Experimental study of forced convection and subcooled flow boiling heat transfer in a vertical annulus using different novel functionalized ZnO nanoparticles

摘要: Abstract In this study the effect of different ZnO-nanoparticles synthesis methods on thermal performance prepared nanofluids has been investigated. The accomplished in two parts. At first, four types ZnO nanoparticles were synthesized by sol-gel hydrothermal method. surfaces these functionalized and then characterization tests performed. second step, forced convective subcooled flow boiling heat transfer coefficients water-based experimentally studied. experiments conducted a closed loop which working fluid passed through vertical cylindrical annulus. performed at levels operating variables such as subcooling temperature (30–50 °C), volume rate (2–4 L/min), flux (8–110 kW/m 2 ) nanoparticle concentration (0.005–0.02 vol%). results indicated that nanorod-nanotube surface modified silica gel UV radiation had best performance.