In this study, heat and moisture transfer model of an enthalpy exchanger is proposed. With separately measured sorption constant and diffusion coefficient, the model predicts the heat and moisture transfer effectiveness of an enthalpy exchanger. Two sample enthalpy exchangers were tested at a KS condition to verify the model. The model predicts the heat transfer effectiveness within 4%, and the moisture transfer effectiveness within 10%. Pressure drop is predicted within 6%. The spacer fin efficiency for heat transfer was 0.11 to 0.13. The fin efficiency for moisture transfer, however, was negligibly small. For heat transfer, the conduction resistance to total thermal resistance was less than 1%. For moisture transfer, however, membrane resistance was dominant to convective moisture transfer resistance.

In this study, wet surface j and f factors were obtained for spiral fin-and-tube heat exchangers. Nine samples having different fin pitches (2.12, 2.54 and 3.18 mm) and different tube rows (1, 2 and 3 row) were tested. Data are compared with those of the dry surface. For the wet surface, the effect of fin pitch on j factor is not significant. However, f factor decreases as the number of tube row increases. The j factor increases as the number of tube row increases. Different from the j factor, f factor decreases as the number of tube row increases. At one row configuration, the dry surface j factor is larger than that of the wet surface one. As the number of tube row increases, the trend is gradually reversed. Possible reasoning is provided considering the condensate behavior under wet condition. A new j and f factor correlation is developed, which predicts j and f factors within ± 20% and ± 30%, respectively.

Heat transfer and pressure drop characteristics of fin-and-tube heat exchangers having sine wave fins and oval tubes were investigated. Oval tubes having an aspect ratio of 0.6 were made, by deforming 12.7 mm round tubes. Twelve samples, having different fin pitch and tube row, were tested. The effect of fin pitch on the j and f factors was negligible. The effect of the tube row on the j factor, however, was different from that of common fin-and-tube heat exchangers having plain fins and round tubes. The highest j factor was obtained for a two-row configuration, while the lowest one was obtained for a one-row configuration. A possible reason was attributed to the flow mixing characteristics of the sine wave channel of the present geometry. Comparison with a plain fin-and-tube heat exchanger having 15.88 mm O. D. round tube reveals that the present oval fin-and-tube heat exchanger shows generally superior thermal performance, except for the one-row configuration.