JPWO2019176803A1 - Heat exchanger for refrigerator / freezer - Google Patents

Abstract

To provide a heat exchanger for a freezer / refrigerator that can achieve both heat exchange performance and frost formation time by arranging fins in the heat exchanger more efficiently. The fin group (2) has a plurality of stages, and the fin group (2) having a plurality of stages is arranged in the flow direction of the fluid to be cooled (arrow X direction) at a predetermined interval (C), and the fins in the fin group (2) are arranged. It has a metal pipe (3) arranged so as to sequentially penetrate (20) and exhibit a meandering form. The fin (20) is made of a plate made of aluminum or an aluminum alloy. The fin pitch (Pb) in the fin group 2 (a) located at the uppermost stream in the flow direction of the fluid to be cooled, the fin pitch (Pt) in the fin group (2 (g)) located at the most downstream, and the position between them. The fin pitch (Pm) in the fin group (2 (m)) is 10 mm ≦ Pb ≦ 20 mm, 1.8 mm ≦ Pt ≦ 5.0 mm, 2.2 ≦ Pm ≦ 15 mm, 2 ≦ Pb / Pt ≦ 11.2. It has a relationship of 1, 1 ≦ Pm / Pt ≦ 8.4.

Description

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

As the heat exchanger mounted on the refrigerator / freezer, a serpentine heat exchanger is usually used. The serpentine heat exchanger is composed of a plurality of plate fins arranged in a row in parallel at predetermined intervals from each other, and a metal pipe for passing one or a plurality of refrigerants penetrating these fins. .. Then, a group of fins composed of a plurality of fins arranged in a row is arranged in a plurality of stages, and the air in the refrigerator, which is a fluid to be cooled, flows in the arrangement direction of the fin groups so as to sequentially pass through the fin groups in the plurality of stages. Be placed.

In a refrigerator / freezer, it is required to reduce the size of the heat exchanger in order to maximize the internal volume for accommodating foods and the like while maintaining sufficient refrigerating / refrigerating performance. On the other hand, in the refrigerator / freezer, the temperature of the heat exchanger may be lower than 0 ° C., so that water vapor contained in the air adheres to the fins of the heat exchanger to form frost. In such a special usage environment, it has not yet been clarified what kind of configuration can be made smaller by improving the freezing / refrigerating performance, that is, the heat exchange performance.

For example, in Patent Document 1, by cutting off a surface on the air inlet side and / or a part of the heat exchange fins on the upper surface of the refrigerant inlet, the distance between the heat exchange fins on that surface is widened and frost blockage is suppressed. , The interval of defrosting operation is extended to suppress the temperature rise in the space. However, in the heat exchanger for a freezer / refrigerator in which frost is unavoidably attached as described above, the configuration of Patent Document 1 cannot sufficiently obtain the effect.

Japanese Unexamined Patent Publication No. 2010-210140

The present invention has been made in view of this background, and provides a heat exchanger for a freezer / refrigerator capable of achieving both heat exchange performance and frost formation time by arranging fins in the heat exchanger more efficiently. It is something to try.

One aspect of the present invention has a plurality of stages of fin groups composed of a plurality of fins arranged in a row in parallel with each other at predetermined intervals, and the plurality of stages of fin groups are circulated in a refrigerator / freezer. In a heat exchanger for a refrigerator / freezer having one or a plurality of metal pipes arranged so as to form a meandering shape by sequentially penetrating the fins in the fin group at predetermined intervals in the flow direction of the above.
The fins are made of aluminum or an aluminum alloy plate.
The fin pitch Pb in the fin group located at the most upstream in the flow direction of the fluid to be cooled, the fin pitch Pt in the fin group located at the most downstream, and the fin pitch Pm in the fin group located between them are
10 mm ≤ Pb ≤ 20 mm,
1.8 mm ≤ Pt ≤ 5.0 mm,
2.2 ≤ Pm ≤ 15 mm,
2 ≦ Pb / Pt ≦ 11.2,
1 ≦ Pm / Pt ≦ 8.4
It is in a heat exchanger for a freezer / refrigerator, which is characterized by having the above relationship.

As described above, the heat exchanger for the refrigerator / freezer changes the fin pitch from the inlet side to the outlet side of the fluid to be cooled flowing in the refrigerator / freezer so as to narrow the fin pitch, while adjusting the specific dimensions thereof. Limited to a specific range. As a result, the frost formation time can be relatively long while maintaining the heat exchange performance, and both the heat exchange performance and the frost formation time can be realized.

