RU2722930C2 - Multi-stroke microchannel heat exchanger with multiple bent plates - Google Patents

Abstract

FIELD: heat exchange.SUBSTANCE: disclosed is a heat exchanger comprising a first header and a second header separated from each other. Plurality of tubular segments spaced apart in parallel connect the first and second headers hydraulically. Plurality of tubular segments comprise a bend forming the first plate and the second plate. Second plate is located at an angle to the first plate. Heat exchanger has a multi-stroke configuration relative to the air flow, containing at least the first stroke and the second stroke. First stroke has the first flow orientation, and the second stroke has the second flow orientation. Second flow orientation differs from the first flow orientation.EFFECT: multi-stroke microchannel heat exchanger with multiple bent plates is proposed.19 cl, 9 dwg

Description

BACKGROUND

[0001] The present invention relates generally to a heat pump and artificial cooling applications, and more particularly to a microchannel heat exchanger adapted to be used in a heat pump or cooling system.

[0002] Heating, ventilation, air conditioning and cooling (HVAC) systems include heat exchangers for removing or receiving heat between the circulation of the refrigerant within the system and the environment. One type of heat exchanger, which is becoming increasingly popular due to its compactness, light weight, structural rigidity and excellent performance characteristics, is a microchannel or minichannel heat exchanger. Compared to traditional plate fin heat exchangers, microchannel heat exchangers are more environmentally friendly because they use less refrigerant to charge the system, which is typically a high-GWP synthetic fluid (global warming potential). A microchannel heat exchanger contains two or more retaining forms, such as tubes, through which a cooling or heating fluid (i.e., refrigerant or glycol solution) circulates. Tubes, as a rule, have a flattened cross section and several parallel channels for flow. The ribs are usually arranged to pass between the tubes to increase the effective interchange of thermal energy between the heating / cooling fluid and the environment. The ribs have a corrugated pattern, contain blinds to further improve heat transfer and, as a rule, are attached to the tubes by soldering in a protective atmosphere.

[0003] In a heat pump and artificial cooling applications, when a microchannel heat exchanger is used as an evaporator, moisture present in the air stream supplied to the heat exchanger for cooling can condense and then freeze on the outer surfaces of the heat exchanger. The resulting ice or frost can block the air flow through the heat exchanger, thereby reducing the efficiency and functionality of the heat exchanger and the HVAC system. Microchannel heat exchangers can freeze faster than round tube heat exchangers and plate fin heat exchangers, and therefore require more frequent defrosting, reducing the useful life of the heat exchanger and overall productivity. Therefore, it is desirable to create a microchannel heat exchanger with increased frost resistance and increased productivity.

SUMMARY OF THE INVENTION

[0004] According to one embodiment of the invention, a heat exchanger is provided comprising a first collector and a second collector separated from each other. A plurality of tubular segments arranged in a spaced parallel relationship fluidly couple the first and second manifold. Many tubular segments comprise a bend forming a first plate and a second plate. The second plate is located at an angle to the first plate. The heat exchanger has a multi-way configuration relative to the air flow, including at least a first stroke and a second stroke. The first move has a first flow orientation, and the second move has a second flow orientation. The second flow orientation is different from the first flow orientation.

[0005] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the first stroke has a transverse parallel flow orientation.

[0006] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the second stroke has a transverse orientation of the oncoming flow.

[0007] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the first part of the plurality of tubular segments form the first stroke, and the second part of the plurality of tubular segments form the second stroke.

[0008] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the number of tubular segments located within each of the first stroke and the second stroke is selected to reduce the formation of frost on the heat exchanger.

[0009] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the second part has a larger number of tubular segments than the first part.

[0010] In addition to one or more of the features described above, or alternatively, in additional embodiments of the invention, the ratio of the tubular segments in the first part and in the second part is 20:80.

[0011] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the ratio of the tubular segments in the first part and in the second part is 40:60.

[0012] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, a divider is located within the first collector to form a first section and a second section. The first section is fluidly coupled to the first part of the plurality of tubular segments, and the second section is fluidly coupled to the second part of the plurality of tubular segments.

