Hybrid evaporator

A laminate-type evaporator includes U-channel plates in combination with various configurations of dual cup and single cup plates, to control refrigerant pressure drop and achieve enhanced temperature spreads within the evaporator. The U-channel plates define one or more of the final refrigerant passes in the evaporator, and the dual cup and single cup plates define refrigerant passes upstream therefrom. Fins are disposed between adjacent plate pairs and extend to selected end edges of the U-channel plates to maximize the surface area available for heat exchange in the final refrigerant passes.

FIELD OF THE INVENTION

This invention relates to a heat exchanger, and more particularly, to an evaporator for the climate control system of a motor vehicle.

DESCRIPTION OF THE RELATED ART

Evaporators are well known in the art, and typically include a plurality of tubes having interiors through which refrigerant flows. Thermal energy, or heat, exchange occurs between ambient air flowing outside the tubes and the refrigerant flowing within. To enhance the amount of heat exchanged between the air and refrigerant, multiple fins are disposed between the adjacently positioned tubes. The fins are placed in contact with selected exterior surfaces of the tubes. This increases the surface area available for heat transfer from the air to the refrigerant circulating within the tubes, which in turn cools and dehumidifies the air as it flows across the exterior of the evaporator.

Heat transfer from the air to the refrigerant is further enhanced by routing the refrigerant to flow through the tubes so that it makes multiple passes through the interior passages of the tubes as air flows across the finned exterior. Unfortunately, because the refrigerant absorbs heat from the air, the cooling capacity of the refrigerant decreases with each additional pass the refrigerant makes. Thus, the air flowing across those tubes which form the initial passes of refrigerant is cooled to a greater extent and more efficiently than the air which flows across those tubes located further downstream and included in the latter passes. This inconsistency in heat exchange between the initial and latter refrigerant passes manifests itself as a non-uniform temperature distribution of the air leaving the evaporator and entering the passenger compartment (referred to as “temperature spreads”).

The problem of non-uniform temperature of the discharge air is further exacerbated by the manner in which an evaporator core is designed. For example, in those evaporators fabricated from single cup, full plate tube plates only, high cooling capacity is achieved at the expense of large temperature spreads under certain operating conditions. For instance, non-uniform air temperature distribution occurs in such evaporators when a vehicle in which the evaporator is installed accelerates from rest. In this situation, the compressor of the climate control system quickly draws refrigerant out of the evaporator, causing high refrigerant superheats to occur within the last passes of the evaporator. Evaporators formed from U-channel tubes achieve temperature spreads which are more uniform than those achieved by single cup, full plates. However, the cooling capacity of such tubes is compromised by the increased pressure drop that occurs on the refrigerant side of the tubes, which is caused by the reduced cross-sectional area of the tubes available for refrigerant flow.

Although evaporators that utilize dual cup tubes to effectively create two cores through which the refrigerant flows in series first through one core and then the other achieve improved temperature spreads and greater cooling capacity than evaporators formed from U-channel tubes, increasing movement towards evaporator cores with smaller depths, necessitated by space constraints, has eroded these benefits. The smaller the core depth, the narrower the cross-sectional area of the tubes through which the refrigerant must flow, and the greater the refrigerant pressure drop, which has a negative impact on the cooling capacity of the evaporator core.

BRIEF SUMMARY OF THE INVENTION AND ADVANTAGES

The invention provides a laminate-type evaporator having a plurality of first plates stacked together in adjacent pairs. Each plate includes first and second tubular projections and a first recess. The plates are positioned in abutting engagement with one another such that the first tubular projections define a first tank, the second tubular projections define a second tank, and the first recesses define a plurality of initial passageways interconnecting the first and second tanks in fluid communication therewith.

The evaporator also includes a plurality of second plates stacked together in adjacent pairs. Each of the second plates extend between opposed end edges and include third and fourth tubular projections, as well as a pair of elongate recesses. The elongate recesses extend parallel to one another and are interconnected by a return recess disposed adjacent one of the end edges. Adjacent pairs of the second plates are in abutting engagement with one another such that the third tubular projections define a third tank positioned downstream from the second tank, the fourth tubular projections define a fourth tank, and the return and parallel recesses define a plurality of U-shaped passageways. The U-shaped passageways interconnect the third and fourth tanks, which permits a fluid refrigerant to enter the first tank and flow in an upstream to downstream direction through the initial passageways and the second tank, into the third tank, and through the U-shaped passageways prior to exiting the fourth tank.

