Heat exchanger

Abstract: The present invention relates to a heat exchanger in which a plate-shaped refrigerant flow portion (11) which provides an internal refrigerant flow path (R) by overlaying two flat plates (13, 14) formed by drawing and a cooling fin (12) are alternately layered; and comprising an opening portion (13a, 14a) provided on each of the flat plates and which is connected with the refrigerant flow path; and a continuous space (Sa) for the flow of the refrigerant which is provided by connecting the opening portions of adjacent refrigerant flow portions. The refrigerant which flows in the space is distributed to the respective refrigerant flow paths through the opening portions. The heat exchanger further comprises a means for improving the heat exchange capacity, and this means is, for example, a narrowing means (31) which is provided at the upstream end part of the space in order to uniformly distribute the refrigerant to the refrigerant flow paths.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a heat exchanger as defined by the features of the preamble portion of claim 1 which is used for an air conditioner. Description of the Related Art Figs. 5 to 9 show examples of structures of heat exchangers which are used as evaporators for vehicular air conditioners and the like. The heat exchangers shown in these figures are called drawn-cup type heat exchangers, and each air conditioner is constructed by alternately overlaying plate shaped refrigerant passage portions and corrugated plate shaped cooling fins. In Figs. 5 and 6, reference numeral 11 denotes the refrigerant flow portions and reference numeral 12 denotes the cooling fins. The refrigerant flow portion 11 is obtained by overlaying substantially rectangular flat plates 13 and 14 which are formed by drawing, and brazing at the outer peripheral portions and the central portions thereof. A refrigerant inlet 15 and a refrigerant outlet 16 are provided side by side at the lower end part of the refrigerant flow portion 11, and an inverted U-shaped refrigerant flow path R which extends upwardly from the refrigerant inlet 15 and turns downwards at the top of the refrigerant flow portion 11 toward the refrigerant outlet 16, is formed within the refrigerant flow portion 11. A plurality of dimples 17 are formed in the refrigerant flow portion 11 by denting the flat plates 13 and 14 which form the refrigerant flow path R from the outside, and these dimples 17 form a plurality of bulged portions 18 in the refrigerant flow path R. Furthermore, the left end of the laminated refrigerant flow portions 11 and cooling fins 12 are covered by a side plate 19. Hereinafter, the left end of each figure is referred to as the "proximal end" and the right end of each Figure is referred to as the "distal end". The refrigerant inlet 15 is composed of opening portions 13a and 14a formed in the flat plates 13 and 14, and the refrigerant inlets 15 of the respective refrigerant flow portions 11 are directly overlaid with no intervening cooling fin 12, so that a continuous space Sa is formed. Similarly, the refrigerant outlet 16 is composed of opening portions 13b and 14b formed in the flat plates 13 and 14, and the refrigerant outlets 16 of the respective refrigerant flow portions 11 are directly overlaid with no intervening cooling fins 12, so that a continuous space Sb is formed. The proximal end of the space Sa is connected with a refrigerant inlet pipe 20 which extends from the central part of the height of the heat exchanger, and the proximal end of the space Sb is connected with a refrigerant outlet pipe 21. Furthermore, the distal end of each space Sa, Sb is closed by a cover which is not shown in Figures. In this heat exchanger, refrigerant which flows into the space Sa through the refrigerant inlet pipe 20 is distributed to each of the refrigerant flow paths R, undergoes heat exchange while it passes through the refrigerant flow paths R, and then is collected at the space Sb and exits from the refrigerant outlet pipe 21. The heat exchanger shown in Figs. 7 to 9 provides the refrigerant inlet 15 and the refrigerant outlet 16 at the upper end part of the refrigerant flow portion 11, and a U-shaped refrigerant flow path R which extends downwards from the refrigerant inlet 15 and turns upwards at the bottom of the refrigerant flow portion 11 towards the refrigerant outlet 16 is formed within the refrigerant flow portion 11. Furthermore, in this air conditioner, the bulged portions 18 are not provided, and a corrugated inner fin 18a is sandwiched between each of the flat plates 13 and 14. In addition, the proximal end of the space Sa is connected with the refrigerant inlet pipe 20 via a header 22, and the distal end of the space Sb is connected with the refrigerant outlet pipe 21 via a header 23. In this heat exchanger, refrigerant which flows into the space Sa from the refrigerant inlet pipe 20 through the header 22 is distributed to each of the refrigerant flow paths R, undergoes heat exchange while passing through the refrigerant flow path R, and then is collected at the space Sb and exits from the refrigerant outlet pipe 21. However, when the refrigerant inlet pipe 20 has a 90 degree curve adjacent to the space Sa as denoted by symbol A in Fig. 5 for example, the flow of the refrigerant is slowed down due to the curve, and therefore, the refrigerant may not reach the innermost regions (the distal end part) of the space Sa, and the refrigerant may not flow to the distal end part of the space Sa. As a result, the refrigerant may not be uniformly distributed throughout the respective refrigerant flow paths R, and consequently, the problem that heat exchange is not sufficient at the refrigerant flow paths R at the distal end part may occur. Furthermore, the heat exchangers as described above are manufactured by braze welding. For example, in the heat exchanger shown in Figs. 8 and 9, the refrigerant flow portion 11 is constructed by brazing the flat plates 13 and 14 at flange portions 13c and 14c which are provided on the outer peripheral portions thereof as shown in Fig. 9. In addition, adjacent refrigerant inlets 15 (or refrigerant outlets 16) are fastened by brazing a flange-shaped side wall 13d which is formed at each opening portion 13a (or 14b) and a flange-shaped side wall 14d which is formed at adjacent opening portion 14a (or 13b). However, in the latter case, the fastening positions of the refrigerant inlets 15 or refrigerant outlets 16 protrude into the space Sa or Sb and give rise to resistance to the flow of fluid (refrigerant) in the space Sa or Sb. As a result, the pressure loss of the fluid which passes the space Sa or Sb caused by the resistance increases to a significant level, and the heat exchange capacity of the heat exchanger decreases. A prior art heat exchanger with the features of the preamble portion of claim 1 is disclosed in US-A-5 979 544. This heat exchanger is provided with plates separating the space into different blocks, whereby the flow between the blocks is controlled by increasing/decreasing the flow passage area for the heat exchanging medium to influence the fluid level within the respective heat exchanger blocks. The present invention was made in consideration of the above-mentioned circumstances, and an object of the present invention is to uniformly distribute the refrigerant in the space Sa and improve the heat exchange capacity of the heat exchanger. SUMMARY OF THE INVENTION The present invention relates to a heat exchanger as defined by claim 1 in which a plate-shaped refrigerant flow portion provides an internal refrigerant flow path by overlaying two flat plates formed by drawing and a cooling fin are alternately layered, an opening portion is provided on each of the flat plates and which is connected with the refrigerant flow path, and a continuous space for the flow of the refrigerant is provided by connecting the opening portions of adjacent refrigerant flow portions, wherein the refrigerant which flows in the space is distributed to the respective refrigerant flow paths through the opening portions. Particularly, the heat exchanger of the present invention is characterized by comprising a means for improving the heat exchange capacity. This means is a narrowing means which is provided at an upstream end part of the space in order to uniformly distribute the refrigerant to the respective refrigerant flow paths, for example. In this case, it is preferable to provide a rectifier which rectifies the flow of the refrigerant along the longitudinal direction of the space at a downstream end side of the space, and it is further preferable to provide the rectifier adjacent to the narrowing means. BRIEF EXPLANATION OF THE DRAWINGS Fig. 1 is a cross sectional view showing a connecting portion of the refrigerant inlet pipe and the space in the first embodiment of the heat exchanger according to the present invention. Fig. 2A is a cross sectional view showing a connecting portion of the refrigerant inlet pipe and the space in another embodiment of the heat exchanger according to the present invention. Fig. 2B is a cross sectional view showing a connecting portion of the refrigerant inlet pipe and the space in another embodiment of the heat exchanger according to the present invention. Fig. 3 is a cross sectional view showing a region including the vicinity of the space in another example of the heat exchanger. Fig. 4 is a cross sectional view showing a region including the vicinity of the space in another example of the heat exchanger. Fig. 5 is a cross sectional view showing an example of the structure of a conventional heat exchanger. Fig.6 is a perspective view showing the structure of the refrigerant flow portion of the heat exchanger shown in Fig.5. Fig. 7 is a perspective view showing an example of the structure of a conventional heat exchanger. Fig.8 is a perspective view showing the structure of the refrigerant flow portion of the heat exchanger shown in Fig.7. Fig. 9 is a cross sectional view showing a region including the vicinity of the space in the heat exchanger shown in Fig.7. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in the following with reference to the Figures. In the following description, members having the same structure as the conventional heat exchangers shown in Figs. 5 to 9 are denoted by the same reference symbols as in these figures, and explanations thereof are omitted. An embodiment of the present invention is shown in Fig. 1. Fig. 1 shows a cross sectional view of the connecting portion of the refrigerant inlet pipe 20 and the space Sa, and a porous plate (narrowing means) 31 formed by an extension of the lower end of the side plate 19, is provided at the portion where the refrigerant inlet pipe 20 connects with the refrigerant inlet 15 located at the upstream end of the space Sa. The porous plate 31 has a plurality of pores 31a, and a piece of punched metal or a wire mesh can also be used as the porous plate 31. The porous plate 31 is inclined at an angle of 45 degrees, and it separates the lower end of the refrigerant inlet pipe 20 and the refrigerant inlet 15. Furthermore, a straight portion (rectifier) 32 which bends towards the refrigerant inlet 15 side at the downstream end side of the porous plate 31 is provided directly under the porous plate 31. The straight portion 32 is for rectifying the flow direction of the refrigerant along the longitudinal direction of the space Sa, and a horizontal plane 32a which has a predetermined length in the longitudinal direction of the space Sa is provided on the upper surface of the straight portion 32. The remainder of the structure of the heat exchanger is the same as that of the heat exchanger shown in Figs. 5 and 6. In the heat exchanger having the above structure, the refrigerant supplied by the refrigerant inlet pipe 20 is converted into a mist when it passes the porous plate 31, and the refrigerant is accelerated to obtain a flow which is sufficient to reach the innermost regions of the space Sa. As a result, the refrigerant is uniformly distributed throughout to all the refrigerant flow paths R, and the heat exchange capacity of the heat exchanger is improved. Furthermore, the flow of the refrigerant which passes the straight portion 32 is guided by the horizontal plane 32a and rectified along the longitudinal direction of the space Sa. Therefore, an effect which of curvature in the path of the refrigerant when it passes through the connecting portion of the refrigerant inlet pipe 20 and the space Sa is decreased, and the refrigerant is more uniformly distributed throughout the refrigerant flow paths R. Moreover, since the straight portion 32 is provided directly under the porous plate 31, the effect of the curvature of the path of the refrigerant is more effectively decreased, and the refrigerant is more uniformly distributed throughout the refrigerant flow paths R. In addition to the porous plate 30, the following structures can be used as the narrowing means. Figs. 2A and 2B show a pipe 33 which is provided at the inlet side of the space Sa and projects toward the upstream or downstream end of the space Sa in the longitudinal direction of the space Sa, and a porous plate 33a which is provided on the end surface of the pipe 33. In these embodiments, the inner surface of the pipe 33 acts as the straight portion 33b. While the above embodiments describe cases in which the refrigerant inlets 15 and refrigerant outlets 16 are provided side by side at the lower end parts of the heat exchangers, the narrowing means as shown in Fig. 1 through Fig. 2B can also be provided when the refrigerant inlet 15 and refrigerant outlet 16 are provided side by side at the upper end part of the heat exchanger, or when one of the refrigerant inlet 15 or refrigerant outlet 16 is provided at the upper end part of the heat exchanger and the other of the refrigerant inlet 15 or refrigerant outlet 16 is provided at the lower end part of the heat exchanger. Fig. 3 is a cross sectional view showing a region including the vicinity of the space Sa. In this heat exchanger, a tubular portion 13e which extends perpendicular to the flat plates 13, 14 and has a uniform enlarged diameter is provided at the proximal end part of the opening portion 13a (the end part not having the flange portion 13c), and a tubular portion 14e which extends perpendicular to the flat plates 13, 14 and has a uniform diameter which is not enlarged, is provided at the distal end part of the opening portion 14a (the end part not having the flange portion 14c), of a pair of flat plates 13, 14 which form the refrigerant flow portions 11. Furthermore, the tubular portions 13e, 14e are positioned in order to have the same axis as the opening portions 13a, 14a, and the tubular portions 13e, 14e of the adjacent refrigerant flow portions 11 face each other when the heat exchanger is assembled. The remainder of the structure of the heat exchanger is the same as that of the heat exchanger shown in Figs. 7 to 9. The flat plates 13 and 14 are fastened by brazing the flange portions 13c and 14c which are provided on the outer peripheral portions thereof. In addition, adjacent refrigerant inlets 15 are overlaid by inserting the tubular portion 14e into the tubular portion 13e of the adjacent refrigerant flow portion 11 so as to closely contact the inner peripheral surface of the tubular portion 13e and the outer peripheral surface of the tubular portion 14e, and brazing these surfaces. And as a result of overlaying these refrigerant inlets 15, the space Sa which has a tubular shape and no projections on its inner peripheral surface is formed. Here, the space Sb formed by overlaying the refrigerant outlets 16 also has the same structure as described above, though it is not shown in the figures. In the heat exchanger having the above structure, since there are no projections in the