ES2831020T3 - Multi-pass, multi-plate folded microchannel heat exchanger - Google Patents

Abstract

A heat exchanger comprising: a first manifold (32); a second manifold (34) separate from the first manifold; a plurality of tube segments (36) arranged in a spaced parallel relationship and fluidly coupling the first manifold and second manifold, the plurality of tube segments including an elbow (60) defining a first plate (66) and a second plate (68), the second plate being arranged at an angle to the first plate; and a divider (38) disposed within the first manifold to form a first manifold section (32a) and a second manifold section (32b); and a divider disposed within the second manifold to form a first section (34a) of the second manifold and a second section (34b) of the second manifold; wherein the heat exchanger has a multi-pass configuration with respect to an air flow including at least a first pass and a second pass, the first pass including a first portion (36a) of the plurality of tube segments and having a first flow orientation and the second passage including a second part (36b) of the plurality of tube segments and having a second flow orientation, the second flow orientation being different from the first flow orientation, wherein several segments of tube in the first part and various tube segments in the second part are different; characterized in that a longitudinally elongated distributor insert (70) is disposed within the second section of the second manifold.

Description

DESCRIPTION

Multi-pass, multi-plate folded microchannel heat exchanger

The present invention generally relates to a heat exchanger for use in a heat pump or refrigeration system. Document EP 0654645 discloses a heat exchanger having the features of the preamble of claim 1.

Heating, cooling, air conditioning and refrigeration (HVAC & R) systems include heat exchangers to reject or accept heat between the refrigerant that is circulating within the system and its vicinity. One type of heat exchanger that has become increasingly popular due to its compactness, lighter weight, structural rigidity, and superior performance is a micro-channel or mini-channel heat exchanger. Compared to conventional plate and fin heat exchangers, microchannel heat exchangers are also more environmentally friendly as they use less refrigerant charge, which are usually synthetic fluids with high GWP (Global Warming Potential). . A microchannel heat exchanger includes two or more forms of containment, such as tubes, through which a cooling or heating fluid (ie, coolant or a glycol solution) circulates. The tubes usually have a flattened cross section and multiple parallel flow channels. The fins are typically arranged to extend between the tubes in order to increase the efficient exchange of thermal energy between the heating / cooling fluid and the surrounding environment. The fins have a wavy pattern, incorporate louvers to further enhance heat transfer, and are often attached to the tubes by controlled atmosphere welding.

In refrigeration and heat pump applications, when the microchannel heat exchanger is used as an evaporator, the moisture present in the air flow provided to the heat exchanger for cooling may condense and then freeze on the external surfaces of the heat exchanger. hot. The formed ice or frost can block air flow through the heat exchanger, thereby reducing the efficiency and functionality of the heat exchanger and the HVAC & R system. Microchannel heat exchangers tend to freeze faster than round tube and plate-and-fin heat exchangers and therefore require more frequent de-icing, reducing the uptime of the exchanger heat and overall performance. Consequently, it is desirable to manufacture the microchannel heat exchanger with improved tolerance to frost formation and improved performance.

According to a first aspect, the invention provides a heat exchanger comprising: a first manifold; a second collector separate from the first collector; a plurality of tube segments arranged in a spaced parallel relationship and fluidly coupling the first manifold and the second manifold, the plurality of tube segments including an elbow defining a first plate and a second plate, the second plate being arranged at an angle to the first plate; and a divider disposed within the first manifold to form a first manifold section and a second first manifold section; and a divider disposed within the second manifold to form a first second manifold section and a second second manifold section; wherein the heat exchanger has a multi-pass configuration with respect to an air flow including at least a first pass and a second pass, the first pass including a first part of the plurality of tube segments and having a first orientation and the second passage including a second part of the plurality of tube segments and having a second flow orientation, the second flow orientation being different from the first flow orientation, wherein several tube segments in the first part and several tube segments in the second part are different; characterized in that a longitudinally elongated distributor insert is disposed within the second section of the second manifold.

The first pass may have a transverse parallel flow orientation.

The second pass may have a cross flow orientation.

The number of tube segments arranged within each of the first pass and the second pass can be selected to reduce frost build-up in the heat exchanger.

The second part may have a greater number of tube segments than the first part.

A tube segment ratio between the first part and the second part can be 20:80.

A tube segment ratio between the first part and the second part can be 40:60.

