JPH0251120B2 - - Google Patents

Description

Detailed Description of the Invention Field of the Invention The present invention relates to a heat exchanger with fins for gas-gas-liquid two-phase fluid (or liquid), which is widely used in evaporators, condensers, etc. in the field of air conditioning equipment. It is something.

Conventional configurations and their problems In recent years, with the reduction in noise from air conditioning equipment, there has been a growing trend to design heat exchangers with front wind speeds of 1 m/sec or less. Improving the performance of the equipment has become an issue.

Conventionally, this type of heat exchanger has a group of flat fins 1 arranged in parallel at regular intervals, as shown in Figure 1a.
It is composed of a heat transfer tube group 2 inserted perpendicularly into the fin group 1, and air flows between the fins in the direction of the arrow to exchange heat with the fluid inside the tubes. As shown in Figure 1b, the thermal fluid characteristics around the heat transfer tube group 2 between the fin groups 1 are as follows: When a low wind speed airflow flows through the heat transfer tubes 2 in the direction of the arrow, the stagnation point (airflow angle θ from the first part of the pipe wall
The flow separates at 70 to 80 degrees, and a dead area 3 shown by diagonal lines is created at the downstream part of the heat transfer tube, so the air side heat transfer coefficient in this dead area 3 decreases significantly, and the heat transfer as a heat exchanger is reduced. It had the disadvantage of low performance.

In addition, as shown in Figure 1c, the thickness of the temperature boundary layer 4 on the heat transfer surface of the fin group 1 increases in proportion to the square root of the distance from the airflow inlet, so the air side heat transfer coefficient The heat transfer performance as a heat exchanger deteriorates significantly as the distance from the air flow inlet increases, and the heat transfer performance as a heat exchanger is low.

Purpose of the Invention The present invention eliminates the above-mentioned conventional drawbacks, and in particular reduces the dead zone downstream of the heat transfer tube and the temperature boundary layer thickness on the heat transfer surface of the fins by using the fin shape.
Moreover, the purpose of this invention is to promote airflow turbulence by the blowout flow, thereby achieving a significant improvement in the air-side heat transfer coefficient, and thereby achieving a smaller size and higher performance of the finned heat exchanger.

Structure of the Invention The heat exchanger with fins of the present invention is composed of flat plate fins arranged in parallel at regular intervals, through which air flows, and heat transfer tubes inserted at right angles to the flat plate fins, through which fluid flows. , I-shaped cut-out portions having a plurality of small holes facing the airflow and louver-shaped cut-out portions having openings at both ends in the airflow direction are alternately provided in the portion of the flat plate fin located between the heat transfer tubes. Furthermore, one of the I-shaped cut-and-raised portions is provided at a rear position at an angle of 90° or more from the stagnation point on the surface of the heat exchanger tube.

With this configuration, first, short fins are lined up in the air flow direction, and a temperature boundary layer is formed on each of these short fins, so that the thickness of the boundary layer becomes thin.

Furthermore, the airflow that has passed through the small holes of the I-shaped cut-and-raised portion and the flow that has passed over the upper part re-adheres to the downstream fins, which promotes airflow turbulence.

Furthermore, even after the airflow around the heat exchanger tube collides with the heat exchanger tube, it is prevented from separating from the heat exchanger tube by the flow passing over the I-shaped cut and raised side surface, so that the dead area downstream of the heat exchanger tube is reduced.

Therefore, the air side heat transfer coefficient is significantly improved, and the finned heat exchanger can be made smaller and have higher performance.

DESCRIPTION OF EMBODIMENTS Hereinafter, a heat exchanger with fins according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a plan view, and FIG. 3 is a sectional view taken along line AA in FIG.

Heat exchanger tubes 7 are inserted into fin collar portions 6 which are barred at regular intervals on the flat plate fins 5. And the direction perpendicular to the airflow flowing in the direction of the arrow,
That is, the fins 5 in the gaps between the heat transfer tubes 7 adjacent in the step direction have I-shaped cut-out portions 8, 9 facing the airflow and openings 10a, 10 at both ends in the airflow direction.
A plurality of louver-shaped cut-and-raised portions 10 and 11 having louver-shaped cut-and-raised portions 11a and 11b are provided, and from the upstream side of the airflow, an I-shaped cut-and-raised portion 8, a louver-shaped cut-and-raised portion 10, an I-shaped cut and raised portion 9. Louver-shaped cut-and-raised parts 11 I-shaped and louver-shaped cut-and-raised parts are arranged alternately in this order. Further, a plurality of small holes 12 are provided in the I-shaped cut-and-raised portions 8 and 9.

