CN111556950A

CN111556950A - Heat exchanger for refrigerator

Info

Publication number: CN111556950A
Application number: CN201880085577.3A
Authority: CN
Inventors: 上田薫; 笹崎干根; 荻原加奈
Original assignee: UACJ Corp
Current assignee: UACJ Corp
Priority date: 2018-02-13
Filing date: 2018-12-13
Publication date: 2020-08-18
Also published as: JP2019138582A; WO2019159520A1

Abstract

Provided is a heat exchanger for a refrigerator-freezer, which can be miniaturized when heat exchange performance equivalent to that of the prior art is sought, and can be realized in an occupied volume equivalent to that of the prior art when heat exchange performance higher than that of the prior art is sought. The heat exchanger for a refrigerator/freezer comprises a plurality of fin groups (2) composed of a plurality of fins (20) arranged in parallel in a row at a predetermined interval, wherein the plurality of fin groups (2) are arranged at a predetermined interval in the X direction which is the flow direction of a cooling target fluid flowing in the refrigerator/freezer, and the heat exchanger comprises 1 or more metal pipes (3) arranged in a serpentine shape so as to sequentially penetrate the fins (20) in the fin groups (2). The fins (20) are formed of a rectangular plate made of aluminum or an aluminum alloy having a short side with a length of 25mm or less in the X direction, and the shortest distance from 4 corners (23) of the rectangle to the outer peripheral surface of the metal pipe (3) penetrating the fins (20) is in the range of 12.0 to 17.5 mm.

Description

Heat exchanger for refrigerator

Technical Field

The present invention relates to a heat exchanger for a refrigerator-freezer.

Background

A serpentine heat exchanger is generally used as a heat exchanger mounted in a refrigerator-freezer. The serpentine heat exchanger is constituted by a plurality of plate fins arranged in parallel in 1 row at a predetermined interval from each other, and 1 or more metal pipes penetrating these fins and allowing a refrigerant to flow therethrough. Further, it is configured as follows: a fin group consisting of a plurality of fins arranged in 1 row is arranged in multiple layers, and the air in the refrigerator as the fluid to be cooled flows in the arrangement direction of the fin group and sequentially passes through the multiple layers of fin groups.

In a refrigerator-freezer, a heat exchanger is required to be downsized in order to increase the internal volume for accommodating foods and the like as much as possible while maintaining sufficient refrigerating and freezing performance. On the other hand, in the freezer-refrigerator, since the temperature of the heat exchanger is sometimes lower than 0 degrees, water vapor contained in the air adheres to the fins of the heat exchanger to turn into frost. In such a special use environment, it is not considered necessary to provide a structure that improves the refrigerating and freezing performance, i.e., the heat exchange performance and can be made compact.

For example, patent document 1 proposes to define an appropriate fin pitch and provide a special coating layer on the surface of the fin in order to suppress a decrease in heat exchange performance due to condensation. However, as described above, in the heat exchanger for the freezer-refrigerator in which adhesion of frost cannot be avoided, sufficient effects cannot be obtained by the configuration of patent document 1.

(prior art documents)

(patent document)

Patent document 1: WO2012/014934A1

Disclosure of Invention

(problems to be solved by the invention)

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heat exchanger for a refrigerator-freezer, which can improve heat exchange performance per unit volume of a volume occupied by the heat exchanger, can reduce the size of the heat exchanger when heat exchange performance equivalent to that of the related art is required, and can realize the heat exchanger in an occupied volume equivalent to that of the related art when heat exchange performance higher than that of the related art is required.

(means for solving the problems)

One aspect of the present invention is a heat exchanger for a refrigerator-freezer, comprising a plurality of fin groups each of which is formed of a plurality of fins arranged in parallel at a predetermined interval in a row, wherein the plurality of fin groups are arranged at a predetermined interval in an X direction which is a flow direction of a fluid to be cooled flowing in the refrigerator-freezer, wherein the plurality of fin groups are arranged at a predetermined interval in a serpentine shape in which the fins in the fin groups sequentially penetrate, wherein the fins are formed of a rectangular plate made of aluminum or an aluminum alloy, wherein the rectangular plate has a short side having a length of 25mm or less in the X direction, and wherein the shortest distance from 4 corners of the rectangular plate to an outer peripheral surface of the metal pipe penetrating the fins is in a range of 12.0 to 17.5 mm.

