An experimental study of the thermal performance of the square and rhombic solar collectors

Solar collectors are the key part of solar water heating systems. The most widely produced solar collectors are flat plate solar collectors. In the present study,  two types of flat plate collectors, namely square and rhombic collectors are experimentally tested and compared and the thermal performance of both collectors is investigated. The results show both collectors have the same performance around noon (≈ 61%), but the rhombic collector has better performance in the morning and afternoon. The values for rhombic and square collectors are approximately 56.2% and 53.5% in the morning and 56.1% and 54% in the afternoon respectively. The effect of flow rate is also studied. The thermal efficiency of rhombic and square flat plate collectors increases in proportion to the flow rate. The results indicated the rhombic collector had better performance in comparison with the square collector with respect to the mass flow rate.