A divider may be provided within the first manifold to define a first section of the first manifold and a second section of the first manifold, wherein the first section of the first manifold is fluidly coupled to the first part of the plurality of tube segments, and the second section of the first manifold is fluidly coupled to the second part of the plurality of tube segments.

A distributor may be arranged within the first section of the first manifold.

A distributor can be provided between the first step and the second step.

The elbow may be formed around an axis arranged perpendicular to a longitudinal axis of the plurality of tube segments.

The elbow of each tube segment may include a fold of tape.

The angle between the second plate and the first plate can be approximately 180 degrees.

Each of the plurality of tube segments may be a microchannel tube having a plurality of discrete flow channels formed therein.

The subject matter, considered by the present invention, is particularly pointed out and clearly claimed in the claims at the end of the specification. The above and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic diagram of an example of a steam refrigeration cycle of a refrigeration system;

Figure 2 is a side view of a microchannel heat exchanger according to an embodiment of the invention prior to a kinking operation;

Figure 3 is a cross-sectional view of a tube segment of a microchannel heat exchanger according to an embodiment of the invention;

Figure 4 is a perspective of a microchannel heat exchanger according to one embodiment of the invention;

Figure 5 is a front view of a microchannel heat exchanger according to another embodiment of the invention;

Figure 6 is a side view of a microchannel heat exchanger according to one embodiment of the invention; Figure 7 is a perspective view of a microchannel heat exchanger according to yet another embodiment of the invention; Y

Figure 7a is a cross-sectional view of the microchannel heat exchanger of Figure 6 taken along the line X-X in accordance with yet another embodiment of the invention; Y

Figure 7b is a cross-sectional view of the microchannel heat exchanger of Figure 6 taken along the Y-Y line in accordance with yet another embodiment of the invention.

The detailed description below explains embodiments of the invention, along with advantages and features, by way of example with reference to the drawings.

Referring now to FIG. 1, a vapor compression refrigerant cycle 20 of a refrigeration or air conditioning system is schematically illustrated. Illustrative air conditioning or refrigeration systems include, but are not limited to, for example, split, packaged, chiller, rooftop, supermarket, and transportation refrigeration systems. A refrigerant R is configured to circulate through the vapor compression cycle 20 so that the refrigerant R absorbs heat when it evaporates at low temperature and pressure and releases heat when it condenses at a higher temperature and pressure. Within this cycle 20, the refrigerant R flows in the left-hand direction as indicated by the arrow. Compressor 22 receives refrigerant vapor from evaporator 24 and compresses it to a higher temperature and pressure, then the relatively hot vapor passes to condenser 26, where it is cooled and condensed to a liquid state through a heat exchange relationship with a cooling medium (not shown) such as air. The liquid refrigerant R then passes from the condenser 26 to an expansion device 28, where the refrigerant R expands to a low-temperature liquid / vapor two-phase state as it passes to the evaporator 24. The low-pressure vapor then returns to the compressor 22, where the cycle is repeated. The vapor compression cycle 20 described herein is a heat pump cycle operating in a heating mode. As a result, the outdoor coil of cycle 20 is configured as an evaporator 24 and the indoor coil is configured as a condenser. When configured as a heat pump, the vapor compression cycle further includes a four-way valve 29 disposed downstream of compressor 22 with respect to refrigerant flow that reverses the direction of refrigerant flow through cycle 20 to switch between the cooling and heating mode of operation. It should be understood that the refrigeration cycle 20 depicted in Figure 1 is a simplistic representation of an HVAC & R system, and many enhancements and features known in the art can be included in the schematic.

Referring now to Figure 2, an example of a heat exchanger 30 configured for use in the vapor compression system 20 is illustrated in more detail. Heat exchanger 30 may be used as a condenser 24 or as an evaporator 28 in the vapor compression system 20. Heat exchanger 30 includes at least a first manifold or manifold 32, a second manifold or manifold 34 separate from the first manifold 32, and a plurality of tube segments 36 extending in parallel spaced relationship between the first manifold 32 and the second manifold 34, connecting them. In the illustrated and non-limiting embodiments, the first manifold 32 and the second manifold 34 are oriented generally horizontally and the segments 36 of the heat exchange tube extend generally vertically between the two manifolds 32, 34. However, other configurations, for example when the first and second headers 32, 34 are arranged substantially vertically are also within the scope of the invention.

