JP2020143806A - Heat exchanger, air conditioner and method for manufacturing heat exchanger - Google Patents

Abstract

To control frost from adhering to a part without a fin in an end part of a flat tube to be connected to a header, in a heat exchanger.SOLUTION: A heat exchanger 15 includes: headers 21, 22; multiple flat tubes 23 of which end parts are connected to the headers 21, 22; and a fin group 24 comprising a number of fins 24a arranged while arrayed in a longitudinal direction of the flat tubes 23 and coming into contact with surfaces of the flat tubes 23. A part 23b between the headers 21, 22 and the fin group 24 of the surfaces of the flat tubes 23 has water-repellent property of which contact angle exceeds 90°.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to heat exchangers, air conditioners, and methods of manufacturing heat exchangers.

When heating is performed by an air conditioner in an environment where the outside air temperature is low, frost may adhere to the heat exchanger (evaporator) of the outdoor unit. Adhesion of frost on such a heat exchanger obstructs the flow of air passing through the heat exchanger and causes deterioration of heat exchange performance. In order to prevent the adhesion of frost to the heat exchanger, Patent Document 1 states that a hydrophilic film is formed on the fins of the heat exchanger to facilitate the flow of water droplets adhering to the surface of the fins and prevent the adhesion of frost. The technology is disclosed.

JP-A-2009-229040

In recent years, a microchannel heat exchanger has been used as a heat exchanger for an outdoor unit. This microchannel heat exchanger includes a header, a plurality of flat tubes arranged side by side in the longitudinal direction of the header, and a group of fins composed of a large number of fins in contact with the surface of the flat tubes. At the end of the flat tube connected to the header, there is usually a portion where fins are not provided due to manufacturing reasons or the like. In this part, heat exchange with air is not sufficient, and the surface temperature becomes low during the heating operation, so that there is a high possibility that frost adheres. When frost adheres to the end of the flat tube, the frost spreads to the header and fins starting from that portion, which further deteriorates the heat exchange efficiency.

An object of the present disclosure is to suppress the adhesion of frost in a finless portion at the end of a flat tube connected to a header in a heat exchanger.

(1) The heat exchanger of the present disclosure is
Header and
A plurality of flat tubes whose ends are connected to the header,
A group of fins composed of a large number of fins arranged side by side in the longitudinal direction of the flat tube and in contact with the surface of the flat tube.
The portion of the surface of the flat tube between the header and the fin group has water repellency having a contact angle of more than 90 °.

With such a configuration, it becomes difficult for water droplets to adhere to the surface of the flat tube between the header and the fin group, and the adhesion of frost can also be suppressed.

(2) Preferably, the surface of the header has water repellency having a contact angle of more than 90 °.
With such a configuration, the adhesion of frost on the surface of the header can also be suppressed.

(3) Preferably, the portion of the surface of the flat tube provided with the fin group has hydrophilicity with a contact angle of 90 ° or less.
With such a configuration, in the portion of the flat tube where the fins are provided, even if the water vapor in the air condenses and water droplets adhere, it easily flows down, and the water droplets obstruct the air flow or freeze on the surface of the flat tube. It can be suppressed.

(4) Preferably, the surface of the fin has hydrophilicity with a contact angle of 90 ° or less.
With such a configuration, even if water vapor in the air condenses and water droplets adhere to the fins, they easily flow down, and it is possible to prevent the water droplets from obstructing the flow of air or freezing on the surface of the fins. ..

(5) The heat exchanger of the present disclosure is
Header and
A plurality of flat tubes whose ends are connected to the header,
It is provided with a group of fins composed of a large number of fins arranged side by side in the longitudinal direction of the flat tube and in contact with the surface of the flat tube.
A water-repellent layer that further enhances water repellency is provided on a portion of the surface of the flat tube between the header and the fin group.

With such a configuration, water droplets are less likely to adhere to the surface of the flat tube between the header and the fin group, and frost adhesion and freezing of water droplets can be suppressed.

(6) The air conditioner of the present disclosure has the heat exchanger according to any one of (1) to (4) above.

(7) The method for manufacturing the heat exchanger of the present disclosure is as follows.
It includes a header, a plurality of flat tubes whose ends are connected to the header, and a group of fins composed of a large number of fins arranged side by side in the longitudinal direction of the flat tubes and connected to the surface of the flat tubes. It is a method of manufacturing a heat exchanger.
A step of applying a water repellent treatment to further enhance water repellency is included in a portion of the surface of the flat tube between the header and the fin group.

With such a configuration, it becomes difficult for water droplets to adhere to the surface of the flat tube between the header and the fin group, and the adhesion of frost can be suppressed.

