WO2006070923A1

WO2006070923A1 - Heat exchanger

Info

Publication number: WO2006070923A1
Application number: PCT/JP2005/024238
Authority: WO
Inventors: Yoshihiko Seno; Osamu Kamoshida
Original assignee: Showa Denko K.K.
Priority date: 2004-12-28
Filing date: 2005-12-27
Publication date: 2006-07-06
Also published as: DE112005003259T5

Abstract

A heat exchanger 1 includes a condenser section 2, a subcooling section 3, and a gas-liquid separator section 4 which is provided between the condenser section 2 and the subcooling section 3; and is configured to allow a refrigerant to flow out of the condenser section 2 into the subcooling section 3 through the gas-liquid separator section 4. The gas-liquid separator section 4 includes a pair of headers 21, 22 and liquid receiving tubes 23 which are disposed between the headers 21, 22. A refrigerant inlet 32 is provided on an upper wall 21a of one of the headers 21 of the gas-liquid separator section 4 and a refrigerant outlet 33 is provided on a lower wall 22b of the other header 22 of the gas-liquid separator section 4. The gas-liquid separator section includes flow rate lowering means which has a mesh material 34 spread across the refrigerant inlet 32 and a passage extending member 35 which is formed in the other header 22 so as to enclose the refrigerant outlet 33 and to extend the length of the passage through which the refrigerant moves from the refrigerant inlet 32 to the refrigerant outlet 33. This heat exchanger 1 exhibits enhanced gas-liquid separation effect in the gas-liquid separator section.

Description

DESCRIPTION

HEAT EXCHANGER

CROSS REFERENCE TO RELATED APPLICATIONS

This application is an application filed under 35 U.S.C. § lll(a) claiming the benefit pursuant to 35 U.S.C. § 119(e)(l) of the filing date of Provisional Application No. 60/641,731 filed January 7, 2005 pursuant to 35 U.S.C. § lll(b) .

TECHNICAL FIELD

The present invention relates to a heat exchanger for a refrigerant cycle which takes part in, for example, an automotive air conditioner.

In the present specification and claims, the top and bottom of FIG. 1 and FIG. 8 will be referred to as "top" (or up, upper, or a similar expression) and "bottom" (or down, lower, or a similar expression) , respectively.

BACKGROUND ART

In recent years, in order to improve the performance of mounting a heat exchanger into an automobile body, a certain type of heat exchanger for a refrigerant cycle in an automotive air conditioner has been developed and come to be known. The heat exchanger has a condenser section having a pair of headers spaced apart from each other, a plurality of heat exchange tubes which are disposed between the headers so that opposite end portions of the tubes are connected to their corresponding headers, and a corrugate fin which is disposed between, and is bonded to, mutually neighboring heat exchanger tubes; a subcooling section having a pair of headers spaced apart from each other, a plurality of heat exchange tubes which are disposed therebetween so that opposite end portions of the tubes are connected to their corresponding headers, and a corrugate fin which is disposed between, and is bonded to, mutually neighboring heat exchanger tubes; and a vertical liquid receiver which is fixedly secured bridging one of the headers of the condenser section and one of the headers of the subcooling section. This heat exchanger is configured such that the two headers of the condenser section and the two headers of the subcooling section are respectively partitioned by partition members provided in a pair of tanks which are spaced apart from each other, and that the liquid receiver includes a block having a refrigerant inflow passage which is in fluid communication with one of the headers of the condenser section and a refrigerant outflow passage which is in fluid communication with one of the headers of the subcooling section, the block being fixedly secured to one of the tanks so as to connect the two headers, and a vertical hollow cylindrical liquid receiver main body whose bottom is detachably fixed to the block. In a heat exchanger of this type, in order to improve the refrigerating performance of the refrigerant cycle, a liquid refrigerant which has been condensed in the condenser section is further cooled, or supercooled, in the subcooling section to a temperature 5 to 15°C lower than the condensation temperature.

However, the above-mentioned existing heat exchanger has the problem in that since the diameter of the liquid receiver main body is greater than the widths as measured in the air flow direction of the condensation section and the subcooling section, useless space is created when the heat exchanger is installed in the engine room. Moreover, there may be required extra parts, such as a sealant between the liquid receiver main body and the block, and a fixing member for fixedly securing the liquid receiver main body to the block, increasing the number of parts.

To cope with the above problem, a heat exchanger having the following structure had previously been developed. Specifically, the heat exchanger includes a condenser section having a pair of headers spaced apart from each other, a plurality of heat exchange tubes which are disposed between the headers so that opposite end portions of the tubes are connected to their corresponding headers, and a corrugate fin which is disposed between, and is bonded to, mutually neighboring heat exchanger tubes; a subcooling section disposed above the condenser section and having a pair of headers spaced apart from each other, a plurality of heat exchange tubes which are disposed therebetween so that opposite end portions of the tubes are connected to their corresponding headers, and a corrugate fin which is disposed between, and is bonded to, mutually neighboring heat exchanger tubes; and a gas-liquid separator section which is provided between the condenser section and the subcooling section; wherein the gas-liquid separator section includes a pair of headers which are spaced apart from each other and a single straight pipe which is disposed therebetween so that opposite end portions of the pipe are connected to their corresponding headers, the passage of the pipe having a cross sectional area greater than that of the heat exchange tubes of the condenser section and the subcooling section. This heat exchanger is configured such that the two headers of the condenser section, the two headers of the subcooling section, and the two headers of the gas-liquid separator section are respectively partitioned by partition members provided in a pair of tanks which are spaced apart from each other, and that a refrigerant flowing out of the condenser section passes through the gas-liquid separator section and enter the subcooling section (see Japanese Patent No. 3158509). However, in the heat exchanger described in the Japanese patent, since the gas-liquid separator section is constituted by a pair of headers and a single straight pipe whose passage has a cross sectional area greater than that of the heat exchange tubes of the condenser section and the subcooling section, the refrigerant which has left the condenser section flows into the straight pipe of the gas- liquid separator section at a relatively high flow rate. Therefore, the refrigerant quickly passes through the straight pipe before entering the subcooling section. This means that the gas-liquid separating effect at the gas-liquid separator section is insufficient, permitting a relatively massive gas-phase refrigerant to flow into the subcooling section, resulting in an insufficient subcooling effect at the subcooling section. In the end, the overall cooling effect of the entire refrigerant cycle is lowered.

An object of the present invention is to solve the above problem and to provide a heat exchanger which exhibits enhanced effect of gas-liquid separation in a gas-liquid separator section.

DISCLOSURE OF THE INVENTION

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

1) A heat exchanger comprising: a condenser section having a pair of headers spaced apart from each other and a plurality of heat exchange tubes which are disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers; a subcooling section having a pair of headers spaced apart from each other and a plurality of heat exchange tubes which are disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers; and a gas-liquid separator section which is provided between the condenser section and the subcooling section; and the heat exchanger being configured to allow a refrigerant to flow out of the condenser section into the subcooling section via the gas-liquid separator section, wherein the gas-liquid separator section comprises a pair of headers which are spaced apart from each other and a liquid receiving tube disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers, and the gas-liquid separator section is provided with flow rate lowering means for lowering the flow rate of a refrigerant flowing into the gas-liquid separator section.

2) A heat exchanger according to par. 1), wherein the gas-liquid separator section includes a plurality of liquid receiving tubes which are disposed at predetermined intervals.

