TECHNICAL FIELD
[001] The present invention relates to a multi-function unit suitable for automotive air conditioning system. Particularly, the invention relates to a design and manufacturing method of a multi-function unit which is able to perform the functions of internal heat exchanger as well as refrigerant noise muffler.
BACKGROUND
[002] Air conditioning system for an automotive application typically comprises a compressor, a condenser, an expansion device, and an evaporator. The compressor which is a key component of the air conditioning system is responsible for compressing and transferring the refrigerant to the condenser. The condenser extracts heat from the refrigerant and passes it to the expansion device in order to regulate the flow of refrigerant to the evaporator. The evaporator expands the refrigerant to absorb heat from a vehicle cabin and discharges the refrigerant to the compressor in order to repeat the process of heat exchange from the vehicle cabin to the outside ambient air.
[003] The aforementioned components are connected in series by tubes and hoses in order to establish fluid communication throughout the circuit. Currently, R-134a is commonly used refrigerant in automotive air conditioning system; while other refrigerants such as natural refrigerant (carbon dioxide), HFO-1234yf are also used for their low Global Warming Potential (GWP). Although the air conditioning system using natural refrigerant or low GWP refrigerant has the same basic structure, but the system efficiency deteriorates as compare to R-134a.
[004] The system level performance and efficiency could be enhanced by recovering excess and waste energy of auto air conditioning system. This is achieved by a device called internal heat exchangers, also called IHX, a type of heat exchangers, which enable heat transfer from a section of the refrigerant circuit running between condenser and expansion valve to a section of the refrigerant circuit running between evaporator and compressor. The IHX exchanges heat between high temperature refrigerant coming out of condenser and low temperature refrigerant entering into compressor. After the condenser extracts enough heat to condense the refrigerant to a liquid, it will be still pretty warm. The IHX transfers even more heat out of the liquid
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refrigerant by sub-cooling it, such that it cools the refrigerant before it reaches the expansion device, the IHX is utilizing cooling capacity that is otherwise wasted.
[005] Internal heat exchangers are generally designed as coaxial tube heat exchangers where one inner tube is enclosed by an outer tube. The liquid refrigerant flows in the interior space of the inner tube and vapour refrigerant flows in the intermediate space between inner and outer tube in counter flow fashion and heat transfer takes place between two heat exchanger mediums.
[006] The internal heat exchanger described above has its disadvantages. The installation of such a heat exchanger into an engine compartment is difficult because existing vehicle package hardly offers any room for the individual adaptation. Furthermore, the known coaxial heat exchangers also exhibit low heat transfer efficiency.
[007] Apart from the need of efficiency increase of the existing air conditioning systems, it is highly essential to muffle a noise in and at vehicle in order to meet the increasing comfort and quality demands. As the vehicles are equipped with large number systems, the auto air conditioning system might have such undesirable noise levels not only from the blower unit, turbulences, valves and connection blocks, but also from refrigerant pulsations created by the compressor itself.
[008] The compressor, during the process of compressing the refrigerant causes pressure pulsations of the refrigerant. In some of the cases due to typical layout of piping these refrigerant pulsations are transmitted to the internal vehicle cabin part of air conditioning system, it generates noise within the interior of the vehicle, thus affecting the comfort of the vehicle occupants. Existing auto air conditioning systems usually employ a device called muffler or silencer, which is placed at suction or discharge side of the compressor in an air conditioning circuit in order to dampen the refrigerant noise created by such pressure pulsations.
[009] Various designs of internal heat exchangers and muffler are already exists in the practice to achieve similar or lesser improvement in the performance. However, they are placed in air conditioning circuit as physically separate devices, which incur significant cost and packaging
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space. For automotive application, it is desirable to have the air conditioning systems which are less in weight and occupies less space. In addition, they must be constructed to reduce the complexity of the production process as well as the enabling of cost saving potentials.
[010] In view of the foregoing, at least one object is to provide an improved internal heat exchanger for an automotive air-conditioning system that can be produced efficiently, cost-effectively and simply. Another object is to provide a muffler which can readily be adapted into engine compartment to reduce the noise in passenger compartment. Other objects such as desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.
