfer lines and a series of different regulating valves, needle valves, safety valves, etc. are provided at different locations of the plant to regulate the flow rate, safety measures, monitor the gas flow rates, etc.
The hydrogen liquefaction plant discussed is converted into hydrogen liquefaction and recondensation unit by replacing the liquefaction unit as discussed in 7. Here, the lower cold finger will liquefy the gas and the upper cold finger will recondense the evaporated hydrogen to liquid hydrogen.
The liquefaction unit of the hydrogen plant can be replaced by the liquefaction unit to make it cryogen-free, reliable operation, etc.
The objectives of this invention includes the:
• Concept of small-scale liquid helium, liquid hydrogen, and liquid neon cryogenic plant using twin cold finger mechanical drive GM cryocooler.
• Concept of a small-scale twin cold finger mechanical drive GM cryocooler-based helium/ hydrogen/ neon liquefaction and recondensation unit.
• Conceptualization of a compact, portable liquid hydrogen generator using an onboard hydrogen gas production unit from water by electrolyzer, purifier and then liquefaction of the gas by using a twin cold-finger mechanical drive GM cryocooler-based hydrogen gas liquefier.
• Design of an LN2 cooled precooler for precooling of helium/ hydrogen and neon gas from room temperature to the boiling point of nitrogen.
• Design of a liquefaction unit/ cold box for liquefaction of helium/ hydrogen/ neon gas.
• Design of a bulk liquid helium/ hydrogen/ neon storage Dewar to minimize the boil-off rate of the fluid.

This invention reports the development procedures of twin cold finger-based helium, hydrogen, and neon liquefiers. The liquid helium, liquid hydrogen, and liquid neon have a wide variety of industrial and laboratory applications.
• Liquid helium is an essential cooling medium for several low-temperature applications including superfluid helium droplet spectroscopy, superconducting quantum interference devices, particle accelerators, construction of high-accuracy gyroscopes, etc.
• Liquid helium is also used in major laboratory-based applications such as: cooling of low Tc superconducting magnets, MRI, Nuclear magnetic resonance (NMR), superconducting quantum infrared detectors (SQUIDs), infrared sensors, etc.
• Liquid helium is also used in low-temperature physics research, cryogenics research, space applications, military applications, and medical science activities, especially in MRI, fiber optics, space exploration, military rockets, etc.
• Liquid helium is used in cooling of both low-temperature superconducting magnets to retain their superconducting states.
• Liquid helium is used in calibration of cryogenic temperature sensors.
• Liquid hydrogen is also used as a fuel in cryogenic rocket engines.
• Liquid hydrogen is used as a green fuel for spacecraft, cars, buses, trucks, trains, etc.
• Liquid neon is used in laboratory and industrial applications such as aerospace, space crafts and automotive, etc.
• Refrigerant for testing of material properties in cryogenic temperature limits.
• An onboard portable robust novel liquid hydrogen generator has been designed, which can be used to produce liquid hydrogen from water directly and store it for practical applications. This liquid hydrogen generator can be easily transported from one place to another by lorry. This can be used in trains to produce liquid hydrogen from water directly and power its fuel cells using liquid hydrogen. This can be used to produce liquid hydrogen from water and this liquid hydrogen can be used as a fuel for UAVs for Ariel military applications in border area.

