WO2006112540A1

WO2006112540A1 - Heat exchanger

Info

Publication number: WO2006112540A1
Application number: PCT/JP2006/308677
Authority: WO
Inventors: Koichiro Take; Shigeharu Ichiyanagi
Original assignee: Showa Denko K.K.
Priority date: 2005-04-20
Filing date: 2006-04-19
Publication date: 2006-10-26

Abstract

A heat exchanger 2 includes front and rear heat exchange sections (10) and (11). The front heat exchange section includes a pair of header tanks 12A and 12B spaced apart from each other and a plurality of heat exchange tubes 14 disposed between the header tanks 12A and 12B. The rear heat exchange section includes a pair of header tanks 13A and 13B spaced apart from each other and a plurality of heat exchange tubes 14 disposed between the header tanks 13A and 13B. Paths 37A and 37B, each composed of a plurality of heat exchange tubes 14 successively arranged, are provided in the heat exchange sections (10) and (11) at the same position so as to correspond to each other. A fluid flows in the same direction through heat exchange tubes 14 which constitute each of the paths 37A and 37B. The flow direction of the fluid in the path 37A of the heat exchange section 10 and that in the path 37B of the heat exchange section 11 are opposite each other. When this heat exchanger 2 is used for heating to-be-conditioned air in a supercritical heating cycle using CO2 as a heat carrier, it is possible to effectively prevent generation of nonuniform distribution of the blowout temperature of conditioned air.

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. 60/674,292 filed April 25, 2005 pursuant to 35 U. S. C. § lll(b) .

TECHNICAL FIELD

The present invention relates to a heat exchanger, and more particularly to a heat exchanger suitably used for heating air to be conditioned (hereinafter referred to as "to-be-conditioned air"), by means of a supercritical heating cycle in which, for example, CO₂ is used as a heat carrier.

Herein and in the appended claims, the term "aluminum" encompasses aluminum alloys in addition to pure aluminum. Further, herein and in the appended claims, the term "supercritical heating cycle" refers to a heating cycle in which the pressure of a heat carrier exceeds the critical pressure and enters a supercritical state on a high-pressure side, and the term "supercritical heat carrier" refers to a heat carrier or heat medium used in the supercritical heating cycle . BACKGROUND ART

The mainstream heating scheme in an automobile by means of an air conditioner is a scheme in which to-be-conditioned air is heated by means of a water-based heat carrier heated by waste heat of an engine. However, in automobiles for the next generation, such as hybrid cars, fuel-cell automobiles, high-efficiency gasoline engine automobiles, and diesel engine automobiles, which are designed to reduce environmental load, waste heat from the engine is small, and in some cases, a heat quantity necessary for heating the interior of the passenger compartment cannot be obtained.

In view of the above, engineers have considered using as a heat carrier a fluid which has a low critical temperature, such as CO₂. That is, CO₂ having been heated and pressurized to a high temperature and a high pressure by means of a compressor is caused to exchange heat with to-be- conditioned air at a heat exchanger within the compartment (hereinafter referred to as the "in-compartment heat exchanger) , whereby the to-be-conditioned air is heated and used for heating the interior of the compartment.

However, since CO₂ is considerably low in heat capacity as compared with a water-based heat carrier, the temperature of CO₂, which flows through heat exchange tubes as a heat carrier, sharply drops from the inlet side of the in- compartment heat exchanger toward the outlet side of the in- compartment heat exchanger, whereby the blowout temperature of conditioned air having passed through the in-compartment heat exchanger changes greatly (i.e. , the temperature distribution becomes nonuniform) with respect to the longitudinal direction of the heat exchange tubes . As a result, in the case of automobile heating by means of an air conditioner, a temperature difference arises in the conditioned air between the driver's seat side and the front- passenger's seat side, so that the air conditioning becomes unsatisfactory.

Therefore, a heat exchanger having solved the above- described problem has been proposed (see JP-A No. 2004- 125346). This heat exchanger includes first and second heat exchange sections arranged side-by-side in the air flow direction and each including first and second header tanks separated from each other, a plurality of heat exchange tubes which are disposed between the header tanks at predetermined intervals in the length direction of the header tanks and whose opposite ends are connected to the corresponding header tanks, and fins disposed between adjacent heat exchange tubes. The first header tanks and the second header tanks of the two heat exchange sections are arranged side-by-side in the air flow direction, respectively. An inlet header section is provided on the first header tank of the first heat exchanger section on the downstream side with respect to the air flow direction, and an outlet header section is provided on the first header tank of the second heat exchanger section on the upstream side with respect to the air flow direction. An intermediate header section is provided on each of the second header tanks of the two heat exchange sections such that the two intermediate headers communicate with each other. The quantity of heat transmitted from the heat carrier to the to- be-conditioned air at the first heat exchange section is set to be smaller than the quantity of heat transmitted from the heat carrier to the to-be-conditioned air at the second heat exchange section. In the heat exchanger described in the publication, in order to set the heat transmission quantities at the two heat exchange sections in the above-described manner, for example, the fin pitch of the first heat exchange section is made greater than that of the second heat exchange section, or the inclination and/or pitch of louvers of fins of the first heat exchange section is made greater than the inclination and/or pitch of louvers of fins of the second heat exchange section.

However, even in the heat exchanger described in the publication, the effect of suppressing the above-described phenomenon in which the blowout temperature of conditioned air changes; i.e., in which the temperature distribution becomes nonuniform, remains unsatisfactory. In addition, since fins which differ in fin pitch, louver inclination, and/or louver pitch are used as the fins of the heat exchange sections , the number of components increases .

An object of the present invention is to overcome the above problems and to provide a heat exchanger which can effectively prevent generation of nonuniform distribution of the blowout temperature of conditioned air.

DISCLOSURE OF THE INVENTION

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

1) A heat exchanger comprising first and second heat exchange sections arranged side-by-side in an air flow direction, each heat exchange section including first and second header tanks separated from each other and a plurality of heat exchange tubes which are disposed between the header tanks at predetermined intervals in the length direction of the header tanks and whose opposite ends are connected to the corresponding header tanks, wherein each heat exchange section is configured such that a fluid fed into the first header tank flows to the second header tank via the heat exchange tubes and flows out of the second header tank; each heat exchange section includes at least one path composed of a plurality of heat exchange tubes successively arranged; the two heat exchange sections are the same in the number of paths; the paths of the two heat exchange sections are provided on the same location to correspond to each other; the fluid flows in the same direction through the plurality of heat exchange tubes forming each path; and the flow direction of the fluid flowing through the path of the first heat exchange section is opposite the flow direction of the fluid flowing through the path of the second heat exchange section located at a position corresponding to the path of the first heat exchange section.

2) A heat exchanger according to par. 1), wherein each heat exchange section includes a single path.

3) A heat exchanger according to par. 2), wherein one header section is provided on each of the first and second header tanks of each heat exchange section; the opposite ends of all the heat exchange tubes constituting a single path are connected to the corresponding header tanks for communication with the corresponding header sections; one header section of each heat exchange section serves as an input header section, and the other header section of each heat exchange section serves as an output header section; the inlet header section of the first heat exchange section and the outlet header section of the second heat exchange section are arranged side-by-side in the air flow direction, and the outlet header section of the first heat exchange section and the inlet header section of the second heat exchange section are arranged side-by-side in the air flow direction; a fluid inlet pipe is connected to the inlet header section of each heat exchange section, and a fluid outlet pipe is connected to the outlet header section of each heat exchange section.

4) A heat exchanger according to par. 1), wherein each heat exchange section includes a plurality of paths; and the flow directions of the fluid at adjacent paths of each heat exchange section are opposite each other.

5) A heat exchanger according to par. 4 ) , wherein the same number of plural header sections are provided on each of the first and second header tanks of each heat exchange section; the opposite ends of all the heat exchange tubes constituting each path are connected to the corresponding header tanks for communication with the corresponding header sections; one header section of the first header tank communicating with all the heat exchange tubes of each path serves as an input header section communicate, and the corresponding header section of the second header tank serves as an output header section; each header tank includes the inlet header section and the outlet header section alternately arranged; the inlet header sections of the first heat exchange section and the outlet header sections of the second heat exchange section are arranged side-by-side in the air flow direction, and the outlet header sections of the first heat exchange section and the inlet header sections of the second heat exchange section are arranged side-by-side in the air flow direction; a fluid inlet pipe is connected to the inlet header sections of each heat exchange section, and a fluid outlet pipe is connected to the outlet header sections of each heat exchange section.

6 ) A heat exchanger according to par . 1 ) , wherein the header tanks of the two heat exchange sections are integrated together.

7) A heat exchanger according to par. 1 ) , wherein each heat exchange tube has a flat shape such that its width direction coincides with the air flow direction and has a plurality of fluid channels arranged therein along the width direction thereof; each of the fluid channels has a vertically elongated cross section; and when the quotient produced by dividing a channel height Hp (mm) of the fluid channel by a minimum channel width Wp (mm) of the fluid channel is defined as "aspect ratio," the aspect ratio (Hp/Wp) is 1.05 to 2.

8) A heat exchanger according to par. 7), satisfying a relation 0.5 ≤ Tw/Wp ≤ 1.5, where Tw (mm) is the thickness of a partition wall between the adjacent fluid channels of each of the heat exchange tubes, and Wp (mm) is the minimum channel width of each of the fluid channels .

9 ) A heat exchanger according to par . 7 ) , satisfying a relation 0.3 ≤ Hp/Ht ≤ 0.7, where Hp (mm) is the channel height of each of the fluid channels of each of the heat exchange tubes, and Ht (mm) is the tube height of each of the heat exchange tubes.

10) A heat exchanger according to par. 7), satisfying a relation 0.5 ≤ Sp ≤ 5, where Sp (mm²) is the total channel cross-sectional-area of all the fluid channels of each of the heat exchange tubes.

11) A heat exchanger according to par. 7), satisfying a relation Sp/Sb ≤ 0.5, where Sp (mm²) is the total channel cross-sectional-area of all the fluid channels of each of the heat exchange tubes, and Sb (mm²) is the remaining area (cross-sectional area of a bulk portion) after subtracting the total channel cross-sectional-area Sp (mm²) from the entire cross-sectional area of each of the heat exchange tubes .

12) A heat exchanger according to par. 7), satisfying a relation (Wt x Ht) /3 ≥ Sp, where Sp (mm²) is the total channel cross-sectional-area of all the fluid channels of each of the heat exchange tubes; Ht (mm) is the tube height of each of the heat exchange tubes; and Wt (mm) is the tube width of each of the heat exchange tubes .

