Evaporator

Abstract

An evaporator includes a pair of header tanks spaced from each other in a vertical direction; a plurality of flat heat exchange tubes 45 which are disposed between the two header tanks such that their width direction coincides with a front-rear direction and they are spaced from one another in a left-right direction, opposite ends portions of the flat heat exchange tubes being connected to the corresponding header tanks; and corrugated fins 5 each disposed between adjacent heat exchange tubes 45. Each of left and right portions of front and rear end walls 45a of each heat exchange tube 45 has a straight slope portion 55 which inclines outward in the front-rear direction, toward a center portion of the heat exchange tube 45 with respect to the left-right direction. The angle formed between the slope portion 55 and the left edge or right edge of the corresponding corrugated fin 5 is set to 25 to 40 degrees.

Description

TECHNICAL FIELD

[0001] The present invention relates to an evaporator suitable for use in a car air conditioner, which is a refrigeration cycle to be mounted on an automobile, for example.

[0002] In this specification and the appended claims, the downstream side (a direction represented by arrow X in FIGS. 1, 2, 8, and 10) of an air flow through air-passing clearances between adjacent heat exchange tubes will be referred to as the "front," and the opposite side as the "rear." Further, the upper, lower, left-hand, and right-hand sides of FIG. 1 will be referred to as "upper," "lower," "left," and "right," respectively.

BACKGROUND ART

[0003] The present applicant has proposed an evaporator for a car air conditioner which satisfies the requirements for reduction in size and weight and higher performance (refer to Patent Document 1). The evaporator includes a pair of header tanks spaced from each other in the vertical direction; a plurality of flat heat exchange tubes which are formed of aluminum extrudate and which are disposed between the two header tanks such that their width direction coincides with the front-rear direction and they are spaced from one another in the longitudinal direction of the header tanks, opposite ends portions of the flat heat exchange tubes being connected to the corresponding header tanks; and corrugated fins each disposed between adjacent heat exchange tubes and having louvers. The upper header tank includes a refrigerant inlet header section and a refrigerant outlet header section, which are juxtaposed in the front-rear direction and are united together. The lower header tank includes a first intermediate header section disposed to face the refrigerant inlet header section, and a second intermediate header section disposed rearward of the first intermediate header section to face the refrigerant outlet header section and united with the first intermediate header section. The upper and lower end portions of the front heat exchange tubes are connected to the refrigerant inlet header section and the first intermediate header section, respectively, and the upper and lower end portions of the rear heat exchange tubes are connected to the refrigerant outlet header section and the second intermediate header section. Each of the front and rear end walls of each heat exchange tube has an arcuate transverse cross section projecting outward with respect to the front-rear direction.

[0004] Since the evaporator described in Patent Document 1 is designed to satisfy the requirements for reduction in size and weight and higher performance, a large amount of condensed water is produced on the surface of each corrugated fin, whereby the amount of condensed water per unit volume of the evaporator increases. Incidentally, an ordinary evaporator is designed such that water condensed on the fin surface flows downward through clearances between adjacent louvers. Therefore, in order to enhance water draining performance, increasing the length of the louvers is desirable. However, in order to reduce size and weight as in the case of the evaporator described in Patent Document 1, the clearance between heat exchange tubes located adjacent to each other in the longitudinal direction of the header tanks must be reduced. Therefore, there is a limit on increasing the length of the louvers, and water draining performance may become insufficient when the amount of condensed water is large.

PRIOR ART DOCUMENT

Patent Document

[0005] Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2008-20098

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0006] An object of the invention is to solve the above-described problem, and provide an evaporator which has an excellent performance of draining water condensed on the surfaces of fins.

Means for Solving the Problems

[0007] To achieve the above object, the present invention comprises the following modes.

[0008] 1) An evaporator comprising a pair of header tanks spaced from each other in a vertical direction; a plurality of flat heat exchange tubes which are disposed between the two header tanks such that their width direction coincides with a front-rear direction and they are spaced from one another in a left-right direction, opposite ends portions of the flat heat exchange tubes being connected to the corresponding header tanks; and corrugated fins each disposed between adjacent heat exchange tubes, wherein

[0009] each of left and right portions of front and rear end walls of each heat exchange tube has a straight slope portion which inclines outward in the front-rear direction, toward a center portion of the heat exchange tube with respect to the left-right direction, and an angle formed between the slope portion and a left edge or right edge of the corresponding corrugated fin is 25 to 40 degrees.

[0010] 2) An evaporator according to par. 1), wherein left and right side surfaces of each heat exchange tube are in contact with the corresponding corrugated fins; and a ratio of a length W2 (mm), as measured in the front-rear direction, of areas of contact between the left and right side surfaces of the heat exchange tube and the corresponding corrugated fins to a width W1 (mm) of each heat exchange tube as measured in the front-rear direction is 80 to 95%.

[0011] 3) An evaporator according to par. 1), wherein each heat exchange tube has a width of 10 to 20 mm as measured in the front-rear direction.

[0012] 4) An evaporator according to par. 1), wherein each heat exchange tube has a thickness of 1 to 1.8 mm as measured in the left-right direction.

[0013] 5) An evaporator according to par. 1), wherein a plurality of tube sets each composed of a plurality of flat heat exchange tubes spaced from one another in the front-rear direction are disposed between the upper and lower header tanks at predetermined intervals in the left-right direction; each of the fins is disposed between tube sets located adjacent to each other in the left-right direction; and, in each tube set composed of a plurality of the flat heat exchange tubes, a clearance is formed between the heat exchange tubes located adjacent to each other in the front-rear direction, the clearance having a width of 1.5 to 3.5 mm as measured in the front-rear direction.

[0014] 6) An evaporator according to par. 1), wherein each heat exchange tube is provided in a flat hollow body composed of two pressed rectangular metal plates laminated and joined together; the two metal plates which constitute the flat hollow body are bulged outward so as to form the heat exchange tube such that the heat exchange tube is open at upper and lower ends thereof; each of front and rear walls of an outward bulged portion of each metal plate which forms the heat exchange tube is straight and inclines outward in the front-rear direction, toward a thicknesswise center portion of the flat hollow body.

[0015] 7) An evaporator according to par. 6), wherein, at a front edge of each flat hollow body, one of the two metal plates has a protrusion formed over the entire length thereof such that a distal end portion of the protrusion projects beyond the other metal plate and toward the corrugated fin with which the other metal plate is in contact.

Effects of the Invention

[0016] According to the evaporators of par. 1) to 7), each of left and right portions of the front and rear end walls of each heat exchange tube has a straight slope portion which inclines outward in the front-rear direction, toward a center portion of the heat exchange tube with respect to the left-right direction, and the angle formed between the slope portion and the left edge or right edge of the corresponding corrugated fin is 25 to 40 degrees. Therefore, recesses are formed between the slope portions of the front and rear end walls of each heat exchange tube and the left and right edges of the corresponding corrugated fins such that a corner portion of each recess located on the inner side with respect to the width direction of the heat exchange tube has an acute angle. Thus, due to surface tension, condensed water produced on the surfaces of the corrugated fins flows into the recesses as if it were drawn into the recesses, and flows downward through the recesses. Accordingly, the evaporator has an improved performance of draining the condensed water produced on the surfaces of the corrugated fins, whereby scattering of condensed water and a drop in heat exchange performance caused by freezing of condensed water are prevented.

