An evacuated solar collector system with flow boiling in tube has high collector efficiency of solar energy. In this paper, we present experimental and simulation results for characterizing an evacuated flat plate solar collector. By comparing the experiment results with six boiling heat transfer correlation equations, we found that Sani’s correlation is closest to our experimental results. Subsequently, this paper reports on how various factors impact collector efficiency. Collector efficiency decreases with decreasing flow rate of the working fluid, with decreasing solar irradiation, with reduction of thickness and thermal conductivity of the heat collector plate. Collector efficiency increases with decreasing saturation temperature of the working fluid, with decreasing vacuum pressure in the collector, with small bending angle of the heat collector tube. Collector efficiency does not change with change of inside diameter of the heat collection tube, and with change of inlet subcooling temperature of the working fluid.

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