Development of sodium acetate trihydrate-ethylene glycol composite phase change materials with enhanced thermophysical properties for thermal comfort and therapeutic applications

Rohitash Kumar,Ambesh Dixit,Sumita Vyas,Ravindra Kumar

doi:10.1038/s41598-017-05310-3

Rohitash Kumar, Ambesh Dixit + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-05310-3

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Abstract

The heat packs using phase change materials (PCMs) are designed for possible applications such as body comfort and medical applications under adverse situations. The development and performance of such heat packs rely on thermophysical properties of PCMs such as latent heat, suitable heat releasing temperature, degree of supercooling, effective heat releasing time, crystallite size, stability against spontaneous nucleation in metastable supercooled liquid state and thermal stability during heating and cooling cycles. Such PCMs are rare and the available PCMs do not exhibit such properties simultaneously to meet the desired requirements. The present work reports a facile approach for the design and development of ethylene glycol (EG) and aqueous sodium acetate trihydrate (SAT) based composite phase change materials, showing these properties simultaneously. The addition of 2–3 wt% EG in aqueous SAT enhances the softness of SAT crystallites, its degree of supercooling and most importantly the effective heat releasing time by ~10% with respect to aqueous SAT material. In addition, the maximum heat releasing temperature of aqueous SAT has been tailored from 56.5 °C to 55 °C, 54.9 °C, 53.5 °C, 51.8 °C and 43.2 °C using 2%, 3%, 5%, 7% and 10 wt% EG respectively, making the aqueous SAT-EG composite PCMs suitable for desired thermal applications.

Highlights

The extreme low ambient temperature at high altitude regions adversely affects the health of inhabitants and may cause frostbite, hypothermia etc
The XRD pattern of aqueous sodium acetate trihydrate (SAT) is in good agreement with the reported monoclinic crystallographic structure with space group C2/c32
The reduced intensity is attributed to the geometrical effects, where smaller crystals have resulted in the out of phase diffracted radiation, and relatively lower intensity

Summary

Introduction

The extreme low ambient temperature at high altitude regions adversely affects the health of inhabitants and may cause frostbite, hypothermia etc. Phase change materials such as hydrated salts exhibit large degree of supercooling, which is not desirable for general heat storage applications such as building heating/cooling This property can be utilized for long-term storage of thermal energy at low ambient temperature and release it later at the time of demand by initiating the crystallization in the metastable supercooled liquid PCMs13, 14. Among such PCMs, sodium acetate trihydrate (SAT) has attracted attention because of its high latent heat of fusion ~250 kJ/kg, suitable melting temperature ~58 °C, large supercooling range, better thermal stability during charge/discharge cycles and most important, the low price[15,16,17,18,19,20]. In spite of such thermo-physical properties of SAT and potential applications in heating devices as explained schematically in Fig. 1, there are few challenges associated with SAT based PCM heat packs such as hard, lumped, big and sharp edges of SAT crystallites, unintentional nucleation in metastable supercooled liquid PCM at low ambient temperature (~0 °C), low heat retention time due to the fast crystal growth during solidification from metastable supercooled liquid state

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