[0013] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, a distributor is located inside the first section of the first manifold.

[0014] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, a dispenser is provided between the first stroke and the second stroke.

[0015] In addition to one or more of the features described above, or alternatively, in additional embodiments of the invention, the bend is made around an axis located perpendicular to the longitudinal axis of the plurality of tubular segments.

[0016] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the bend of each tubular segment comprises a funnel fold of the tape.

[0017] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, the angle between the second plate and the first plate is about 180.

[0018] In addition to one or more of the features described above, or alternatively, in further embodiments, each of the plurality of tubular segments is a microchannel tube having a plurality of discrete flow channels formed therein.

[0019] A heat exchanger is provided comprising a first collector and a second collector separated from each other. A plurality of tubular segments arranged in a spaced parallel relationship fluidly couple the first and second manifold. Many tubular segments comprise a bend forming a first plate and a second plate. The second plate is located at an angle to the first plate. The heat exchanger has a multi-way configuration relative to the air flow, including at least a first stroke and a second stroke. Both the inlet of the heat exchanger and the outlet of the heat exchanger are made in the first plate.

[0020] In addition to one or more of the features described above, or alternatively, in additional embodiments of the invention, the first part of the plurality of tubular segments forms a first stroke, and the second part of the plurality of tubular segments forms a second stroke. The first part has fewer tubular segments than the second part.

[0021] In addition to one or more of the features described above, or alternatively, in further embodiments of the invention, each of the plurality of tubular segments is a microchannel tube having a plurality of discrete flow channels formed therein.

[0022] In addition to one or more of the features described above, or alternatively, in further embodiments, the distributor is positioned adjacent to the inlet of each stroke of the heat exchanger.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[0023] The subject matter of the invention, which is regarded as an invention, is particularly indicated and clearly stated in the claims in the concluding part of this description. The above and other features, as well as the advantages of this invention, are obvious from the following detailed description in combination with the accompanying graphic materials, in which:

[0024] in FIG. 1 is a schematic diagram of an example cooling cycle by evaporation of a refrigerant of a cooling system;

[0025] in FIG. 2 illustrates a side view of a microchannel heat exchanger according to an embodiment of the invention before a bending operation;

[0026] in FIG. 3 illustrates a cross-sectional view of tubular segments of a microchannel heat exchanger according to an embodiment of the invention;

[0027] in FIG. 4 illustrates a perspective view of a microchannel heat exchanger according to an embodiment of the invention;

[0028] in FIG. 5 is a front view of a microchannel heat exchanger according to another embodiment of the invention;

[0029] in FIG. 6 illustrates a side view of a microchannel heat exchanger according to another embodiment of the invention;

[0030] in FIG. 7 illustrates a perspective view of a microchannel heat exchanger according to yet another embodiment of the invention; and

[0031] in FIG. 7a is a cross-sectional view of the microchannel heat exchanger of FIG. 6 along section line XX according to yet another embodiment of the invention; and

[0032] in FIG. 7b is a cross-sectional view of the microchannel heat exchanger of FIG. 6 along the Y-Y cut line according to another embodiment of the invention.

[0033] A detailed description of the invention sets forth embodiments of the invention together with advantages and features as an example with reference to graphic materials.

DETAILED DESCRIPTION OF THE INVENTION

[0034] With reference to FIG. 1, a vapor compression cycle 20 of a heat pump of an air conditioning or cooling system is schematically illustrated. Typical air conditioning or cooling systems include, but are not limited to, for example, split systems, embedded systems, rooftop refrigerators, supermarkets, and transportation refrigeration systems. The refrigerant R is configured to circulate through the vapor compression cycle 20, so that the refrigerant R absorbs heat during evaporation at low temperature and pressure and gives off heat during condensation at high temperature and pressure.

