JPH04165297A - Heat exchanger - Google Patents

Abstract

PURPOSE:To suppress growth of frost and to prevent a decrease in cooling capacity by reducing a distance between a heat transfer side end of an agitating blade and a heat transfer shorter than a rising point for rising the gradient of a convection heat transfer rate rise upon reduction of the distance. CONSTITUTION:When an agitating blade 21 on a disc 22 is rotated by the rotation of a motor 23, the air is driven by a centrifugal force, fed from an air inlet 24 to flow from the inside toward the outside on a heat transfer surface 1a. A distance between the side end of the blade and the transfer surface is approached from a temperature boundary layer so that the blade crosses the layer. Accordingly, an air flow near the transfer surface is disordered to improve its heat transfer ratio. When the air fed into a heat exchanger is cooled on the transfer surface, if the temperature of the transfer surface is below the freezing point of water, steam in the flowing air is solidified on the transfer surface to form a frost layer. If it is above the freezing point, dew-condensation occurs in response to the moisture of the air. Thereafter, when it is further cooled so that the temperature of the transfer surface becomes below the freezing point, water droplets adhered to the transfer surface are solidified to become ice droplets. These frost, water droplets, ice droplets are scraped by the transfer surface, and discharged from an air diffuser by a centrifugal force.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat exchange device for exchanging heat between a cooled heat transfer body and air.

(Prior Art) FIG. 9 is a block diagram schematically showing a heat transfer form of a heat exchange device disclosed in, for example, Japanese Utility Model Publication No. 58-34338.

In the figure, (1) is the heat transfer body, (1a) is the heat transfer surface, (
2) is a fan, and (3) is air on the heat transfer surface (1a). The solid arrows represent the direction of heat transfer, and the dashed arrows represent the air flow.

The air driven by the fan (2) flows over the heat transfer surface (1a) as shown by the dotted arrow in the figure.
) and air (3), the heat transfer surface (1a)
heat is transferred to the air (3).

[Problem to be solved by the invention]

The convective heat transfer coefficient between the heat transfer body (1) and the air (3), defined by the following equation, is determined only from the air flow velocity and the shape of the heat transfer body (1), but conventional heat exchange devices Since the structure is as follows, there is a problem in that the convective heat transfer coefficient is low and therefore a large heat transfer area is required.

h=Q/(SxΔT) (1)Q
: Amount of heat exchange S: Area of the heat transfer surface of the heat transfer body ΔT: Absolute value of the temperature difference between the heat transfer surface and the air Also, since the fan and the heat transfer body are installed far apart, the volume of the device increases. There was a problem.

Furthermore, when air passes through a heat exchange device and is cooled below the freezing point of water, frost forms on the heat transfer surface and if the frost layer grows thick, the reduction in air flow velocity and the thermal resistance of the frost can cause frost formation on the heat transfer surface. , the cooling capacity will be significantly reduced. Therefore, it is necessary to make the air flow path wide in advance so that it is not blocked by frost. Therefore, there was a problem that the volume of the device became large.

Further, when the frost has grown to a certain extent, it is necessary to interrupt the operation of the heat exchange device and perform a defrosting operation such as heating the heat transfer surface. Therefore, in order to continuously cool the air, there is a problem in that a plurality of heat exchange devices must be installed and operated alternately.

Regarding the above problem, the same applicant has already filed a complaint on September 2, 1990.
Although the invention "Heat exchange device and method for manufacturing the same" has been applied for on date 0, there was a problem that the defrosting ability was insufficient even with the invention.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and has the function of suppressing the growth of frost and preventing a decrease in cooling capacity. The objective is to obtain a small and lightweight heat exchange device that does not require

The heat exchange device according to the present invention includes a heat transfer body whose heat transfer surface has been subjected to a water-repellent treatment, and a stirring blade that opposes the heat transfer body and moves relative to the heat transfer body, and the heat exchange device of the stirring blade has the above-mentioned heat transfer. The distance between the body side edge and the heat transfer body is made smaller than the starting point at which the gradient of convective heat transfer coefficient rises as the distance decreases, and a blade wiper or cutting blade is attached to the stirring blade. , the tip of the disturbance blade on the same population side is processed into an acute angle, and the tip of the opening provided in the heat transfer body or the disc on which the disturbance blade is implanted is processed into an acute angle, and When the temperature of the heat transfer surface is above the freezing point of water, the rotation speed of the stirring blade is higher than when it is below the freezing point, and the temperature of the heat transfer surface is kept above the freezing point of water and below the dew point of the incoming air. .

