Parametric study and optimization of a new type of solar air collector employing flat micro heat pipe arrays

The performance improvement of flat-plate solar air collectors (FPSACs) is vital for solar energy utilization. Accordingly, flat micro heat pipe arrays (FMHPAs) have been utilized to FPSACs given their excellent thermal conductivity and suitable specific surface area. To investigate the impact of structural parameters of the flat-plate solar air collector with flat micro heat pipe arrays and optimize the performance, this study establishes a CFD 3D model of the collector with L-shaped flat micro heat pipe arrays. Fin height H, fin spacing L, glass thickness D, and air gap thickness Sair are selected as four important structural parameters for numerical work. Response surface methodology is adopted to recognize the significance of each factor and realize the prediction and optimization of the collector's thermal efficiency. Results show that the thermal efficiency can achieve a peak value of 52.50%. An enhanced heat transfer condition in condensation is obtained when the optimal fin height and fin spacing are 25 and 4 mm, respectively. An improved thermal insulation in evaporation is also achieved when the optimal glass thickness and air gap thickness are 3 and 35 mm, respectively. The significance order of the factors is H > L > D > Sair. The results can be served as an important reference for designing the flat-plate solar air collectors.