[0017] According to the evaporator of par. 2), it is possible to restrain a drop in heat conduction performance caused by a decrease in the areas of contact between the heat exchange tubes and the corrugated fins, without preventing the flow of the condensed water into the recesses formed between the slope portions of the front and rear end walls of each heat exchange tube and the left and right edges of the corresponding corrugated fins.

[0018] According to the evaporator of par. 5), in each tube set composed of a plurality of flat heat exchange tubes disposed between the two header tanks, a clearance is formed between the heat exchange tubes located adjacent to each other in the front-rear direction, and the clearance has a width of 1.5 to 3.5 mm as measured in the front-rear direction. Thus, due to surface tension, condensed water produced on the surfaces of the corrugated fins flows into the clearances between the heat exchange tubes of each tube set located adjacent to each other in the front-rear direction, as if it were drawn into the clearances, and flows downward through the clearances. Accordingly, the evaporator has an improved performance of draining the condensed water produced on the surfaces of the corrugated fins, whereby scattering of condensed water and a drop in heat exchange performance caused by freezing of condensed water are prevented.

[0019] According to the evaporator according to par. 6), the straight slope portions--which incline outward in the front-rear direction, toward a center portion of the heat exchange tube with respect to the left-right direction--can be relatively easily formed at the left and right portions of the front and rear end walls of each heat exchange tube. Also, the angle formed between each slope portion and the left edge or right edge of the corresponding corrugated fin can be relatively easily set to 25 to 40 degrees.

[0020] According to the evaporator according to par. 7), scattering of condensed water from the front edge of each flat hollow body can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a partially cut-away perspective view showing the overall structure of an evaporator according to a first embodiment of the present invention.

[0022] FIG. 2 is a partially omitted enlarged sectional view taken along line A-A of FIG. 1.

[0023] FIG. 3 is an enlarged sectional view taken along line B-B of FIG. 2.

[0024] FIG. 4 is a graph showing the results of Experimental Examples 1 to 2 and Comparative Experimental Examples 1 to 2.

[0025] FIG. 5 is a graph relating to Experimental Examples 1 to 2 and Comparative Experimental Example 1 and showing the relation among the amount of retained water, contact ratio, and angle between slope portions of each heat exchange tube and left and right edges of corresponding corrugated fins.

[0026] FIG. 6 is a graph relating to Experimental Examples 1 to 2 and Comparative Experimental Example 1 and showing the relation between the ratio of the amount of retained water to the contact ratio obtained from the graph of FIG. 5, and the angle between slope portions of each heat exchange tube and left and right edges of corresponding corrugated fins.

[0027] FIG. 7 is a graph showing the results of Experimental Examples 3 to 4 and Comparative Experimental Examples 3 to 4.

[0028] FIG. 8 is a view corresponding to FIG. 2 and showing an evaporator according to a second embodiment of the present invention.

[0029] FIG. 9 is a partially omitted enlarged sectional view taken along line C-C of FIG. 8.

[0030] FIG. 10 is a view corresponding to FIG. 2 and showing an evaporator according to a third embodiment of the present invention.

[0031] FIG. 11 is a partially omitted enlarged sectional view taken along line D-D of FIG. 10.

DESCRIPTION OF REFERENCE NUMERALS

[0032] (1), (60), (90): evaporator [0033] (2), (3), (61), (62): header tank [0034] (4), (63): flat hollow body [0035] (5): corrugated fin [0036] (41), (75): metal plate [0037] (43), (95): clearance [0038] (44), (92): set of heat exchange tubes juxtaposed in the front-rear direction [0039] (48), (78): outward bulged portion [0040] (48a), (78a): front and rear walls [0041] (45), (76), (91): heat exchange tube [0042] (45a), (76a), (91a): front and rear end walls [0043] (55), (83), (93): slope portion [0044] (57), (85): protrusion

MODES FOR CARRYING OUT THE INVENTION

[0045] Embodiments of the present invention will next be described with reference to the drawings. Like portions and members are denoted by like reference numerals throughout the drawings, and repeated description is not provided.

[0046] In the following description, the term "aluminum" encompasses aluminum alloys in addition to pure aluminum.

First Embodiment

[0047] This embodiment is shown in FIGS. 1 to 3. FIG. 1 shows the overall structure of an evaporator, and FIGS. 2 and 3 show the structure of a main portion of the evaporator.

[0048] As shown in FIGS. 1 and 2, an evaporator (1) includes a first header tank (2) and a second header tank (3) formed of aluminum and disposed apart from each other in the vertical direction such that they extend in the left-right direction; a plurality of flat hollow bodies (4) formed of aluminum and disposed between the two header tanks (2) and (3) at predetermined intervals in the left-right direction (the longitudinal direction of the header tanks (2) and (3)) such that their width direction coincides with the front-rear direction and their longitudinal direction coincides with the vertical direction; louvered, corrugated fins (5) made of aluminum, disposed in air-passing clearances between the adjacent flat hollow bodies (4) and externally of the left- and right-end flat hollow bodies (4), and brazed to the flat hollow bodies (4); and side plates (6) made of aluminum, disposed externally of the left- and right-end corrugated fins (5) and brazed to the corrugated fins (5).

[0049] The first header tank (2) includes a refrigerant inlet header section (7) located on the front side (downstream side with respect to the air flow direction) and extending in the left-right direction; a refrigerant outlet header section (8) located on the rear side (upstream side with respect to the air flow direction) and extending in the left-right direction; and a connection section (9) which integrally connects the header sections (7) and (8) together. A refrigerant inlet pipe (11) made of aluminum is connected to the refrigerant inlet header section (7) of the first header tank (2). Similarly, a refrigerant outlet pipe (12) made of aluminum is connected to the refrigerant outlet header section (8). The second header tank (3) includes a first intermediate header section (13) located on the front side and extending in the left-right direction; a second intermediate header section (14) located on the rear side and extending in the left-right direction; and a connection section (15) which integrally connects the header sections (13) and (14) together.

[0050] The first header tank (2) is composed of a plate-like first member (16) which is formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and to which all the flat hollow bodies (4) are connected; a second member (17) which is formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and which covers the upper side of the first member (16); a flat partition portion forming plate (18) which is formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof or an aluminum bear material and which is interposed between the first member (16) and the second member (17) and is brazed to the two members (16) and (17); left and right end members (19) which are formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and which are brazed to the left ends and right ends, respectively, of the first member (16), the second member (17), and the partition portion forming plate (18); and a joint plate (21) which is formed of aluminum, extends in the front-rear direction, and is brazed to the outer surface of the right end member (19) such that the joint plate (21) extends across the refrigerant inlet header section (7) and the refrigerant outlet header section (8). The refrigerant inlet pipe (11) and the refrigerant outlet pipe (12) are connected to the joint plate (21). Notably, the joint plate (21) is formed from an aluminum bear material through press work.

