Effect of nanofluids on thin film evaporation in microchannels |
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Authors: | Jun-Jie Zhao Yuan-Yuan Duan Xiao-Dong Wang Bu-Xuan Wang |
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Affiliation: | (1) Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing, 100084, China;(2) State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing, 102206, China; |
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Abstract: | A thin film evaporation model based on the augmented Young–Laplace equation and kinetic theories was developed to describe
the nanofluid effects on the extended evaporating meniscus in a microchannel. The nanofluid effects include the structural
disjoining pressure, a thin porous coating layer at the surface formed by the nanoparticle deposition and the thermophysical
property variations compared with the base fluid. The results show that the nanofluid thermal conductivity enhancement mainly
due to the Brownian motion tends to greatly increase the liquid film thickness and the thin film heat transfer. The structural
disjoining pressure effect tends to enhance the nanofluid spreading capability and the thin film evaporation. The nanoparticle-deposited
porous coating layer improves the surface wettability while significantly reducing the thin film evaporation with increasing
layer thickness due to the thermal resistance across this layer. The nanofluid thermal conductivity enhancement together with
the structural disjoining pressure effect can not counteract the thermal resistance effects of the porous coating layer when
the coating layer thickness is sufficiently large. |
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Keywords: | |
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