Abstract
An experimental study was undertaken to assess the heat-transfer coefficient (HTC) of graphene nanoplatelets-pentane nanofluid inside a gravity-assisted heat pipe (HP). Influence of various parameters comprising heat flux, mass fraction of the nanoparticles, installation angle and filling ratio (FR) of the working fluid on the HTC of the HP was investigated. Results showed that the HTC of the HP was strongly improved due to the presence of the graphene nanoplatelets. Also, by enhancing the heat flux, the HTC of the HP was improved. Two trade-off behaviors were identified. The first trade-off belonged to the available space in the evaporator and the heat-transfer coefficient of the system. Another trade-off was identified between the installation angle and the residence time of the working fluid inside the condenser unit. The installation angle and the FR of the HP were identified in which the HTC of the HP was the highest. The value of installation angle and filling ratio were 65° and 0.55, respectively. Likewise, the highest HTC was obtained at the largest mass fraction of the graphene nanoplatelets which was at wt. % = 0.3. The improvement in the HTC of the HP was ascribed to the Brownian motion and thermophoresis effects of the graphene nanoplatelets.
Highlights
With the continuous advancement and development in the structure of the cities, demand for new technologies and, as a result, energy has increased [1]
Their results demonstrated that the thermal resistance of a heat pipe (HP) can be diminished by 42%, while thermal conductivity and viscosity both increased when nanofluid was employed in the HP
The temperature of the evaporator is relatively close to the boiling temperature of pentane, there is a potential for incipience of the boiling heat transfer in the evaporator section
Summary
With the continuous advancement and development in the structure of the cities, demand for new technologies and, as a result, energy has increased [1]. Hamid et al [6] experimentally analyzed the efficacy of TiO2 -SiO2 /water-EG nanofluid on the HTC of a HP They found the heat-transfer efficiency can be improved by 254.4%, whereas the friction factor was augmented by 76%, compared to the base fluid. HTC of pulsating HP (PHP) using 0.25–1.5 g/lit of GO/H2 O nanofluids was experimentally studied by Nazari et al [30] Their results demonstrated that the thermal resistance of a HP can be diminished by 42%, while thermal conductivity and viscosity both increased when nanofluid was employed in the HP. A thermosyphon HP is employed and effect of several operating parameters such as the applied thermal energy to the evaporator, the installation tilt angle, the filling ratio (FR) of the working fluid and the mass fraction of the nanofluid on the HTC of the evaporator and the efficiency of the HP is experimentally studied. Due to the large vapor pressure and plausible thermal performance, n-pentane/graphene was selected for the present study
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