It is a schematic plan view which looked at the inside of the air conditioner which concerns on 1st Embodiment from above. It is a schematic front view of a heat exchanger. FIG. 2 is a cross-sectional view taken along the line AA of FIG. FIG. 3 is a cross-sectional view taken along the line BB of FIG. It is explanatory drawing of water repellency and hydrophilicity.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
<First Embodiment>
FIG. 1 is a schematic plan view of the inside of the air conditioner according to the first embodiment as viewed from above.
The air conditioner 10 is a separate type separated into an outdoor unit 11 and an indoor unit, and FIG. 1 shows the outdoor unit 11. The outdoor unit 11 includes a housing 12. The housing 12 is formed in a rectangular parallelepiped shape and is formed in a rectangular shape in a plan view. The inside of the housing 12 is divided into a machine room S1 and a heat exchange room S2 by a partition wall 13.

The compressor 14 is housed in the machine room S1 of the housing 12. In addition to the compressor 14, the machine room S1 also houses a four-way switching valve (not shown), an accumulator, an oil separator, an expansion valve, and the like.

A heat exchanger 15, a fan 16, and the like are housed in the heat exchange chamber S2 of the housing 12.
Air intake ports 12a1 and 12b1 are formed on two adjacent side walls 12a and 12b of the housing 12 arranged on the heat exchange chamber S2 side. The fan 16 is arranged to face the other side wall 12c adjacent to one side wall 12b on which the air intake 12b1 is formed. An air outlet 12c1 is formed on the side wall 12c. When the fan 16 operates, air is taken into the housing 12 from the air intake ports 12a1 and 12b1 and discharged from the air outlet 12c1. The arrow a shown in FIG. 1 indicates the direction of the flow of air taken into the housing 12. Hereinafter, the direction of air flow is also referred to as "air flow direction".

The heat exchanger 15 is formed in an L shape in a plan view. The heat exchanger 15 bends near the corner 12e between the two side walls 12a and 12b where the air intakes 12a and 12b1 are formed, and is arranged along the two side walls 12a and 12b.

FIG. 2 is a schematic front view of the heat exchanger 15.
The heat exchanger 15 is a microchannel type heat exchanger. The heat exchanger 15 has a pair of headers 21 and 22, a heat transfer tube 23, and a fin group 24. These are made of aluminum or aluminum alloy.

The headers 21 and 22 are arranged with their longitudinal directions facing up and down. The pair of headers 21 and 22 are composed of a gas side header 21 and a liquid side header 22. A gaseous refrigerant flows through the gas side header 21. A liquid (or gas-liquid two-phase) refrigerant flows through the liquid-side header 22.

The heat transfer tube 23 is composed of a flat tube having a length in the air flow direction a (see FIG. 1) longer than the length in the longitudinal direction of the headers 21 and 22. Hereinafter, the heat transfer tube is referred to as a flat tube 23. A large number of flat tubes 23 are provided side by side in the vertical direction, which is the longitudinal direction of the headers 21 and 22. One end of the flat tube 23 is connected to the gas side header 21, and the other end of the flat tube 23 is connected to the liquid side header 22. The longitudinal direction of the flat pipe 23 is a direction extending from one end connected to the gas side header 21 of the flat pipe 23 to the other end connected to the liquid side header 22. The longitudinal direction of the flat tube 23 is orthogonal to the longitudinal direction of the headers 21 and 22, and is also orthogonal to the air flow direction a.

FIG. 3 is a cross-sectional view taken along the line AA of FIG. FIG. 4 is a cross-sectional view taken along the line BB of FIG.
As shown in FIG. 4, the flat tube 23 has a plurality of flow paths 23a arranged side by side in the air flow direction a. As shown in FIG. 1, the refrigerant that has flowed into the flat pipe 23 from one header flows through each flow path 23a and flows into the other header. When the heat exchanger 15 is used as an evaporator, a gas-liquid two-phase refrigerant flows into the flat pipe 23 from the liquid side header 22, and the refrigerant evaporates while flowing in each flow path 23a to become a gaseous refrigerant. Flows into the gas side header 21. The refrigerant that has flowed into the gas side header 21 is sucked into the compressor 14 via the gas pipe.

As shown in FIG. 3, the fin group 24 includes a large number of fins 24a arranged side by side in the longitudinal direction of the flat tube 23. A gap L is provided between the gas side header 21 and the fin group 24. As shown in FIG. 4, each fin 24a is formed with a large number of grooves 24b at intervals in the vertical direction. A flat tube 23 is inserted into the groove 24b, and fins 24a are fixed to the flat tube 23. The fin 24a includes a protruding portion 24c that protrudes upstream of the flat tube 23 in the air flow direction a.

The headers 21 and 22, the flat tube 23, and the fin group 24 constituting the heat exchanger 15 of the present embodiment have different "wetting properties" of water depending on the parts. Wetting properties are primarily used to represent the affinity of a liquid for a solid surface. In the case of water, wettability can be expressed by the terms "water repellent" and "hydrophilic".

