Enhancing the Specific Heat Capacity of Molten Salts for Heat Transfer Applications Using Nanoparticles

Abstract

Molten salts have physical properties that include thermal stability over a large temperature range, low vapor pressure at high temperature, and are nearly immune to radiological effects. Due to these favorable properties, molten salts are being considered as a promising candidate for next generation heat transfer fluids for use in generation IV nuclear reactors. One drawback of molten chloride salts thermo-physical properties is their low specific heat capacity (around 1.0–1.5 (J/(g×K)). It has been shown that addition of nanoparticles in molten salts leads to a large increasing in the specific heat capacity of these salts, once melted with the particles. The aim of this study is to investigate the effect that nanoparticles have on specific heat capacity of zinc potassium chloride solutions. The hollow carbon nanospheres (hCNS, outer diameter is 20–30 nm; wall thickness 7 nm) and zeolite nanoparticles (ZSM-5, size 10–30 nm) were chosen for this study. The colloidal solutions of ZnCl2–KCl (46 mol% KCl) eutectic melt (Tm.p. = 220 oC) with different amounts, 0.3 to 2 wt% of nanoparticles, were prepared by mechanical mixing of required amount of salt with nanoparticles at 350oC for at least 24 hours until stable colloidal solutions were formed. Specific heat capacity of the samples was measured using a differential scanning calorimeter (HDSC; PT1000, Linseis Inc.) under the argon atmosphere according to established literature procedures. Measurements were carried out between 250–350oC temperature region with 10oC/min temperature rate using platinum crucibles with platinum lids for containment. The obtained experimental results (fig. 1) demonstrate that specific heat capacity of ZnCl2–KCl eutectic melt increases with increasing amounts of both types of nanoparticles used to form the colloidal solution. Figure 1