Numerical investigation of surface wettability effect on two-phase closed thermosyphon

Abstract

A two-phase closed thermosyphon (TPCT) is promising for heat removal due to its simple structure and high performance in heat transfer. However, investigating the phase change process in TPCT through experiments with current technology is still challenging. To study the various surface wettability effects on TPCT, this is the first systematical volume of fluid (VOF) method-based numerical study. The wettability in terms of contact angles (5°, 40°, 120°, and 175°) is endowed on the surfaces of TPCT. The numerical results of heat transfer coefficients of the TPCT show good agreement compared with the correlations. The simulation results reveal that the hydrophilic evaporator and the hydrophobic condenser benefit heat transfer. Within the input power of 376.14 W, the hydrophilic evaporator can reduce the thermal resistance of the evaporator to 35.3 % and delays the vapor film formation. The hydrophobic condenser decreases the thermal resistance of the condenser at 3.64 % and prevents filmwise condensation. The surface wettability is critical to the temperature distribution along the evaporator, but the main temperature drop is located between the adiabatic section and the condenser. It is also noted that the thermal resistance of the condenser is dominant to the overall thermal resistance. This study provides a detailed physical insight into the surface wettability effect on TPCT and benefits the future design in thermal engineering applications.