3) A heat exchanger according to par. 1), wherein a desiccant is placed in the liquid receiving tube.

4) A heat exchanger according to par. 1), wherein the flow rate lowering means includes a porous member at a refrigerant inlet provided in either one of the headers of the gas-liquid separator section.

5) A heat exchanger according to par. 4), wherein the porous member is made of a mesh material.

6) A heat exchanger according to par. 1), wherein the flow rate lowering means has a narrow refrigerant outlet for allowing outflow of the refrigerant, the outlet being provided in either one of the headers of the gas-liquid separator section. 7) A heat exchanger according to par. 1), wherein the headers of the condenser section, the headers of the subcooling section, and the headers of the gas-liquid separator section are configured such that a pair of tanks spaced apart from each other are partitioned by partition members to provide the respective sets of headers.

8) A heat exchanger according to par. 7), wherein the width, as measured in the air passage direction, of the liquid receiving tube of the gas-liquid separator section is equal to or smaller than the width, as measured in the air passage direction, of the tank.

9) A heat exchanger according to par. 1), wherein the condenser section is provided above the gas-liquid separator section and the subcooling section is provided below the gas- liquid separator section.

10) A heat exchanger according to par. 9), wherein the flow rate lowering means includes a porous member disposed at a refrigerant inlet provided on an upper wall in either one of the headers of the gas-liquid separator section.

11) A heat exchanger according to par. 10), wherein the porous member is made of a mesh material.

12) A heat exchanger according to par. 9), wherein the flow rate lowering means has a narrow refrigerant outlet for allowing outflow of the refrigerant, the outlet being provided on a lower wall of either one of the headers of the gas-liquid separator section.

13) A heat exchanger according to par. 9), wherein either one of the headers of the gas-liquid separator section has a refrigerant inlet on an upper wall thereof, either one of the header of the gas-liquid separator section has a refrigerant outlet on a lower wall thereof, and the flow rate lowering means includes a porous member provided at the refrigerant inlet and a passage extending member which is formed so as to enclose the refrigerant outlet and which elongates the length of the passage for the refrigerant from the refrigerant inlet to the refrigerant outlet.

14) A heat exchanger according to par. 13), wherein the refrigerant inlet is provided in substantially the entire portion of the upper wall of the header of the gas-liquid separator section.

15) A heat exchanger according to par. 13), wherein the refrigerant inlet is provided on a portion of the upper wall of the header of the gas-liquid separator section.

16) A heat exchanger according to par. 13), wherein the porous member is made of a mesh material.

17) A heat exchanger according to par. 13), wherein the passage extending member includes a tubular inner member projecting upward around the refrigerant outlet, and a hollow outer member projecting upward and provided on the lower wall of the header having the refrigerant outlet so as to enclose the inner member, the hollow outer member having a closed upper end and a through hole which penetrates a lower portion of a surrounding wall thereof.

18) A heat exchanger according to par. 17), wherein the upper end of the outer member is located at a position lower than the upper wall of the header having the refrigerant outlet.

19) A heat exchanger according to par. 17), wherein the upper end of the outer member is equal in height to the upper wall of the header having the refrigerant outlet.

20) A heat exchanger according to par. 13), wherein the refrigerant inlet is provided on the upper wall of either one of the headers of the gas-liquid separator section, and the refrigerant outlet is provided on the lower wall of the other header of the gas-liquid separator section.

21) A heat exchanger according to par. 13), wherein the refrigerant inlet is provided on the upper wall of one of the header of the gas-liquid separator section, and the refrigerant outlet is provided on the lower wall of the same header of the gas-liquid separator section.

22) A heat exchanger according to par. 21), wherein resistant imparting means is provided in the liquid receiving tubes of the gas-liquid separator section.

23) A heat exchanger according to par. 22), wherein the resistant imparting means comprises a mesh and/or a filter.

24) A heat exchanger according to par 21), wherein the other header of the gas-liquid separator section has a pressure-reducing hole on a lower wall thereof, the hole communicating with one of the headers of the subcooling section.

25) A heat exchanger according to par. 9), wherein the headers of the condenser section, the headers of the subcooling section, and the headers of the gas-liquid separator section are configured such that a pair of tanks spaced apart from each other are partitioned by partition members to provide the respective sets of headers, and the partition members between the gas-liquid separator section and the condenser section are upper walls for the headers of the gas-liquid separator section, and the partition members between the gas-liquid separator section and the subcooling section are lower walls for the headers of the gas-liquid separator section.

26) A heat exchanger according to par. 25), wherein the width, as measured in the air passage direction, of the liquid receiving tube of the gas-liquid separator section is equal to or smaller than the width, as measured in the air passage direction, of the tank.

In the heat exchanger of par. 1) or 2), the gas-liquid separator section includes a pair of headers spaced apart from each other and liquid receiving tubes which are disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers, and the gas-liquid separator section is provided with flow rate lowering means for lowering the flow rate of a refrigerant flowing into the gas-liquid separator section. Therefore, the flow rate of the refrigerant moving from the condenser section into the gas-liquid separator section is lowered, prolonging the time required for the refrigerant to pass therethrough to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section. As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle.

With the heat exchanger of par. 3), moisture contained in a refrigerant can be removed.

In the heat exchanger of any one of pars. 4) to 6) , the flow rate lowering means has a relatively simple structure.

With the heat exchanger of par. 7) , the number of the parts of the entire device is reduced.

With the heat exchanger of par. 8), since the liquid receiving tubes never protrude from the tanks as viewed in the air flow direction, useless space can be eliminated when the heat exchanger is placed in an engine room.

In the heat exchanger of par. 9), the gas-liquid separator section includes a pair of headers spaced apart from each other and liquid receiving tubes which are disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers, and the gas-liquid separator section is provided with flow rate lowering means for lowering the flow rate of a refrigerant flowing into the gas-liquid separator section. Therefore, the flow rate of the refrigerant moving from the condenser section into the gas-liquid separator section is lowered, prolonging the time required for the refrigerant to pass therethrough to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section. As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle.

In the heat exchanger of any one of pars. 10) to 12), the flow rate lowering means has a relatively simple structure.

With the heat exchanger of any one of pars. 13) to 15), the gas-liquid separation effect in the gas-liquid separator section is further enhanced.

With the heat exchanger of par. 16), cost for the porous member is low.

In the heat exchanger of any one of pars. 17) to 19), the passage extending member has a relatively simple structure.

With the heat exchanger of par. 22), the quantity of refrigerant charged into a refrigerating cycle including the heat exchanger can be made relatively small.

That is, in the case of a heat exchanger in which a refrigerant inlet is formed in the upper wall of one of the headers of the gas-liquid separator section, and a refrigerant outlet is formed in the lower wall of the same header, if no resistant imparting means is provided in the liquid receiving tubes, immediately after flowing into the one header via the refrigerant inlet, the refrigerant flows into the liquid receiving tubes, and then flows into the other header. Therefore, it becomes difficult for the refrigerant to flow into the subcooling section via the refrigerant outlet unless a large quantity of the refrigerant is accumulated in the liquid receiving tubes and the other header. Accordingly, the quantity of refrigerant charged into the refrigeration cycle required to reach a steady region where a constant degree of subcooling is attained must be increased. In contrast, when resistant imparting means is provided in the liquid receiving tubes of the gas-liquid separator section, by the action of the resistant imparting means, it becomes difficult for the refrigerant having flown into the one header via the refrigerant inlet to flow into the liquid receiving tubes and to flow into the other header via the liquid receiving tubes. Thus, it becomes easier for the refrigerant having flown into the one header via the refrigerant inlet to flow into the subcooling section via the refrigerant outlet. Accordingly, the quantity of refrigerant charged into the refrigeration cycle required to reach a steady region where a constant degree of subcooling is attained becomes relatively small.