13) A heat exchanger according to par. 7), satisfying a relation Ht ≤ 4, where Ht (mm) is the tube height of each of the heat exchange tubes .

14) A heat exchanger according to par. 7), wherein each of the heat exchange tubes includes two flat walls in parallel with each other; first and second side walls extending over corresponding side ends of the two flat walls; and reinforcement walls provided between the first and second side walls and extending between the two flat walls and in the longitudinal direction of the two flat walls; and each of the heat exchange tubes is formed from a single metal sheet including two flat-wall-forming portions; a connection portion connecting the two flat-wall-forming portions and adapted to form the first side wall; two side- wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the flat-wall-forming portions opposite the connection portion, and adapted to form the second side wall; and a plurality of reinforcement-wall-forming elongated projections provided integrally with the flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections; and the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side- wall-forming elongated projections butt against each other and such that the reinforcement-wall-forming elongated projections butt against each other, and by brazing the mutually butting side-wall-forming elongated projections together and the mutually butting reinforcement-wall-forming elongated projections together, the mutually brazed reinforcement-wall-forming elongated projections forming the reinforcement walls.

15) A heat exchanger according to par. 14), wherein of two reinforcement-wall-forming elongated projections which form each reinforcement wall, one reinforcement-wall-forming elongated projection has a groove which is formed on the tip end face thereof so as to receive a tip end portion of the other reinforcement-wall-forming elongated projection.

16) A heat exchanger according to par. 7), wherein each of the heat exchange tubes includes two flat walls in parallel with each other; first and second side walls extending over corresponding side ends of the two flat walls; and reinforcement walls provided between the first and second side walls and extending between the two flat walls and in the longitudinal direction of the two flat walls; and each of the heat exchange tubes is formed from a single metal sheet including first and second flat-wall-forming portions; a connection portion connecting the first and second flat-wall-forming portions and adapted to form the first side wall; two side-wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the first and second flat- wall-forming portions opposite the connection portion, and adapted to form the second side wall; and a plurality of reinforcement-wall-forming elongated projections provided integrally with the first and second flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections; and the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side- wall-forming elongated projections butt against each other, and by brazing the mutually butting side-wall-forming elongated projections together, brazing the reinforcement- wall-forming elongated projections of the first flat-wall- forming portion to the second flat-wall-forming portion, and brazing the reinforcement-wall-forming elongated projections of the second flat-wall-forming portion to the first flat- wall-forming portion, the reinforcement-wall-forming elongated projections brazed to the first and second flat- wall-forming portions forming the reinforcement walls.

17) A heat exchanger according to par. 16), wherein projections are integrally formed, in such a manner as to extend along the entire length of the first and second flat- wall-forming portions, at those portions of the first and second flat-wall-forming portions which the corresponding reinforcement-wall-forming elongated projections of the second and first flat-wall-forming portions abut; grooves are formed on the corresponding tip end faces of the projections so as to receive corresponding tip end portions of the reinforcement-wall-forming elongated projections; and while being fitted into the corresponding grooves, the tip end portions of the reinforcement-wall-forming elongated projections are brazed to the corresponding projections.

18) A heat exchanger according to par. 7), wherein corrugate fins each including wave crest portions, wave trough portions, and connection portions each connecting together a wave crest portion and a wave trough portion are each arranged between the adjacent heat exchange tubes; the fin height of the individual corrugate fins ; i.e., the direct distance between the wave crest portions and the wave trough portions, is 3 mm to 8 mm; a fin pitch; i.e., the pitch of the connection portions, is 0.5 mm to 1.5 mm; and the thickness of each of the corrugate fins is 0.05 mm to 0.1 mm.

19) A heat exchanger according to par. 18), wherein the corrugate fins are disposed to across the two heat exchange sections, and shared by the heat exchange tubes of the heat exchange sections .

20) A heat exchanger according to par. 19), wherein a heat transmission reducing portion is formed on each corrugate fin between the two heat exchange sections .

21) A heat exchanger according to par. 20), wherein the heat transmission reducing portion is formed of a slit.

22) A supercritical heating cycle which comprises a compressor, an in-compartment heat exchanger to which a high temperature, high pressure heat carrier having been compressed by the compressor is fed, a pressure-reducing device for depressurizing the heat carrier flowing out of the in-compartment heat exchanger, and an out-compartment heat exchanger for cooling the depressurized heat carrier and in which a supercritical heat carrier is used, wherein the in- compartment heat exchanger is a heat exchanger according to any one of pars. 1) to 21).

According to the heat exchanger described in par. 1) to 5), each heat exchange section includes at least one path composed of a plurality of heat exchange tubes successively arranged; the two heat exchange sections are the same in the number of paths; the paths of the two heat exchange sections are provided on the same location to correspond to each other; the fluid flows in the same direction through the plurality of heat exchange tubes forming each path; and the flow direction of the fluid flowing through the path of the first heat exchange section is opposite the flow direction of the fluid flowing through the path of the second heat exchange section located at a position corresponding to the path of the first heat exchange section. Therefore, the temperature distribution of air having passed through the first heat exchange section with respect to the longitudinal direction of the heat exchange tubes becomes reverse to that of air having passed through the second heat exchange section, so that these temperature distributions are canceled out. Accordingly, it becomes possible to effectively prevent generation of nonuniform distribution of the blowout temperature of air having passed through the heat exchanger. In addition, unlike the heat exchanger described in Patent Document 1, the two heat exchange sections are not required to have different fins, whereby the number of components decreases .

The heat exchanger described in par. 6) can reduce the number of components.

The heat exchanger described in any one of pars. 7) to 13) exhibits improved heat exchange performance, and enhanced withstand pressure of the flat heat exchange tubes.

The heat exchanger described in par. 18) exhibits improved heat radiation performance while suppressing an increase in pressure loss of air flowing through clearances between adjacent flat heat exchange tubes, thereby maintaining good balance therebetween.

The heat exchanger described in par. 19) can reduce the number of components.

According to the heat exchanger described in par. 20), it becomes possible to improve the effect of suppressing generation of nonuniform distribution of the blowout temperature of air having passed through the heat exchanger, because of the reduced quantity of heat transferred between the two heat exchange sections. According to the heat exchanger described in par. 21), the heat transmission reducing section can be formed on the corrugate fins in a relatively easy manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a heating cycle using an in-compartment heat exchanger to which the present invention is applied. FIG. 2 is a partially cut-away perspective view showing the overall configuration of Embodiment 1 of the in- compartment heat exchanger to which the present invention is applied. FIG. 3 is a partially omitted vertical sectional view of the in-compartment heat exchanger of FIG. 2 as viewed from the rear side thereof. FIG. 4 is an enlarged fragmentary view in section taken along line A—A of FIG. 2. FIG. 5 is an exploded perspective view showing a first tank of the in-compartment heat exchanger of FIG. 2. FIG. 6 is an exploded perspective view showing a second tank of the in- compartment heat exchanger of FIG. 2. FIG. 7 is an enlarged cross-sectional view showing a heat exchange tube of the in- compartment heat exchanger of FIG. 2. FIG. 8 is a fragmentary enlarged view of FIG. 7. FIG. 9 is a diagram showing the flow of a heat carrier in the in-compartment heat exchanger of FIG. 2. FIG. 10 is a pair of diagrams showing the flow of a heat carrier in each of in-compartment heat exchangers of Comparative Experiment Examples 1 and 2. FIG. 11 is a graph showing the results of Experiment Example and Comparative Experiment Examples 1 and 2. FIG. 12 is a partially cut-away perspective view showing the overall configuration of Embodiment 2 of the in-compartment heat exchanger to which the present invention is applied. FIG. 13 is an exploded perspective view showing a first tank of the in-compartment heat exchanger of FIG. 12. FIG. 14 is an exploded perspective view showing a second tank of the in- compartment heat exchanger of FIG. 12. FIG. 15 is a diagram showing the flow of a heat carrier in the in-compartment heat exchanger of FIG. 12. FIG. 16 is an enlarged cross-sectional view showing a first modified embodiment of the heat exchange tube. FIG. 17 is a fragmentary enlarged view of FIG. 16. FIG. 18 is a series of views showing a method of manufacturing the heat exchange tube shown in FIG. 16. FIG. 19 is an enlarged cross-sectional view showing a second modified embodiment of the heat exchange tube. FIG. 20 is an enlarged cross-sectional view showing a third modified embodiment of the heat exchange tube. FIG. 21 is a fragmentary enlarged view of FIG. 20. FIG. 22 is a series of views showing a method of manufacturing the heat exchange tube shown in FIG. 20. FIG. 23 is an enlarged cross- sectional view showing a fourth modified embodiment of the heat exchange tube. FIG. 24 is a fragmentary enlarged view of FIG. 23. FIG. 25 is a set of views showing a method of manufacturing the heat exchange tube shown in FIG. 23.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will next be described with reference to the drawings . In this embodiment, the present invention is applied to an in- compartment heat exchanger of a heating cycle using a supercritical heat carrier, such as CO₂.

In the following description, the downstream side of an air flow through air-passing clearances between adjacent heat exchange tubes (the direction indicated by arrow X in FIGS. 2 and 12) will be referred to as the "front," and the opposite side as the "rear." The upper, lower, left-hand, and right- hand in FIGS. 2, 3, and 12 will be referred to as "upper" (or a similar expression) , "lower" (or a similar expression) , "left" (or a similar expression), and "right" (or a similar expression), respectively. Further, the same reference numerals are used throughout the drawings to refer to similar parts or elements , and their repeated descriptions will be omitted. Embodiment 1

This embodiment is shown in FIGS. 1 to 9.

FIG. 1 shows a heating cycle using CO₂ in which an in- compartment heat exchanger of this embodiment is used, FIGS. 2 and 3 show the overall configuration of the in-compartment heat exchanger of this embodiment, and FIGS. 4 to 8 show the configuration of essential portions of the in-compartment heat exchanger. Further, FIG. 9 shows a flow of a heat carrier in the in-compartment heat exchanger.