Fins are disposed between the adjacent pairs of plates. Those fins disposed between adjacent pairs of the second plates are positioned in overlying relation to the return recesses and extend to the upper edges adjacent thereto for inducing a transfer of thermal energy between an airflow through the fins and the fluid flowing through the return recesses.

The subject invention overcomes the limitations of the art by providing an evaporator which utilizes U-channel plates in combination with various configurations of dual cup and single cup plates. The U-channel plates are utilized to define one or more of the final refrigerant passes in the evaporator, which aids in the distribution of the small quantity of liquid refrigerant that typically remains in those passes as the refrigerant vaporizes and its quality approaches unity. The dual and single cup plates are utilized in passes upstream from the U-channel plates to reduce the drop in pressure that would otherwise occur on the refrigerant side if U-channel plates were used throughout the evaporator. Extending the fins to the upper edges of the U-channel plates maximizes the surface area of the plates available for heat exchange in the final refrigerant passes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a laminate-type evaporator is generally shown at20inFIGS. 1 through 3. The evaporator20includes a plurality of first tube plates22(dual cup tube plates) stacked together in adjacent pairs24. As is best shown inFIG. 4, each first plate22includes first and second tubular projections26,28and a first recess30. The first plate22also has an exterior surface32. The first recess30extends between the first and second tubular projections26,28. The first and second tubular projections26,28define respective apertures34,36through the plate22. The projections26,28also extend from the plate22in the same direction as the first recess30.

Referring toFIGS. 1 and 2, the adjacent pairs24are positioned in abutting engagement with one another such that the first tubular projections26define a first tank38and the second tubular projections28define a second tank40. As is shown inFIG. 5, the first recesses30define a plurality of initial passageways42. The initial passageways42interconnect the first and second tanks38,40and are in fluid communication therewith.

Referring again toFIG. 1, the evaporator20also includes a plurality of second tube plates44(U-channel tube plates). Like the first plates22, the second plates44are stacked together in adjacent pairs46. However, as is shown inFIG. 7, each of the second plates44extend between opposed end edges48and include third and fourth tubular projections52,54. The third and fourth projections52,54are positioned adjacent the lower edge48and define respective apertures56,58. A pair of elongate recesses60extends parallel to one another and are interconnected by a return recess62positioned adjacent one of the end edges48. Each elongate recess60extends from an upper end64to a lower end66, with the return recess62interconnecting the upper ends64. Each of the lower ends66is in fluid communication with a selected one of the apertures56,58.

Referring again toFIG. 2, the adjacent pairs46of second plates44are positioned in abutting engagement with one another with the third tubular projections52defining a third tank68. The third tank68is positioned downstream from the second tank40and is in fluid communication therewith. The fourth tubular projections54define a fourth tank70, and the elongate and return recesses60,62define a plurality of U-shaped passageways72. The passageways72interconnect the third and fourth tanks68,70, which in turn permits a fluid, or fluid stream,74to enter the first tank38, and then flow in an upstream to downstream direction “D” through the initial passageways42and second tank40, into the third tank68, and through the U-shaped passageways72prior to exiting the fourth tank70. The flow from tank70, as more fully described herein after, flows t the fifth tank92via the separator plates107.

Although not shown for clarity the various plates typically include bumps, dimples, fins, or the like, to project into the flow in the u-shaped passageways to control flow and/or enhance heat transfer. Any combination of such flow control devices may be employed in the subject invention.

Referring again toFIG. 1, the evaporator20also includes a plurality of fins76, which are disposed between adjacent pairs24,46of the plates22,44. In particular, each fin76is interposed between a selected pair of the first plate pairs24or a selected pair of the second plate pairs46. As is best shown inFIG. 3, those fins76interposed between adjacent pairs46of the second plates44are positioned in overlying relation to the return recesses62and extend to the upper edges48adjacent thereto, which in turn induces a transfer of thermal energy between an airflow78flowing through the fins76and the fluid stream74flowing through the return recesses62. The airflow78travels through the fins76from an downstream airside80to a upstream airside79of the evaporator20.

