On the Night Heat Losses in Thermosyphon Solar Water Heaters
Abstract
An experimental investigation of the effects of night heat losses on the performance of thermosyphon solar water heating systems has been carried out in this study. Based on the methodology suggested by the ISO 9459-2:95, three typical thermosyphon solar water heating systems, with different storage tanks have been tested. Analysis of the results served to quantify the night heat losses and examine the effect of these losses on the daily system performance. The results showed linearity between the heat losses and the night mean ambient temperature. The linearity correlation coefficients range from 0.93 to 0.95, while the losses reached almost 8000kJ at an ambient air temperature of 10°C. Examination of the results also revealed that for the local weather conditions in Cyprus and for the typical configuration of the thermosyphon solar water heaters used in the island, the thermosyphonic reverse flow is rather unimportant with minimal contribution to the night heat losses of the solar collector.