Heat exchangers for refrigerators and freezers

Abstract

Provided is a heat exchanger for a refrigerator / freezer that achieves both heat exchange performance and frost formation time by more efficiently arranging fins within the heat exchanger. The heat exchanger has multiple fin groups (2), the multiple fin groups (2) are arranged at predetermined intervals (C) in the flow direction of a fluid to be cooled (direction indicated by arrow X), and metal piping (3) is arranged to sequentially penetrate the fins (20) of the fin groups (2) in a serpentine shape. The fins (20) are made of aluminum or aluminum alloy plates. The fin pitch (Pb) of the fin group (2(a)) located at the most upstream position in the flow direction of the fluid to be cooled, the fin pitch (Pt) of the fin group (2(g)) located at the most downstream position, and the fin pitch (Pm) of the fin group (2(m)) located between them satisfy the following relationships: 10 mm ≦ Pb ≦ 20 mm, 1.8 mm ≦ Pt ≦ 5.0 mm, 2.2 ≦ Pm ≦ 15 mm, 2 ≦ Pb / Pt ≦ 11.2, and 1 ≦ Pm / Pt ≦ 8.4.

Description

[Technical field]

[0001] The present invention relates to a heat exchanger for a refrigerator. [Background technology]

[0002] Serpentine heat exchangers are usually used as heat exchangers installed in refrigerators and freezers. Serpentine heat exchangers are composed of a number of plate fins arranged in a row in parallel with each other at a certain interval, and one or more metal pipes that pass through the fins and allow the refrigerant to flow. Fin groups each consisting of a number of fins arranged in a row are arranged in multiple stages, and the air in the refrigerator, which is the fluid to be cooled, flows in the direction of the arrangement of the fin groups and passes through the multiple stages of fin groups in sequence.

[0003] In a refrigerator-freezer, the heat exchanger needs to be made smaller in size in order to maximize the internal volume for storing food and the like while maintaining sufficient refrigeration and freezing performance. Meanwhile, in a refrigerator-freezer, the temperature of the heat exchanger may drop below 0 degrees, causing water vapor in the air to adhere to the fins of the heat exchanger and form frost. In such a special usage environment, it has not yet been clarified what kind of configuration can improve refrigeration and freezing performance, i.e., heat exchange performance, while making the refrigerator smaller.

[0004] For example, in Patent Document 1, by cutting out some of the heat exchange fins on the surface on the air inlet side and / or the upper side surface of the refrigerant inlet, the interval between the heat exchange fins on that surface is increased, thereby suppressing frost blockage, extending the interval between defrosting operations, and suppressing the temperature rise in the space. However, in a heat exchanger for a refrigerator / freezer, where the adhesion of frost is unavoidable as described above, the configuration of Patent Document 1 is not sufficiently effective. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2010-210140 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above background, and aims to provide a heat exchanger for a refrigerator / freezer that can achieve both high heat exchange performance and reduced frost formation time by more efficiently arranging fins inside the heat exchanger. [Means for solving the problem]

[0007] One aspect of the present invention is a heat exchanger for a refrigerator / freezer, the heat exchanger having multiple stages of fin groups each made of a plurality of fins arranged in a row in parallel with each other at a predetermined interval, the multiple stages of fin groups being arranged at predetermined intervals in a flow direction of a cooled fluid flowing through the refrigerator / freezer, and one or more metal pipes being arranged to sequentially penetrate the fins in the fin groups and form a serpentine shape, The fin is made of an aluminum or aluminum alloy plate, the multiple stages of fin groups include an upstream fin group consisting of only one stage of fin groups located at the most upstream side in the flow direction of the cooled fluid, a downstream fin group consisting of only one stage of fin groups located at the most downstream side, and an intermediate fin group consisting of multiple stages of fin groups located between them, The fin pitch Pb in the upstream fin group, the fin pitch Pt in the downstream fin group, and the fin pitch Pm in the intermediate fin group are 10mm≦Pb≦20mm, 1.8mm≦Pt≦5.0mm, 10mm≦Pm≦15mm, 4.0≦Pb / Pt≦11.1, 3.0≦Pm / Pt≦8.3 、 1 <Pb / Pm≦9.1 The present invention relates to a heat exchanger for a refrigerator / freezer, which has the above relationship. Effect of the Invention