[0035] In this cycle 20, refrigerant R flows counterclockwise, as indicated by the arrow. The compressor 22 receives refrigerant vapor from the evaporator 24 and compresses it to high temperatures and pressures, with relatively hot steam, passing to the condenser 26, where it is cooled and condensed to a liquid state by mutual heat exchange with a cooling medium (not shown), such as air . Then, the liquid refrigerant R passes from the condenser 26 to the throttle device 28, in which the refrigerant R expands to a two-phase liquid / vapor state with a low temperature as it passes to the evaporator 24. Then the low pressure steam is returned to the compressor 22, where the cycle repeats. The vapor compression cycle 20 described herein is a heat pump cycle operating in a heating mode. As a result, the outer coil of the cycle 20 is made in the form of an evaporator 24, and the inner coil is made in the form of a condenser. When executed as a heat pump, the vapor compression cycle further comprises a four-way valve 29 located downstream of the compressor 22 relative to the refrigerant stream, which reverses the direction of the refrigerant stream through cycle 20 to switch between cooling and heating. It should be understood that the cooling cycle 20 shown in FIG. 1 is a simplified representation of an HVAC system, and many improvements and features known in the art can be included schematically.

[0036] With reference to FIG. 2, an example of a heat exchanger 30 adapted for use in a steam compression system 20 is illustrated in more detail. The heat exchanger 30 can be used either as a condenser 24 or as an evaporator 28 in a steam compression system 20. The heat exchanger 30 comprises at least a first a collector or collector 32, a second collector or collector 34 located at a distance from the collector 32, and a plurality of tubular segments 36 spaced apart in parallel, connecting the first collector 32 and the second collector 34. In the illustrated, non-limiting embodiments, the first collector 32 and the second collector 34 is oriented generally in the horizontal direction and the tubular segments 36 of the heat exchanger extend generally in the vertical direction between the two collectors 32, 34. However, other configurations, such as where the first and second collectors 32, 34 are located along essentially in the vertical direction are also included in the scope of the invention.

[0037] With reference to FIG. 3, an example of a cross-section of tubular segments 36 of a heat exchanger is illustrated. The tubular segments 36 comprise a flattened microchannel heat exchanger tube having a leading edge 40, a trailing edge 42, a first surface 44 and a second surface 46. The leading edge 40 of each heat exchanger tube 36 is located upstream of its corresponding trailing edge 42 relative to the air flow A passing through heat exchanger 36. The internal flow part of each tubular segment 36 of the heat exchanger can be divided by internal walls into a plurality of discrete flow channels 48 that extend along the entire length of the tubes 36 from the inlet end to the outlet end and establish fluid communication between the respective first and second collectors 32, 34 The flow channels 48 may have a circular cross section, a rectangular cross section, a trapezoidal cross section, a triangular cross section, or another non-circular cross section. Heat exchanger tubes 36 containing discrete flow channels 48 can be made using known techniques and materials, including, but not limited to, extrusion or bending.

[0038] The tubular heat exchanger segments 36 disclosed herein further comprise a plurality of ribs 50. In an embodiment, the ribs 50 are made of a single continuous ribbon of rib material, closely folded by a ribbon-like snake method, thereby providing a plurality of closely spaced ribs that extend into generally perpendicular to the tubular segments 36 of the heat exchanger. Heat exchange between one or more fluids inside the tubular segments 36 of the heat exchanger and the air flow A is through the outer surfaces 44, 46 of the tubular segments 36 of the heat exchanger, which together form the primary surface of the heat exchanger, and also through the surface of the heat exchanger fins 50, which forms the secondary surface of the heat exchanger.

[0039] The heat exchanger 30 has a multi-pass configuration with respect to air flow A. To create a multi-pass configuration in one embodiment of the invention illustrated in FIG. 4-6, a multi-way configuration is achieved by performing at least one bend 60 in each tubular segment 36 of the heat exchanger 30. Bend 60 is made around an axis extending substantially perpendicular to the longitudinal axis of the tubular segments 36. In the illustrated embodiment, the bend 60 is funnel fold of the tape (see Fig. 6), made by bending and folding tubular segments 36 of the heat exchanger around the core (not shown); however, other types of bends are included in the scope of the invention. In an embodiment of the invention, a plurality of bends 60 can be made in various places along the length of the plurality of tubular segments 36 of the heat exchanger.