As shown in FIG. 1, the heating cycle includes a compressor (1)', an in-compartment heat exchanger (2) to which a high-temperature, high-pressure heat carrier having been compressed by the compressor (1) is fed, an expansion valve (3) (pressure-reducing device) which depressurizes the heat carrier flowing out of the in-compartment heat exchanger (2), an out-compartment heat exchanger (4) which evaporates the depressurized heat carrier, and an accumulator (5) (gas- liquid separator) which performs gas-liquid separation of the heat carrier flowing out of the out-compartment heat exchanger (4). The heating cycle is installed to an automobile. Incidentally, in the case of a car air conditioner which performs heating and cooling the interior of the passenger compartment of an automobile, if necessary, the heating cycle may include an evaporator, an expansion valve (a pressure-reducing device) which depressurizes the heat carrier before flowing into the evaporator, an intermediate heat exchanger which performs heat exchange between the heat carrier flowing out of the out-compartment heat exchanger (4) and the heat carrier flowing out of the evaporator, a bypass passage with a bypass valve which feeds the heat carrier flowing out of the in-compartment heat exchanger (2) into the out-compartment heat exchanger (4) without passing through the expansion valve (3), and a bypass passage with a bypass valve which feeds the heat carrier flowing out of the intermediate heat exchanger into the accumulator (5) without passing through the evaporator.

As shown in FIGS. 2 to 4, the in-compartment heat exchanger (2) comprises a front heat exchange section (10) and a rear heat exchange section (11) which are arranged in parallel in the front-rear direction. Each of the heat exchange sections (10) and (11) comprises a pair of header tanks (12A) and (12B), and (13A) and (13B) spaced apart from each other in the left-right direction and extending in the vertical direction; a plurality of flat heat exchange tubes (14) arranged in parallel between the two header tanks (12A) and (12B), and (13A) and (13B), respectively, and disposed at predetermined intervals in the vertical direction; corrugated fins (15) disposed within air-passing clearances between the adjacent heat exchange tubes (14) and on the outer sides of the uppermost and lowermost heat exchange tubes (14), and each brazed to the corresponding heat exchange tubes (14); and side plates (16) made of bare aluminum material, disposed on the outer sides of the uppermost and lowermost corrugate fins (15), and brazed to the corresponding corrugate fins (15).

The left header tanks (12A) and (13A) of the front and rear heat exchange sections (10) and (11); and the right header tanks (12B) and (13B) of the front and rear heat exchanger sections (10) and (11) are formed integrally, respectively. In this embodiment, the integrated left header tanks (12A) and (13A) will be referred to as a "first header tank (17)," and the integrated right header tanks (12B) and (13B) will be referred to as a "second header tank (18)."

As shown in FIG. 4 and 5, the first header tank (17) comprises a header-forming plate (21) formed from a" brazing sheet (an aluminum brazing sheet in the present embodiment) having a brazing material layer over each of opposite surfaces thereof, a tube-connecting plate (22) formed from a brazing sheet (an aluminum brazing sheet in the present embodiment) having a brazing material layer over each of opposite surfaces thereof, and an intermediate plate (23) made from a bare metal material (a bare aluminum material in the present embodiment) and interposed between the header- forming plate (21) and the tube-connecting plate (22), wherein the plates (21) to (23) are arranged in superposed layers and brazed to one another.

Formed in the header-forming plate (21) and mutually separated in the front-rear direction are two bulging portions (24A) and (24B) extending vertically and being equal in bulging height, length, and width. An opening of each of the bulging portions (24A) and (24B) facing rightward is closed with the intermediate plate (23). A heat carrier inlet (25) is formed in an upper portion in the top of the front bulging portion (24A) of the header-forming plate (21), and a heat carrier outlet (26) is formed in a lower portion in the top of the rear bulging portion (24B) of the plate (21). The header-forming plate (21) is formed by press work on an aluminum brazing sheet having a brazing material layer over each of opposite surfaces thereof.

Each of the front and rear portions of the tube- connecting plate (22) has a plurality of tube insertion holes (27) extending through the thickness thereof, elongated in the front-rear direction, and separated from one another in the vertical direction. The insertion holes (27) in the front portion of the plate (22) are provided within the vertical range of the front bulging portion (24A) of the header-forming plate (21), and the insertion holes (27) in the rear portion of the plate (22) are provided within the vertical range of the rear bulging portion (24B) of the header-forming plate (21). The front-to-rear length of each tube insertion hole (27) is slightly larger than the front- to-rear width of each of the bulging portions (24A) and (24B), and the front and rear ends of the tube insertion hole (27) project outward beyond the respective front and rear edges of the bulging portion (24A) and (24B) (see FIG. 4). Cover walls (28) projecting leftward to the outer surface of the header-forming plate (21) and covering the boundary between the header-forming plate (21) and the intermediate plate (23) over the entire length thereof are formed integrally with the front and rear side edge portions of the tube-connecting plate (22), and brazed to the front and rear side faces of the header-forming plate (21) and the intermediate plate (23). A plurality of engaging portions (29) engaging with the outer surface of the header-forming plate (21) are formed integrally with the projecting ends of the cover walls (28) at predetermined intervals in the vertical direction, and brazed to the header forming plate (21). The tube-connecting plate (22) is made by press work on an aluminum brazing sheet having a brazing material layer over each of opposite surfaces thereof.

The intermediate plate (23) has communication holes (31) extending through the thickness thereof and equal in number to the tube insertion holes (27) of the tube- connecting plate (22) for allowing the holes (27) to communicate with the bulging portion (24A) or (24B) of the header-forming plate (21) therethrough. The communication holes (31) are substantially larger than the tube insertion holes (27) (see FIG. 4). The communication holes (31) are formed at positions corresponding to the respective tube insertion holes (27) of the tube-connecting plate (22). The front tube insertion holes (27) of the tube-connecting plate (22) communicate with the interior of the front bulging portion (24A) through the front communication holes (31) of the intermediate plate (23), the rear tube insertion holes (27) of the tube-connecting plate (22) communicate with the interior of the rear bulging portion (24B) through the rear communication holes (31) of the intermediate plate (23). All the communication holes (31) communicating with the interior of the front bulging portion (24A), as well as. all the communication holes (31) communicating with the interior of the rear bulging portion (24B), are held in communication by communication portions (32) formed by cutting away the portions between the adjacent communication holes (31) in the intermediate plate (23). The intermediate plate (23) is made by press work on a bare aluminum material.

The second tank (18) has the similar construction as the first tank (17) and members and portions similar to those of the first tank (17) are denoted by the same reference numerals (see FIG. 6). The tanks (17) and (18) are arranged with their tube-connecting plates (22) opposed to each other. The second tank (18) differs from the first tank (17) in that a heat carrier outlet (26) is formed in a lower portion of the top of the front bulging portion (24A) of the header- forming plate (21), and a heat carrier inlet (25) is formed in an upper portion of the top of the rear bulging portion (24B) of the plate (21).

Each of the tanks (17) and (18) is manufactured as follows. The header-forming plate (21) having the bulging portions (24A) and (24B); the tube-connecting plate (22) having the tube insertion holes (27), the cover wall (28), and engaging portion forming lugs (29A) (see solid lines in FIGS. 5 and 6) extending straight from each of the cover walls (28); and the intermediate plate (23) having the communication holes (31) and the communication portions (32) are formed. Subsequently, the three plates (21), (22), and (23) of each header tank are assembled in a layered form, and then the lugs (29A) are bent and engaged with the header- forming plate (21) to form engaging portions (29). Next, the three plates (21), (22), and (23) are brazed to one another by utilization of the brazing material layers of the header- forming plate (21) and the brazing material layers of the tube-connecting plate (22). Further, the cover walls (28) are brazed to the front and rear side faces of the ^• intermediate plate (23) and. the front and rear side faces of the header-forming plate (21), and the engaging portions (29) are brazed to the header-forming plate (21).

As shown in FIG. 7 and 8, each of the heat exchange tubes (14) is made from a metal extrudate (aluminum extrudate in the present embodiment ) , is in the form of a flat tube whose width direction corresponds to the front-rear direction. In the interior of the tube (14), a plurality of heat-carrier channels (14a) extending in the longitudinal direction of the heat exchange tube (14) are formed and arranged in parallel. Each of the heat-carrier channels (14a) has the same vertically elongated rectangular transverse cross section, except for those at the opposite end portions . The opposite ends of each heat exchange tube (14) are brazed to the tube- connecting plates (22) of the tanks (17) and (18) using the brazing material layers of the tube-connecting plates (22), with the opposite ends being inserted into the respective tube insertion holes (27) of the tanks (17) and (18). Each end of the heat exchange tube (14) is placed into the corresponding communication hole (31) of the intermediate plate (23) to an intermediate portion of the thickness thereof (see FIG. 4). The opposite end portions of the front heat exchange tubes (14) are connected to the corresponding tanks (17) and (18) so as to communicate with the interior of the front bulging portion (24A). Similarly, the opposite end portions of the rear heat exchange tubes (14) are connected to the corresponding tanks (17) and (18) so as to communicate with the interior of the rear bulging portion (24B).

The heat exchange tubes (14) preferably satisfy the following relationships 1 to 7. In the relationships , the height of the heat-carrier channel (14a) of each heat exchange tube (14) is represented by Hp (nun), the minimum passage width of the heat-carrier channels (14a) (except for those at the opposite end portions) is represented by Wp (mm), the thickness of a partition wall (14b) between adjacent heat-carrier channels (14a) in each heat exchange tube (14) is represented by Tw (mm) , the height of each heat exchange tube (14) is represented by Ht (mm), the total cross- sectional area of all the heat-carrier channels (14a) of each heat exchange tube (14) (the total area of hatched portions in FIG. 7(b)) is represented by Sp (mm²), the area (the area of the hatched bulk portion in FIG. 7(a)) obtained by subtracting the total cross-sectional area Sp (mm²) from the entire cross-sectional area T (mm²) of each heat exchange tube (14) is represented by Sb (mm²) (= T - Sp), and the width of each heat exchange tube (14) is represented by Wt (mm) . Relationship 1

When the quotient produced by dividing Hp (mm) by Wp (mm) is defined as "aspect ratio," 1.05 ≤ aspect ratio (Hp/Wp) ≤ 2 Relationship 2

0.5 ≤ Tw / Wp ≤ 1.5 Relationship 3 0.3 ≤ Hp / Ht ≤ 0.7 Relationship 4

0.5 ≤ Sp ≤ 5 Relationship 5

Sp/Sb ≤ 0.5 Relationship 6

(Wt x Ht) / 3 ≥ Sp Relationship 7

Ht ≤ 4

When the above relationships 1 to 7 are satisfied, the heat radiation performance of the heat exchanger (1) is improved, and the withstand pressure of the heat exchange tube (14) is increased. In the heat exchange tube (14) used in the heat exchange ( 1) of the present embodiment , the width of the heat-carrier channels (14a), except for those at the opposite end portions, remains unchanged along the entire height of the heat-carrier channels ( 14a) . Thus, the width of each of the heat-carrier channels (14a) is the minimum channel width Wp. The width of the heat-carrier channels (14a) at the opposite end portions changes in the height direction, and needless to say, the minimum channel width Wp is the width of the narrowest potion. Further, the above relationship 4 is preferable to be 0.5 ≤ Sp ≤ 3.