(effect of the invention)

In the heat exchanger for a refrigerator-freezer, the shape of the fins is a rectangle whose short side length is limited to the specific value or less, and the positional relationship between the corners of the rectangle of the fins and the metal pipes is limited to the specific range, so that the heat exchange performance in the refrigerator-freezer can be improved compared to the conventional one. This has been confirmed by a number of experiments, some of which are shown in the examples described below. Further, by using the heat exchanger for a refrigerator-freezer as described above, the heat exchanger can be downsized in the case of pursuing heat exchange performance equivalent to that of the conventional one, and can be realized in the occupied volume equivalent to that of the conventional one in the case of pursuing heat exchange performance higher than that of the conventional one. Therefore, the heat exchanger configured as described above is very suitable for use in a refrigerator-freezer.

Drawings

Fig. 1 is an explanatory diagram showing a structure of a heat exchanger for a freezer-refrigerator in embodiment 1.

Fig. 2 is an explanatory diagram showing a dimensional relationship of the fin of example 1.

Fig. 3 (a) is an explanatory view showing the structure of the heat exchanger for a freezer-refrigerator in example 1, (b) is an explanatory view showing the structure of the heat exchanger for a freezer-refrigerator in comparative example 1, and (c) is an explanatory view showing the structure of the heat exchanger for a freezer-refrigerator in example 2.

Detailed Description

In the heat exchanger for a refrigerator-freezer, a plate made of rectangular aluminum or aluminum alloy is used as the fin. Here, the rectangle generally means a quadrangle having 4 corners all of which are right angles, but the rectangle can be substantially recognized in all cases even when the angles of the corners are slightly deviated from the right angles, the vertices of the corners are slightly rounded, and the sides are slightly bent.

The fin is formed in a rectangular shape having a short side of 25mm or less in the X direction (length H) in the flow direction of the cooling target fluid. The shape of the fins is generally considered: the larger the surface area, the more improved the heat exchange performance. However, it is known that, in the heat exchanger for the freezer-refrigerator, if the size of the fluid to be cooled in the flow direction (X direction) is large to some extent, the effect of improving the heat exchange performance is hardly obtained. In particular, as demonstrated in example 1 described later, even if the short side length is reduced from the conventional 28mm to 20mm, no substantial decrease in heat exchange performance is observed. Therefore, it is understood that the length of at least 20mm to 28mm can be set as the upper limit of the length of the short side. Here, in order to substantially obtain the effect of downsizing the heat exchanger which is the original object, it is considered effective to reduce the short side length by 10% or more, that is, by 2.8mm or more (about 3mm), and from this viewpoint, the short side length is limited to 25mm or less in the present invention.

The lower limit of the short side length is about 20mm which exhibits the same performance as the conventional one. Although consideration needs to be given to both heat exchange performance and downsizing, the lower limit of the short side length can be allowed to be 18mm by considering at least various variations such as manufacturing variations. The short side length may be set to be preferably 19mm or more, and more preferably 20mm or more.

Further, the fin is shaped such that the shortest distance (distance L1) from the 4 corners of the rectangle to the outer peripheral surface of the metal pipe penetrating the fin is within the range of 12.0 to 17.5 mm. That is, by limiting the distance L1 between the metal pipe and the corner of the fin to the above-described predetermined range, the heat exchange performance in the freezer-refrigerator can be optimized. When the distance L1 is less than 12mm, sufficient heat exchange performance cannot be obtained, and when it exceeds 17.5mm, further improvement in heat exchange performance cannot be expected. This means that, in the case where the distance L1 exceeds 17.5mm, the shape of the fin is large beyond necessary limits.

Although 1 metal pipe may be provided, 2 or more metal pipes may be provided to penetrate 1 fin. When a plurality of metal pipes are provided, the refrigerant flow rate can be increased as compared with the case of 1 pipe, and improvement in heat exchange performance due to the increase can be expected. When a plurality of metal pipes are provided, the number of metal pipes is preferably 2 or 3. Although 4 or more are possible in principle, 3 or less are preferable from the viewpoint of downsizing.

In addition, when a plurality of metal pipes are provided, the metal pipes are preferably arranged in a direction parallel to the long sides of the rectangular shape of the fin, and the interval therebetween (pipe interval L2) is set to be in a range of 10 to 30 mm. When the pipe interval L2 is less than 10mm, the area of the fins between the metal pipes is too small to expect improvement in heat exchange performance, while when it exceeds 30mm, the fins are not provided with portions that sufficiently contribute to heat exchange, which is not preferable.

