Investigation of liquid heating efficiency of solar collectors which follows sun in two dimensions

In this study, a liquid heater, which has a conical collector following sun in two dimensions, was designed and engineered to reach higher temperatures and its performance was evaluated in terms of basic system parameters. Being designed differently from previously used systems, current system has a conical collector with a absorber at its focal point. By following the position of sun from sunrise to sunset, sun rays were reflected onto absorbent vertically all the time.The performance of this conical liquid heating system was investigated at different flow rates. Effect of flow rates on output temperatures, useful heat and collector efficiency was evaluated at 6 different values changing between 5 mL/s- 30 mL/s. Results showed that output temperature decreases with increasing flow rates and the highest temperature (65,9 ? C ) is obtained at 5 mL/s while the lowest temperature (47,6 ? C) is obtained at 30 mL/s flow rates. It was observed that useful heat increases with increasing flow rates and highest useful heat is observed at 30 mL/s flow rate. Also flow rated showed positive effect on collector efficiency and 20-25 % efficiency was obtained at 30 mL/ s flow rate.Change in characteristic properties (FR and UL) of conical liquid heating system was also studied. Heat gain factor (FR) showed an increase with flow rate because of increasing collector efficiency. FR value was observed between 0.2 and 0.25 at 30 mL/s flow rate. Because of high surface temperature of absorber and lack of vacuum between absorber and glass tubes, heat lost coefficient (UL) is high for all flow rates and it decreases with increasing volumetric flow rate of the fluid circulating in the system.