Experimental determination for optimal position of reflector in solar water heater

Abstract An experimental investigation was carried out on novel solar water heater that utilizes a flat reflector positioned underneath the absorber tubes. Experiments were conducted at National Institute of Technology Patna, India, having latitude 25.61°N and longitude 85.14° E and constant insolation of 1000 W / m 2 . The experimental data were collected for different reflector positions i.e. δ = 0 mm, 15 mm, 30 mm, 45 mm, and 60 mm and six mass flow rates of working fluid i.e. 0.0056 kg s−1, 0.0097 kg s−1, 0.0138 kg s−1, 0.0207 kg s−1, 0.0277 kg s−1, and 0.0346 kg−1s. The obtained experimental results exhibited that the location of the reflector relative to the absorber tubes significantly affects the thermal performance of the system. The effect of the mass flow rate on the outlet temperature, thermal performance, and overall performance has also been studied. For the present system under energy and exergy analysis, the optimal position of the reflector was found of δ = 30 mm. The results showed that the solar water heater with an optimally positioned reflector has a 23% increase in thermal efficiency compared to the solar water heater without a reflector. The novelty of using a flat reflector underneath absorber tube is to provide heat to rear side of the absorber tubes after reflecting the insolation falling on the reflector and hence improvement in the thermal performance of the solar water heater. The scope of present system includes providing an eco-friendly and energy-efficient solution for residential and commercial hot water needs. Limitations of the present study are requirement of sufficient roof space and direct sunlight. The use of reflectors has implications for energy savings, more efficient system designs, and enhanced thermal performance.