FIG. 5 is an explanatory diagram of water repellency and hydrophilicity. When water W is in contact with the surface S of the solid, the angle formed by the surface of the liquid W with the surface S of the solid is called the contact angle θ. In the present embodiment, as shown in FIG. 5A, the property of the solid surface S when the contact angle θ exceeds 90 ° is referred to as “water repellency”. As shown in FIG. 5B, the property of the solid surface S when the contact angle θ is 90 ° or less is referred to as “hydrophilic”.

The flat tube 23 constituting the heat exchanger 15 has different wettability depending on the site. Specifically, as shown in FIG. 3, a portion 23b (a portion arranged in the range of reference numeral L in FIG. 3) between the gas side header 21 and the fin group 24 on the surface of the flat tube 23 is The portion 23c that has water repellency and is provided with the fin group 24 is hydrophilic. Of the surface of the flat tube 23, the portion between the liquid side header 22 and the fin group 24 also has water repellency.

The surfaces of the gas side header 21 and the liquid side header 22 have water repellency. The surface of each fin 24a constituting the fin group 24 has hydrophilicity.
The hydrophilicity of the flat tube 23 and the fins 24a is given by the surface properties of the constituent material itself. The water repellency of the flat tube 23 and the headers 21 and 22 is provided by applying a water repellent treatment to the surfaces thereof and providing a water repellent layer that further enhances the water repellency.

For example, a water repellent treatment can be applied by spraying a water repellent material. As the water-repellent material, a fluorine-based material, a silicone-based material, or the like can be adopted. In addition to spraying the water-repellent material by spraying, application by a brush or the like, immersion in the water-repellent material, or the like may be adopted. However, the water repellent treatment can be easily applied by spraying the water repellent material. As a method of water repellent treatment, surface treatment can also be adopted.

The water repellency of the flat tube 23 and the headers 21 and 22 may be given by the surface properties of the constituent materials themselves, and the hydrophilicity of the flat tube 23 and the fins 24a is obtained by subjecting these surfaces to a hydrophilic treatment. It may be given by providing a hydrophilic layer that enhances hydrophilicity.

When the heating operation is performed by the air conditioner 10, the heat exchanger 15 becomes an evaporator, and a refrigerant having a temperature lower than that of the outside air flows in the flat pipe 23. The portion 23b of the surface of the flat tube 23 where the fin group 24 is not provided has a lower heat exchange efficiency than the portion 23c where the fin group 24 is provided, so that the temperature becomes lower. Therefore, water vapor in the air may form frost and adhere to it, or it may adhere as water droplets due to condensation and freeze.

In the present embodiment, of the surface of the flat tube 23, the portion 23b between each header 21 and 22 and the fin group 24 has water repellency, so that the contact area of water droplets becomes small and water droplets adhere. It becomes difficult. Therefore, frost is less likely to adhere. Water droplets adhering to the flat tube 23 due to condensation are easily removed by blowing air from the air intake port 12a1 or the like, and freezing is suppressed. Therefore, the frost and ice generated in the portion 23b of the flat tube 23 do not spread to the headers 21 and 22 and the fin group 24, and the deterioration of the heat exchange efficiency can be suppressed.

Since the surfaces of the headers 21 and 22 also have water repellency, it is possible to suppress the adhesion of frost and the freezing of water droplets. In particular, since the headers 21 and 22 are arranged along the vertical direction, the attached water droplets can be easily flowed downward by their own weight.

Of the surface of the flat tube 23, the portion 23c provided with the fin group 24 has hydrophilicity, so even if water droplets adhere due to the condensation of water vapor in the air, the water droplets are still present on the flat tube 23. It spreads on the surface of the water vapor and becomes easy to flow, and freezing is suppressed. Since the surface of each fin 24a is also hydrophilic, the attached water droplets easily flow and freezing is prevented.

<Action and effect of the embodiment>
The heat exchanger 15 of the above-described embodiment has a header (gas side header 21 and liquid side header 22), a plurality of flat tubes 23 whose ends are connected to headers 21 and 22, and in the longitudinal direction of the flat tubes 23. A fin group 24 composed of a large number of fins 24a arranged side by side and in contact with the surface of the flat tube 23 is provided, and a contact angle between the headers 21 and 22 and the fin group 24 on the surface of the flat tube 23 is provided. Has a water repellency of more than 90 °. With such a configuration, water droplets are less likely to adhere to the surface of the flat tube 23 between the headers 21 and 22 and the fin group 24, and frost adhesion and freezing of water droplets can be suppressed.

In the above-described embodiment, the surfaces of the headers 21 and 22 have water repellency with a contact angle of more than 90 °. Therefore, it is possible to suppress the adhesion of frost and the freezing of water droplets on the surfaces of the headers 21 and 22.

