Heat transfer characteristics of a two-phase closed thermosyphon considering the working fluid filling ratio

Abstract

In this study, the heat transfer performance of a two-phase closed thermosyphon was experimentally measured and compared according to the working fluid filling ratio. The total length of the thermosyphon was 1,000mm and the lengths of the evaporator and condenser were varied to 5:5, while the working fluid was filled to 20%, 40%, 60%, and 80% for the experiments. The working fluid was HFE 7100. The evaporation region temperature is 90°C and to exchange heat energy, the condensation region was supplied air. To achieve high heat transfer performance, the condensation region of thermosyphon had annular round fins. The air flow velocity of condensation region was 2m/s. This study's result was presented as a value of heat transfer amount and effective thermal conductivity. The heat transfer amount of thermosyphon was measured at condensation region. The effective thermal conductivity was calculated using themosyphon's temperature at evaporation and condensation region. The highest heat transfer performance for the thermosyphon and effective thermal conductivity were obtained with a filling ratio of 40%. And it means that the optimal value of working fluid filling ratio exists.