Referring now to Figure 3, an example of a cross section of a heat exchange tube segment 36 is illustrated. Tube segment 36 includes a flattened microchannel heat exchange 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 upstream of its respective trailing edge 42 with respect to an air flow A passing through the heat exchanger. heat 36. The interior flow passage of each heat exchange tube segment 36 may be divided by interior walls into a plurality of discrete flow channels 48 which extend along tubes 36 from an inlet end to a outlet end and establish fluid communication between the respective first and second manifolds 32, 34. The flow channels 48 may have a circular cross section, a cross section rectangular salt, a trapezoidal cross section, a triangular cross section or other non-circular cross section. Heat exchange tubes 36 that include discrete flow channels 48 can be formed using known techniques and materials, including, but not limited to, extrusion or folding.

The heat exchange tube segments 36 described herein further include a plurality of fins 50. In one embodiment, the fins 50 are formed of a single continuous strip of fin material tightly folded into a serpentine tape shape. , thereby providing a plurality of closely spaced fins that extend generally orthogonally to the heat exchange tube segments 36. The heat exchange between one or more fluids within the heat exchange tube segments 36 and an air flow, A, takes place through the outer surfaces 44, 46 of the heat exchange tube segments 36 which together form a primary heat exchange surface, and also through the heat exchange surface fins 50, which forms a secondary heat exchange surface.

Heat exchanger 30 has a multi-pass configuration relative to air flow A. To achieve a multi-pass configuration, in one embodiment illustrated in Figures 4-6, the multi-pass configuration is achieved by forming at least one elbow 60 in each tube segment 36 of heat exchanger 30. Elbow 60 is formed around an axis that extends substantially perpendicular to the longitudinal axis of tube segments 36. In the illustrated embodiment, elbow 60 is a pleat. tape (see FIG. 6) formed by folding and twisting the heat exchange tube segments 36 around a mandrel (not shown); however, other types of pleats are within the scope of the invention. In one embodiment, a plurality of elbows 60 may be formed at various locations along the plurality of heat exchange tube segments 36.

Elbow 60 at least partially defines a first section 62 and a second section 64 of each of the plurality of tube segments 36, wherein, in the folded configuration, the first section 62 forms a first plate 66 of the heat exchanger 30 with respect to air flow A and second section 64 forms a second plate 68 of heat exchanger 30 with respect to air flow A. In the illustrated non-limiting embodiment, elbow 60 is formed at an approximate midpoint of the segments of tube 36 between the opposite first and second manifolds 32, 34, so that the first and second sections 62, 64 are generally the same size. However, other embodiments in which the first section 62 and the second section 64 have a substantially different length are within the scope of the invention.

As shown in the figures, the heat exchanger 30 can be formed so that the first plate 66 is positioned at an obtuse angle with respect to the second plate 68. Alternatively, or additionally, the heat exchanger 30 also may be formed so that the first plate 66 is arranged at an acute angle or substantially parallel (FIG. 5) to the second plate 68. As a result of the elbow 60 between the first and second plates 66, 68, the heat exchanger 30 can be formed with a conventional A-coil or V-coil shape. Forming the heat exchanger 30 by folding the tube segments 36 results in a heat exchanger 30 having a reduced bend radius, as when configured with a 180 ° elbow, for example. As a result, the heat exchanger 30 can be adapted to fit within the size envelopes defined by existing refrigeration and air conditioning systems.

Referring again to Figure 2, a plurality of first fins 50a extend from first plate 66 and a plurality of second fins 50b extend from second plate 68 of heat exchanger 30. In embodiments in which the heat exchanger 30 is formed by folding the plurality of tube segments 36, there are no fins disposed within the elbow portion 60 of each tube segment 36. The first fins 50a and the second fins 50b may be substantially identical or, alternatively, may vary as for its size, its shape or its density.

Conventional heat exchangers configured as heat pump evaporators typically have a parallel flow configuration to achieve the desired efficiency. However, the parallel flow orientation leads to poor tolerance to frost formation in microchannel heat exchangers. Heat exchanger 30 can have any of a variety of multi-pass configurations such that refrigerant passes through heat exchanger 30 in one or more of a parallel flow orientation, a cross flow orientation, and a counter flow orientation. , for example. In one embodiment, a divider 38 may be provided within both or one of the first and second manifolds 32, 34 to increase the number of passages, and thus the length of the flow path, within the heat exchanger 30. .