With the heat exchanger of par. 23), the cost for the resistant imparting means decreases.

In the heat exchanger of par. 24), due to the presence of the pressure-reducing hole, the pressure in one of the headers where neither the refrigerant inlet nor the refrigerant outlet is formed is decreased, and therefore, the liquid-phase refrigerant can easily be accumulated in the liquid receiver, whereby the gas-liquid separation effect in the gas-liquid separator section is enhanced.

With the heat exchanger of par. 25), the number of the parts of the entire device is reduced.

With the heat exchanger of par. 26), the liquid receiving tubes never protrude from the tanks as viewed in the air flow direction, useless space can be eliminated when the heat exchanger is placed in an engine room.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view showing the entire structure of a heat exchanger of Embodiment 1 of the present invention. FIG. 2 is an enlarged fragmentary vertical sectional view showing a portion of the heat exchanger shown in FIG. 1. FIG. 3 is an exploded perspective view showing, on an enlarged scale, the second header of the gas-liquid separator section of the heat exchanger shown in FIG. 1. FIG. 4 is a graph showing the results of an experiment performed by the use of a product A of the present invention as shown in FIG. 1 and a referential device. FIG. 5 is an enlarged fragmentary vertical sectional view showing a portion of a heat exchanger of Embodiment 2 of the present invention. FIG. 6 is an enlarged fragmentary vertical sectional view showing a portion of a heat exchanger of Embodiment 3 of the present invention. FIG. 7 is a perspective view showing the passage extending member for a heat exchanger as shown in FIG. 6. FIG. 8 is a front elevational view showing the entire structure of a heat exchanger of Embodiment 4 of the present invention. FIG. 9 is an enlarged fragmentary vertical sectional view showing a portion of the heat exchanger shown in FIG. 8. FIG. 10 is an enlarged fragmentary vertical sectional view showing a portion of a heat exchanger of Embodiment 5 of the present invention. FIG. 11 is a perspective view showing the passage extending member for a heat exchanger as shown in FIG. 10. FIG. 12 is an enlarged fragmentary vertical sectional view showing a portion of a heat exchanger of Embodiment 6 of the present invention. FIG. 13 is an enlarged fragmentary vertical sectional view showing a portion of a heat exchanger of Embodiment 7 of the present invention. FIG. 14 is a graph showing the results of an experiment performed by the use of a product B of the present invention as shown in FIG. 13 and a referential device.

BEST MODE FOR CARRYING OUT THE INVENTION

Several embodiments of the present invention will next be described with reference to the accompanying drawings in which the same reference numerals are used throughout the drawings to refer to similar parts or elements for the sake of concise description.

In the following description, the term "aluminum" encompasses not only pure aluminum but also aluminum alloys. Also, in the following description, the right and left of FIG. 1 and FIG. 8 will be referred to as "right" and "left," W

respectively, and the backside of the sheets of FIG. 1 and FIG. 8 (the downstream side of air flow) will be referred to as "front," and the opposite side as "rear." Embodiment 1

This embodiment is shown in FIG. 1 to FIG. 3.

FIG. 1 shows the entire structure of this embodiment and FIG. 2 and FIG. 3 show essential portions of the structure.

In FIG. 1 and FIG. 2, the heat exchanger (1) has a condenser section (2) and a subcooling section (3) on a common vertical plane, so that the two sections are spaced apart in the upper-lower relation, with the condenser section (2) being on the upper side. The heat exchanger (1) also has a gas-liquid separator section (4) between the condenser section (2) and the subcooling section (3). A refrigerant outflows from the condenser section (2), enters the gas- liquid separator section (4), passes all the way through the gas-liquid separator section (4), and flows into the subcooling section (3).

The condenser section (2) includes a first and a second aluminum headers (5) and (6), a plurality of flat aluminum heat exchange tubes (7), and aluminum corrugate fins (8), wherein the headers (5) and (6) extend vertically and are spaced apart from each other in parallel in the left-right direction; the heat exchange tubes (7) are disposed between the two headers (5) and (6) at predetermined intervals in the vertical direction, with their width being oriented in the front-rear direction and opposite end portions of the tubes being connected to their corresponding headers (5) and (6); and the corrugate fins (8) are disposed between the adjacent heat exchange tubes (7) and are brazed to the heat exchange tubes (7). An aluminum side plate (9) is disposed above the top heat exchange tube (7) with a certain space therebetween. An aluminum corrugate fin (8) is also disposed between the side plate (9) and the top heat exchange tube (7), and the corrugate fin (8) is brazed to the side plate (9) and the top heat exchange tube (7) .

The first header (5) is divided into an upper header (5a) and a lower header (5b) by a plate-shaped partition member (11) disposed at a position slightly lower than the mid point of the header in the vertical direction, and a refrigerant inlet (12) is provided at an upper end of the upper header (5a). In the condenser section (2), passage groups (13) and (14) are provided on the upper and lower sides of the partition member (11), respectively, wherein the passages in each group are defined by a plurality of heat exchange tubes (7) arranged in rows in a vertical direction. The number of the heat exchange tubes (7) in the upper passage group (13) is greater than that of the lower passage group (14). The flowing directions of the refrigerant in all the heat exchange tubes (7) in each of the passage groups (13) and (14) are identical, and the flowing direction of the refrigerant in the passage group (13) and that of the passage group (14) are opposite to each other. The subcooling section (3) includes a first and a second aluminum headers (15) and (16), a plurality of flat aluminum heat exchange tubes (17), and aluminum corrugate fins (18), wherein the headers (15) and (16) extend vertically and are spaced apart from each other in the left- right direction; the heat exchange tubes (17) are disposed between the two headers (15) and (16) at predetermined intervals in the vertical direction, with their width being oriented in the front-rear direction and opposite end portions of the tubes being connected to their corresponding headers (15) and (16); and the corrugate fins (18) are disposed between adjacent heat exchange tubes (17) and are brazed to the heat exchange tubes (17). The first header (15) has a refrigerant outlet (20). The heat exchange tubes (17) are identical to those of the condenser section (2). An aluminum side plate (19) is disposed below the bottom heat exchange tube (17) with a certain space therebetween. An aluminum corrugate fin (18) is also disposed between the side plate (19) and the bottom heat exchange tube (17), and the corrugate fin (18) is brazed to the side plate (19) and the bottom heat exchange tube (17).

The gas-liquid separator section (4) includes a first and a second aluminum headers (21) and (22) and a plurality of two in this embodiment aluminum liquid receiving tubes (23), wherein the headers (21) and (22) extend vertically and are spaced apart from each other in parallel in the left-right direction; the liquid receiving tubes (23) are disposed between the two headers (21) and (22) at predetermined intervals in the vertical direction, with opposite end portions of the tubes being connected to their corresponding headers (21) and (22). The liquid receiving tubes (23) are cylindrical tubes having outer diameters equal to or smaller than the width, as measured in the front-rear direction, of the header (21) and (22). No particular limitation is imposed on the cross-sectional shape of the liquid receiving tubes (23), so long as the width in the front-rear direction is equal to or smaller than the width of the headers (21) and (22) in the front-rear direction, and therefore, square tubes or tubes of any other shape may be used other than cylindrical tubes. The cross-sectional area of the passage of each liquid receiving tube (23) is larger than the cross-sectional area of the passage of each of the heat exchanger tubes (7) and (17). A desiccant (24) is placed in the lower liquid receiving tube (23). The corrugate fins (8) and (18) are also disposed between the upper liquid receiving tube (23) and the lowest heat exchange tube (7) of the condenser section (2), as well as the lower liquid receiving tube (23) and the highest heat exchange tube (17) of the subcooling section (3), and are brazed to the liquid receiving tubes (23) and the heat exchange tubes (7) and (17).