Next, the action and effects will be explained.

First, I-shaped cut-out portions 8 and 9 are made on the flat plate fin 5.
By providing the louver-shaped cut-and-raised parts 10 and 11, the tops of the louver-shaped cut-and-rise parts 10 and 11 function as fins parallel to the airflow, and the flat plate fins 5 are arranged in the airflow direction as short fins 5 and louvers. The shaped cut-out parts 10 and 11 are lined up, and,
There must be an I between the louver-shaped cut-out parts 10 and 11.
Since the letter-shaped cut-out portions 8 and 9 are provided, a thin temperature boundary layer is always formed on the short fin 5 and the louver-shaped cut-out portions 10 and 11, respectively. 11 will not be buried in the temperature boundary layer formed in the upstream louvered cut-out portion 10.

In addition, the plurality of small holes 1 of the I-shaped cut-and-raised portions 8 and 9
2 and the flow that passed over the upper part reattached to the louver-shaped cut-out parts 10, 11 and the flat plate fin 5 on the downstream side, thereby promoting airflow turbulence, and moreover, the air flow passed through the plurality of small holes 12. The downstream side heat transfer surfaces of the I-shaped cut-and-raised portions 8 and 9 also become effective due to the blowout flow.

In addition, since the I-shaped cut-out portion 9 is provided at the rear, which is more than 90 degrees from the stagnation point on the surface of the heat exchanger tube, the airflow around the heat exchanger tube 7 collides with the heat exchanger tube 7 inserted into the fin collar portion 6. Rear I-shaped cut-out part 9
It is possible to prevent separation from the heat exchanger tube 7 due to the flow over the side surface 9a of the I-shaped raised portion 9 due to the damming effect, and it also enters the rear region of the heat exchanger tube 7, reducing dead areas.

From the above, the air-side heat transfer coefficient is significantly improved, and the finned heat exchanger can be made smaller and have higher performance.

Effects of the Invention As described above, the heat exchanger with fins of the present invention has flat plate fins arranged in parallel at regular intervals and through which air flows, and a heat exchanger inserted at right angles to the flat plate fins through which fluid flows. I-shaped cut-out portions having a plurality of small holes facing the airflow and louver-shaped cut-out portions having openings at both ends in the airflow direction are alternately provided on the flat plate fins between the heat transfer tubes. As a result, short fins are lined up in the airflow direction, and since there is an I-shaped cut-out between the louver-shaped cut-outs, there is always a thin temperature boundary layer around these short fins. is formed.

The blowout flow that passes through the plurality of small holes in the I-shaped cut-and-raised portion and the flow that passes over the upper portion reattach to the downstream louver-shaped cut-and-raised portion and the flat plate fin, thereby promoting airflow turbulence.

The airflow around the heat exchanger tubes is controlled by an I installed at the rear of the heat exchanger tubes.
It is possible to prevent separation from the heat exchanger tube due to side flow caused by the damming effect of the cut-and-raised portion, and the dead area is reduced.

As a result of the above, the air side heat transfer rate is significantly improved, and the finned heat exchanger can be made smaller and have higher performance.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional heat exchanger with fins, FIG. 2 is a front view of a heat exchanger with fins according to an embodiment of the present invention, and FIG. 3 is a sectional view taken along line A-A in FIG. . 5... Flat plate fin, 7... Heat exchanger tube, 8, 9...
I-shaped cut-and-raised portion, 10, 11...louver-shaped cut-and-raised portion, 12...small hole.

Claims (1)

[Claims] 1 Consisting of flat plate fins arranged in parallel at regular intervals, through which air flows, and heat transfer tubes inserted at right angles to the flat plate fins, through which fluid flows, and located between the heat transfer tubes of the flat plate fins. I-shaped cut-out portions having a plurality of small holes facing the airflow and louver-shaped cut-out portions having openings at both ends in the airflow direction are alternately provided in the portion, and one of the I-shaped cut-out portions is provided. is from the stagnation point on the surface of the heat exchanger tube.
Heat exchanger with fins installed at the rear with an angle of 90° or more.