Advances in Thermoregulating Textiles: Materials, Mechanisms, and Applications

Mid and high-temperature inorganic salts have limited applications due to their corrosiveness and low thermal conductivity. Shape-stabilized phase change materials (SSPCMs) can ease these issues. This study explored using dolomite, an affordable and abundant mineral with good thermal properties, in SSPCMs. We developed SSPCMs using raw and calcined dolomite at 700 °C, 750 °C, and 800 °C (700Do, 750Do and 800Do) as skeletal support materials (SSMs) and NaNO3-KNO3 as the phase change materials (PCMs). Calcined dolomites had a porous structure compared to raw dolomite (RawDo). 700Do, 750Do and 800Do require a minimum of 50 wt%, 40 wt% and 30 wt% to stabilize the shape of the sintered material by 100 cycles. RawDo was unsuitable for SSM during cycling. XRD confirmed chemical compatibility between components, and SEM showed an even distribution of SSMs within the PCMs. The thermal conductivity of SSPCMs ranged from 1.09 to 1.27 W/(m·K), compared to 0.52 W/(m·K) for NaNO3-KNO3. The NaNO3-KNO3 has a latent heat of about 110.60 J/g and a supercooling degree of 5.84 °C. The latent heat of SSPCMs depends on the proportion of SSMs, slightly lower than the theoretical value by 0.01 %–2.37 %, and the supercooling degree of SSPCMs varies between 4.75 °C and 6.25 °C. The SSPCMs were chemically stable with little latent heat change after 100 cycles, showing excellent cycling stability. The thermal decomposition temperature of SSPCMs containing 700Do was about 580 °C, while SSPCMs containing 750Do and 800Do exhibited a minor decomposition onset at around 380 °C, attributed to Ca(OH)2 decomposition. The best-performing SSPCM contained 30 wt% 800Do, offering a thermal conductivity of 1.27 W/(m·K) and thermal energy storage density of 359 kJ/kg in the 100–320 °C range. In general, calcined dolomite-based SSPCMs offer excellent thermal energy storage performance at a low cost compared to many SSPCMs.

Shape stabilized phase change materials based on different support structures for thermal energy storage applications–A review

Nitrile butadiene rubber (NBR) latex exhibits excellent tensile properties, chemical resistance, and thermal stability in applications such as gloves and safety shoes due to vulcanization. In this research work, attempts have been made to manipulate the vulcanization to produce thin and compact elastomeric NBR coating on myristic acid (MA) phase change material (PCM) to produce shape-stabilized PCM. The proposal for the use of latex-based elastomeric coating for PCM has been rarely considered in the literature due to a lack of understanding of the crosslink of elastomers. Thus, in this research, the effects of sulfur formulation on the coating performance of NBR on the PCM in terms of latent heat and thermal stability were determined. Leakage analysis indicates that the MA pellet coated with 0.5 phr of sulfur-cured NBR layer (MA/NBR-0.5) successfully eliminates the leakage issue. A tensile analysis revealed that a durable PCM coating layer must possess a combination of the following criteria: high tensile strength, ductility, and flexibility. Fourier transform infrared analysis (FTIR) and electron microscopy images showed the formation of thin, compact, and continuous NBR coating when 0.5 phr of sulfur was used. The further increment of sulfur loading between 1.0 and 1.5 phr causes the formation of defects on the coating layers, while non-vulcanized NBR layers seem to be very weak to withstand the phase-change process. The recorded latent heat values of melting and freezing of MA/NBR-0.5 are 142.30 ± 1.38 and 139.47 ± 1.23 J/g, respectively. The latent heat of the shape-stabilized MA/NBR-0.5 PCM is reduced by 32.24% from the pure MA latent heat density. This reduction is significantly lower than the reported latent heat reduction in shape-stabilized PCMs in other works. The thermal cycle test highlights the durability of the coated PCMs by withstanding up to 1000 thermal cycles (2.7 years) with less than 2% changes in latent heat value. Cooling performance test on photovoltaic (PV) module shows that the fabricated shape-stabilized PCM could reduce the temperature of the PV module up to 17 °C and increase the voltage generation by 7.92%. Actual performance analysis of shape-stabilized PCMs on the cooling of the PV module has been rarely reported and could be considered a strength of this work.

