A STUDY OF NATURAL CIRCULATION FLOW RATE THROUGH SINGLE-ENDED EVACUATED TUBE SOLAR COLLECTORS

摘要

Water-in-glass evacuated tube solar water heaters have had a large market in China over the last decade but the longterm performance of this type of system has not been systematically evaluated. One of the factors that influence the system performance is the thermal stratification in the tank, and in systems where the collectors are directly connected to the storage tank, the stratification is primarily influenced by the collector flow rate. This paper outlines an experimental program and numerical simulations that were undertaken to develop a correlation of natural circulation flow rate through single-ended evacuated tubes as a function of solar input, tank temperature, collector inclination and tube aspect ratio.