[0008] As described above, in the above-mentioned heat exchanger for a refrigerator, the fin pitch is changed so as to become narrower from the inlet side to the outlet side of the cooled fluid flowing through the refrigerator, while the specific dimensions are limited to the above-mentioned specific range. This makes it possible to relatively extend the frost formation time while maintaining the heat exchange performance, thereby realizing a balance between the heat exchange performance and the frost formation time. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is an explanatory diagram showing the configuration of a heat exchanger for a refrigerator according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] As described above, the fins are made of aluminum or aluminum alloy plates. More specifically, plates made of materials such as JIS A1050, JIS A1100, JIS A1200, and JIS A7072 can be used.

[0011] The fins preferably have a thickness of 0.08 to 0.25 mm. If the fin thickness is less than 0.08 mm, the heat dissipation efficiency, i.e., the "fin efficiency" which represents the ratio of the amount of heat dissipated when the entire heat dissipation surface is at the same temperature as the heat source to the actual amount of heat dissipation, may decrease, whereas if the fin thickness exceeds 0.25 mm, the improvement effect of the fin efficiency may saturate and the overall weight may increase.

[0012] The arrangement pitch of the fins in the fin group is wider on the inlet side of the cooled fluid (air) and narrower toward the outlet side. In other words, the fin pitch Pb of the fin group located at the most upstream position in the flow direction of the cooled fluid, the fin pitch Pt of the fin group located at the most downstream position, and the fin pitch Pm of the fin groups located between them are set to be in the ranges of 10 mm≦Pb≦20 mm, 1.8 mm≦Pt≦11.2, and 2.2≦Pm≦15 mm.

[0013] If the fin pitch Pb on the inlet side (upstream side) of the cooled fluid is less than 10 mm, frost will cause clogging and ventilation resistance will increase early. Also, if the fin pitch Pb is wider than 20 mm, the number of fins will be reduced, which will affect the heat exchange performance.

[0014] The fin pitch Pm from the second stage onwards from the inlet side (upstream side) of the cooled fluid is somewhat lower in both temperature and humidity, so it is necessary to improve heat exchange performance by narrowing the fin pitch compared to the inlet side (upstream side) and increasing the number of fins. Therefore, the fin pitch Pm is set to 15mm or less. On the other hand, when considering the air flow between the fins, if the fin pitch Pm is less than 2.2mm, improvement in heat exchange performance cannot be expected and ventilation resistance will increase, so it is set to 2.2mm or more.

[0015] Since the air with the lowest temperature and humidity flows on the outlet side of the cooled fluid (the most downstream side), it is necessary to increase the number of fins as much as possible. Therefore, the fin pitch Pt on the outlet side of the cooled fluid (the most downstream side) is set to 5 mm or less. On the other hand, if it is made too narrow, frost will form early and it will be difficult to ensure a ventilation path, so the fin pitch Pt should be 1.8 mm or more, and more preferably 2.2 mm or more.

[0016] Furthermore, the fin pitch Pb, the fin pitch Pt, and the fin pitch Pm are set to satisfy the relationships of 2 ≤ Pb / Pt ≤ 11.2 and 1 ≤ Pm / Pt ≤ 8.4. When Pb / Pt is less than 2, since Pm will be in the middle, there is a risk that the effect of changing the fin pitch ratio cannot be fully exerted. When Pb / Pt exceeds 11.2, the cooling of air on the inlet side becomes insufficient, and there is a risk of a problem that frost adheres early in the middle stage and after. Therefore, more preferably, Pb / Pt is 5 or less. On the other hand, when Pm / Pt is less than 1, there is a risk of a problem that frost adheres early in the middle part, increasing the ventilation resistance, and the heat exchange area on the air outlet side is insufficient, resulting in a decrease in heat exchange performance. When Pm / Pt exceeds 8.4, the cooling of air in the middle part becomes insufficient, and there is a risk of a problem that frost adheres early to the fins on the air outlet side. Therefore, more preferably, Pm / Pt is 6.8 or less.

[0017] Also, the relationship between the fin pitch Pb and the fin pitch Pm is 、1 <Pb / Pm ≤ 9.1. By adjusting to these relationships, it is possible to more surely achieve the effects of heat exchange performance and frosting time. If these ranges are deviated from, adjacent fins may come into contact with each other, blocking the refrigerant passage, making it easier to frost, or the heat exchange performance may deteriorate.