[0040] Bend 60 at least partially forms a first section 62 and a second section 64 of each of the plurality of tubular segments 36, wherein in the bend configuration, the first section 62 forms a first plate 66 of the heat exchanger 30 with respect to air flow A, and the second section 64 forms a second plate 68 heat exchanger 30 relative to airflow A. In the illustrated non-limiting embodiment, bending 60 is made at approximately the midpoint of the tubular segments 36 between the opposing first and second headers 32, 34, so that the first and second sections 62, 64 are generally the same size. However, other embodiments where the first section 62 and the second section 64 are substantially different in length are included in the scope of the invention.

[0041] As illustrated in the figures, the heat exchanger 30 may be configured such that the first plate 66 is placed at an obtuse angle with respect to the second plate 68. Alternatively or additionally, the heat exchanger 30 may also be configured such that the first plate 66 is located either at an acute angle, or essentially parallel to (Fig. 5), the second plate 68. As a result of bending 60 between the first and second plates 66, 68, the heat exchanger 30 can be made in the form of a coil A-shaped or V-shaped. The formation of the heat exchanger 30 by bending the tubular segments 36 leads to the fact that the heat exchanger 30 has a reduced bending radius, as, for example, when performed with a bend of 180 °. As a result, the heat exchanger 30 can be adapted to fit into the dimensions defined by existing air conditioning and cooling systems.

[0042] Again with reference to FIG. 2, the plurality of first ribs 50a extend from the first plate 66, and the plurality of second ribs 50b extend from the second plate 68 of the heat exchanger 30. In embodiments where the heat exchanger 30 is formed by bending a plurality of tubular segments 36, there are no ribs within the bending portion 60 of each tubular segment 36. The first ribs 50a and the second ribs 50b may be essentially identical, or alternatively, may differ in one of: size, shape and density.

[0043] Conventional heat exchangers made as heat pump evaporators typically have a parallel flow configuration to achieve the desired efficiency. However, the orientation of the parallel flow leads to poor frost resistance in microchannel heat exchangers. The heat exchanger 30 may have any of a number of multi-way configurations, so that the refrigerant passes through the heat exchanger 30, for example, in one or more of: parallel flow orientation, transverse flow orientation and counter flow orientation. In one embodiment, the divider 38 may be located inside one or two of the first and second collectors 32, 34 to increase the number of strokes, and therefore the length of the flow path, inside the heat exchanger 30.

[0044] In the embodiment of the invention illustrated in FIG. 7, a divider 38 is located inside the first collector 32 to form a first section 32a and a second section 32b. As a result, the refrigerant supplied to the inlet (not shown) of the first collector 32 is configured to flow only through the portion 36 a of the tubular segments 36 fluidly coupled to the first section 32 a. After passing through the first portion 36a of the tubular segments 36, the refrigerant moves to the second collector 34. Inside the second collector 34, the refrigerant flows from the first portion 36a of the tubular segments 36 towards the second, adjacent portion 36b of the tubular segments 36. The second portion 36b may contain the same the very number or different number of tubular segments 36 as the first part 36a. In an embodiment, the ratio of the tubular segments in the first part 36a and in the second part 36b is 20:80 or, alternatively, 40:60.

[0045] The second collector 34 may likewise comprise a divider 38 for detecting fluid-connected first and second sections 34a, 34b. The refrigerant is adapted to flow from the second collector 34 through the second portion 36b of the tubular segments 36 fluidly coupled to the second section 32b of the first collector 32 and an outlet (not shown) formed therein. Although the illustrated heat exchanger 30 comprises two distinctive parts of the tubular segments 36 of the heat exchanger, heat exchangers 30 having any number of parts of the tubular segments 36 that form discrete passages through the heat exchanger 30 are within the scope of the invention.

[0046] Evenly distributing a refrigerant within a collector, such as collector 32 or 34 or an intermediate collector, for example, is a common problem with microchannel heat exchangers. In general, it is easy to evenly distribute the refrigerant along the length of a small collector, but as the length of the collector increases, improper distribution becomes an increasingly significant problem.