[0051] The first member (16) has front and rear downward-bulged header forming portions (22) and (23) which form lower portions of the refrigerant inlet header section (7) and the refrigerant outlet header section (8); and a connection wall (24) which connects the front and rear header forming portions (22) and (23) together and forms a lower portion of the connection section (9). A plurality of tube insertion holes (25) elongated in the front-rear direction are formed in the two header forming portions (22) and (23) of the first member (21) at predetermined intervals in the left-right direction such that the positions (with respect to the left-right direction) of the tube insertion holes (25) formed in the front header forming portion (22) coincide with those of the corresponding tube insertion holes (25) formed in the rear header forming portion (23).

[0052] The second member (17) has front and rear upward-bulged header forming portions (26) and (27) which form upper portions of the refrigerant inlet header section (7) and the refrigerant outlet header section (8); and a connection wall (28) which connects the front and rear header forming portions (26) and (27) together and forms an upper portion of the connection section (9).

[0053] The partition portion forming plate (18) has a front partition portion (29) which divides the interior of the refrigerant inlet header section (7) into upper and lower spaces (7A) and (7B); a rear partition portion (31) which divides the interior of the refrigerant outlet header section (8) into upper and lower spaces (8A) and (8B); and a connection wall (32) which connects the two partition portions (29) and (31) together, and forms an intermediate portion (with respect to the vertical direction) of the connection section (9). A communication hole (33) for establishing communication between the upper and lower spaces (7A) and (7B) within the refrigerant inlet header section (7) is formed in the front partition portion (29) of the partition portion forming plate (18) at a position located leftward of the flat hollow body (4) disposed at the left end. A plurality of circular communication holes (34) for establishing communication between the upper and lower spaces (7A) and (7B) of the refrigerant inlet header section (7) are formed in an intermediate portion (with respect to the front-rear direction) of the front partition portion (29) of the partition portion forming plate (18) at predetermined intervals in the left-right direction. Further, a plurality of oblong communication holes (35) elongated in the left-right direction and adapted to establish communication between the upper and lower spaces (8A) and (8B) of the refrigerant outlet header section (8) are formed, at predetermined intervals in the left-right direction, in a rear portion of the rear partition portion (31) of the partition portion forming plate (18), excluding left and right end portions of the rear portion. The length of the oblong communication hole (35) in the central portion is shorter than those of the remaining oblong communication hole (35).

[0054] The left end member (19) closes the left end openings of the refrigerant inlet header section (7) and the refrigerant outlet header section (8), and the right end member (19) closes the right end openings of the refrigerant inlet header section (7) and the refrigerant outlet header section (8). Although not illustrated in the drawings, a refrigerant inlet is formed in a portion (facing the upper space (7A)) of a portion of the right end member (19) which portion closes the right end opening of the refrigerant inlet header section (7), and a refrigerant outlet is formed in a portion (facing the upper space (8A)) of a portion of the right end member (19) which portion closes the right end opening of the refrigerant outlet header section (8). The joint plate (21) has refrigerant passages which communicate with the refrigerant inlet and the refrigerant outlet of the right end member (19).

[0055] The second header tank (3) has a structure similar to that of the first header tank (2), and is disposed upside down with respect to the first header tank (2). Therefore, like portions are denoted by like reference numerals.

[0056] Notably, the two header forming portions (22) and (23) of the first member (16) of the second header tank (3) form upper portions of the first intermediate header section (13) and the second intermediate header section (14), and the two header forming portions (26) and (27) of the second member (17) of the second header tank (3) form lower portions of the first intermediate header section (13) and the second intermediate header section (14). Also, the interior of the first intermediate header section (13) is divided into upper and lower spaces (13A) and (13B) by the front partition portion (29) of the partition portion forming plate (18), and the interior of the second intermediate header section (14) is divided into upper and lower spaces (14A) and (14B) by the rear partition portion (31) of the partition portion forming plate (18). Furthermore, an intermediate portion of the connection portion (15) with respect to the vertical direction is formed by the connection wall (32) of the partition portion forming plate (18).

[0057] The second header tank (3) differs from the first header tank (2) in the following points.

[0058] The first difference is that a plurality of communication portions (36) for establishing communication between the lower space (13B) of the first intermediate header section (13) and the lower space (14B) of the second intermediate header section (14) are provided at predetermined intervals (with respect to the left-right direction) in a portion of the second member (17) which portion separates the lower spaces (13B) and (14B) of the two intermediate header sections (13) and (14) from each other. The communication portions (36) are provided at a plurality of locations such that each communication portion (36) is provided between two flat hollow bodies (4) located adjacent to each other with respect to the left-right direction and such that the amount of refrigerant within the second intermediate header section (14) can be made uniform along the longitudinal direction of the second header tank (3).

[0059] The second difference is that, in place of the communication hole (33) and the circular communication holes (34), a plurality of relatively large rectangular communication holes (37) elongated in the left-right direction are formed in the front partition portion (29) of the partition portion forming plate (18) at predetermined intervals in the left-right direction; and that, in place of the oblong communication holes (34), a plurality of circular communication holes (through holes) (38) are formed in a rear portion of the rear partition portion (31) of the partition portion forming plate (18) at predetermined intervals in the left-right direction.

[0060] The third difference is that the refrigerant inlet and the refrigerant output are not formed in the right end member (21), and the joint plate (21) is not brazed thereto.

[0061] As shown in FIGS. 2 and 3, each of the flat hollow bodies (4) is formed through a process of making two rectangular metal plates (41) from an aluminum brazing sheet through press working, and brazing the two rectangular metal plates (41), over the entire length thereof, along front and rear edge portions thereof and along center portions thereof with respect to the front-rear direction. Each of the flat hollow bodies (4) has two heat exchange tubes (45), the number of which is equal to the number of the header sections (7) and (8) of the first header tank (2) and the number of the header sections (13) and (14) of the second header tank (3). The heat exchange tubes (45) extend in the vertical direction, and are open at the upper and lower ends thereof. The heat exchange tubes (45) of each flat hollow body (4) are provided through formation of outward bulged portions (48) on the two metal plates (41) over the entire length thereof in regions between brazed portions (46) of the front and rear edge portions of the two metal plates (41), and brazed portions (47) of the center portions (with respect to the front-rear direction) of the two metal plates (41). The heat exchange tubes (45) have a flat shape such that their width direction coincides with the front-rear direction. Each flat hollow body (4) has a tube set (44) including a plurality of (two in the present embodiment) of flat heat exchange tubes (45) whose width direction coincides with the front-rear direction and which are spaced from each other in the front-rear direction. In each tube set (44), clearances (43) are formed between the heat exchange tubes (45) located adjacent to each other in the front-rear direction. That is, a plurality of tube sets (44)--each composed of a plurality of flat heat exchange tubes (45) disposed such that their width direction coincides with the front-rear direction and they are spaced from one another in the front-rear direction--are disposed between the first header tank (2) and the second header tank (3) at predetermined intervals in the left-right direction; and each of the corrugated fins (5) is disposed between the tube sets (44) (sets of the heat exchange tube (45)) located adjacent to each other in the left-right direction.

