Experimental study on the condensation of a thermosyphon by electrical capacitance tomography

The study on the condensation and the two-phase flow pattern in the condensation section is important to understand the operating mechanisms in a thermosyphon. In this paper, a new electric capacitance tomography (ECT) sensor was designed for the visualization measurement in a liquid by removing the shielding case and sealing with insulating hydrophobic material. It was successfully used to measure the condensation process in a thermosyphon under different operating temperatures. The thermosyphon was made of silica glass, and alcohol was used as a working fluid. The alcohol vapor was cooled to condense through the heat convection with the cooling water. The operating temperature was controlled by a heater with different power outputs. The experimental results show that the alcohol vapor condensed in stripes and unevenly on the wall surface at a low operating temperature. The liquid bridge will be formed periodically at the operating temperature of 90°C, and the time interval between two liquid bridges will be shorter with the increase of the operating temperature. At 117°C or even higher operating temperatures, the complete liquid bridge cannot be formed sometimes due to the difference of the growth rate of the surface wave around the circumference.