Formulation and Characterisation of Ternary Salt Based Solutions as Phase Change Materials for Cold Chain Applications

Cold energy storage has attracted considerable attention due to the increasing cooling demand, which provides an isothermal environment for users. Salt-water solutions are suggested as phase change materials (PCMs) for sub-zero applications because they have favourable thermoproperties. Binary salt based PCMs have been widely studied. However, choices are limited for PCMs with the phase change temperature between -15 and -30 °C for cold chains. In this paper, three ternary salt-water solutions (NaCl-NaNO3-H2O, NaCl-Na2SO4-H2O and NaCl-KCl-H2O) are formulated, characterised and compared, where NaCl solution is selected as the base material. The experimental results show that ternary salt-water solutions have lower phase change temperatures than the NaCl solution. NaCl-Na2SO4 solution has the highest phase change temperature of -21 °C, while NaCl-NaNO3 solution has the lowest value around -27 °C. The fusion heat of the ternary salt-water solutions depends on the components and salt ratio. NaCl-KCl solution has the highest fusion heat among NaCl solution and ternary PCMs, while NaCl-NaNO3 solution shows the lowest fusion heat. NaCl-Na2SO4 solution does not have a significant difference with NaCl solution due to the limited solubility. Finally, a new approach is proposed for formulating a set of ternary salt based PCMs, which helps to bridge the gap in this temperature range for cold chain applications.