[0018] Also, the metal pipe is preferably made of copper or a copper alloy, or aluminum or an aluminum alloy. Examples of the aluminum or aluminum alloy for the metal pipe include JIS A1050, JIS A1100, JIS A1200, and JIS A3003. Examples of the copper or copper alloy for the metal pipe include JIS H3300 C1220 and JIS H3300 C5010.

[0019] The refrigerant circulated in the metal pipe can be selected from R134a, R600a, and CO2. Among these refrigerants, R600a is the most common and has a low environmental impact, making it suitable for use in heat exchangers for refrigerators and freezers. However, from a cost perspective, cheaper R134a may be used, and CO2, which has a low environmental impact, may also be used. EXAMPLES

[0020] <Embodiment 1> The present application EMBODIMENT 1 Such a heat exchanger 1 for a freezer-refrigerator will be described with reference to Fig. 1. As shown in the figure, the heat exchanger 1 for a freezer-refrigerator has multiple stages of fin groups 2 each consisting of multiple fins 20 arranged in a row in parallel with each other at a predetermined interval, and has one or more metal pipes 3 arranged at a predetermined interval C between the multiple stages of fin groups 2 and in the flow direction (direction of arrow X) of the fluid to be cooled flowing through the freezer-refrigerator, and passing through the fins 20 in the fin groups 2 in sequence to form a serpentine shape.

[0021] The fins 20 are rectangular plates made of aluminum or aluminum alloy. The fin pitch Pb of the fin group 2(a) located at the most upstream position in the flow direction (arrow X direction) of the cooled fluid (air), the fin pitch Pt of the fin group 2(g) located at the most downstream position, and the fin pitch Pm of the fin group 2(m) located therebetween satisfy the following relationships: 10mm≦Pb≦20mm, 1.8≦Pt≦5.0mm, 2.2≦Pm≦15mm, 2≦Pb / Pt≦11.2, 1≦Pm / Pt≦8.4. This will be described in more detail below.

[0022] ( Reference example 1) Reference exampleThe heat exchanger 1 for a refrigerator-freezer has plate fins made of a plate material of JIS A1050 and a thickness of 0.20 mm as the fins 20. Each of the fins 20 has a rectangular shape with a short side 21 having a length H of 20 mm and a long side 21 having a length W of 60 mm. Each of the fins 20 has two through holes 25, and the metal pipes 3 are inserted into the through holes 25.

[0023] The inner diameter d of the through hole 25 in the fin 20 is 8 mmφ, which is a dimension equivalent to the outer diameter of the metal pipe 3. In this example, an inner grooved pipe made of JIS A3003 material, having an outer diameter φ of 8 mm, and having grooves on the inner peripheral surface was used as the metal pipe 3. The metal pipe 3 has a wall thickness of 0.65 mm at the groove bottom, a groove depth of 0.65 mm, and 30 grooves.

[0024] In this example, the fin 20 and the metal pipe 3 are joined by expanding the metal pipe 3 with a slightly smaller outer diameter inserted into the through hole 25 of the fin 20. The metal pipe 3 can be expanded by adopting either a mechanical expansion method in which a mandrel (not shown) is pressed into the metal pipe 3 and moved, or a hydraulic expansion method in which oil is filled into the metal pipe 3 to apply pressure.

[0025] As shown in Fig. 1, the metal pipe 3 is arranged so that it extends from the end 31 (Fig. 1), penetrates the fin group 2(g) on ​​the most downstream side (the uppermost side in Fig. 1), then meanders to penetrate the multiple stages of the fin groups 2 on the upstream side through multiple U-shaped connectors 35, penetrates the fin group 2(a) on the most upstream side (the lowermost side in Fig. 1), further penetrates the fin group 2(a) again through the U-shaped connector 35, then meanders to penetrate the multiple stages of the fin groups 2 on the downstream side through multiple U-shaped connectors 35, penetrates the fin group 2(g) on ​​the most downstream side (the uppermost side in Fig. 1) and reaches the end 32. When the heat exchanger 1 for a freezer-refrigerator is used, a compressor (not shown) and other devices necessary for the freezer are connected to the end 31 and the end 32.

