Experimental investigations on the heat transfer characteristics of micro heat pipe array applied to flat plate solar collector

This paper introduces a novel flat plate solar collector (FPC) using micro heat pipe array (MHPA) as a key element. To analyze the thermal transfer behavior of flat plate solar collector with micro heat pipe array (MHPA-FPC), an indoor experiment for thermal transfer characteristic of MHPA applied to FPC was conducted by using an electrical heating film to simulate the solar radiation. Different cooling water flow rates, cooling water temperatures, slopes, and contact thermal resistances between the condenser of MHPA and the heat exchanger were tested at different heating powers. The experimental results indicate that MHPA-FPC exhibits the enhanced heat transfer capability with increased cooling water flow rate and temperature. Total thermal resistance has a maximum decline of approximately 10% when the flow rate increases from 180 L h−1 to 360 L h−1 and 38% when the cooling water temperature increases from 20°C to 40°C. When the inclination angle of MHPA-FPC exceeds 30°, the slope change has a negligible effect on the heat transfer performance of MHPA-FPC. In addition, contact thermal resistance significantly affects the heat transfer capability of MHPA-FPC. The total thermal resistances lowers to nearly half of the original level when contact material between the condenser of MHPA and the heat exchanger changes from conductive silicone to conductive grease. These results could provide useful information for the optimal design and operation of MHPA-FPC.