Investigation On Heat Transfer Of Nanofluids

The main subject of this paper is the study of the anomalous thermal conductivity enhancement and the mechanism of thermal transport behavior in nanofluids.In 1995, a new class of heat transfer fluids called "nanofluids" was proposed by Choi from Argonne National Laboratory. Nanofluids is defined as a kind of composite material in which metallic or nonmetallic particles are randomly embedded in fluids. Nanofluids are expected to exhibit heat transfer properties superior to those of conventional heat transfer fluids.The purpose of this paper is to theoretically demonstrate the feasibility of the anomalous thermal conductivity enhancement in nanofluids. We aim at the effects of multipolar interaction, the particle shape, the interfacial nanolayer, the interfacial thermal resistance on the effective thermal conductivity enhancement.1.The effective thermal conductivity of carbon nanotube based nanofluidsBy taking into account the physical anisotropy, geometrical anisotropy and the effect of interfacial thermal resistance, we generalize differential effective medium approximation to investigate the thermal conductivity of carbon nanotube based nanofluids. We find that for spherical particles (i. e., L_z=1/3), the effective thermal conductivity of the composites achieves minimum. When the granular shape deviates from the spherical one, the effective thermal conductivity will be increased regardless of the prolate (L_z<1/3) or oblate (L_z>1/3) one. Therefore, the adjustment of the particle shape is really helpful to achieve appreciable enhancement of the thermal conductivity. On the other hand, large thermal resistance results in an energy loss and subsequently leads to a degradation in the effective thermal...