SUMMARY
[011] The present invention discloses a novel multi-function unit capable of performing the functions of internal heat exchanger (IHX) and muffler simultaneously.
[012] In accordance with features of the invention, the multi-function unit which not only acts as an internal heat exchanger by heat exchanging between high temperature refrigerant coming out of condenser and low temperature refrigerant entering into compressor, but also serves the purpose of damping out the refrigerant noise, thus achieving compact, efficient, cost effective and ease of manufacturing solution for energy recovery as well as for noise control. This multi-function unit is called as IHX cum muffler.
[013] To achieve at least some of the objects of the invention, the present invention replaces the concentric tubes used in the traditional coaxial tubes with a helical coil and confining cylindrical body to make it a multi-function unit. The method and design of both fluid carrying channels i.e., the helical coil and the cylindrical body is such that it results in an improved heat exchange along with muffling effect. The helical coil not only allows maximum heat transfer area in a confined space, but also serves the purpose of noise dampening by obstructing and absorbing the sound waves coming along with low pressure vapor refrigerant from evaporator.
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[014] In accomplishing the foregoing objects, there has been provided according to an aspect of the present invention an IHX cum muffler assembly, comprising a cylindrical body that includes a first end, a second end, a first port and a second port; an end cap that closes the first end of the cylindrical body; a heat exchanger coil comprising of a first tube end and a second tube end extending away perpendicularly; a connector pipe to connect the second tube end of the heat exchanger coil. The heat exchanger coil is disposed in a cylindrical cavity provided inside the cylindrical body. The heat exchanger coil includes a plurality of adjacent turns spaced according to a predetermined coil pitch. The end cap is provided with a port to support the first tube end of the heat exchanger coil. The first tube end and the second tube end are given at the opposite ends of the heat exchanger coil and two tube ends are perpendicular to each other.
[015] In an embodiment, the heat exchanger coil is provided in the form of a helix and here onwards, it will be called as helical coil. An outer diameter of the helical coil is sized to fit substantially within the cylindrical cavity with a predetermined annular gap between the coil outer diameter and attenuating zone diameter of the cylindrical cavity. The annular gap is sized to provide a substantially unobstructed and least resistance pathway for refrigerant flow through the cylindrical cavity.
[016] In an another embodiment, the first tube end of the helical coil is connected to another connector pipe inserted into a third port of the cylindrical body.
[017] In another embodiment, the helical coil is made in such a way that the first tube end and the second tube end are on the same side of the helical coil. In this case, the end cap is provided with two ports to accommodate both tube ends.
[018] In yet another embodiment, the helical coil can be tube and fin type in order to increase heat transfer area on vapor side.
[019] In an embodiment, the connector pipe is cladded. In another embodiment, the connector pipe is non-cladded and a clad ring, which acts as a brazing agent, is used between the connector pipe and the second tube end of the helical coil.
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[020] In an embodiment, the cylindrical body has a plurality of attenuation zones disposed along the axial direction. In another embodiment, the axial distance between the attenuation zones is same. In yet another embodiment, the axial distance between the attenuation zones is gradually increasing or decreasing and distances between attenuating zones are of predetermined lengths not only based upon a frequency of the pressure pulsations to be attenuated, but also to achieve maximum heat exchange between the helical coil and cylindrical body due to increased turbulence inside the cylindrical body. The diameter of the cylindrical cavity at attenuation zones is smaller than the diameter of the cylindrical body. The cylindrical body is made as single piece, yet in another embodiment, it can be made in two pieces.
[021] Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments, construed in conjunction with the appended claims.
[022] It will be appreciated that the features of the present disclosure are susceptible to being combined in various combinations without departing from the spirit and the scope of the disclosure, as defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[023] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those skilled in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
[024] Embodiments of the present disclosure will now be described, by way of an example only, with reference to the following diagrams wherein:
[025] FIG. 1 illustrates an isometric view of an IHX cum muffler assembly in accordance with an embodiment of the disclosure;
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[026] FIG. 2 illustrates an exploded view of the IHX cum muffler assembly showing the cylindrical body, helical coil, connector pipe and end cap to seal the first end of the cylindrical body.
