JPH01111177A - Heat exchanger with diagonal corrugated fins - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a heat exchanger with fins used in air conditioners such as room air conditioners, and is particularly suitable for outdoor heat exchangers of heat pumps. Regarding heat exchangers.

[Conventional technology]

Regarding the structure and performance of diagonal corrugated fins, see Refrigeration Volume 57, Volume 6.
No. 55 (Sho 57-5), pages 464-472. According to this, the intersecting corrugated fins cause rotation of the airflow along the corrugated wall surface, promoting agitation of the air and achieving good heat transfer performance. Furthermore, since there is no raised louver in the middle of the fin, there is no renewal of the boundary layer at the tip of the louver, and there is no frost buildup at that part.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional technology does not take into consideration frost formation at the tips of the fins into which air flows, and there is a problem in that frost builds up at the tips of the fins.

An object of the present invention is to reduce the amount of frost formed at the fin tip portions of a heat exchanger with diagonal corrugated fins, and to obtain a heat exchanger that is less likely to become clogged with frost.

[Means for solving problems]

A cross-corrugated fin consisting of fins with waveforms diagonal to the incoming air, stacked at predetermined intervals so that the waveforms intersect alternately, and a group of pipes inserted at right angles to the fin group, through which fluid flows. This is achieved by placing the pipe eccentrically on the downstream side of the incoming air in the heat exchanger.

[Effect]

By shifting the pipe to the air downstream side from the fin center position, the distance from the pipe to the fin tip becomes longer.

Therefore, when the pipe is at a low temperature of 0° C. or lower, the temperature at the tip of the fin is higher than the temperature of the pipe and closer to the temperature of the air. As a result, the amount of water vapor in the air that forms frost on the tips of the fins is reduced, and it is possible to prevent the tips of the fins from becoming clogged with frost.

Diagonal waveform fins promote air mixing by swirling the air, and improve heat transfer performance by eliminating temperature distribution. As a result, there is no part like the tip of the louver where the amount of frost increases dramatically, and the frost is almost uniform in the middle part of the fin.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 shows one side of the diagonal corrugated fin of the present invention.

The waveform 3 provided on the fin A1 surface has an upward slope of 15° with respect to the airflow direction 4. The pipe center position indicated by fin collar 2 is located on the air downstream side of the center of the fin, and c3x is larger than d2.

FIG. 2 shows the remaining half of the diagonal waveform fin of the present invention.

The waveform B6 provided on the surface of the fin 85 has a downward slope of 15'' with respect to the airflow direction 4.The position of the pipe is shifted from the center of the fin to the downstream side of the air, as in FIG.

The diagonal corrugated fin heat exchanger of the present invention has fins A and fins B alternately stacked at regular intervals, and heat transfer tubes inserted at right angles. FIG. 3 is a view of the fin tips of the assembled cross-corrugated fin heat exchanger as seen from the air inflow direction. The distance between fins A and fins B is narrower or wider, and it is expected that the narrow portions are likely to become clogged with frost. However, in the present invention, since the pipe position is shifted toward the air downstream side from the center of the fin, clogging due to frost at the tips of the fins can be prevented.

FIG. 4(a) is a graph of temperature distribution explaining the reason. The horizontal axis is the distance taken from the fin tip in the airflow direction. Curve 7 shows the change in airflow temperature, and the air flowing in from the fin tip is gradually cooled down to a low temperature. Curve 8 is the average temperature at that distance of the fin. Since the pipe center position 9 is shifted toward the air downstream side from the center of the fin, heat conduction to the fill tip becomes poor, and the fin tip temperature becomes high and approaches the air flow temperature 7.

As a result, the amount of frost formed at the tips of the fins is reduced, and there is no longer any clogging caused by frost there.

In the middle part of the fin, the swirling flow of air along the waveform causes intense mixing, so while maintaining high heat transfer performance, there is no area where frost is locally concentrated.

Next, consider the amount of eccentricity of the pipe. The width (dz+d2) of the conventional fin is about twice the pipe outer diameter do, and the fin width d1 on the air upstream side from the pipe center position is equal to the fin width d2 on the air downstream side from the pipe center position.

Now, the pipe outer diameter do is fixed as 10+nm, the air downstream side fin width d2 is fixed as 1.0 mm, the fin pitch fp is 2 nn, and the fin plate thickness δ is fixed as 0.13 mm, and the air upstream side fin width d1 is gradually increased from 1.0 nn. FIG. 4(b) shows the change in performance when the length is changed to 20IIN11.