The area of the fin is preferably 480 to 750mm per one metal pipe²The range of (1). That is, it is preferable that the area of the fin be divided by the number of the metal pipes to obtain a value within the above range. By providing the above-described conditions of the short side length and the distance L1 in addition to the requirement of the area, the characteristics as a heat exchanger for a freezer-refrigerator can be improved. At least, the average fin area of each metal pipe is 480mm²As described above, sufficient heat exchange performance can be secured from the viewpoint of area, and on the other hand, the thickness exceeds 750mm²In the case of (2), further improvement of heat exchange performance cannot be expected.

As described above, the fin is made of aluminum or an aluminum alloy. More specifically, plates made of materials such as JIS a1050, JISA1100, JIS a1200, and JIS a7072 can be used.

The fin preferably has a thickness of 0.08 to 0.25 mm. When the thickness of the fin is less than 0.08mm, the heat radiation efficiency, that is, "fin efficiency" indicating the ratio of the amount of heat radiation to the actual amount of heat radiation when the entire heat radiation surface has the same temperature as the heat source may decrease, while when the thickness of the fin exceeds 0.25mm, the effect of improving the fin efficiency may saturate, and the entire weight may increase.

Preferably, the plurality of fin groups are arranged at intervals of 1 to 5 mm. If the fin group interval (dimension of reference symbol C in fig. 1 to 3) is less than 1mm, the leading edge effect may be reduced, while if it exceeds 5mm, the space between the fins may be wasted.

In the fin group, the arrangement pitch of the fins is preferably 2.2mm or more. Since frost is deposited on the surfaces of the fins when the heat exchanger for a freezer-refrigerator is used, it is difficult to secure a ventilation passage if the arrangement pitch of the fins is too narrow. Therefore, as described above, the arrangement pitch of the fins is preferably 2.2mm or more. On the other hand, if the fin pitch is too wide, the heat exchanger is increased in size, and therefore, it is preferable to set the fin pitch to 20mm or less. In the freezer-refrigerator heat exchanger, the frost grows faster toward the upstream side, and therefore, it is preferable to set the arrangement pitch of the fins in the fin group on the most upstream side to be the widest.

The metal piping is preferably an inner grooved pipe having an outer diameter of 5 to 10mm phi and a groove on an inner circumferential surface. When the outer diameter of the metal pipe is less than 5mm, the flow rate of the refrigerant flowing inside cannot be sufficiently secured, while when it exceeds 10mm, the fin area is decreased, which has the effect of decreasing the heat exchange performance. Further, by using the inner grooved tube as the metal pipe, the heat exchange performance between the refrigerant and the metal pipe can be improved, and the characteristics as a heat exchanger can be further improved.

The metal pipe is preferably made of copper or a copper alloy, or aluminum or an aluminum alloy. Examples of aluminum or aluminum alloys for metal pipes include JIS a1050, JIS a1100, JIS a1200, and JIS a 3003. Examples of copper or copper alloy for metal piping include JIS H3300C 1220 and JIS H3300C 5010.

Further, the refrigerant circulating in the metal pipe can be selected from R134a, R600a, and CO₂Is selected. Among these refrigerants, R600a is most commonly used and has a low environmental load, and therefore is suitable for use in a heat exchanger for a refrigerator-freezer. However, in view of cost, R134a which is less expensive may be used, and CO which is less likely to cause environmental load may be used₂And the like.

Further, it is preferable that the metal pipe has a straight portion penetrating the fin and a U-shaped coupling portion coupling the straight portions, and a pipe radius R in an outer diameter of the U-shaped coupling portion and a bending radius R outside the U-shape of the U-shaped coupling portion have a relationship of R/R ≧ 3. When R/R is less than 3, when the U-shaped coupling portion is formed by bending the metal pipe, there is a possibility that the metal pipe may be wrinkled, which may adversely affect the fluidity of the refrigerant.

[ examples ] A method for producing a compound

< embodiment example 1 >

A heat exchanger for a freezer-refrigerator according to an embodiment of the present invention will be described with reference to the drawings.

