Xiaolan Wei

Performance of Molten Salts Phase Change Materials

Heat transfer medium in solar thermal power stations are used by molten salts materials. Quaternary molten salts which were composed of potassium nitrate, sodium nitrite, sodium nitrate when adding 5%, 10%, 15% additive A, additive B, additive C respectively were prepared. Thermal stability and thermal cycling analysis of molten salts, XRD and DSC tests showed molten salt with 5% additive A had higher thermal stability. Its optimum operating temperature would be increased to 550°C from 500°C. This kind of heat transfer medium had high phase change latent heat and low melting point. So it could reduce the size of system and requirement for energy. The efficiency of its using energy was higher and the effect of energy saving was better. Besides, this kind of molten salt may also supply theoretical prediction for molten salts synthesis and basic method for project application.

Enhanced specific heat capacity of binary chloride salt by dissolving magnesium for high-temperature thermal energy storage and transfer

Thermal energy storage and transfer technology has received significant attention with respect to concentrating solar power (CSP) and industrial waste heat recovery systems. In this study, we report a novel method to synthesize nanofluids by dissolving magnesium metal in NaCl–CaCl2 eutectic molten salt to enhance the specific heat capacity without the conventional agglomerate effect of nanoparticles. It was found that the solubility of magnesium in the binary molten salt reached 0.075% and 0.185% at 550 °C and 750 °C, respectively. Magnesium did not react with the molten salt but dissolved in it in the form of liquid magnesium metal and did not change the melting temperature of the binary molten salt. The liquid specific heat capacities of nanofluids containing 1.0 wt% and 2.0 wt% magnesium were 1.12 J g−1 °C−1 and 1.15 J g−1 °C−1, which were 105.66% and 108.49% higher than those of the binary chloride salts. Magnesium decreased the upper temperature limit and thermal stability, and the nanofluid was thermally and chemically stable after 50 heating/cooling cycles. These results implied that the resulting nanofluid is a promising candidate material for high-temperature heat storage and transfer applications.

New molten salt heat transfer fluid for solar thermal power plant

In order to remove the oxidation of nitrite salt and reduce the cost of lithium nitrate relative to previously available materials, new molten salt heat transfer fluid (KCl-KNO3-NaNO3) is prepared by static fusion method. Eutectic point and component of molten salt are determined firstly from phase diagram that is calculated by using conformal ionic solution (CIS) theory. Then thermal stability of this mixture is investigated by thermo-gravimetric analysis (DSC-TGA) device. Experimental results show the agreement between measurements and calculations is found to be very good. This kind of molten salt has a lower melting point (210°C), compared to Solar Salt (220°C). It is thermally stable at temperatures up to 500°C, and may be used up to 550°C for short periods. So that was suitable for heat transfer and thermal storage medium.