[0047] The heat exchanger 30 disclosed herein has an improved distribution of the refrigerant by separating at least one of the first and second collectors 32, 34 using a divider 38. As a result, the length of the manifold in which the refrigerant is to be evenly distributed is reduced. Furthermore, by bending the heat exchanger 30, the need for an intermediate collector is eliminated, and hence the distribution problems associated with such an collector. In an embodiment of the invention, a longitudinally extending distributor insert 70, as is known in the art, may be located within one or more sections of either the first collector 32 or the second collector 34 of the heat exchanger 30. The distributor insert 70 is generally centered in the inner part of the collector and is configured to evenly distribute the flow of the refrigerant between the plurality of heat exchanger tubes 36 connected in fluid with it. In the illustrated, non-limiting embodiment, the first distributor insert 70 is located inside the first section 32a of the collector 32. The distributor insert 70 is located inside the first section 32 of the first collector 30, generally over part or all of the length of section 32, so that the refrigerant provided therein , will be more evenly distributed over the entire length of the first section 32, thereby improving the heat transfer of the heat exchanger 30. Alternatively or in addition, another distributor 70 may similarly be placed inside the second section 34b of the second collector 34.

[0048] Since the direction of the air flow A is the same relative to the first and second parts 36a, 36b of the tubular segments 36, the refrigerant inside each of these parts has a different flow orientation. For example, in the illustrated, non-limiting embodiment, air A flows from the first collector 32 toward the second collector 34. By supplying the refrigerant to the inlet of the first section 32a of the first collector 32, the refrigerant flowing through the first portion 36a of the tubular segments 36, as in detail illustrated in FIG. 7a has a transverse parallel flow orientation. In addition, the refrigerant flowing through the second portion 36b of the tubular segments 36, as illustrated in more detail in FIG. 7b has a transverse oncoming flow.

[0049] In conventional heat exchangers having a parallel flow configuration, the two-phase refrigerant enters the first low-vapor section 32, which is configured to absorb heat from the air, and begins to boil. Since boiling occurs at a constant temperature, the temperature difference between the air and the refrigerant gradually decreases as the air flows through the heat exchanger 30, reducing heat transfer, which occurs, in particular, in the downstream plate 68. This behavior reduces the overall efficiency of the heat exchanger and also leads to lower evaporation temperatures, which adversely affects both system efficiency and frost resistance.

[0050] By dividing the plurality of tubular segments 36 of the heat exchanger 30 in the form of an evaporator into the first part 36a and the second part 36b to form two successive strokes, the partially evaporated refrigerant is supplied from the first stroke to the second stroke. In the second step, the refrigerant completely boils, and superheated steam leaves the upstream side of the heat exchanger 30. By performing the second stroke so that the refrigerant flow intersects with the air flow A, the temperature difference between the air and the refrigerant will be more favorable. In addition, the presence of superheated steam on the upstream side of the heat exchanger 30 prevents excessive frost accumulation and increases frost resistance.

[0051] The heat exchanger 30, having a multi-way design with several curved plates, allows to optimize the pressure drop of the refrigerant, thereby improving performance. During the flow of the refrigerant through the tubular segments 36 of the heat exchanger, the vapor content continuously increases, leading to an increased volumetric flow rate and, consequently, an increase in pressure drop. By gradually increasing the internal flow coverage when moving the refrigerant from one stroke to another, the pressure drop can be significantly improved compared to traditional heat exchangers. Improving the operational efficiency of the heat exchanger 30 may provide the possibility of reducing the size of the heat exchanger 30 necessary for the desired application. Alternatively, the size of other system components, such as a compressor, for example, can be reduced, which in turn will cause an even higher evaporation temperature and a further reduction in the number of defrost cycles, as well as a significant increase in system performance.

[0052] While the present invention is specifically illustrated and described with reference to typical embodiments, as illustrated in the graphic materials, those skilled in the art will understand that various modifications can be made without departing from the scope and spirit of the invention. Therefore, it is intended that the present disclosure is not only not limited to the specific embodiment (s), but that the disclosure will include all embodiments within the scope of the appended claims. In particular, similar principles and relationships can be extended to rooftop applications and compact vertical installations.