The explanatory view which shows the structure of the heat exchanger for a refrigerator / freezer in Embodiment 1. FIG.

As the fin, as described above, a plate made of aluminum or an aluminum alloy is used. More specifically, plates made of materials such as JIS A1050, JIS A1100, JIS A1200, and JIS A7072 can be used.

Further, the thickness of the fin is preferably 0.08 to 0.25 mm. When the thickness of the fin is less than 0.08 mm, the heat dissipation efficiency, that is, the "fin efficiency" which represents the ratio between the heat dissipation amount and the actual heat dissipation amount when the entire heat dissipation surface is at the same temperature as the heat source is lowered. On the other hand, if the fin thickness exceeds 0.25 mm, the effect of improving the fin efficiency may be saturated and the total weight may be increased.

Further, the arrangement pitch of the fins in the fin group is wide on the entry side of the fluid to be cooled (air) and narrows toward the exit side. That is, the fin pitch Pb in the fin group located at the uppermost stream in the flow direction of the fluid to be cooled, the fin pitch Pt in the fin group located at the most downstream, and the fin pitch Pm in the fin group located between them are Set so that the range is 10 mm ≦ Pb ≦ 20 mm, 1.8 mm ≦ Pt ≦ 11.2, 2.2 ≦ Pm ≦ 15 mm.

If the fin pitch Pb on the side where the fluid to be cooled (upstream side) is less than 10 mm, the blockage due to frost is quick and the ventilation resistance becomes high at an early stage. Further, when the fin pitch Pb is wider than 20 mm, the number of fins is reduced, which has an influence on the heat exchange performance.

Since the fin pitch Pm of the second and subsequent stages from the inlet side (upper stream side) of the fluid to be cooled is slightly lower in both temperature and humidity, the fin pitch is narrower than that of the inlet side (upper stream side) and the number of fins is reduced. It is necessary to improve the heat exchange performance by increasing the number. Therefore, the fin pitch Pm is set to 15 mm or less. On the other hand, when the air flow between the fins is taken into consideration, if the fin pitch Pm is less than 2.2 mm, improvement in heat exchange performance cannot be expected and ventilation resistance increases. Therefore, the fin pitch is set to 2.2 mm or more.

Since air with the lowest temperature and humidity flows on the side where the fluid to be cooled (the most downstream side) flows, it is necessary to increase the number of fins as much as possible. Therefore, the fin pitch Pt on the side where the fluid to be cooled (the most downstream side) is discharged is set to 5 mm or less. On the other hand, if it is made too narrow, there is a problem that frost adheres at an early stage and it becomes difficult to secure a ventilation path. Therefore, the fin pitch Pt is set to 1.8 mm or more, more preferably 2.2 mm or more. Good.

Further, the fin pitch Pb, the fin pitch Pt, and the fin pitch Pm satisfy the relationship of 2 ≦ Pb / Pt ≦ 11.2 and 1 ≦ Pm / Pt ≦ 8.4. If Pb / Pt is less than 2, Pm is in the middle, so the effect of changing the fin pitch ratio may not be fully exerted. If Pb / Pt exceeds 11.2, it may not be fully exhibited. Insufficient cooling of the air on the entry side may cause a problem that frost adheres early after the middle stage. Therefore, more preferably, Pb / Pt is 5 or less. On the other hand, if Pm / Pt is less than 1, frost may adhere to the intermediate portion at an early stage to increase the ventilation resistance, resulting in a shortage of heat exchange area on the air outlet side and a decrease in heat exchange performance. If Pm / Pt exceeds 8.4, the air is not sufficiently cooled in the intermediate portion, and there is a possibility that frost may be attached to the fins on the air outlet side at an early stage. Therefore, more preferably, Pm / Pt is 6.8 or less.

The relationship between the fin pitch Pb and the fin pitch Pm is not particularly limited, but is 0.3 ≦ Pb / Pm ≦ 20, preferably 0.7 ≦ Pb / Pm ≦ 9.1, and more preferably. 1 <Pb / Pm ≦ 9.1. By adjusting to these relationships, it is possible to more reliably achieve the effects of heat exchange performance and frost formation time. If it deviates from these ranges, adjacent fins may come into contact with each other and block the passage of the refrigerant, so that frost may easily form or the heat exchange performance may deteriorate.

