diabatic, visualization, R410A, flow boiling
The objective of this paper is to present the mechanism of flow boiling in horizontal smooth and micro-finned tubes through visualization in diabatic conditions. In most of the literature, the flow regime of flow boiling in the micro-finned evaporator tube is visualized by the sight glass at the exit of the test section under adiabatic condition. In order to better understand effect of micro-fins in flow boiling in the visualization test section, a novel technique to visualize flow of evaporation under diabatic condition has been developed and presented. R410A flow boiling experiments are conducted at 10 °C saturation temperature in both of the smooth and micro-finned tubes with the inner diameter of 6.3 mm. The bubble generation in the liquid refrigerant is presented along with bubble departure diameter, bubble departure frequency, and nucleation sites. In addition, the flow regime of the flow boiling under adiabatic and diabatic conditions is compared.