[0062] Upper and lower end portions of the brazed portions (46) of the front and rear edge portions of the two metal plates (41) of each flat hollow body (4) are cut such that the formed cutouts extend from the outer edges with respect to the front-rear direction to the upper and lower end surfaces, respectively. The cutouts are denoted by (51). Also, upper and lower end portions of the brazed portions (47) of the center portions (with respect to the front-rear direction) of the two metal plates (41) of each flat hollow body (4) have a width (as measured in the front-rear direction) greater than those of the remaining portions, and cutouts (52) are formed in wide brazed portions (47a) such that the cutouts (52) extend from the respective outer ends with respect to the vertical direction. Notably, due to provision of the width brazed portions (47a) on each flat hollow body (4), upper and lower end portions of each heat exchange tube (45) is narrower than the reaming portions as measured in the front-rear direction. As a result of formation of the cutouts (51) in the brazed portions (46) of the front and rear edge portions and formation of the cutouts (52) in the width brazed portions (47a) of the center portions with respect to the front-rear direction, the upper and lower end portions of each heat exchange tube (45) project outward with respect to the vertical direction from the remaining portions. The projecting portions serve as insertion portions (53) inserted into the tube insertion holes (25) of the first header tank (2) and the second header tank (3). The flat hollow bodies (4) are brazed to the first members (16) of the two header thanks (2) and (3) as follows. The upper and lower insertion portions (53) of the front heat exchange tubes (45) are inserted into the front tube insertion holes (25) of the first members (16) of the first header tank (2) and the second header tank (3). Similarly, the upper and lower insertion portions (53) of the rear heat exchange tubes (45) are inserted into the rear tube insertion holes (25) of the first members (16) of the first header tank (2) and the second header tank (3). At the time of the insertion operation, bottom side portions of the cutouts (51) of the brazed portions (46) of the front and rear edge portions of each flat hollow body (4) and bottom side portions of the cutouts (52) of the width brazed portions (47a) of the center portions of the flat hollow body (4) are brought into contact with the outer surfaces of the two header forming portions (22) and (23) of the respective first members (16) of the first header tank (2) and the second header tank (3), whereby the end portions of the flat hollow bodies (4) are positioned. In this state, the flat, hollow bodies (4) are brazed to the first members (16) of the first header tank (2) and the second header tank (3). The corrugated fins (5) are shared by the front and rear heat exchange tubes (45) of the corresponding flat hollow bodies (4). The crest portions or trough portions of each corrugated fin (5) are brazed to the corresponding heat exchange tube (45). Also, a plurality of louvers are formed on connection portions of each corrugated fin (5) located between the crest portions and trough portions thereof. Moreover, a corrugated inner fin (54) formed of aluminum is disposed in each flat hollow body (4) such that the corrugated inner fin (54) extends through the interiors of the two heat exchange tubes (45), and is brazed to the two metal plates (41).

[0063] Straight slope portions (55) are provided on left and right portions of front and rear end walls (45a) of the two heat exchange tubes (45) of each flat hollow body (4). The straight slope portions (55) incline outward with respect to the front-rear direction, toward the center portions of the heat exchange tubes (45) (with respect to the left-right direction). That is, front and rear walls (48a) of the outward bulged portions (48) of the metal plates (41) of each flat hollow body (4), which portions form the two heat exchange tubes (45), linearly incline in an outward direction with respect to the front-rear direction, toward the thicknesswise center of the flat hollow body (4). Thus, recess portions (56) are formed between the outer surfaces of the slope portions (55) of the front and rear end walls (45a) of the heat exchange tubes (45) of each flat hollow body, and the left and right edge portions of the corresponding corrugated fins (5). A corner portion of each recess (56) located on the inner side with respect to the width direction of the heat exchange tubes (45) has an acute angle. The angle .theta. formed between each of the slope portions (55) of the front and rear end walls (45a) of the two heat exchange tubes (45) and the left or right edge portion of the corresponding corrugated fin (5) is set to 25 to 40 degrees in consideration of drainage of water condensed on the surfaces of the flat hollow bodies (4) and the corrugated fins (5). Also, when the width of the heat exchange tubes (45) as measured in the front-rear direction is represented by W1 (mm) and the length (as measured in the front-rear direction) of contact areas where the left and right side surfaces of the heat exchange tubes (45) are in contact with the corresponding corrugated fins (5) is represented by W2 (mm), preferably, a contract ratio W2/W1; i.e., the ratio of W2 (the length (as measured in the front-rear direction) of the areas of contact between the left and right side surfaces of the heat exchange tubes (45) and the corresponding corrugated fins (5)) to W1 (the width of the heat exchange tubes (45) as measured in the front-rear direction), is 80 to 95%. Furthermore, preferably, the width W1 of the heat exchange tubes (45) as measured in the front-rear direction is 10 to 20 mm, and the thickness H of the heat exchange tubes (45) as measured in the left-right direction is 1 to 1.8 mm.

[0064] At each of the front and rear edges of each flat hollow body (4), a protrusion (57) is formed on one of the two metal plates (41) over the entire length thereof such that a distal end portion of the protrusion (57) projects beyond the other metal plate (41) and toward the corrugated fin (5) with which the other metal plate (41) is in contact. That is, a protrusion (57) whose distal end projects rightward beyond the right metal plate (41) is formed at the front edge of the left metal plate (41) of the flat hollow body (4) over the entire length thereof, and another protrusion (57) whose distal end projects leftward beyond the left metal plate (41) is formed at the rear edge of the right metal plate (41) of the flat hollow body (4) over the entire length thereof.

[0065] In each tube set (44) including the flat hollow bodies (4), preferably, the width S (as measured in the front-rear direction) of the clearances (43) formed between the heat exchange tube (45) located adjacent to each other in the front-rear direction is 1.5 to 3.5 mm. If the width S of the clearances (43) as measured in the front-rear direction is smaller than 1.5 mm, condensed water having been produced on the surfaces of the corrugated fins (5) and flowed into (as if it had been drawn into) the clearances (43) between the front and rear heat exchange tubes (45) of each tube set (44) by means of surface tension stagnates at the clearances (43) due to surface tension, which hinders a downward flow of the condensed water. If the width S of the clearances (43) as measured in the front-rear direction is greater than 3.5 mm, condensed water produced on the surfaces of the corrugated fins (5) becomes less likely to be drawn into the clearances (43). Also, preferably, the thickness H of the heat exchange tubes (45) as measured in the left-right direction is 1 to 1.8 mm, the width W of the heat exchange tubes (45) as measured in the front-rear direction is 10 to 20 mm.

[0066] In manufacture of the evaporator (1), component members thereof excluding the inlet pipe (11) and the outlet pipe (12) are assembled together, and brazed together.

[0067] The evaporator (1), together with a compressor and a condenser serving as a refrigerant cooler, constitutes a refrigeration cycle which uses a chlorofluorocarbon-based refrigerant. This refrigeration cycle is installed in a vehicle, such as an automobile, as a car air conditioner.

[0068] In the evaporator (1) described above, while the compressor is ON, a two-phase refrigerant of vapor-liquid phase having passed through the compressor, the condenser, and an expansion valve enters the upper space (7A) of the refrigerant inlet header section (7) from the refrigerant inlet pipe (11); flows through the lower space (7B) of the same, the front heat exchange tubes (45) of the flat hollow bodies (4), the upper space (13A) of the first intermediate header section (13), the lower space (13B) of the same, the lower space (14B) of the second intermediate header section (14), the upper space (14A) of the same, the rear heat exchange tubes (45) of the flat hollow bodies (4), the lower space (8B) of the refrigerant outlet header section (8), and the upper space (8A) of the same; and flows out to the refrigerant outlet pipe (12).