Although those fins76that are interposed between the adjacent pairs24of first plates22are capable of inducing a transfer of thermal energy between the airflow78passing through the fins76and the fluid stream74as it flows through the initial passageways30, the surface area on the plates22that is actually available for heat exchange is reduced by the presence of the first and second tanks38,40at the respective ends of the plates22. As is shown inFIG. 1, the surface area of the fins76and passageways30is limited to that which is located between the first and second tanks38,40. In contrast, the third and fourth tanks68,70are disposed adjacent those end edges48located adjacent the lower ends66of the elongate recesses60on the second plates44, which allows the return recesses62within the plates44and the fins76disposed against the exterior thereof to extend to the end edges48opposite the tanks68,70This increases the total air side and refrigerant side surface area available for heat transfer in a portion of the heat exchanger where the fluid stream74has higher vapor quality than at the inlet of the evaporator and this helps to maximize heat exchange between air and refrigerant.

Referring again toFIG. 4, each first plate22also includes fifth and sixth tubular projections82,84. A second recess86extends parallel to the first recess30between the fifth and sixth tubular projections82,84. The fifth and sixth tubular projections82,84define respective apertures88,90through the plate22, and the second recess86interconnects and is in fluid communication with the apertures88,90. As is shown inFIG. 2, the fifth tubular projections82define a fifth tank92positioned downstream from the fourth tank70and the sixth tubular projections84define a sixth tank94. The second recesses86define a plurality of final passageways96that interconnect the fifth and sixth tanks92,94and are in fluid communication therewith. Furthermore, the fifth tank92is in fluid communication with the fourth tank70, which allows the fluid stream74to flow from the fourth tank70into the fifth tank92. As is best shown inFIG. 6, the fluid stream74then flows through the final passageways96and into the sixth tank94.

Referring again toFIG. 1, the evaporator20also includes first and second end plates98,100. Each end plate98,100has upper and lower edges101,102. The first end plate98is disposed against the first plates22upstream therefrom and includes an inlet103and an outlet104that are axially aligned with the first tank38and sixth tank94, respectively. As is shown inFIG. 3, the fluid stream74enters the evaporator20through the inlet103and exits through the outlet104. The second end plate100is disposed against the second plates44downstream from the third tank68, and directs the fluid stream74to flow from the third tank68, through the U-shaped passageways72and into the fourth tank70.

The evaporator20also has a first flow separator106. The separator106is disposed between the first and second plates22,44for directing the fluid stream74to flow from the first plates22to the second plates44. As is best shown inFIG. 2, the first flow separator106is fabricated from a pair of first separator plates107. Each separator plate107has an exterior surface108disposed in a back-to-back relationship relative to the exterior surface108of the other separator plate107. A fin109is disposed between the exterior surfaces108, and is fabricated from the same materials as the fins76.

Referring now toFIG. 8, one of the first separator plates107is shown. The separator plate107has opposed end edges110and elongate side edges111. A first pair of projections112extends from the first separator plate107adjacent one of the end edges110. A second pair of projections113extends from the plate107adjacent the other end edge110. Recessed portions114extend parallel to one another between the first and second pairs of projections112and113. The portions114are recessed relative to the end edges110and side edges111, and protrude from the exterior surface108in the same direction as the first and second pairs of projections112,113.

Each of the second pair of projections113includes an aperture115; however, only one of the first pair of projections112has an aperture115. The other projection112has a cylindrical sidewall116that extends to an upper edge117. A planar face118likewise extends to the upper edge117.

Referring again toFIG. 2, when the exterior surfaces108are disposed back-to-back relative to one another, the first pairs of projections112engage one another so that the planar face118on each separator plate107covers the aperture115defined by the projection112extending from the other plate107. This prevents the fluid stream74from flowing downstream past the first flow separator106as the stream74exits the first tank38, and instead diverts the fluid stream74through the initial passageways42into the second tank40. The fluid stream74then exits through the aperture115on the downstream airside79of the evaporator20and flows into the third tank68and through the second plates44. Upon returning from the fourth tank70through the aperture115on the upstream airside80, the fluid stream74flows through the fifth tank92and the final passageways96, encounters the end plate98, and is directed to flow into the sixth tank94prior to exiting the evaporator20through the outlet104. The planar face118positioned on the flow separator106on the upstream airside80prevents the fluid stream74in tank94from flowing beyond the flow separator106and back into the flow passages72of the plates44.

