Effect of Geometric Parameters on the Performance of Water in Glass Evacuated Tube Solar Heater

Abstract

Performance improvement of water in glass evacuated tube solar water heaters has received attention from many researchers yet the effect of geometric parameters on the performance of the system has not been fully explored. In this work, the effect of collector tube length, diameter and tilt angle on the temperature and velocity distribution was studied using computational fluid dynamics (CFD). The results of the CFD model were validated against experimental data. The collector tube length was found to have a significant influence on both the temperature in the storage tank and the velocity distribution. The longest collector tube (2000 mm) achieved the highest temperature compared to collector lengths of 1800 mm and 1600 mm. A larger collector tube diameter of 52 mm enhanced the average temperature in the storage tank compared to collector tube diameters of 42 mm and 47 mm. The effect of tilt angle on velocity distribution was analysed using tilt angles of 10, 23, 30, and 45 degrees and the results showed that the average flow velocity for lower tilt angles was high, however, the maximum flow velocity which occurs at regions close to the boundary between the collector tube and the storage tank was higher for high tilt angles.