Experimental Investigation of the Thermal Performance of a Two-Phase Closed Thermosyphon under Developed and Geyser Boiling Phenomena in the Evaporator Section

Energy conservation is becoming increasingly important as the cost of fuel continuously rises. The two-phase closed thermosyphons are handy tools in the heat transfer process. In this study, the effect of affecting parameters on a two-phase closed thermosyphon's thermal performance was investigated experimentally. A copper pipe with a length of one meter and an inside diameter of 20 mm was constructed. Distilled water was used as a working fluid for this research. Many experiments were carried out for the inclination angle range of 5º–90º, input heat between 100 to 300 W, aspect ratio 13, 16.5, 20, and filling ratios of 25% to 70%. An experimental correlation derived from all of the results shows that the thermal efficiency increase with the increase of the filling ratio, mass flow rate of the coolant, and input heat and decreases with the rise in the inclination angle and aspect ratio. The highest thermal efficiency is obtained at input power 200 W, inclination angle 60, aspect ratio 16.5, and the filling ratio 50%. The geyser boiling has been investigated by examining the time variations of the outlet water temperature from the condenser jacket. At an input power of 100W, geyser boiling occurs, but if input power equal to or greater than 150 W combined, boiling will be observed. An empirical relationship for the period of temperature variations caused by boiling was presented. The results show that the geyser boiling period was shorter for higher input power, cooling water flow rate, and inclination angles.