Experimental investigation of the effect of using closed-loop pulsating heat pipe on the performance of a flat plate solar collector

In this study, performance of a flat plate solar collector operating in conjunction with a closed-loop pulsating heat pipe is investigated experimentally. The experiments were carried out in Yazd, Iran. The experimental setup consisted of a flat plate solar collector, pulsating heat pipe, and a tank. The pulsating heat pipe's evaporator is located inside the flat plate collector. In order to investigate the effect of the evaporator length on the efficiency of the system, three different length collectors are manufactured in the evaporating section. In addition, the effects of the pulsating heat pipe filling ratio, inclination angle, and flow rate are investigated for each collector separately. Although the increase in the length of the evaporator adversely affects the convectional heat transfer, the results do not show a noticeable deterioration in the performance of the flat plate solar collector. The optimum value of the filling ratio of the pulsating heat pipe in all three devices was measured at 30%, ...