Each of the corrugated fins (15) is formed in a wavy form using an aluminum brazing sheet having a brazing material layer over each of opposite surfaces thereof. The corrugate fin (15) includes wave crest portions, wave trough portions, and connection portions each connecting together the wave crest portion and the wave trough portion. A plurality of louvers (15a) are formed at the connection portions in such a manner as to be juxtaposed in the front- rear direction. The heat exchange tubes (14) of the front and rear heat exchange sections (10) and (11) share the corrugate fins (15). The width of the corrugate fin (15) as measured in the front-rear direction is approximately equal to the span between the front edges of the heat exchange tubes (14) of the front heat exchange section and the rear edges of the rear heat exchange tubes (14) of the rear heat exchange section. The fin height of each corrugate fin (15) is the direct distance between the wave crest portion and the wave trough portion, and the fin height is preferably 3 mm to 8 mm. Further, the fin pitch of each corrugate fin (15) is the distance between the central portions (with respect to the left-right direction) of a wave crest portion and a wave trough portion adjacent thereto; i.e., half the interval between the central portions (with respect to the left-right direction) of the adjacent wave crest portions or the adjacent wave trough portions, and the fin pitch is preferably 0.5 mm to 1.5 mm. Moreover, the thickness of each corrugate fin (15) is 0.05 mm to 0.1 mm. Moreover, the corrugate fins (15) have slits (15b) (heat transmission reducing portions) formed between the front heat exchange section (10) and the rear heat exchange section (11) at predetermined intervals such that the slits (15b) span the wave crest portions, the wave trough portions, and the connection portions .

In the in-compartment heat exchanger (2), the front half section of the first tank (17) including front bulging portion (24A) serves as a heat carrier inlet header section (33A) of the front heat exchange section (10), and the front half section of the second tank (18) including front bulging portion (24A) serves as a heat carrier outlet header section (33B) of the front heat exchange section (10). In other words, the heat carrier inlet header section (33A) is formed in the left header tank (12A) of the front heat exchange section (10), and the heat carrier outlet header section (33B) is formed in the right header tank (12B) of the front heat exchange section (10). Further, the rear half section of the second tank (18) including rear bulging portion (24B) serves as a heat carrier inlet header section (34A) of the rear heat exchange section (11), and the rear half section of the first tank (17) including rear bulging portion (24B) serves as a heat carrier outlet header section (34B) of the rear heat exchange section (11). In other words, the heat carrier inlet header section (34A) is formed in the right header tank (13B) of the rear heat exchange section (11), and the heat carrier outlet header section (34B) is formed in the left header tank (13A) of the rear heat exchange section (11). Therefore, the front heat exchange section (10) has a path (37A) formed by all the heat exchange tubes (14) communicating with the heat carrier inlet header section (33A) and the heat carrier outlet header section (33B); and the rear heat exchange section (11) has a path (37B) formed by all the heat exchange tubes (14) communicating with the heat carrier inlet header section (34A) and the heat carrier outlet header section (34B). The flow direction of the heat carrier in the path (37A) of the front heat exchange section

(10) and that in the path (37B) of the rear heat exchange section (11) are opposite each other. Moreover, heat carrier inlet pipes (35) branching from a piping extending from the compressor (1) are connected to the heat carrier inlet header sections (33A) and (34A) of the front and rear heat exchange sections (10) and (11) such that the piles (35) are inserted into the heat carrier inlets (25). Heat carrier outlet pipes (36) merging into a piping extending to the expansion valve (3) are connected to the heat carrier outlet header sections (33B) and (34B) such that the pipes (36) are inserted into the heat carrier outlets .

In the above mentioned heating cycle, as shown in FIG. 9, high-temperature, high-pressure CO₂ having been compressed by the compressor (1) flows into the interior of the heat carrier inlet header section (33A) of the left header tank (12A) of the front heat exchange section (10) and the interior of the heat carrier inlet header section (34A) of the right header tank (13B) of the rear heat exchange section

(11) trough the heat carrier inlet pipes (35). The CO₂ which has entered the interior of the heat carrier inlet header section (33A) of the front heat exchange section (10) flows rightward through the front heat exchange tubes (14) constituting the path (37A) and enters the interior of the heat carrier outlet header section (33B) of the right header tank (12B). The CO₂ which has entered the interior of the heat carrier inlet header section (34A) of the rear heat exchange section (11) flows leftward through the rear heat exchange tubes (14) constituting the path (37B) and enters the interior of the heat carrier outlet header section (34B) of the left header tank (13A). The CO₂ which has entered the heat carrier outlet header sections (33B) and (34B) flows out to the heat carrier outlet pipes (36) and is fed to the expansion valve (3). While flowing through the heat exchange tubes (14), the CO₂ is subjected to heat exchange with the to-be-conditioned air flowing through the adjacent air- passing clearances in the direction of arrow X shown in FIGS. 2 and 9, and the to-be-conditioned air is thereby heated.

Since the heat capacity of CO₂ is small, the temperature of the CO₂ which flows through the heat exchange tubes (14) decreases rapidly from the heat carrier inlet header sections (33A) and (34A) toward the heat carrier outlet header sections (33B) and (34B). Consequently, the blowing-out temperature of the conditioned air which has passed through the heat exchange section (10) and (11) decreases from the heat carrier inlet header sections (33A) and (34A) toward the heat carrier outlet header sections (33B) and (34B), whereby the temperature distribution becomes non-uniform. However, in the front heat exchange section (10), the temperature of the CO₂ and the blowing-out temperature of the conditioned air decrease from the left side toward the right side; and in the rear heat exchange section (11), the temperature of the CO₂ and the blowing-out temperature of the conditioned air decrease from the right side to the left side. Therefore, the nonuniform distribution of the temperature of the conditioned air having passed through the heat exchange section (10) and the nonuniform distribution of the temperature of the conditioned air having passed through the heat exchange section (11) are canceled out each other. As a result, the temperature distribution of the conditioned air having passed through the in-compartment heat exchanger (2) becomes uniform.

An experiment example performed by using the in- compartment heat exchanger (2) of embodiment 1 will next be described along with comparative experiment examples. Experiment Example

A heat exchanger having the following dimensions was prepared. The height Hc (the dimension as measured in the longitudinal direction of the header tanks ) of the heat exchange core sections of the front and rear heat exchange sections (10) and (11), each section comprising the heat exchange tubes (14) and the corrugate fins (15), is 200 mm; the width Wc (the dimension as measured in the longitudinal direction of the heat exchange tube) of the heat exchange core sections is 250 mm; the number of the heat exchange tubes (14) in each of the heat exchange sections (10) and (11) is 36. The channel height Hp of each heat-carrier channel (14a) of the heat exchange tube (14) is 0.44 mm; the minimum channel width Wp of the heat-carrier channel (14a), except for those at the opposite end portions, is 0.32 mm; the thickness Tw of a partition wall (14b) between adjacent heat-carrier channels (14a) is 0.38 mm; the tube height Ht is 1.3 mm; the total cross-sectional area Sp of all the heat- carrier channel (14a) is 2.4 mm²; the area Sb obtained by subtracting the total cross-sectional area Sp (mm²) from the entire cross-sectional area of each heat exchange tube (14) is 12.9 mm²; and tube width Wt is 12mm. Accordingly, the above-described relationships 1 to 7 are satisfied; i.e., the aspect ratio (Hp/Wp) = 1.4, Tw/Wp = 1.2, Hp/Ht = 0.3, Sp/Sb = 0.2, and (Wt x Ht) /3 = 5.2.

Next, with employing a bench testing apparatus for a car air conditioner, the temperature of air which has passed through the in-compartment heat exchanger (2) was measured at a plurality of points which differ in distance each other as measured from the left end of the heat exchange core section (i.e., heat exchange tubes (14)) of the in-compartment heat exchanger ( 2 ) under the following conditions : the front wind velocity (the inlet side wind velocity): 1.6 m/s, the air temperature: O⁰C, the circulation volume of a CO₂ heat carrier: 100 kg/h, the heat carrier pressure at the inlet: 11 MPa, and the heat carrier temperature at the inlet: 10O⁰C. Subsequently, the air temperatures at all measurement points were averaged to obtain the average temperature of the conditioned air; and the relation between the distance from the left end of the heat exchange core section to each measurement point and the temperature difference of the blowing-out temperature at each measurement point in relation to the average temperature was obtained. Comparative Experiment Example 1

An in-compartment heat exchanger (100) comprising a single heat exchange section (103) was prepared. The heat exchange section (103) includes a pair of header tanks (101) spaced apart from each other and a plurality of heat exchange tubes (102) disposed between the two header tanks (101) at intervals along the longitudinal direction of the header tanks (101) and each having opposite end portions connected to their corresponding header tanks (101). In this in- compartment heat exchanger (100), a heat carrier inlet header section is formed in the left header tank (101) and a heat carrier outlet header section is formed in the right header tank (101) for allowing a heat carrier to flow from the heat carrier inlet header section to the heat carrier outlet header section through the heat exchange tubes (102) (see FIG. 10 (a)). The dimensions of the heat exchange section (103) and the dimensions of the heat exchange tubes (102) of this in-compartment heat exchanger (100) are identical with those in the experiment example.

Under conditions similar to those in the experiment example, the temperature of air which has passed trough the in-compartment heat exchanger (100) was measured at a plurality of points which differ in distance as measured from the left end of the heat exchange tube (102) of the heat exchanger (100). Subsequently, the air blowing-out temperatures at all measurement points were averaged to obtain the average blowing-out temperature of the conditioned air; and the relation between the distance from the left end of the heat exchange tube (102) to each measurement point and the temperature difference of the blowing-out temperature at each measurement point in relation to the average temperature was obtained. Comparative Experiment Example 2

An in-compartment heat exchanger (200) comprising heat exchange sections (203) and (204) which are arranged in parallel in the air passage direction was prepared. Each of the heat exchange sections (203) and (204) includes a pair of header tanks (201) spaced apart from each other and a plurality of the heat exchange tubes (202) disposed between the two header tanks (201) at intervals along the longitudinal direction of the header tanks (201) and each having opposite end portions connected to there corresponding header tanks (201). In this in-compartment heat exchanger (200), a heat carrier inlet header section is formed in the left header tank (201) of the front heat exchange section (203) and a heat carrier outlet header section is formed in the left header tank (201) of the rear heat exchange section (204) . Moreover, intermediate header sections are formed in the right header tank (201) of the front heat exchange section (203) and in the right header tank (201) of the rear heat exchange section (204) such that the intermediate header sections communicate with each other. Further, a heat carrier flows from the heat carrier inlet header section of the front heat exchange section (203) to the intermediate header section of the front heat exchange section (203) through the heat exchange tubes (202), enters the intermediate header section of the rear heat exchange section (204) and flows to the heat carrier outlet header section through the heat exchange tubes (202) (see FIG. 10(b)). The dimensions of each of the heat exchange sections (203) and (204) of this in-compartment heat exchanger (200), and the dimensions of each of the heat exchange tubes of this in- compartment heat exchanger (200) are identical with those in the experiment example.