Further, the metal pipe is preferably made of copper or a copper alloy, or aluminum or an aluminum alloy. Examples of aluminum or aluminum alloy for metal piping include JIS A1050, JIS A1100, JIS A1200, and JIS A3003. Further, examples of copper or copper alloy for metal piping include JIS H3300 C1220 and JIS H3300 C5010.

Further, the refrigerant circulating in the metal pipe can be selected from any of _{R134a, R600a, and CO 2.} Among these refrigerants, R600a is the most common and has a low environmental load, and is therefore suitable for use in heat exchangers for refrigerators and freezers. However, from the viewpoint of cost, cheaper R134a may be used, or CO2 or the like having a low environmental load can be used.

<Embodiment 1>
The heat exchanger 1 for a refrigerator / freezer according to the embodiment of the present application will be described with reference to FIG. As shown in the figure, the heat exchanger 1 for a refrigerator / freezer has a plurality of stages of fin groups 2 composed of a plurality of fins 20 arranged in a row in parallel at predetermined intervals from each other, and the fin group of the plurality of stages. 2 and the fluid to be cooled flowing in the refrigerator / freezer are arranged at a predetermined interval C in the flow direction (direction of arrow X), and are arranged so as to sequentially penetrate the fins 20 in the fin group 2 and exhibit a meandering form. It has one or a plurality of metal pipes 3.

The fin 20 is made of a rectangular aluminum or aluminum alloy plate. Then, the fin pitch Pb in the fin group 2 (a) located at the most upstream in the flow direction (arrow X direction) of the fluid to be cooled (air), the fin pitch Pt in the fin group 2 (g) located at the most downstream, and the like. The fin pitch Pm in the fin group 2 (m) located between the two is 10 mm ≦ Pb ≦ 20 mm, 1.8 ≦ Pt ≦ 5.0 mm, 2.2 ≦ Pm ≦ 15 mm, 2 ≦ Pb / Pt ≦ 11.2. It has a relationship of 1, 1 ≦ Pm / Pt ≦ 8.4. The details will be described below.

(Example 1)
The heat exchanger 1 for a refrigerator / freezer according to the first embodiment has plate fins made of a material JIS A1050 and a plate material having a thickness of 0.20 mm as fins 20. Each of the fins 20 has a rectangular shape having a short side 21 having a length H of 20 mm and a long side 21 having a length W of 60 mm. Each fin 20 has two through holes 25, and the metal pipe 3 is inserted into each of the through holes 25.

The inner diameter d of the through hole 25 in the fin 20 is 8 mmφ, which is a dimension corresponding to the outer diameter of the metal pipe 3. As the metal pipe 3, in this example, an inner grooved pipe having a material of JIS A3003, an outer diameter of 8 mm, and a groove on the inner peripheral surface was used. The metal pipe 3 has a groove bottom portion with a wall thickness of 0.65 mm, a groove depth of 0.65 mm, and a groove number of 30.

In this example, the fin 20 and the metal pipe 3 are joined by expanding the metal pipe 3 with the metal pipe 3 having a slightly smaller outer diameter inserted into the through hole 25 of the fin 20. For the expansion of the metal pipe 3, either a mechanical pipe expansion method in which a mandrel (not shown) is press-fitted into the metal pipe 3 to move the mandrel or a hydraulic pipe expansion method in which the metal pipe 3 is filled with oil and pressurized is adopted. It can be carried out by doing.

As shown in FIG. 1, the metal pipe 3 extends from the end 31 (FIG. 1), penetrates the fin group 2 (g) on the most downstream side (the uppermost side in FIG. 1), and then has a plurality of U-shaped connecting portions 35. It meanders through the fin group 2 of a plurality of stages on the upstream side sequentially through the fin group 2 (a) on the most upstream side (lowermost side in FIG. 1), and further, a U-shaped connecting portion 35. After penetrating the fin group 2 (a) again through the fin group 2, it meanders through the plurality of U-shaped connecting portions 35 so as to sequentially penetrate the fin group 2 in a plurality of stages on the downstream side, and is the most downstream side (in FIG. 1). It is arranged so as to penetrate the fin group 2 (g) on the uppermost side) and reach the terminal 32. When the heat exchanger 1 for a refrigerator / freezer is used, a compressor (not shown) or other equipment necessary for the refrigerator is connected to the terminal 31 and the terminal 32.