Review on Nanostructure Supporting Material Strategies in Shape-stabilized Phase Change Materials

A review on encapsulation techniques for inorganic phase change materials and the influence on their thermophysical properties

Latent heat storage with inorganic salts as phase change materials (PCM) is very attractive as these compounds can store a large amount of heat within a small temperature range in a small volume. However, subcooling, phase segregation, and low cycling stability are present in these materials, affecting its applications. One of the ways to reduce or eliminate these disadvantages is to encapsulate or stabilize the inorganic salts. In this work, one-step sol–gel technique was used to create new shape stabilized PCM (SS-PCM) with SiO2 as support material. Four pure salts, LiCl, LiNO3, LiCO3, and CH3COOLi·2H2O, were investigated to evaluate the potential of this sol–gel method, usually used with organic PCM, to obtain inorganic SS-PCM. IR spectroscopy confirmed the polymerization process during the sol–gel process, and show that no chemical reaction occurs between PCM and SiO2 support material, except for Li2CO3. XRD patterns for high salt content (60%) samples show occurrence of salt agglomerations. In addition, the water molecules loss for CH3COOLi·H2O during sol–gel process was observed in SS-PCM. The thermophysical characterization by DSC show that LiCl and LiNO3 properties were improved due to sol gel process, exhibiting higher cycling stability and lower subcooling value than the pure salts. The LiNO3 and LiCl SS-PCM present potential thermal energy storage applications. However, CH3COOLi·H2O and Li2CO3 did not demonstrate potential to be used as PCM under the studied condition.

Experimental study on phase transition behaviour of shape stable phase change material for application in vacuum insulation panel

Research on U-tube Heat Exchanger with Shape-stabilized Phase Change Backfill Material

Oleophobic modification of clay minerals to improve encapsulation ratios of shape-stabilized phase change materials: A universal method

Development of a novel alkali-activated slag-based composite containing paraffin/ceramsite shape stabilized phase change material for thermal energy storage

Model and Simulation on Thermal Performance of Shape-Stabilized Phase Change Material Floor

Thermal energy storage (TES) using solar energy is one of the most prominent techniques to store the energy and reduce to gap between energy demand and supply. There are many useful applications that can be fuelled by TES. Phase change materials (PCM) as TES materials are of great importance as far as the energy storage applications are concerned. However, there are various bottleneck problems with pure PCM like liquid phase leakage, low thermal conductivity, supercooling etc. To overcome this deficit, highly porous foam is used to improve the leakage problem of PCMs during phase transition. Additionally, nanoparticles and nucleating agent are the most commonly employed in-practice approaches to get rid of the issue of low thermal conductivity and supercooling, respectively. In addition, even after being subjected to multiple heat cycles, foam-stabilized PCM composites showed remarkable stability without being degraded. This paper discusses the major foams that has been incorporated with different PCMs along with their critical outcomes. This paper also discusses the significant uses of foam stable PCMs reported by several researchers. As a result of its high latent heat, good thermal conductivity, balanced chemical compatibility, and high thermal stability, the foam-stable PCM composite is a viable choice for thermal-energy management systems.

High temperature shape – Stabilized phase change materials obtained using mesoporous silica and NaCl – NaBr – Na2MoO4 salt eutectic

Nanofibers with thermal management ability are attracting great attention in both academia and industry due to the increasing interest in energy storage applications, thermal insulation, and thermal comfort. While electrospinning is basically a fiber formation technique, which uses electrostatic forces to draw ultrafine fibers from a wide variety of polymers, with the addition of phase change materials (PCMs) to the electrospinning solution it enables the production of shape stabilized phase change materials with thermal management functionality. In this study, polyacrylonitrile (PAN) nanofibers containing paraffinic PCMs were produced by electrospinning method and the composite nanofibers obtained were characterized in terms of their morphology, chemical structure, thermal properties, stability, thermal degradation behaviour and hydrophobicity. Besides, PCMs with different phase transition temperatures were added simultaneously into the nanofiber structure in order to investigate the tunability of the thermoregulation properties of the nanofibers. Uniform nanofibers with thermal management functionality were obtained. It could be possible to obtain composite nanofibers showing thermoregulation ability over a wider temperature range by simultaneous addition of PCMs with different melting points into the nanofiber structure. 50 wt% PCM could be added to PAN nanofiber structure wherein the resulting nanofiber exhibited 58.74 J g−1 of enthalpy storage during heating and 57.41 J g−1 of heat release during cooling. The composite nanofibers maintained their cylindrical fiber morphology, structure and composition after multiple heating–cooling cycles and retained their thermal management functionality. The contact angle measurements showed that the addition of PCMs imparted hydrophobicity to the nanofibers.

Evaluation of paraffin infiltrated in various porous silica matrices as shape-stabilized phase change materials for thermal energy storage