As shown in fig. 1, the heat exchanger 1 for a refrigerator-freezer of the present embodiment includes a plurality of fin groups 2, each of the fin groups 2 is composed of a plurality of fins 20 arranged in parallel at a predetermined interval from each other in a row, the plurality of fin groups 2 are arranged at a predetermined interval C in an X direction which is a flow direction of a cooling target fluid flowing in the refrigerator-freezer, and the heat exchanger 1 for a refrigerator-freezer includes 1 to a plurality of metal pipes 3 arranged in a meandering manner so as to sequentially penetrate the fins 20 in the fin groups 2.

As shown in fig. 2, the fin 20 is formed of a plate made of aluminum or aluminum alloy having a rectangular shape with a short side 21 having a length H of 25mm or less in the X direction. The shortest distance L1 from the 4 corners of the rectangle to the outer peripheral surface of the metal pipe penetrating the fin 20 is in the range of 12.0 to 17.5 mm. The following describes the details further.

(example 1)

As shown in fig. 1, 2, and 3 (a), the heat exchanger 1 for a refrigerator-freezer of the present example has plate fins made of a plate material having a material JIS a1050 and a thickness of 0.20mm as the fins 20. The fins 20 each have a rectangular shape with a short side 21 having a length H of 20mm and a long side 21 having a length W of 60 mm. Each fin 20 has 2 through holes 25, and the metal pipes 3 are inserted through the through holes 25.

The inner diameter d of the through hole 25 in the fin 20 is 8mm phi, which is a dimension corresponding to the outer diameter of the metal pipe 3. As shown in fig. 2, starting from the 4 corners 211 of the rectangle of the fin 20 and proceeding to the fin 20The shortest distances L1 to the outer peripheral surfaces of the metal pipes 3 penetrating therethrough were all the same size, 16.2 mm. The interval L2 between the adjacent 2 metal pipes 3 was set to 17 mm. In this example, an inner grooved tube made of JIS A3003, having an outer diameter of 8mm and a groove on the inner surface, was used as the metal pipe 3. In the metal pipe 3, the wall thickness of the groove bottom portion was 0.65mm, the groove depth was 0.65mm, and the number of grooves was 30. The area of the fin 20 is 550mm in the present example because the area occupied by the metal pipe 3 is excluded²。

In this example, the metal pipe 3 having a slightly smaller outer diameter is expanded in a state where the metal pipe 3 is inserted into the through hole 25 of the fin 20, and the fin 20 and the metal pipe 3 are joined to each other. The metal pipe 3 can be expanded by any of a mechanical pipe expanding method in which a mandrel, not shown, is pressed into the metal pipe 3 and moved, and a hydraulic pipe expanding method in which oil is filled into the metal pipe 3 and pressurized.

As shown in fig. 1 and 3 (a), the metal pipe 3 is arranged such that: after the fin group 2(g) on the most downstream side (the uppermost side in fig. 1 and 3 a) extending from the tip 31 (fig. 1) is penetrated, the fin group 2(a) on the most upstream side (the lowermost side in fig. 1 and 3 a) is penetrated by meandering through the plurality of U-shaped connecting portions 35 so as to sequentially penetrate the fin groups 2 on the upstream side, and further, after the fin group 2(a) is penetrated again through the U-shaped connecting portions 35, the fin group 2(g) on the most downstream side (the uppermost side in fig. 1 and 3 a) is penetrated by meandering through the plurality of U-shaped connecting portions 35 so as to sequentially penetrate the fin groups 2 on the downstream side and reach the tip 32. When the heat exchanger 1 for a refrigerator/freezer is used, a device required for a refrigerator such as a compressor, not shown, is connected to the end 31 and the end 32.

As shown in fig. 3 (a), the fin group 2 of this example has a specification of 7 layers of the fin groups 2(a) to 2 (g). The intervals C of the adjacent fin groups 2 are set to 3.0 mm. Therefore, the total dimension H2 in the X direction after the 7-layer fin groups 2 are arranged is 158 mm. The arrangement pitches P (fig. 1) of the fins 20 in each fin group 2 are set to be equal in size after the order of the most upstream fin group 2(a) (the lowermost fin group in fig. 3 (a)), the 2 nd fin group 2(b) from the upstream side, and the 3 rd fin group 2(c) from the upstream side in the flow direction of the cooling target fluid is smaller, but each arrangement pitch P is set to be 2.2mm or more.

Comparative example 1

As a comparative example of example 1, a heat exchanger 9 for a freezer-refrigerator having the configuration shown in fig. 3 (b) was prepared. For convenience of explanation, the same reference numerals are used for the same portions as those in embodiment 1. The heat exchanger 9 for a refrigerator/freezer of comparative example 1 differs from example 1 in the size of the fins 20, the positional relationship with the metal pipes 3, and the like.

