TECHNICAL FIELD
Embodiments of the present invention relate generally to refrigerators and more specifically to refrigerators working in dual mode using Alternating Current (AC) power in a first mode and Direct Current (DC) power in a second mode.
BACKGROUND ART
Refrigerators generally are power intensive appliances and hence are designed for operating under a constant supply of Alternating Current (AC). However, constant supply of AC power is still a challenge in a number of developing and under-developed economies. The problem is aggravated as the focus is shifted from urban areas to rural areas, where the AC power supply is at best intermittent. This poses a significant challenge to applicability of the refrigerator and therefore undermines any reason to make an investment into one. The reason being that in most of their applications, and especially in rural areas, the refrigerators are used to preserve perishable food items and in absence of uninterrupted cooling, the food items are liable to perish anyways. In case of visi coolers, that are generally used to store beverages supposed to be served chilled (within a desired temperature range), lack of sufficient cooling or absence of cooling hampers the marketability of the beverages that are stored in the visi coolers.
Therefore, in light of the discussion above, there is need for a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator, which does not suffer from above mentioned deficiencies.
OBJECT OF THE INVENTION
An aspect of the present invention provides a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator.
Another aspect of the present invention provides a control module for a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator.
SUMMARY OF THE INVENTION
Embodiments of the present invention aim to provide a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator. the hybrid refrigerator is still able to perform its intended function during power cut-off or grid failure, which is a major bonus for developing countries and rural areas where power cut-off and grid failures are a common phenomenon. The invention is simple in construction and does not demand any major design overhaul for implementation, thus providing several cost benefits including ability for upgrading existing refrigeration setups. Since the conduits carrying the refrigerant need not come in contact with the PCM, there is minimal issue of surface corrosion. Also, a wide range of PCMs may be used to achieve different levels of refrigeration (or to meet a wide range of cooling requirements) for different applications, without making any changes in the design of the setup.
According to a first aspect of the present invention, there is provided a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator including a compressor, a condenser, a throttling device, an evaporator and conduits carrying a refrigerant, the hybrid refrigerator comprising an auxiliary heat exchanger including a Phase Change Material (PCM), the auxiliary heat exchanger being configured to transfer heat to the refrigerant during an AC operated mode and receive heat from a refrigerated space during a DC operated mode, a rechargeable battery configured to be receive and store electrical power during the AC operated mode and deliver the stored electrical power during the DC operated mode, an auxiliary fan configured to be powered from the rechargeable battery during the DC operated mode in order to augment the transfer of heat from the refrigerated space to the auxiliary heat exchanger and a control module configured to switch the hybrid refrigerator between the AC operated mode and the DC operated mode.
In one embodiment of the invention, the refrigerated space includes a first temperature sensor configured to sense a first temperature value in the refrigerated space and a circulation fan configured to be cut-off in response to the first temperature value being smaller than a first temperature threshold.
In one embodiment of the invention, the refrigerated space comprises a refrigeration compartment and a freezer compartment, the freezer compartment including a circulation fan, wherein the freezer compartment includes a first temperature sensor configured to sense a first temperature value in the freezer compartment and the circulation fan is configured to be cut-off in response to the first temperature value being smaller than a first temperature threshold.
In one embodiment of the invention, the hybrid refrigerator further comprises a second temperature sensor provided along the conduits, downstream of the auxiliary heat exchanger and configured to sense a second temperature value of the refrigerant and the compressor is configured to be cut-off in response to the second temperature value being smaller than a second temperature threshold.
In one embodiment of the invention, the auxiliary heat exchanger includes one or more storage tanks sandwiched between two plates of two respective plate and tube heat exchangers, the one or more storage tanks being adapted to store the PCM.
In one embodiment of the invention, the one or more storage tanks include grooves on respective outer surfaces of the one or more storage tanks, in order to accommodate tubes of the two plate and tube heat exchangers.
In one embodiment of the invention, the control module includes a micro-controller configured to regulate current being supplied to the rechargeable battery, during the AC operated mode, connect the rechargeable battery with the auxiliary fan in response to a supply voltage, of an AC supply line delivering AC power to the hybrid refrigerator, being smaller than a first supply threshold and a battery voltage, across terminals of the rechargeable battery, being greater than a second battery threshold, during the DC operated mode and disconnect the rechargeable battery from the auxiliary fan in response to the battery voltage being smaller than a third battery threshold, during the DC operated mode, in order to prevent the rechargeable battery from deep discharge.
