JPS6140920B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to fins for heat exchangers.

In general, in an air heat exchanger of an air conditioner, particularly in an evaporator, the surface temperature of the fins during operation of the air conditioner is below the dew point of the atmosphere, so that moisture in the atmosphere becomes water droplets and adheres to the surface of the fins. In particular, the gap between the fins is 1 to 3 mm, such as in automobile air conditioners.
In small and narrow heat exchangers, water droplets adhere to the air passages formed between each fin, reducing the area through which air passes and increasing ventilation resistance.This reduces the amount of air passing through and reduces the amount of heat exchanged. There is the inconvenience of doing so.
At this time, with conventional fins (hereinafter referred to as smooth fins) that are formed from as-rolled material and have a smooth surface with no irregularities, a large amount of moisture in the atmosphere stagnates and adheres to the surface in the form of beads, causing air to pass through the area. There is a drawback that the number of ventilation portions is significantly reduced due to blockage, and the amount of heat exchange is also significantly reduced, resulting in a deterioration of heat exchange efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fin for a heat exchanger that has good water removal properties and good heat exchange efficiency with less adhesion of water droplets on the surface of the fin.

The present invention was developed by focusing on the wetting phenomenon in which by roughening the surface of an object, it becomes a surface with good drainage properties with less water droplets adhering to it. This aims to achieve the above objective.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 shows an example of a small heat exchanger in which heat exchanger fins according to the present invention are used. In the figure, an evaporator 1 as a small heat exchanger includes a plurality of flexible pipes 2, one end of which is connected to a distributor 4 via a distribution pipe 3, and the other end connected to a collecting pipe 5. It is connected to the gathering room header 6 via. Further, a plurality of fins 7 are attached to the outer circumference of the flexible tube 2 at predetermined intervals in a direction perpendicular to the flexible tube 2. The spacing between these fins 7 is, for example, about 1 to 3 mm.

In such a configuration, the low-pressure liquid refrigerant sent from the expansion valve (not shown) to the distributor 4 flows into the flexible pipe 2 through the distribution pipe 3, and when flowing through the flexible pipe 2, The refrigerant cools the air by exchanging heat with the air flowing on the outer surface of the refrigerant 2, and it evaporates to become a low-pressure gas refrigerant, passes through the collecting pipe 5, reaches the collecting chamber header 6, and transfers to a compressor (not shown). At this time, moisture contained in the air that is cooled by flowing through the fins 7 is attached to the surface of the fins 7 as a pseudo-condensation. Since condensation of moisture in the air passing through the surface of the fins 7 is unavoidable due to the need for heat exchange, the problem is how quickly the moisture adhering to the surface of the fins 7 can be made to flow down. Therefore, in the present invention, the fin 7
The space between each fin 7 is prevented from being blocked by water droplets by forming multiple irregularities of different pitches on the surface of the fins 7 so that the attached moisture becomes a film and immediately flows down.

Next, the surface shape of the fin of the present invention will be explained with reference to FIGS. 2 to 4. These Figures 2 to 4 show the surface roughness with the vertical dimension multiplied by 1000 times and the horizontal dimension multiplied by 100 times. Figure 2 shows that the surface of the fin 7 is etched by several tens of micrometers (for example, 20 micrometers) by shotplast processing, rolling processing, chemical etching processing, etc.
The figure shows the roughness of the fin surface when the first unevenness is formed to have a surface roughness of about m). At this time, shotplast processing is performed by spraying alumina powder, and rolling processing is performed by forming a predetermined roughness on the surface of the roll, and pressing this roll surface against the surface of the fin material to transfer the unevenness. Furthermore, chemical etching is a process in which the surface of the fin material is melted with a chemical solution such as a predetermined acid.

FIG. 3 shows a fin 7 in which a second unevenness is formed on the surface of the fin 7 by shotplast, rolling, chemical etching, etc. to have a surface roughness of several μm (for example, 3 to 5 μm) in the same manner as described above.
It shows the surface roughness.

FIG. 4 shows the roughness of the surface of the fin 7 formed by overlapping the second unevenness shown in FIG. 3 on the surface of the fin 7 on which the first unevenness shown in FIG. 2 was formed. The surface shape of the fin 7 in which unevenness is formed with this double pitch is one embodiment of the fin 7 of the present invention.

By forming multiple irregularities with different pitches on the surface of the fins 7 in this way, the synergistic effect of the irregularities with small pitches and the irregularities with large pitches allows the adhering moisture to form a film without forming large water droplets on the surface of the fins 7. It adheres to the fins 7 to form a so-called wetted surface, and immediately flows down along the surface of the fins 7. That is, the water condensed on the surface of the fins 7 easily becomes a film due to the small irregularities, is retained in the concave portions of the large irregularities, and quickly flows vertically downward of the fins 7 by the action of the drainage grooves created by the large irregularities.

