Experimental study and numerical validation on the effect of inclination angle to the thermal performance of solar heat pipe photovoltaic/thermal system

Abstract

Effect of inclination angle to the thermal performance of a heat pipe photovoltaic/thermal system (HP-PV/T) system was rarely reported. In the present study, a HP-PV/T system was firstly constructed in an Enthalpy Difference Laboratory, where inclination angle was experimentally managed as the only variable. Meanwhile, a comprehensive numerical model for the HP-PV/T system was developed to validate the experiments. Particularly, a 3D model for the inclined heat pipe was also firstly involved. The simulation results show that liquid film thickness within the condenser or the evaporator stabilizes at a constant value at inclining condition. The relative filmwise thermal resistance of the condenser decreases first and then increases with inclination angle; while the evaporator shows an opposite trend to the condenser. The overall thermal resistance of solar heat pipe is mainly determined by the evaporator while the evaporator is mainly determined by the effective height of the liquid pool. The experimental and simulation results both indicate that the optimum inclination angle is 40°. The proposed model agrees well with the experimental results at big inclination angles (≥20°), it is practicable to reveal the influence of inclination angle to the thermal performance of a HP-PV/T system.