Stacked heat exchanger

Abstract: The stacked heat exchanger (85) has a structure wherein grooves (46) are brazed together to seal the external surface of the coolant passage, further grooves (47) are brazed together to form a partition between the straight incoming and outgoing flow passages, and least one groove (67) in the straight incoming and outgoing flow passage section which groove runs in parallel with the grooves (46,47) earlier mentioned is formed on the formed plates. With this structure, drain water flows down promptly through these grooves (46,47,67) and the splashing of the drain water into the downstream area of the heat exchanger (85) can be prevented.

Description: The invention refers to a stacked heat exchanger, in particular an evaporator for air conditioners of motor verhicles. EP-A-0 415 584 discloses a stacked heat exchanger comprising a plurality of plate-shaped tubular elements stacked in a direction of their width with a fin member interposed between two of such tubular elements which have inlet header portions at their ends and outlet header portions at their other ends so that coolant can flow straight within the tubular elements, a pair of dish-shaped core plates which constitute each tubular element having inner surfaces provided with ribs arranged at regular intervals in a direction of coolant flow, wherein an end surface of each rib protruding from one core plate is alternately bonded to a flat body of the other core plate whereby the coolant paths within each tubular element are formed parallel with each other and straight from the inlet header portion toward the outlet header portion without inserted corrugated inner plates. US-A-5,024,269 refers to a laminated heat exchanger for use in automobile air-conditioners including a plurality of heat exchanger elements laminated together and each having a pair of tanks on one side thereof and connected by a U-shaped channel. The heat exchanger elements are communicated with each other so as to form a flow passage having at least four paths. An inlet and an outlet pipe are disposed in juxtaposition on one side of the laminated heat exchanger which is out of alignment with the path of flow of air to be cooled. However, there are no corrugated inner plates inserted in the flow passage. FR-A-2.010.517 discloses a heat exchanger similar to EP-A-0 415 584, wherein a U-shaped corrugated plate is provided along a U-shaped coolant flow passage integral and without any interruption with the tube plate, and there is no inner groove in each of the reciprocating chambers running parallel with peripheral sealing grooves formed in said pair of plates. With such preknown evaporators in air conditioners for motor vehicles, effecting dehumification of air with lowering of temperature thereof below its dew point temperature, condensed water inhibits efficient heat exchange. Therefore it is desired to rapidly clear condensed water on the surface of an evaporator as drain water by draining grooves. However, a decrease of heat transmission due to an increase in the number of grooves is the main cause of lowering the function of heat exchange in pre-known evaporators. Additionally, the division of inner plates due to the increase and the number of grooves will lead to an increase in part to be used. Therefore, disadvantageously, the number of assembly steps increases same as manufacturing problems. To overcome the above mentioned problems, the invention provides a stacked heat exchanger as specified in claim 1. Further advantageous embodiments of this heat exchanger are mentioned in dependent claims 2-6. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of the stacked heat exchanger in an embodiment of the present invention. Fig. 2 is an exploded perspective view of the coolant flow passages used in the first embodiment of the present invention. Fig. 3 is a cross-sectional view of the same coolant flow passages when assembled. Fig. 4 is an exploded perspective view of the coolant flow passages used in the second embodiment of the present invention. Fig. 5 is a cross-sectional view of the same coolant flow passages when assembled. Fig. 6 is an enlarged view of the X portion of Fig. 5. Fig. 7 is a cross-sectional view of coolant flow passages used in the third embodiment of the present invention. Fig. 8 is a perspective view of the same coolant flow passages and the air-side fins when assembled. Fig. 9 is a cross-sectional view at the line indicated by arrow IV in Fig. 1. Fig. 10 is a view of line IV - IV of Fig. 9 Fig. 11 is an enlarged view of the area indicated by the arrow V in Fig. 1. Fig. 12 is a cross-sectional view through line III - III of Fig. 1. Fig. 13 is an exploded perspective view of the flat tubes. Fig. 14 is a side view of the surface of one of the butted plates forming the flat tubes. Fig. 15 is a cross-sectional view through line C - C of Fig. 1. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 is a side view of the stacked heat exchanger in an embodiment of the present invention. Fig. 2 is an exploded perspective view of flat coolant tubes, and Fig. 3 is a cross-sectional view of the flat coolant tubes when assembled. In these figures, the flat coolant tubes 81 are formed by butting two press-formed plates 82. At one end of the flat tubes 81 (the upper end in Fig. 1), an intake/outlet tank section 83 is formed. The flat tubes 81 and corrugated air-side fins 84 are alternately stacked and the intake/outlet tank sections 83 are connected so as to form an stacked heat exchanger (evaporator) 85. At the outer sides 81a of the flat tubes 81 that are located at either end of the exchanger 85, end plates 86 are fitted. In the end plate 86 passage holes 87 are formed through to the intake/outlet tank section 83. One of the passage holes 87 is connected with a coolant intake header 88 and the other passage hole 87 is connected with a coolant outlet header 89. On the outside of the end plates 86, there are the corrugated air-side fins 84 and side plates 90 fitted outside these fins 84. Next, the structure of flat coolant tubes 81 is explained. In Figs. 2 and 3, there are shown a pair of the formed plates 82, and the intake/outlet tank section 83 which is formed at the top of each formed plate 82 with grooves. Parallel grooves 47, 46, 67 are formed on the formed plates 82. The difference between this formed plate 82 and a conventional plate is that the formed plate 82 of the present invention has additional inner grooves 67, which run parallel to the groove of the conventional plate. Corrugated inner plates 52 are fitted in between the formed plates 82 at the time of assembly. For illustrating purpose, there are four of the corrugated plates 52 in each flat tube, whereas the invention claims only two plates. In this embodiment, condensed water can flow down through the gap between grooves 46, 47 and 67 of formed plates 82 and the air-side fins 84. With this structure, the amount of condensed water running into the air-side fins is reduced, making it possible to reduce the amount of water splashing out from the backwash side of the evaporator. It should be noted that the number of the grooves 67 may be increased beyond two; there is no restriction on this. In figures 4-6, a pair of formed plates 82b are approximately the equivalent of those used in the first embodiment. Parallel grooves 46, 47, 67 are formed in the formed plates 82b. Two corrugated inner plates 52b are fitted in between the formed plates at the time of assembly. One corrugated plate 52b is mounted astride two coolant passages as illustrated in Figs. 5 and 6. With this structure, the number of necessary parts is reduced. Also, it is possible to create more coolant passages by forming more grooves and to prepare and use corrugated plates that can be fitted astride more than two coolant passages to accommodate any number of passages. The function and operation of this embodiment in relation to the down flowing condensed water are the same as those in the first embodiment. In figures 7 and 8, reference numeral 82c denotes the formed plate, 46, 47 and 67 the grooves, 83 the tank section, 50 the coolant turn grooves for guiding the coolant through a U-turn, the arrows 70 indicate the flow direction of the coolant and the range h 1 is the coolant U-turn area. The difference between this formed plate and the formed plates in the first and second embodiments is that the inner grooves 67 on both plates are continuous with the coolant turn groove 50 through the U-turn section. In this figure, h 2 indicates the range which is below the bottom of the aforementioned continuous coolant turn groove. In Fig. 8, reference numeral 52c indicates the corrugated plates. Both the formed plates 82c and the corrugated plates 52c may be identical to those in either embodiment 1 or embodiment 2. Reference numeral 84 indicates the air-side fin, 60 the flow of the condensed water, and 61 the air flow. In this embodiment, the condensed water 60 which is collected in the inner grooves 67 flows down the same grooves 67. The condensed water which has flowed down runs into one of the coolant turn grooves 50 connected to the opposite groove 67 at the coolant U-turn section and flows out onto the air-side fin 84 within the area indicated by h 2 , which also indicates the height of the bottom of the coolant turn grooves. Part of the condensed water 60 that has flowed out this way will flow into the coolant turn groove which is located immediately below the first one and then flows out onto the next air-side fin. A similar flow will occur at the coolant turn groove which is yet one lower, making the condensed water 60 flow to an even lower position. Because of this, the entirety of the condensed water 60 flowing in the grooves 67 finally goes out onto the air-side fins 84 at the height of the lower end of the lowest coolant turn groove, thereby minimizing the chance of the condensed water 60 flowing out from the air backwash side of the evaporator. Therefore, with this embodiment, the chances of water splashing out from the rear in the backwash air flow of the evaporator are reduced. Next the structure of the side plate 90 is explained using Figs. 9 and 10. Fig. 10 is a cross-sectional view along the line B-B in Fig. 9. As shown in Figs. 9 and 10, there are three grooves 91 formed on the inner surface of the side plate 90. These grooves 91 extend vertically and project out on the external surface. The condensed water on the inner surface of the side plate 90 flows down guided by the three grooves 91. Also, as shown in Fig. 9, there are a plurality of through holes 92 provided, which go through the side plate 90. The diameters of these holes 92 gradually become larger toward the lower end. The condensed water on the inner surface of the side plate 90 is discharged to the outside through these through holes 92. These through holes 92 need not be round but can be elongated. By creating grooves 91 and through holes 92 in the side plate 90, the condensed water on the inside of the side plate 90 flows down guided by the grooves and is discharged to the outside through the through holes 92. This means that the condensed water does not flow to the backwash side of the air flow. The structure of the upper section of the