The fin efficiency φ gradually decreases as dl increases, but the time t until frost buildup gradually increases. The rate of change in heating capacity until clogging due to frost is expressed as the product of the fin efficiency φ and the time t until clogging, as shown by the -dotted chain line in FIG. 4(b). The heating capacity ratio gradually increases when dx/da becomes larger than 1, reaches a peak when dz/d2 is around 1.2, and d1/d
If 2 exceeds 1.5, the value will be lower than when dx/dx is 1. In the end, the heating capacity per fin material cost is greater than that of conventional fins because d1/d2 is 1.
It ranges from 0 to 1.5. Therefore, the scope of claims of the present application is expressed by the following formula.

1.0<dz/d2<1.5...(
1) Figures 5 to 7 show another embodiment. That is, 5th.
As shown in FIG. 6, a band-shaped flat portion 12 is provided at the tip of the fin on the air inflow side. At this time, the pipe is also shifted toward the air downstream side from the center of the fin. That is, in FIG. 5, dl>dz. In this way, the fins A' and fins B' having flat portions at the tips of the fins are stacked alternately, and a pipe is passed through the inside of the fin collar to form a heat exchanger. Looking at this heat exchanger from the air inlet side,
It looks like Figure 7. The solid line (straight line) in FIG. 7 is the shape of the fin tip, and the broken line (wavy) is the shape of the fin middle portion. The tips of the fins, which are most susceptible to frost formation, are not curved as shown in Fig. 3, but are straight lines as shown in Fig. 7, eliminating narrow fin spacing and creating fins that are more resistant to clogging due to frost. can get. Flat portion 12 and waveform A3 or waveform B6
This means that the waveforms are continuous and smooth, and care is taken to prevent frost from forming on the tip of the waveform.

FIGS. 8-9 show yet another embodiment. In other words, the distance dz between the fin tip and the pipe center in FIG.
The distance is different from the distance d8 in the figure. The relationship in FIGS. 8 and 9 is d s";> d B> d 2, but it is not limited to this. When the fins in FIG. 8 and the fins in FIG. 9 are stacked alternately, The tip of the fin in Figure 8 is
The spacing becomes wider, as if the fin pitch had doubled. Furthermore, the positions of the tips of the fins, which are prone to frost formation, are alternately shifted. As a result, a frosted state as shown in FIG. 10(a) is created, and clogging due to frost becomes difficult to occur. Fins in which the tips of the fins alternately protrude and retract are called staggered fins. Next, the value of the stagger amount (da-dx) will be considered. With diagonal waveform fins, a lot of frost accumulates on the fin tips on the air inflow side, causing buildup in this area, so only the fin tips will be considered. FIG. 10(b) shows the frosting state when the distance to the fin tip is -like, and the frosting distribution is approximated by a circle. FIG. 10(c) shows the stagger amount (cl
a-di) is equal to the fin pitch fp,
Clogging is less likely to occur than in the case of FIG. 10(b). In Fig. 10(d), the stagger amount (ds dl) is set to twice the fin pitch, 2 f p , and frost with a diameter twice that of Fig. 10(b) is deposited before clogging occurs. be able to. However, even if the stagger amount is increased further, the area that is twice the fin pitch will be clogged, so
It has no effect.

Therefore, the range of the following equation is appropriate for the stagger amount (da-dt).

fp≦(da dz)≦2fp...
- (2) Figures 11 and 12 show yet another embodiment. This stagger fin is provided with a flat portion 12 shown in FIGS. 5 and 6 at the tip of the fin. Since the tips of the fins are straight, there is no narrow part between the fins, making it even more effective against frost formation. However, fin B′ in FIG.
Since the waveform of fin A' shown in FIG. 11 has already started at the tip of the fin, the fin spacing will be narrow in some places and wide in others. In areas with narrow fin spacing, there is a risk of clogging due to frost. The embodiment shown in FIGS. 13 and 14 was devised to improve this problem. In this embodiment, the width of the flat part 13 of the fin (fin A' in FIG. 13) with the longer distance d1 from the tip of the fin to the center of the pipe is increased, and the distance d4 from the position where the waveform starts to the center of the pipe is increased. is set to the same value as fin B' in FIG.

As a result, the fin tips are flat and the fin spacing is constant until the waveform starts.

