Experimental study on the operating characteristics of a trichotomous vacuum tube solar water heater

In this paper, an experimental study has been carried out to examine the operating characteristics of a trichotomous vacuum tube water heater, which has three separate water tanks, under typical sunny and cloudy weather condition, which is also compared to that of a regular solar water heater. The results show that the temperature stratification in the trichotomous solar water heater is stronger than that in the regular solar water heater, no matter it was under the sunny or cloudy weather conditions. In the trichotomous vacuum solar water heater, the temperature difference between the top and the middle is small, but there is a large temperature difference between the top and the bottom. In each water tank, there is a cold water zone in the bottom region, which is particularly evident in the high temperature water tank. During the nighttime cooling period, the temperature stratification in the low temperature water tank in the trichotomous solar water heater is the strongest, while in the bottom region of the high temperature water tank, the water temperature has the trend to rise initially but gradually become stable subsequently