[0026] The fin group 2 in this example has seven stages, consisting of fin groups 2(a) to 2(g). The interval C between adjacent fin groups 2 is 3.0 mm. The fin pitch, which is the arrangement pitch of the fins 20 in the seven stages of the fin group 2, is such that the fin pitch Pb of the most upstream fin group 2(a) is the widest at 10.0 mm, the fin pitch Pt of the most downstream fin group 2(g) is the narrowest at 2.2 mm, and the fin pitch Pm of all fin groups 2(m) between them is 4.0 mm.

[0027] (Comparative Examples 1 and 2) Comparative Example 1 has the following basic structure: Reference example Comparative Example 2 is an example in which the fin pitches Pb, Pt, and Pm of all the fin groups 2 from the most upstream to the most downstream are set to 2.2 mm, similar to Comparative Example 1. Reference example 1, the fin pitches Pb, Pt, Pm of all the fin groups 2 from the most upstream to the most downstream are all set to 10.0 mm.

[0028] (Evaluation test) As mentioned above Reference example 1, Comparative Example 1 and Comparative Example The heat exchanger No. 2 was incorporated into an actual refrigeration and storage system, and an experiment was conducted to evaluate its performance. Specifically, a publicly 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 specified conditions.

[0029] First, the lower surface of the lower fin group 2(a) in Fig. 1 is the inlet for the air, which is the medium to be cooled in the heat exchanger, and the upper side in the same figure is the outlet. The conditions of the air introduced into the inlet (air side conditions) are as follows: dry bulb temperature 5.0°C, wet bulb temperature 3.8°C, and wind speed 0.5m / s.

[0030] In addition, the conditions of the refrigerant introduced into the inlet of the metal pipe 3 (refrigerant side conditions) were as follows: the pressure on the inlet side of the expansion valve (not shown) was 1.826 MPa, the temperature on the inlet side of the expansion valve was 25°C, the pressure at the outlet of the heat exchanger was 0.485 MPa, and the temperature at the outlet of the heat exchanger was -8°C.

[0031] Then, the air, which is the fluid to be cooled, and the refrigerant were circulated, and the air temperature at the inlet and outlet of the heat exchanger and the refrigerant temperature at the inlet and outlet of the heat exchanger were measured for about 150 minutes. The air-based heat exchange capacity (air-side capacity [W]) was calculated from the temperature difference of the air at the inlet and outlet of the heat exchanger. The refrigerant-based heat exchange capacity (refrigerant-side capacity [W]) was also calculated from the temperature difference of the refrigerant at the inlet and outlet of the heat exchanger. The calculated values ​​were both the average value during the experiment period and the momentary maximum value (instantaneous value).

[0032] In addition, the differential pressure between the air inlet and outlet of the heat exchanger (fin group) was measured using a micro-differential pressure gauge, and the value was taken as the ventilation resistance (pressure loss). The frost formation time was evaluated as the time from the start of the evaluation until the ventilation resistance (pressure loss) reached 150 Pa.

[0033] The maximum heat exchange capacity, average heat exchange capacity, and frost formation time obtained are as follows: Reference example The result of 1 was set as 1, and Comparative Examples 1 and 2 were evaluated based on the ratio. The evaluation results are shown in Table 1.

[0034] [Table 1]

[0035] As shown in Table 1, Reference example Although Example 1 had a lower maximum heat exchange capacity and average heat exchange capacity than Comparative Example 1, the frost formation time was extended by more than three times. Reference example Although the frost formation time of Example 1 was shorter than that of Comparative Example 2, the maximum heat exchange capacity and the average heat exchange capacity were significantly improved. Reference example Compared with Comparative Examples 1 and 2, it can be said that Example 1 is capable of achieving both heat exchange performance and frost formation time.

[0036] <Embodiment 2> The configuration shown in FIG. Reference exampleUsing the configuration of Example 1 as a standard, the allowable range of fin pitch combinations was evaluated for heat exchangers of several different configurations in which the fin pitches Pb, Pt, and Pm were changed as shown in Table 2, under the same conditions as in the evaluation test of Example 1.