[Effect]

In the heat exchange device of the present invention, the disturbance blades that move relatively close to the heat transfer surface cross the temperature boundary layer on the heat transfer surface, so the air flow near the heat transfer DI11 is disturbed and heat is generated. Transmission rate is improved. In addition, the heat transfer surface is water-repellent, so when it is cooled to below freezing, water droplets with a small contact area with the heat transfer surface are formed, preventing the formation of a hard ice layer over the entire heat transfer surface. , the water droplets are easily scraped off by the agitation blades that rotate close to the heat transfer surface. Relatively soft frost that adheres to the entire heat transfer surface is also continuously scraped off by the stirring blades, so it does not grow to the extent that it reduces the heat transfer coefficient. Furthermore, the scraped water droplets and frost are discharged from the air outlet by centrifugal force. Therefore, there is no need to stop the heat exchange device and perform defrosting operation.

Further, by attaching a blade wiper or a cutting blade to the side end of all or part of the stirring blade, water droplets and frost can be scraped off more reliably.

In addition, when the inlet temperature of the air is higher than the dew point temperature, for example, when the heat exchange equipment starts operating, the temperature of the heat transfer surface near the air population is set above the freezing point and below the dew point to cause dew condensation, and then the stirring blades are rotated at high speed. This method prevents the formation of a hard ice layer by allowing water to drain out of the device. Also, by making the gust inlet at an acute angle, frost formation due to air collisions at that part is prevented from increasing.

(Example〕 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a vertical cross-sectional configuration diagram showing a heat exchange device according to an embodiment of the present invention. In the figure, (21) is a plurality of plate-shaped disturbance blades installed radially and perpendicularly to a disk (22) with an opening in the center, and (23) is a disk (22) with an opening in the center. )
(24) is the air inlet,
In this case, an opening provided in the center of the disk (22), (
25) is an air outlet. (S) is the distance between the side edge of the heat transfer body (1) of the stirring blade (21) and the heat transfer surface (1a) of the heat transfer body (1), and the gradient of increase in convective heat transfer coefficient as the distance decreases. is set to be smaller than the rising point at which it rises. In this case, the thickness is about 0.1 mm and is formed by the method described below. The distal end portion (26) of the stirring blade (21) is made of fluorocarbon resin which wears easily, in this case KYNAR (trade name of Pennwalt, Inc., USA) (PVDF=vinylidene difluoride resin). Further, the solid line arrows represent the heat transfer direction, the broken line arrows represent the air flow, and the double line arrows represent the rotation direction of the disk, that is, the stirring blade.

FIG. 2(a) is a plan view of the disk (22) on which the stirring blades (21) of FIG. 1 are installed, viewed from the heat transfer body side, and FIG. 2(b) is a side view of the same.

First, a manufacturing method for forming the gap S between the heat transfer body side end of the stirring blade (21) and the heat transfer surface (1) will be described.

As shown in the schematic explanatory diagram of FIG. 3, the disk (22) is attached with the stirring blade (21) in contact with the heat transfer surface (1),
When this disk (22) is rotated and the abutting portion of the stirring blade (21) and the heat transfer surface (1) are rubbed together, the tip (26) of the stirring blade (21) is made of a material that is easily worn. As a result, a gap S is formed between the side end of the heat transfer body (1) of the stirring blade (21) and the heat transfer surface (la).

