EMD analysis on the impact of temperature, volume fraction and molecular weight on the thermal conductivity of water-based nanofluids

SR Krishnan and VNN Namboothiri, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 146, 1525-1537 (2021).

DOI: 10.1007/s10973-020-10134-x

The development of high-performance thermal systems for heat transfer enhancement is crucial since the reliability and performance of chips and processors are heavily dependent on the operating temperature. The space constraints also need to be simultaneously met. Miniaturization, optimum power consumption and enhancement in the efficiency of electronic systems can be achieved by the judicious selection of nanofluids. But the enhancement in thermal conductivity of nanofluids is dependent on a number of parameters such as volume fraction of nanoparticles, nanoparticle used, size and shape of the nanoparticle, base fluid used and temperature. For studying the impact of volume fraction, system temperature and weight of nanoparticle on thermal conductivity enhancement of water-based aluminium/aluminium oxide nanofluids, equilibrium molecular dynamics is applied. The numerical estimation of thermal conductivity is performed in the temperature range of 290-350 K for volume fraction ranging between 1 and 4%. From the analysis, it is observed that although there is a definite thermal conductivity enhancement for nanofluids when compared to water, an increase in volume fraction and temperature may not always result in a proportionate enhancement. At low temperatures, a nanofluid with a heavier nanoparticle and low volume fraction is effective, but the enhancement at higher temperatures and higher volume fractions is found to be more for a nanofluid having a lighter nanoparticle. Hence, in addition to temperature and volume fraction, weight of the nanoparticle is also a critical factor in the selection of nanofluids. For a given nanoparticle, there exist a particular temperature and volume fraction at which the nanofluid gives maximum heat transfer effectiveness. The base fluid used is also important as nanofluids exhibit a delayed convection onset when compared to base fluid, and the delay is more as volume fraction increases. Nanofluid is more effective in heat transfer only when its layer thickness is greater than the thickness required for convection to onset.

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