side plate 90 is explained based on Figs. 1 and 11. Fig. 11 shows an enlarged view of the portion indicated by arrow V in Fig. 1. The cross section of the outlet header 89 is approximately rectangular, and the outlet header 89 is connected with passage hole 87 in the end plate 86. At the upper end of the side plate 90, the end of the horizontal section 93 is bonded to the end plate 86. The bottom surface of the outlet header 89 and the top surface of the horizontal section 93 are aligned and are bonded by means of brazing. Because the outlet header 89 and the side plate 90 are bonded, if pressure is applied, the force applied to the intake/outlet tank section 83 in the direction of the width is absorbed by the side plate 90, preventing deformation of the entire evaporator 85. As grooves 91 are formed on the side plate 90 and project on its outside, the side plate 90 has sufficient strength and deformation is reliably prevented. The core section of the evaporator 85 has a larger total area of brazing because at this core section the plates 82 are joined together via the corrugated inner fins 52. This results in a large difference in strength between the intake/outlet tank section 83 and the core section. Because of this, if there is pressure applied, there is a significant difference in the amount of deformation occurring at the core section and at the intake/outlet tank section 83. However, by bonding the outlet header 89 and side plate 90, deformation can be sufficiently prevented even for the evaporator 85 which is inherently weak. In Fig. 11, the bonded section of the outlet header 89 and the side plate 90 is shown. The intake header 88 has an identical shape as the outlet header 89 so the bonded areas with side plate 90 is exactly the same on both ends. As the bottom surface of the intake header 88 and the outlet header 89 are bonded to the top surface of side plate 90 in the evaporator 85, any force applied to the intake/outlet tank section 83 in the direction of width when pressure is applied is absorbed by the side plate 90. Thus, deformation of the entire evaporator 85 due to the large difference in strength between the core section and the intake/outlet tank section 83 is avoided. Furthermore, as there is no gap present between the intake header 88 and outlet header 89 and the side plate 90, there is no air leak, eliminating the problem of lowered heat exchange performance . Fig. 12 shows a fourth embodiment and is a cross-sectional view along line C - C in Fig. 1. As shown in Fig. 12, in the flat portion of corrugated air-side fins 84 a plurality of cut and raised louvers are formed along the direction of air flow (vertical in the figure), and the raised louvers 95 are parceled into blocks of a specific number of louvers to form louver groups 96. Between one louver group 96 and another, there is a non-louvered section 97. Corrugated fins 84 are arranged between the flat tubes 81 in such a manner that non-louvered sections 97 correspond with the grooves 47 and 67 of the plate 82. In the evaporator 85 of the aforementioned structure, the air flow is directed into upper and lower flow paths by the flat portion of each corrugated air-side fin 84, and the exchange of intaken air between different air paths is achieved through passages formed at the raised louvers 95. The width of the non-louvered sections 97 of the corrugated fins 84 is larger than the width at the louver groups 96, but as the non-louvered sections 97 are positioned at locations that correspond with the grooves 47 and 67 of the plate 82, the portions of the corrugated fins 84 where the louver groups 96 are located come in contact with the plate 82. Because of this, the contact between the corrugated fins 84 and the flat tubes 81 becomes continuous line contact, eliminating any unbrazed areas from occurring. The grooves 47 and 67 have a function of drawing promptly downward the drain water which condenses on the surface of the flat tubes 81 and the corrugated fins 84. Fig. 13 is an exploded perspective view of the flat tubes used in the fifth embodiment of the present invention, and Fig. 14 is a front view of the butting surface of the plates that form the flat tubes. Fig. 15 shows a cross section through the line C - C in Fig. 1. As shown in Fig. 13, the flat tubes 81 are formed by butting two press-formed plates 82 together. At one end of the flat tubes 81 (the upper end in the figure) an intake/outlet tank section 83 is formed. As shown in Fig. 1, the flat tubes 81 and the corrugated air-side fins 84 are alternately stacked and the intake/outlet tank sections 83 are connected to form the stacked heat exchanger (evaporator) 85. The intake/outlet tank section 83 is partitioned into an intake section 44 and an outlet section 45 in the direction of the width of the panel of flat tubes 81. When the evaporator 85 is assembled, the adjacent intake/outlet tank sections 83 are connected by means of communicating holes 46 in such a manner that the intake sections 44 communicate with one another and the outlet sections 45 communicate with one another. As shown in Figs. 13 and 14, the inner hollow section of the plate 82 is partitioned into two chambers 48 and 49 by a partitioning wall 47 which extends vertically. The lower end of partitioning wall 47 is open and the lower end of plates 82 thereby form a U-turn section 50 in which the fluid coolant makes a U-turn. By butting two plates 82 the partitioning wall 47 divides the intake/outlet tank section 83 into the intake section 44 and the outlet section 45 and it further separates the chamber 48 that extends from intake section 44 from the