Demonstration of plausible application of gallium nano-suspension in microchannel solar thermal receiver: Experimental assessment of thermo-hydraulic performance of microchannel

The present study experimentally investigates the potential application of a liquid metal enriched with aluminum oxide nanoparticles in a microchannel, which can have further applications in designing the next generation of solar thermal receivers equipped with microchannel fluid passages. The gallium nano-suspensions were prepared at mass fractions of 5%, 10% and 15% of aluminum oxide in gallium and were utilized in a copper-made rectangular microchannel liquid block at 200 °C. Effects of different operating parameters such as heater heat flux, mass fraction of nanoparticles and peristaltic flow rate on the overall heat transfer coefficient, value of the pressure drop and thermo-hydraulic performance index of the microchannel were experimentally investigated. Results showed that gallium nano-suspension offers a great potential for cooling the surface of the microchannel at high heat flux condition. The highest thermal performance index of 3.5 and 2.9 were achieved for the flow in laminar and turbulent regimes at mass fraction of 10%. Likewise, heat flux and peristaltic flow rate plausibly enhanced the heat transfer coefficient, however, for the mass concentration, the thermo-hydraulic performance was decreased at wt% = 15, due to the augmentation in the viscosity and agglomeration of aluminum oxide nanoparticles within the gallium, which was attributed to the increase in friction forces between layers of gallium.