In order to reveal the difference of collector performance between horizontal and vertical all glass vacuum tube water heaters, the parameters of effective heat collecting area, total solar radiation received by two water heaters under four typical days of the year (spring equinox, summer solstice, autumn equinox and winter solstice) are calculated theoretically. The actual heat collecting performance of the two water heaters is experimentally studied, and the reliability and accuracy of the theoretical analysis are verified. Finally, using FLUENT simulation software to simulate the heat collecting process of two kinds of water heaters. The reason for the difference of collector performance between the two water heaters is explained from the aspect of flow and heat transfer inside the water heater. The results show that only in summer, the collector performance of horizontal tube water heater has advantages. In spring, autumn and winter, the heat collection performance of vertical drain water heater is better.
Keywords Solar water heater; collector performance; Instantaneous heat collection; Internal convective heat transfer