Nitrate based high temperature nano-heat-transfer-fluids: formulation & characterisation

This work relates to the development of high temperature heat-transfer-fluid with enhanced specific heat capacity using nano-particle additives. A eutectic mixture of nitrate (60 wt% NaNO3 & 40 wt% KNO3) was produced through ball-milling and characterised on DSC, TGA, Rheometer. The results obtained showed that the salt mixture melted at 221°C with a heat of fusion of 97 J/g. Onset of melting was seen at 215°C whilst crystallisation started at 219°C, reaching a solid state below 217°C with an enthalpy of 97 J/g. Displaying very little overcooling, the salt showed specific heat capacity of 1.41 J/[°C*g] at 260°C to 1.44 J/[°C*g] at 440°C with viscosity values changing from 4.8 cP at 250°C to 1.7 cP at 450°C for this Newtonian fluid. Thermal decomposition of the salt showed that it was stable up to 550°C. The addition of nano-particles displayed an overall positive effect toward the specific heat capacity enhancing the latter whilst reducing the onset of melting due to increased entropy. The addition of 0.1, 0,5 and 1.0 wt% copper oxide gave the best results with increase of 10.5%, 9,2% and 8,5% in specific heat capacity respectively. SEM analysis of the samples showed that the nano-particles clearly disrupted the crystallisation structure showing a rougher organisation. Rheological tests on 0.1 wt% CuO demonstrated a slight rise in viscosity due to the addition of nano-particles. The stability of 0.1 wt% CuO was tested in large scale rigs (>1.0 kg) and demonstrated that sedimentation of nano-particles did occur. Different manner of dispersion were tested and revealed that they each affected the specific heat capacity differently with some causing negative enhancements whilst others were positive. The method of production did not affect the specific heat capacity values, and current theories point toward the formation of liquid nano-layers as a reason toward this increase

Rheological Analysis of Binary Eutectic Mixture of Sodium and Potassium Nitrate and the Effect of Low Concentration CuO Nanoparticle Addition to Its Viscosity

This paper is focused on the characterisation and demonstration of Newtonian behaviour of salt at both high and low shear rate for sodium and potassium nitrate eutectic mixture (60/40) ranging from 250 °C to 500 °C. Analysis of published and experimental data was carried out to correlate all the numbers into one meaningful 4th order polynomial equation. Addition of a low amount of copper oxide nanoparticles to the mixture increased viscosity of 5.0%–18.0% compared to the latter equation

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

In this study, TiO2 nanoparticles (average particle size 16 nm) were successfully produced in molten salt phase and were showed to significantly enhance the specific heat capacity of a binary eutectic mixture of sodium and potassium nitrate (60/40) by 5.4 % at 390 °C and 7.5 % at 445 °C for 3.0 wt% of precursors used. The objective of this research was to develop a cost-effective alternate method of production which is potentially scalable, as current techniques utilized are not economically viable for large quantities. Enhancing the specific heat capacity of molten salt would promote more competitive pricing for electricity production by concentrating solar power plant. Here, a simple precursor (TiOSO4) was added to a binary eutectic mixture of potassium and sodium nitrate, heated to 450 °C, and cooled to witness the production of nanoparticles

Mechanical Dispersion of Nanoparticles and Its Effect on the Specific Heat Capacity of Impure Binary Nitrate Salt Mixtures

In this study, the effect of nanoparticle concentration was tested for both CuO and TiO2 in eutectic mixture of sodium and potassium nitrate. Results showed an enhancement in specific heat capacity (Cp) for both types of nanoparticles (+10.48% at 440 °C for 0.1 wt % CuO and +4.95% at 440 °C for 0.5 wt % TiO2) but the behavior toward a rise in concentration was different with CuO displaying its highest enhancement at the lowest concentration whilst TiO2 showed no concentration dependence for three of the four different concentrations tested. The production of cluster of nanoparticles was visible in CuO but not in TiO2. This formation of nanostructure in molten salt might promote the enhancement in Cp. However, the size and shape of these structures will most likely impact the energy density of the molten salt

Supra-normal skills in processing of visuo-auditory prosodic information by cochlear-implanted deaf patients

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中高温储热材料的研究现状与展望

开发中高温储热材料及其制备方法是储热技术发展的关键之一。本文结合中高温储热材料的分类、特点、应用及存在的问题对中高温储热材料的研究进展进行了综述,主要包括显热储热材料、热化学储热材料以及潜热储热材料。探讨了复合结构储热材料及其制备工艺,进一步介绍了其最新研究进展,并对中高温储热材料的下一步研究进行了展望,提出开发高性能纳微复合结构储热材料是未来研究的重点