Experimental investigation of an integrated collector-storage solar air heater based on the lap joint-type flat micro-heat pipe arrays

This article presents an integrated collector-storage solar air heater (ICSSAH) based on lap joint-type (LJT) flat micro-heat pipe arrays (FMHPA) and latent thermal storage (LTS). FMHPA for thermal collection and for thermal storage/release were separated and overlapped. The discharging process is not affected by the length of the collection segment. Approximately 21.03 kg of 52# industry paraffin wax was utilized as thermal storage material (TSM) to store solar energy, and the collection area was set to 1.03 m2. The influence of environmental factors on the charging process and the effects of heat transfer fluid's parameters on the discharging process were studied. An average efficiency curve was proposed according to the analysis of experimental data to evaluate thermal storage performance during charging, and a correlation between Re and Nu was fitted to predict the convective heat transfer coefficient during the discharging of the device. LJT-FMHPA-ICSSAH exhibits good thermal characteristics during experimental conditions. The thermal storage/extraction efficiency reached 73.8%/97.1%, and the average thermal storage/extraction power reached 623.7 W/815.9 W.