A case study on internal flow patterns of the two-phase closed thermosyphon (TPCT)

Abstract

This study investigates types of two-phase flow patterns that affect the heat transfer rate which occurs within the two - phase closed thermosyphon (TPCT) made of heat-resistant glass tube with inner diameters of 7 and 25.2 mm. Aspect ratio was 5 while the inclination angels were 0°, 80° and 90°, and the evaporator temperature were 50, 70 and 90 °C. Furthermore, the addition rate of chemical reactants was 50% by volume of the evaporator component whilst the water temperature within the condensation unit was maintained at 20 °C. From the experimental results, the TPCT's inner diameter was 7 mm, the inclination angels were at 80° and 90°. There were four types of flow pattern including; bubble flow pattern, slug flow pattern, churn flow pattern and annular flow pattern. Churn flow pattern and the annular flow pattern affected the heat transfer rate of the TPCT with the inner diameter of 7 mm at the inclination angels of 80 and 90° respectively. As for the TPCT test, the inner diameter of 25.2 mm with the inclination angels of 80° resulted in four types of the flow patterns, including the bubble flow pattern, slug flow pattern, churn flow pattern and stratified flow pattern respectively. According to the results, churn and stratified flow patterns, were the types of flow that affected the heat transfer rate. According to the experiment of TPCT with inner diameter of 25.2 mm at the inclination angels of 90°, four flow patterns including the bubble pattern, slug flow pattern, churn flow pattern and the vortex flow pattern were found. The vertex flow pattern was initiated when the temperature of the evaporator section was raised from 70 to 90 °C. According to this experiment, the churn flow and the vortex flow patterns were able to affect the heat transfer rates. Furthermore, the experiment revealed that heat flux that was obtained from the experiments of TPCT with the inner diameter of 7 and 25.2 mm showed the highest heat transfer rate at evaporation temperature of 90 °C and the inclination angels of 80° which were 31.88 and 58.15 W, respectively.