An experimental study of feedwater flow rate effects on technical and economic performances of a stepped solar still

In the present study, a galvanized iron stepped solar still is examined via a solar simulator with a radiation power of 904 W/m2. To enhance the evaporation rate, a number of galvanized iron fins were fabricated to create hot points on step surfaces. For the experimental study, the input feedwater flow rate was set to be 0.086, 0.098, 0.146, 0.167, and 0.190 lit/min, measuring the temperatures of different points in the system and freshwater production rate in the internal and external condenser during 150 min at each of these flow rates. Then, the temperature variations and distillate production rates were provided in the form of diagrams. To complete the study, the cost of distillate production in different conditions was calculated. The results showed that the distillate production rate, and consequently, the cost of distillate production were lower at smaller flow rates. In all the distillation production tests, the curve began at a relatively small slope and then continued to rise linearly. As a result, it was observed that distillate production would continue if the solar simulator operated for a longer time. Furthermore, the optimal initial feedwater flow rate for the maximization of distillation production seemed to occur at the flow rates of 0.086 and 0.098 lit/min. The lowest prime cost of distillate production was obtained to be 9.4 ¢/L at the lowest flow rates, which was found to be acceptable in comparison with similar studies.