chamber 49 that extends from outlet section 45. Furthermore, chambers 48 and 49 communicate at the U-turn section 50, thus a fluid passage 51 is created by the chambers 48 and 49 and the U-turn section 50. Within the chambers 48 and 49 (between the dotted lines), the corrugated inner plates 52 and 53 are inserted into the fluid passage 51. As shown in Fig. 15, in the corrugated inner plates 52 and 53, a plurality of corrugations 52a and 53a are formed along the direction of the length, so that flow paths 54 and 55 running along the direction of the length (vertically in the figure) of the chambers 48 and 49 are formed independently to divide the coolant flow into separate paths. In the U-turn part of the fluid passage 51, a plurality of semicircular turn flow passages 56 guide the flow of the coolant through the U-turn in independent paths. The passages 56 are formed by a plurality of U-shaped beads 57 which are press formed on the inside surface of the plates 82. The passages 56 make a turn along the shape of the plates 82. When the coolant flows between the chambers 48 and 49, the coolant flowing in flow paths 54 and 55 located outside with respect to the width direction of the flat tubes 81 flows in the flow passages 56 through the outside portion of the U-turn section 50. Also, the coolant flowing in flow paths 54 and 55 located inside with respect to the width direction of the flat tubes 81 flows in the flow passages 56 through the inside part of the U-turn section 50. In other words, the coolant within the flat tubes 81 flows in the fluid passage 51 by going from inner side to inner side and from outer side to outer side. As shown in Figs. 13 and 15, there is provided an inner groove in the chamber 84 of the plate 82. The groove 67 forms on the outer side of the plate 82 a groove 71 extending parallel to the dividing groove 47. The height of the groove 67 (or the depth of the groove 71) is such that the groove 67 comes into contact with the inner surface of chamber 49 of the other plate when a pair of plates 82 are butted and joined together. Also, as shown in Fig. 15, the width H of the groove 71, at the downstream side (lower area in the figure) of the air flow, is wider than the width h of the groove 71 at the upstream side (upper area in the figure). In other words, the flat tubes 81 are formed by butting two different types of plates 82 in which grooves 67 of differing width are formed. Furthermore, as shown in Fig. 15, the flat portion of the corrugated fins 84 has cut and raised louvers 95 formed along the direction of the air flow and the exchange of intaken air between different air paths which are partitioned vertically by the corrugated fins 84 is achieved through these raised louvers 95. The corrugated fin 84 is divided into corrugated fins 84a, 84b, 84c and 84d and aligned with the position of the grooves 71 and the dividing groove 47 to make up divided sections 98. A drain channel 99 is formed with the groove 71 and the back side of the projection 47 and the divided section 98. In the evaporator 85 described above, the fluid coolant which flows through the intake section 44 of the flat tube 81 is guided to the U-turn section 50 via the separate flow paths 54 formed by the corrugated inner plates 52, makes a U-turn at the separate turn flow passages 56 formed with the U-shaped beads 57 and then flows to the outlet portion 45 via the separate flow paths 55 formed by the corrugated inner plates 53. The coolant flowing within the flat tubes 81 flows into the subdivided flow paths 54 and 55 and the turn flow passages 56, which means the coolant flows in the fluid passage 51 from inside to inside and from outside to outside. This limits the separation of gas and liquid in a two phase flow of coolant that results from the centrifugal force exerted in the U-turn section 50 within the turn flow passages 56. Thus, there is reduced distribution of gas and liquid in a two phase flow of coolant. Also, as the flow passages 56 of the U-turn section 50 is U-shaped along the form of the plate 82, there is no impedance of flow of the coolant. Because of this, distribution of gas and liquid in the coolant is reduced, so that loss of thermal efficiency due to the separation of gas and liquid is less likely. At the same time, the likelihood of occurrence of inconsistent heat exchange performance due to impedance of the coolant flow is eliminated. While the coolant flows within the flat tubes 81, air is supplied between the corrugated fins 84 and the air is cooled by the latent heat of evaporation of the coolant. In the aforementioned evaporator 85, as the groove 71 of the flat tubes 81 is formed in the chamber 84 of one of the plates 82 at a depth at which it fits exactly the inner surface of the chamber 49 of the other plate 82, a drain channel 99 of approximately the same depth as the thickness of flat tubes 81 is obtained. Also, in the aforementioned evaporator 85, as the width H of the groove 71 on the downstream side of the air flow is greater than the width h of the groove 71 on the upstream side of the air flow, the condensed water does not flow out of the drain channel 99 even if the amount of condensed water increases on the downstream side of the air flow. In the aforementioned evaporator 85, as the corrugated fins 84 are divided according to the position of the groove formed by groove 71 of the flat tubes 81 and the projection 47 and the drain channel 99 is formed with the groove formed by the groove 71 and projection 47 and the divided section 98, the condensed water flowing down is guided by the groove and is not blocked by the corrugated fins 84.

Claims: A stacked heat exchanger, in particular an evaporator for air conditioners of motor vehicles, comprising pairs of formed plates (82, 82b, 82c) each formed with a shallow dish portion, said pair of plates (82, 82b) facing each other and being connected together to form a flat coolant tube (81) comprising a U-shaped flow passage (51) with reciprocating chambers (48, 49) and a semi-circular turn flow passage (56), U-shaped beads (57) formed at said turn flow passage (56), a coolant intake portion (44) and a coolant outlet portion (45) at one end of said shallow dish portion, the latter portions (44, 45) being made deeper than the former dish portion, corrugated inner plates (52, 52a, 52b, 53, 53a) inserted in said reciprocating chambers (48, 49), respectively, said coolant tube (81) and a corrugated air-side fin (84) being alternately stacked in a plurality of layers, a side plate (90) being provided at each lateral side of said stacking, a peripheral groove (46) formed in said pair of plates (82, 82b) to seal the periphery of said coolant tube (81), a deviding groove (47) in said pair of plates (82) to form a partition between said reciprocating chambers (48, 49) and a inner groove (67, 71) in each of said reciprocating chambers (48, 49) running parallel with said other grooves (46, 47), each of said corrugated inner plates (52, 52a, 52b, 53, 53a) extending through the chambers (48, 49) ending with a clearance to said beads (57) and being mounted astride of one inner groove (67, 71) and extending within the two coolant passages of one chamber (48, 49). Heat exchanger according to claim 1, wherein each inner groove (67) is made of a concave portion of such a depth to come in contact with a complementary groove (67) of said formed plates (82, 82b, 82c) or in contact with the inner surface of the other formed plate (82, 82b) through a portion of said corrugated inner plates (52, 52a, 52b, 53, 53a). Heat exchanger according to claim 1, wherein a plurality of said inner grooves (71) is provided in the widthwise direction of said coolant tube (81), the width of said inner grooves (71) being gradually made wider from upstream to downstream of air flow. Heat exchanger according to claim 1, wherein each corrugated air-side fin (84) is formed with a plurality of cut and raised louvers (95) at a flat portion thereof along the direction of an air flow. Heat exchanger according to claim 1, wherein each corrugated air-side fin (84) has subdivided portions (98) corresponding to the positions of said deviding and inner grooves (47, 67), a drain discharge groove (99) being formed by said sub-divided portion (98) of each corrugated air-side fin (84) and said grooves (47, 67), respectively. Heat exchanger according to claim 1, wherein each inner groove (67) has an end (67a) facing an intermediate portion of a plurality of U-shaped beads (57) of said turn flow passage (56).

Inventors: HAYASHI MASATERU, HIRAO YASUHIKO, IOKAWA HIROSHI, ISHII KAZUO, ITO AKIHIRO, KAWAI HIDENAO, HAYASHI, MASATERU, HIRAO, YASUHIKO, IOKAWA, HIROSHI, ISHII, KAZUO, ITO, AKIHIRO, KAWAI, HIDENAO, Hayashi, Masateru, c/o Mitsubishi Jukogyo K.K., Hirao, Yasuhiko, c/o Mitsubishi Jukogyo K.K., Iokawa, Hiroshi, c/o Mitsubishi Jukogyo K.K., Ishii, Kazuo, c/o Mitsubishi Jukogyo K.K., Ito, Akihiro, c/o Mitsubishi Jukogyo K.K., Kawai, Hidenao, c/o Mitsubishi Jukogyo K.K.
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1993
Main classification: B60H1
IPC codes: F25B39, F28F17, F28D1, B60H1