Referring now toFIG. 9, a laminate-type evaporator according to an alternative embodiment of the invention is generally shown at120. The evaporator120includes first plates122, second plates144, fins176,209and a first flow separator206which are fabricated from the same materials, include the same components and are interconnected in the same manner as the first plates22, second plates44, fins76,109and first flow separator106, respectively, of the evaporator20. However, unlike the evaporator20, the evaporator120also includes a plurality of third plates222stacked together in adjacent pairs224. In addition, instead of having an outlet formed in the first end plate198, a fluid outlet227, is positioned downstream from the sixth tank194and is in fluid communication therewith

Referring now toFIG. 10, one of the third plates222is shown. The third plate222includes upper and lower tubular projections226,228and an elongate recessed portion230. The first tubular projections226define a pair of upper apertures234, and the second tubular projections228define a pair of lower apertures236. The elongate recessed portion230extends between the upper and lower tubular projections226,228. As is shown inFIG. 10, the recessed portion230and upper and lower tubular projections226,228extend in the same direction from an exterior surface231of the third plate222.

Referring again toFIG. 9, adjacent pairs224of the third plates222are in abutting engagement with one another. The first tubular projections226define at least one, or as shown, two upper tanks238and the second tubular projections228define at least one, or as shown, two lower tanks240. The upper and lower tanks238,240are positioned upstream from the first tank138.

The elongate recessed portions230define a plurality of fluid passageways246that interconnect the upper and lower tanks238,240. The passageways246are in fluid communication with the upper and lower tanks238,240, which allows the fluid stream174to flow through the fluid passageways246between the upper and lower tanks238,240prior to entering the first tank138and flowing through the evaporator120along a fluid pathway identical to that which is described above regarding the fluid stream74which flows through the evaporator20.

Like the first flow separator106of the evaporator20, the first flow separator206of the evaporator120is disposed intermediate the first and second plates122,144for directing the fluid stream174to flow from the first plates122to the second plates144. A second flow separator248is interposed between the first and third plates122,222for directing the fluid stream174to flow from the upper tanks242in the third plates270into the first tank138.

Unlike the first flow separator206, which is formed from a pair of first separator plates207identical to the first separator plates107described above with reference toFIG. 8, the second flow separator248is formed from a first separator plate207and a second separator plate250.

Referring now toFIG. 11, the second separator plate250has interior and exterior surfaces252,254and opposed end edges256interconnected by elongate side edges258. Projections260extend from the exterior surface254. Each projection260is positioned adjacent a selected one of the end edges256. An elongate recessed portion262extends between the projections260. The recessed portion262is recessed relative to the interior surface252and extends from the exterior surface254in the same direction as the projections260.

Like the upper tubular projections226on the third plates222, one of the projections260has an upper surface264defining a pair of apertures266. In contrast, the other projection260has an upper surface264defining a single aperture266located adjacent a planar area268.

Referring now toFIG. 12, the first separator plate207is shown. With the exception of one of the second pair of projections213including a second planar face219instead of an aperture215, the first separator plate207is identical to the first separator plate107described above with reference toFIG. 8.

Referring again toFIG. 9, the second flow separator248includes a lower diverting portion270, which is disposed in the lower tanks244for directing the fluid stream274to flow therefrom into the upper tanks242, and an upper diverting portion272, which is disposed in the upper tank242intermediate the first and third plates122,222for directing the fluid stream174to flow from the third plates222into the first tank138. In addition, a final diverting portion274is disposed in the upper tank242adjacent the sixth tank194for directing the fluid stream174to flow from the sixth tank194into the fluid outlet227.