A pair of tanks (25) and (26) which extend vertically and are spaced apart from each other in the left-right direction are partitioned by partition members (27), (28), (29), and (30) to provide the two headers (5) and (6) of the condenser section (2), the two headers (21) and (22) of the gas-liquid separator section (4), and the two headers (15) and (16) of the subcooling section (3). Specifically, the partition members (27) and (29) between the condenser section (2) and the gas-liquid separator section (4) are upper walls (21a) and (22a) for the headers (21) and (22) of the gas- liquid separator section (4); and the partition members (28) and (30) between the gas-liquid separator section (4) and the subcooling section (3) are lower walls (21b) and (22b) for the headers (21) and (22) of the gas-liquid separator section (4). A refrigerant inlet (32) is provided all over the upper wall (21a), excepting the peripheral portion thereof, of the first header (21) of the gas-liquid separator section (4). Similarly, a refrigerant outlet (33) which is much narrower as compared with the refrigerant inlet (32) is provided in the lower walls (22b), at a position somewhat close to the outer wall of the second header (22).

The refrigerant flows through the refrigerant inlet

(12) into the upper header (5a) of the first header (5) of the condenser section (2), then through the upper passages

(13) into the second header (6), and subsequently flows into the lower header (5b) of the first header (5) through the lower passages (14). The refrigerant which has entered the lower header (5b) passes through the refrigerant inlet (32) and flows into the first header (21) of the gas-liquid separator section (4), where the refrigerant is pooled. Specifically, the refrigerant is accumulated in the headers (21) and (22) and the liquid receiving tubes (23) of the gas- liquid separator section (4), and then flows into the second header (16) of the subcooling section (3) via the refrigerant outlet (33). The refrigerant, which has entered the second header (16), flows into the first header (15) through the heat exchange tubes (17), and outflows through the refrigerant outlet (20).

The gas-liquid separator section (4) includes flow rate lowering means for lowering the flow rate of a refrigerant which outflows from the condenser section (2) into the gas- liquid separator section (4). The flow rate lowering means includes a mesh material (34) serving as the mentioned porous member and spread across the refrigerant inlet (32) formed in the upper wall (21a) of the first header (21), and a passage extending member (35) provided in the second header (22) so as to enclose the refrigerant outlet (33) and to extend the length of the passage through which the refrigerant moves from the refrigerant inlet (32) to the refrigerant outlet (33).

The passage extending member (35) includes an aluminum tubular inner member (36) and an aluminum hollow outer member (37), wherein the aluminum tubular inner member (36) projecting upward is provided on the lower wall (22b) so as to establish a fluid communication with the refrigerant outlet (33), and the aluminum hollow outer member (37) projecting upward is provided on the lower wall (22b) so as to enclose the inner member (36), with the top being closed and a through hole (38) being provided at the lower end of the surrounding wall (37a). The lower end of the inner member (36) is inserted into the refrigerant outlet (33) and fixedly secured to the lower wall (22b). As shown in FIG. 3, the outer member (37) includes a surrounding wall (37a) and a top plate (37b), wherein the surrounding wall (37a), formed integral with the lower wall (22b); i.e., the partition member (30), projects upward and has a semicircle cross section, and the top plate (37b) is formed at the top of the surrounding wall (37a) so as to be integrated therewith and closes the top opening. The through hole (38) is provided at a lower portion of the flat wall of the surrounding wall (37a). The height of the upper end of the outer member (37) is lower than that of the upper wall (22a) of the second header (22). The passage extending member (35), together with the partition member (30), is housed in the right-side tank (26) through a through hole (39) defined in the surrounding wall of the right-side tank (26) and brazed to thereto.

When the aforementioned heat exchanger (1) is assembled with a compressor, a decompressor (an expansion valve) , and an evaporator, a refrigerating cycle is realized. A refrigerating cycle of this type is used as an air conditioner for a vehicle, such as an automobile.

In the aforementioned heat exchanger (1) , when the refrigerant flows through the lower header (5b) of the first header (5) of the condenser section (2), then through the refrigerant inlet (32) into the first header (21) of the gas- liquid separator section (4), the flow rate of the refrigerant is lowered due to the presence of the mesh material (34). The refrigerant, after having passed through the liquid receiving tubes (23) to enter the second header (22), is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and (22) and liquid receiving tubes (23). Subsequently, the refrigerant flows into the second header (16) of the subcooling section (3) through the refrigerant outlet (33). At this time, the flow rate of the refrigerant is again lowered because the refrigerant flows into the outer member (37) through the through hole (38) of the passage extending member (35), flows upward in the outer member (37) then enters the inner member (36) via the top opening thereof and flows out to the second header (16) of the subcooling section (3) through the refrigerant outlet (33). Therefore, the flow rate of the refrigerant moving from the condenser section (2) into the gas-liquid separator section (4) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section (4). As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle.

Next will be described an experiment performed by use of a heat exchanger (1) having the above-described structure (hereinafter called the product A of the present invention), in comparison with a referential example.

Dimensions of respective parts of the product A of the present invention are as follows. The condenser section (2) has a height of 290 mm, a width as measured in the left-right direction of 570 mm, and a depth as measured in the front- rear direction of 16 mm. The number of the heat exchange tubes (7) of the condenser section (2) is 28, and the total cross-sectional area of all the heat exchange tubes (7) is 367 mm². The subcooling section (3) has a height of 60 mm, a width as measured in the left-right direction of 570 mm, and a depth as measured in the front-rear direction of 16 mm. The number of the heat exchange tubes (17) of the subcooling section (3) is 5, and the total cross-sectional area of all heat exchange tubes (17) is 65 mm². The inner diameter of the liquid receiving tube (23) is 13.5 mm, and the outer diameter thereof is 15.9 mm.

