JPH01107096A - Finned heat exchanger - Google Patents

Abstract

PURPOSE:To improve the heat transfer performance by setting the pitch-of-row and pitch-of-level of heat transmission pipes in specific relations relative to the outer diameter of a heat transmission pipe, arranging the pipes in a staggered form, and corrugating the fins spanning between the pipes. CONSTITUTION:The pitch-of-row L1 in the air flow direction of heat transmission pipes having the outer diameter D0 (3mm<=D0<=7.5mm) is set 1.2D0<=L1<=1.8D0, and the pitch-of-level L2 in the air flow direction is set 2.6D0<=L2<=3.7D0. As the incoming air shown by arrow 3 passes through the space between the heat transmission pipes 9a in the inlet side first row, the air is separated from behind the peak 8 of the corrugation, creating turbulences which improves the air side localized heat transfer rate, and, after the air flow again contacts the fin surface, it follows the fin contour. By a staggered arrangement of the pipes, the downstream side heat transmission pipes 9b cancel the dead spaces behind the upstream side heat transmission pipes 9a. By this compound effect, the heat transfer performance of the fins can be improved, and a fin and tube type heat exchanger can be provided which has a high heat transfer rate on the air side, has less draft resistance and is not susceptible to frost growth.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a heat exchanger used in air conditioners, refrigerators, etc., for transferring heat between a refrigerant and a fluid such as air.

BACKGROUND OF THE INVENTION A conventional fin-tube heat exchanger of this type consists of a group of plate-like fins 1 arranged in parallel at regular intervals, and a group of plate-like fins arranged perpendicularly to the group of plate-like fins 1, as shown in the perspective view of FIG. The airflow 3 flows between the plate-shaped fin groups 1 and exchanges heat with the refrigerant flowing inside the heat exchanger tube group 2.

In recent years, such fin-tube heat exchangers have been required to be smaller and have higher performance, but the airflow velocity between the fins is kept low from the viewpoint of noise etc., so the thermal resistance inside the heat exchanger tubes is reduced. In comparison, the thermal resistance on the air side is high.

Therefore, efforts are currently being made to reduce the difference in thermal resistance from the inside of the heat transfer tube by expanding the heat transfer area on the air side.

However, there are physical limits to enlarging the heat transfer surface, and there are also problems in terms of economy and space saving. This is an important issue in type heat exchangers.

FIGS. 6 to 9 show an example of a conventional fin-tube heat exchanger. 6 and 8 show partial side views. Figures 7 and 9 are E-E' cross-sectional views, respectively.
An F-F' cross-sectional view is shown.

The conventional examples shown in FIGS. 6 and 7 are called flat fins with a staggered tube arrangement, and the pitch L1' of the tube rows in the three directions of the airflow of the heat exchanger tubes 2 is set by the outer diameter D'o (Db −=
10trtm), and the tube stage pitch L'2 in the direction perpendicular to the airflow 3 is set to 2.2 times the outer diameter D'o of the heat transfer tubes 2.
．． It is set at about 2 to 2.5 times.

Furthermore, the conventional examples shown in FIGS. 8 and 9 are called slit fins, and are based on the above-mentioned flat fins, and have a large number of slit-shaped cuts 5a to 5a between the heat transfer tubes 2 of the plate-like fins 1. 5d. In addition, plate-shaped fin 1
The heat exchanger tube 2 is penetrated through the fin collar 4 provided integrally.

Problems to be Solved by the Invention However, although the flat fins having the above configuration have low ventilation resistance and are effective in preventing frost formation when used as an evaporator, the heat transfer coefficient on the air side is low. This is because the outer diameter D'o of the heat exchanger tube 2 is large, and the dead zone 6 that occurs downstream thereof is correspondingly large, and the temperature boundary layer generated from the leading edge end face of the fin is thick and draws the trailing edge end face travel. The thermal resistance on the air side is high.

Also, regarding slit fins based on this,
The large number of cuts and raised portions 5a to 5d destroys the thick temperature boundary layer that occurs during the 7-rat fin and creates a thin temperature boundary layer, so that the heat transfer performance at the cut and raised portions is good. Therefore, the heat transfer coefficient on the air side is significantly higher than that of flat fins.

However, on the other hand, the ventilation resistance becomes high, and the distance between the fins decreases due to the provision of the slits, which accelerates frost formation.

Therefore, in view of the above problems, the present invention improves the heat transfer performance of the fin part due to the turbulent flow effect and significantly reduces the dead area by adding innovations to the fin shape, tube arrangement, and tube diameter. The present invention provides a fin-tube heat exchanger that has a high heat transfer coefficient on the air side, low ventilation resistance, and is less likely to cause frosting.