Next, the operation of the heat exchanger of this embodiment will be explained. v
In figure J1, the rotation of the motor (23) causes the disc (2
2) When the upper stirring blade (21) rotates, the air is driven by centrifugal force, and the air inlet (21) is driven as shown by the dotted arrow in the figure.
24) and heat transfer surface (1a) from the inside to the outside.
flowing above. By making the distance between the side edge of the stirring blade and the heat transfer surface closer than the temperature boundary layer, the stirring blade crosses the temperature boundary layer, which disturbs the airflow near the heat transfer surface and improves the heat transfer coefficient. Furthermore, when air flowing into a heat exchanger is cooled on a heat transfer surface, the phenomenon differs depending on the temperature of the heat transfer surface. That is, when the heat transfer surface temperature is below the freezing point temperature of water, water vapor in the incoming air solidifies on the heat transfer surface to form a frost layer. When the temperature of the heat transfer surface is above the freezing point of water, condensation occurs depending on the humidity of the air, but when the heat transfer surface temperature reaches below the freezing point due to further cooling, condensation forms on the heat transfer surface. The water droplets solidify and become water droplets.

These frost, water droplets, and water droplets are scraped off from the heat transfer surface by rotating agitation blades and discharged from the air outlet by centrifugal force.

At this time, as shown in Figure 3, if a water-repellent film (31) such as Teflon or the like is applied to the heat transfer surface, when the air is cooled to below freezing point, water droplets (31) with a small contact area with the heat transfer surface ( 3
2) occurs, which prevents the formation of a hard ice layer over the entire heat transfer surface, and has the effect that water droplets are easily scraped off by the stirring blades that rotate close to the heat transfer surface. Relatively soft frost that adheres to the entire heat transfer surface is also continuously scraped off by the stirring blades, so it does not grow to the extent that it reduces the heat transfer coefficient. Further, the scraped water droplets and frost are discharged from the air outlet by centrifugal force. Therefore, there is no need to stop the heat exchanger and perform defrosting operation.

Furthermore, as shown in Figures 4 and 5, if a cutting blade (4J) or blade wiper (42) is attached to the stirring blade (2I) and rotated, the effect of easily scraping off water droplets or frost can be obtained. .

In addition, as shown in Fig. 6, the opening (51) that serves as the air inlet (24) provided in the rotating disk (22) and the tip (52) of the stirring blade where air flows in and collides with each other are arranged at an acute angle. By machining it, the opening that cannot be scraped off by the agitating blade (51)
It is possible to prevent frost from forming on the tips (52) of the stirring blades.

Next, a method of operating the heat exchanger of this embodiment will be explained.

Defrosting performance can be further improved by controlling the heat transfer surface temperature of the heat exchanger and controlling the rotation speed of the stirring blades. For example, when the heat exchanger starts operating, the incoming air temperature is around normal temperature and the absolute humidity is high. Further, the temperature of the heat transfer surface is also higher than the freezing point of water. Therefore, a relatively large amount of dew condensation occurs on the heat transfer surface, and when the heat transfer surface is further cooled, this large amount of moisture forms a hard ice film. To prevent this, the rotational speed of the stirring blades is temporarily increased until the artificial air temperature drops to near the freezing point, thereby preventing water droplets from being blown away by centrifugal force. During this time, the temperature of the heat transfer surface is maintained above the freezing point.

Furthermore, by keeping the central portion of the heat transfer surface at a temperature above the freezing point of water and below the dew point of incoming air, and by keeping the outer peripheral portion at a temperature below the freezing point, the following effects can be obtained. In other words, the moisture in the air is removed by forming water droplets in the center where the air flows in, so the water droplets can be easily blown away by the agitating blades, and then the outer periphery can be cooled to a predetermined temperature. The effect is that large amounts of water droplets are not generated.

In the above embodiment, the case where the disturbance blade (21) is installed in the disk (22) with an opening in the center is shown, but the seventh embodiment
Of course, the same effect can be obtained when the center of the heat transfer body (1) is opened as shown in the figure.

Furthermore, as shown in FIG. 8, the same effect can of course be obtained even if the stirring blades (21) and the heat transfer body (1) are arranged in multiple stages in the direction of the drive shaft.

〔Effect of the invention〕

Since the heat exchange device of the present invention is configured as described above, it has the effects described below.

The air is driven by a disturbance blade that moves relatively close to the heat transfer surface, increasing the turbulence near the heat transfer surface and increasing the convective heat transfer coefficient. Therefore, the heat transfer area is small and no fan is required, so it can be made smaller and weighed.