Separately, the following heat exchanger was provided as a referential product. It includes a condenser section having a pair of headers spaced apart from each other, a plurality of heat exchange tubes which are disposed between the headers so that opposite end portions of the tubes are connected to their corresponding headers, and a corrugate fin which is disposed between, and is bonded to, mutually neighboring heat exchanger tubes; a subcooling section having a pair of headers spaced apart from each other, a plurality of heat exchange tubes which are disposed therebetween so that opposite end portions of the tubes are connected to their corresponding headers, and a corrugate fin which is disposed between, and is bonded to, mutually neighboring heat exchanger tubes; and a vertical liquid receiver which is fixedly secured bridging one of the headers of the condenser section and one of the headers of the subcooling section. This referential heat exchanger is configured such that the two headers of the condenser section and the two headers of the subcooling section are respectively partitioned by partition members provided in a pair of tanks which are spaced apart from each other, and that the liquid receiver includes a block having a refrigerant inflow passage which is in fluid communication with one of the headers of the condenser section and a refrigerant outflow passage which is in fluid communication with one of the headers of the subcooling section, the block being fixedly secured so as to connect the two headers, and a vertical hollow cylindrical liquid receiver main body whose bottom is detachably fixed to the block. In the referential heat exchanger, the heat exchange tubes for the condenser section and the subcooling section are of the same type as those used in the product A of the present invention. Also, the size of the condenser section, the number of the exchanging tubes of the condenser section, the total cross-sectional area of all the heat exchange tubes of the condenser section, the size of the subcooling section, the number of the exchanging tubes of the subcooling section, and the total cross-sectional area of all the heat exchange tubes of the subcooling section of the referential heat exchanger are respectively identical to those of the product A of the present invention. Evaluation test 1

A refrigerating cycle was constructed using the product A of the present invention, a compressor, an expansion valve, and an evaporator. Similarly, a comparative refrigerating cycle was also constructed using the above referential product instead of the product A of the present invention. Initially, a predetermined amount of a refrigerant (850 g) was introduced into each of the refrigerating cycles, whereby operation was started. While adding the refrigerant, degree of subcooling was plotted at several points in refrigerant charge. The results are shown in FIG. 4. In the graph shown in FIG. 4, points indicated by A are the start points of subcooling of the refrigerant flowing out of the product A of the present invention or the referential device, points indicated by B are the points at which a liquid-state refrigerants started to be accumulated in the gas-liquid separator section of the product A of the present invention or in the liquid receiver of the referential device, points indicated by C are the points at which the gas-liquid separator sections of the product A of the present invention or the liquid receiver of the referential device has been filled with the liquid refrigerant. The span of the steady zone at which a constant level of subcooling has been attained with the product A of the present invention is equivalent to that as found when the referential device was employed, proving that the product A of the present invention has sufficient performance as a heat exchanger of this type. Embodiment 2

This embodiment is shown in FIG. 5.

In a heat exchanger (40) of this embodiment, flow rate lowering means which is provided in a gas-liquid separator section (4) and lowers the flow rate of a refrigerant flowing out of a condenser section (2) to enter the gas-liquid separator section (4) includes a mesh material (34) which serves as a porous member and a narrow refrigerant outlet (41). The mesh material (34) is spread across the refrigerant inlet (32) formed in an upper wall (21a) of the first header (21). The narrow refrigerant outlet (41) is formed at a central portion of a lower wall (22b) of a second header (22). The size of the narrow refrigerant outlet (41) is smaller than the refrigerant outlet (33) of the heat exchanger (1) of Embodiment 1.

Except for the above changes, the heat exchanger of this embodiment is substantially identical to that of Embodiment 1.

In the heat exchanger (40) of Embodiment 2, when the refrigerant flows through a lower header (5b) of a first header (5) of the condenser section (2), then through the refrigerant inlet (32) into the first header (21) of the gas- liquid separator section (4), the flow rate of the refrigerant is lowered due to the presence of the mesh material (34). The refrigerant, after having passed through the liquid receiving tubes (23) to enter the second header (22), is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and (22) and liquid receiving tubes (23), and then flows into a second header (16) of a subcooling section (3). At this time, the flow rate of the refrigerant is again lowered because the refrigerant flows out to the second header (16) of the subcooling section (3) through the narrow refrigerant outlet (41). Therefore, the flow rate of the refrigerant flowing into the gas-liquid separator section (4) from the condenser section (2) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separation effect in the gas-liquid separation section. As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle. Embodiment 3

This embodiment is shown in FIGS. 6 and 7.

In a heat exchanger (45) of this embodiment, a refrigerant inlet (32) is defined in an area corresponding to an approximately inner half of an upper wall (21a) of a first header (21) of a gas-liquid separator section (4). Flow rate lowering means which is provided in the gas-liquid separator section (4) and lowers the flow rate of a refrigerant flowing out of the condenser section (2) to enter the gas-liquid separation (4) includes a mesh material (34) serving as the mentioned porous member and spread across the refrigerant inlet (32) formed in the upper wall (21a) of the first header (21), and a passage extending member (46) provided in the second header (22) so as to enclose the refrigerant outlet (33) and to extend the length of the passage through which the refrigerant moves from the refrigerant inlet (32) to the refrigerant outlet (33).

A passage extending member (46) includes an aluminum tubular inner member (47) and an aluminum hollow outer member (48), wherein the aluminum tubular inner member (47) projecting upward is provided on the lower wall (22b) so as to establish a fluid communication with the refrigerant outlet (33), and the aluminum hollow outer member (48) projecting upward is provided on the lower wall (22b) so as to enclose the inner member (47), with the top being closed and a through hole (49) being provided at the lower end of the surrounding wall (48a). The lower end of the inner member (47) is inserted into the refrigerant outlet (33) and fixedly secured to the lower wall (22b). As shown in FIG. 7, the outer member (48) is configured such that the outer member (37) of the heat exchanger (1) of Embodiment 1 is extended upward and integrally formed with an upper wall (22a) of the second header (22); i.e., a partition member (29). The upper wall (22a) functions as a top plate (48b) that closes the top opening of a surrounding wall (48a) of the outer member (48). Therefore, the upper end of the outer member (48) is at a position equal in height to the upper wall (22a) of the second header (22). The passage extending member (46), together with upper and lower partition members (29) and (30), is housed in the right-side tank (26) through a through hole (39) defined in the surrounding wall of the right-side tank (26) and brazed to thereto.

In the heat exchanger (45) of Embodiment 3, when the refrigerant moves from a lower header (5b) of a first header (5) of the condenser section (2), through the refrigerant inlet (32), into the first header (21) of the gas-liquid separator section (4) , the flow rate of the refrigerant is lowered due to the presence of the mesh material (34). The refrigerant, after having passed through the liquid receiving tubes (23) to enter the second header (22), is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and (22) and liquid receiving tubes (23). Subsequently, the refrigerant flows into the second header (16) of the subcooling section (3) through the refrigerant outlet (33). At this time, the flow rate of the refrigerant is again lowered because the refrigerant flows into the outer member (48) through the through hole (49) of the passage extending member (46), flows upward in the outer member (48) then enters the inner member (47) via the top opening thereof and flows out to the second header (16) of the subcooling section (3) through the refrigerant outlet (33). Therefore, the flow rate of the refrigerant moving from the condenser section (2) into the gas-liquid separator section (4) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section (4). As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle. Embodiment 4

This embodiment is shown in FIGS. 8 and 9.

In a heat exchanger (50) of this embodiment, a first header (15) of a subcooling section (3) is partitioned into an upper header (15a) and a lower header (15b) by a plate- shaped partition member (51) disposed at about the vertically mid point of the header (15), and a refrigerant outlet (20) is provided in the lower header (15b). In a subcooling section (3), passage groups (52) and (53) are provided on the upper and lower sides of the partition member (51), respectively, wherein the passages in each group are defined by a plurality of heat exchange tubes (17) arranged in rows in a vertical direction. The number of the heat exchange tubes (7) in the upper passage group (13) is greater than that of the lower passage group (14). The flowing directions of the refrigerant in all the heat exchange tubes (17) in each of the passage groups (52) and (53) are identical, and the flowing direction of the refrigerant in the passage group (52) and that of the passage group (53) are opposite to each other.

A refrigerant outlet (33) is provided on a lower wall (21b) close to the outer wall of a first header (21) of a gas-liquid separator section (4).