In the above-described embodiment, the portion 23c of the surface of the flat tube 23 provided with the fin group 24 has hydrophilicity with a contact angle of 90 ° or less. Therefore, in the portion 23c of the flat tube 23 where the fin group 24 is provided, even if the water vapor in the air condenses and water droplets adhere to it, it easily flows down, and the water droplets obstruct the air flow or freeze on the surface of the flat tube. It can be suppressed.

In the above-described embodiment, the surface of the fin 24a has hydrophilicity with a contact angle of 90 ° or less. Therefore, even if the water vapor in the air condenses and water droplets adhere to the fins 24a, they easily flow down, and it is possible to prevent the water droplets from obstructing the flow of air or freezing on the surface of the fins 24a.

The heat exchanger 15 of the above-described embodiment includes headers 21 and 22, a plurality of flat tubes 23 whose ends are connected to headers 21 and 22, and flat tubes 23 arranged side by side in the longitudinal direction of the flat tubes 23. A fin group 24 composed of a large number of fins 24a in contact with the surface is provided, and a portion 23b between the headers 21 and 22 and the fin group 24 on the surface of the flat tube 23 is water repellent to further enhance water repellency. Layers are provided. With such a configuration, water droplets are less likely to adhere to the surface of the flat tube 23 between the headers 21 and 22 and the fin group 24, and frost adhesion and freezing of water droplets can be suppressed.

The heat exchanger 15 of the above-described embodiment is manufactured by applying a water-repellent treatment to further enhance water repellency between the headers 21 and 22 and the fin group 24 on the surface of the flat tube 23. Therefore, it becomes difficult for water droplets to adhere to the surface 23b of the flat tube 23 between the headers 21 and 22 and the fin group 24, and frost adhesion and freezing of water droplets can be suppressed.

It should be noted that the present disclosure is not limited to the above examples, and is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.
In the above-described embodiment, the surfaces of the gas side header 21 and the liquid side header 22 have water repellency, but may have hydrophilicity. The portion 23c of the surface of the flat tube 23 provided with the fin group 24, or the surface of the fins 24a may have water repellency.

In each of the above-described embodiments, the heat exchanger 15 may include two or more rows of flat tubes 23 in the air flow direction a.
In each of the above-described embodiments, the heat exchanger 15 is formed in an L shape along two adjacent side walls 12a and 12b of the housing 12 in a plan view, but one side wall or three or more side walls. It may be formed along the side wall.

In each of the above-described embodiments, the outdoor unit 11 blows air from the side wall 12c of the housing 12 by the fan 16, but may be configured to blow air from the upper surface of the housing 12.

10: Air conditioner 15: Heat exchanger 21: Gas side header 22: Liquid side header 23: Flat tube 23b: Water repellent part 23c: Hydrophilic part 24: Fin group 24a: Fins

Claims (7)

Headers (21, 22) and
A plurality of flat tubes (23) whose ends are connected to the headers (21, 22),
A fin group (24) composed of a large number of fins (24a) arranged side by side in the longitudinal direction of the flat tube (23) and in contact with the surface of the flat tube (23) is provided.
A heat exchanger in which a portion (23b) of the surface of the flat tube (23) between the header (21,22) and the fin group (24) has a water repellency having a contact angle of more than 90 °. The heat exchanger according to claim 1, wherein the surface of the headers (21, 22) has water repellency having a contact angle of more than 90 °. The heat exchanger according to claim 1 or 2, wherein the portion (23c) of the surface of the flat tube (23) provided with the fin group (24) has hydrophilicity with a contact angle of 90 ° or less. The heat exchanger according to any one of claims 1 to 3, wherein the surface of the fin (24a) has hydrophilicity having a contact angle of 90 ° or less. Headers (21, 22) and
A plurality of flat tubes (23) whose ends are connected to the headers (21, 22),
A fin group (24) composed of a large number of fins (24a) arranged side by side in the longitudinal direction of the flat tube (23) and in contact with the surface of the flat tube (23) is provided.
A water-repellent layer that further enhances water repellency is provided on a portion (23b) between the header (21, 22) and the fin group (24) on the surface of the flat tube (23) for heat exchange. vessel. An air conditioner having the heat exchanger (15) according to any one of claims 1 to 5. A header (21,22), a plurality of flat tubes (23) whose ends are connected to the headers (21,22), and the flat tubes (23) arranged side by side in the longitudinal direction of the flat tubes (23). A heat exchanger (15) including a fin group (24) composed of a large number of fins (24a) connected to the surface of).
Heat exchange including a step of applying a water repellent treatment to a portion (23b) between the header (21, 22) and the fin group (24) on the surface of the flat tube (23) to further enhance water repellency. How to make a vessel.

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