In addition, water droplets, water droplets, and frost adhering to the heat transfer surface are scraped off by the agitating blades that rotate in opposition to the heat transfer surface, and are discharged from the air outlet using centrifugal force, resulting in a low air volume and thermal resistance. Prevents a decrease in cooling capacity due to an increase in

Therefore, there is no need for defrosting operation, and continuous operation becomes possible. Furthermore, since there is no need to widen the air flow path in advance to prevent the air flow path from being blocked by frost, the device can be made more compact.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional configuration diagram showing the configuration of a heat exchange device according to an embodiment of the present invention, and FIGS. 2(a) and (b) are diagrams showing a disk on which the stirring blades of FIG. 1 are installed. , (a) is a plan view, (b) is a side view, Fig. 3 is a schematic cross-sectional view when water-repellent treatment is applied to the heat transfer surface, and Fig. 4 is a cross-sectional view when a cutting blade is attached to the stirring blade. Schematic diagram, Figure 5 is a cross-sectional schematic diagram when a blade wiper is attached to a stirring blade, Figure 6 is a cross-sectional diagram showing that the opening tip and the stirring blade are machined at an acute angle, and Figure 7 is a heat transfer body. FIG. 8 is a schematic cross-sectional view showing that the stirring blades and heat transfer bodies are arranged in multiple stages, and FIG. 9 is a configuration diagram of a conventional heat exchange device. (1) is the heat transfer body, (Ia) is the heat transfer surface, (21) is the stirring blade, (22) is the disk, (23) is the motor, (24) is the air inlet, (25) is the air outlet , (31) is a water repellent layer, (41) is a cutting blade, 42) is a blade wiper, (
51) is the opening, and (52) is the tip of the stirring blade. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (6)

[Claims] (1) A heat transfer body, and provided opposite to this heat transfer body,
A disturbance blade that moves relative to this is provided, and the distance between the side end of the heat transfer body of the disturbance blade and the heat transfer surface of the heat transfer body is determined by the slope of the increase in heat transfer coefficient as the distance decreases. A heat exchange device smaller than a point, characterized in that a heat transfer surface is treated with water repellency. (2) a heat transfer body, and provided opposite to this heat transfer body,
A disturbance blade that moves relative to this is provided, and the distance between the side end of the heat transfer body of the disturbance blade and the heat transfer surface of the heat transfer body is determined by the slope of the increase in heat transfer coefficient as the distance decreases. A heat exchange device smaller than a point, characterized in that a blade wiper or a cutting blade attached to the stirring blade is moved relative to the heat transfer body. (3) a heat transfer body, and provided opposite to this heat transfer body,
A disturbance blade that moves relative to this is provided, and the distance between the side end of the heat transfer body of the disturbance blade and the heat transfer surface of the heat transfer body is determined by the slope of the increase in heat transfer coefficient as the distance decreases. 1. A heat exchange device smaller than a point, characterized in that a tip of a stirring blade on an air inlet side is machined at an acute angle. (4) a heat transfer body, and provided opposite to this heat transfer body,
A disturbance blade that moves relative to this is provided, and the distance between the side end of the heat transfer body of the disturbance blade and the heat transfer surface of the heat transfer body is determined by the slope of the increase in heat transfer coefficient as the distance decreases. 1. A heat exchange device smaller than a point, characterized in that the tip of an opening provided in a disk in which a heat transfer body or a stirring blade is embedded is machined into an acute angle. (5) a heat transfer body, and provided opposite to the heat transfer body,
A disturbance blade that moves relative to this is provided, and the distance between the side end of the heat transfer body of the disturbance blade and the heat transfer surface of the heat transfer body is determined by the slope of the increase in heat transfer coefficient as the distance decreases. 1. A heat exchange device smaller than a point, characterized in that when the temperature of the heat transfer surface is above the freezing point of water, the rotational speed of the stirring blade is made higher than when the temperature is below the freezing point of water. (6) a heat transfer body, and provided opposite to the heat transfer body,
A disturbance blade that moves relative to this is provided, and the distance between the side end of the heat transfer body of the disturbance blade and the heat transfer surface of the heat transfer body is determined by the slope of the increase in heat transfer coefficient as the distance decreases. 1. A heat exchange device smaller than a point, characterized in that the temperature of the central portion of the heat transfer surface is set to be above the freezing point of water and below the dew point of incoming air.