In one embodiment of the invention, the hybrid refrigerator further includes a secondary illumination source, wherein the control module is configured to illuminate the refrigerated space through the secondary illumination source, during the DC operated mode.
According to a second aspect of the present invention, there is provided a control module for a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator including a compressor, a condenser, a throttling device, an evaporator and conduits carrying a refrigerant, the control module comprising a micro-controller configured to regulate current being supplied to the rechargeable battery, during the AC operated mode, connect the rechargeable battery with the auxiliary fan in response to a supply voltage, of an AC supply line delivering AC power to the hybrid refrigerator, being smaller than a first supply threshold and a battery voltage, across terminals of the rechargeable battery, being greater than a second battery threshold, during the DC operated mode and disconnect the rechargeable battery from the auxiliary fan in response to the battery voltage being smaller than a third battery threshold, during the DC operated mode, in order to prevent the rechargeable battery from deep discharge.
In one embodiment of the invention, the micro-controller is further configured to is configured to illuminate the refrigerated space through a secondary illumination source, during the DC operated mode.
In the context of the specification, a “Phase Change Material (PCM)” includes any pure substance, or a mixture or a solution capable of undergoing phase transformation between solid and liquid phases, preferably within a predetermined temperature range, thereby releasing heat during solidification and absorbing heat during fusion. They may include water, organic liquids (such as fatty acids), organic solids (such as paraffins), hydrated salts, and eutectic solutions.
In the context of the specification, a “micro-controller” includes any general purpose processor, microprocessors, Field Programmable Gate Arrays (FPGAs) and Application Specific Integrated Circuits (ASICs) and may be based on several different architectures known in the art or may be developed in the foreseeable future.
In the context of the specification, a “polymer material” is any naturally occurring or man-made material having long chains of organic molecules (8 or more organic molecules), with physical and chemical properties of such organic molecules giving the material its desired properties.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may have been referred by embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
These and other features, benefits, and advantages of the present invention will become apparent by reference to the following text figure, with like reference numbers referring to like structures across the views, wherein:
Fig. 1 illustrates a logical diagram of a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator, in accordance with an embodiment of the present invention;
Fig. 2A illustrates an exploded view of the hybrid refrigerator, in accordance with an embodiment of the present invention;
Fig. 2B illustrates a rear perspective view of the hybrid refrigerator, in accordance with an embodiment of the present invention;
Fig. 2C illustrates a logical diagram of a control module, in accordance with an embodiment of the present invention;
Fig. 3 illustrates a logical diagram of a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator, in accordance with another embodiment of the present invention; and
Fig. 4 illustrates an exploded view of the hybrid refrigerator, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
While the present invention is described herein by way of example using embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments of drawing or drawings described, and are not intended to represent the scale of the various components. Further, some components that may form a part of the invention may not be illustrated in certain figures, for ease of illustration, and such omissions do not limit the embodiments outlined in any way. It should be understood that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the present invention as defined by the appended claim. As used throughout this description, the word "may" is used in a permissive sense (i.e. meaning having the potential to), rather than the mandatory sense, (i.e. meaning must). Further, the words "a" or "an" mean "at least one” and the word “plurality” means “one or more” unless otherwise mentioned. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes. Any discussion of documents, acts, materials, devices, articles and the like is included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention.
In this disclosure, whenever a composition or an element or a group of elements is preceded with the transitional phrase “comprising”, it is understood that we also contemplate the same composition, element or group of elements with transitional phrases “consisting of”, “consisting”, “selected from the group of consisting of, “including”, or “is” preceding the recitation of the composition, element or group of elements and vice versa.
The present invention is described hereinafter by various embodiments with reference to the accompanying drawing, wherein reference numerals used in the accompanying drawing correspond to the like elements throughout the description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the following detailed description, numeric values and ranges are provided for various aspects of the implementations described. These values and ranges are to be treated as examples only, and are not intended to limit the scope of the claims. In addition, a number of materials are identified as suitable for various facets of the implementations. These materials are to be treated as exemplary, and are not intended to limit the scope of the invention.
