Performance improvement of thermosyphon solar water heater: minimizing water flow rate in some risers of the solar collector (Thai)

Abstract

This paper presents a method to increase the performance of a thermosyphon solar water heater with horizontal tank by minimizing water flow rate in some riser tubes of the solar collector. Its performance depends on the water temperature in the solar collector. Heat from solar radiation was absorbed by the absorber plate and transferred to the water, which flows in the riser tube. If the water in the riser tubes flows slowly, a higher rate of heat transfer to the water is obtained. Therefore, the water temperature is increased. Three experimental models were made by adjusting regulating valves in every riser at the top header of the solar collector. Model I is 100% valve opening for all risers. Model II is 50% valve opening for all risers. In Model III, the valves are 100% opened for every other tube. The results show that the lowest efficiency is Model I which is 17.71% and the highest efficiency is Model III which is 35.07%. This will be the new design for a thermosyphon solar water heater by reducing the diameter at the end of the riser near the top header in the solar collector.