JPH02192597A - Heat exchanger - Google Patents

Abstract

PURPOSE:To delay blockading due to the layer of frost and eliminate the deterioration of heating capacity when heating operation is reopened after defrosting by employing a water repellent fin member, with fine grooves, as a plate fin. CONSTITUTION:The main body of a heat exchanger is constituted by a method wherein a heat transfer tube penetrating hole is bored on a plate type fin 5 made of aluminum, on which a water repellent film 6 is applied on the surface thereof and fine grooves 7 are formed, fin collars 2 are established with equal intervals to penetrate a heat transfer tube 3 made of copper and, thereafter, the tube 3 is fixed and adhered to the plate type fin 5 by means of expanding or the like. Ethylene tetrafluoride resin coating having the pure water contact angle of 110 deg., for example, is used as the water repellent film. Either one of water repellent coatings such as the copolymer resin coating of ethylene tetrafluoride and propylene hexafluoride, silicon resin coating and the like or water repellent surface treatment coated with fatty acid such as stearic acid, lauric acid and the like may be employed as a water repellent surface treatment material. The width and the depth of the fine grooves are not specified especially but the effect of capillary phenomenon is higher when the grooves are provided with more acute angle.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heat exchanger used in cooling systems such as air conditioning equipment, freezing and refrigeration equipment, and the like.

BACKGROUND OF THE INVENTION In recent years, the number of air conditioning equipment, so-called heat pumps, has been increasing year by year, and frost formation on outdoor heat exchangers during heating operation has become a problem. In addition, similar problems occur in freezing and refrigerating equipment, and there is a strong need for measures against frosting of the heat exchanger itself.

An example of a conventional heat exchanger will be described below with reference to the drawings. FIG. 3 shows a partial side sectional view of a conventional heat exchanger, and FIG. 4 shows a top sectional view.

Heat exchanger tube insertion holes are bored in the plate-shaped fin 1, which is a thin metal plate such as iron, copper, or aluminum, and fin collars 2 are set up at equal intervals, and copper, a! After the heat transfer tube 3, which is a metal tube such as reminium, is inserted, it is tightly fixed to the plate-shaped fin 1 by means such as tube expansion.

A refrigerant is made to flow inside the heat exchanger tube 3, and the heat is transmitted to the fins 1 from the fin collar 2 which is closely attached and fixed to the heat exchanger tube 3. On the other hand, when the gas flows in the direction of the four outlined arrows and passes over the fins 1, υ heat is exchanged due to the temperature difference between the gas, the heat transfer tubes 3, and the fins 1, and due to this action, the refrigerant and the gas Heat exchange is performed continuously.

Problems to be Solved by the Invention Among the above effects, taking an outdoor heat exchanger as an example during heating operation of a heat pump, if the temperature of the inflowing gas in the four directions of the white arrows is low, the temperature of the heat exchanger will decrease. The evaporation temperature of the refrigerant flowing inside becomes 0° C. or lower, and condensed water is first generated on the fin surface and a portion of the fin collar around the heat transfer tube. If the fin surface is hydrophilic, the condensed water forms a film and freezes early. As the operating time progresses, frost formation progresses. As the frost grows, the spaces between the fins become clogged, reducing gas flow resistance. This causes ventilation resistance in the heat exchanger, which in turn impedes heat exchange between the air and the refrigerant. Further, when the fin surface is water repellent, the condensed water does not form into droplets, and even if the fin surface temperature drops considerably, it remains in the droplet state for a relatively long time. The density of this droplet is several times greater compared to frost. These droplets eventually freeze, forming frost.

Therefore, the frost that grows on a water-repellent surface is denser than the frost that grows on a hydrophilic surface. In other words, it takes longer for the fins to become clogged due to frost.

However, after heating operation is interrupted and defrosting operation is performed by means such as reverse cycle, the defrosting water droplets may remain on the fin surface as droplets because the fin surface is water repellent. . Therefore, when the operation is restarted after defrosting, there is a problem that the remaining water droplets create ventilation resistance from the beginning, resulting in a decrease in heating capacity. Therefore, the time for clogging between the fins, which are made of a water-repellent surface that forms high-density frost and does not leave water droplets behind after defrosting, is short, allowing ventilation even after restarting operation after defrosting. It is necessary to develop a heat exchanger with low resistance and no reduction in heating capacity.

Note that water repellency here refers to a surface tension that is higher than that of the untreated surface of thin metal sheets such as iron, copper, and aluminum, which are the materials of the plate-shaped fins, and is expressed in terms of the contact angle with pure water. 500 or more, and hydrophilicity refers to a surface whose contact angle with pure water is less than 50'.

Means for Solving the Problems In order to solve the above problems, the present invention comprises a plurality of plate-shaped fins arranged in parallel at regular intervals and through which airflow flows, and a heat transfer tube inserted through the plate-shaped fins at right angles. In this heat exchanger, a water-repellent fin material with fine grooves formed therein is used as the plate-like fins.