The fin group 2 of this example has a 7-stage specification of fin groups 2 (a) to 2 (g). The distance C between the adjacent fin groups 2 was set to 3.0 mm. The fin pitch, which is the arrangement pitch of the fins 20 in the 7-stage fin group 2, is the widest, with the fin pitch Pb of the most upstream fin group 2 (a) being 10.0 mm, and that of the most downstream fin group 2 (g). The fin pitch Pt was the narrowest at 2.2 mm, and the fin pitch Pm of all the fin groups 2 (m) between them was set to 4.0 mm.

(Comparative Examples 1 and 2)
Comparative Example 1 is an example in which the basic configuration is the same as that of the first embodiment, and the fin pitches Pb, Pt, and Pm of all the fin groups 2 from the most upstream to the most downstream are aligned to 2.2 mm. Comparative Example 2 is an example in which the basic configuration is the same as that of the first embodiment, and the fin pitches Pb, Pt, and Pm of all the fin groups 2 from the most upstream to the most downstream are aligned to 10.0 mm.

(Evaluation test)
An experiment was conducted in which the heat exchangers of Example 1, Comparative Example 1 and Example 2 described above were incorporated into an actual freezing and refrigerating system and their performance was evaluated. Specifically, a known refrigeration system was constructed by connecting an expansion valve, a compressor and other necessary parts to each heat exchanger, and the refrigeration performance was evaluated under predetermined conditions.

First, the lower surface of the lower fin group 2 (a) in FIG. 1 is an inlet for air, which is a medium to be cooled in the heat exchanger, and the upper surface in the figure is an outlet. As for the conditions of the air introduced into the inlet (air side conditions), the dry-bulb temperature was 5.0 ° C, the wet-bulb temperature was 3.8 ° C, and the wind speed was 0.5 m / s.

Regarding the conditions of the refrigerant to be introduced into the inlet of the metal pipe 3 (refrigerant side conditions), the pressure on the inlet side of the expansion valve (not shown) is 1.826 MPa, the temperature on the inlet side of the expansion valve is 25 ° C., and the heat exchanger The pressure at the outlet was 0.485 MPa, and the temperature at the outlet of the heat exchanger was −8 ° C.

Then, the air and the refrigerant, which are the fluids to be cooled, were circulated, and the air temperature at the inlet and outlet of the heat exchanger and the temperature of the refrigerant at the inlet and 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 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 refrigerants at the inlet and outlet of the heat exchanger. Moreover, as the calculated value, both the average value during the experimental period and the instantaneous maximum value (instantaneous value) were obtained.

In addition, the differential pressure between the air inlet and outlet of the heat exchanger (fin group) was measured with a micro differential pressure gauge, and the value was used as the ventilation resistance (pressure loss). Then, the frost formation time was evaluated by the time from the start of the evaluation until the ventilation resistance (pressure loss) reached 150 Pa.

Regarding the obtained maximum heat exchange capacity, average heat exchange capacity, and frost formation time, the result of Example 1 was set to 1, and Comparative Example 1 and Comparative Example 2 were evaluated by the ratio to the result. The evaluation results are shown in Table 1.

As shown in Table 1, although the maximum heat exchange capacity and the average heat exchange capacity of Example 1 were inferior to those of Comparative Example 1, the frost formation time could be extended more than three times. Further, in Example 1, although the frost formation time was inferior to that in Comparative Example 2, the maximum heat exchange capacity and the average heat exchange capacity were significantly improved. From these results, it can be said that Example 1 can achieve both heat exchange performance and frost formation time as compared with Comparative Examples 1 and 2.

<Embodiment 2>
Based on the configuration shown in FIG. 1 in the first embodiment (the configuration of the first embodiment), as shown in Table 2, in a plurality of types of heat exchangers having different configurations in which the fin pitches Pb, Pt, and Pm are changed, an example of the embodiment. The allowable range of the fin pitch combination was evaluated under the same conditions as in the evaluation test of 1.

The outlet temperature of the air, which is the medium to be cooled, was evaluated as appropriate when it was -5.2 ° C or lower, and as insufficient cooling performance when it exceeded it.

The pressure loss (Pa) is measured by measuring the differential pressure (pressure loss) between the air inlet and outlet of the heat exchanger (fin group) in the ventilation flow path with a micro differential pressure gauge, and the pressure loss 1 hour after the start of ventilation is measured. Examined. When the pressure loss was 10 Pa or less, it was evaluated as appropriate, and when it exceeded that, it was evaluated as high pressure loss.

