Thermal performance of a new CPC solar air collector with flat micro-heat pipe arrays

A new type of compound parabolic concentrator (CPC) solar air collector (SAC) with flat micro-heat pipe arrays (FMHPA) was investigated in this study. A cylindrical absorber was constructed by inserting the FMHPA into an evacuated glass tube to transport heat during the working process. The new FMHPA-CPC SAC is an edge ray collector with a concentration ratio of 1.8. The core concept is the integration of the FMHPA, an absorber tube, and a CPC reflector as a heat-collecting unit. Thermal performance investigation was conducted theoretically and experimentally. This study mainly analyzed the effect of different factors on the thermal performance of the collector. The efficiencies and heat loss coefficients of the new collector were determined. Experimental curves with different testing conditions are presented. The optimal value of efficiency was determined for the SAC. The aperture area of each CPC collecting unit is approximately 0.4 m². The new FMHPA-CPC SAC was tested in Beijing, China. The average efficiency was approximately 61% at a volume flow rate of 320 m³/h, with a radiation of 799 W/m² (ambient temperature of 28.8°C). The instantaneous efficiency reached 68%, depending on the solar radiation, air volume flow rate, and ambient temperature. In addition, the time constant of the collector was approximately 14.8 min, with an air volume flow rate of 260 m³/h.