The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

Benefits, other advantages, and solutions to problems have been described above about specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims. ,CLAIMS:1. An apparatus for liquefaction of helium/hydrogen/neon using a twin cold finger mechanical drive GM cryocooler, said apparatus comprises:
a. a gas supply unit (102) configured to supply pure gas from a high-pressure storage cylinder (102A) or a gas production and purification unit (102B) selected from a group consisting of an electrolyzer and moisture and oxygen trap for pure hydrogen gas;
b. a precooling unit (104) connected with said gas supply unit (102) and operable to cool received gas from ambient conditions to a liquid nitrogen temperature using liquid nitrogen (LN2) as a precooling fluid (externally supplied cryogenic fluid) (104A), said precooling unit (104) comprising:
i. a single-stage twin cold finger mechanical drive Gifford-McMahon (GM) cryocooler (104B), or
ii. a precooler Dewar comprising an outer container and an inner container with an annular gap filled with multilayer insulation (MLI) and vacuum insulation, said inner container holding LN2 and a coiled tube heat exchanger for gas cooling;
iii. a plurality of spacers provided in between said outer and inner container to provide a structural support and normally poor thermal conducting materials preferably Hylam/FRP;
iv. a coiled tube heat exchanger placed inside said inner container, within which said gas passes and gets cooled;
v. an intermediate flange reduces heat loss by conduction, said flange further contains passages for said supply of LN2 to said inner container and a passage for removal of evaporated LN2, two passages for said inlet and outlet of gas to and from said precooler Dewar, feed through for sensors, burst discs, and safety valves;
wherein in case of hydrogen liquefaction, said heat exchanger needs to be filled with a catalyst to reduce a rate of energy liberation due to exothermic reaction because of ortho-para conversion of hydrogen;
c. a liquefaction unit (106) comprising:
i. an upper and lower liquefaction Dewar, each having an outer container and an inner container with interspaces filled with MLI and vacuum insulation to reduce radiation heat loads;
ii. a twin cold finger mechanically driven GM cryocooler (104B) contains a first-stage displacer housing, first-stage regenerator, first-stage heat exchanger, second-stage displacer housing, second-stage regenerator, second-stage heat exchanger, associated gas spaces, and related drive mechanisms;
iii. a supplementary heat exchanger adopted at said first stage heat exchangers of both lower and upper cold fingers to enhance heat transfer area, and two condensers are attached at said second stage heat exchangers of both upper and lower cold fingers to condense gas and produce said liquid;
iv. a helium compressor, and a water chillier;
wherein different arrangements selected from coiled tubes and fins have been made to efficiently transfer said refrigeration effect from said cryocooler (104B) to said gas to enhance a cooling rate;
d. a series of transfer lines, comprising bare, insulated, and vacuum-insulated lines, to transfer gas between units of said liquefaction unit (106), wherein said bare transfer line is used to transfer said gas from said supply unit to said precooler unit, said insulated cryogenic transfer lines are used to transfer said liquid between precooler Dewar to liquefaction Dewars, and liquefaction Dewars to bulk liquid storage Dewar;
e. a plurality of safety and regulatory components selected from a number of safety valves, burst discs, relief valves, regulatory valves, V-J regulatory valves, level sensors, temperature sensors, needle valves, pressure sensors, flow meters, and depressurization valves at different locations; and
f. an external bulk liquid storage unit (108) that stores said liquid product including helium, hydrogen, and neon after liquefaction, wherein said external bulk liquid storage unit (108) contains two containers, such as an outer container and an inner container, wherein an interspace between said outer and inner container is filled with MLI and vacuum insulation to reduce a convective and radiative heat load, wherein said external bulk liquid storage unit (108) stores liquid cryogen and is delivered to an end user upon requirement.

2. The apparatus as claimed in claim 1, wherein said precooler Dewar is removed to configure said apparatus as a cryogen-free system, thereby eliminating usage of LN2, wherein said precooling and liquefaction processes are performed in both upper and lower liquefaction Dewars by utilizing refrigeration capacities from said upper and lower cold fingers of a twin cold finger mechanically driven GM cryocooler (104B), specifically at first-stage heat exchangers, wherein a portion of said cryocooler's cooling capacity is allocated for a precooling process, resulting in a reduction in overall cooling performance, wherein any reduction in cooling performance due to allocation of a cryocooler's cooling capacity for precooling is substantively offset, as evidenced by theoretical simulations indicating minimal adverse effect.

3. The apparatus as claimed in claim 1, wherein further modified to comprise two precooling Dewars, each having a similar structural configuration, wherein one of said precooling Dewars is dedicated to cooling gas for said lower liquefaction Dewar, and another precooling Dewar is dedicated to cooling gas for an upper liquefaction Dewar, wherein incorporation of two precooling Dewars results in an increased system complexity, wherein a modification leading to said increased complexity does not significantly enhance a cooling rate.

