JPS59215596A - Heat exchanger - Google Patents

Abstract

PURPOSE:To provide a heat exchanger of which heat transmitting rate is very high, by introducing air flow smoothly by sufficiently utilizing the front edge effect of fins, by arranging each strip in such a manner that the growing direction of boundary layer of each strip is not in presence on the same plane. CONSTITUTION:A plurality of insertion ports 2 for heat transfer pipes are provided to a fin base plate 1, and cutouts of arbitrary length are provided at right angles with the direction of a step in the middle of both insertion ports 2 in the direction of a step. The cutouts are raised to form a shape having the sectional form as shown in the figure. In the sectional view of fins, a plane strip as a fin base plate 1, a raised strip 3, and a fin base plate 1j running with the raised strip 3 are arranged in the direction of air flow. When fins constituted in such a manner is laminated in layer, the strip 3 forms waved flow paths having a plurality of bending parts with the same part of another fin which is juxtaposed with the strip 3. The air flow passing through the waved flow paths repeats changing of flow directions plurality of times. Accordingly the heat transmitting rate of a heat exchanger can be increased by the repeated effect of approach run which makes the boundary layers of fins thin as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a great fin cheep heat exchanger used in air conditioning, refrigeration equipment, etc.

In the heat exchanger, several heat transfer tubes pass through a plurality of fins arranged in parallel at right angles, and are brought into close contact with the fins by means such as tube expansion. A primary fluid such as cold/hot water or refrigerant is passed through the heat transfer tube.

A secondary fluid such as air is passed between the fins to exchange heat between the two fluids.

At this time, the airflow flowing between the fins includes:
A boundary layer of flow is generated, and the temperature gradient within the boundary layer is extremely large. In other words, the boundary layer becomes a large thermal resistance. This boundary layer develops thickly in the direction of flow of the secondary fluid, resulting in significantly reduced heat transfer downstream of the fins. As described above, the biggest problem with the great fin-chive heat exchanger is that the heat transfer coefficient on the secondary fluid side (fin side) is low.

In order to improve the heat transfer coefficient on this fin side.

It is effective to prevent the formation and development of the boundary layer described above, and various improvements regarding the processed shape on the fin surface have been proposed.

These suggestions for improvement are bold 2:a,! It can be divided into 2. One is that by forming four convex portions on the 9,747 plane of the 9-folded fin surface, the air flow path created when the fins are stacked is enlarged, the air flow path changes direction, etc., and the run-up section (as mentioned above) There are some types of fins that aim at repeating the thin part of the boundary layer (7 effects), with corrugated fins and trapezoidal fins being typical examples. It aims to improve heat transfer by cutting the layer into pieces and eliminating the thick part of the boundary layer, making use of the so-called leading edge effect.In recent years, the latter method has mainly become popular because it provides a relatively high heat transfer coefficient. It's becoming a target.

For example, the first conventional example shown in FIGS. 1 and 2 has a flat fin base (11) having a tube insertion port (2) with a large number of cuts perpendicular to the direction of the pipe stage of the tube insertion port (2). When the fin base (11) is laminated, a group of small strips (3) are As a result, they are arranged in a parallel array.

In a heat exchanger configured in this way.

The heat transfer coefficient on the fin side is improved because the small strips break up the boundary layer of the airflow and prevent its formation and development.

However, since there are many strips (3) on the same plane parallel to the flow direction and they are close to each other, the influence of the boundary stratification formed by the strips (3) on the upstream side is absorbed by the strips on the downstream side. ) There are problems with the strength of the fins because the IJ tubes are affected, the leading edge effect of the individual strips is not fully exploited, and the fins are made up of a collection of small strips.

Another example is the Utility Model 56-5 shown in Figures 6 and 7.
There is one disclosed by No. 8184. In the second conventional example shown in this figure, the strip (3) is attached to the fin base (1).
It is tilted with the surface as the axis. This conventional example does not have the same problems as the conventional example if you consider one fin, but
When fins are stacked at a pitch of several millimeters, as in the case of actual use as a heat exchanger, the main flow direction bends along the inclination of the strip.
8) and S) The positional relationship of the IJ knob (3b).

They exist in the same plane parallel to the flow direction, and the leading edge effect of the strip (3) is not fully utilized, as in the first conventional example. Also, in this example, if the fin stacking pitch is reduced, the strip spacing of adjacent fins becomes smaller, and most of the leading edge effect of strip (3) is lost, so the fin stacking pinch There is also the problem of restrictions.

In order to improve these shortcomings,
75 has been proposed. This invention, shown as conventional example 3 in Figs. 3 and 4, is based on the first
The conventional example shown in FIG.
That is.

In the explanation of the above-mentioned Publication of Publication, 1983-35575, the Ministry of Specification states, ``By providing the strips at an angle with respect to the airflow direction, the IJ strips can be lined up at positions different from the direction of boundary layer development. At the same time, we created turbulence in the airflow to improve heat transfer."