Under conditions similar to those in the experiment example, the temperature of air which has passed trough the in-compartment heat exchanger (200) was measured at a plurality of points which differ in distance as measured from the left end of the heat exchange tube (202) of the heat exchanger (200). Subsequently, the air blowing-out temperatures at all measurement points were averaged to obtain the average blowing-out temperature of the conditioned air; and the relation between the distance from the left end of the heat exchange tube (202) to each measurement point and the temperature difference of the blowing-out temperature at each measurement point in relation to the average temperature was obtained.

The results of these experiments are shown in FIG. 11. FIG. 11 clearly shows that unevenness in the temperature distribution of the blowing-out conditioned air is small when the in-compartment heat exchanger (2) of Embodiment 1 is employed. Embodiment 2

This embodiment is shown in FIGS. 12 to 15.

FIG. 12 shows the overall configuration of an in- compartment heat exchanger of this embodiment, and FIGS. 13 and 14 show the configuration of essential portions of the in-compartment heat exchanger. Further, FIG. 15 shows a flow of a heat carrier within the in-compartment heat exchanger.

In the case of the in-compartment heat exchanger (40) of this embodiment, a first tank (17) has two bulging portions (41A) and (41F) extending vertically and mutually separated in the front-rear direction in the upper portion of a header-forming plate (21), and two bulging portions (41D) and (41G) extending vertically and mutually separated in the front-rear direction in the lower portion of the header- forming plate (21); a second tank (18) has two bulging portions (41B) and (41E) extending vertically and mutually separated in the front-rear direction in the upper portion of the header-forming plate (21), and two bulging portions (41C) and (41H) extending vertically and mutually separated in the front-rear direction in the lower portion of the plate (21). Hereinafter, in this embodiment, the bulging portion (41A) in the upper front portion of the first tank (17) will be referred to as a "first bulging portion," the bulging portion (41B) in the upper front portion of the second tank (18) will be referred to as a "second bulging portion," the bulging portion (41C) in the lower front portion of the second tank (18) will be referred to as a "third bulging portion," the bulging portion (41D) in the lower front portion of the first tank (17) will be referred to as a "fourth bulging portion," the bulging portion (41E) in the upper rear portion of the second tank (18) will be referred to as a "fifth bulging portion," the bulging portion (41F) in the upper rear portion of the first tank (17) will be referred to as a "sixth bulging portion," the bulging portion (41G) in the lower rear portion of the first tank (17) will be referred to as a "seventh bulging portion," and the bulging portion (41H) in the lower rear portion of the second tank (18) will be referred to as an "eighth bulging portion." An opening of each of the bulging portions (41A) to (41H) facing inward in the left-right direction is closed with an intermediate plate (23). Each of the bulging portions (41A) to (41H) are equal in bulging height, length, and width. A heat carrier inlet (25) is formed in the top of each of the first bulging portion (41A), the third bulging portion (41C), the fifth bulging portion (41E), and the seventh bulging portion (41G). A heat carrier outlet (26) is formed in the top of each of the second bulging portion (41B), the fourth bulging portion (41D), the sixth bulging portion (41F), and the eighth bulging portion (41H).

Insertion holes (27) in the front upper-half portion of a tube-connecting plate (22) of each of the tanks (17) and (18) are provided within the vertical range of the first and second bulging portions (41A) and (41B) of the header-forming plate (21); and the insertion holes (27) in the front lower- half portion of the plate (22) are provided within the vertical range of the third and fourth bulging portions (41C) and (41D) of the plate (21). The insertion holes (27) in the rear upper-half portion of the tube-connecting plate (22) of each of the tanks (17) and (18) are provided within the vertical range of the fifth and sixth bulging portions (41E) and (41F) of the header-forming plate (21); and the insertion holes (27) in the rear lower-half portion of the plate (22) are provided within the vertical range of the seventh and eighth bulging portions (41G) and (41H) of the plate (21).

A plurality of the tube insertion holes (27) in the front upper-half portion of the tube-connecting plates (22) of the tanks (17) and (18) communicate with the interiors of the first and second bulging portions (41A) and (41B), respectively, through a plurality of communication holes (31) in the front upper-half portions of the intermediate plates (23). A plurality of tube insertion holes (27) in the front lower-half portions of the tube-connecting plates (22) of the tanks (17) and (18) communicate with the interiors of the third and fourth bulging portions (41C) and (41D), respectively, through a plurality of communication holes (31) in the front lower-half portions of the intermediate plates (23). A plurality of tube insertion holes (27) in the rear upper-half portions of the tube-connecting plates (22) of the tanks (17) and (18) communicate with the interiors of the fifth and sixth bulging portions (41E) and (41F), respectively, through a plurality of communication holes (31) in the rear upper-half portions of the intermediate plates (23). A plurality of tube insertion holes (27) in the rear lower-half portions of the tube-connecting plates (22) of the tanks (17) and (18) communicate with the interiors of the seventh and eighth bulging portions (41G) and (41H), respectively, through a plurality of communication holes (31) in the rear lower-half portions of the intermediate plates (23).

In the intermediate plates (23) of the tanks (17) and (18), all the communication holes (31) communicating with the interiors of the first and second bulging portions (41A) and (41B), all the communication holes (31) communicating with the interiors of the third and fourth bulging portions (41C) and (41D), all the communication holes (31) communicating with the interiors of the fifth and sixth bulging portions (41E) and (41F), and all the communication holes (31) communicating with the interiors of the seventh and eighth bulging portions (41G) and (41H), are held in communication by communication portions (32), which are formed by cutting away the portions between vertically adjacent pairs of the communication holes (31) of the intermediate plate (23). In this in-compartment heat exchanger (40), the front portions of the tanks (17) and (18) including the first and third bulging portions (41A) and (41C) serve as heat carrier inlet header sections (42A) of a front heat exchange section (10), and the front portions of the tanks (17) and (18) including the second and fourth bulging portions (41B) and (41D) serve as heat carrier outlet header sections (42B) of the front heat exchange section (10). In other words, the heat carrier inlet header section (42A) and the heat carrier outlet header section (42B) are formed in a left header tank (12A) of the front heat exchange section (10) such that they are separated from each other in the vertical direction, and the heat carrier outlet header section (42B) and the heat carrier inlet header (42A) are formed in a right header tank (12B) of the front heat exchange section (10) such that they are separated from each other in the vertical direction. Moreover, the rear portions of the tanks (17) and (18) including the fifth and seventh bulging portions (41E) and (41G) serve as heat carrier inlet header sections (43A) of the rear heat exchange section (11), and the rear portions of the tanks (17) and (18) including the sixth and eighth bulging portions (41F) and (41H) serve as heat carrier outlet header sections (43B) of the rear heat exchange section (11). In other words, the heat carrier inlet header section (43A) and the heat carrier outlet header section (43B) are formed in the right header tank (13B) of the rear heat exchange section (11) such that they are separated from each- other in the vertical direction, and the heat carrier outlet header section (43B) and the heat carrier inlet header section (43A) are formed in the left header tank (13A) of the rear heat exchange section (11) such that they are separated from each other in the vertical direction. Therefore, the front heat exchange section (10) has a first path (44A) and a second path (44B). The first path (44A) includes an upper half of the corresponding heat exchange tubes (14) communicating with the upper heat carrier inlet header section (42A) and the upper heat carrier outlet header section (42B). The second path (44B) includes a lower half of the corresponding heat exchange tubes (14) communicating with the lower heat carrier inlet header section (42A) and the lower heat carrier outlet header section (42B). The rear heat exchange section (11) has a first path (45A) and a second path (45B). The first path (45A) includes an upper half of the corresponding heat exchange tubes (14) communicating with the upper heat carrier inlet header section (43A) and the upper heat carrier outlet header section (43B). The second path (45B) includes a lower half of the corresponding heat exchange tubes (14) communicating with the lower heat carrier inlet header section (43A) and the lower heat carrier outlet header section (43B). The first paths (44A) and (45A) of the heat exchange sections (10) and (11) are provided at the same height and the second paths (44B) and (45B) of the heat exchange sections (10) and (11) are provided at the same height. In other words, the first paths (44A) and (-45A) are provided at the same position with respect to the longitudinal direction of the header tanks (12A), (12B), (13A), and (13B), and the second paths (44B) and (45B) are provided a the same position with respect to the longitudinal direction thereof. Moreover, the flow direction of the heat carrier in the first path (44A) of the front heat exchange section (10) and that in the first path (45A) of the rear heat exchange section (11) are opposite each other. Similarly, the flow direction of the heat carrier in the second path (44B) of the front heat exchange section (10) and that in the second path (45B) of the rear heat exchange section (11) are opposite each other. Further, heat carrier inlet pipes (35) branching from a piping extending from the compressor (1) are connected the heat carrier inlet header sections (42A) and (43A) of the front and rear heat exchange sections (10) and (11) such that the pipes (35) are inserted into the corresponding heat carrier inlets (25). Similarly, heat carrier outlet pipes (36) merging into a piping extending to the expansion valve (3) are connected to the heat carrier outlet header sections (42B) and (43B) such that the pipes (36) are inserted into the corresponding heat carrier outlets (26).

