Abstract
There is no consensus on the effect of nanoparticle (NP) addition on the specific heat capacity (SHC) of fluids. In addition, the predictions from the existing model have a large discrepancy from the measured SHCs in nanofluids. We show that the SHC of the molten salt-based alumina nanofluid decreases with reducing particle size and increasing particle concentration. The NP size-dependent SHC is resulted from an augmentation of the nanolayer effect as particle size reduces. A model considering the nanolayer effect which supports the experimental results was proposed.
Highlights
While nanofluids, i.e., solvents doped with suspended nanoparticles (NPs), show enhanced thermal conductivities [1,2,3,4,5], the effect of nanoparticle addition on the specific heat capacity (SHC) of the fluids does not provide consistent findings in previous studies [6,7,8,9,10,11,12]
The SHCs of the NPs, molten salt, solid salt doped with NPs, and nanofluids were measured using differential scanning calorimetry (DSC, Model Q20, TA Instrument, New Castle, DE, USA and Model 7020 of EXSTAR, Hitachi High-Tech Science Corporation, Tokyo, Japan)
The SHCs were taken from the average of at least three measurements, and the error bars shown in the figure are the stand errors of these measurements
Summary
I.e., solvents doped with suspended nanoparticles (NPs), show enhanced thermal conductivities [1,2,3,4,5], the effect of nanoparticle addition on the specific heat capacity (SHC) of the fluids does not provide consistent findings in previous studies [6,7,8,9,10,11,12]. Das and co-workers [6,7,8] found reduced SHCs of nanofluids consisting of silicon dioxide, zinc oxide, and alumina NPs, respectively, dispersed in a mixture of water and ethylene glycol as compared to that of the base fluid. Zhou and Ni [9] found a reduced SHC of the water-based alumina nanofluid, and a similar decrease of SHC with increasing particle concentration was observed. Studies [6,10,11,12] found a large discrepancy between their experimental results and the predictions from the existing model [13]: 1⁄4
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