Patent Application
20060144051
1. Field of the Invention
This invention relates to a heat exchanger for use in a vehicle climate control system. More specifically, the invention relates to an evaporator for transferring heat between a cross-flow of air through the evaporator and a refrigerant circulating within the evaporator.
2. Description of the Related Art
Various evaporator designs exist in the art that incorporate components for promoting heat exchange between a refrigerant fluid flowing within tubes and air flowing through fins that are disposed on the exterior surfaces of the tubes. The tubes typically incorporate features that force the refrigerant entering the evaporator to flow in a number of passes before it exits the evaporator. The evaporators often also include specific modifications to the interior surfaces of the tubes, which increase the surface area available for heat exchange between the ambient air and the fluid. For example, some evaporators are formed entirely of tubes having interior surfaces upon which interior fins are disposed. Other evaporators utilize tubes having interior surfaces from which “dimpled”, or “bumped”, protrusions extend into the interior (refrigerant side) of the evaporator.
While interior fins and “bumped” or “dimpled” surfaces increase heat exchange within the evaporator, limiting use of one or the other of the fins or dimples throughout all of the tubes in an evaporator is not necessarily the optimum way to maximize heat exchange. This is especially the case in climate control systems utilizing thermostatic expansion valves (“TXVs”). In a TXV system, the evaporator outlet superheat is normally set at about 15° F.; however, when a TXV system is under transient operation, the superheat can increase to 30° F. or more. This reduces cooling capacity and causes the temperature distribution of the discharge air to become more non-uniform.
Another problem with dimpled evaporators is that under certain transient vehicle operating conditions, vapor flowing over the dimples gives rise to a pure tone noise or “whistle” emanating from the evaporator. By providing fins inside the refrigerant tube plates in appropriate locations, as described in this invention, it is possible to eliminate this whistling transient noise.
The invention provides a laminate-type evaporator having first and second tanks and fabricated from a plurality of plates. Each plate has upstream and downstream side edges with an interior portion recessed relative thereto. The plates are disposed in pairs with the side edges of each pair in abutting engagement with one another and the interior portions defining a passageway between each pair. The pairs are spaced along the tanks in first and second groups, and the passageways are in fluid communication with the tanks for permitting a fluid to flow between the tanks through the passageways. A thermal energy exchange occurs between the fluid and a cross-flow of air through the first and second groups from the upstream to downstream side edges. Dimples extend from the interior portions into the passageways of the first group. Interior fins are disposed against the interior portions and extend to the upstream and downstream side edges, which enhances the thermal energy exchange between the fluid and the cross-flow of air between the upstream and downstream side edges of the second group of plates.
Disposing dimples on the first group of plates enhances the thermal energy exchange between the air and a first flow of the fluid passing from the upstream to downstream side edges of the first group of plates. The fins on the second group of plates enhance thermal energy exchange between the air and a second flow of fluid passing from the upstream to downstream side edges of the second group of plates independently and separately from the first flow of fluid.
The subject invention overcomes the limitations of the art by providing an evaporator which utilizes tubes having interior fins in combination with a separate, distinct group of tubes having interior surfaces upon which dimples are formed. The interior fins are utilized in those tubes which define the final refrigerant passes of the evaporator. Doing so reduces refrigerant side thermal resistance by providing increased refrigerant side surface area to compensate for the decrease in the refrigerant side heat transfer coefficient that often occurs in the last passes of evaporators, especially in those operating at high outlet superheats. Additionally, providing interior fins in the final refrigerant passes also improves the thermal contact between the air fins and the tubes, because the tubes in this region of the evaporator have no dimples. Thus, in the final evaporator passes, a higher overall heat transfer coefficient is achieved resulting from reduced thermal resistance on the refrigerant side and in the conduction path from the air fins to the tube. Tubes having dimples formed on the interior surfaces are utilized in the initial refrigerant passes on the upstream airside of the evaporator where high refrigerant side surface area is not critical to initiate heat exchange, because of the prevailing high refrigerant side heat transfer coefficients associated with low to medium vapor quality two-phase flow. Providing interior fins in the final refrigerant passes also eliminates the tonal noise or whistle originating in the evaporator under certain transient operating conditions. This is because high velocity refrigerant vapor flow over the dimples in the last passes is the cause of a phenomenon called acoustic resonance, which is perceptible as whistling. Combining different surface enhancements by providing them only where they are truly necessary reduces total evaporator mass, decreases manufacturing costs, eliminates transient whistling noise, and improves heat exchange efficiency and temperature uniformity and stability.
Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring now to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a laminate-type evaporator is generally shown at 10 in
Each of the plates 16 has upstream and downstream side edges 18, 20 with an interior portion 22 recessed relative thereto. As shown in
Referring now to
The evaporator 10 also includes a plurality of dimples 34 which extend from the interior portions 22 of the first group 28 of plates 16 into the passageways 26 for enhancing the thermal energy exchange between the fluid 32 and the cross-flow of air between the upstream and downstream side edges 18, 20. The thermal efficiency of the evaporator 10 is further improved by a plurality of interior fins 36. The fins 36 are disposed against the interior portions 22 of the second group of plates 30. As shown in
Disposing the dimples 34 on the first group 28 of plates 16 enhances the thermal energy exchange of air with the flow of the fluid 32 passing between the upstream and downstream side edges 18, 20 of the first group 28 of plates 16, while the fins 36 on the second group 30 of plates 16 enhance the thermal energy exchange of air with the flow of the fluid 32 passing through the second group of plates 30.
As is best shown in
The plates 16 include upper and lower side edges 40, 42 that interconnect the upstream and downstream side edges 18, 20. The upper tank 12 is disposed adjacent the upper edges 40, and the lower tank 14 is disposed adjacent the lower side edges 42. The tanks 12, 14 are in fluid communication with the passageways 26, which permits the fluid 32 to flow between the first and second groups 28, 30 of plates 16.
The evaporator 10 also includes exterior fins 48 which are disposed against the exterior surfaces of the adjacent pairs 24 of plates 16. The fins 48 extend from the upper tank 12 to the lower tank 14. Each exterior fin 48 has a plurality of folds 50. The folds 50 extend perpendicularly to the longitudinal axes 51 of the plates 16 between the upstream and downstream side edges 18, 20. The orientation of the folds 50 relative to the longitudinal axis 51 of each plate 16 maximizes the total surface area available on the exterior fins 48 for transferring thermal energy between the cross-flow of air and the fluid 32 as the air passes across the exterior fins 48 from the upstream to downstream side edges 18, 20 of the plates 16.
The evaporator 10 also has upstream or right and downstream or left endplates 52, 54. The upstream endplate 52 is disposed against that plate 16 which is located rightmost from the remaining plates 16 forming the first group 28. The right endplate 52 includes an inlet aperture 56. As is shown in
The left endplate 54 includes an outlet aperture 58, and is positioned against that plate 16 which is located leftmost from the rest of the plates 16 in the second group 30. Like the inlet aperture 56, the outlet aperture 58 is in axial alignment with the upper tank 12 for permitting the fluid 32 to exit the evaporator 10 after flowing through the plates 16 in the second group 30.
The evaporator 10 is configured in a manner that directs the fluid 32 through a plurality of passes through the passageways 26 and across the path of the cross-flow of air through the exterior fins 48. As is shown in
The blind 62 is disposed in the upper tank 12 within the tubular projection 38 of the first plate pair 24 positioned immediately downstream from the first group 28 of plates 16. Positioning the blind 62 in this location prevents the fluid 32 from flowing further to the left in the upper tank 12 past the blind 62, and instead diverts the fluid 32 to flow into the lower tank 14 through the plate pairs 24 of the third pass of the first group 28. From the lower tank 14, the fluid 32 then flows through the plate pairs 24 in the second group 30.
The evaporator 10 also utilizes upstream and intermediate flow separators 64, 66, which consist of blinds 68, 70 identical in shape and structure to the blind 62 described above with reference to the first flow separator 60. The blind 68 which forms the rightmost flow separator 64 is disposed within the upper tank 12 intermediate two of the plate pairs 24 that are located in the first group 28 a predetermined distance to the left of the inlet aperture 56.
