A finite-difference method to evaluate the thermal performance of a solar water heater

Abstract--The theoretical performance of a solar water heater operating under thermosiphon-flow conditions was evaluated using a finite-difference solution procedure. Tests were conducted on an experimental heater which incorporated a flat-plate collector design. Experimental water mass flow rates were measured at half-hour intervals using a dye-injection method while the temperature distribution of the system was monitored continuously. Some defects in the theory arising from inaccurate assumptions of the mean temperatures of the various components of the system are pointed out. Fortunately, these defects are significant only during the early and late periods of the day. Throughout the main insolation period, satisfactory qualitative and quantitative agreement can be obtained between experimental and theoretical results. A proposal for future study to investigate the reverse-flow phenc, ena is introduced.