A refrigerator, also colloquially known as a cooler, employs a vapour compression cycle for achieving refrigeration of stored items. Most common constructions of refrigerators involve a single door with a single compartment for refrigeration, a single door with two compartments, one being a refrigeration compartment and another being a freezer compartment (also known as an ice maker) and double doors with one door for each one of the freezer compartment and the refrigeration compartment. There is another commercially used construction known as a visi cooler, generally used to cool liquids to within a temperature range of 2-4°C. Visi coolers are also generally characterized by at least partially transparent front doors for display of items, such as soft-drinks and beverages, contained within the refrigerator cabinet.
All the constructions discussed above and many more commercially available constructions will generally deploy, among other things, a refrigerant being recirculated in conduits and connecting an evaporator, a compressor downstream of the evaporator, a condenser downstream of the compressor, a throttling device downstream of the condenser and the evaporator being downstream of the throttling device, thus forming a cycle. Commonly known refrigerants include, but are not limited to R32, R134a, R125, R245ca, R245fa, R290, R407C, R410A, R507A, R508B and R600 etc. The refrigerant is generally delivered to the evaporator in its liquid state where the refrigerant absorbs heat from the refrigerated space and vaporizes.
The vaporized refrigerant is delivered to the compressor, where the refrigerant undergoes polytropic compression and is delivered to the condenser at a high pressure. The high pressure and vaporized refrigerant loses heat to the atmosphere inside the condenser, causing the refrigerant to condense to a liquid state while still being at a relatively high pressure. The throttling device allows the refrigerant to undergo pressure drop without significant heat transfer taking place between the atmosphere and the liquid refrigerant. This low pressure refrigerant in liquid state is again delivered to the evaporator allowing the refrigerant to absorb further heat from the refrigerated space and maintain a predetermined temperature in the refrigerated space.
While the operation of the vapour compression cycle as discussed above has been known in the art for some time and there have been several incremental improvements to enhance the overall efficiency and efficacy of the cycle, the cycle is still largely dependent on work input provided by the compressor to keep the refrigerant in circulation. However, since in a normal household, the compressor can only be operated through AC electrical power, the vapour compression cycle becomes ineffective in absence of, or due to interrupted, supply of the AC electrical power. Therefore, it is envisaged that there may be provided an auxiliary heat exchanger in the refrigerated space. The auxiliary heat exchanger is envisaged to contain a Phase Change Material (PCM) that would release heat to the refrigerant during normal operation of the refrigerator when there is the AC power supply available and freeze to a solid state or at least undergo drop in temperature. When, the AC power supply is unavailable, and the compressor in unable to operate, the PCM will absorb heat from the refrigerated space and undergo fusion to produce cooling effect in the refrigerated space. The cooling of the refrigerated space may further be augmented through a DC operated auxiliary fan. Of course to operate the auxiliary fan, a rechargeable battery may also be provided, the rechargeable battery being charged when there is AC power supply available.
Referring to the drawings, the invention will now be described in more detail. Figure 1 illustrates a logical diagram of a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator 100 (hereinafter referred to as the hybrid refrigerator 100), in accordance with an embodiment of the present invention. As can be seen from Figure 1, the hybrid refrigerator 100 includes standard elements of a vapour compression cycle such as a compressor 102 which may be a positive displacement type or a centrifugal compressor. Other possible constructions of compressor 102 include hermetic and semi-hermetic compressors and may be of rotary, reciprocating or scroll types. A condenser 104 is provided downstream of the compressor 102, a condenser fan 136 to augment heat transfer from the refrigerant to the ambient, a throttling device 106 downstream of the condenser 104 and an evaporator 108 downstream of the throttling device 106. The throttling device 106 may be a valve or a cluster of capillaries of gradually decreasing cross-section. The compressor 102, the condenser 104, the throttling device 106 and the evaporator 108 together form a vapour-compression cycle connected through conduits 150 carrying the refrigerant. The refrigerant may be selected from compositions discussed above or may be a different composition altogether depending upon specific application.
The evaporator 108 defines a refrigerated space 110 from where the refrigerant absorbs heat and vaporizes causing a temperature drop in the refrigerated space 110. In the embodiment shown in Figure 1, the refrigerated space 110 includes only a single compartment, but more than one compartments are also possible and will be discussed later in the specification. There is also provided a circulation fan 114 adapted to augment the transfer for heat from the refrigerated space 110 to the refrigerant by causing forced convection. The compressor 102, the condenser fan 136 and the circulation fan 114 are adapted to be powered by an Alternating Current (AC) supply line 120. The compressor 102 is connected with the AC supply line 120 through a compressor switch 130. Similarly, the condenser fan 136 is connected with the AC supply line 120 through a condenser fan switch 134 and the circulation fan 114 is connected with the AC supply line 120 through a circulation fan switch 128. The compressor switch 130, the condenser fan switch 134 and the circulation fan switch 128 may be electro-mechanical in construction such as relays or may be solid state switches such as transistors, and are envisaged to be temperature controlled as will be discussed later.