In the above mentioned heating cycle, as shown in FIG. 15, high-temperature, high-pressure CO₂ having been compressed by the compressor (1) flows into the interiors of the heat carrier inlet header sections (42A) of the header tanks (12A) and (12B) of the front heat exchange section (10) and the interiors of the heat carrier inlet header sections (43A) of the header tanks (13A) and (13B) of the rear heat exchange section (11) trough the heat carrier inlet pipe (35) The CO₂ which has entered the interior of the upper heat carrier inlet header section (42A) of the front heat exchange section (10) flows rightward through the heat exchange tubes (14) of the first path (44A) and enters the interior of the upper heat carrier outlet header section (42B). The CO₂ which has entered the interior of the lower heat carrier inlet header section (42A) of the front heat exchange section (10) flows leftward through the heat exchange tubes (14) of the second path (44B) and enters the interior of the lower heat carrier outlet header section (42B). The CO₂ which has entered the interior of the upper heat carrier inlet header section (43A) of the rear heat exchange section (11) flows leftward through the heat exchange tubes (14) of the first path (45A) and enters the interior of the upper heat carrier outlet header section (43B). The CO₂ which has entered the interior of the lower heat carrier inlet header section (43A) of the rear heat exchange section (11) flows rightward through the heat exchange tubes (14) of the second path (45B) and enters the interior of the lower heat carrier outlet header section (43B). The CO₂ which has entered the heat carrier outlet header sections (42B) and (43B) flows out to the heat carrier outlet pipe (36) and is fed to the expansion valve ( 3 ) . While flowing through the heat exchange tubes (14), the CO₂ is subjected to heat exchange with the to-be- conditioned air flowing through the adjacent air-passing clearances in the direction of arrow X shown in FIGS. 12 and 15, and the to-be-conditioned air is thereby heated.

Since the heat capacity of CO₂ is small, the temperature of the CO₂ which flows through the heat exchange tubes (14) decreases rapidly from the heat carrier inlet header sections (42A) and (43A) toward the heat carrier outlet header sections (42B) and (43B). Consequently, the blowing-out temperature of the conditioned air which has passed through the heat exchange section (10) and (11) decreases from the heat carrier inlet header section (42A) and (43A) toward the heat carrier outlet header section (42B) and (43B), whereby the temperature distribution becomes non-uniform. However, in the upper portion of the front heat exchange section (10), the temperature of the CO₂ and the blowing-out temperature of the conditioned air decrease from the left side toward the right side; and in the upper portion of the rear heat exchange section (11), the temperature of the CO₂ and the blowing-out temperature of the conditioned air decrease from the right side to the left side. Moreover, in the lower portion of the front heat exchange section (10), the temperature of the CO₂ and the blowing-out temperature of the conditioned air decrease from the right side toward the left side; and in the lower portion of the rear heat exchange section (11), the temperature of the CO₂ and the blowing-out temperature of the conditioned air decrease from the left side to the right side. Therefore, variation in the temperature of the conditioned air having passed through the heat exchange section (10) and variation in the temperature of the conditioned air having passed through the heat exchange section (11) are canceled out each other. As a result, the temperature distribution of the conditioned air having passed through the in-compartment heat exchanger (40) becomes uniform.

Incidentally, the in-compartment heat exchanger (2) and (40) of the above mentioned respective embodiment 1 and 2 may be used in a posture such that the longitudinal direction of the heat exchange tube (14) coincides with the vertical direction.

Next will be described modified example of the heat exchange tubes used in the in-compartment heat exchangers (2) and (40) of Embodiments 1 and 2. In the following description concerning modified example of the heat exchange tubes, upper, lower, left-hand, and right-hand in each drawing will be referred to as "upper" (or a similar expression) , "lower" (or a similar expression) , "left" (or a similar expression), and "right" (or a similar expression), respectively.

A heat exchange tube (50) shown in FIGS. 16 and 17 includes mutually opposed flat upper and lower walls (51) and (52) (a pair of flat walls); left and right side walls (53) and (54) that extend over left and right side ends, respectively, of the upper and lower walls (51) and (52); and a plurality of' reinforcement walls (55) that are provided at predetermined intervals between the left and right side walls (53) and (54) and extend longitudinally and between the upper and lower walls (51) and (52). By virtue of this structure, the heat exchange tube (50) internally has a plurality of heat-carrier channels (56) arranged in the width direction thereof. The reinforcement walls (55) serve as partition walls between adjacent heat-carrier channels (56). The width of each heat-carrier channel (56), except for the heat- carrier channel at the right end portion, remains unchanged along the entire height thereof.

The left side wall (53) has a dual structure and includes an outer side-wall-forming elongated projection (57) that is integrally formed with the left side end of the upper wall (51) in a downward raised condition and extends along the entire height of the heat exchange tube (50); an inner side-wall-forming elongated projection (58) that is located inside the outer side-wall-forming elongated projection (57) and is integrally formed with the upper wall (51) in a downward raised condition; and an inner side-wall-forming elongated projection (59) that is integrally formed with the left side end of the lower wall (52) in an upward raised condition. The outer side-wall-forming elongated projection (57) is brazed to the two inner side-wall-forming elongated projections (58) and (59) and the lower wall (52) while a lower end portion thereof is engaged with a left side edge portion of the lower surface of the lower wall (52). The two inner side-wall-forming elongated projections (58) and (59) are brazed together while butting against each other. A right side wall (54) is integrally formed with the upper and lower walls (51) and (52). A projection (59a) is integrally formed on the tip end face of the inner side-wall-forming projection (59) of the lower wall (52) and extends in the longitudinal direction of the inner side-wall-forming projection (59) along the entire length thereof. A groove (58a) is formed on the tip end face of the inner side-wall- forming elongated projection (58) of the upper wall (51) and extends in the longitudinal direction of the inner side-wall- forming elongated projection (58) along the entire length thereof. The projection (59a) is press-fitted into the groove (58a) .

Each of the reinforcement walls (55) is formed such that a reinforcement-wall-forming elongated projection (60), which is integrally formed with the upper wall (51) in a downward raised condition, and a reinforcement-wall-forming elongated projection (61), which is integrally formed with the lower wall (52) in an upward raised condition, are brazed together while butting against each other.

The heat exchange tube (50) is manufactured by use of a heat-exchange-tube-forming metal sheet (65) as shown in FIG. 18(a). The heat-exchange-tube-forming metal sheet (65) is formed by performing rolling on an aluminum brazing sheet having a brazing material layer over each of opposite surfaces thereof. The tube-forming metal sheet (65) includes a flat upper-wall-forming portion (66) (flat-wall-forming portion); a lower-wall-forming portion (67) (flat-wall- forming portion); a connection portion (68) connecting the upper-wall-forming portion (66) and the lower-wall-forming portion (67) and adapted to form the right side wall (54); the inner side-wall-forming elongated projections (58) and (59), which are integrally formed with the side ends of the upper-wall-forming and lower-wall-forming portions (66) and (67) opposite the connection portion (68) in an upward raised condition and which are adapted to form an inner portion of the left side wall (53); an outer side-wall-forming- elongated-projection forming portion (69), which extends in the left-right direction (rightward) from the side end (right side end) of the upper-wall-forming portion (66) opposite the connection portion (68); and a plurality of reinforcement- wall-forming elongated projections (60) and (61), which are integrally formed with the upper-wall-forming portion (66) and lower-wall-forming portions (67) in an upward raised condition and which are arranged at predetermined intervals in the left-right direction. The reinforcement-wall-forming elongated projections (60) of the upper-wall-forming portion (66) and the reinforcement-wall-forming elongated projections (61) of the lower-wall-forming portion (67) are located symmetrically with respect to the centerline of the connection portion (68) in the width direction. The projection (59a) is formed on the tip end face of the inner side-wall-forming elongated projection (59) of the lower- wall-forming portion (67), and the groove (58a) is formed on the tip end face of the inner side-wall-forming elongated projection (58) of the upper-wall-forming portion (66). The two inner side-wall-forming elongated projections (58) and (59) and all the reinforcement-wall-forming elongated projections (60) and (61) have the same height. The vertical thickness of the connection portion (68) is greater than the thickness of the upper-wall-forming and lower-wall-forming portions (65) and (66), and its upper end is located at the same height as the upper ends of the inner side-wall-forming elongated projections (58) and (59) and the reinforcement- wall-forming elongated projections (60) and (61).

The inner side-wall-forming elongated projections (58) and (59) and the reinforcement-wall-forming elongated projections (60) and (61) are integrally formed, through rolling, on one side of the aluminum brazing sheet whose opposite surfaces are clad with a brazing material, whereby brazing material layers (unillustrated) are formed on the opposite side surfaces and tip end faces of the inner side- wall-forming elongated projections (58) and (59), on those of the reinforcement-wall-forming elongated projections (60) (61), and on the vertically opposite surfaces of the upper- wall-forming and lower-wall-forming portions (65) and (66) and the outer side-wall-forming-elongated-projection forming portion (69).

The heat-exchange-tube-forming metal sheet (65) is gradually folded at left and right side edges of the connection portion (68) by a roll forming process (see FIG. 18(b)) until a hairpin form is assumed. The inner side-wall- forming elongated projections (58) and (59) are caused to butt against each other; the reinforcement-wall-forming elongated projections (60) and (61) are caused to butt against each other; and the projection (59a) is caused to be press-fitted into the groove (58a).

Next, the outer side-wall-forming-elongated-projection forming portion (69) is folded along the outer surfaces of the inner side-wall-forming elongated projections (58) and (59), and a tip end portion thereof is deformed so as to be engaged with the lower-wall-forming portion (67), thereby yielding a folded member (70) (see FIG. 18(c)).

Subsequently, the folded member (70) is heated at a predetermined temperature so as to braze together tip end portions of the inner side-wall-forming elongated projections (58) and (59); to braze together tip end portions of the reinforcement-wall-forming elongated projections (60) and (61); and to braze the outer side-wall-forming-elongated- projection forming portion (69) to the inner side-wall- forming elongated projections (58) and (59) and to the lower- wall-forming portion (67). Thus is manufactured the heat exchange tube (50). The heat exchange tubes (50) are manufactured in the course of manufacture of the heat exchanger (2) and (40).

In the case of a heat exchange tube (75) shown in FIG. 19, a projection (76) extending along the entire length thereof and a groove (77) extending along the entire length thereof are alternately formed on the tip end faces of all the reinforcement-wall-forming elongated projections (60) of the upper wall (51). A groove (78) into which the corresponding projection (76) of the reinforcement-wall- forming elongated projection (60) of the upper wall (51) is fitted and a projection (79) to be fitted into the corresponding groove (77) of the reinforcement-wall-forming elongated projection (60) of the upper wall (51) are alternately formed on the tip end faces of all the reinforcement-wall-forming elongated projections (61) of the lower wall (52), along the entire length thereof. Other structural features are similar to those of the heat exchange tube (50) shown in FIGS. 16 and 17. The heat exchange tube (75) is manufactured in a manner similar to that for the heat exchange tube (50) shown in FIGS. 16 and 17.