In this third conventional example, as described in the specification of the above-mentioned Japanese Utility Model Publication No. 52-45575, in order to fully utilize the leading edge effect, the strip (3) is attached to the fin base (1). The idea is to avoid placing other strips in the direction of boundary layer development.

However, this third conventional example lacks consideration to the flow direction of the mainstream. This point is shown in the fifth section, which schematically shows the flow direction.
This will be explained with a diagram. in this case.

The main direction of the air flow does not flow obediently along the inclined strip as in the conventional example 2 shown in FIG. This point can be easily observed by airflow visualization experiments. In other words, the fifth
As shown in the figure, since the parallel strips (3c) and the inclined strips (3d) are mixed alternately, the main stream is neatly arranged as shown in Fig. 7 of the conventional example (2) in which the inclined strips are arranged in an orderly manner. , resulting in flow separation in the wake of the inclined strip (3d), as shown in FIG. When separation occurs, the flow velocity near the strip in that area is almost zero, so the heat transfer in that area becomes very small, and conversely, the wind pressure loss increases greatly. be. The specification of Conventional Example 3 also recognizes this point, and states that [turbulence occurs in the airflow] as mentioned above. However, when used in a laminar flow region such as in an air conditioner, it is undesirable to cause turbulence (actually separation) as described above.

Another conventional example is disclosed in Japanese Utility Model Application Laid-Open No. 56-144988, and a fourth conventional example is shown in FIGS. 8 and 9. As for a similar idea.

JP-A-55-105194, JP-A-57-18199
5, etc., and these are considered to be roughly the same.

These fourth conventional examples can be regarded as the third conventional example, in which both ends of the inclined strip (3) in FIG. It can also be said that it is divided. It goes without saying that the purpose of the fourth conventional example is to improve the drawbacks of the second conventional example described above. However, this proposal also
As shown in Fig. 9, in (3e) and (3f) of the χ-shaped strip (3) installed,
e) The boundary stratification velocity formed by

This affects the strip (3f), and the leading edge effect of the strip on the downstream side is not fully utilized, and according to the experiments described later, the heat transfer coefficient is also lower than that of the second conventional example. Furthermore, there are disadvantages in that the wind pressure loss is large, the blowing power is stationary, and the noise is increased.

The present invention was developed to eliminate the following drawbacks, and includes plate fins with multiple rows of slat layers;
In a plate-fin-tube heat exchanger, which is composed of heat exchanger tubes that penetrate through these fins and are held in close contact with them, in which the refrigerant in the heat exchanger tube and the air passing between the fins exchange heat.

A single piece (strip) is cut and raised in the direction perpendicular to the flow direction of the air passing between the fins, and one piece (strip) is cut and raised in the fin part between adjacent heat transfer fins in the longitudinal direction of the fins. The heat exchanger is formed into a λ-shaped shape with a chevron in the center, and a flat plate is provided between adjacent cut and raised parts in parallel to the air flow. .

An embodiment of the present invention will be described below with reference to the drawings. Figure 1O is a fin plan view of a plate fin and cheap heat exchanger showing an embodiment of the present invention, in which a plurality of heat exchanger tube insertion ports (2) are provided in the fin board (1), and each of the insertion ports (2) is A cut of an appropriate length is made between the step directions at right angles to the step direction, and this cut is opened and raised in a λ shape to form a cross-sectional shape as shown in FIG.

FIG. 11 will be explained. FIG. 11 is a sectional view when two fins are laminated. As mentioned above, the fin cross section is
A flat strip that is the fin board (1) and a \-shaped cut-and-raised strip (31) and the fin board (1j) connected to it
and are arranged in the flow direction.

When fins configured in this way are stacked.

The 1\-shaped strip (3) forms a multi-bend wave-shaped flow path with the same portion of other fins arranged in parallel. Since the airflow passing through this wave-shaped flow path changes direction multiple times, the overall boundary layer becomes thinner and the heat transfer coefficient improves due to the effect of repeating the run-up section. Furthermore, according to the present invention, since the strip (3) has a convex portion, it prevents the development of a boundary layer in the strip portion, so that (i) the heat transfer coefficient of the IJ tube (3) itself is improved; Then.

In combination with the above, the overall heat transfer coefficient is improved.

Furthermore, in the present invention, the performance has been dramatically improved by adding a flat strip (1j), and the presence of the flat strip (1j) makes it possible for the helical strip (3) to change the flow direction between the two. Because the separation from sin becomes longer,
-S) Unlike the fourth conventional example, the boundary stratification that affects the leading edge of the IJ knob (3) almost disappears, and the front effect of the \-shaped strip (3) on the wake side of the air is fully utilized. , high heat transfer coefficient can be obtained. Also, as can be seen from Figure 11, even when Finn is attacked.

