Heat Transfer Characteristics of Falling Film Boiling of R1234ze(E) on a Vertical Plate

Abstract

This study experimentally investigated the heat transfer and flow characteristics of falling film boiling of R1234ze(E) on a vertical plate to clarify the effects of behaviors of boiling bubble, liquid film breakdown and dry patch on heat transfer and flow characteristics to HFO refrigerants. The liquid film flowed down with waves at the vapor-liquid interface. The generation and collapse of boiling bubbles were observed in the liquid film. As the heat flux increased, while the film Reynolds number decreased, the size of the dry patches increased. However, the dry patches were rewetted by thicker liquid film flowing at higher liquid mass flow rate. The heat transfer coefficients increased with increasing heat flux and refrigerant pressures and drastically decreased owing to the expansion of dry patches. In addition, the wet area fractions and heat transfer coefficients began decreasing at almost the same film Reynolds number.