[027] FIG. 3 illustrates a longitudinal cross sectional view, when cut through the first port and the second port of the IHX cum muffler assembly showing the helical coil in a predetermined position.
[028] FIG. 4 illustrates another longitudinal cross sectional view of the IHX cum muffler assembly showing the helical coil and attenuation zones in accordance with an embodiment of the disclosure.
[029] FIG. 5A is a perspective view of the operating parts of the automotive air conditioning system embodying a presently preferred embodiment of the IHX cum muffler in accordance with the present invention.
[030] FIG. 5B is an enlarged view of the automotive air conditioning system of FIG. 5A.
DETAILED DESCRIPTION OF EMBODIMENTS
[031] The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
[032] In accordance with a preferred embodiment of the present invention, an automotive air conditioning system comprises compressor, condenser, expansion device, evaporator, and refrigerant tubes and hoses hydraulically connecting the aforementioned components in series. The air conditioning system further includes internal heat exchanger to increase the heat transfer capacity of air conditioning system, or in other words, it improves coefficient of performance (COP) of the system. In addition to that, a silencing device called muffler is also provided in the air conditioning circuit to reduce the noise due to refrigerant pressure pulsation. Hence, the given invention discloses a multi-function unit which is capable of improving the system COP as well as it provides a solution to flow generated noise where it acts as a muffler to reduce the pressure pulsation noise.
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[033] FIG.1 illustrates an isometric view of an IHX cum muffler assembly 100, said IHX cum muffler 100 comprising a cylindrical body 102, a helical coil 104, an end cap 106 and a connector pipe 108. The cylindrical body 102 includes a first end 110, a second end 112, a first port 114 and a second port 116. The first port 114 and the second end 112 acts as an inlet and an outlet for refrigerant vapour respectively. In an alternative embodiment, provision can be made in the end cap 106 to act as inlet for refrigerant vapour. The second end 112 is in the form of annular flange which is integrally formed with the cylindrical body 102. In an alternative embodiment, the second end is made as a separate part.
[034] FIG. 2 illustrates an exploded view of IHX cum muffler assembly 100 comprising cylindrical body 102 having an interior surface which defines a substantially cylindrical cavity, the helical coil 104 to be disposed coaxially within the cylindrical cavity and the end cap 106 to hydraulically seal the first end 110 of the cylindrical body 102. The end cap 106 includes a port 118 to provide support and passage for a first tube end 200 of the helical coil 104. The connector pipe 108 is provided to connect a second tube end 202 of the helical coil 104.The cylindrical body 102 includes an exterior surface, the first end 110 and axially opposed second end 112, the first port 114 and the second port 116 and a plurality of attenuation zones 206 disposed about the central axis of the cylindrical body 102. A circumferential gap between two adjacent attenuating zones 206 can be selected in such a way that it guides the helical coil 104 to a predetermined path to locate the second tube end 202 to second port 116 of the cylindrical body 102.
[035] In the auto air conditioning system, the second tube end 202 of the helical coil 104 is connected downstream from the condenser and the first tube end 200 is connected upstream from the expansion device to draw high pressure liquid refrigerant from the condenser for further cooling. Similarly, the cylindrical body 102 includes inlet and outlet for low pressure vapour refrigerant. The first port 114 of the cylindrical body 102 is connected downstream from the evaporator and the second end 112 is connected upstream from the compressor to pre-heat the low pressure vapour refrigerant prior it’s entery into compressor.
[036] FIG. 3 illustrates a longitudinal cross sectional view of IHX cum muffler assembly 100, when cut through the first port 114 and the second port 116 of the IHX cum muffler assembly
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100 showing the helical coil104 in a predetermined position. The helical coil 104 includes the first tube end 200 that extends away from the first end 110 of the cylindrical body 102 through the port 118 provided in the end cap 106. The second tube end 202 of the helical coil 104 is provided with a collar 302. The collar 302 can be developed by bulging process or any other process. The first tube end 200 may also be provided with a similar type of collar, if needed. The port 118 in the end cap 106 provides support for the first tube end 200 of the helical coil 104 at first end 110 of the cylindrical body 102, while at the opposite end, the connector pipe 108 is provided to support the second tube end 202. The connector pipe 108 is inserted through the second port 116 and rests on the collar 302 provided at the second tube end 202 of the helical coil 104.
