Preparation of a low-temperature nanofluid phase change material: MgCl2–H2O eutectic salt solution system with multi-walled carbon nanotubes (MWCNTs)

Abstract

Abstract With the rapid development of cold chain logistics, there is a growing demand for refrigerated transportation equipment for low-temperature products, such as fresh products, chemical supplies and medical vaccines. For some products with low transport temperatures, phase change materials (PCMs) from −10 C to −40 °C are still to be developed. This paper focuses on the development of a low phase transition temperature nanofluid phase change materials (NFPCMs) with excellent thermodynamic properties, simple preparation method and low cost. 23 wt% MgCl2 eutectic solution was used as phase change material in the NFPCMs, in which Multi-walled carbon nanotubes (MWCNTs) and nucleating agents play a supportive role to reduce supercooling degree. At that, the addition of MWCNTs increases the thermal conductivity and thickener xanthan gum (XG) can prevent phase separation and agglomeration. The NFPCM with 1 wt% MWCNTs has a phase transition temperature of −34.54 °C, a phase transition enthalpy of 146.9 kJ kg−1, and thermal conductivity of 0.5344 W (m k)−1. Also, under the synergistic action of MWCNTs with CaCl2 and Ca(OH)2, the supercooling degree of NFPCM decreased to 1.82 °C, which was 89% lower than that of the pure eutectic salt solution. Furthermore, the NFPCMs still showed excellent stability after 400 thermal cycles. The results show that the NFPCMs has high latent heat, higher thermal conductivity, low supercooling degree and excellent thermal stability, which makes it have practical application value and broad development prospects in the field of the cold chain.