Contributory effect of diffusive heat conduction and Brownian motion on thermal conductivity enhancement of nanofluids
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Contributory effect of diffusive heat conduction and Brownian motion on thermal conductivity enhancement of nanofluids SAYANTAN MUKHERJEE1 , PURNA CHANDRA MISHRA1 and SHANTA CHAKRABORTY1
,∗ ,
PARITOSH CHAUDHURI2,3
1 Thermal
Research Laboratory, School of Mechanical Engineering, Kalinga Institute of Industrial Technology, Bhubaneswar 751 024 , India 2 Institute for Plasma Research, Bhat, Gandhinagar 382 428, India 3 Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, India ∗ Corresponding author. E-mail: [email protected] MS received 12 April 2020; revised 1 June 2020; accepted 1 July 2020 Abstract. The effect of diffusive heat conduction and Brownian motion on the enhancement of thermal conductivity in nanofluids is presented here. Al2 O3 and TiO2 nanofluids were prepared at four different wt. fractions of 1%, 0.5%, 0.1% and 0.05% and their thermal conductivity values were measured over temperatures ranging from 25 to 55◦ C for every 10◦ C interval. The thermal conductivity of nanofluids increased with the increase in concentration and temperature. Diffusive thermal conduction and Brownian motion contribute to thermal conductivity enhancement. However, diffusive heat conduction has major contribution to thermal conductivity enhancement in nanofluids. The thermal boundary resistance was found to be increasing with wt. fraction and decreasing with temperature elevation. Finally, a correlation is presented using group method of data handling (GMDH) neural network to predict the thermal conductivity of nanofluids. Keywords. Nanofluids; nanoparticles; thermal conductivity; Brownian motion; diffusion; neural network. PACS Nos 44.10.+i; 05.40.Jc; 84.35.+i; 44.35.+c; 43.35.Ac
1. Introduction In the present era, energy-saving technology is the need of the hour and augmentation of heat transfer is a means to achieve this. In order to improve the heat transfer, dispersion of non-organic nanoparticles of high thermal conductivity in different cooling media has been studied by many researchers. Investigations in various engineering fields such as heat exchanger, microelectronics, automotive, biomedical, nuclear sectors and process engineering have proved the potential of nanofluids for better thermal performance of industrial equipments. Nanofluids are colloidal dispersions of metallic and non-metallic nanoparticles in water, ethylene glycol (EG), oil, etc. After the pioneering work of Choi and Eastman [1], innumerable studies had been performed to explore the heat transfer and performance analysis of nanofluids. Available works of literature show that thermal conductivity of nanofluids is higher than that of the base fluids [2,3]. The enhancement in thermal conductivity of nanofluids has 0123456789().: V,-vol
been attributed to the occurrence of several phenomena in the nanofluids. Following is a review on the effect of various parameters on the thermal conductivity of nanofluids. Lee et al [4] measured the thermal conductivity of Al2 O3 –water and CuO–water nanofluids. They r
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