inner peripheral surface of the space Sa (or the Space Sb), the pressure loss of the fluid which passes through the space Sa (or the Space Sb) is decreased, and the heat exchange capacity of the heat exchanger is improved. The structure of the connecting portion of the flat plates 13, 14 can be modified as follows. Fig. 4 is a cross sectional view showing a region including the vicinity of the space Sa in a heat exchanger. In this example, a tubular portion 13f which extends substantially perpendicular to the flat plates 13, 14, and having a diameter which is gradually enlarged toward the edge of the opening portion 13a, is provided in place of the tubular portion 13e. The remainder of the structure of the heat exchanger is the same as that of the heat exchanger shown in Fig. 3. The flat plates 13 and 14 are fastened by brazing the flange portions 13c and 14c which are provided on the outer peripheral portions thereof. In addition, adjacent refrigerant inlets 15 are overlaid by inserting the tubular portion 14e into the tubular portion 13f of the adjacent refrigerant flow portion 11 so as to closely contact the inner peripheral surface of the tubular portion 13f and the outer peripheral surface of the tubular portion 14e, and brazing these surfaces. And as a result of overlaying these refrigerant inlets 15, the space Sa, which has a tubular shape and no projections on its inner peripheral surface, is formed. Here, the space Sb formed by overlaying the refrigerant outlets 16 also has the same structure as described above, though it is not shown in the figures. In the heat exchanger having the above structure, similarly to the heat exchanger shown in Fig. 3, since there are no projections in the inner peripheral surface of the space Sa (or the Space Sb), the pressure loss of the fluid which passes through the space Sa (or the Space Sb) is decreased, and the heat exchange capacity of the heat exchanger is improved. In addition, in the above embodiments, cases in which the refrigerant inlets 15 and refrigerant outlets 16 are provided side by side at the upper end parts of the heat exchangers are described. However, structures such as those shown in Figs. 3 and 4 can also be provided when the refrigerant inlet 15 and refrigerant outlet 16 are provided side by side at the lower end part of the heat exchanger or when one of the refrigerant inlet 15 or refrigerant outlet 16 is provided at the upper end part of the heat exchanger and the other of the refrigerant inlet 15 or refrigerant outlet 16 is provided at the lower end part of the heat exchanger.

Claims: A heat exchanger comprising a plurality of plate-shaped refrigerant flow portions (11) which respectively provide an internal refrigerant flow path (R) by overlaying two flat plates (13, 14) formed by drawing and cooling fins (12) alternately layered, wherein an opening portion (13a,14a) is provided on each of said flat plates (13,14) and is connected with the respective refrigerant flow path (R); and wherein a continuous space (Sa) for the flow of said refrigerant is provided by connecting the opening portions (13a,14a) of adjacent refrigerant flow portions (11) and refrigerant which flows in said space (Sa) during operation of the heat exchanger is distributed to said refrigerant flow paths (R) through said opening portions (13a ,14a) ; and a refrigerant inlet (20); characterized in that a plate (31; 33a) with a plurality of pores (31a) and a straight portion (32;33b) for rectifying the flow of said refrigerant along the longitudinal direction of said space (Sa) are provided at an inlet end of said space (Sa) in order to uniformly distribute said refrigerant from the refrigerant inlet (20) to the respective refrigerant flow paths (R). A heat exchanger according to claim 1, wherein said straight portion is formed by a rectifier (32) that is provided adjacent to said porous plate (31). A heat exchanger according to claim 1, wherein said straight portion is formed by the inner circumferential surface (33b) of a pipe (33) that is provided at the inlet side of said space (Sa) so as to project to the upstream or downstream side of said space (Sa) in the longitudinal direction of said space (Sa) and said porous plate (33a) is provided at an axial end of said pipe (33). A heat exchanger according to claim 1 or 2, wherein said porous plate (31) is inclined at an angle of 45° with respect to a refrigerant inlet pipe (20) and separates the lower end of the refrigerant inlet pipe (20) and a refrigerant inlet (15) to said space (Sa). A heat exchanger according to any one of claims 1 to 4, wherein said porous plate (31;33a) is formed by a piece of punched metal or a wire mesh.

Inventors: ANAI YUJIRO, INOUE MASASHI, SAITO KATSUHIRO, SUZUKI KAZUHIRO, WATANABE YOSHINORI, YOSHIKOSHI AKIRA, ANAI, YUJIRO, INOUE, MASASHI, SAITO, KATSUHIRO, SUZUKI, KAZUHIRO, WATANABE, YOSHINORI, YOSHIKOSHI, AKIRA, Anai, Yujiro, Mitsubishi Heavy Industries Ltd., Inoue, Masashi, Mitsubishi Heavy Industries Ltd., Saito, Katsuhiro, Mitsubishi Heavy Industries Ltd., Suzuki, Kazuhiro, Mitsubishi Heavy Industries Ltd., Watanabe, Yoshinori, Mitsubishi Heavy Industries, Yoshikoshi, Akira, Mitsubishi Heavy Industries Ltd
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 2001
Main classification: F28F27
IPC codes: F28F27, F28D1