The intermediate flow separator 66 is positioned within the first group 28 to the left of the rightmost flow separator 64. However, in contrast to the blind 68, the blind 70 forming the intermediate flow separator 66 is disposed within the lower tank 14 between a plate pair 24 located a predetermined distance to the right of the flow separator 60, and a plate pair 24 located a predetermined distance to the left of the upstream flow separator 64.
Although any number of flow separators may be utilized in the evaporator 10 to define flow path configurations with any number of passes, the rightmost, leftmost and intermediate flow separators 64, 60, 66 are utilized in combination with the upstream and downstream endplates 52, 54 to define four passes through the evaporator 10 in the particular case shown in
The fluid 32 continues to flow to the left through the lower tank 14 and is diverted through the passageways 26 located immediately between the intermediate blind 70 and the rightmost blind 68. The fluid 32 flows back into the upper tank 12, thus completing a second pass through the evaporator 10.
The fluid 32 completes a third pass through the first group 28 by flowing to the left through the upper tank 12 to the flow separator 60. The blind 62 defining the flow separator 60 causes the fluid 32 to flow through the passageways 26 of the selected group of the plate pairs 24 in the first group 28 positioned immediately upstream from the second group 30. The fluid 32 is diverted back into the second tank 14 and into the second group 30 of plates 16. The fluid 32 then makes a fourth, or final, pass from the second tank 14, through the passageways 26 and across the interior fins 36 of the plates 16 in the second group 30 prior to re-entering the upper tank 12 and exiting the evaporator 10 through the outlet aperture 58 located in the left end plate 54.
Referring now to
In contrast to the plates 16 utilized in the evaporator 10, the interior portions 122 of the plates 116 in both the first group 128 and the second group, generally shown at 130 in
As is shown in
While the exterior fins 148 are disposed against the exterior surfaces of the adjacent pairs 124 of plates 116, in contrast to the exterior fins 48 of the evaporator 10, the fins 148 extend from the first and second tanks 112, 114 to the lower edges 142 of the plates 116 adjacent the base 186.
The U-shaped channels 180 affect both the rate of heat exchange within the evaporator 110 and the location of the interior fins 136 and dimples 134 disposed within the passageways 126. As is shown in
Referring again to
The evaporator 110 utilizes right or upstream and left or downstream endplates 152, 154 which have respective inlet and outlet apertures 156, 158. The endplates 152, 154 are identically shaped. The right endplate 152 is disposed against that plate 116 which is located to the right of the remaining plates 116 that constitute the first plate group 128. The endplate 152 is disposed in abutting engagement with the aforementioned plate 116 with the inlet aperture 156 in axial alignment with the first tank 112. The left endplate 154 is similarly disposed against the plate 116 in the second group 130 which is located furthest to the left of the other plates 116 of the evaporator 110. The left endplate 154 is oriented in axial alignment with the first tank 112 with the outlet aperture 158 adjacent the side edge 118. As described in greater detail below, this allows the fluid 132 to exit the evaporator 110 after flowing through the passageways 126 in the second group 130.
The evaporator 110 utilizes right and left flow separators 164, 160 to direct the fluid 132 through a predetermined flow configuration within the evaporator 110. In order to accommodate the U-shaped configuration of the plates 116, the shape and components of the flow separators 160, 164 differ from those utilized in the evaporator 10. In particular, the left flow separator 160 includes a planar surface, or blind 194. The blind 194 covers a selected one of the tubular projections 138 in a single plate pair 124 positioned intermediate the first and second plate groups 128, 130. As is shown in
The upstream flow separator 164 includes a single blind 198, which covers a tubular projection 138 in a selected plate 116 in the first group 128. In particular, the blind 198 covers the projection 138 located adjacent the downstream side edge 120, which effectively blocks the portion of first tank 112 to the left of blind 198. The blind 198 diverts the fluid 132 to flow in a first pass through the U-shaped channels 180, over the dimples 134 and into the second tank 114. The fluid 132 continues flowing through the second tank 114 and encounters the other blind 194 in the second tank 114 and is then diverted to flow in a second pass through the U-shaped channels 180 of a selected plurality of plates 116 in the first group 128. These plates 116 are located immediately to the right of the second group 130. The fluid 132 then flows back into the first tank 112 and flows in a third, or final, pass through the second plate group 130 in the manner described above.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