4. The apparatus as claimed in claim 1, wherein said two-stage twin cold finger GM cryocooler (104B) of said liquefaction unit (106) is replaced by a single-stage twin cold finger high-capacity mechanically driven GM cryocooler (104B), wherein heat pipes and heat exchangers attached to cold heat exchangers of both upper and lower cold fingers, said configuration being adapted to enhance a rate of heat transfer, wherein a modified apparatus is not configured to produce liquid helium, wherein said apparatus is capable of producing liquid neon and liquid hydrogen, said production being contingent upon a cooling capacity of said cryocoolers.

5. The apparatus as claimed in claim 1, wherein said LN2 precooled precooling Dewar is replaced by a single-stage twin cold finger mechanically driven GM cryocooler (104B), wherein said precooling Dewar further comprising vacuum chambers associated with both said lower and upper cold finger units, wherein gas pre-cooling occurs through absorption of a refrigeration capacity from:
i. said first stage of said lower cold finger for said lower liquefaction Dewar, and
ii. said first stage of said upper cold finger for said upper liquefaction Dewar.

6. The apparatus as claimed in claim 1, wherein said second-stage condenser of said upper liquefaction Dewar is replaced, facilitating cooling of said gas in said upper cold finger of said twin cold finger mechanically driven GM cryocooler (104B), wherein, post-cooling in said upper cold finger, said gas is supplied to said lower liquefaction Dewar for subsequent liquefaction within said lower condenser, wherein a configuration permits a vertical orientation of said plant, wherein vertical orientation results in an increased load on a bottom condenser.

7. The apparatus as claimed in claim 1, wherein further configured as a liquefaction-recondensation unit, wherein said lower cold finger functions as a liquefier to convert said gas to a liquid state, and said upper cold finger operates as a condenser, designed to recondense evaporated liquid originating from said bulk liquid storage container, converting it back to liquid form and directing it to an external storage Dewar, such a configuration being conducive to minimizing boil-off loss from an external bulk storage container and allowing for a vertical orientation of said apparatus.

8. The apparatus as claimed in claim 1, further comprises valves positioned within supply lines, wherein liquefaction rates of both said lower and upper liquefaction Dewars are adjustable through a modulation of said regulating valves.

9. The apparatus as claimed in claim 9, further comprises a portable hydrogen liquefaction plant system, adapted to derive a specific quantity of liquid hydrogen from water comprises:

a. an on-board electrolyzer configured to electrolytically dissociate water, producing hydrogen and oxygen;
b. an oxygen trap functionally designed to capture said produced oxygen and remove it from said system;
c. a moisture trap to sequester moisture resulting from a electrolysis process;
d. sensors to determine moisture and oxygen concentrations, providing feedback on system status;
e. a hydrogen purity meter to detect a purity of said produced hydrogen, wherein if purity meets a user-defined criteria, said hydrogen is directed to said liquefaction unit (106), otherwise, it's stored in a designated gas storage space; and
wherein said liquefaction unit (106), which may be in line with previously described liquefaction configurations, comprising:
i. a precooler unit, which may optionally be excluded for a cryogen-free configuration, further consisting of an inner container, an outer container, a coiled tube for gas flow, an upper flange, an intermediate flange, measurement sensors, and safety mechanisms;
ii. a primary liquefaction system, inclusive of a two-stage twin cold finger mechanically driven GM cryocooler (104B), a helium compressor, a water chiller, and both lower and upper liquefaction Dewars, each Dewar consisting of an inner and outer container, gas flow pathways, safety valves, and vacuum ports;
iii. an external bulk hydrogen storage Dewar, equipped with outer and inner containers separated by a space filled with vacuum insulation and MLI to minimize external heat leakage, configured to store said liquefied hydrogen for subsequent use; and
wherein cryogenic transfer lines and a series of different regulating valves, needle valves, and safety valves are provided at different locations of said plant to regulate a flow rate, safety measures, and monitor said gas flow rates.

10. The apparatus as claimed in claim 9, wherein said system is converted into hydrogen liquefaction and recondensation unit by replacing said liquefaction unit (106), wherein said lower cold finger liquefies said gas and said upper cold finger recondenses evaporated hydrogen to liquid hydrogen, wherein said liquefaction unit (106) of said hydrogen plant replaced by said liquefaction unit (106) to make it cryogen-free, and reliable operation.