That is, the fin 20 in comparative example 1 has a rectangular shape in which the length H of the short side 21 is 28mm and the length W of the long side 21 is 60 mm. The shortest distances L1 (fig. 2) from the 4 corners 211 of the rectangular fin 20 to the outer peripheral surface of the metal pipe 3 penetrating the fin 20 are all the same size, and are 18.4 mm. The area of the fins 20 is 790mm in this example². The fin group 2 was provided with 7 layers in the same manner as in example 1. The intervals C of the adjacent fin groups 2 are set to 2.0 mm. Therefore, the total dimension H2 in the X direction after the 7-layer fin groups 2 are arranged is 208 mm. The other constitution is the same as that of embodiment 1.

(example 2)

As a modification of example 1, a heat exchanger 102 for a freezer-refrigerator having the configuration shown in fig. 4 was prepared. For convenience of explanation, the same reference numerals are used for the same portions as those in example 1. The heat exchanger 102 for a refrigerator/freezer according to example 2 has 9 layers in addition to the number of the fin groups 2 as compared with example 1, and is provided to have an occupied volume equivalent to that of comparative example 1. Specifically, the intervals C between the adjacent fin groups 2 are set to 3.0 mm. Therefore, the total dimension H2 in the X direction after the fin groups 2 of 9 layers were aligned was 204 mm. The other constitution is the same as that of embodiment 1.

(Experimental example 1)

The heat exchangers of example 1, comparative example 1, and example 2 were incorporated into an actual refrigerating and freezing system, and experiments were conducted to evaluate the performance thereof. Specifically, a known refrigeration system is configured by connecting necessary components such as an expansion valve and a compressor to the respective heat exchangers, and the refrigeration performance is evaluated under predetermined conditions.

First, the lower surface of the lower fin group 2(b) in fig. 1 is an inlet of air as a cooling target medium in the heat exchanger, and the upper side in the same drawing is an outlet. Regarding the conditions of the air introduced into the inlet (air-side conditions), the dry bulb temperature was set to 5.0 ℃, the wet bulb temperature was set to 3.8 ℃, and the wind speed was set to 0.5 m/s.

Regarding the conditions of the refrigerant introduced into the inlet of the metal pipe 3 (refrigerant side conditions), the pressure at the inlet side of the expansion valve (not shown) was set to 1.826MPa, the temperature at the inlet side of the expansion valve was set to 25 ℃, the pressure at the outlet of the heat exchanger was set to 0.485MPa, and the temperature at the outlet of the heat exchanger was set to-8 ℃.

Then, air as a cooling target fluid and a refrigerant were circulated, and the air temperature at the inlet and the outlet of the heat exchanger and the temperature of the refrigerant at the inlet and the outlet of the heat exchanger were measured for about 150 minutes. Then, the heat exchange capacity (air-side capacity [ W ]) based on the air was calculated from the temperature difference between the air at the inlet and the air at the outlet of the heat exchanger. Further, the heat exchange capacity (refrigerant side capacity [ W ]) based on the refrigerant was calculated from the temperature difference between the refrigerant at the inlet and the refrigerant at the outlet of the heat exchanger. As the calculated values, both the average value and the instantaneous maximum value (instantaneous value) during the experiment were obtained. These results are shown in table 1. In table 1, evaluation values per unit volume are also calculated and shown based on the total dimension H2 in the X direction of each heat exchanger and the dimension of comparative example 1.

(Table 1)

As is apparent from table 1, the heat exchanger of example 1 has an improved air-side capacity and a substantially equivalent refrigerant-side capacity as compared with the heat exchanger of comparative example 1. On the other hand, the total size of example 1 was significantly smaller than that of comparative example 1. As a result of calculating the evaluation value per unit volume also taking this size difference into consideration, each evaluation value was 1.30 or more, that is, an improvement of 30% or more was exhibited with reference to comparative example 1 (1).

Further, as is apparent from table 1, the heat exchanger of example 2 has a result that both the air-side capacity and the refrigerant-side capacity are significantly improved as compared with the heat exchanger of comparative example 1. In addition, since the total size difference of example 1 is slightly different from that of comparative example 1, the results of the actual measurement values are similar to the evaluation per unit volume. As a result of calculating the evaluation value per unit volume in consideration of the size difference, each evaluation value was improved from the reference (1) of comparative example 1 as shown in table 1.