[0069] While flowing through the front and rear heat exchange tubes (45) of the flat hollow bodies (4), the refrigerant is subjected to heat exchange with air flowing through the air-passing clearances between the adjacent flat hollow bodies (4). Then, the refrigerant flows out from the evaporator (1) in a vapor phase.

[0070] At that time, condensed water is produced on the surfaces of the corrugated fins (5). Due to surface tension, the condensed water flows into the recesses (56) formed between the outer surfaces of the slopes portions (55) of the front and rear end walls (45a) of the heat exchange tubes (45) of each flat hollow body (4) and the left and right edges of the corresponding corrugated fins (5), as if the condensed water were drawn into the recesses (56). After that, the condensed water flows downward via the recesses (56). Accordingly, the evaporator (1) has an improved condensed water draining performance, whereby a drop in the performance of the evaporator (1) is prevented. Furthermore, frontward scattering of condensed water is restrained by the action of the protrusion (57) at the front edge of each flat hollow body (4).

[0071] Next, experimental examples which were performed by use of the flat hollow bodies (4) of the evaporator (1) according to the first embodiment will be described along with comparative experimental examples.

Experimental Example 1

[0072] There was prepared an assembly which was equivalent to an assembly obtained by removing the two header tanks (2) and (3), the refrigerant inlet pipe (11), and the refrigerant outlet pipe (12) from the evaporator (1) of the first embodiment, and in which only the flat hollow bodies (4), the corrugated fins (5), and the side plates (6) were brazed together. The angle .theta. between each of the slope portions (55) of the front and rear end walls (45a) of the two heat exchange tubes (45) of each flat hollow body (4) and the left or right edge portion of the corresponding corrugated fin (5) was 25 degrees. The assembly was immersed in water within a tank for removal of air remaining within the assembly. After that, the assembly was allowed to stand for 30 minutes. Subsequently, the assembly was lifted such the flat hollow bodies (4) became vertical, and was removed from the water. In this state, the weight of the assembly was measured for 30 minutes so as to investigate a change in the amount of retained water.

Experimental Example 2

[0073] An assembly identical with that used in Experimental Example 1 except that the angle .theta. between each of the slope portions (55) of the front and rear end walls (45a) of the two heat exchange tubes (45) and the left or right edge portion of the corresponding corrugated fin (5) was set to 35 degrees was prepared, and a change in the amount of retained water was investigated in the same manner as in Experimental Example 1. Notably, the width W1 of the heat exchange tubes (45) as measured in the front-rear direction and the thickness H of the heat exchange tubes (4) as measured in the left-right direction are the same as those of the heat exchange tubes used in the Experimental Example 1.

Comparative Experimental Example 1

[0074] An assembly identical with that used in Experimental Example 1 except that the angle .theta. between each of the slope portions (55) of the front and rear end walls (45a) of the two heat exchange tubes (45) and the left or right edge portion of the corresponding corrugated fin (5) was set to 45 degrees was prepared, and a change in the amount of retained water was investigated in the same manner as in Experimental Example 1. Notably, the width W1 of the heat exchange tubes (45) as measured in the front-rear direction and the thickness H of the heat exchange tubes (4) as measured in the left-right direction are the same as those of the heat exchange tubes used in the Experimental Example 1.

Comparative Experimental Example 2

[0075] Instead of the flat hollow bodies (4), tube pairs each composed of two heat exchange tubes spaced from each other in the front-rear direction were brazed together with the corrugated fins (5) and the side plates (6), whereby an assembly was prepared. The heat exchange tubes had the same structure as that disclosed in Patent Document 1; i.e., the front and rear end walls of the heat exchange tubes had an arcuate shape, as viewed on a transverse cross section, which was convex outward with respect to the front-rear direction. Notably, the heat exchange tubes used in Comparative Experimental Example 2 have the same width (as measured in the front-rear direction) and thickness (as measured in the left-right direction) as those of the heat exchange tubes used in the Experimental Example 1. A change in the amount of retained water was investigated in the same manner as in Experimental Example 1.

[0076] FIG. 4 shows the results of Experimental Examples 1 to 2 and Comparative Experimental Examples 1 to 2. As is clear from the results shown in FIG. 4, in Experimental Examples 1 to 2, the amount of retained water after elapse of 30 minutes is smaller as compared with Comparative Experimental Example 1 to 2, and excellent draining performance is attained.

[0077] FIG. 5 shows the relation among the amount of retained water, the contact ratio W2/W1, and the angle .theta. obtained from Experimental Example 1 to 2 and Comparative Experimental Example 1. As described previously, the contract ratio W2/W1 is the ratio of W2 (the length (as measured in the front-rear direction) of the areas of contact between the left and right side surfaces of the heat exchange tubes and the corresponding corrugated fins) to W1 (the width of the heat exchange tubes as measured in the front-rear direction). The angle .theta. is the angle between each of the slope portions of the front and rear end walls of the heat exchange tubes and the left or right edge portion of the corresponding corrugated fin.

[0078] FIG. 6 shows the relation between the ratio of the water retraining amount to the contact ratio W2/W1 and the angle .theta. between each of the slope portions of the front and rear end walls of the heat exchange tubes and the left or right edge portion of the corresponding corrugated fin. The graph of FIG. 6 means that, when the ratio of the water retraining amount to the contact ratio W2/W1 is small, it is possible to restrain a drop in heat conduction performance caused by a decrease in the areas of contact between the heat exchange tubes and the corrugated fins, while preventing a drop in draining performance. Accordingly, the results shown in FIG. 6 demonstrate that, when the angle .theta. between each of the slope portions of the front and rear end walls of the heat exchange tubes and the left or right edge portion of the corresponding corrugated fin is 25 to 40 degrees, the condensed water draining performance can be enhanced, while a required thermal conductivity is secured.

Experimental Example 3

[0079] There was prepared an assembly which was equivalent to an assembly obtained by removing the two header tanks (2) and (3), the refrigerant inlet pipe (11), and the refrigerant outlet pipe (12) from the evaporator (1) of the first embodiment, and in which only the flat hollow bodies (4), the corrugated fins (5), and the side plates (7) were brazed together. The width S (as measured in the front-rear direction) of the clearances (43) formed between the front and rear heat exchange tubes (45) of each flat hollow body (4) was 1.6 mm. The assembly was immersed in water within a tank for removal of air remaining within the assembly. After that, the assembly was allowed to stand for 30 minutes. Subsequently, the assembly was lifted such the flat hollow bodies (4) became vertical, and was removed from the water. The assembly was held in this state for 30 minutes, and the amount of retained water after elapse of 30 minutes was measured.

