Experimental Investigation of Average Nusselt Number Variations in a Heat Pipe-Evacuated Tube Solar Collector due to Presence of Acetone-Graphene Nanofluid

This study investigates the enhancement of thermal performance in Evacuated Tube Solar Collectors (ETCs) by integrating graphene nanoparticles into the heat transfer fluid. Improvement the efficiency of ETCs is crucial for maximizing solar energy utilization, particularly in regions with diverse climatic conditions. To achieve this, we conducted experiments comparing the thermal performance of the ETC under two conditions: with and without graphene nanoparticles, and at varying flow rates of condenser water (۵, ۱۰, ۱۵, and ۲۰ L/h) in an open space in Babol, northern Iran, over two periods in August ۲۰۲۲. Measurements included ambient temperature, input and output water temperatures, heat pipe temperature, and water flow rate. Key performance indicators, such as the average Nusselt number, useful heat output, and convection heat transfer, were calculated. The results indicate that the Nusselt number increased by ۱۰.۶۴% and overall thermal performance improved when utilizing the acetone-graphene nanofluid at a flow rate of ۲۰ L/h under vacuum conditions (-۰.۶ bar) with a volume fraction of ۰.۰۸% nanoparticles. This work demonstrates a significant enhancement in thermal energy storage capabilities of ETCs, showcasing the potential of nanofluids in solar thermal applications, thereby contributing novel insights into the engineering optimization of solar collectors.

کلیدواژه ها:

Evacuated tube solar collector ، Nanoparticle ، Nusselt Number ، Phase change ، thermal conduction