The adjacent strips of parallel fins do not have a boundary layer influence on each other and inhibit the AiJ edge effect, which is different from the conventional example 2. This is also an effect of inserting a flat strip in the middle of the cross-shaped strips, and separating the positions of the single-shaped strips of the parallel fins.

The front edges of the IJ tubes having convex portions according to the present invention are all arranged in a parallel row with respect to the flow direction. The IJ tubes on the upper and downstream sides are carefully designed so that the direction of boundary layer growth is not on the same plane.

Even if they are on the same plane, they are far apart and the boundary layer of the pre-strip almost disappears and has no effect. In addition, it does not have an unreasonable configuration that would cause flow separation or turbulence that would cause a decrease in heat transfer characteristics or an increase in wind pressure loss.

The heat exchanger of the present invention formed by laminating these fins not only improves the heat transfer characteristics of the wave-shaped flow path described above, but also improves the heat transfer coefficient because the leading edge effect of each stage works well. This is a dramatic improvement over conventional examples, and wind pressure loss is also reduced.

Fig. 12 is a performance comparison diagram of the heat exchanger of the present invention and the fourth conventional example shown in Figs. This is the front wind speed on the fin side.

According to FIG. 12, the above embodiment of the present invention has an average surface heat transfer coefficient greater than 25% and 3
Wind pressure loss is small around 0% (front wind speed 1m/2, nearby)
This makes clear the great practical value of the present invention.

FIG. 13 shows another embodiment of the present invention, in which the embodiment is
In this example, the corners of the waveform are rounded and the IJ tube (31) is used, as shown in Fig. 13. This is the same as the conventional example.

This embodiment also has almost the same effect as the previous embodiment, but since the strip (3) is formed in a smooth and informal shape, the wind pressure loss is slightly reduced. However, the heat transfer coefficient decreases somewhat.

Either embodiment may be selected as appropriate depending on the conditions of use.

Further, although it is not known in the art, the present invention also has a fin having a C-shaped strip that is fully curved, so that the fin has sufficient strength.

As described above, the present invention makes a large number of cuts in the fin portion between adjacent heat exchanger tubes perpendicular to the direction of the tube stage, and provides a convex part at every other cut in the flow direction. As a result, the cross-sectional structure of the raised portion of the fin cut 9 is such that the flat strips A1-shaped strips are arranged alternately in the flow direction so that the boundary layer growth direction of each strip is not on the same plane. , the leading edge effect is fully demonstrated,
The present invention provides a heat exchanger that smoothly guides the flow, reduces wind pressure loss, and has a very high heat transfer coefficient.

[Brief explanation of drawings]

Fig. 1 is a plan view of the fin of the first conventional example, Fig. 2 is a sectional view of the cut-out portion of the fin of the first conventional example, and Fig. 3 is a fin plan view of the fin of the first conventional example.
FIG. 3 is a plan view of a conventional fin. Figure 4 is a new view of the cut-out part of the third fin;
The figure is a schematic diagram of the air flow phase of the third conventional example. Fig. 6 is a plan view of the fin of the second conventional example, Fig. 7 is a sectional view of the cut-out portion of the fin of the second conventional example, and Fig. 8 is the fin of the fourth conventional example.
FIG. 9 is a sectional view of the cut-and-raised portion of the fin of the fourth conventional example. FIG. FIG. 11 is a cross-sectional view of a cut and raised portion of a fin of a heat exchanger according to an embodiment of the present invention. FIG. 12 is a characteristic comparison diagram between a conventional heat exchanger and the heat exchanger of the present invention, and FIG. 13 is a sectional view of a cut-and-raised portion of a fin of another embodiment of the heat exchanger of the present invention. The same line numbers in the figure indicate the same or corresponding parts (11 is the fin board, (2) is the heat exchanger tube insertion port, and (3) is the cut-out strip. Agent Masuo Oiwa No. 1 Figure 2 Figure ths Figure 5 Intestine 6 View 7 Figure 8 Figure 99A Figure 10 Figure 11 Figure N13 Figure 12vA Frontal abdominal velocity.

Claims (1)

[Claims] A great fin tube heat exchanger is composed of multiple rows of stacked great fins and heat transfer tubes that penetrate through these fins and hold them in close contact, and the refrigerant in the heat transfer tubes and the air passing between the fins exchange heat. In this method, a cut and raised strip (strip) is provided in a direction perpendicular to the flow direction of air passing between the fins in the fin part between adjacent heat exchanger tubes in the fin longitudinal direction, and the shape of the cut and raised strip is A heat exchanger characterized in that it is formed in a \-shape with a chevron-shaped part in the center, and a flat plate is provided between adjacent cut-and-raised parts parallel to the flow of air.