In this study, the heat transfer and friction characteristics of nonsymmetric slit-finned heat exchangers are experimentally investigated. Louver-finned heat exchangers are also tested for comparison purpose. The effect of fin pitch on j and f factors is negligible. Considering the small variation of the fin pitch (from 1.3 mm to 1.5 mm), the foregoing argument should hold true for the present samples. Louver fin samples yield higher j and f factors than slit fin samples. Both j and f factors increase as the number of tube rows decreases. The row effect is true for both slit and louver fin samples. For one-row configuration, j/f ratios of louver fin samples are larger than those of slit fin samples. The trend is, however, reversed for three-row configuration. Data are compared with available correlations.

In Korea, a typically hot and humid summer means that air-conditioners consume a large quantity of electricity; accordingly, the simultaneous usage of an indirect evaporative cooler may reduce the sensible-heat level and save the amount of electricity that is consumed. In this study, the heat-transfer and pressure-drop characteristics of an indirect evaporative cooler made of paper/plastic film were investigated under both dry and wet conditions; for the purpose of comparison, an indirect evaporative cooler made of plastic film was also tested. Our results show that the indirect evaporative efficiencies under a wet condition are greater than those under a dry condition, and the efficiencies of the paper/plastic sample (109% to 138%) are greater than those (67% to 89%) of the plastic sample; in addition, the wet-surface, indirect evaporative efficiencies of the paper/plastic sample are 32% to 36% greater than those of the plastic sample. Further, the wet-surface pressure drops of the paper/plastic sample are 13% to 23% larger than those of the plastic sample, and this might have been caused by the surface roughness of the samples. A rigorous heat-transfer analysis revealed that, for the plastic sample, 30% to 37% of the wet channels remained dry, whereas all of the channels were wet for the paper/plastic sample.Key words Indirect Evaporative Cooler(간접증발소자), Paper(종이), Plastic(플라스틱), Performance(성능) †Corresponding author, E-mail: knh0001@incheon.ac.kr