An experimental study was performed to determine the performance of thermosyphon Solar Water Heater(SWH) system under various conditions using R744 (CO2) as the working fluid. The uniqueness of the system was the use of carbon dioxide as a working fluid; which is one of the most promising alternative natural refrigerants. Literature shows that most of the CO2 utilized SWH systems are active systems. In this study, an attempt has been made to design and fabricate a simple thermosyphon solar water heater using supercritical CO2 as working fluid to investigate for its feasibility in various operating conditions when exposed to solar adverse regions like those found in North Dakota, USA. The effect of various parameters such as storage volume, inlet tank temperature etc. on the overall performance of a CO2 assisted SWH system has been evaluated. The results indicate that, the measured collector (ηcol) and heat recovery efficiencies (ηRE) were calculated around 65% and 55% respectively.

Keywords : Solar Water Heating, Thermosyphon, Refrigerant, R744, Evacuated Tube Collector, Heat Recovery Efficiency