Experimental investigation of a rhombic solar collector without riser by using Sio2/water nanofluid

Geometry change and thermal properties of coolant can increase the efficiency of solar collectors. In this study, solar flat plate collector which has rhombic geometry, with helical piping and without raiser is investigated. In order to increase performance, the SiO2/water nanofluid that is made by two-step methods and with 1% concentration is used. Collector is experimentally tested in Behbahan city in the south of Iran according to ASHRAE standard. Water and nanofluid (without surfactant) are tested in collector with similar conditions. Performance evaluation is consist of the effect of flow rate, temperature, solar radiation and ambient conditions. The results show that the rhombic collector without raiser has better performance than ordinary flat plate collector. The collector efficiency by using nanofluid is about 3% more than using net water and the maximum value of efficiency and outlet temperature by using SiO2/water nanofluid are about 66% and 780 C respectively.