It is well known that the refrigerated space 110 may be used for a number of applications such as for chilling drinks and edible items, to preserve perishable food items and laboratory samples and other things that may decompose or undergo chemical or physical change at room temperature. Therefore, in most of the cases it is imperative that a predetermined temperature threshold be always maintained as long as possible or at least restored as quickly as possible for as long as possible, in the refrigerated space 110. However, as has been presented above, the AC supply line 120 may not always be a reliable source of power, as it is prone to voltage fluctuations, cut-offs and supply breakdown issues. That makes contents in the refrigerated space 110 susceptible to damage or deterioration. Therefore, the hybrid refrigerator 100 has been designed to be operated in dual mode, a first mode being an AC operated mode and a second mode being a DC operated mode.
To enable the dual mode operation, the hybrid refrigerator 100 has been provided with an auxiliary heat exchanger 112, including a Phase Change Material (PCM). The auxiliary heat exchanger 112 has been provided within the confines of the evaporator and is configured to transfer heat to the refrigerant during the AC operated mode and receive heat from the refrigerated space 110 during the DC operated mode. Further, a rechargeable battery 118 has also been provided with the hybrid refrigerator 100. The rechargeable battery 118 is configured to be receive and store electrical power during the AC operated mode and deliver the stored electrical power during the DC operated mode. In that manner, the rechargeable battery 118 may be a Lead-acid, Lithium-ion, Lithium-polymer or a Nickel-metal-hydride battery. An auxiliary fan 116 configured to be powered from the rechargeable battery 118 during the DC operated mode has also been provided in the hybrid refrigerator 100. The purpose of the auxiliary fan 116 is to augment the transfer of heat from the refrigerated space 110 to the auxiliary heat exchanger 112 during the DC operated mode. The auxiliary fan 116 is connected with the rechargeable battery 118 through an auxiliary fan switch 132 that may again be a relay or a transistor etc.
Also, the hybrid refrigerator 100 includes a control module 122 configured to switch the hybrid refrigerator 100 between the AC operated mode and the DC operated mode. The hybrid refrigerator 100 also includes a secondary illumination source 138 and the control module 122 is configured to illuminate the refrigerated space 110 through the secondary illumination source 138, during the DC operated mode. In that manner, the secondary illumination source 138 may be a Light Emitting Diode (LED) or an incandescent bulb or a Compact Fluorescent Lamp (CFL) etc.
The refrigerated space 110 includes a first temperature sensor 124 configured to sense a first temperature value in the refrigerated space. Once a particular temperature has been achieved in the refrigerated space 110, the circulation fan 114 may be cut-off to allow the refrigerant to receive bulk of heat from the PCM in the auxiliary heat exchanger 112 rather than from the refrigerated space 110. Therefore, the circulation fan 114 is configured to be cut-off in response to the first temperature value being smaller than the first temperature threshold. For chilling applications, the first temperature threshold may lie between 0°C to 5°C. As shown in Figure 1, the first temperature sensor 124 includes a thermostat that operates on the circulation fan switch 128 to disconnect the circulation fan 114 from the AC supply line 120. The thermostat may further be a bi-metallic type or diaphragm type. In alternate embodiments, the circulation fan switch 128 may be operated from the control module 122 based on a temperature signal received by the control module 122, from the first temperature sensor 124. The first temperature sensor 124 in such scenarios may include thermistors, Resistance Temperature Detectors (RTDs), thermocouples and semiconductor based sensors etc.
The cutting-off of the circulation fan 114 allows the PCM to cool down, and if the AC power is available for long enough, to change from a liquid state to a solid state. It is to be noted here that the compressor 102 still needs to run in order to keep the refrigerant in circulation and allow the cooling and further solidification of the PCM. There is also provided a second temperature sensor 126 provided along the conduits 150, downstream of the auxiliary heat exchanger 112. The second temperature sensor 126 is configured to sense a second temperature value of the refrigerant and the compressor 102 is configured to be cut-off in response to the second temperature value being smaller than a second temperature threshold. This implies from the fact that once the PCM has been frozen, it is no longer transferring heat to the refrigerant and thus the temperature of the refrigerant is not rising. The second temperature threshold may vary between, for example, -10 to -15 °C.
