Experimental investigation of enclosed steel tube fitted inside evacuated tube solar water heater using glazed aluminum reflector in two-stage heating
摘要
The growing global shift toward renewable energy has driven the search for more sustainable water heating solutions, leading to this study titled “Investigating the Performance of an Evacuated Tube Solar Water Heater (ETSWH)”. The system employed six evacuated tubes with a total collector area of 0.846 m2 to heat 7.8 Ls of water per charge, operating through the thermosiphon principle. The setup was tested over a period of 5 days. A target water temperature of 90 °C was set for charging during each heating cycle. Material selection for the system considered factors such as design calculations, cost-effectiveness, and local availability. Throughout the testing period, a consistent two-stage daily heating pattern was observed, with the 90 °C mark typically achieved between 12:00 and 13:30 during the first heating cycle. The highest solar irradiance recorded during testing was 623.83 W m−2, accompanied by an ambient temperature of 31.6 °C at 12:20 Hrs. Notably, the fastest time to reach the 90 °C target occurred on day 3 at 12:18 Hrs., under a solar irradiance of 567.22 W m−2, and an ambient temperature of 31.1 °C. Efficiency measurements showed that the highest thermal efficiency during the first heating stage was 63.1% at 90 °C. Meanwhile, the overall peak efficiency recorded across the experiment was 83.9%, achieved during the second heating cycle at 16:00 Hrs. on the 5th day.