In the embodiment illustrated in Figure 7, a divider 38 is disposed within the first manifold 32 to form a first section 32a and a second section 32b. As a result, the refrigerant supplied to an inlet (not shown) of the first manifold 32 is only configured to flow through the portion 36a of the tube segments 36 fluidly connected to the first section 32a. After passing through a first part 36a of the tube segments 36, the refrigerant is received in the second manifold 34. Inside the second manifold 34, the refrigerant flows from the first part 36a of the tube segments 36, towards a second part adjacent 36b of tube segments 36. Second part 36b includes a different number of tube segments 36 than first part 36a. In one embodiment, the tube segment ratio between the first part 36a and the second part 36b is 20:80 or, alternatively, 40:60.

The second manifold 34 may similarly include a divider 38 to define first and second sections 34a, 34b thereof fluidly coupled. The refrigerant is configured to flow from the second manifold 34 through the second portion 36b of fluidly connected tube segments 36 to the second section 32b of the first manifold 32 and to an outlet (not shown) formed therein. Although the illustrated heat exchanger 30 includes two distinct parts of heat exchanger tube segments 36, heat exchangers 30 having any number of tube segment parts 36 that form discrete passageways through heat exchanger 30 meet within the scope of the invention.

Evenly distributing the refrigerant within a manifold, like manifold 32 or 34 or an intermediate manifold, for example, is a common problem with microchannel heat exchangers. In general, it is easy to distribute the coolant evenly for short collector lengths, but maldistribution becomes a more significant problem as the collector length increases.

The heat exchanger 30 described herein has an improved refrigerant distribution by dividing at least one of the first and second manifolds 32, 34, with a divider 38. As a result, the lengths of the manifold in which the refrigerant it should be evenly distributed. Additionally, by collapsing the heat exchanger 30, the need for an intermediate manifold and thus the distribution problems associated with such a manifold are eliminated. In one embodiment, a longitudinally elongated distributor insert 70, as is known in the art, is positioned within the second section 34b of the second head 34. Another distributor 70 may be disposed within one or more of the sections of the first manifold. 32 or from the second manifold 34 of the heat exchanger 30. The distributor insert 70 is disposed generally centrally within the interior volume of the manifold and is configured to evenly distribute the flow of refrigerant among the plurality of heat exchange tubes 36 coupled from fluidly to it. In the illustrated non-limiting embodiment, a first distributor insert 70 is disposed within the first section 32a of the manifold 32. The distributor insert 70 disposed within the first section 32 of the first manifold 30 is generally over a portion or the entire length of section 32, so that the refrigerant provided thereto is more evenly distributed over the length of the first section 32, thereby improving heat transfer from heat exchanger 30.

Because the air flow direction A is the same with respect to the first and second parts 36a, 36b of the tube segments 36, the refrigerant within each of these parts has a different flow orientation. For example, in the illustrated non-limiting embodiment, air A flows from the first manifold 32 to the second manifold 34. By supplying the refrigerant to an inlet of the first section 32a of the first manifold 32, the refrigerant flows through the The first part 36a of the tube segments 36, shown in detail in Figure 7a, has a transverse parallel flow orientation. Additionally, the refrigerant flowing through the second portion 36b of the tube segments 36, shown in more detail in Figure 7b, has a transverse counterflow orientation.

In conventional heat exchangers having a parallel flow configuration, the two-phase refrigerant enters the first section 32 with a low vapor quality where it is configured to absorb heat from the air A and begins to boil. Because boiling takes place at a constant temperature, the temperature difference between the air and the refrigerant progressively reduces as the air flows through the heat exchanger 30, which reduces the heat transfer produced, particularly in the downstream plate 68. This behavior reduces the overall effectiveness of the heat exchanger and also results in lower evaporation temperatures, which is detrimental to both system efficiency and tolerance to heat. frost formation.

By dividing the plurality of heat exchange tube segments 36 of a heat exchanger 30 configured as an evaporator into a first part 36a and a second part 36b to form two sequential passages, the partially evaporated refrigerant is supplied from the first passage to the second step. In the second step, the refrigerant is fully boiled and the superheated vapor comes out of the upstream face of the heat exchanger 30. By setting the second step to have a refrigerant flow as opposed to air flow A, the temperature difference between air and refrigerant is favorable. Additionally, the presence of superheated steam on the upstream face of heat exchanger 30 prevents excessive frost build-up and improves tolerance to frost formation.

