JPS59189292A - Heat exchanger - Google Patents

Abstract

PURPOSE:To improve the heat transfer rate by a structure wherein heat transfer medium is prevented from being separated while flowing between fins and at the same time changed the flow direction of flowing heat transfer medium in order to destruct the boundary layer formed on a fin base and then to adhere the main flow to the fin again. CONSTITUTION:A fin consists in forming bridge shape bits 10, which are shaved upright from the fin after lancing a fin base 9 and have thin wing sections, with the wind chord of which is inclined at the angle of attack of alpha degrees with respect to the flow direction of heat transfer medium. When fins are laminated and heat transfer medium is flowed between the fins, the heat transfer medium flows between the fin bases and the bridge shape bits 13 as indicated with streamlines 11. When the angle of attach alpha degrees is adequate, the heat transfer medium flows along the thin wing bits 13 without separating therefrom so as to change its flow direction. On the other hand, the heat transfer medium flowing on the fin bases 12 starts to form boundary layers on the fin bases 12. However the heat transfer medium, the flow direction of which is changed, collides with said boundary layers so as to destruct the layers and adhere the main flows flowing from the wing bits 13 to the wall surface of the fin bases 12, resulting in remarkably improving the heat transfer rate at the main flow adhesion parts on the fin bases 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in the fin structure of a fin-tube heat exchanger constructed by attaching a large number of fans to heat exchanger tubes for air conditioning or refrigeration.

Structure of a conventional example and its problems Figure 1 shows a conventional example of a fin-tube heat exchanger used for air conditioning. Such a heat exchanger is composed of aluminum fins 1 and copper tubes 2, and the fins 1 are connected to the copper tubes 2.
A large number of pipes are arranged perpendicular to the pipe, and are crimped or brazed to the copper pipe. A fluorocarbon refrigerant flows inside the copper tube and indirectly exchanges heat with air flowing in the direction of the arrow in the figure via the copper tube 2 and the fins 1.

A plan view of the fin 1 is shown in FIG. This fin has a large number of bridge-shaped cut and raised pieces 5 provided on an aluminum fin substrate 4. Further, the steel pipe to be joined to the fin is inserted into the collar 3 raised from the fin substrate 4.

The shape of the bridge-shaped piece 5 is shown in cross section AA as shown in FIG. A and b in the figure show two types as conventional examples. 4a and 4b are cross sections of the fin substrate corresponding to 4 in FIG. 2, and 5a and 5b are cross sections of the bridge-shaped cut and raised pieces corresponding to 6 in FIG.

FIG. 4 depicts streamlines of air flowing between the fins in order to understand the characteristics of the fins of a conventional fin-tube heat exchanger. 6c and ed are streamlines, 7c and 7cl are cross sections of the fin substrate, and sc and aa are cross sections of bridge-shaped pieces. In such a fin, air entering from the direction of the arrow forms a boundary layer on the surfaces of the fin substrate 70.7d and the bridge-shaped pieces sQ, sd, but the fin surface is cut off before the boundary layer is sufficiently developed. The boundary layer becomes thinner and the heat transfer coefficient between the fins and the air improves.

To improve the heat transfer coefficient between the fins and the air,
There are methods that utilize the leading edge effect of the boundary layer and methods that utilize the effects of turbulence and vortices. Figure 3a shows the former, and b adds the latter to the former to further improve the heat transfer coefficient of a. However, in case b, as seen in Figure 4, flow separation occurs at the rear of the bridge-shaped piece, so not only does the heat transfer coefficient not improve much compared to case a, but also wind noise accompanies the separation. Purpose of the Invention The purpose of the present invention is to eliminate the separation of the heat medium flowing between the fins, change the flow direction of the heat medium, destroy the boundary layer on the fin substrate, The present invention provides a heat exchanger having a fin structure in which the main flow is reattached to the fins and the heat transfer coefficient is improved.

Structure of the Invention In the present invention, a large number of cuts are provided in the fins facing the heat medium flowing between the 1D fins, and the small pieces formed by the cuts are curved to the upper part, straddle the lower part, and form a thin plate shape.
It is raised from the fins and opposed to the heat medium flowing between the fins at an angle of attack of α (0<α<90) degrees.

Description of examples A fin structure according to an embodiment of the present invention is shown in FIG.

After making a notch in the fin substrate 9, a bridge-shaped small piece 10 cut and raised from the fin is made into a thin plate shape, and the line connecting the leading edge and the trailing edge of the small piece, the bow chord, and the flow direction of the heat medium and the angle of attack. The fin is tilted by α degree (0° and α<90°).

FIG. 6 shows a cross-section of the characteristic portions of the fins shown in FIG. 5 stacked together and a heat medium flowing between them. The arrow indicates the flow direction of the thermal fluid, 12 indicates the fin substrate, 13
indicates a thin plate-shaped bridge-shaped piece, and the streamline of the heat medium flowing between them is indicated by 11. The thin plate piece 13 is installed at an angle of attack of α degree (0 < α 9 o) with the fin inflow angle of the heat medium. be done.

If the α degree is appropriate, the heat medium flows along the thin plate pieces 13 without peeling off and changes its flow direction.

On the other hand, the heat medium flowing over the fin substrate 12 begins to form a boundary layer on the fin substrate 12 due to its viscosity;
On the way, it collides with the heat medium whose flow direction has been changed by the airfoil pieces 13, the boundary layer is destroyed, and the main flow flowing from the airfoil pieces 13 adheres to the wall surface of the fin substrate 12. This is the same phenomenon as the so-called fluid redepositing on the heat transfer surface before and after peeling and significantly increasing the heat transfer coefficient, and the heat transfer coefficient of the mainstream adhering portion is significantly improved.

In the embodiment shown in FIG. 5, the fin substrate 9 has a flat plate shape, but the present invention is also effective when the fin substrate 9 has a corrugate shape or a thin plate shape.

6.S. Effects of the Invention According to the present invention, since the flow direction of the heat medium is deflected by the small airfoil, the main flow of the heat medium is reattached to the fin wall, and the heat transfer coefficient is significantly improved. Furthermore, since the cut and raised bridge-shaped pieces have a thin plate shape, peeling is less likely to occur and wind noise generated from the heat exchanger is suppressed.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a conventional fin-tube heat exchanger, Fig. 2 is a plan view of the fins in Fig. 1, and Fig. 3 is a perspective view of a conventional fin-tube heat exchanger.
The figures are Fig. 2, a configuration diagram of a conventional example of a person-to-person cross section, Fig. 4, a streamline diagram of air flowing between fins in the conventional example, Fig. 5, a sectional view of a fin according to an embodiment of the present invention, and Fig. 6. The figure is a flow diagram of a heat medium flowing between fins according to an embodiment of the present invention. 9...Fin board, 10.12...Bridge-shaped cut piece, 11...Streamline.

Claims (1)

[Claims] It is composed of a plurality of heat transfer tubes and a plurality of fins attached to the heat transfer tubes at an angle close to perpendicular to the heat transfer tubes, and a number of cuts are provided in the fins facing the heat medium flowing between the fins. A small piece having a thin wing shape is raised from the fin, and a line connecting the leading edge and the trailing edge of the airfoil flows between the fins in the direction in which the heat medium enters. A heat exchanger placed at an angle to the opposite direction.