Claims (35)

1. A heat exchanger containing: first collector; a second collector separated from the first collector; a plurality of tubular segments spaced parallel to each other and hydraulically connecting the first collector and the second collector, the plurality of tubular segments comprising a bend forming a first plate and a second plate, the second plate being angled to the first plate; wherein said heat exchanger has a multi-way configuration with respect to the air flow comprising at least a first stroke and a second stroke, wherein the first stroke has a first flow orientation and the second stroke has a second flow orientation, the second flow orientation being different from the first flow orientation, wherein said heat exchanger also contains a first separator located in the first collector to form a first section and a second section of a first collector; a second separator located in the second manifold with the formation of the first section and the second section of the second collector; a longitudinally elongated distributor located in the second section of the second manifold between the first stroke and the second stroke. 2. The heat exchanger according to claim 1, characterized in that the first stroke has a transversely parallel flow orientation. 3. The heat exchanger according to claim 2, characterized in that the second stroke has a cross-flow orientation. 4. The heat exchanger according to claim 1, characterized in that the first part of the plurality of tubular segments forms a first stroke, and the second part of the plurality of tubular segments forms a second stroke. 5. The heat exchanger according to claim 4, characterized in that the number of tubular segments located in each of the first stroke and the second stroke is selected to reduce the formation of frost on the heat exchanger. 6. The heat exchanger according to claim 4, characterized in that the second part has a greater number of tubular segments than the first part. 7. The heat exchanger according to claim 6, characterized in that the ratio of the tubular segments in the first part and in the second part is 20:80. 8. The heat exchanger according to claim 6, characterized in that the ratio of the tubular segments in the first part and in the second part is 40:60. 9. The heat exchanger according to claim 4, characterized in that the separator is located inside the first collector to form the first section and the second section, wherein the first section is hydraulically connected to the first part of the plurality of tubular segments, and the second section is hydraulically connected to the second part of the plurality of tubular segments. 10. The heat exchanger according to claim 9, characterized in that the distributor is located inside the first section of the first collector. 11. The heat exchanger according to claim 9, characterized in that the distributor is provided between the first stroke and the second stroke. 12. The heat exchanger according to claim 1, characterized in that the bend is made around an axis located perpendicular to the longitudinal axis of the plurality of tubular segments. 13. The heat exchanger according to claim 1, characterized in that the bend of each tubular segment contains a funnel fold of the tape. 14. The heat exchanger according to claim 1, characterized in that the angle between the second plate and the first plate is about 180 degrees. 15. The heat exchanger according to claim 1, characterized in that each of the plurality of tubular segments is a microchannel tube having a plurality of discrete flow channels formed therein. 16. A heat exchanger containing: first collector; a second collector separated from the first collector; a plurality of tubular segments spaced parallel to each other and hydraulically connecting the first collector and the second collector, the plurality of tubular segments comprising a bend forming a first plate and a second plate, the second plate being angled to the first plate; moreover, the heat exchanger has a multi-way configuration relative to the air flow, containing at least a first stroke and a second stroke, as well as the inlet pipe of the heat exchanger and the outlet pipe of the heat exchanger, both made in the first plate, wherein said heat exchanger also contains a first separator located in the first collector to form a first section and a second section of a first collector; a second separator located in the second manifold with the formation of the first section and the second section of the second collector; a longitudinally elongated distributor located in the second section of the second manifold between the first stroke and the second stroke. 17. The heat exchanger according to claim 16, characterized in that the first part of the plurality of tubular segments forms a first stroke, and the second part of the plurality of tubular segments forms a second stroke, the first part having fewer tubular segments than the second part. 18. The heat exchanger according to claim 16, characterized in that each of the plurality of tubular segments is a microchannel tube having a plurality of discrete flow channels formed therein. 19. The heat exchanger according to claim 16, characterized in that the distributor is located adjacent to the inlet pipe of each stroke of the heat exchanger.

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