No abstract

Thermal conductivity of a heat transfer fluid plays a significant role in improving the heat transfer performance of a heat exchanger. In this work, experiments were performed in a natural convection heat transfer apparatus by mixing homogenized Al2O3 nanoparticles in a base fluid of water-ethylene glycol mixtures. The effects of heat input, nanoparticle volume content in the base fluid, and ethylene-glycol volume content in the base fluid on thermal conductivity of the nanofluid were analyzed. Based on results obtained by MINITAB? design software (factorial design matrix), 16 experimental runs were performed with the lower and higher levels of input factors. The levels for heat input were 10 and 100 W; for nanoparticle volume content in the base fluid 0.1 and 1 vol.% and for the base fluid composition 30 and 50 vol.% of ethylene glycol in water. From the obtained experimental results, a Pareto chart, normal probability plot, contour plot and surface plot were drawn. Based on the results, a new correlation was proposed, and predictions were compared with the experimental results. From the study, the maximum thermal conductivity value 0.49 W m-1 K-1 was observed at a nanoparticle volume content in the base fluid of 1.0 vol.%, ethylene glycol volume content in the base fluid of 30 vol.% and heat input of 100 W.

The experimental study of heat transfer coefficient of nanofluid plays a significant role in improving the heat transfer rate of the heat exchanger. The research was conducted in a natural convection heat transfer apparatus by suspending Al2O3 nanoparticle in a base fluid of Water-Ethylene glycol mixture. The effects of heat input (A), nanoparticle volume fraction (B), and base fluid concentration (C) on experimental heat transfer coefficient (hexpnf) were studied. By the results obtained by MINITDesign software 23 full factorial design matrix, 16 experimental runs were performed with the lower and higher level of input factors. The levels for heat input are 10 and 100 W; nanoparticle volume fraction is 0.1 and 1 volume% and for base fluid concentration is 30 and 50 volume% of Ethylene Glycol in water. From the obtained experimental results residual plots, Pareto chart, contour plot and 3D surface plots were drawn. It can be found from the study that the experimental heat transfer coefficient showed highest enhancement with high level of nanoparticle volume fraction and moderate enhancement with high level of heat input and slight enhancement with base fluid concentration.

Improving heat transfer performance of conventional fluid creates significant energy savings in process Industries. In this aspect, experimental study was performed to evaluate the heat transfer performance of Fe2O3-Water (W)-Engine Oil (EO) nanofluid at different concentrations and different hot fluid inlet temperatures in a plate heat exchanger. Experiments were conducted by mixing Fe2O3 nanoparticle (45 nm) in a base fluid of water-engine oil mixture with volume fractions of 5%EO + 95%W and 10%EO +90%W. Main aim of the present study is to assess the impact of variations in nanoparticle volume fraction and hot fluid inlet temperature on the heat transfer performance of prepared nanofluid. Based on the experimental results, convective heat transfer coefficient, Reynolds, Prandtl and Nusselt number were determined. Result shows that at the hot fluid inlet temperature of 75?C, the increase in Nusselt number and convective heat transfer co efficient are optimum at 0.9 vol. % nanoparticle for both the base fluid mixtures. The increase in heat transfer coefficient is because of the Brownian motion (increasing thermal conductivity) effect, motion caused by temperature gradient (Thermo-phoretic) and motion due to concentration gradient (Osmophoretic). If the volume fraction of nanoparticle increases then Reynolds number increment is higher than Prandtl number decrement, which augments Nusselt number as well as convective heat transfer coefficient.