Experimental investigation of graphene oxide nanofluid on heat transfer enhancement of pulsating heat pipe

Pulsating heat pipes (PHPs) are heat transfer devices which are widely utilized in electronic devices and energy systems. Improvement in thermal performance of PHPs will lead to higher heat transfer capacity and enhancement in the efficiency of systems which PHPs are applied. In this study, an experimental investigation was performed on the thermal performance of a pulsating heat pipe by applying graphene oxide nanofluid as working fluid. Four concentrations of graphene oxide (0.25, 0.5, 1, and 1.5 g/lit) in water as base fluid were used in the PHP. Results indicate that adding graphene oxide sheets increased thermal conductivity and viscidity of the base fluid. Moreover, utilizing graphene oxide can decrease thermal resistance of PHP up to 42%. In addition, high concentration (1.5 g/lit) of the nanofluid worsen thermal performance of the PHP in comparison with pure water which is attributed to increase in dynamic viscosity of nanofluid. Finally, a regression model is proposed in order to compare effects of heat input and concentration of nanofluid on thermal resistance mathematically.