Some Studies On Heat Transfer and Pressure Drop Characteristics of Nanofluids

Abstract

Nanofluids are suspensions of nanometer-sized solid particles in base fluids which have been proposed as a route for surpassing the performance of heat transfer fluids. The heat transfer and pressure drop characteristics of nanofluid is being studied in this thesis work. Various aspects of nanofluid including synthesis of nanofluid, applications, experimental and analytical studies on the thermal conductivity, viscosity, density and heat transfer coefficient have been carried out.

For nanofluids, nanoparticles of Alumina (Al2O3) and carbon nanotubes (MWCNT) and distilled water is used as base fluid. The volume fractions of nanoparticles used are 0.1% and 0.50%. The Thermal conductivity is measured by KD2 pro thermal property analyzer, viscosity and density is measured by Ubbelohde viscometer and pycnometer, respectively. Heat transfer coefficient and pressure drop is measured by using an experimental setup at various flow rates and power inputs for distilled water, 0.1 volume% and 0.5 volume% alumina/distilled water nanofluid. Reynolds number and Nusselt number have also been calculated for the same above.

Results show that the alumina/distilled water nanofluid has a good stability while MWCNT/distilled water nanofluid after using a surfactant is not stable for more than 2 hours. Therefore, for further work alumina/water nanofluid is selected. Thermal conductivity is increasing with increase in temperature and also with particle concentration. Density and viscosity is decreasing with temperature but increasing with increase in particle concentration.

The temperatures of nanofluids, surface temperatures of pipe and pressure drop of nanofluids are measured at steady state for different flow rates and power inputs. The heat transfer coefficients and friction factors are calculated for above experimental data. With increase in flow rate and power input, heat transfer coefficient of 0.1 volume % and 0.5 volume % of alumina/water nanofluid is much higher than that of distilled water. Heat transfer coefficient is increasing with increase in flow rate and particle concentration. Pressure drop of distilled water is higher than that of alumina/distilled water nanofluid but it is increasing with increase in particle concentration.