Means for Solving the Problems In order to solve the above problems, the fin-tube heat exchanger of the present invention includes a plurality of flat fins arranged in parallel at regular intervals and through which gas flows; Outer diameter Do (3 degrees < Do <
75 mm), and the tube array pitch L1 in the airflow direction of this heat exchanger tube group is set to 1-2 Do (L
1 (1,8Do, airflow and vertical pipe pitch L2
・2.6 Do < 12 (3,7D.

In addition, the fins between the heat exchanger tube groups in this flat plate fin are formed in a wave shape, and each heat exchanger tube group is configured such that the heat exchanger tubes are staggered from each other.

For production The effects of this technical means are as follows.

When airflow passes through the wave-shaped fins, turbulence is generated in the wake of the fins, increasing the local heat transfer coefficient on the air side.

In addition, the dead area itself is reduced by the turbulence flowing into the dead area at the rear of the heat transfer tube. Regarding this dead area,
Since the absolute amount is smaller than in the conventional case of D'o*10 mm, in combination with the above-mentioned turbulent flow effect, the heat transfer performance is significantly improved.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

Components that are the same as those in the conventional example are designated by the same reference numerals, and description thereof will be omitted.

1 to 3 are a plan view of a main part, a sectional view taken along the line AN, and a sectional view taken along the line B, showing an embodiment of the present invention.

In the figure, when the airflow flowing in from the direction of the arrow 3 passes through the gap between the heat transfer tubes 9a in the first row on the airflow side, turbulence occurs behind the wave-shaped peaks, improving the local heat transfer coefficient on the air side. Furthermore, the dead area behind the heat exchanger tubes 9a is reduced by the heat exchanger tubes 9b in the second row on the airflow side. This process is repeated one after another, and the liquid flows out in the direction of arrow 3'. At this time, the state of the flow and heat transfer in the 7 beni I system was such that, as shown in the diagram, separation occurred behind the wave-shaped peak 8, the flow was disturbed, and the airflow reattached to the fin surface. It begins to flow along the rear fin. In addition, the flow at No. 7 is stagnant and has become a dead area.

As shown in Figure 4, it can be seen that the local heat transfer coefficient of air increases rapidly behind the mountaintop 8.In addition, by using a staggered arrangement, the heat transfer tubes on the downstream side are connected to the heat transfer tubes on the upstream side. It has the effect of reducing the dead area of the heat tube, and as a combined effect of these, the heat transfer state on the air side is dramatically improved.

Effects of the Invention As described above, if the fin shape and tube arrangement of the present invention are used, the heat transfer performance of the fin section will be improved due to the turbulent flow effect, and the dead area will be significantly reduced, and the heat transfer coefficient on the air side will be improved. high,
Moreover, it is possible to obtain a fin-tube heat exchanger that has low ventilation resistance and is also resistant to frost formation.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the main parts of a finned heat exchanger showing an embodiment of the present invention, FIG. 2 is a sectional view of the main parts taken along line AA' in FIG. 1, and FIG. Main part sectional view taken along B-B' line,
Fig. 4 is an explanatory diagram for explaining the local heat transfer coefficient, Fig. 5 is an overall perspective view of a finned heat exchanger, and Fig. 6 is a plan view of essential parts of a finned heat exchanger showing the first conventional example. , FIG. 7 is a sectional view of the main part taken along the line E-E' in FIG. 6, FIG. 8 is a plan view of the main part of the finned heat exchanger showing the second conventional example, and FIG. It is a sectional view of the main part taken along the line F-F'. 1... Plate fin, 2... Heat exchanger tube, 3
．． 3'......' flow, 4.10--Fin collar, 5a to 5d......Slit cutting and raising, 6.
...Dead area, 7...Dead area, 8...
...Mountain top, 9a to 9d...Heat transfer tubes. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
--Plate fin 3.3'-m-airflow 8-J,, 7i section ri'a-9d -m-transfer M pipe IO-fin collar Fig. 1 Chief fin collar Fig. 3 Fig. 4 Fig. 5 Figure 6 tr' Figure 8

Claims (1)

[Claims] A plurality of flat plate fins arranged in parallel at regular intervals, through which gas flows, and a plurality of heat transfer tube groups having an outer diameter Do (3 mm≦Do≦7.5 mm) through which fluid flows through the flat plate fins. The tube row pitch L_1 in the airflow direction of the heat transfer tubes is 1.2Do≦L_1≦1.8Do, and the tube row pitch L_2 in the airflow and vertical direction is 2.6Do≦
L_2≦3.7Do, and further, the fins between the heat exchanger tube groups in the flat plate fins are formed in a wave shape, and each of the heat exchanger tube groups is arranged in a staggered manner. Heat exchanger with arrayed fins.