A heat exchanger 30 having a multi-pass, multi-plate, and pleated construction allows the pressure drop of the refrigerant to be optimized, thereby improving performance. As the refrigerant flows through the heat exchange tube segments 36, the quality of the vapor continuously increases, leading to an increase in volumetric flow and thus a greater pressure drop. By allocating a progressively larger internal flow area as the refrigerant moves from one step to the next, it is possible to greatly improve the pressure drop performance compared to conventional heat exchangers. The improvement in the operational efficiency of the heat exchanger 30 may allow the size of the heat exchanger 30 required for a desired application to be reduced. Alternatively, other system components can be downsized, such as a compressor for example, which in turn would lead to an even higher evaporation temperature and further reduction in de-frost cycles, as well as an increase in the system performance.

Although the present invention has been shown and described particularly with reference to the illustrative embodiments illustrated in the drawings, those skilled in the art will recognize that various modifications can be made without departing from the scope of the invention defined in the claims. Therefore, it is intended that the present disclosure is not limited to the one or more particular disclosed embodiments, but that the disclosure includes all embodiments that are within the scope of the appended claims. In particular, similar principles and relationships can be extended to rooftop applications and vertical package units.

Claims (14)

1. A heat exchanger comprising: a first manifold (32); a second manifold (34) separate from the first manifold; a plurality of tube segments (36) arranged in a spaced parallel relationship and fluidly coupling the first manifold and second manifold, the plurality of tube segments including an elbow (60) defining a first plate (66) and a second plate (68), the second plate being arranged at an angle to the first plate; Y a divider (38) disposed within the first manifold to form a first manifold section (32a) and a second manifold section (32b); Y a divider disposed within the second manifold to form a first section (34a) of the second manifold and a second section (34b) of the second manifold; wherein the heat exchanger has a multi-pass configuration with respect to an air flow including at least a first pass and a second pass, the first pass including a first portion (36a) of the plurality of tube segments and having a first flow orientation and the second passage including a second part (36b) of the plurality of tube segments and having a second flow orientation, the second flow orientation being different from the first flow orientation, wherein several segments of tube in the first part and various tube segments in the second part are different; characterized in that a longitudinally elongated distributor insert (70) is disposed within the second section of the second manifold. The heat exchanger according to claim 1, wherein the first passage has a transverse parallel flow orientation. The heat exchanger according to claim 2, wherein the second passage has a transverse counterflow orientation. The heat exchanger according to any preceding claim, wherein a number of tube segments (36) disposed within each of the first passage and the second passage are selected to reduce frost formation on the heat exchanger. The heat exchanger according to any preceding claim, wherein the second part (36b) has a greater number of tube segments (36) than the first part (36a). The heat exchanger according to claim 5, wherein a tube segment ratio (36) between the first part (36a) and the second part (36b) is 20:80. The heat exchanger according to claim 5, wherein a tube segment ratio (36) between the first part (36a) and the second part (36b) is 40:60. The heat exchanger according to any preceding claim, wherein a divider (38) is arranged within the first manifold (32) to define a first section (32a) of the first manifold and a second section (32b) of the first manifold. , the first section of the first manifold being fluidly coupled to the first part (36a) of the plurality of tube segments (36), and the second section of the first manifold being fluidly coupled to the second part (36b) of the plurality of tube segments. The heat exchanger according to claim 8, wherein a distributor (70) is arranged within the first section (32a) of the first manifold. The heat exchanger according to claim 8, wherein a distributor (70) is provided between the first pass and the second pass. The heat exchanger according to claim 1, wherein the elbow (60) is formed around an axis arranged perpendicular to a longitudinal axis of the plurality of tube segments (36). The heat exchanger according to claim 1, wherein the elbow (60) of each tube segment (36) includes a ribbon pleat. The heat exchanger according to claim 1, wherein the angle between the second plate (68) and the first plate (66) is approximately 180 degrees. The heat exchanger according to claim 1, wherein each of the plurality of tube segments (36) is a microchannel tube having a plurality of discrete flow channels (48) formed therein.