JPH05149687A - Heat transfer fins for plate fin type heat exchanger and its forming method - Google Patents

Abstract

PURPOSE:To improve a mean coefficient of heat transfer by a method wherein many slits are punched in a heat transfer plate so as to form fine heat transfer pieces and the heat transfer pieces are regularly inclined toward alternative right and left sides, respectively. CONSTITUTION:Heat transfer fins 3, 3... are constructed such that one heat transfer plate 2 is formed with some rows of slits 7 punched therein. Namely, each of the slits 7 is formed in a direction perpendicular to a flowing direction of the fluid. The heat transfer plate 2 is reversed in either a U-shape or a U-shape at each of the rows of slits 7 through a pressing work and bent to form an approximate corrugated step shape. Then, one of the many adjacent pieces in the slits 7 is used as one raised fin piece 3b, its subsequent stage piece is used as a right slant piece 3b inclined rightwardly and further subsequent piece and a still further piece is used as a left slant fin 3c inclined leftwardly. In this way, the two pieces are set as one set and this operation is repeated in sequence to form the heat transfer fins 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer fin for a plate fin type heat exchanger and a method for forming the heat transfer fin.

[0002]

2. Description of the Related Art In a plate fin type heat exchanger, generally, a large number of heat transfer plates are stacked, and heat transfer fins are alternately projected from upper and lower heat transfer plates in a space between them. There are various structures of heat transfer fins. Among them, the most basic plain type fin is formed by pressing one heat transfer plate material so that the U shape is repeatedly inverted, and A heat transfer fin, which forms a linear flow path and exhibits flow characteristics similar to a circular pipe.

In the case of the plane type fin, the flow of the fluid as the heat medium becomes a laminar flow with no obstacles. Therefore, as shown in the graph on the left side of FIG. A thermal boundary layer develops with different velocities and temperatures. Then, the heat transfer efficiency is governed by the thickness δ of the temperature boundary layer as follows.

Since the boundary layer thickness δ increases in proportion to the 1/2 power of the distance from the start point of the heat transfer fin when the flow is laminar, the average heat transfer coefficient hm is It decreases in inverse proportion to the square root of the surface length L. Therefore, the fin length L
Is smaller, the average heat transfer coefficient hm is larger. The multi-entry fins positively utilized this property. In other words, the multi-entry fins average the heat transfer coefficient at a high position by repeating the starting point of the flow forming the fluidized bed to make it continuous. Further, corrugated fins, louver-shaped fins, perforated plate-shaped fins, etc. also show similar characteristics.

The conventional multi-entry fin is shown in FIG.
As shown in Fig. 5, the heat transfer plate material is pressed with a mold to form heat transfer fins in a U shape, and convex and concave walls are alternately formed on the side surface. Is repeated. Therefore, since the flow of the fluid is disturbed by the unevenness, the velocity is suppressed and the boundary layer of temperature is sheared.

[0006]

Since the conventional multi-entry fin has unevenness on the side surface as described above,
It requires a very complicated mold, and it is unavoidable that the manufacturing cost of the mold is high, and the side surface of the heat transfer fin is close to vertical, so the direction of fluid flow disturbance is disturbed. Was two-dimensional in the horizontal direction, and the fluid flow did not exchange much at the top and bottom, and there was room for improvement in this respect.

The present invention has been made in view of the above circumstances.
Plate fin type that has characteristics similar to multi-entry fins, but is easy to design and manufacture, and has a good average heat transfer coefficient because the disturbance direction of the fluid flow is three-dimensional. It is an object of the present invention to provide a heat transfer fin for a heat exchanger and a method for forming the heat transfer fin.

[0008]

In order to achieve the above-mentioned object, the plate fin type heat exchanger of the present invention is a heat transfer fin which is alternately projected from upper and lower heat transfer plates.
It is characterized in that it is subdivided into a large number of heat transfer fin pieces by slits, and that all or most of the heat transfer fin pieces are regularly inclined alternately left and right.

According to the method of forming heat transfer fins of the present invention, a heat transfer plate material for forming fins which is fixed to the heat transfer plate is formed with slit rows in the flow direction of the fluid so that the slits are at right angles. Is reversed in each slit row and bent into a corrugated shape, and a part or most of the pieces divided by the slits are regularly inclined alternately to the left and right.

[0010]

Since the heat transfer fins for the plate fin type heat exchanger are configured as described above, when the fluid flows in the flow path between the heat transfer fins, the temperature boundary layer is sheared by each of the subdivided heat transfer fin pieces. Therefore, the starting point of the temperature boundary layer can be created for each heat transfer fin (see the graph on the right side of the figure), so to speak, the louvers that receive the flow are shifted in three stages (or two stages), and the louvers in the previous stage Since the influence is reduced, a very high heat transfer coefficient is obtained, and the characteristics are similar to those of a multi-entry fin. Moreover, since the shearing of the temperature boundary layer is performed obliquely and the disturbance becomes three-dimensional, the average heat transfer coefficient hm
Are held in a high position on average over the entire length of the fluid flow path.

Comparing this with the conventional multi-entry fin, not only the position of the starting point of the boundary layer was shifted, but also the boundary layer shearing generated by the heat transfer fins in the preceding stage was caused because the angle was given. The heat transfer fins at the latter stage effectively operate. In the experiment, for regular plain fins, 1
It was confirmed that the heat transfer efficiency was improved by 5 to 20%.

In the heat transfer fin, the heat transfer fin is erected,
When tilted to the right or left, the obstacle area of the fluid increases and the average heat transfer coefficient can be improved, but in some cases, the pressure loss becomes excessive. When the restriction on the pressure loss is severe, the heat transfer fin can be inclined rightward and leftward only in two steps, so that the pressure loss can be reduced in exchange for a slight decrease in heat transfer efficiency. ..