The refrigerant flows through the refrigerant inlet

(13) into the second header (6), and subsequently flows into the lower header (5b) of the first header (5) through the lower passages (14). The refrigerant which has entered the lower header (5b) passes through the refrigerant inlet (32) and flows into the first header (21) of the gas-liquid separator section (4), where the refrigerant is pooled. Specifically, the refrigerant is accumulated in the headers (21) and (22) and the liquid receiving tubes (23) of the gas- liquid separator section (4), and then flows into the upper header (15a) of the first header (15) of the subcooling section (3) via the refrigerant outlet (33). The refrigerant, which has entered the upper header (15a) of the first header (15), flows into a second header (16) through the upper passage group (52), and then to the lower header (15b) of the first header (5) through the lower passage group (53). Subsequently, the refrigerant flows into the lower header (15b) of the first header (5) through the lower passage group (53), and flows out from a refrigerant outlet (20).

Flow rate lowering means which is provided in the gas- liquid separator section (4) and lowers the flow rate of a refrigerant flowing out of the condenser section (2) to enter the gas-liquid separation (4) includes a mesh material (34) serving as the mentioned porous member and spread across the refrigerant inlet (32) formed in the upper wall (21a) of the first header (21), a passage extending member (35) provided in the first header (21) so as to enclose the refrigerant outlet (33) and to extend the length of the passage through which the refrigerant moves from the refrigerant inlet (32) to the refrigerant outlet (33), and a pressure-reducing hole (54) which is provided in a central portion of a lower wall (22b) of the second header (22) so as to be in fluid communication with the second header (16) of the subcooling section (3) .

The passage extending member (35) is similar to the passage extending member (35) of Embodiment 1, except that the right and left sides are reversed. An outer member (37) is integrally formed with partition members (27) and (28), rather than with partition members (29) and (30). The lower end of an inner member (36) is inserted into the refrigerant outlet (33) which is defined in a lower wall (21b); i.e., the partition member (28), and fixed to the lower wall (21b). The upper end of the outer member (37) is located lower than the upper wall (21a) of the first header (21). The passage extending member (35), together with the partition member (28), is housed in the left-side tank (25) through a through hole (55) defined in the surrounding wall of the left-side tank (25) and brazed to thereto.

In the heat exchanger (50) of Embodiment 4, when the refrigerant moves from a lower header (5b) of a first header (5) of the condenser section (2), through the refrigerant inlet (32), into the first header (21) of the gas-liquid separator section (4), the flow rate of the refrigerant is lowered due to the presence of the mesh material (34). The refrigerant is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and (22) and liquid receiving tubes (23). Subsequently, the refrigerant flows into the upper header (15a) of the first header (15) of the subcooling section (3) through the refrigerant outlet (33). At this time, the flow rate of the refrigerant is again lowered because the refrigerant flows into the outer member (37) through the through hole (38) of the passage extending member (35), flows upward in the outer member (37) then enters the inner member (36) via the top opening thereof and flows out to the upper header (15a) of the first header of the subcooling section (3) through the refrigerant outlet (33). Therefore, the flow rate of the refrigerant moving from the condenser section (2) into the gas-liquid separator section (4) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section (4). As the quantity of the refrigerant flowing into the gas-liquid separator section (4) increases, the pressure in the second header (22) of the gas-liquid separator section (4) rises, and accordingly, there may be the risk that the refrigerant flowing into the first header (21) goes through passage extending member (35) directly without flowing into the second header (22) and flows out to the upper header (15a) of the first header of the subcooling section (3) through the refrigerant outlet (33). However, because the refrigerant in the second header (22) flows out to the second header (16) of the subcooling section (3) through a pressure-reducing hole (54) and thus the pressure in the second header (22) is lowered, the refrigerant surely flows into the second header (22). Therefore, the residence time of the refrigerant in the gas-liquid separator section (4) will not be shortened, improving the gas-liquid separation effect in the gas-liquid separation section (4). As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle. Incidentally, a small quantity of a vapor-phase refrigerant migrates into the refrigerant which flows out of the second header (22) of the gas-liquid separator section (4) into the second header (16) of the subcooling section (3) through the pressure-reducing hole (54), but its quantity is so small that the refrigerant is surely condensed and subcooled in the subcooling section (3). Embodiment 5

This embodiment is shown in FIGS. 10 and 11.

In a heat exchanger (60) of this embodiment, a refrigerant inlet (32) is defined in an area corresponding to an approximately inner half of an upper wall (21a) i.e., a partition member (27) of a first header (21) of a gas- liquid separator section (4). Flow rate lowering means which is provided in the gas-liquid separator section (4) and lowers the flow rate of a refrigerant flowing out of the condenser section (2) to enter the gas-liquid separation (4) includes a mesh material (34) serving as the mentioned porous member and spread across the refrigerant inlet (32) formed in the upper wall (21a) of the first header (21), and a passage extending member (46) provided in the first header (21) so as to enclose the refrigerant outlet (33) and to extend the length of the passage through which the refrigerant moves from the refrigerant inlet (32) to the refrigerant outlet (33).

As shown in FIG. 11, the passage extending member (46) is similar to the passage extending member (46) of Embodiment 3, except that the right and left sides are reversed. An outer member (48) is integrally formed with partition members (27) and (28), rather than with partition members (29) and (30). The lower end of an inner member (47) is inserted into the refrigerant outlet (33) which is defined in the partition member (28), and fixed to the lower wall (21b). The outer part of the partition member (27); i.e., the upper wall (21a), is also a top plate (48b) that closes the top opening of a surrounding wall (48a) of the outer member (48). The refrigerant inlet (32) is formed so as to protrude inward from a flat wall of the surrounding wall (48a) of the partition member (27); i.e., the upper wall (21a). Accordingly, the upper end of the outer member (48) is on the same level with the upper wall (21a) of the first header (21). The passage extending member (46), together with upper and lower partition members (27) and (18), is housed in the leftside tank (25) through a through hole (55) defined in the surrounding wall of the left-side tank (25) and brazed to thereto.

Except for the above changes, the heat exchanger of this embodiment is substantially identical to the heat exchanger (50) of Embodiment 4.

In the heat exchanger (60) of Embodiment 5, when the refrigerant moves from a lower header (5b) of a first header (5) of the condenser section (2), through the refrigerant inlet (32), into the first header (21) of the gas-liquid separator section (4), the flow rate of the refrigerant is lowered due to the presence of the mesh material (34). The refrigerant is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and (22) and liquid receiving tubes (23). Subsequently, the refrigerant flows into the upper header (15a) of the first header (15) of the subcooling section (3) through the refrigerant outlet (33). At this time, the flow rate of the refrigerant is again lowered because the refrigerant flows into the outer member (48) through the through hole (49) of the passage extending member (46), flows upward in the outer member (48) then enters the inner member (47) via the top opening thereof and flows out to the upper header (15a) of the first header of the subcooling section (3) through the refrigerant outlet (33). Therefore, the flow rate of the refrigerant moving from the condenser section (2) into the gas-liquid separator section (4) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section (4). As the quantity of the refrigerant flowing into the gas-liquid separator section (4) increases, the pressure in the second header (22) of the gas-liquid separator section (4) rises, and accordingly, there may be the risk that the refrigerant flowing into the first header (21) goes through passage extending member (35) directly without flowing into the second header (22) and flows out to the upper header (15a) of the first header of the subcooling section (3) through the refrigerant outlet (33). However, because the refrigerant in the second header (22) flows out to the second header (16) of the subcooling section (3) through a pressure-reducing hole (54) and thus the pressure in the second header (22) is lowered, the refrigerant surely flows into the second header (22). Therefore, the residence time of the refrigerant in the gas-liquid separator section (4) will not be shortened, improving the gas-liquid separation effect in the gas-liquid separation section (4). As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle. Incidentally, a small quantity of a vapor-phase refrigerant migrates into the refrigerant which flows out of the second header (22) of the gas-liquid separator section (4) into the second header (16) of the subcooling section (3) through the pressure-reducing hole (54), but its quantity is so small that the refrigerant is surely condensed and subcooled in the subcooling section (3). Embodiment 6

This embodiment is shown in FIG. 12.

