Paraffin/chitosan composite phase change materials fabricated by piercing-solidifying method for thermal energy storage

Honghua Qi,Kunjie Wang,Yi Wang,Ting Zhang,Deyi Zhang

doi:10.1063/1.5140582

Honghua Qi, Kunjie Wang + Show 3 more

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https://doi.org/10.1063/1.5140582

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Abstract

To study the effects of emulsifier content on the structure and thermal properties of encapsulated phase change materials (PCMs), four kinds of paraffin/chitosan (CS) macroencapsulated PCMs with different emulsifier contents were fabricated via the piercing–solidifying method. The effects of emulsifier content on macro-profile, micromorphology, thermal energy storage properties, and thermal durability of the as-prepared composite, as well as the structure of the optimal capsules, were investigated. The results show that the non-spherical degree, average diameter, and compressive strength decreased first and then increased with increase in emulsifier content, resulting in thermal energy storage capacity’s increase at first and then its decrease. The optimal macro-capsules, fabricated at the critical micelle concentration of the emulsifier, present a regular spherical surface and microencapsulated paraffin wax inside. The paraffin content is as high as 85%, with a phase change latent heat of 112.6 J g−1 for melting and 118.7 J g−1 for solidification. The melting enthalpy and weight loss ratio of the optimal paraffin/chitosan composite after 600 heating/cooling cycles only changed to 0.71% and 1.17%, respectively. These results not only suggest that the piercing–solidifying method can be employed to fabricate macro-capsules with high heat storage performance and excellent thermal stability but also reveal that paraffin/CS can be used in thermal management at low temperature.

Highlights

Most of them exist as agglomerates of pure CS, which resulted in a lower heat storage capacity (Fig. 5)
A series of paraffin/CS macro-capsules were fabricated by the piercing–solidifying method, and the influence of emulsifier content scitation.org/journal/adv on the morphology and thermal properties of paraffin/CS was investigated
The results show that the emulsifier content has significant effects on the average diameter, non-sphere degree, compressive strength, and thermal energy storage performance

Summary

Introduction

Thermal energy storage (TES) plays an important role in renewable energy utilization systems because it can solve the mismatch problem between energy supply and demand, as well as effectively ease the pollution issues caused by excessive usage of fossil energy. Compared with other TES methods, latent heat thermal energy storage (LHTES) embedded with phase change materials (PCMs) is considered to be the most effective and promising technique because PCMs can absorb and release large amounts of heat during the process of melting or solidification with negligible phase transition temperatures. In consideration of these features, LHTES can be widely applied in building walls, smart textiles, automotive applications, and thermal management of electronic materials.9Solid–liquid PCMs are the commonly used medium in LHTES due to the advantages of high latent heat density and minor volume changes during the phase transition process, compared with liquid– gas and solid–gas PCMs. Among the investigated solid–liquidPCMs, paraffin has been widely used due to its safety, chemical inactivity, non-corrosiveness, and good thermal properties. leakage, frosting, and quick deterioration of thermal properties are the inherent defects of paraffin, which lead to the loss of PCMs, contamination of equipment, hysteresis of thermal response, and, restriction of its practical utilization. To eliminate these drawbacks, encapsulation was usually employed to avoid leakage, increase heat transfer area, and decrease the reaction possibility with an external environment during the phase change procedures. Compared with other TES methods, latent heat thermal energy storage (LHTES) embedded with phase change materials (PCMs) is considered to be the most effective and promising technique because PCMs can absorb and release large amounts of heat during the process of melting or solidification with negligible phase transition temperatures.. Compared with other TES methods, latent heat thermal energy storage (LHTES) embedded with phase change materials (PCMs) is considered to be the most effective and promising technique because PCMs can absorb and release large amounts of heat during the process of melting or solidification with negligible phase transition temperatures.4,5 In consideration of these features, LHTES can be widely applied in building walls, smart textiles, automotive applications, and thermal management of electronic materials.. Thermal stability can be boosted by microencapsulation due to the synergistic effect between core and shell materials.

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