Much like first temperature sensor 124, the second temperature sensor 126 includes a thermostat that operates on the compressor switch 130 to disconnect the compressor 102 from the AC supply line 120. The thermostat may further be a bi-metallic type or diaphragm type. In alternate embodiments, the compressor switch 130 may be operated from the control module 122 based on temperature signal received by the control module 122, from the second temperature sensor 126. The second temperature sensor 126 in such scenarios may include thermistors, Resistance Temperature Detectors (RTDs), thermocouples and semiconductor based sensors etc. It is also envisaged that the condenser fan 136 may also be cut-off in the same manner as the compressor 102, by the thermostat or the control module 122 operating on the condenser fan switch 134 to save power as the refrigerant will not be circulating any further in the conduits 150 as long as the compressor 102 is not operating. While there a number of constructions possible for the auxiliary heat exchanger 112 and the control module 122, some of the exemplary ones have been discussed below.
Figure 2A illustrates an exploded view of the hybrid refrigerator 100, in accordance with an embodiment 200 of the present invention. As can be seen from Figure 2A, the auxiliary heat exchanger 112 includes one or more storage tanks 220 sandwiched between two plates 212 of two respective plate and tube heat exchangers 210, the one or more storage tanks 220 being adapted to store the PCM. The one or more storage tanks 220 have been held in a stack using a frame 216. Further, the one or more storage tanks 220 include grooves 222 on respective outer surfaces of the one or more storage tanks 222, in order to accommodate tubes 214 of the two plate and tube heat exchangers 210. This arrangement allows the tubes 214 to not be in contact with the PCM and therefore prevent the tubes 214 from rusting or corrosion. Moreover, even the one or more storage tanks 220 may be made from a polymeric non-reactive material to prevent the one or more storage tanks 220 from internal or external rusting. Alternately, the one or more storage tanks 220 may also be made up of metallic materials to augment heat transfer and may also be coated or electroplated, internally or externally, to prevent corrosion. The entire assembly of the auxiliary heat exchanger 112 may be located behind a rear wall of the refrigerated space 110. Moreover, it is to be noted that the tubes 214 may be extensions and/or braches of the conduits 150 carrying the refrigerant. While the two plates 212 may be made up of a thermally conducting material, such as aluminium, to enable absorption of heat from the refrigerated space during the DC operated mode.
Figure 2B illustrates a rear perspective view of the hybrid refrigerator 100, in accordance with an embodiment 250 of the present invention. It is envisaged that the control module 122 be provided in the rear of the hybrid refrigerator 100, although this is not binding. Figure 2C illustrates a logical diagram of a control module 122, in accordance with an embodiment of the present invention. The control module 122 includes a voltage transformer 234 configured to step down the AC power being received from the AC supply line 120. Further, connected to the voltage transformer 234 is an AC/DC converter 235 configured to convert the stepped down AC power to DC power. One output of the AC/DC converter 235 is connected to the rechargeable battery 118 via a charging current regulator 140 and another output is connected to a micro-controller 232 via a first step down circuit 233. The control module 122 further includes a second step down circuit 236 configured to step down a battery voltage across terminals of the rechargeable battery118 and apply the stepped down battery voltage to the micro-controller 232. The control module 122 may also include other elements such as a memory to store machine readable instructions, an oscillator for time keeping and other elements such as amplifiers, AC/DC converters and logic coded Integrated Circuits etc.
The micro-controller 232 is configured by the machine readable instructions to regulate current being supplied to the rechargeable battery 118 during the AC operated mode. This may be achieved by the micro-controller 232 acting on the charging current regulator 140 to ensure that the rechargeable battery 118 is charged to the battery voltage across the terminals equaling a first battery threshold (for example 24V) and that the rechargeable battery 118 is not overcharged. The DC operated mode may be activated when the supply voltage of the AC supply line drops below a first supply threshold. Further the micro-controller 232 is configured to connect the rechargeable battery 118 with the auxiliary fan 116 in response to the supply voltage, of the AC supply line 120, being smaller than the first supply threshold and the battery voltage being greater than a second battery threshold, during the DC operated mode. The first supply threshold may be 90 V RMS and the second battery threshold may be for example 18.