In a heat exchanger (65) of this embodiment, a pressure-reducing hole is not provided on a lower wall (22b) of a second header (22) of a gas-liquid separator section (4).

Except for the above changes, the heat exchanger of this embodiment is substantially identical to that of Embodiment 5.

In the heat exchanger of Embodiment 6, when the refrigerant moves from a lower header (5b) of a first header (5) of the condenser section (2), through the refrigerant inlet (32), into the first header (21) of the gas-liquid separator section (4), the flow rate of the refrigerant is lowered due to the presence of the mesh material (34). The refrigerant is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and (22) and liquid receiving tubes (23). Subsequently, the refrigerant flows into the upper header (15a) of the first header (15) of the subcooling section (3) through the refrigerant outlet (33). At this time, the flow rate of the refrigerant is again lowered because the refrigerant flows into the outer member (48) through the through hole (49) of the passage extending member (46), flows upward in the outer member (48) then enters the inner member (47) via the top opening thereof and flows out to the upper header (15a) of the first header of the subcooling section (3) through the refrigerant outlet (33). Therefore, the flow rate of the refrigerant moving from the condenser section (2) into the gas-liquid separator section (4) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separating effect in the gas-liquid separator section (4). As a result, the quantity of the vapor-phase refrigerant that flows into the subcooling section (3) decreases, attaining a sufficient subcooling effect in the subcooling section (3) and improving the cooling effect of the overall refrigerating cycle. Embodiment 7

This embodiment is shown in FIG. 13.

In the case of a heater exchanger (70) according to the present embodiment, a desiccant (24) is placed in the upper liquid receiving tube (23) of the gas-liquid separator section (4). First resistance imparting means (71A) composed of a filter (72) made of nonwoven fabric and a mesh (73) superposed on one side of the filter (72) is disposed on each of the left-hand and right-hand sides of the desiccant (24) within the upper liquid receiving tube (23). Further, second resistance imparting means (71B) composed of a filter (72) made of nonwoven fabric and a mesh (73) superposed on both sides of the filter (72) is disposed at each of the left-hand and right-hand end portions of the lower liquid receiving tube (23).

A mesh having a mesh size of 120 mesh or less is used for the mesh (73) used in the resistance imparting means (71A) and (71B).

In place of at least one of the two first resistance imparting means (71A) disposed within the upper liquid receiving tube (23), the second resistance imparting means (71B) may be disposed. The first resistance imparting means (71A) or the second resistance imparting means (71B) may be disposed on only one side of the desiccant (24) within the upper liquid receiving tube (23).

In place of at least one of the two second resistance imparting means (71B) disposed within the lower liquid receiving tube (23), the first resistance imparting means (71B) may be disposed. The first resistance imparting means (71A) or the second resistance imparting means (71B) may be disposed at only one end portion of the lower liquid receiving tube (23).

Notably, in the above, the combination of the filter (72) and the mesh (73) superposed together is used for the resistance imparting means (71A) and (71B). However, the present invention is not limited thereto, and resistance imparting means composed of only one of the filter (72) and the mesh (73) may be used in some cases.

In the case where a refrigerant inlet (32) is formed in the upper wall (21a) of the first header (21) of the gas- liquid separator section (4) and a refrigerant outlet (33) is formed in the lower wall (21b) of the first header (21) as in the heat exchanger (70) of Embodiment 7, if the resistance imparting means (71A) and (71B) are provided within the liquid receiving tubes (23) of the gas-liquid separator section (4), refrigerant flows as follows at the time of charging of the refrigerant into the refrigeration cycle because of the action of the resistance imparting means (71A) and (71B). That is, it becomes difficult for the refrigerant having flown into the first header (21) via the refrigerant inlet (32) to flow into the liquid receiving tubes (23), and to flow into the second header (22) via the liquid receiving tubes (23). As a result, it becomes easier for the refrigerant having flown into the first header (21) via the refrigerant inlet (32) to flow into the upper header (15a) of the subcooling section (3) via the refrigerant outlet (33). Accordingly, the quantity of refrigerant charged into the refrigeration cycle required to reach a steady region where a constant degree of subcooling is attained becomes relatively small.

In addition, in the heat exchanger (70) of Embodiment 7, when the refrigerating cycle is operated, the refrigerant flows from the lower header (5b) of the first header (5) of the condenser section (2) into the first header

(21) of the gas-liquid separator section (4) via the refrigerant inlet (32). At that time, the flow rate of the refrigerant is lowered by the action of the mesh (34). Further, the refrigerant is accumulated in the gas-liquid separator section (4), specifically in the headers (21) and

(22) and the liquid receiving tubes (23), and then flows into the upper heard (15a) of the first header (15) of the subcooling section (3) via the refrigerant outlet (33). At this time, the refrigerant enters the interior of the outer member (48) via the through hole (49) of the passage extending member (46), flows upward within the outer member (48), enters the interior of the inner member (47) via an upper end opening thereof, passes through the refrigerant outlet (33), and enters the upper header (15a) of the first header (15) of the subcooling section (3). Therefore, the flow rate of the refrigerant is again lowered. Therefore, the flow rate of the refrigerant flowing into the gas-liquid separator section (4) from the condenser section (2) is lowered, prolonging the time during which the refrigerant stays in the gas-liquid separator section (4) to a certain extent, thus improving the gas-liquid separation effect in the gas-liquid separation section (4). As the quantity of the refrigerant flowing into the gas-liquid separator section (4) increases, the pressure within the second header (22) of the gas-liquid separator section (4) increases. In such a case, without flowing into the second header (22), the refrigerant having flown into the first header (21) may pass directly through the passage extending member (46), and flow into the upper header (15a) of the first header (15) of the subcooling section (3) via the refrigerant outlet (33). However, since the refrigerant in the second header (22) flows into the second header (16) of the subcooling section (3) via the pressure-decreasing hole (54), the pressure in the second header (22) is lowered, and the refrigerant flows into the second header (22) without fail. As a result, it becomes possible to prevent shortening of the time during which the refrigerant stays in the gas-liquid separator section (4) and to improve the gas-liquid separation effect in the gas-liquid separation section (4). Accordingly, the quantity of gas-phase refrigerant flowing into the subcooling section (3) decrease, and a sufficient level of subcooling effect is attained at the subcooling section (3), whereby the cooling effect of the entire refrigerating cycle is improved. Notably, although the refrigerant which flows from the second header (22) of the gas-liquid separation section (4) into the second header (16) of the subcooling section (3) via the pressure-decreasing hole (54) contains a small amount of gas- phase refrigerant, this gas-phase refrigerant is liquefied and subcooled at the subcooling section (3) because its amount is small.

Next will be described an experiment performed by use of the heat exchanger (70) having the above-described structure (hereinafter called the product B of the present invention), in comparison with a referential example.

