Investigation of Thermal Performance of Cylindrical Heat Pipe Using Silver Nanofluid. Part I: Experimental Evaluation

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Cylindrical heat pipes are widely used in various applications to transfer the heat effectively and efficiently. Besides parameters of heat pipe, its thermal performance mainly depends on the characteristics of working fluid also. Recently, various nanofluids have been considered as the most promising working fluid in different heat transfer applications. In the present paper thermal performance of cylindrical heat pipe using silver nanofluid as working fluid has been experimentally evaluated. Extensive experiments have been performed on cylindrical copper heat pipe having two-layer screen mesh filled with silver nanofluid in filling ratio of 40% with a vacuum of 10−3 torr. The thermal performance of heat pipe has been evaluated in terms of thermal resistance, thermal conductivity and overall heat transfer coefficient by varying parameters such as size of nanoparticle, concentration of nanoparticle, angle of inclination of heat pipe, heat load on heat pipe, average evaporator temperature and average condenser temperature to propose the best combination of parameters. The results indicate that the cylindrical heat pipe kept at 45° inclination angle and filled with silver nanofluid of 35 nm size of silver nanoparticle in 0.3% volume concentration yields higher thermal performance when it is operated at 120–140 W heat input. Thus, the cylindrical heat pipe under study is suitable for applications which require operation of heat pipe at some angles, such as cooling of high-wattage LED street lights.