B.R.ChenW.S.LeeS.L.ChenSIH-LI CHEN2021-10-072021-10-072005www.swc2005.orghttps://scholars.lib.ntu.edu.tw/handle/123456789/584192https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870490292&partnerID=40&md5=820bbcbfe36a360af5f7a19119055588This article studies the long-term charge performance of a two-phase closed thermosyphon solar water heater. It utilizes the superior heat transfer characteristics of boiling and condensation and eliminates drawbacks found in the conventional systems. Experimental investigations are first conducted to study the thermal performance of the solar water heater under different weather conditions. The result indicates that the charge efficiency is affected by the solar irradiation intensity. High irradiation could enhance the boiling heat transfer inside the thermosyphon and increase the thermal performance of the system. The results of longterm charge performance test shows that the characteristic charge efficiency is 63.7%, which is higher than those of the conventional systems in Taiwan (about 51%).Boiling and condensations; Boiling heat transfer; Charge efficiency; Conventional systems; Experimental investigations; Heat transfer characteristics; Performance tests; Solar irradiation; Thermal Performance; Thermosyphons; Two-phase closed thermosyphon; Weather conditions; Heat transfer; Mixed convection; Phase transitions; Solar water heatersconference paper2-s2.0-84870490292