The lower, upper and final diverting portions270,272,274of the second flow separator206are formed by disposing the first separator plate207against the second separator plate250so that the exterior surfaces208,254are in a back-to-back relationship relative to one another. The planar face219on the first separator plate207covers the single aperture266on the second separator plate250and the planar area268is disposed over the aperture215located adjacent the planar face219to define the lower diverting portion270. The upper and final diverting portions272,274are formed by positioning the planar face218of the first separator plate207over one of the apertures266located adjacent the end edge256on the second separator plate250.

Although not required, the evaporator120also includes an upstream flow separator276. As is shown inFIG. 9, the upstream flow separator276is disposed between two of the adjacent pairs224of third plates222for directing the fluid stream174to flow from the upper tanks242to the lower tanks244. The separator276is formed using a pair of the second separator plates250. The second separator plates250are disposed with the exterior surfaces254positioned in a back-to-back relationship with one another so that the planar area268on each plate250covers the single aperture266on the other plate250. The upstream flow separator276is then positioned between the selected adjacent pairs224of third plates222and oriented so that the planar areas268are disposed within the upper tanks242, which in turn diverts the fluid stream174into the lower tanks244.

Referring now toFIG. 13, an evaporator according to another alternative embodiment of the invention is generally shown at320. The evaporator320includes a plurality of first plates322stacked together in adjacent pairs324. The first plates322are fabricated in the same manner and include the same components as the third plates222of the evaporator120and described above with reference toFIG. 10. However, in contrast to the third plates222, which are used in combination with the first and second plates122;144in the evaporator120, the first plates322are combined solely with the second plates344in the evaporator320.

The evaporator320also includes a plurality of second plates344which are likewise stacked together in adjacent pairs346. Although the second plates344include the same components as the second plates44,144, the second plates344are oriented within the evaporator320in a different manner than that of the second plates44,144. As is shown inFIG. 13, the evaporator320features a first end plate398identical in structure and function to the first end plate198utilized in the evaporator120. However, unlike the second end plate200of the evaporator120, the second end plate400includes an outlet404and is disposed against the second plates344downstream from the upstream tank368, with the outlet404aligned with the downstream tank370to permit the vaporized fluid stream374to exit therethrough.

The second plates344are positioned so that the third368and fourth370tanks are disposed adjacent the upper edge401of the end plate400and the return recesses362are disposed adjacent the lower edge402. This differs from the second plates44,144, which are oriented within the evaporators20,120so that the third and fourth tanks68,70,168,170are adjacent the lower edge102,202, and the return recesses62,162are adjacent the upper edge101,201.

As is shown inFIG. 13, the projections352,354define respective upstream and downstream tanks368,370which are in fluid communication with the lower ends364of the elongate recesses360. The return recesses362interconnect the upper ends366, which in turn defines a plurality of U-shaped passageways372. The passageways372interconnect the upstream and downstream tanks368,370, which in turn permits the fluid stream374to enter the upstream tank368, and flow through the U-shaped passageways372prior to exiting the downstream tank370. Orienting the second plates344in this manner permits the U-shaped passageways372to be utilized in the final refrigerant pass without requiring that the fluid stream374be directed back toward the first plates322prior to exiting the evaporator320.

The evaporator320also includes a plurality of fins376disposed between the adjacent plate pairs324,346. Those fins376which are disposed between the adjacent pairs346of second plates344extend to the lower edges348. The increased surface area of the fins376provides the same advantages as that of the fins76described above with reference toFIG. 3. Specifically, the increased surface area permits a thermal energy exchange between the airflow378flowing through the fins376and the fluid stream374as it flows through the return recesses362. This maximizes heat transfer from the airflow378to the fluid stream374and improves the discharge air temperature uniformity of the evaporator320.

A downstream flow separator448is interposed between the first and second plates322,344for directing the fluid stream374to flow from the upper tanks342into the upstream tank368. The downstream flow separator448is formed from a pair of separator plates450(line one shown inFIG. 11but without the apertures266i.e., blocked) having projections460disposed against one another to define lower, upper and final diverting portions470,472,474that function in a manner identical to that of the slow separators described above. In essence, the respective flow paths defined by the second flow separator248and downstream flow separator448are identical. An upstream flow separator476is disposed between two of the adjacent pairs324of first plates322. The upstream flow separator476is fabricated using the same components and functions in the same manner as the upstream flow separator276utilized in the evaporator120and described above with reference toFIGS. 9 and 11.