[037] FIG. 4 illustrates another longitudinal cross sectional view of IHX cum muffler assembly 100. The helical coil 104 includes an outer diameter "d" and a coil tube diameter "dt". The helical coil 104 outer diameter "d" is selected to fit into the cylindrical body diameter "D" coaxially. The axial distance between adjacent coils is defined as coil pitch "p". A diameter "da" of cylindrical cavity at attenuation zones 206 is smaller than the diameter "D" of the cylindrical body 102, thus defining an annular gap "G" between the helical coil 104 and the cylindrical cavity at attenuation zones 206. The annular gap "G" is sized to permit an unimpeded flow of refrigerant through the cylindrical cavity.
[038] FIG. 5A illustrates a perspective view of the automotive air conditioning system and FIG. 5B illustrates an enlarged view of FIG. 5A. The automotive air conditioning system 500 comprises a compressor 502, a condenser 504, an expansion device 506 and an evaporator 508. The aforementioned components are connected in series in a known manner to establish fluid communication through refrigerant tubes. Low pressure vapor refrigerant exiting from evaporator 508 is drawn and compressed by compressor 502 into a high pressure vapor refrigerant, which is then discharged to condenser 504. Within condenser 504, the high pressure vapor refrigerant is condensed to a high pressure liquid refrigerant. The high pressure liquid refrigerant then passes through expansion device 506 that regulates the flow of the refrigerant to evaporator 508, in which the high pressure liquid refrigerant expands into the low pressure vapor
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refrigerant as it absorbs heat from the cabin of an automobile. The dashed line and long dashed line in FIG. 5B indicate engine comportment boundary and HVAC boundary respectively.
[039] The automotive air conditioning system further includes the internal heat exchanger to increase the heat transfer capacity of air conditioning system. As shown in FIG. 5A and FIG. 5B, on high pressure side, the IHX cum muffler assembly 100 is arranged between downstream of the condenser 504 and upstream of the expansion device 506. On the low-pressure side, the IHX cum muffler assembly 100 is provided between downstream of the evaporator 508 and upstream of the compressor 502. The relatively low temperature low pressure vapor refrigerant exiting the evaporator 508 is used to sub-cool the relatively high temperature high pressure liquid refrigerant exiting the condenser 504 prior to the expansion device 506. Within the IHX cum muffler assembly 100, the high pressure liquid refrigerant from condenser 504 and low pressure vapor refrigerant from evaporator 508 flows in counter flow fashion to have a maximum heat exchange between two mediums.
[040] Referring back to FIG. 4 in addition to FIG. 5, when the low pressure vapor refrigerant flows from the evaporator 508 to the IHX cum muffler assembly 100, it expands against inner walls of the cylindrical body 102, which actually results in reduced refrigerant noise by conversion of sound energy into potential energy. The low pressure vapor refrigerant further expands and turbulence is created through the turns of the helical coil 104, so that part of acoustic energy is converted to potential energy. Thus the propagation of refrigerant sound along the cylindrical cavity is partially inhibited and delayed due to resistance caused by inner walls of the cylindrical body 102 as well as helical tubes of the helical coil 104. Also as the size of the cylindrical body 102 is larger than the typical muffler, flow energy of refrigerant is effectively absorbed. The flow path and delay time (retention time) of the refrigerant in the cylindrical body 102 is increased, hence the flow is slow down effectively.
[041] Also the cylindrical body 102 of IHX cum muffler assembly 100 is specially designed to include the plurality of attenuation zones 206, which is helpful in dying out of acoustic waves. As it is seen in FIG. 4, the diameter "da" of cylindrical cavity at plurality of attenuation zones 206 is smaller than the diameter "D" of the cylindrical body 102, thus forming a contracting area
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and an expansion area respectively. As the refrigerant flows through these areas within the cylindrical cavity, it keeps on contracting and expanding along the axial direction, thus helping in silencing the noise.