Regarding the frost formation performance, the pressure loss 48 hours after the start of ventilation is measured in the same manner as above, and if the pressure loss at that time is 10 Pa or less, the frost formation performance is qualified, and the pressure loss exceeds 10 Pa due to frost on the fins. The case was evaluated as unsuitable for frost formation performance. The evaluation results are shown in Table 2.

As can be seen from Table 2, the fin pitches Pb, Pt and Pm are 10 mm ≦ Pb ≦ 20 mm, 1.8 mm ≦ Pt ≦ 5.0 mm, 2.2 ≦ Pm ≦ 15 mm, 2 ≦ Pb / Pt ≦ 11.2, Regarding the configurations E1, E4, E9 to E11, E13, and E14 having all the relationships of 1 ≦ Pm / Pt ≦ 8.4, all the evaluation items were appropriate or passed. Among them, the configurations E1 and E4 having a relationship of Pt ≧ 2.2 mm and Pb / Pt ≦ 5 and Pm / Pt ≦ 6.8 have particularly small pressure loss and exhibit excellent well-balanced characteristics. You can see that.

On the other hand, in the configurations C2 and C3, the fin pitch Pb in the uppermost stream was too narrow, the range of Pb / Pt also deviated from the appropriate range, and the frost formation was rejected.

In the configuration C5, the fin pitch Pb in the uppermost stream was too wide, and the cooling performance was insufficient.

In the configuration C6, the fin pitch Pm at the intermediate position was too narrow, the Pm / Pt range also deviated from the appropriate range, and the pressure loss became too high.

In the configuration C7, the fin pitch Pm at the intermediate position was too wide, resulting in insufficient cooling performance.

In the configuration C8, the fin pitch Pt at the most downstream was too narrow, the Pb / Pt range and the Pm / Pt range were out of the appropriate range, resulting in an excessively high pressure loss.

In the configuration C12, the fin pitch Pt at the most downstream was too wide, resulting in insufficient cooling performance.

Claims (7)

It has a plurality of stages of fin groups consisting of a plurality of fins arranged in a row in parallel with each other at a predetermined interval, and the plurality of stages of fin groups are arranged at a predetermined interval in the flow direction of the fluid to be cooled flowing in the refrigerator / freezer. In a heat exchanger for a refrigerator / freezer having one or a plurality of metal pipes arranged apart from each other and sequentially penetrating the fins in the fin group to exhibit a meandering shape.
The fins are made of aluminum or an aluminum alloy plate.
The fin pitch Pb in the fin group located at the most upstream in the flow direction of the fluid to be cooled, the fin pitch Pt in the fin group located at the most downstream, and the fin pitch Pm in the fin group located between them are
10 mm ≤ Pb ≤ 20 mm,
1.8 mm ≤ Pt ≤ 5.0 mm,
2.2 ≤ Pm ≤ 15 mm,
2 ≦ Pb / Pt ≦ 11.2,
1 ≦ Pm / Pt ≦ 8.4
Heat exchanger for refrigerators and freezers. The fin pitches Pb, Pt and Pm are
2.2 mm ≤ Pt ≤ 5.0 mm,
2 ≦ Pb / Pt ≦ 5,
1 ≦ Pm / Pt ≦ 6.8
The heat exchanger for a refrigerator / freezer according to claim 1, which has the above-mentioned relationship. The heat exchanger for a refrigerator / freezer according to claim 1 or 2, wherein the metal pipe is a pipe with an inner groove having an outer diameter of φ5 to 10 mm. The heat exchanger for a refrigerator / freezer according to any one of claims 1 to 3, wherein the metal pipe is made of copper or a copper alloy, or aluminum or an aluminum alloy. The heat exchanger for a refrigerator / freezer according to any one of claims 1 to 4, wherein a plurality of the metal pipes penetrate the one fin. The heat exchanger for a refrigerator / freezer according to any one of claims 1 to 5, wherein the refrigerant circulating in the metal pipe is _{any of R134a, R600a, and CO 2.} The heat exchanger for a refrigerator / freezer according to any one of claims 1 to 6, wherein the metal pipe and the fin are assembled by mechanical pipe expansion or hydraulic pipe expansion.

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