The size of the condenser section (2), the number of the heat exchange tubes (7), the total cross-sectional area of all the heat exchange tubes (7) , the size of the subcooling section (3), the number of the heat exchange tubes (17), the total cross-sectional area of all the heat exchange tubes (17), and the inner and outer diameters of the liquid receiving tube (23) of the gas-liquid separation section (4) of the product B of the present invention are the same as those of the product A of the present invention.

Notably, the referential device is identical with the referential device used in the above-described Evaluation test 1. In the referential device, the heat exchange tubes for the condenser section and the subcooling section are of the same type as those used in the product B of the present invention. Also, the size of the condenser section, the number of the exchanging tubes of the condenser section, the total cross-sectional area of all the heat exchange tubes of the condenser section, the size of the subcooling section, the number of the exchanging tubes of the subcooling section, and the total cross-sectional area of all the heat exchange tubes of the subcooling section of the referential heat exchanger are respectively identical to those of the product B of the present invention. Evaluation test 2

A charge graph was made by use of the product B of the present invention and the referential device in the same manner as in the above-mentioned Evaluation test 1. The results are shown in FIG. 14. In the graph shown in FIG. 4, points indicated by A are the start points of subcooling of the refrigerant flowing out of the product B of the present invention or the referential device, points indicated by B are the points at which a liquid-state refrigerant started to be accumulated in the gas-liquid separator section of the product B of the present invention or in the liquid receiver of the referential device, points indicated by C are the points at which the gas-liquid separator section of the product B of the present invention or the liquid receiver of the referential device has been filled with the liquid refrigerant. The span of the steady zone at which a constant level of subcooling has been attained with the product B of the present invention is equivalent to that as found when the referential device was employed, proving that the product B of the present invention has sufficient performance as a heat exchanger of this type.

INDUSTRIAL APPLICABILITY

The heat exchanger according to the present invention is preferably used in a refrigeration cycle which constitutes a car air conditioner, for example.

Claims

1. A heat exchanger comprising: a condenser section having a pair of headers spaced apart from each other and a plurality of heat exchange tubes which are disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers; a subcooling section having a pair of headers spaced apart from each other and a plurality of heat exchange tubes which are disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers; and a gas-liquid separator section which is provided between the condenser section and the subcooling section; and the heat exchanger being configured to allow a refrigerant to flow out of the condenser section into the subcooling section via the gas-liquid separator section, wherein the gas-liquid separator section comprises a pair of headers which are spaced apart from each other and a liquid receiving tube disposed therebetween, with opposite end portions of the tubes being connected to their corresponding headers, and the gas-liquid separator section is provided with flow rate lowering means for lowering the flow rate of a refrigerant flowing into the gas-liquid separator section.

2. A heat exchanger according to claim 1, wherein the gas- liquid separator section includes a plurality of liquid receiving tubes which are disposed at predetermined intervals.

3. A heat exchanger according to claim 1, wherein a desiccant is placed in the liquid receiving tube.

4. A heat exchanger according to claim 1, wherein the flow rate lowering means includes a porous member at a refrigerant inlet provided in either one of the headers of the gas-liquid separator section.

5. A heat exchanger according to claim 4, wherein the porous member is made of a mesh material.

6. A heat exchanger according to claim 1, wherein the flow rate lowering means has a narrow refrigerant outlet for allowing outflow of the refrigerant, the outlet being provided in either one of the headers of the gas-liquid separator section.

7. A heat exchanger according to claim 1, wherein the headers of the condenser section, the headers of the subcooling section, and the headers of the gas-liquid separator section are configured such that a pair of tanks spaced apart from each other are partitioned by partition members to provide the respective sets of headers.

8. A heat exchanger according to claim 7, wherein the width, as measured in the air passage direction, of the liquid receiving tube of the gas-liquid separator section is equal to or smaller than the width, as measured in the air passage direction, of the tank.

9. A heat exchanger according to claim 1, wherein the condenser section is provided above the gas-liquid separator section and the subcooling section is provided below the gas- liquid separator section.

10. A heat exchanger according to claim 9, wherein the flow rate lowering means includes a porous member disposed at a refrigerant inlet provided on an upper wall in either one of the headers of the gas-liquid separator section.

11. A heat exchanger according to claim 10, wherein the porous member is made of a mesh material.

12. A heat exchanger according to claim 9, wherein the flow rate lowering means has a narrow refrigerant outlet for allowing outflow of the refrigerant, the outlet being provided on a lower wall of either one of the headers of the gas-liquid separator section.

13. A heat exchanger according to claim 9, wherein either one of the headers of the gas-liquid separator section has a refrigerant inlet on an upper wall thereof, either one of the header of the gas-liquid separator section has a refrigerant outlet on a lower wall thereof, and the flow rate lowering means includes a porous member provided at the refrigerant inlet and a passage extending member which is formed so as to enclose the refrigerant outlet and which elongates the length of the passage for the refrigerant from the refrigerant inlet to the refrigerant outlet.

14. A heat exchanger according to claim 13, wherein the refrigerant inlet is provided in substantially the entire portion of the upper wall of the header of the gas-liquid separator section.

15. A heat exchanger according to claim 13, wherein the refrigerant inlet is provided on a portion of the upper wall of the header of the gas-liquid separator section.

16. A heat exchanger according to claim 13, wherein the porous member is made of a mesh material.

17. A heat exchanger according to claim 13, wherein the passage extending member includes a tubular inner member projecting upward around the refrigerant outlet, and a hollow outer member projecting upward and provided on the lower wall of the header having the refrigerant outlet so as to enclose the inner member, the hollow outer member having a closed upper end and a through hole which penetrates a lower portion of a surrounding wall thereof.

18. A heat exchanger according to claim 17, wherein the upper end of the outer member is located at a position lower than the upper wall of the header having the refrigerant outlet.

19. A heat exchanger according to claim 17, wherein the upper end of the outer member is equal in height to the upper wall of the header having the refrigerant outlet.

20. A heat exchanger according to claim 13, wherein the refrigerant inlet is provided on the upper wall of either one of the headers of the gas-liquid separator section, and the refrigerant outlet is provided on the lower wall of the other header of the gas-liquid separator section.

21. A heat exchanger according to claim 13, wherein the refrigerant inlet is provided on the upper wall of either one of the headers of the gas-liquid separator section, and the refrigerant outlet is provided on the lower wall of the same header of the gas-liquid separator section.

22. A heat exchanger according to claim 21, wherein resistant imparting means is provided in the liquid receiving tubes of the gas-liquid separator section.

23. A heat exchanger according to claim 22, wherein the resistant imparting means comprises a mesh and/or a filter.

24. A heat exchanger according to claim 21, wherein the other header of the gas-liquid separator section has a pressure-reducing hole on a lower wall thereof, the hole communicating with one of the headers of the subcooling section.

25. A heat exchanger according to claim 9, wherein the headers of the condenser section, the headers of the subcooling section, and the headers of the gas-liquid separator section are configured such that a pair of tanks spaced apart from each other are partitioned by partition members to provide the respective sets of headers, and the partition members between the gas-liquid separator section and the condenser section are upper walls for the headers of the gas-liquid separator section, and the partition members between the gas-liquid separator section and the subcooling section are lower walls for the headers of the gas-liquid separator section.

26. A heat exchanger according to claim 25, wherein the width, as measured in the air passage direction, of the liquid receiving tube of the gas-liquid separator section is equal to or smaller than the width, as measured in the air passage direction, of the tank.