Boiling and Evaporation of Falling Film on Horizontal Tubes and its Enhancement on Grooved Tubes

Abstract

Thin liquid films are utilized as an important component in various heat transfer processes because of their high heat transfer rate at low feed rates and with small temperature difference. Evaporators employing such characteristics are widely found in refrigeration systems, natural gas and air liquefying facilities, petrochemical and distillation plants, and more recently are proposed for use in OTEC systems. This paper reviews recent developments on evaporation and boiling heat transfer to falling films on horizontal tubes and their enhancement. Main items focused here are; (1) analysis and experiment for evaporative heat transfer to falling films, (2) empirical formulas for predicting heat transfer coefficient, (3) falling film breakdown and resulting deterioration of heat transfer, (4) analysis of enhanced heat transfer in grooved surface, (5) experimental results for heat transfer enhancement on grooved tubes, and (6) enhanced boiling heat transfer in falling films on grooved tubes.