JPS63183390A - Louver fin with slit - Google Patents

Abstract

PURPOSE:To improve heat transfer properties and pressure loss properties, by providing a slit in the center of each inclined plate disposed in a row to constitute a rouver. CONSTITUTION:The louver 1 in a front position is composed by disposing back ward inclined plates 2 in a row at predetermined intervals, and the rouver 3 in a rear position is composed by disposing forward inclined plates 4 in a row in the sale manner. The front and the rear ends of a return plate 5 provided in the middle of both louvers 1 and 3 are bent in accordance with the inclination of inclined plates 2 and 4. The rear end of a front plate 6 is also bent in the same manner. A slit 7 or a hole is provided in the center of each inclined plate 2 or 4. In regard to two neighboring inclined plates 2 of a louver 1, a thermal refrigerant fluid flows from the front side of the upstream part 2a of an inclined plate to the back side of its downstream part 2b, passing through the slit 7 as shown by arrow signs B when the width 'ls' of a slit 7 to the width 'lf' of an inclined plate 2 as viewed from the cross sectional view is determined as 3/16 lf for example.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvements in heat transfer fins provided in heat exchangers.

(Prior Art) Heat transfer is promoted in a heat exchanger by providing plate-shaped fins that protrude into the flow of heat/coolant. Plate fins usually have their plate surfaces parallel to the flow to reduce pressure loss. Figure 5 shows the local heat transfer coefficient of the plate fin [a] in the direction perpendicular to the plate surface, and the flow (b)
The heat transfer coefficient line (c
It becomes l. This is because the thickness of the boundary layer of the flow along the plate surface increases in the wake direction. As shown in Figure 6, a slit (DL or hole is provided in the middle of the plate for pre-play)
(aρ) and the rear plate (a,), and divide the boundary force so that a leading edge effect occurs, the heat transfer coefficient line (c,
) The overall heat transfer is improved as (c =).

The problems in this case are that (i) an effective leading edge effect cannot be obtained if it reaches the wake of the front plate or the rear plate, and (50 slits reduce the heat transfer area. Regarding (i) Quantitative analysis is still being carried out as a countermeasure. (As a countermeasure for 10, it is known to arrange the fins as shown in FIG. 7 or 8.

In each figure, the local heat transfer coefficient is also shown in the direction perpendicular to the plate surface.

Figure 7 shows a staggered fin in which the heat transfer characteristics are increased by arranging the plays (a,) at different levels. 8th
The figure shows a sloping play in which cut-and-raised cuts are made on the board using louver fins) (
If a,) are arranged in a row to form a louver, even greater heat transfer characteristics can be obtained as a whole.

(Problems to be Solved by the Invention) The present invention focuses on the fact that louver fins have a structure that tends to increase pressure loss, and improves the structure to further improve its heat transfer characteristics and improve pressure loss characteristics. The purpose is to

(Means, functions, and embodiments for solving the problem) In order to achieve the above object, the present invention provides louver fins in which a slit or a hole is provided in the center of the inclined plates that are arranged at intervals and constitute the louver. shall be.

That is, the louver fin with slits of the present invention is characterized in that each of the arrayed inclined plates constituting the louver is provided with a hole in the center. In this case, the width of the slit seen from the cross section is equal to the width of the inclined plate. It is preferable to set it to 115 or less.

A hole is also provided in the center of the folded plate at the middle position of the louver, which is made up of the front and rear inclined plates, to improve the flow to the rear louver.

1 shows a sectional view of one embodiment of the louver fin with slits of the present invention. The front louver (1) of this louver fin is constructed by arranging inclined plates (2) in a backward-tilting position at regular intervals, and the rear louver (3) is also made up of inclined plates (2) in a forward-tilting position. (4) are arranged in a row. The folding plate (5) at the intermediate position between the two louvers (1) +3) has its front and rear ends bent to match the slopes of the louvers (2) and (4). The rear end of the front plate (6) is similarly bent.

Each inclined play) +2) +4) shall have a slit (7) or hole in its central part. Figure 2 shows the louver (1)
Two adjacent inclined plates (2) are shown, and the width Ig of the slit (7) is set to +If with respect to the width If of the inclined plate (2) seen from the cross section. The heat/coolant fluid flows from the front side of the upstream part (2a) of the inclined plate to the slit (
7) Flows through the downstream portion (2b) to the rear side.

Figure 3 shows the local heat transfer coefficient of the embodiment of the present invention on the vertical axis and the width of the inclined plate (2) on the horizontal axis. Figure 4 shows the heat transfer coefficient line (cl). The figure shows the local heat transfer coefficient without slits.In the present invention, the heat transfer per unit length is improved by about 15 cm compared to without slits.Even considering the reduction in heat transfer area due to slits, In comparison, an improvement in heat transfer characteristics of about 5 inches was obtained.

In terms of pressure loss, the overall system without slits was 5-5.
decreased. Therefore, the pressure loss characteristics are improved by about 5 inches as well as the heat transfer characteristics.

There is also a slit (8) in the center of the folding plate (5).
Alternatively, holes can be provided.

(Effects of the Invention) As described above, when the slits are provided in the inclined plate according to the present invention, the boundary layer on the plate is divided, and in this case, a flow field is formed across the slits, so that the influence of the wake is reduced. The leading edge effect is less effective, which together provides the favorable result of improved heat transfer and reduced pressure drop. In the example, both heat transfer characteristics and pressure loss characteristics were improved by about 5 cm compared to the conventional technology without slits.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view in the flow direction of one embodiment of the louver fin with slits of the present invention, Fig. 2 is a longitudinal cross-sectional view showing the relationship between two adjacent inclined plates, and Fig. 5 is a horizontal cross-sectional view of the inclined plates. A heat transfer coefficient distribution diagram of an inclined plate according to an embodiment of the present invention, with the local heat transfer coefficient plotted on the width and vertical axes. FIG. 4 is a heat transfer coefficient distribution diagram without slits for comparison. FIG. 5 is a heat transfer coefficient distribution diagram of a conventional conventional plate fin, FIG. 6 is a heat transfer coefficient distribution diagram of a conventional plate fin with slits, and FIG. 7 is a cross-sectional diagram of a conventional staggered fin.
FIG. 8 is a sectional view of a conventional louver fin. (1) (3) - Louver, (2) [4)... Inclined plate, (2a)... Upstream section, (2b)... Downstream section,
(5)...Folding plate, (6)...Front plate, (
7) (8)...slit, hole, (lf)...inclined plate width, (la)...slit width, exit...flow, (a
l (a,) (a, Xa, Xaρ... plate, (b)
...flow, (cl (c) (c) ... heat transfer coefficient line,
(dl・-slit.

Claims (3)

[Claims] (1) A louver fin with slits, characterized in that each of the rows of inclined plates forming the louver has a hole in the center. (2) The louver fin with slits according to claim 1, wherein a hole is provided in the center of the folded plate at an intermediate position between the front and rear louvers, which are made up of parallel inclined plates. (3) The louver fin with slits according to claim 1, wherein the width of the hole in the cross section is 1/3 or less of the width of the inclined plate.