Performance evaluation of a refrigerant-charged integrated solar water heater in northern Nigeria

The thermal performance of the refrigerant-charged integrated solar water heater was analyzed to show its applicability in Nigeria, using data of several sunny and cloudy days. This unit, having three identical small-scale solar water heating systems using refrigerants R-134a, R12, and ethanol, was constructed and tested side by side under various environmental and load conditions in the Department of Mechanical Engineering, Bayero University, Kano, Nigeria. The thermal performance was evaluated extensively throughout the months of August and September 2006; the maximum water temperature increases of 28°C, 37°C and 40°C for R12, ethanol and R-134a were attained at about 14:00 h respectively, while the maximum collection efficiencies computed were 40.63%, 50.78% and 56.59% for R12, ethanol and R-134a respectively. Best performance was obtained using R134a, probably due to its higher latent heat, higher liquid thermal conductivity, and lower viscosity and high surface tension to improve capillary pumping. This reveals a good capability of the system to convert solar energy to heat which can be used for heating water in northern Nigeria.