The heat transfer fins need not be entirely inclined with respect to one heat transfer plate, but can be partially inclined depending on the situation. Further, since the distance between the heat transfer fins can be changed by the width of the slit, it is possible to easily change the substantial fin length of the heat transfer fins.
The required performance (heat exchange capacity, pressure loss) can be carefully handled in design and manufacturing.

By the way, in the case of a plate fin type heat exchanger, it is often designed as a heat exchanger for three or more fluids, and it is necessary to balance the heat between the fluids.
In such a case, according to the present invention, based on the plain fin type, it is possible to partially perform multi-entry fin processing or partially change the length of the fins, so that it is possible to give a width to the design. It becomes possible, and the manufacturing cost becomes low in that respect.

Further, according to the method for forming the heat transfer fins, in addition to the same operation as described above in manufacturing, the heat transfer plate material is preliminarily slit-processed and then formed into a corrugated shape by a press, and a simple work is performed. Since the heat transfer fins can be formed by inclining, the cost can be reduced because a complicated die unlike the conventional multi-entry fins is not required.

[0016]

Embodiments of the present invention will now be described with reference to the drawings. 1 to 4 show an embodiment, in which a heat exchanger includes a plurality of heat transfer fins 3, 3, ... Which are alternately arranged in a space between a plurality of heat transfer plates 1, 1 ,. Is provided, and its space is the fluid flow path 5, and the heat transfer fins 3,
3, ... The whole is molded by one heat transfer plate member 2.

As for the manufacturing process, one heat transfer plate member 2 is provided with slits 7, 7, ... In multiple rows (FIG. 4), and each slit 7 is formed in a direction perpendicular to the fluid flow direction. To do. Next, in each row, the heat transfer plate material 2 is inverted and bent into a U-shape (or a U-shape) by pressing, and is formed into a generally corrugated step. In this state, since the adjacent pieces stand by the slits 7 in each row,
Bending is performed using a die or one by one.

Regarding the bending process, one of the many pieces adjacent to each other by the slit 7 is left as it is and the standing fin piece 3 is formed.
a, and the next stage piece is inclined to the right and the right inclined fin piece 3b is formed.
Each of the heat transfer fins 3 is formed by inclining the next stage piece to the left to form a left inclined fin piece 3c, and repeating this in sequence.

In each heat transfer fin 3, the fins are arranged in the same row in a row. By doing so, bending can be easily performed. However, the rows may be alternately inclined, or the standing fins, the right inclined fins, and the left inclined fins may be arranged in this order.

FIG. 5 shows another embodiment. In this case, each heat transfer fin 3 is constituted by alternating right slant fin pieces 3b and left slant fin pieces 3c.

The inclination of the heat transfer fins to the left and right does not have to be completely regular, but may be approximately regular according to various requirements.

[0022]

As described above, according to the present invention, the following effects are remarkably exhibited. 1) When a fluid flows in the flow path between the heat transfer fins, the temperature boundary layer is sheared by each of the subdivided heat transfer fin pieces, and thus exhibits characteristics similar to those of a multi-entry fin.
Moreover, since the shearing of the temperature boundary layer is made oblique and the disturbance becomes three-dimensional, the average heat transfer coefficient is kept at a high position on average over the entire length of the fluid flow path, and the heat transfer efficiency is very good. ..

2) The size of the cross-sectional area occupied by the heat transfer fins can be easily changed at the designing and manufacturing stages by selecting each of the right tilting, left tilting, and standing modes of the heat transfer fins. Since it is possible to easily change the length of the fins with the width of the slit, it is possible to make detailed correspondences to the required performance (heat exchange capacity, pressure loss) in design and manufacturing.

3) Based on the plain type fin type, partly multi-entry fin processing,
Since the length of the fin can be partially changed, it is possible to give a width to the design, and the manufacturing cost is reduced in that respect.

4) In particular, according to the method for forming the heat transfer fin, the cost can be reduced because a complicated die unlike the conventional multi-entry fin is not required.

[Brief description of drawings]

FIG. 1 is a perspective view showing a plate fin type heat transfer fin for a heat exchanger according to an embodiment of the present invention in a protruding state from a heat transfer plate.

FIG. 2 is a partial cross-sectional view of the plate fin type heat exchanger according to the same embodiment.

FIG. 3 is an explanatory view of a state of arrangement of heat transfer fin pieces as seen from a plane.

FIG. 4 is a plan view of the heat transfer plate material showing a part of the manufacturing process.

FIG. 5 is a sectional view corresponding to FIG. 2 showing another embodiment.

FIG. 6 is a graph for explaining multi-entry fin characteristics in comparison with plain fins.

FIG. 7 is a perspective view of a conventional multi-entry fin.

[Explanation of symbols]

 1 Heat Transfer Plate 2 Heat Transfer Plate Material 3 Heat Transfer Fins 3a, 3b, 3c Heat Transfer Fin Piece 7 Slit

Claims (2)

[Claims] 1. A heat transfer fin, which is alternately projected from upper and lower heat transfer plates, is subdivided into a large number of heat transfer fin pieces by slits, and all or most of the heat transfer fin pieces are regularly inclined right and left alternately. A heat transfer fin for a plate fin type heat exchanger characterized by being made. 2. A heat transfer plate material for forming fins fixed to a heat transfer plate, wherein slit rows in the direction of fluid flow are formed so that the slits are at right angles, and the heat transfer plate material is inverted at each slit row to form a wave stage. A method for forming heat transfer fins for a plate fin type heat exchanger, which comprises bending a part of the piece divided by slits and alternately inclining the part or most of the pieces divided by slits in a regular alternating manner.