Figures 15 and 16 show yet another embodiment. In this example, a flat portion is provided at the center of the pipe and also at the rear end of the fin. The flat portion 14 at the center of the pipe has the effect of accurately shaping the distance between the fin collars 2 and facilitating pipe insertion. In addition, since water droplets condensed on the fin surface also fall through the flat portion 14, a fin with good drainage properties can be obtained. The flat portion 15 at the rear edge of the fin is provided to prevent the fin from deforming when cutting the fin A' or the fin B' in the longitudinal direction. The width of the flat portion is preferably set to the minimum necessary value. This is because by providing a large number of flat parts, the original effect of the cross-corrugated fins is weakened. In addition, the boundary between the flat part and the corrugated part should be connected smoothly, and care must be taken to avoid excessive ventilation resistance due to separation of the flow in this part.

Figures 17 and 18 show yet another embodiment. The direction of the waveform 22 is switched by a pipe center line 24 where the air flow is vertically symmetrical and a horizontal line 25 passing through the center between the pipes. That is, in the fin C (20), an upwardly sloping waveform is provided in the upper half of the horizontal line 25 passing through the center between the pipes, and a downwardly sloping waveform is provided in the lower half of the horizontal line 25. Fin D (21) stacked alternately with fin C
In this case, contrary to the fin C, a downwardly sloping waveform is provided in the upper half of the horizontal line 25, and an upwardly sloping waveform is provided in the lower half.

By making the waveform symmetrical along the vertical line of symmetry in this way, air flows symmetrically around the pipe, which is effective in improving heat transfer coefficient and reducing pressure loss. Also, when manufacturing fins, if only one waveform is used, the fins will gradually deform and may be crushed by long fins, but if the direction of the waveform is changed over a short range as in this example, Deformation of the fins can be prevented, resulting in the effect that the fins can be easily handled when manufacturing a heat exchanger by laminating fins.

〔Effect of the invention〕

According to the present invention, it is possible to prevent clogging due to frost at the tips of the air inlet side fins of a heat exchanger with diagonal corrugated fins, and to achieve high heat transfer performance and uniform frost distribution.
A frost-resistant heat exchanger suitable for an outdoor heat exchanger of a heat pump type air conditioner can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a fin according to an embodiment of the present invention, FIG. 2 is a plan view of a fin paired with FIG. 1, and FIG. 3 is a fin of a heat exchanger according to an embodiment of the present invention. Figures 4(a) and 4(b), which are views of the tip viewed from the air inflow direction, are & representing the temperature distribution of the air and the fins. 5 to 7 show other embodiments, FIG. 5 is a fin plan view, FIG. 6 is a plan view of the fin paired with FIG. 5, and FIG. 7 is a fin plan view of the heat exchanger. FIG. 3 is a view of the tip portion viewed from the air inflow side. Figures 8 to 1
FIG. 0 shows still another embodiment, and FIG. Figure 9 is a plan view of a pair of fins, Figure 10 (a) and (b)
(c) and (d) are explanatory diagrams of frosting conditions. 11 and 12 are plan views of a pair of fins showing yet another embodiment, and FIGS. 13 and 14, and FIGS. 15 and 16 each showing still another embodiment, forming a pair. It is a top view of a fin. FIGS. 17 and 18 are plan views of a pair of fins showing still another embodiment of the present invention. 1... Fin A, 2... Fin color, 3... Waveform A, 4... Airflow direction, 5... Fin B, 6...
Waveform B, 7...Airflow temperature, 8...Fin temperature, 9.
...Pipe center position.

Claims (1)

[Claims] 1. A pipe in which fins each having a waveform diagonally relative to the incoming air are stacked at a predetermined interval so that the waveforms intersect with each other at a predetermined interval, and the pipe is inserted at right angles to the group of fins, through which fluid flows. A heat exchanger with diagonal corrugated fins, characterized in that the pipe is eccentrically positioned on the downstream side of incoming air. 2. A heat exchanger with diagonal corrugated fins according to claim 1, wherein a band-shaped flat portion is provided at the tip of the fin. 3. Claim 1 in which two types of fins with different distances from the pipe center position to the fin tips are stacked alternately
Heat exchanger with diagonal corrugated fins as described in Section 1. 4. A heat exchanger with diagonal corrugated fins according to claim 3, wherein a band-shaped flat portion is provided at the tip of the fin. 5. Change the width of the band-like flat part of the fin tip, widen the flat part of the fin with a long distance from the pipe center position to the fin tip, and make the flat part of the fin with a short distance from the pipe center position to the fin tip. 5. A heat exchanger with diagonal corrugated fins according to claim 4, wherein the width of each portion is narrow. 6. The heat exchanger with diagonal corrugated fins according to claim 5, wherein a band-shaped flat portion is provided at the rear end of the fin and also at the center of the pipe.