Experimental Example 4

[0080] An assembly identical with that used in Experimental Example 3 except that the width S (as measured in the front-rear direction) of the clearances (43) formed between the front and rear heat exchange tubes (45) of each flat hollow body (4) was 2.8 mm was prepared, and the amount of retained water after elapse of 30 minutes was measured in the same manner as in Experimental Example 3. Notably, the width W of the heat exchange tubes (45) as measured in the front-rear direction and the thickness H of the heat exchange tubes (45) as measured in the left-right direction are the same as those of the heat exchange tubes used in the Experimental Example 1.

Comparative Experimental Example 3

[0081] An assembly identical with that used in Experimental Example 3 except that the width S (as measured in the front-rear direction) of the clearances (43) formed between the front and rear heat exchange tubes (45) of each flat hollow body (4) was 1.0 mm was prepared, and the amount of retained water after elapse of 30 minutes was measured in the same manner as in Experimental Example 3. Notably, the width W of the heat exchange tubes (45) as measured in the front-rear direction and the thickness H of the heat exchange tubes (45) as measured in the left-right direction are the same as those of the heat exchange tubes used in the Experimental Example 1.

Comparative Experimental Example 4

[0082] Instead of the flat hollow bodies (4), tube pairs each composed of two heat exchange tubes having the same structure as that of the heat exchange tubes used in the above-described Comparative Experimental Example 2 were brazed together with the corrugated fins (5) and the side plates (6), whereby an assembly was prepared. Notably, the heat exchange tubes used in Comparative Experimental Example 4 have the same width (as measured in the front-rear direction) and thickness (as measured in the left-right direction) as those of the heat exchange tubes used in the Experimental Example 3; and the width (as measured in the front-rear direction) of the clearances formed between the front and rear heat exchange tubes of each tube set was the same as that of the assembly used in the Experimental Example 3. The amount of retained water after elapse of 30 minutes was measured in the same manner as in Experimental Example 3.

[0083] FIG. 7 shows the results of Experimental Examples 3 to 4 and Comparative Experimental Examples 3 to 4. As is clear from the results shown in FIG. 7, in Experimental Examples 3 to 4, the amount of retained water after elapse of 30 minutes is smaller as compared with Comparative Experimental Example 3 to 4, and excellent draining performance is attained. Therefore, in order to enhance the water draining performance of the evaporator, the width (as measured in the front-rear direction) of the clearances formed between the heat exchange tubes adjacent to each other in the front-rear direction must be set to 1.5 to 3.5 mm.

Embodiment 2

[0084] This embodiment is shown in FIGS. 8 and 9. FIGS. 8 and 9 show the structure of a main portion of an evaporator according to the present embodiment.

[0085] As shown in FIGS. 8 and 9, an evaporator (60) includes a first header tank (61) and a second header tank (62) formed of aluminum and disposed apart from each other in the vertical direction such that they extend in the left-right direction; a plurality of flat hollow bodies (63) formed of aluminum and disposed between the two header tanks (61) and (62) such that their width direction coincides with the front-rear direction and they are spaced from one another in the left-right direction; corrugated fins (5) made of aluminum, disposed in air-passing clearances between the adjacent flat hollow bodies (63) and externally of the left- and right-end flat hollow bodies (63), and brazed to the flat hollow bodies (63); and side plates (not shown) made of aluminum, disposed externally of the left- and right-end corrugated fins (5) and brazed to the corrugated fins (5).

[0086] The entirety of the first header tank (61) serves as a refrigerant inlet header section (65), and the entirety of the second header tank (62) serves as a refrigerant outlet header section (66). A refrigerant inlet pipe (not shown) is connected to the refrigerant inlet header section (65) of the first header tank (61), and a refrigerant outlet pipe (not shown) made of aluminum is connected to the refrigerant outlet header section (66) of the second header tank (62).

[0087] The first header tank (61) is composed of a plate-like first member (67) which is formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and to which all the flat hollow bodies (63) are connected; a second member (68) which is formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and which covers the upper side of the first member (67); a flat partition portion forming plate (69) which is formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof or an aluminum bear material and which is interposed between the first member (67) and the second member (68) and is brazed to the two members (67) and (68); and left and right end members (not shown) which are formed, through press work, from an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and which are brazed to left ends and right ends, respectively, of the first member (67), the second member (68), and the partition portion forming plate (69).

[0088] The first member (67) forms a lower portion of the refrigerant inlet header section (65), and the second member (68) forms an upper portion of the refrigerant inlet header section (65). A plurality of tube insertion holes (71) elongated in the front-rear direction are formed in the first member (67) at predetermined intervals in the left-right direction. The partition portion forming plate (69) has a partition portion (73) which divides the interior of the refrigerant inlet header section (65) into upper and lower spaces (65A) and (65B). A plurality of relatively large rectangular communication holes (74) elongated in the left-right direction are formed in each of front and rear portions of the partition portion (73) of the partition portion forming plate (69) at predetermined intervals in the left-right direction. The left and right end members close the left and right end openings of the refrigerant inlet header section (65). A refrigerant inlet is formed in the left end member or the right end member at a position corresponding to the upper space (65A).

[0089] The second header tank (62) has a structure similar to that of the first header tank (61), and is disposed upside down with respect to the first header tank (61). Therefore, like portions are denoted by like reference numerals.

[0090] Notably, the first member (67) of the second header tank (3) forms an upper portion of the refrigerant outlet header section (66), and the second member (68) thereof forms a lower portion of the refrigerant outlet header section (66). The partition portion (73) of the partition portion forming plate (69) divides the interior of the refrigerant outlet header section (66) into upper and lower spaces (66A) and (66B). A refrigerant outlet is formed in the left end member or the right end member at a position corresponding to the lower space (66B).

[0091] Each of the flat hollow bodies (63) is formed through a process of making two rectangular metal plates (75) from an aluminum brazing sheet through press working, and brazing the two rectangular metal plates (75), over the entire length thereof, along front and rear edge portions thereof. Each of the flat hollow bodies (63) has only one heat exchange tube (76), the number of which is equal to the number of the header section (65) of the first header tank (61) and the number of the header section (66) of the second header tank (62). The heat exchange tube (76) extends in the vertical direction, and is open at the upper and lower ends thereof. The heat exchange tube (76) of each flat hollow body (63) is provided through formation of outward bulged portions (78) on the two metal plates (75) over the entire length thereof in a region between brazed portions (77) of the front and rear edge portions of the two metal plates (75). The heat exchange tube (76) has a flat shape such that its width direction coincides with the front-rear direction.

[0092] Upper and lower end portions of the brazed portions (77) of the front and rear edge portions of the two metal plates (75) of each flat hollow body (63) are cut such that the formed cutouts extend from the outer edges with respect to the front-rear direction to the upper and lower end surfaces, respectively. The cutouts are denoted by (81). As a result of formation of the cutouts (81) in the brazed portions (77) of the front and rear edge portions, the upper and lower end portions of each heat exchange tube (76) project outward with respect to the vertical direction from the remaining portions. The projecting portions serve as insertion portions (82) inserted into the tube insertion holes (71) of the first header tank (61) and the second header tank (63). The flat hollow bodies (63) are brazed to the first members (67) of the two header thanks (61) and (62) as follows. The upper and lower insertion portions (82) of the heat exchange tubes (76) are inserted into the tube insertion holes (71) of the first members (67) of the first header tank (61) and the second header tank (62). At the time of the insertion operation, bottom side portions of the cutouts (81) of the brazed portions (77) of the front and rear edge portions of each flat hollow body (63) are brought into contact with the outer surfaces of the respective first members (67) of the first header tank (61) and the second header tank (62), whereby the end portions of the flat hollow bodies (63) are positioned. In this state, the flat hollow bodies (63) are brazed to the first members (67) of the first header tank (61) and the second header tank (62). The crest portions or trough portions of the corrugated fins (5) are brazed to the corresponding heat exchange tube (76). Moreover, a corrugated inner fin (79) formed of aluminum is disposed in the heat exchange tube (76) of each flat hollow body (63), and is brazed to the two metal plates (75).