< embodiment example 2 >

As described above, in embodiment 1, it was found that the effect of improving the heat exchange performance as described above was obtained by changing the short side length H of the fin 20 from the conventional 28mm to 20 mm. Based on the results, a simulation was performed to find the allowable ranges of H and L1 by changing the short side length H (height) and the shortest distance from the corner of the fin to the outer peripheral surface of the metal pipe (distance L1) assuming that 2 refrigerant pipes were arranged to penetrate the rectangular fin at intervals of 17mm, with the long side dimension W (width) of the fin fixed to 60 mm. The number of fin groups was set to 7, and the other structure was the same as in example 1. When the outer diameter of the refrigerant pipe is set to be 5mm, the refrigerant pipe is spaced apart by 25mm in order to be disposed at a uniform distance.

Regarding the heat exchange performance in the evaluation items, the refrigerant tube temperature was set to 5 ℃, and the heat exchange capacity [ W ] was calculated from the temperature difference between the air temperature at the inlet and the air temperature at the outlet when air at a predetermined temperature was caused to flow in from the inlet, and used for the evaluation. Further, regarding the ratio, the measured value of the current heat exchanger was obtained, and the ratio was evaluated with the measured value of the current heat exchanger set to 1.

In addition, whether or not there is a molding failure is visually checked for the U-shaped connection portion, and if there is even a little wrinkling, "there is a failure condition (Δ)" is assumed, and if there is no wrinkling at all, "good (∘)" is assumed.

The results are shown in Table 2.

(Table 2)

As is clear from table 2, at least when the short side length H is 18mm or more and less than 28mm and the distance L1 is 12.0mm to 17.5mm, the heat exchange performance is equal to or more than that when H is 28mm and L1 is 18.4mm as the reference. At least, the average fin area per metal pipe was 480mm²～750mm²In the case of (3), the above-mentioned excellent characteristics can be maintained. Among them, it is also known that, in the case where the bending radius R/the tube radius R is less than 3, the copper tube is liable to wrinkle and the productivity may be deteriorated.

Claims

1. A heat exchanger for a refrigerator-freezer, comprising a plurality of fin groups each composed of a plurality of fins arranged in parallel at a predetermined interval in a row, wherein the plurality of fin groups are arranged at a predetermined interval in an X direction which is a flowing direction of a fluid to be cooled flowing in the refrigerator-freezer, and further comprising 1 or more metal pipes arranged in a serpentine shape so as to sequentially penetrate the fins in the fin groups,

the fin is formed of a plate made of aluminum or an aluminum alloy having a rectangular shape having a short side of a length of 25mm or less in the X direction,

the shortest distance from the 4 corners of the rectangle to the outer peripheral surface of the metal pipe penetrating the fin is within the range of 12.0-17.5 mm.

2. The heat exchanger for a refrigerator-freezer according to claim 1, wherein,

when the number of the metal pipes is plural, the metal pipes are arranged in a direction parallel to the long sides of the rectangles of the fins, and the interval between the metal pipes is in a range of 12 to 30 mm.

3. The heat exchanger for a freezer-refrigerator according to claim 1 or 2, wherein,

the area of the fin averaged per metal tubing is 480-750 mm²。

4. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 3, wherein,

the thickness of the fin is 0.08-0.25 mm.

5. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 4, wherein,

the plurality of fin groups are arranged at intervals of 1-5 mm.

6. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 5, wherein,

the arrangement pitch of the fins in the fin group is 2.2mm or more.

7. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 6, wherein,

the metal piping is an inner grooved pipe having an outer diameter phi of 5 to 10mm and a groove on an inner circumferential surface.

8. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 7, wherein,

the metal pipe is made of copper or a copper alloy, or aluminum or an aluminum alloy.

9. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 8, wherein,

in the aboveThe refrigerant circulating in the metal pipe is R134a, R600a and CO₂Any one of (1).

10. The heat exchanger for a freezer-refrigerator according to any one of claims 1 to 9, wherein,

the metal pipe has a straight line part penetrating the fin and a U-shaped connecting part connecting the straight line parts, and the pipe radius R in the outer diameter dimension of the U-shaped connecting part and the bending radius R of the U-shaped connecting part have a relation that R/R is more than or equal to 3.