[0037] Regarding the outlet temperature of the air, which is the cooled medium, a temperature of -5.2°C or below was evaluated as appropriate, while anything above that was evaluated as insufficient cooling performance.

[0038] The pressure loss (Pa) was measured by measuring the pressure difference (pressure loss) between the air inlet and outlet of the heat exchanger (group of fins) in the ventilation flow path with a micro-differential pressure gauge, and the pressure loss was measured one hour after the start of ventilation. A pressure loss of 10 Pa or less was evaluated as appropriate, and a pressure loss above that was evaluated as high pressure loss.

[0039] Regarding frost resistance, the pressure loss 48 hours after the start of ventilation was measured in the same manner as above, and the frost resistance was evaluated as acceptable if the pressure loss was 10 Pa or less, and as unacceptable if the pressure loss due to frost on the fins exceeded 10 Pa. The evaluation results are shown in Table 2.

[0040] [Table 2]

[0041] As can be seen from Table 2, the configurations E1, E4, E9 to E11, E13, and E14, which have fin pitches Pb, Pt, and Pm satisfying the relationships 10 mm≦Pb≦20 mm, 1.8 mm≦Pt≦5.0 mm, 2.2≦Pm≦15 mm, 2≦Pb / Pt≦11.2, and 1≦Pm / Pt≦8.4, were evaluated as appropriate or acceptable for all evaluation items. Among them, the configurations E1 and E4, which have Pt≧2.2 mm and the relationships Pb / Pt≦5 and Pm / Pt≦6.8, are found to have particularly small pressure loss and excellent, well-balanced characteristics.

[0042] On the other hand, in the configurations C2 and C3, the fin pitch Pb at the most upstream side was too narrow, the Pb / Pt range was outside the appropriate range, and the frost formation was unacceptable.

[0043] In configuration C5, the fin pitch Pb at the most upstream portion was too wide, resulting in insufficient cooling performance.

[0044] In the configuration C6, the fin pitch Pm at the middle position was too narrow, and the Pm / Pt range was outside the appropriate range, resulting in too high pressure loss.

[0045] In configuration C7, the fin pitch Pm at the middle position was too wide, resulting in insufficient cooling performance.

[0046] In configuration C8, the fin pitch Pt at the most downstream side was too narrow, and the Pb / Pt range and the Pm / Pt range were outside the appropriate range, resulting in too high pressure loss.

[0047] In the configuration C12, the fin pitch Pt at the most downstream side was too wide, resulting in insufficient cooling performance.

Claims

1. A heat exchanger for a refrigerator / freezer, comprising: a plurality of fin groups each having a plurality of fins arranged in a row in parallel with each other at a predetermined interval; the plurality of fin groups are arranged at predetermined intervals in a flow direction of a fluid to be cooled flowing through the refrigerator / freezer; and one or a plurality of metal pipes are arranged to sequentially penetrate the fins in the fin groups and form a serpentine shape, The fin is made of an aluminum or aluminum alloy plate, the multiple stages of fin groups include an upstream fin group consisting of only one stage of fin groups located at the most upstream side in the flow direction of the cooled fluid, a downstream fin group consisting of only one stage of fin groups located at the most downstream side, and an intermediate fin group consisting of multiple stages of fin groups located therebetween; The fin pitch Pb in the upstream fin group, the fin pitch Pt in the downstream fin group, and the fin pitch Pm in the intermediate fin group are 10 mm≦Pb≦20 mm, 1.8mm≦Pt≦5.0mm, 10 mm≦Pm≦15 mm, 4.0≦Pb / Pt≦11.1, 3.0≦Pm / Pt≦8.3, 1<Pb / Pm≦9.1 A heat exchanger for a refrigerator / freezer, comprising:

2. 2. The heat exchanger for a refrigerator according to claim 1, wherein the metal pipe is an inner grooved pipe having an outer diameter of 5 to 10 mm.

3. 3. The heat exchanger for a refrigerator according to claim 1, wherein the metal pipe is made of copper or a copper alloy, or aluminum or an aluminum alloy.

4. 4. The heat exchanger for a refrigerator according to claim 1, wherein a plurality of said metal pipes penetrate one of said fins.

5. The refrigerants circulating in the metal pipes are R134a, R600a, CO 2 The heat exchanger for a refrigerator according to any one of claims 1 to 4, wherein

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