A Simple Analytical Model for Specific Heat of Nanofluid With Tube Shaped and Disc Shaped Nanoparticles
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In this study we present a simple analytical model for estimating the specific heat capacity of nanofluids containing tube shaped and disc shaped nanoparticles dispersed in a solvent. The model includes the effect of an ordered liquid layer formed at the solid-liquid interface between a tube or disc shaped nanoparticle and the liquid phase. The size and thermo-physical properties of the ordered liquid layer are calculated based on the results of molecular dynamic (MD) simulation. The model is applied to nanofluid dispersed carbon nanotube (CNT) nanoparticles with tube shape in a liquid phase of alkaline metal carbonate salt eutectic mixture (Li2CO3:K2CO3 in 62:38 molar ratio). In addition, the specific heat of nanofluid with graphite nanoparticles with disc shape is calculated using the simple analytical model. The alkaline salt mixture as well as the corresponding nanofluid has potential applications as thermal energy storage (TES) material for solar thermal energy conversion. Hence, the specific heat is an important thermo-physical property for determining the thermal efficiency of the solar thermal energy system. To identify the effect of particle size and mass concentration, the specific heat capacity is plotted as a function of particle size and mass concentration. The experimental data is used to validate the simple analytical model for the effect of particle shape on the specific heat. The results show that the specific heat of nanofluid increases with the mass concentration of nanoparticles. Furthermore, nanoparticles with diameters less than 6 nm can cause anomalous enhancement in the specific heat of nanofluid. The results also show that tube shaped nanoparticles are more effective in enhancing the specific heat capacity of nanofluids than disc shaped nanoparticles due to the higher specific surface area of tube shaped nanoparticles compared to disc shaped nanoparticles of similar mass.
