JP2723558B2 - Heat exchanger - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger used for a cooling system such as an air conditioner and a refrigerator.

2. Description of the Related Art In recent years, the number of air conditioners in the form of heat pumps, so-called heat pumps, has been increasing year by year, and frost formation on the outdoor heat exchanger during heating operation has become a problem. In addition, freezers and refrigerators have similar problems, and there is an urgent need for measures against frost formation on the heat exchanger itself.

Hereinafter, an example of a conventional heat exchanger will be described with reference to the drawings. FIG. 3 is a partial side sectional view of a conventional heat exchanger, and FIG. 4 is a front sectional view. A heat transfer tube insertion hole is formed in a plate-like fin 1 which is a thin metal plate of iron, copper, aluminum or the like, and fin collars 2 are raised at equal intervals. After insertion, the fins 1 are tightly fixed to the plate-like fin 1 by means such as expansion. The refrigerant flows inside the heat transfer tube 3 and the heat is transferred to the heat transfer tube 3.
Is transmitted to the fin 1 from the fin collar 2 which is in close contact with and fixed to the fin 1. On the other hand, when the gas flows from the direction of the white arrow 4 and passes over the fins 1, heat is exchanged due to the temperature difference between the gas and the heat transfer tubes 3 and the fins 1. By this action, heat exchange between the refrigerant and the gas is performed. Are performed continuously.

Problems to be Solved by the Invention In the above operation, taking the outdoor heat exchanger at the time of the heating operation of the heat pump as an example, if the temperature of the inflow gas from the white arrow 4 direction is low, the inside of the heat exchanger The condensed water is first generated on the fin surface and the fin collar around the heat transfer tube. When the fin surface is hydrophilic, the condensed water becomes a film, freezes early, and frost formation progresses with the operation time, and as the frost grows,
The space between the fins is clogged, resulting in gas flow resistance, causing draft resistance of the heat exchanger, and thus hindering heat exchange between air and the refrigerant. When the fin surface is water-repellent, the condensed water is in the form of droplets, and is kept in a droplet state for a relatively long time even if the fin surface temperature is considerably lowered. The density of this droplet is several times greater than that of frost. However, these droplets freeze in time, and then the moisture in the air grows as frost.
At this time, since the frost grows intensively on the icing water, the frost growth per icing water is large, the frost height increases remarkably, and the fins are clogged. Therefore, regardless of whether the fin surface is hydrophilic or water repellent, the number of times that the heating operation should be interrupted and the defrosting operation should be performed by means such as a reverse cycle is frequent.

That is, there are problems such as a decrease in the heating capacity, discomfort caused by interrupting the heating operation, and a decrease in energy efficiency, and it is necessary to reduce frost formation on the heat exchanger.

Here, the term “water-repellent” refers to a material having a surface tension higher than the untreated surface of a thin metal plate such as iron, copper, or aluminum which is a material of the plate-like fin, and is expressed as a contact angle with pure water. ° or more, and hydrophilic means a surface with a contact angle with pure water of less than 50 °.

Means for Solving the Problems In order to solve the above problems, the present invention is arranged in parallel at regular intervals, a plate-like fin through which the air flow flows,
In a heat exchanger including a heat transfer tube inserted at right angles to the plate-like fin, a fin material which has been subjected to a surface treatment which is water-repellent and has fine irregularities is used as the plate-like fin.

