The present invention relates to a fin tube heat exchanger, and more particularly to a fin tube heat exchanger for reducing noise due to airflow resistance and increasing heat transfer performance by draining water drops generated on the fin surface smoothly.
Generally, as shown in FIG. 1, a fin tube heat exchanger 1 is provided with a plurality of fin plates 2 of aluminum spaced at regular intervals and a plurality of refrigerant tubes 3 extending through the fin plates 2. The refrigerant tubes 3 extend through the fin collars 4 and are enlarged so as to be rigidly secured therein. Each fin plate 2 has a plurality of narrow raised strips extending across the direction of flow. These strips are raised from the plane in which the fin plate 2 lies for raising the heat exchanging performance.
FIGS. 2 to 4 show conventional configurations of raised strips.
As shown in FIG. 2A, raised strips 5, 6, 7, 8 or 5, 6', 7, 8' extend in a direction perpendicular to the direction of air flow shown by arrows A and B. The raised strips 5, 6, 7, 8 are formed on the same side of each fin plate 2 in FIG. 2B whereas the raised strips 5, 6', 7, 8' are formed alternately on both sides of each fin plate 2 in FIG. 2C.
Raised strips shown in FIG. 3A also extend in a direction perpendicular to the direction of air flow shown by arrows A and B. The raised strips 9, 10, 11, 12, 13, 14 in FIG. 3B are formed on the same side of each fin plate 2 whereas the raised strips 9, 10', 11, 12', 13, 14' in FIG. 3C are formed alternately on both sides of each fin plate 2.
In the case of the raised strips 5, 6, 7, 8 as shown in FIG. 2B, water drops tend to stay between adjacent raised strips 5, 6, 7, 8. On the other hand, in the case of the raised strips 5, 6', 7, 8' as shown in FIG. 2C, water drops tend to stay substantially in the form of a bridge between adjacent raised strips 5, 6', 7, 8'. In either case, water drops do not drop from the fin plate until they grow into a considerable size, thereby generating noise due to airflow resistance.
In FIGS. 3B and 3C, water drops also tend to stay between adjacent raised strips 9, 10, 11, 12, 13, 14 or 9, 10', 11, 12', 13, 14' in the same manner as described above. In this case, since each fin plate 2 is provided with a draining passage 15 along the center line of a row of refrigerant tubes 3, not as many water drops remain as compared with the strip pattern as shown in FIGS. 2A to 2C, but the heat exchanging performance is still lowered.
FIG. 4 shows another conventional configuration of raised strips disclosed in Japanese Patent Laid-open Publication No. 2-171596.
As shown in FIGS. 4A and 4B, raised strips 21a, 2lb, 21c, 23, 25a, 25b are formed on the same side of fin plate 2 by one punch on the side of air flow inlet. Raised strips 22a, 22b, 24, 26a, 26b, 26c formed in the opposite direction by another punch are formed alternately on an opposite side of the fin plate 2 simultaneously on the side of air flow outlet in addition to above-mentioned raised strips 21a, 2lb, 21c, 23, 25a, 25b. In this case, however, water drops are generated at the raised strips 21a, 2lb, 21c, 23, 25a, 25b on the side of air flow inlet, and the heat exchanging performance is lowered at the fin plate portion on the side of air flow inlet where the raised strips 22a, 22b, 24, 26a, 26b, 26c are not formed.