A study on the Characteristics of Heat Transfer of Condensers with Various Insert Devices of Loop Type Two Phase Thermosyphons

Abstract

Two-phase thermosyphons are devices that can transfer large amounts of heat flux with the boiling and condensation of the working fluid resulting from small temperature differences. A two-phase thermosyphon consists of the evaporators, an insulation unit, and the condensers. The working fluid inside the evaporator is evaporated by the heating of the evaporator in the lower part of the two-phase thermosyphon and the evaporated steam rises to the in the upper part to transfer heat in response to the cooling fluid outside the tube. The resultant condensed working fluid flows downward along the inside surface of the tube due to gravity. The resultant condensed working fluid flows downward along the inside surface of the tube due to gravity. These processes form a cycle. In the present study, condensers with various insert devices of a loop type two-phase thermosyphon which is 480mm wide, 68mm long, and 1,000mm high was used. The heat transfer pipes in the loop type two-phase thermosyphon were 15mm in diameter and 1,000mm in length and 98 heat transfer pipes were installed in loop type two-phase thermosyphon. The inside of the condensers with various insert devices was composed of heat transfer pipes installed to increase the heat transfer surface area of the heating media in the heat transfer pipes condensers with various insert devices. Using refrigerant R134a as a working fluid for the loop type two-phase thermosyphon to conduct heat transfer performance experiments for changes in the temperature of the cooling air outside the condenser and changes in the mass flow rate. According to the results of the present experiments, as the spaces between internal discontinuous pins decreased, pressure drops increased. Changes in the temperatures at the outlet of the condenser were shown to be a little smaller. Therefore, it can be seen that as the spaces between internal discontinuous pins decreased, the heat transfer performance increased. As the temperature of the air flowing in the condenser with various insert devices increased, the condensation heat transfer rate of the thermosyphon increased. As the condenser with various insert devices refrigerant inflow temperature increased, the condensation heat transfer rate of the condensers with various insert devices of the thermosyphon heat exchanger increased.