[0093] Straight slope portions (83) are provided on left and right portions of front and rear end walls (76a) of the heat exchange tube (76) of each flat hollow body (63). The straight slope portions (83) incline outward with respect to the front-rear direction, toward the center portion (with respect to the left-right direction) of the heat exchange tube (76). That is, front and rear walls (78a) of the outward bulged portions (78) of the metal plates (75) of each flat hollow body (63), which portions form the heat exchange tube (76), linearly incline in an outward direction with respect to the front-rear direction, toward the thicknesswise center of the flat hollow body (63). Thus, recess portions (84) are formed between the outer surfaces of the slope portions (83) of the front and rear end walls (76a) of the heat exchange tube (76) of each flat hollow body (63), and the left and right edge portions of the corresponding corrugated fins (5). A corner portion of each recess (84) located on the inner side with respect to the front-rear direction has an acute angle. The angle .theta. formed between each of the slope portions (83) of the front and rear end walls (76a) of each heat exchange tube (76) and the left or right edge portion of the corresponding corrugated fin (5) is set to 25 to 40 degrees in consideration of drainage of water condensed on the surfaces of the flat hollow bodies (63) and the corrugated fins (5). Also, when the width of the heat exchange tube (76) as measured in the front-rear direction is represented by W1 (mm) and the length (as measured in the front-rear direction) of contact areas where the left and right side surfaces of the heat exchange tube (76) are in contact with the corresponding corrugated fins (5) is represented by W2 (mm), preferably, a contract ratio W2/W1; i.e., the ratio of W2 (the length (as measured in the front-rear direction) of the areas of contact between the left and right side surfaces of the heat exchange tube (76) and the corresponding corrugated fins (5)) to W1 (the width of the heat exchange tube (76) as measured in the front-rear direction), is 80 to 95%. Furthermore, preferably, the width W1 of the heat exchange tube (76) as measured in the front-rear direction is 10 to 20 mm, and the thickness H of the heat exchange tubes (76) as measured in the left-right direction is 1 to 1.8 mm.

[0094] At each of the front and rear edges of each flat hollow body (63), a protrusion (85) is formed on one of the two metal plates (75) over the entire length thereof such that a distal end portion of the protrusion (85) projects beyond the other metal plate (75) and toward the corrugated fin (5) with which the other metal plate (75) is in contact. That is, a protrusion (85) whose distal end projects rightward beyond the right metal plate (75) is formed at the front edge of the left metal plate (75) of the flat hollow body (63) over the entire length thereof, and another protrusion (85) whose distal end projects leftward beyond the left metal plate (75) is formed at the rear edge of the right metal plate (75) of the flat hollow body (63) over the entire length thereof.

[0095] The evaporator (60), together with a compressor and a condenser serving as a refrigerant cooler, constitutes a refrigeration cycle which uses a chlorofluorocarbon-based refrigerant. This refrigeration cycle is installed in a vehicle, such as an automobile, as a car air conditioner.

[0096] In the evaporator (60) described above, while the compressor is ON, a two-phase refrigerant of vapor-liquid phase having passed through the compressor, the condenser, and an expansion valve enters the refrigerant inlet header section (65) of the first header tank (61) from the refrigerant inlet pipe via the refrigerant inlet of the right end member or the left end member; flows through the heat exchange tubes (76) and the refrigerant outlet header section (66); and flows out to the refrigerant outlet pipe.

[0097] While flowing through the heat exchange tubes (76) of the flat hollow bodies (63), the refrigerant is subjected to heat exchange with air flowing through the air-passing clearances between the adjacent flat hollow bodies (63). Then, the refrigerant flows out from the evaporator (60) in a vapor phase.

[0098] At that time, condensed water is produced on the surfaces of the corrugated fins (5). Due to surface tension, the condensed water flows into the recesses (84) formed between the outer surfaces of the slopes portions (83) of the front and rear end walls (76a) of the heat exchange tube (76) of each flat hollow body (63) and the left and right edges of the corresponding corrugated fins (5), as if the condensed water were drawn into the recesses (84). After that, the condensed water flows downward via the recesses (84). Accordingly, the evaporator (60) has an improved condensed water draining performance, whereby a drop in the performance of the evaporator (1) is prevented. Furthermore, frontward scattering of condensed water is restrained by the action of the protrusion (85) at the front edge of each flat hollow body (63).

Third Embodiment

[0099] This embodiment is shown in FIGS. 10 and 11. FIGS. 10 and 11 show the structure of a main portion of an evaporator according to the present embodiment.

[0100] As shown in FIGS. 10 and 11, an evaporator (90) includes a first header tank (2) and a second header tank (3), which have the same structures as those of the first header tank (2) and the second header tank (3) of the evaporator (1) of the first embodiment and which are disposed apart from each other in the vertical direction. A plurality of tube sets (92) are disposed between the two header tanks (2) and (3) at predetermined intervals in the left-right directions. Each tube set (92) includes two flat heat exchange tubes (91), the number of which is equal to the number of the header sections (7) and (8) of the first header tank (2) and the number of the header sections (13) and (14) of the second header tank (3). The flat heat exchange tubes (91) are formed of aluminum extrudate and disposed such that their width direction coincides with the front-rear direction and they are spaced from each other in the front-rear direction. Corrugated fins (5) made of aluminum are disposed in air-passing clearances between adjacent tube sets (92) each composed of the front and rear heat exchange tubes (91), and externally of the left- and right-end tube sets (92), and brazed to the corresponding heat exchange tubes (91). Side plates (not shown) made of aluminum are disposed externally of the left- and right-end corrugated fins (5) and brazed to the corrugated fins (5). In each set (92) composed of two heat exchange tubes (91) adjacent to each other in the front-rear direction, a clearance (95) is formed between the two heat exchange tubes (91).

[0101] The front and rear heat exchange tubes (91) are brazed to the first members (16) of the two header thanks (2) and (3) as follows. Upper and lower end portions of the front heat exchange tubes (91) are inserted into the front tube insertion holes (25) of the first members (16) of the first header tank (2) and the second header tank (3). Similarly, upper and lower end portions of the rear heat exchange tubes (91) are inserted into the rear tube insertion holes (25) of the first members (16) of the first header tank (2) and the second header tank (3). In this state, the front and rear heat exchange tubes (91) are brazed to the first members (16) of the first header tank (2) and the second header tank (3). The corrugated fins (5) are shared by the front and rear heat exchange tubes (91). The crest portions or trough portions of each corrugated fin (5) are brazed to the corresponding heat exchange tube (91).