Function When the fin surface temperature of the outdoor heat exchanger during heating operation of a heat pump is below 0°C and moisture in the air adheres to it, the condensed water does not suddenly become exposed even if the surface temperature is very low, and the condensed water It adheres as liquid moisture and is retained for a long time as droplets of liquid moisture. After that, the water freezes, frost forms on top of it, and frost formation progresses.

However, by forming the plate-like fins with water repellency and fine grooves as in the structure of the present invention, the moisture in the air that is concentrated due to the water repellency effect becomes a liquid whose density is several times higher than that of frost. It adheres to the fin surface as moisture, and compared to a hydrophilic surface, it takes longer for the fins to become clogged due to frost. In addition, after defrosting operation, the droplets remaining on the fin surface are pulled by the fine grooves formed on the fin surface by capillary phenomenon, quickly fall downward from the fin surface, and drop onto the fin surface. It does not remain behind, and even when operation is resumed after defrosting, it does not create ventilation resistance and does not reduce heating capacity.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a partial side sectional view of a heat exchanger according to an embodiment of the present invention, and FIG. 2 shows a top sectional view. In FIG. 1 and FIG. 2, an aluminum plate-shaped fin 5 with a water-repellent coating 6 formed on the surface and a fine expiry formed thereon.
At the same time, heat exchanger tube insertion holes are bored in the fin collars 2, and the fin collars 2 are stood up at equal intervals, and after inserting the copper heat exchanger tubes 3 through them, they are tightly fixed to the plate-like fins 5 by means such as tube expansion, thereby forming the main body. It is. The effect will be explained below.

A refrigerant is made to flow inside the heat exchanger tube 3, and the heat is transmitted from the fin collar 2 closely fixed to the heat exchanger tube onto the fins 5,
Gas is caused to flow through the heat exchanger and passed over the fins, and heat is exchanged due to the temperature difference between the gas, the fins 5, and the heat transfer tubes 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 condenses on the fin surfaces. However, since the fin surface is water repellent, even if the fin surface is below 0° C., it will not freeze on the fin surface and will be retained in the form of liquid water.

Compared to the frost layer, liquid moisture is several times more dense. Further, even after this water freezes, the frozen water is dispersed, so 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 significantly delayed. or,
Even after defrosting, water droplets remaining on the plate-like fins ε remain in the fine grooves 7.
It is pulled by capillary action, quickly flows downward, and does not remain on the plate-like fins 6, and even when heating operation is restarted, it does not create ventilation resistance and does not reduce heating performance.

The water-repellent film according to this example has a pure water contact angle of 1
A 1o0 47 fluoride ethylene resin paint was used. As a water-repellent surface treatment material, a copolymer resin paint of 47-ethylene fluoride and propylene hexafluoride is used.

Water-repellent paints such as silicone resin paints, stearic acid.

Any material with water repellency, such as one whose surface is treated with fatty acids such as lauric acid, is possible.

Regarding the fine grooves, although the width and depth of the grooves are not particularly specified, the more acute the grooves are, the higher the effect of capillary confinement is. If the groove spacing is narrow, the water repellent effect on the surface will be weakened, and if it is wide, there will be a lot of droplets remaining, so it is desirable that the groove spacing is about 0.1 to 1.0H.

As described above, according to this embodiment, by applying water-repellent plate-shaped fins with fine grooves formed to the heat exchanger of a heat pump, clogging of the heat exchanger by a layer of frost is delayed, and Even after defrosting, water droplets do not remain on the fins, there is no increase in ventilation resistance after heating operation is resumed, and there is no decrease in heating capacity.

Effects of the Invention As described above, the present invention consists of a large number of plate-shaped fins arranged in parallel at regular intervals, through which airflow flows, and a heat transfer tube inserted at right angles to the plate-shaped fins. Since the heat exchanger has plate-shaped fins made of water-based fin material with fine grooves, it delays blockage due to frost layer and prevents the heating capacity from decreasing even after heating operation resumes after defrosting. Can be done.

[Brief explanation of the drawing]

FIG. 1 shows a partial side cross section of a heat exchanger according to an embodiment of the present invention.
2 is a top sectional view of the same portion, FIG. 3 is a partial side sectional view of the conventional example, and FIG. 4 is a top sectional view of the same portion. 1.5... Plate fin, 6... Water repellent film, 7... Fine groove. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1st
Figure 5 - Retaining forest fin 7 - Fine groove diagram

Claims (1)

[Claims] Consisting of a large number of plate-shaped fins arranged in parallel at regular intervals and through which airflow flows, and a heat transfer tube inserted through the plate-shaped fins at right angles, the plate-shaped fins are coated with a water-repellent coating and have fine grooves formed therein. A heat exchanger characterized in that it is made of a fin material.