Experimental study on a prototype solar water heater using refrigerant R141b as a transfer fluid

A prototype of a heat pipe type solar water heater by using refrigerant as a heat transfer fluid is investigated experimentally. The objective is to explore the performance and characteristics of the prototype when it is filled with R141b. A prototype of the solar water heater with flat plate collector is designed and fabricated. In the experiments, two different refrigerants, R141b and R718, are employed, respectively. The initial pressure of transfer fluid is varied from 10 psi to 55 psi. The prototype is exposed to solar irradiation in a location in Medan city. Solar collector temperatures, solar irradiation, water temperature, and ambient temperature are measured. The efficiency of the system is analyzed. The results show that at the same initial pressure, the solar water heater filled with R141b is better than R718. The optimum initial pressure of the solar water heater filled with R141b is 30 psi. Thermal efficiency of the solar water heater at pressure 30 psi can be up to 34%. The main conclusion can be drawn here is that the solar water heater using refrigerant R141b as a transfer fluid results in a better performance in comparison with conventional water heater. (paper)