[042] Although the present invention focuses on usage of IHX cum muffler in the automotive air conditioning system, the variants of the IHX cum muffler can also be developed for packaged units, window air conditioners and for refrigeration systems.
[043] Modifications to embodiments of the present disclosure described above are possible without deviating from the spirit and the scope of the disclosure as defined in the accompanying claims. Expressions such as “comprise” and “include”, and variations such as “comprises”, “comprising”, “includes”, and including are intended to be construed in a non-exclusive manner, namely allowing for items, components, or elements not explicitly described (or recited) also to be present. Reference to the singular is also to be construed to relate to the plural, except where explicitly stated.
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We Claim :
1. An internal heat exchanger cum muffler (100) for automotive air conditioning system, comprising:
a cylindrical body (102) comprising a first end (110) and a second end (112) axially opposed to the first end (110), and an interior surface defining a substantially cylindrical cavity, the cylindrical body (102) having a cylindrical body diameter;
a helical coil (104) coaxially disposed within said cylindrical cavity, said helical coil (104) comprising a first tube end (200) and a second tube end (202), and having a coil outer diameter;
a plurality of attenuating zones (206) being axially aligned and spaced apart along the longitudinal axis of the cylindrical body (102), wherein a cylindrical cavity diameter at said plurality of attenuation zones (206) is smaller than the cylindrical body diameter and defines an annular gap between the coil outer diameter and the cylindrical cavity diameter at said plurality of attenuation zones (206);
whereby a noise generated due to pressure pulsations of a refrigerant within said automotive air conditioning system is dampened by flowing of the refrigerant through the cylindrical cavity in the cylindrical body (102), the helical coil (104) and the plurality of attenuation zones (206).
2. The internal heat exchanger cum muffler (100) as claimed in claim 1, wherein the cylindrical body (102) further comprising:
a first port (114) and a second port (116);
an end cap (106) that closes the first end (110) of the cylindrical body (102), said end cap (106) comprising a port (118) to facilitate the first tube end (200) of said helical coil (104) to pass through;
a connector pipe (108) to connect and locate the second tube end (202) of the helical coil (104) through the second port (116) of said cylindrical body (102).
3. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the noise generated by the refrigerant is dampened by obstructing and absorbing the noise by the
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cylindrical cavity in the cylindrical body (102), the helical coil (104) and the plurality of attenuation zones (206), due to resistance caused by inner walls of the cylindrical body (102), turbulence produced by the helical coil (104) and a contracting area and an expansion area formed by the plurality of attenuation zones (206).
4. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein a circumferential gap between adjacent attenuating zones of said plurality of attenuation zones (206) is selected in order to guide the helical coil (104) to a predetermined path to locate the second tube end (202) to the second port (116) of the cylindrical body (102).
5. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein distances between adjacent attenuating zones of said plurality of attenuation zones (206) are of predetermined lengths not only based upon a frequency of the pressure pulsations to be attenuated, but also to achieve maximum heat exchange between the helical coil (104) and the cylindrical body (102) due to increased turbulence inside the cylindrical body.
6. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the annular gap is sized to provide a substantially unobstructed pathway for refrigerant flow through the cylindrical cavity.
7. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein either the first tube end (200) or the second tube end (202) or both (200, 202) of the helical coil (104) has a bulging profile.
8. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the first tube end (200) and the second tube end (202) are at the opposite ends of the helical coil (104) and are perpendicular to each other.
9. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the first tube end (200) and the second tube end (202) are on the same side of the helical coil (104) and the end
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cap (106) is provided with two ports to accommodate both the first tube end (200) and the second tube end (202).
10. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the connector pipe (108) is cladded.
11. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the connector pipe (108) is non-cladded and a clad ring acts as a brazing agent between the connector pipe (108) and the second tube end (202) of the helical coil (104).
12. The internal heat exchanger cum muffler (100) as claimed in claim 2, wherein the cylindrical body (102) is made from a single piece or two piece.