Outdoor testing of an evacuated tube closed two phase thermosyphon solar water heater charged with Nano-fluid

Abstract

This paper reports the performance of two types of evacuated tube heat pipe solar water heater systems that have been experimented outdoors under the local meteorological conditions of the capital of Iraq. Tests were conducted using two systems made of the same materials but with different design specifications. To build each of the two trail system, a single evacuated tube to two phase thermosyphon is used to make the investigation of the experiments simpler. With the absence of loading conditions, experiments with the first system were conducted. Graphene water Nano-fluid (GW) was used as the working fluid in this system. The water storage tank system capacity was varied, to analyze the performance for different storage capacity. The system was operated with a flat reflector plate and without this reflector. A modified second system was built with a longer evaporator section for higher performance and with tank that enables hot water removed from it. The hot water from the storage tank was withdrawn intermittently and continuously. Graphene water (GW), Graphene acetone( GA) and distilled wate( d-W) were used as the working fluids in this second system. Energy stored at the water storage tank and overall efficiencies were calculated and found to be comparable to those obtained using natural circulation solar water heating systems. A comparison between the obtained Results and other works was made. The comparison showed that the present systems were just as good in performance. An improvement in the overall efficiency was found when operating the system under load conditions. This improved value is about 10% higher than that without load condition.