[0102] Straight slope portions (93) are provided on left and right portions of front and rear end walls (91a) of each heat exchange tube (91). The straight slope portions (93) incline outward with respect to the front-rear direction, toward the center portion of the heat exchange tube (91) with respect to the left-right direction. Portions of the front and rear end walls (91a) between the two slope portions (93) are orthogonal to the left and right edges of the corrugated fins (5). Thus, recess portions (94) are formed between the outer surfaces of the slope portions (93) of the front and rear end walls (91a) of each heat exchange tube (91) and the left and right edge portions of the corresponding corrugated fins (5). A corner portion of each recess (94) located on the inner side with respect to the width direction of the heat exchange tubes (91) has an acute angle. The angle .theta. formed between each of the slope portions (93) of the front and rear end walls (91a) of each heat exchange tubes (91) and the left or right edge portion of the corresponding corrugated fin (5) is set to 25 to 40 degrees in consideration of drainage of water condensed on the surfaces of the heat exchange tubes (91) and the corrugated fins (5). Also, when the width of the heat exchange tubes (91) as measured in the front-rear direction is represented by W1 (mm) and the length (as measured in the front-rear direction) of contact areas where the left and right side surfaces of the heat exchange tubes (91) are in contact with the corresponding corrugated fins (5) is represented by W2 (mm), preferably, a contract ratio W2/W1; i.e., the ratio of W2 (the length (as measured in the front-rear direction) of the areas of contact between the left and right side surfaces of the heat exchange tube (91) and the corresponding corrugated fins (5)) to W1 (the width of the heat exchange tubes (91) as measured in the front-rear direction), is 80 to 95%. Furthermore, preferably, the width W1 of the heat exchange tubes (91) as measured in the front-rear direction is 10 to 20 mm, and the thickness H of the heat exchange tubes (91) as measured in the left-right direction is 1 to 1.8 mm.

[0103] In each tube set (92) composed of the front and rear heat exchange tubes (91), preferably, the width S (as measured in the front-rear direction) of the clearance (95) formed between the heat exchange tubes (91) located adjacent to each other in the front-rear direction is 1.5 to 3.5 mm. If the width S of the clearance (63) as measured in the front-rear direction is smaller than 1.5 mm, condensed water having been produced on the surfaces of the corrugated fins (5) and flowed into (as if it had been drawn into) the clearance (95) between the front and rear heat exchange tubes (91) of each tube set (92) by means of surface tension stagnates at the clearance (95) due to surface tension, which hinders a downward flow of the condensed water. If the width S of the clearance (95) as measured in the front-rear direction is greater than 3.5 mm, condensed water produced on the surfaces of the corrugated fins (5) becomes less likely to be drawn into the clearance (95).

[0104] The evaporator (90), together with a compressor and a condenser serving as a refrigerant cooler, constitutes a refrigeration cycle which uses a chlorofluorocarbon-based refrigerant. This refrigeration cycle is installed in a vehicle, such as an automobile, as a car air conditioner.

[0105] In the evaporator (90) described above, while the compressor is ON, a two-phase refrigerant of vapor-liquid phase having passed through the compressor, the condenser, and an expansion valve enters the upper space (7A) of the refrigerant inlet header section (7) from the refrigerant inlet pipe (11); flows through the lower space (7B) of the same, the front heat exchange tubes (91), the upper space (13A) of the first intermediate header section (13), the lower space (13B) of the same, the lower space (14B) of the second intermediate header section (14), the upper space (14A) of the same, the rear heat exchange tubes (91), the lower space (8B) of the refrigerant outlet header section (8), and the upper space (8A) of the same; and flows out to the refrigerant outlet pipe (12).

[0106] While flowing through the front and rear heat exchange tubes (91), the refrigerant is subjected to heat exchange with air flowing through the air-passing clearances between the tube sets (92) each composed of adjacent heat exchange tubes (91). Then, the refrigerant flows out from the evaporator (90) in a vapor phase.

[0107] At that time, condensed water is produced on the surfaces of the corrugated fins (5). Due to surface tension, the condensed water flows into the recesses (94) formed between the outer surfaces of the slopes portions (93) of the front and rear end walls (91a) of each heat exchange tube (91) and the left and right edges of the corresponding corrugated fins (5), as if the condensed water were drawn into the recesses (94). After that, the condensed water flows downward via the recesses (94). Accordingly, the evaporator (90) has an improved condensed water draining performance, whereby a drop in the performance of the evaporator (1) is prevented.

INDUSTRIAL APPLICABILITY

[0108] The evaporator according to the present invention is suitable for use in a refrigeration cycle which constitutes a car air conditioner.

Claims

1. An evaporator comprising a pair of header tanks spaced from each other in a vertical direction; a plurality of flat heat exchange tubes which are disposed between the two header tanks such that their width direction coincides with a front-rear direction and they are spaced from one another in a left-right direction, opposite ends portions of the flat heat exchange tubes being connected to the corresponding header tanks; and corrugated fins each disposed between adjacent heat exchange tubes, wherein each of left and right portions of front and rear end walls of each heat exchange tube has a straight slope portion which inclines outward in the front-rear direction, toward a center portion of the heat exchange tube with respect to the left-right direction, and an angle formed between the slope portion and a left edge or right edge of the corresponding corrugated fin is 25 to 40 degrees.

2. An evaporator according to claim 1, wherein left and right side surfaces of each heat exchange tube are in contact with the corresponding corrugated fins; and a ratio of a length W2 (mm), as measured in the front-rear direction, of areas of contact between the left and right side surfaces of the heat exchange tube and the corresponding corrugated fins to a width W1 (mm) of each heat exchange tube as measured in the front-rear direction is 80 to 95%.

3. An evaporator according to claim 1, wherein each heat exchange tube has a width of 10 to 20 mm as measured in the front-rear direction.

4. An evaporator according to claim 1, wherein each heat exchange tube has a thickness of 1 to 1.8 mm as measured in the left-right direction.

5. An evaporator according to claim 1 wherein a plurality of tube sets each composed of a plurality of flat heat exchange tubes spaced from one another in the front-rear direction are disposed between the upper and lower header tanks at predetermined intervals in the left-right direction; each of the fins is disposed between tube sets located adjacent to each other in the left-right direction; and, in each tube set composed of a plurality of the flat heat exchange tubes, a clearance is formed between the heat exchange tubes located adjacent to each other in the front-rear direction, the clearance having a width of 1.5 to 3.5 mm as measured in the front-rear direction.

6. An evaporator according to claim 1, wherein each heat exchange tube is provided in a flat hollow body composed of two pressed rectangular metal plates laminated and joined together; the two metal plates which constitute the flat hollow body are bulged outward so as to form the heat exchange tube such that the heat exchange tube is open at upper and lower ends thereof; each of front and rear walls of an outward bulged portion of each metal plate which forms the heat exchange tube is straight and inclines outward in the front-rear direction, toward a thicknesswise center portion of the flat hollow body.

7. An evaporator according to claim 6, wherein, at a front edge of each flat hollow body, one of the two metal plates has a protrusion formed over the entire length thereof such that a distal end portion of the protrusion projects beyond the other metal plate and toward the corrugated fin with which the other metal plate is in contact.