scholarly journals Characterization of MgCl2·6H2O-Based Eutectic/Expanded Perlite Composite Phase Change Material with Low Thermal Conductivity

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2369 ◽  
Author(s):  
Chao Zhang ◽  
Zeyu Zhang ◽  
Rongda Ye ◽  
Xuenong Gao ◽  
Ziye Ling
Keyword(s):  
Thermal Conductivity ◽  
Phase Separation ◽  
Phase Change ◽  
Phase Change Materials ◽  
Impregnation Method ◽  
Expanded Perlite ◽  
Thermal Reliability ◽  
Low Thermal Conductivity ◽  
Human Thermal Comfort ◽  
Save Energy

The melting points of the phase change materials (PCMs) incorporated into the walls of buildings should be within the human thermal comfort temperature range. In this paper, 15 wt.% of MgCl2·6H2O was mixed with CaCl2·6H2O to obtain the eutectic with a melting point of 23.9 °C. SrCl2·6H2O suppresses the supecooling of the eutectic. The combination with expanded perlite (EP) via the impregnation method overcomes the phase separation and liquid leakage of the CaCl2∙6H2O-MgCl2∙6H2O mixture. The composite PCM is form-stable with the maximum loading mass fraction up to 50 wt.% and latent heat of 73.55 J/g. EP also significantly reduces the thermal conductivity of the CaCl2∙6H2O-MgCl2∙6H2O from 0.732 to 0.144 W/(m·K). The heating-cooling cycling test reveals that the composite PCM is thermally stable. The cheap eutectic salt hydrate, with little supercooling, no phase separation and liquid leakage, low thermal conductivity and good thermal reliability, show great potential as envelope materials to save energy consumption in buildings.

Latent Heat Storage: Container Geometry, Enhancement Techniques, and Applications—A Review

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
S. Arunachalam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Low Thermal Conductivity

Energy storage helps in waste management, environmental protection, saving of fossil fuels, cost effectiveness, and sustainable growth. Phase change material (PCM) is a substance which undergoes simultaneous melting and solidification at certain temperature and pressure and can thereby absorb and release thermal energy. Phase change materials are also called thermal batteries which have the ability to store large amount of heat at fixed temperature. Effective integration of the latent heat thermal energy storage system with solar thermal collectors depends on heat storage materials and heat exchangers. The practical limitation of the latent heat thermal energy system for successful implementation in various applications is mainly from its low thermal conductivity. Low thermal conductivity leads to low heat transfer coefficient, and thereby, the phase change process is prolonged which signifies the requirement of heat transfer enhancement techniques. Typically, for salt hydrates and organic PCMs, the thermal conductivity range varies between 0.4–0.7 W/m K and 0.15–0.3 W/m K which increases the thermal resistance within phase change materials during operation, seriously affecting efficiency and thermal response. This paper reviews the different geometry of commercial heat exchangers that can be used to address the problem of low thermal conductivity, like use of fins, additives with high thermal conductivity materials like metal strips, microencapsulated PCM, composite PCM, porous metals, porous metal foam matrix, carbon nanofibers and nanotubes, etc. Finally, different solar thermal applications and potential PCMs for low-temperature thermal energy storage were also discussed.

scholarly journals Preparation and Thermal Performance Enhancement of Low Temperature Eutectic Composite Phase Change Materials Based on Na2SO4·10H2O

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2230 ◽  
Author(s):  
Pumin Hou ◽  
Jinfeng Mao ◽  
Fei Chen ◽  
Yong Li ◽  
Xian Dong
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Performance Enhancement ◽  
Expanded Graphite ◽  
Nucleating Agent ◽  
Thermal Reliability ◽  
Composite Phase Change Materials ◽  
Mass Fractions

In this paper, a series of Na2SO4·10H2O–KCl eutectic mixtures were prepared by adding different mass fractions of KCl (1 wt.%, 3 wt.%, 5 wt.%, or 7 wt.%) to Na2SO4·10H2O. Polyacrylamide (PAM) was proposed as the thickener, sodium tetraborate decahydrate (STD) was proposed as the nucleating agent, and expanded graphite (EG) was proposed as the high thermal conductivity medium for Na2SO4·10H2O–5 wt.% KCl eutectics. The results showed that in Na2SO4·10H2O–5 wt.% KCl eutectics with 5 wt.% PAM and 5 wt.% STD, almost no phase separation occurred, and the degree of supercooling was reduced to 0.4 °C. The thermal performance of Na2SO4·10H2O–5 wt.% KCl composite phase change materials (CPCMs) with varying contents of EG was explored. The results showed that EG could improve the thermal conductivity effectively and that the mass fraction of EG should be no more than 3%, otherwise the crystallization value and supercooling would deteriorate. The thermal reliability of the Na2SO4·10H2O–5 wt.% KCl eutectic CPCMs containing 5 wt.% PAM, 5 wt.% STD, and 3 wt.% EG was investigated, mainly through the ambient temperature, thermal cycling test, and TGA analysis. The results demonstrated that these CPCMs showed perfect thermal reliability.

Leakage-proof phase change composites supported by biomass carbon aerogels from succulents

2018 ◽  
Vol 20 (8) ◽  
pp. 1858-1865 ◽  
Author(s):  
Yanhong Wei ◽  
Juanjuan Li ◽  
Furong Sun ◽  
Jinrong Wu ◽  
Lijuan Zhao
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Organic Phase ◽  
Phase Change Materials ◽  
Carbon Aerogels ◽  
Biomass Carbon ◽  
Low Thermal Conductivity ◽  
Practical Applications ◽  
Phase Change Composites

The practical applications of organic phase change materials (PCM) are greatly limited, due to their leakage in the melted state and unacceptably low thermal conductivity.

Personalized Cooling System Using Phase Change Materials

2021 ◽  
Vol 875 ◽  
pp. 184-192
Author(s):  
Kashif Ali ◽  
Rizwan Mahmood Gul ◽  
Salman Noshear Arshad ◽  
Muhammad Ali Kamran
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Melting Point ◽  
Phase Change ◽  
Phase Change Materials ◽  
Cooling System ◽  
Heat Of Fusion ◽  
Human Thermal Comfort ◽  
Protective System ◽  
Change Material

The most widely used personal protective system against heat stress is cooling vest that contains phase change material (PCM) for thermal energy storage. PCMs have the property of absorbing/releasing heat when they change their phase at their melting point. If the PCM has greater heat of fusion, more heat is absorbed; furthermore, good thermal conductivity assists in efficient removal of heat. In this work different PCMs are explored for use in personalized cooling vest. Hexadecane is finally selected to be used as a PCM having a melting point of 18-20 °C (which lies in the human thermal comfort) and heat of fusion of 241 kJ/kg. Carbon nanotubes have excellent capability of increasing thermal conductivity of a material. Carbon nanotubes were added in hexadecane, and latent heat of fusion of the mixture increased up to 262.6 kJ/kg.

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