In a heat exchange tube (80) shown in FIGS. 20 and 21, the reinforcement wall (55) formed such that a reinforcement- wall-forming elongated projection (81) formed integrally with the upper wall (51) and in a downward raised condition is brazed to the lower wall (52), and the reinforcement wall (55) formed such that a reinforcement-wall-forming elongated projection (82) formed integrally with the lower wall (52) and in an upward raised condition is brazed to the upper wall (51), are alternately provided in the left-right direction; the upper and lower walls (51) and (52) have projections (83) extending along the entire length thereof and formed integrally at portions thereof that abut the corresponding reinforcement-wall-forming elongated projections (82) and (81); grooves (84) are formed on the corresponding tip end faces of the projections (83) so as to allow corresponding tip end portions of the reinforcement-wall-forming elongated projections (81) and (82) to be fitted thereinto; and the tip end portions of the reinforcement-wall-forming elongated projections (81) and (82) are brazed to the corresponding projections (83) while being fitted into the grooves (84) of the projections (83). The thickness of the projection (83) as measured in the left-right direction is slightly greater than that of the reinforcement-wall-forming elongated projections (81) and (82). Other structural features of the heat exchange tube (80) are similar to those of the heat exchange tube (50) shown in FIGS. 16 and 17. In this heat exchange tubes (80), the width of each of the heat-carrier channels (56) (except for the heat-carrier channel at the right end portion) is not uniform along the height of the heat-carrier channel (56). The minimum channel width Wp of these heat-carrier channel (56) means the width of the heat- carrier channel (56) as measured at a certain height where the heat-carrier channel (56) is the narrowest; i.e., the distance between the reinforcement-wall-forming elongated projection (81) or (82) and the projection (83) to which the adjacent reinforcement-wall-forming elongated projection (82) or (81) is brazed. Moreover, the thickness of the reinforcement-wall-forming elongated projections (81) and (82) each of which forms the reinforcement wall (55) is referred to as the thickness Tw of the partition wall between the adjacent heat-carrier channels (56).

The heat exchange tube (80) is manufactured by use of a heat-exchange-tube-forming metal sheet (85) as shown in FIG. 22(a) . The tube-forming metal sheet (85) is formed by- performing rolling on an aluminum brazing sheet having a brazing material layer over each of opposite surfaces thereof. The tube-forming metal sheet (85) includes a plurality of reinforcement-wall-forming elongated projections (81) and (82), which are integrally formed with the upper-wall-forming and lower-wall-forming portions (66) and (67) in an upward raised condition and which are arranged at predetermined intervals in the left-right direction. The reinforcement- wall-forming elongated projections (81) of the upper-wall- forming portion (66) and the reinforcement-wall-forming elongated projections (82) of the lower-wall-forming portion (67) are located asymmetrically with respect to the centerline of the connection portion (68) in the width direction. The reinforcement-wall-forming elongated projections (81) and (82) have the same height, which is about two times the height of the inner side-wall-forming elongated projections (58) and (59). The projections (83) are integrally formed, in such a manner as to extend along the entire length of the upper-wall-forming and lower-wall- forming portions (66) and (67), at those portions of the upper-wall-forming and lower-wall-forming portions (66) and (67) which the^' corresponding reinforcement-wall-forming elongated projections (82) and (81) of the lower-wall-forming and upper-wall-forming portions (67) and (66) abut. The grooves (84) are formed on the corresponding tip end faces of the projections (83) so as to allow corresponding tip end portions of the reinforcement-wall-forming elongated projections (82) and (81) to be fitted thereinto. Other structural features of the tube-forming metal sheet (85) are similar to those of the tube-forming metal sheet (65) shown in FIG. 18.

The tube-forming metal sheet (85) is gradually folded at left and right side edges of the connection portion (68) by a roll forming process (see FIG. 22(b)) until a hairpin form is assumed. The inner side-wall-forming elongated projections (58) and (59) are caused to butt against each other, and the projection (59a) is caused to be press-fitted into the groove (58a). Also, tip end portions of the reinforcement-wall-forming elongated projections (81) of the upper-wall-forming portion (66) are caused to be fitted into the corresponding grooves (84) of the projections (83) of the lower-wall-forming portion (67), and tip end portions of the reinforcement-wall-forming elongated projections (82) of the lower-wall-forming portion (67) are caused to be fitted into the corresponding grooves (84) of the projections (83) of the upper-wall-forming portion (66).

Next, the outer side-wall-forming-elongated-projection forming portion (69) is folded along the outer surfaces of the inner side-wall-forming elongated projections (58) and (59), and a tip end portion thereof is deformed so as to be engaged with the lower-wall-forming portion (67), thereby yielding a folded member (86) (see FIG. 22(c)).

Subsequently, the folded member (86) is heated at a predetermined temperature so as to braze together tip end portions of the inner side-wall-forming elongated projections (58) and (59); to braze tip end portions of the reinforcement-wall-forming elongated projections (81) and (82) to the corresponding projections (83); and to braze the outer side-wall-forming-elongated-projection forming portion (69) to the inner side-wall-forming elongated projections (58) and (59) and to the lower-wall-forming portion (67). Thus is manufactured the heat exchange tube (80). The heat exchange tubes (80) are manufactured in the course of manufacture of the in-compartment heat exchanger (2) and (40)

The reinforcement walls (55) of a heat exchange tube (90) shown in FIGS. 23 and 24 are formed such that reinforcement-wall-forming elongated projections (91), (92) formed integrally with the upper wall (51) and in a downward raised condition are caused to butt against and brazed to reinforcement-wall-forming elongated projections (93), (94) formed integrally with the lower wall (52) and in an upward raised condition. The high and low reinforσement-wall- forming elongated projections (91) and (92), which differ in projection height, are alternately provided in the left-right direction on the upper wall (51), and the high and low reinforcement-wall-forming elongated projections (93) and (94), which differ in projection height, are alternately provided in the left-right direction on the lower wall (52). The reinforcement-wall-forming elongated projections (91) of large projection height on the upper wall (51) are brazed to the reinforcement-wall-forming elongated projections (94) of small projection height on the lower wall (52); and the reinforcement-wall-forming elongated projections (92) of small projection height on the upper wall (51) are brazed to the reinforcement-wall-forming elongated projections (93) of large projection height on the lower wall (52). Hereinbelow, the reinforcement-wall-forming elongated projections (91), (93) of large projection height provided on the upper and lower walls (51) and (52), respectively, are called "first reinforcement-wall-forming elongated projections," and the reinforcement-wall-forming elongated projections (92), (94) of small projection height provided on the upper and lower walls (51) and (52), respectively, are called "second reinforcement-wall-forming elongated projections." Grooves (95), (96), which extend along the longitudinal direction, are formed on the corresponding tip end faces of the second reinforcement-wall-forming elongated projections (92), (94) of the upper and lower walls (51), (52) over the entire length so as to receive the corresponding tip end portions of the first reinforcement-wall-forming elongated projections (93), (91) of the lower and upper walls (52), (51). The reinforcement-wall-forming elongated projections (91) (94), and the reinforcement-wall-forming elongated projections (92), (93) are brazed together in a state in which the corresponding tip end portions of the first reinforcement- wall-forming elongated projections (91), (93) of the upper and lower walls (51) and (52) are fitted into the grooves (96), (95). Other structural features of the heat exchange tube (90) are similar to those of the heat exchange tube (50) shown in FIGS. 16 and 17.

In the heat exchange tube (90), the width of each of the heat-carrier channels (56), except for the heat-carrier channel (56) at the right end, is not uniform along the height of the heat-carrier channel (56). The minimum channel width Wp of these heat-carrier channels (56) means the width of the heat-carrier channel (56) as measured at a certain height where the heat-carrier channel (56) is the narrowest; i.e., the distance between the first reinforcement-wall- forming elongated projection (91) or (93) and the second reinforcement-wall-forming elongated projection (92) or (94) adjacent thereto. The thickness of each of the first reinforcement-wall-forming elongated projections (91), (93) is the thickness of a partition wall between the adjacent heat-carrier channels (56).

In the heat exchange tube (90), the grooves (95), (96) extent over the entire height of the second reinforcement- wall-forming elongated projections (92) and (94); however, the present invention is not limited thereto, and the depth of the grooves (95), (96) may be smaller than the height of the second reinforcement-wall-forming elongated projections ( 92 ) and ( 94 ) .

The heat exchange tube (90) is manufactured by use of a heat-exchange-tube-forming metal sheet (98) as shown in FIG. 25(a). The heat-exchange-tube-forming metal sheet (98) is formed by performing rolling on an aluminum brazing sheet having a brazing material layer over opposite surfaces thereof. The heat-exchange-tube-forming metal sheet (98) includes a plurality of reinforcement-wall-forming elongated projections (91), (92), (93), (94), which are integrally formed with the upper-wall-forming and lower-wall-forming portions (66), (67) in an upward raised condition and which are arranged at predetermined intervals in the left-right direction. The first reinforcement-wall-forming elongated projections (91) of the upper-wall-forming portion (66) and the second reinforcement-wall-forming elongated projections (94) of the lower-wall-forming portion (67) are located symmetrically with respect to the centerline of the connection portion (68) in the width direction. Similarly, the second reinforcement-wall-forming elongated projections (92) of the upper-wall-forming portion (66) and the first reinforcement-wall-forming elongated projections (93) of the lower-wall-forming portion (67) are located symmetrically with respect to the centerline of the connection portion (68) in the width direction. The grooves (95), (96) are formed on the corresponding tip end faces of the second reinforcement- wall-forming elongated projections (92), (94) of the upper- wall-forming and lower-wall-forming portions (66), (67) so as to allow corresponding tip end portions of the first reinforcement-wall-forming elongated projections (93), (91) of the lower-wall-forming and upper-wall-forming portions (67), (66) to be fitted thereinto. Other structural features of the heat-exchange-tube-forming metal sheet (98) are similar to those of the heat-exchange-tube-forming metal sheet (65) shown in FIG. 18.

The heat-exchange-tube-forming metal sheet (98) is gradually folded at left and right side edges of the connection portion (68) by a roll forming process (see FIG. 25(b)) until a hairpin form is assumed. The inner side-wall- forming elongated projections (58), (59) are caused to butt against each other. Also, tip end portions of the first reinforcement-wall-forming elongated projections (91), (93) are caused to be fitted into the corresponding grooves (96), (95) of the second reinforcement-wall-forming elongated projections (94), (92). Further, the projection (59a) is caused to be press-fitted into the groove (58a).