Further, during the DC operated mode, the micro-controller 232 is configured to disconnect the rechargeable battery 118 from the auxiliary fan 116 in response to the battery voltage being smaller than a third battery threshold. The third battery threshold may be, for example 12 V. This is to ensure that the battery is not excessively drained. The connection and disconnection from the auxiliary fan 116 of the rechargeable battery 118 may be achieved by operating on the auxiliary fan switch 132. In several embodiments, the micro-controller 232 is further configured to illuminate the refrigerated space 110 through the secondary illumination source 138, during the DC operated mode, by operating on the auxiliary fan switch 132 or another switch dedicated for the secondary illumination source 138.
Figure 3 illustrates a logical diagram of the dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator 100, in accordance with another embodiment 300 of the present invention. In the embodiment illustrated in Figure 3, the refrigerated space 110 includes a refrigeration compartment 320 and a freezer compartment 310. The freezer compartment 310 includes the circulation fan 114 and the forced convection reaches the refrigeration compartment 320 through dampers and ducts etc. The freezer compartment 310 also includes the first temperature sensor 124. The first temperature sensor 124 here is configured to sense a first temperature value in the freezer compartment and the circulation fan 114 is configured to be cut-off in response to the first temperature value being smaller than the first temperature threshold. Figure 4 illustrates an exploded view of the hybrid refrigerator 100, in accordance with an embodiment 400 of the present invention.
In use, during the AC operated mode, the AC supply line 120 powers the compressor 102, the condenser fan 136 and the circulation fan 114. The circulation fan 114 is cut-off after the first temperature value in the refrigerated space 110 drops below the first temperature threshold (for example 3°C). This allows the PCM to be cooled and frozen as lesser heat is being absorbed by the refrigerant from the refrigerated space 110 and more from the PCM. Once the PCM is completely frozen, the second temperature value of the refrigerant will stop increasing and compressor 102 is cut-off in response to the second temperature value being smaller than the second temperature threshold (for example -12°C). The compressor 102 may again be restarted when any one or both scenarios occur, the scenarios including when the first temperature value increases beyond the first temperature threshold and the second temperature value increases beyond the second temperature threshold. The micro-controller 232, of the control module 122, regulates the current being supplied to the rechargeable battery 118 to ensure that the rechargeable battery 118 is charged to the first battery threshold (for example 24V), during the AC operated mode. However, when the supply voltage drops below the first supply threshold (for example 90 V RMS, may happen due to power cut, grid failure or sudden voltage drop) and sensing that the battery voltage is greater than the second battery threshold (for example 18V), the micro-controller 232 activates the DC operated mode.
In the DC operated mode, the micro-controller 232 connects the rechargeable battery 118 with the auxiliary fan 116 and maintains the connection until the battery voltage does not drop below the third battery threshold (for example 12V). This is to ensure that the rechargeable battery does not over-drain. The micro-controller 232 also illuminates the refrigerated space 110 through the secondary illumination source 138, during the DC operated mode.
The invention described above through a number of embodiments offers several advantages. The major advantage is that the hybrid refrigerator is still able to perform its intended function during power cut-off or grid failure, which is a major bonus for developing countries and rural areas where power cut-off and grid failures are a common phenomenon. The invention is simple in construction and does not demand any major design overhaul for implementation, thus providing several cost benefits including ability for upgrading existing refrigeration setups. Since the conduits carrying the refrigerant need not come in contact with the PCM, there is minimal issue of surface corrosion. Also, a wide range of PCMs may be used to achieve different levels of refrigeration (or to meet a wide range of cooling requirements) for different applications, without making any changes in the design of the setup.