Incidentally, in practice, the irregularities formed on the surface of the fin 7 are not limited to those of different double pitches as in the embodiment shown in FIG. The method of forming the unevenness is also not limited to the above processing method.

In this example, a lump of metal with a large diameter is first hit on the surface of the transfer roll to form rough irregularities, and then metal powder with a small diameter is shotplasted onto the surface to form small irregularities. Rolled and transferred onto the material.

5 to 7 and 8 are diagrams for confirming the effects of the present invention.

FIGS. 5 to 7 are diagrams showing differences in moisture adhesion due to differences in fin surface shape when cooling fins are placed in the atmosphere under the same conditions. In other words, Figure 5 shows the surface condition of a conventional smooth fin that does not have any unevenness, and the water droplets are bead-shaped and remain in place without flowing down along the fin surface, indicating poor drainage performance. It shows. In this way, the first problem is that the drainage is poor.
As shown in the figure, in a heat exchanger with narrow fin spacing, the space between the fins becomes clogged with water droplets, which increases the ventilation resistance of the air flowing between the fins and significantly impairs the heat exchange performance of the heat exchanger. . Also,
Water droplets adhering to the surface of the fins may be blown off from the cold air outlet by the blower, causing extreme discomfort to the user. Figure 6 shows the state of moisture adhering to the surface of a fin with only large irregularities as shown in Figure 2 on the smooth surface of the fin, and compared to the smooth fin in Figure 5, the effect of water removal due to the wetting phenomenon is However, the water cannot be sufficiently drained into a film that drains well, resulting in a mixed bead-like and film-like state. It has been confirmed that even when only relatively small pitch irregularities are formed on the surface of the smooth fin as shown in FIG. 3, a state similar to that shown in FIG. 6 is obtained. Figure 7 shows the state of moisture attached to the fins according to the present invention, which have a surface shape as shown in Figure 4.Since the moisture adheres to almost the entire surface in the form of a film, the water draining property is very good. I understand.

Figure 8 is a diagram in which the horizontal axis represents the wind speed v _f (m/s) in front of the heat exchanger and the vertical axis represents the ventilation resistance Δp (mmAq) in the heat exchanger shown in Figure 1. . In the figure, a straight line A connected by white circles shows the characteristics of the fin according to the present invention, a straight line B connected by black circles shows the characteristics of a fin in which only relatively large pitch unevenness is provided on a smooth fin, and a straight line connected by X marks C shows the characteristics of a conventional smooth fin. According to this figure, the fins of the present invention are 0.3mmAq to 0.5mm thicker than the fins with simple unevenness across the entire frontal wind speed.
It can be seen that the ventilation resistance is reduced only by Aq, and the draining performance is sufficiently improved.

As described above, according to the present invention, it is possible to provide a fin for a heat exchanger that has good drainage properties and has very little bead-shaped water droplets adhering to its surface.

[Brief explanation of the drawing]

Fig. 1 is a schematic plan view showing an example of a heat exchanger to which the present invention is applied, Fig. 2 is an explanatory diagram showing the surface roughness of a fin with relatively large pitched unevenness, and Fig. 3 is a schematic plan view showing an example of a heat exchanger to which the present invention is applied. An explanatory diagram showing the surface roughness of a fin with a relatively small pitch unevenness formed thereon. FIG. Figure 5 is an explanatory diagram showing the state of water droplet adhesion on a conventional smooth fin (reference photo included), and Figure 6 is an explanatory diagram showing the state of water droplet adhesion on a conventional smooth fin with only irregularities. (Reference photo included), Figure 7 is an explanatory diagram showing the state of water droplet adhesion on the fin of the present invention (Reference photo included), Figure 8 is a conventional smooth fin, a conventional smooth fin with simple irregularities, and a book. FIG. 3 is a diagram showing the relationship between front wind speed and ventilation resistance in a heat exchanger configured using the fins of the invention. 1...evaporator, 7...fin.

Claims (1)

[Claims] 1. In a heat exchanger fin installed around a pipe through which refrigerant flows, the surface of the fin has a depth of 15 mm.
A rough surface consisting of large wavy irregularities with a pitch of ~20μ and about 10 times that, and small wavy irregularities with a depth of 3 to 5μ and a pitch of about 10 times that, formed on the surface of the large wavy irregularities. A heat exchanger fin characterized by being provided with.