scholarly journals Short-Chain Modified SiO2 with High Absorption of Organic PCM for Thermal Protection

Nanomaterials ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 657 ◽  
Author(s):  
Fuxian Wang ◽  
Shiyuan Gao ◽  
Jiachuan Pan ◽  
Xiaomei Li ◽  
Jian Liu
Keyword(s):  
Thermal Conductivity ◽  
Phase Change Materials ◽  
Thermal Protection ◽  
Short Chain ◽  
High Porosity ◽  
Step Method ◽  
Hydrophobic Property ◽  
Low Thermal Conductivity ◽  
Hydrophobic Sio2 ◽  
High Absorption

Organic phase change materials (PCMs) have great potential in thermal protection applications but they suffer from high volumetric change and easy leakage, which require “leak-proof” packaging materials with low thermal conductivity. Herein, we successfully modify SiO2 through a simple 2-step method consisting of n-hexane activation followed by short-chain alkane silanization. The modified SiO2 (M-SiO2) exhibits superior hydrophobic property while maintaining the intrinsic high porosity of SiO2. The surface modification significantly improves the absorption rate of RT60 in SiO2 by 38%. The M-SiO2/RT60 composite shows high latent heat of 180 J·g−1, low thermal conductivity of 0.178 W·m−1·K−1, and great heat capacity behavior in a high-power thermal circuit with low penetrated heating flow. Our results provide a simple approach for preparing hydrophobic SiO2 with high absorption of organic PCM for thermal protection applications.

Freeze-drying preparation of porous diatomite ceramics with high porosity and low thermal conductivity

2020 ◽  
Vol 119 (4) ◽  
pp. 195-203
Author(s):  
Lei Han ◽  
Faliang Li ◽  
Haijun Zhang ◽  
Yuantao Pei ◽  
Longhao Dong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Freeze Drying ◽  
High Porosity ◽  
Low Thermal Conductivity

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.

Rigid Polyurethane Foam: A Versatile Energy Efficient Material

2016 ◽  
Vol 678 ◽  
pp. 88-98 ◽  
Author(s):  
Harpal Singh
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Weight Ratio ◽  
Building Envelope ◽  
Polymerization Reaction ◽  
Low Density ◽  
High Porosity ◽  
Rigid Polyurethane Foam ◽  
Low Thermal Conductivity ◽  
Moisture Permeability

Rigid polyurethane foam (RPUF) is typically prepared by the reaction of an isocyanate, such as methyl diphenyl diisocyanate (MDI) with a polyol blend. During the polymerization reaction, a blowing agent expands the reacting mixture. The finished product is a solid, cellular polymer with a high thermal resistance. RPUF is an outstanding material for different applications. It has many desirable properties such as low thermal conductivity, low density, low water absorption, low moisture permeability, excellent dimensional stability, high strength to weight ratio. So, it is the best insulating material for industrial buildings, cold storages, telecom and defense shelters due to low thermal conductivity, low density, low moisture permeability and high porosity. It works to reduce heating and cooling loss, improving the efficiency of the building envelope. Thus, RPUF insulation in building envelopes brings additional benefits in energy savings, resulting in lower energy bills and protecting the environment by cutting CO2 emissions.

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.

scholarly journals Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu

2019 ◽  
Vol 3 (11) ◽  
pp. 971-976 ◽  
Author(s):  
M. Grott ◽  
J. Knollenberg ◽  
M. Hamm ◽  
K. Ogawa ◽  
R. Jaumann ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Porosity ◽  
Low Thermal Conductivity

Uncertainty Analysis of Thermal Protection by Microencapsulated Phase Change Micro/Nanoparticles during Hyperthermia

2011 ◽  
Vol 291-294 ◽  
pp. 1816-1819
Author(s):  
Yong Gang Lv ◽  
Yang Zou ◽  
Li Yang
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Heat Capacity ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermal Protection ◽  
Treatment Protocol ◽  
Lower Phase ◽  
Phase Transition Temperatures ◽  
Protection Efficacy

Uncertainties for thermal protection efficacy caused by deviations of the values of phase change materials (PCMs) properties (including conductivity, heat capacity, thermal conductivity, latent heat and phase transition temperature) were studied based on our previous study. Our results suggested that the radius of the micro/nano PCM particle, and the upper and lower phase transition temperatures of the PCM should be carefully measured before performing thermal protection by PCMs during hyperthermia. The results will further help us to enlarge the application of clinical hyperthermia in cancer treatment and optimize the treatment protocol of thermal protection by PCMs.

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.

scholarly journals Development of Porous Tungsten Mud Waste-based Alkali-activated Foams with Low Thermal Conductivity

2020 ◽  
Author(s):  
Imed Beghoura ◽  
Joao Castro-Gomes
Keyword(s):  
Thermal Conductivity ◽  
Mining Waste ◽  
Foaming Properties ◽  
Original Material ◽  
Insulation Material ◽  
High Porosity ◽  
Low Thermal Conductivity ◽  
Aluminium Powder ◽  
Blowing Agent ◽  
Alkali Activated

Aim of this study was to produce alkali-activated foams with low thermal conductivity. Different precursors’ maximum particles sizes of 150μm, 300μm, and 500μm using a blend of 70% tungsten mining waste mud (TWM), 20% grounded waste glass (WG) and 10 % metakaolin (MK) with sodium silicate (SS) and sodium hydroxide (SH) as original material. Aluminium powder (Al) was used as a blowing agent and added first to the dry mix by changing content from 0.1g to 0.5g. Precursors and activators were mixed together to produce a homogeneous mixture, which was placed into a mould (100x200x60 mm3), and cured in the oven at 60∘C for 24 hours. The effect on foaming properties of different precursors maximum particles sizes were studied. The AAFs exhibited 28 day compressive strengths ranging from 2.28 to 16.1 MPa with the different densities from 913 to 1647 kg/m3 achieved through alteration of the foaming content. The thermal conductivity of AAFs was in the range 0.21– 0.33 W/m*K. Open celled hardened of the AAFs with 0.5g Al shows a high porosity of 58% with the mix made with 500μm. Therefore, tungsten mining waste-based alkali-activated foams shows a promise as thermal insulation material in some situations.

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