When the fin surface is water repellent, the fin surface temperature is 0
° C or lower, and when moisture in the air adheres, even when the surface temperature is considerably low, it does not suddenly become frosted, but once adheres as condensed water, and is held as droplet-like liquid moisture for a long time.
Thereafter, the water freezes, and frost adheres thereon, and frost formation proceeds. For this reason, as in the configuration of the present invention, by performing a surface treatment that imparts water-repellent and fine irregularities to the plate-like fins, the moisture in the air that is concentrated due to its water-repellent effect has a density lower than that of frost. The liquid moisture adheres to the fin surface as liquid water several times larger, and the fine unevenness becomes a nucleus, and the liquid water exists on the fin in a finely dispersed form. This water eventually freezes, and then the water in the air that concentrates adheres to the frozen water as frost,
Until then, a large air path between adjacent fins is ensured. Further, since the frozen water is dispersed, the frost attached thereto is also dispersed, and the growth of the frost in the height direction is suppressed. Thereby, as a heat exchanger, blockage between the fins due to the frost layer can be delayed.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partial side sectional view of a heat exchanger according to an embodiment of the present invention, and FIG. 2 is a front sectional view. 1 and 2, a heat transfer tube insertion hole is formed in an aluminum plate-like fin 5 provided with a surface treatment layer 6 having a water-repellent surface and fine irregularities. After being raised at intervals, the copper heat transfer tube 3 is inserted into the space, and then tightly fixed to the plate-like fin 5 by means such as expansion,
The main body is configured. Hereinafter, the operation will be described. The refrigerant is caused to flow inside the heat transfer tube 3, and the heat is transferred from the fin collar 2 tightly fixed to the heat transfer tube to the fins 5, causing the gas to flow through the heat exchanger and passing over the fins,
Exchange of heat is performed by the temperature difference between the gas, the fins 5, and the heat transfer tube 3, and heat exchange between the refrigerant and the gas is continuously performed. The air flowing into the heat exchanger is cooled and moisture in the air on the fin surface condenses. However, since the fin surface is water-repellent, even when the fin surface is 0 ° C. or lower, the fin surface does not freeze, and is held in the form of liquid moisture around the fine irregularities 7 as nuclei. Liquid moisture is several times as dense as frost layers. In addition, since the frozen water is dispersed even after the water is frozen, the frost is also dispersed, and the growth of the frost layer in the height direction is suppressed. Therefore, blockage of the heat exchanger due to frost can be greatly delayed.

The water-repellent surface according to this embodiment has a pure water contact angle of 110 °.
The fine irregularities to be provided were realized by plasma etching using the tetrafluoroethylene resin paint.

Examples of the water-repellent surface treatment material include water-repellent paints such as copolymer resin paints of tetrafluoroethylene and hexafluoropropylene, silicone resin paints, and fatty acids such as stearic acid and lauric acid treated on the surface. Any method can be used as long as it is fine, and the same effect can be expected from the method for imparting fine irregularities by other surface roughening methods such as corona treatment, mechanical surface roughening, and dispersion of ceramic fine powder in the coating material. However, the maximum height of the irregularities is 10 μm or less, and the distance between the vertices of the irregularities is 10 μm.
The following fine irregularities exhibit the effect. When the maximum height of the irregularities is 10 μm or more, and the distance between the tops of the irregularities is 10 μm
In the case of m or more, the substantial contact area between the water droplet and the fin surface is large, the dew condensation water grows large, and the fin bridge is likely to be generated.

As described above, according to this embodiment, the plate-like fins are subjected to surface treatment with water repellency and fine irregularities,
Blockage of the heat exchanger by the frost layer can be significantly delayed.

Effect of the Invention As described above, the present invention comprises a plurality of plate-shaped fins arranged at regular intervals in parallel, between which a gas flow flows, and a heat transfer tube inserted at a right angle to the plate-shaped fins, and the surface thereof is formed. Because it is a heat exchanger that has formed a plate-like fin using a fin material that has been subjected to surface treatment with water repellency and fine irregularities,
Blockage by the frost layer can be greatly delayed.

[Brief description of the drawings]

1 is a partial side sectional view of a heat exchanger according to an embodiment of the present invention, FIG. 2 is a partial front sectional view of the same, FIG. 3 is a partial side sectional view of a conventional example, and FIG. FIG. 1, 5: plate-like fins, 6: water-repellent surface treatment layer provided with fine irregularities, 7: fine irregularities.

Claims (1)

(57) [Claims] 1. A plate-like fin, which is arranged in parallel at regular intervals and through which air flows, and a heat transfer tube inserted at right angles to the plate-like fin, wherein the plate-like fin is water-repellent and A heat exchanger made of a fin material having a fine unevenness in which the maximum height of the unevenness is 10 μm or less and the distance between the tops of the unevenness is 10 μm or less.