Various modifications to these embodiments are apparent to those skilled in the art from the description and the accompanying drawings. The principles associated with the various embodiments described herein may be applied to other embodiments. Therefore, the description is not intended to be limited to the embodiments shown along with the accompanying drawings but is to be providing broadest scope of consistent with the principles and the novel and inventive features disclosed or suggested herein. Accordingly, the invention is anticipated to hold on to all other such alternatives, modifications, and variations that fall within the scope of the present invention and appended claims

Claims:We Claim:
1. A dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator (100) including a compressor (102), a condenser (104), a throttling device (106), an evaporator (108) and conduits (150) carrying a refrigerant, the hybrid refrigerator (100) comprising:
an auxiliary heat exchanger (112) including a Phase Change Material (PCM), the auxiliary heat exchanger (112) being configured to transfer heat to the refrigerant during an AC operated mode and receive heat from a refrigerated space (110) during a DC operated mode;
a rechargeable battery (118) configured to be receive and store electrical power during the AC operated mode and deliver the stored electrical power during the DC operated mode;
an auxiliary fan (116) configured to be powered from the rechargeable battery (118) during the DC operated mode in order to augment the transfer of heat from the refrigerated space (110) to the auxiliary heat exchanger (112); and
a control module (122) configured to switch the hybrid refrigerator (100) between the AC operated mode and the DC operated mode.
2. The hybrid refrigerator (100) as claimed in claim 1, wherein the refrigerated space (110) includes a first temperature sensor (124) configured to sense a first temperature value in the refrigerated space (110) and a circulation fan (114) configured to be cut-off in response to the first temperature value being smaller than a first temperature threshold.
3. The hybrid refrigerator (100) as claimed in claim 1, wherein the refrigerated space (110) comprises a refrigeration compartment (320) and a freezer compartment (310), the freezer compartment (310) including a circulation fan (114), wherein the freezer compartment (310) includes a first temperature sensor (124) configured to sense a first temperature value in the freezer compartment (310) and the circulation fan (114) is configured to be cut-off in response to the first temperature value being smaller than a first temperature threshold.
4. The hybrid refrigerator (100) as claimed in claim 1, comprising a second temperature sensor (126) provided along the conduits (150), downstream of the auxiliary heat exchanger (112) and configured to sense a second temperature value of the refrigerant and the compressor (102) is configured to be cut-off in response to the second temperature value being smaller than a second temperature threshold.
5. The hybrid refrigerator (100) as claimed in claim 1, wherein the auxiliary heat exchanger (112) includes one or more storage tanks (220) sandwiched between two plates (212) of two respective plate and tube heat exchangers (210), the one or more storage tanks (220) being adapted to store the PCM.
6. The hybrid refrigerator (100) as claimed in claim 5, wherein the one or more storage tanks (220) include grooves (222) on respective outer surfaces of the one or more storage tanks (220), in order to accommodate tubes (214) of the two plate and tube heat exchangers (210).
7. The hybrid refrigerator (100) as claimed in claim 1, wherein the control module (122) includes a micro-controller (232) configured to:
regulate current being supplied to the rechargeable battery (118), during the AC operated mode;
connect the rechargeable battery (118) with the auxiliary fan (116) in response to a supply voltage, of an AC supply line (120) delivering AC power to the hybrid refrigerator (100), being smaller than a first supply threshold and a battery voltage, across terminals of the rechargeable battery (118), being greater than a second battery threshold, during the DC operated mode; and
disconnect the rechargeable battery (118) from the auxiliary fan (116) in response to the battery voltage being smaller than a third battery threshold, during the DC operated mode, in order to prevent the rechargeable battery (118) from deep discharge.
8. The hybrid refrigerator (100) as claimed in in claim 1, further including a secondary illumination source (138), wherein the control module (122) is configured to illuminate the refrigerated space (110) through the secondary illumination source (138), during the DC operated mode.
9. A control module (122) for a dual mode Alternating Current (AC) and Direct Current (DC) operating hybrid refrigerator (100) including a compressor (102), a condenser (104), a throttling device (106), an evaporator (108) and conduits (150) carrying a refrigerant, the control module (122) comprising a micro-controller (232) configured to:
regulate current being supplied to the rechargeable battery (118), during the AC operated mode;
connect the rechargeable battery (118) with the auxiliary fan (116) in response to a supply voltage, of an AC supply line (120) delivering AC power to the hybrid refrigerator (100), being smaller than a first supply threshold and a battery voltage, across terminals of the rechargeable battery (118), being greater than a second battery threshold, during the DC operated mode; and
disconnect the rechargeable battery (118) from the auxiliary fan (116) in response to the battery voltage being smaller than a third battery threshold, during the DC operated mode, in order to prevent the rechargeable battery (118) from deep discharge.
10. The control module (122) as claimed in claim 9, wherein the micro-controller (232) is further configured to is configured to illuminate the refrigerated space (110) through a secondary illumination source (138), during the DC operated mode.