Heat Transfer Mechanisms In Nanofluids Research Articles

Numerical Modeling of Thermophoresis and Diffusiophoresis in Water-Alumina Nano Fluids

Analysis of major heat transfer mechanisms in nanofluids specifically, thermophoresis and diffusiophoresis under pool boiling condition is attempted in this paper. Basic approach of the study tries to correlate thermophoresis in nanofluids to the behavior of rigid particles in gases. Ultimate objective of the study is to elucidate the thermophoresis/diffusiophoresis mechanism in nanofluids using thermophoretic velocity and viscosity of nanofluids. Thermophoretic velocity of water-alumina nanofluid analyzed in this study is assumed to be inversely proportional to fluid viscosity. Experiments and Computational Fluid Dynamics (CFD) tool are used for analyzing the effects of thermophoresis and diffusiophoresis on the heat transfer enhancement process. The numerical model considered for the study is a (2-D) rectangular container with the dimensions of the experimental set-up and a stainless steel heater inside it. Energy equation constituent of ANSYS Fluent is solved using a pressure based implicit solver and appropriate boundary conditions to obtain the temperature distribution pattern of the model. SIMPLE is used as the pressure correction method with Gauss-Siedel iterative method. Numerical simulation results for temperature distribution are validated using experimental readings. Thermophoretic velocity outputs derived from numerical simulation show significant movement of nanoparticles very close to realistic values. However, numerical results of viscosity, specific heat and diffusion coefficient of nanofluids were found to deviate from the results of the experiments. The dependency effect of these parameters needs further attention.

Heat Transfer Mechanisms in Nanofluids: A Review

Heat Transfer Mechanisms in Nanofluids: A Review

Theoretical Investigation Heat Transfer Mechanisms in Nanofluids and the Effects of Clustering on Thermal Conductivity

Theoretical Investigation Heat Transfer Mechanisms in Nanofluids and the Effects of Clustering on Thermal Conductivity

Heat Transfer Mechanisms and Clustering in Nanofluids

This paper surveys heat transfer in nanofluids. It summarizes and analyzes the theories regarding heat transfer mechanisms in nanofluids, and it discusses the effects of clustering on thermal conductivity. The heat transfer associated with conduction is presented through various experiments followed by a discussion of the theories developed. Relationships between thermal conductivity and various factors such as temperature, concentration, and particle size are also displayed along with a discussion on clustering. There is a brief discussion on convection where the number of studies is limited. There is research currently being performed on the manipulation of the properties governing the thermal conductivity of nanofluids—the particle size, shape, and surface area. Other factors that affect heat transfer are the material of the nanoparticle, particle volume concentration, and the fluid used. Although the interest in this relatively new class of fluids has generated many experimental studies, there is still disagreement over several aspects of heat transfer in nanofluids, primarily concerning the mechanisms behind the increased thermal conductivity. Although nanoparticles have greatly decreased the risks, there is still evidence of unwanted agglomeration which causes erosion and affect the overall conductivity. Research is currently being conducted to determine how to minimize this unwanted clustering.