Next, the outer side-wall-forming-elongated-projection forming portion (69) is folded along the outer surfaces of the inner side-wall-forming elongated projections (58), (59), and a tip end portion thereof is deformed so as to be engaged with the lower-wall-forming portion (67), thereby yielding a folded member (99) (see FIG. 25(c)).

Subsequently, the folded member (99) is heated at a predetermined temperature so as to braze together tip end portions of the inner side-wall-forming elongated projections (58), (59); to braze tip end portions of the first reinforcement-wall-forming elongated projections (91), (93) to tip end portions of the second reinforcement-wall-forming elongated projections (94), (92); and to braze the outer side-wall-forming-elongated-projection forming portion (69) to the inner side-wall-forming elongated projections (58), (59) and to the lower-wall-forming portion (67). Thus is manufactured the heat exchange tube (90). The heat exchange tubes (90) are manufactured in the course of manufacture of the heat exchanger (2), (40).

In the above mentioned heat exchangers (50), (75), (80), and (90), the above mentioned relationships 1 to 7 are satisfied.

INDUSTRIAL APPLICABILITY

The heat exchanger according to the present invention is preferably used for heating to-be-conditioned air by a supercritical heating cycle which, for example, uses CO₂ as a heat carrier.

Claims

1. A heat exchanger comprising first and second heat exchange sections arranged side-by-side in an air flow direction, each heat exchange section including first and second header tanks separated from each other and a plurality of heat exchange tubes which are disposed between the header tanks at predetermined intervals in the length direction of the header tanks and whose opposite ends are connected to the corresponding header tanks , wherein each heat exchange section is configured such that a fluid fed into the first header tank flows to the second header tank via the heat exchange tubes and flows out of the second header tank; each heat exchange section includes at least one path composed of a plurality of heat exchange tubes successively arranged; the two heat exchange sections are the same in the number of paths; the paths of the two heat exchange sections are provided on the same location to correspond to each other; the fluid flows in the same direction through the plurality of heat exchange tubes forming each path; and the flow direction of the fluid flowing through the path of the first heat exchange section is opposite the flow direction of the fluid flowing through the path of the second heat exchange section located at a position corresponding to the path of the first heat exchange section.

2. A heat exchanger according to claim 1, wherein each heat exchange section includes a single path.

3. A heat exchanger according to claim 2, wherein one header section is provided on each of the first and second header tanks of each heat exchange section; the opposite ends of all the heat exchange tubes constituting a single path are connected to the corresponding header tanks for communication with the corresponding header sections; one header section of each heat exchange section serves as an input header section, and the other header section of each heat exchange section serves as an output header section; the inlet header section of the first heat exchange section and the outlet header section of the second heat exchange section are arranged side-by-side in the air flow direction, and the outlet header section of the first heat exchange section and the inlet header section of the second heat exchange section are arranged side-by-side in the air flow direction; a fluid inlet pipe is connected to the inlet header section of each heat exchange section, and a fluid outlet pipe is connected to the outlet header section of each heat exchange section.

4. A heat exchanger according to claim 1, wherein each heat exchange section includes a plurality of paths; and the flow directions of the fluid at adjacent paths of each heat exchange section are opposite each other.

5. A heat exchanger according to claim 4, wherein the same number of plural header sections are provided on each of the first and second header tanks of each heat exchange section; the opposite ends of all the heat exchange tubes constituting each path are connected to the corresponding header tanks for communication with the corresponding header sections; one header section of the first header tank communicating with all the heat exchange tubes of each path serves as an input header section communicate, and the corresponding header section of the second header tank serves as an output header section; each header tank includes the inlet header section and the outlet header section alternately arranged; the inlet header sections of the first heat exchange section and the outlet header sections of the second heat exchange section are arranged side-by-side in the air flow direction, and the outlet header sections of the first heat exchange section and the inlet header sections of the second heat exchange section are arranged side-by-side in the air flow direction; a fluid inlet pipe is connected to the inlet header sections of each heat exchange section, and a fluid outlet pipe is connected to the outlet header sections of each heat exchange section.

6. A heat exchanger according to claim 1 , wherein the header tanks of the two heat exchange sections are integrated together.

7. A heat exchanger according to claim 1 , wherein each heat exchange tube has a flat shape such that its width direction coincides with the air flow direction and has a plurality of fluid channels arranged therein along the width direction thereof; each of the fluid channels has a vertically elongated cross section; and when the quotient produced by dividing a channel height Hp (mm) of the fluid channel by a minimum channel width Wp (mm) of the fluid channel is defined as "aspect ratio," the aspect ratio (Hp/Wp) is 1.05 to 2.

8. A heat exchanger according to claim 7 , satisfying a relation 0.5 ≤ Tw/Wp ≤ 1.5, where Tw (mm) is the thickness of a partition wall between the adjacent fluid channels of each of the heat exchange tubes, and Wp (mm) is the minimum channel width of each of the fluid channels.

9. A heat exchanger according to claim 7 , satisfying a relation 0.3 ≤ Hp/Ht ≤ 0.7, where Hp (mm) is the channel height of each of the fluid channels of each of the heat exchange tubes, and Ht (mm) is the tube height of each of the heat exchange tubes .

10. A heat exchanger according to claim 7, satisfying a relation 0.5 ≤ Sp ≤ 5, where Sp (mm²) is the total channel cross-sectional-area of all the fluid channels of each of the heat exchange tubes .

11. A heat exchanger according to claim 7, satisfying a relation Sp/Sb ≤ 0.5, where Sp (mm²) is the total channel cross-sectional-area of all the fluid channels of each of the heat exchange tubes, and Sb (mm²) is the remaining area (cross-sectional area of a bulk portion) after subtracting the total channel cross-sectional-area Sp (mm²) from the entire cross-sectional area of each of the heat exchange tubes .

12. A heat exchanger according to claim 7, satisfying a relation (Wt x Ht) /3 ≥ Sp, where Sp (mm²) is the total channel cross-sectional-area of all the fluid channels of each of the heat exchange tubes; Ht (mm) is the tube height of each of the heat exchange tubes; and Wt (mm) is the tube width of each of the heat exchange tubes .

13. A heat exchanger according to claim 7, satisfying a relation Ht ≤ 4, where Ht (mm) is the tube height of each of the heat exchange tubes .

14. A heat exchanger according to claim 7, wherein each of the heat exchange tubes includes two flat walls in parallel with each other; first and second side walls extending over corresponding side ends of the two flat walls ; and reinforcement walls provided between the first and second side walls and extending between the two flat walls and in the longitudinal direction of the two flat walls; and each of the heat exchange tubes is formed from a single metal sheet including two flat-wall-forming portions; a connection portion connecting the two flat-wall-forming portions and adapted to form the first side wall; two side- wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the flat-wall-forming portions opposite the connection portion, and adapted to form the second side wall; and a plurality of reinforcement-wall-forming elongated projections provided integrally with the flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections; and the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side- wall-forming elongated projections butt against each other and such that the reinforcement-wall-forming elongated projections butt against each other, and by brazing the mutually butting side-wall-forming elongated projections together and the mutually butting reinforcement-wall-forming elongated projections together, the mutually brazed reinforcement-wall-forming elongated projections forming the reinforcement walls .

15. A heat exchanger according to claim 14, wherein of two reinforcement-wall-forming elongated projections which form each reinforcement wall, one reinforcement-wall-forming elongated projection has a groove which is formed on the tip end face thereof so as to receive a tip end portion of the other reinforcement-wall-forming elongated projection.

16. A heat exchanger according to claim 7, wherein each of the heat exchange tubes includes two flat walls in parallel with each other; first and second side walls extending over corresponding side ends of the two flat walls ; and reinforcement walls provided between the first and second side walls and extending between the two flat walls and in the longitudinal direction of the two flat walls; and each of the heat exchange tubes is formed from a single metal sheet including first and second flat-wall-forming portions; a connection portion connecting the first and second flat-wall-forming portions and adapted to form the first side wall; two side-wall-forming elongated projections provided integrally with and in such a manner as to project from corresponding side ends of the first and second flat- wall-forming portions opposite the connection portion, and adapted to form the second side wall; and a plurality of reinforcement-wall-forming elongated projections provided integrally with the first and second flat-wall-forming portions in such a manner as to project in the same direction as the side-wall-forming elongated projections; and the heat exchange tube is formed by folding the metal sheet at the connection portion into a hairpin form such that the side- wall-forming elongated projections butt against each other, and by brazing the mutually butting side-wall-forming elongated projections together, brazing the reinforcement- wall-forming elongated projections of the first flat-wall- forming portion to the second flat-wall-forming portion, and brazing the reinforcement-wall-forming elongated projections of the second flat-wall-forming portion to the first flat- wall-forming portion, the reinforcement-wall-forming elongated projections brazed to the first and second flat- wall-forming portions forming the reinforcement walls.

17. A heat exchanger according to claim 16, wherein projections are integrally formed, in such a manner as to extend along the entire length of the first and second flat- wall-forming portions, at those portions of the first and second flat-wall-forming portions which the corresponding reinforcement-wall-forming elongated projections of the second and first flat-wall-forming portions abut; grooves are formed on the corresponding tip end faces of the projections so as to receive corresponding tip end portions of the reinforcement-wall-forming elongated projections; arid while being fitted into the corresponding grooves , the tip end portions of the reinforcement-wall-forming elongated projections are brazed to the corresponding projections.

18. A heat exchanger according to claim 7, wherein corrugate fins each including wave crest portions, wave trough portions, and connection portions each connecting together a wave crest portion and a wave trough portion are each arranged between the adjacent heat exchange tubes; the fin height of the individual corrugate fins is 3 mm to 8 mm; the fin pitch of the individual corrugate fins is 0.5 mm to 1.5 mm; and the thickness of each of the corrugate fins is 0.05 mm to 0.1 mm.

19. A heat exchanger according to claim 18, wherein the corrugate fins are disposed to across the two heat exchange sections, and shared by the heat exchange tubes of the heat exchange sections .

20. A heat exchanger according to claim 19, wherein a heat transmission reducing portion is formed on each corrugate fin between the two heat exchange sections.

21. A heat exchanger according to claim 20, wherein the heat transmission reducing portion is formed of a slit.

22. A supercritical heating cycle which comprises a compressor, an in-compartment heat exchanger to which a high temperature, high pressure heat carrier having been compressed by the compressor is fed, a pressure-reducing device for depressurizing the heat carrier flowing out of the in-compartment heat exchanger, and an out-compartment heat exchanger for cooling the depressurized heat carrier and in which a supercritical heat carrier is used, wherein the in- compartment heat exchanger is a heat exchanger according to any one of claims 1 to 21.