Hirasawa Shigeki

Effect of surface tension on condensate motion in laminar film condensation (study of liquid film in a small trough)

Abstract This study reveals that, on a finned surface, there exists a region of high heat transfer coefficients in the trough between the crests of fins. A theoretical analysis had predicted a local thinness of the condensate film produced by the capillary action in the trough. This is confirmed by optical measurements of the film thickness in a flow of ethyl alcohol along the model vertical walls. The results of this experiment agree well with the theoretical prediction. Taking these effects into account, the performance of a vertical finned surface is computed using condensation of R-113 and water.

Heat transfer from tube banks to air/water mist flow

Abstract Heat transfer and pressure drop data were obtained with the banks of smooth tubes, microfinned tubes, and finned tubes placed in the mist stream, where the air velocity was in the range of 1–3 m s−1, and the water mass flux 50–390 kg m−2 h−1. Cross examinations of the heat transfer data indicate that evaporation of water from the wetted part of the surface area is a primary mechanism of heat transfer enhancement. Based on the empirical correlations for the effective wet area on the heat transfer surface, the method of heat exchanger design is proposed. The pressure drop data show little difference between the flow resistance in mist flows and that in single phase air flows.