Peng et al. [25] evaluated the performance of a novel solar air collector with pin-fin integrated absorber. Authors developed an original model of collector, which presents some advantages:
1. low cost;
2. high durability;
3. high thermal efficiency, due to high heat transfer coefficient even at lower air mass flow rates and low heat losses;
4. flexibility in applications of fin-pins.
This new model of solar collector contains an absorber with pin fins arrays of different lengths. From recorded data, the heat transfer coefficients of pin-fin arrays and flat plate collector have been obtained for a determined value of the air volume flow rate (19 m3/h). From theoretical model, the formula of the maximum thermal efficiencies ηmax of 25 kinds of pin-fin collectors is given as in Eq. (1) at ambient temperature: