scholarly journals Liquid Crystals as Phase Change Materials for Thermal Stabilization

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Eva Klemenčič ◽  
Mitja Slavinec
Keyword(s):  
Liquid Crystals ◽  
Heat Source ◽  
Electric Field ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermal Stabilization ◽  
Phase Change Temperature ◽  
Thermotropic Liquid Crystals ◽  
Key Factor ◽  
Change Temperature

Thermal stabilization exploiting phase change materials (PCMs) is studied theoretically and numerically. Using the heat source approach in numerical simulations, we focus on phase change temperature as a key factor in improving thermal stabilization. Our focus is to analyze possible mechanisms to tune the phase change temperature. We use thermotropic liquid crystals (LCs) as PCMs in a demonstrative system. Using the Landau-de Gennes mesoscopic approach, we show that an external electric field or appropriate nanoparticles (NPs) dispersed in LCs can be exploited to manipulate the phase change temperature.

A Study on the Cooling Characteristics of TMA Clathrate Compound with Additives

2006 ◽  
Vol 326-328 ◽  
pp. 1275-1278 ◽  
Author(s):  
Chang Oh Kim ◽  
Jin Heung Kim ◽  
Nak Kyu Chung
Keyword(s):  
Heat Source ◽  
Phase Change ◽  
Specific Heat ◽  
Freezing Point ◽  
Phase Change Temperature ◽  
Source Temperature ◽  
Heat Source Temperature ◽  
Clathrate Compound ◽  
Supercooling Degree ◽  
Change Temperature

This study aims to find out cooling characteristics of TMA 25wt%-water clathrate compound with ethanol such as supercooling, phase change temperature and specific heat. For this purpose, ethanol is added as per weight concentration and cooling experiment is performed at -6, -7 and -8, cooling heat source temperature, and it leads the following result. (1) Phase change temperature is decreased due to freezing point depression phenomenon. Especially, it is minimized as 5.1 and 5.0, 3.8 according to cooling source temperature in case that 0.5wt% of ethanol is added. (2) If 0.5wt% of ethanol is added, average supercooling degree is 0.9 and minimum supercooling is 0.8, 0.7 according to cooling heat source temperature. The restraint effect of supercooling is shown. (3) Specific heat shows tendency to decrease if ethanol is added. It is 3.013~3.048 kJ/kgK according to cooling heat source temperature if 0.5wt% of ethanol is added. Phase change temperature higher than that of water and inhibitory effect against supercooling can be confirmed through experimental study on cooling characteristics of TMA 25wt%-water clathrate compound by adding additive, ethanol.

Preparation and Thermal Propertites of Polyethylene Glycol/ Silica Hollow Nanospheres Composite as Shape-Stabilized Phase Change Materials

2013 ◽  
Vol 773 ◽  
pp. 534-537 ◽  
Author(s):  
Li Li Feng ◽  
Jing Jing Tong ◽  
Chong Yun Wang
Keyword(s):  
Thermal Properties ◽  
Polyethylene Glycol ◽  
Phase Change ◽  
Porous Structure ◽  
Phase Change Materials ◽  
Hollow Nanospheres ◽  
Lower Phase ◽  
Phase Change Temperature ◽  
Change Temperature ◽  
Change Material

Shape-stabilized phase change material (PCM) composed of polyethylene glycol and silica hollow nanospheres was prepared by a vacuum impregnating method. Thermal properties of the composite PCM were investigated by various techniques. Lower phase change temperature and enthalpy of the composite PCM were observed. It is concluded that the phase change properties of the composite PCM are influenced by the adsorption confinement of the PEG segments from the porous structure of the silica hollow nanospheres.

Thermodynamics of Phase-Change Energy Storage: The Effects of Liquid Superheating During Melting, and Irreversibility During Solidification

1991 ◽  
Vol 113 (1) ◽  
pp. 2-10 ◽  
Author(s):  
M. De Lucia ◽  
A. Bejan
Keyword(s):  
Heat Source ◽  
Phase Change ◽  
Geometric Mean ◽  
Solidification Process ◽  
Melting Process ◽  
Optimum Temperature ◽  
Phase Change Temperature ◽  
The Third ◽  
Environment Temperature ◽  
Change Temperature

This paper considers the question of whether the optimum phase-change temperature for maximum exergy storage is universally equal to the geometric mean of the heat source and environment temperature, Tm=(T∞Te)1/2. The study consists of three parts. The first deals with the conduction-melting process, and shows that the optimum melting temperature is generally greater than the geometric mean of the source and environment temperatures. The second part covers the conduction-solidification process, and concludes that the irreversibility of solidification decreases monotonically as the phase-change temperature increases. The third part treats the complete cycle of melting (storage) followed by solidification (retrieval), and demonstrates that the optimum phase-change temperature is greater than the optimum temperature of the melting process alone.

Thermal Stability Experimental Study on Three Types of Organic Binary Phase Change Materials Applied in Thermal Energy Storage System

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Song Mengjie ◽  
Liao Liyuan ◽  
Niu Fuxin ◽  
Mao Ning ◽  
Liu Shengchun ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Research Work ◽  
Energy Storage Materials ◽  
Phase Change Temperature ◽  
Change Temperature

Phase change materials (PCMs) are widely applied in recent decades due to their good thermal performance in energy systems. Their applications are mainly limited by the phase change temperature and latent heat. Many publications are reported around the characteristic improvement of binary organic PCMs. The thermal stability study on organic binary PCMs used in thermal energy storage applications becomes fundamental and meaningful. In this study, thermal stability of three types of organic binary PCMs was experimentally investigated, which are frequently used in building and industry applications. To qualitatively investigate the stability of composite PCMs, differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FT-IR) spectra testing of samples were also conducted. Experimental results showed that the selected composite PCMs, capric acid (CA), and myristic acid (MA), had the best thermal performances, with its phase change temperature unchanged and heat of fusion decreased only 8.88 J/g, or 4.55%, after 2000 thermal cycles. Furthermore, quality ratio of required PCMs as the variation of operation duration was analyzed to quantitatively prepare the materials. The PCMs can successfully operate about 3125 times when prepared as 1.20 times of its calculated value by starting fusion heat. Conclusions of this research work can also be used for guiding the selection and preparation of other energy storage materials.

Preparation and Performance Study of Fatty Acid Diatomite Composite Phase Change Materials and Light Weight Phase Change Gypsum Wall Materials

2012 ◽  
Vol 193-194 ◽  
pp. 307-313
Author(s):  
Yi Zhang ◽  
Bin Huang ◽  
Jing Yan Zhang ◽  
Dong Xu Li
Keyword(s):  
Fatty Acid ◽  
Phase Change ◽  
Thermal Performance ◽  
Phase Change Materials ◽  
Performance Test ◽  
Eutectic Mixture ◽  
Cooling Curve ◽  
Performance Study ◽  
Phase Change Temperature ◽  
Change Temperature

Fatty acid phase change materials(PCMs) and composite diatomite PCMs were prepared in this study, the phase change temperature of different mole ratio lauric acid(LA) and capric acid(CA) PCMs were tested by step cooling curve method, thermal physical performance of the prepared PCMs were tested by differential scanning calorimeter (DSC). A new type of lightweight phase change gypsum wallboard incorporated with LA-CA/diatomite composite PCMs was prepared, and the thermal performance of this material was studied. The results showed that the LA and CA could form an eutectic mixture. DSC results indicated that the phase change temperature of the PCMs and composite diatomite PCMs are both 26.7°C, the latent heat of the PCMs are 142.2J/g and 73.5J/g, respectively. Thermal performance test of the gypsum wallboard indicated that the temperature difference of the phase change gypsum wallboard at different moment is lower than the blank gypsum wallboard, which showed a better energy storage function of the phase change gypsum wallboard.

Preparation and Characterization of Diatomite Loaded Composite Phase Change Materials

2013 ◽  
Vol 320 ◽  
pp. 314-319
Author(s):  
Jun Mao ◽  
Shui Lin Zheng ◽  
Yu Zhong Zhang ◽  
Yan Ping Bai ◽  
Yue Liu
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Phase Change Materials ◽  
Physical Adsorption ◽  
Phase Change Temperature ◽  
Composite Phase Change Materials ◽  
Change Temperature ◽  
Composite Phase Change Material ◽  
And Performance ◽  
Change Material

Organic phase change materials like paraffin as phase change material, modified diatomite as carrier, composite phase change material with proper phase change temperature and larger phase change enthalpy is prepared by melt blending. The structure and performance of composite phase material are characterized using SEM, FI-IR and synthesized thermal analyzer DSC. The results show that the phase change temperature of composite phase change material is 30, and phase change enthalpy is 89.54J/g. With every part preserved, phase change particles are distributed in the diatomite/melted paraffin matrix evenly. Stable composite phase change materials are prepared with diatomite as carrier and paraffin as PCM, which are bonded with Vander Waals forces in the form of physical adsorption.

Research on the Thermal Storage Performance of Solid-Solid Phase-Change Material Used in the Wall

2011 ◽  
Vol 347-353 ◽  
pp. 2801-2804 ◽  
Author(s):  
Quan Ying Yan ◽  
Li Li Jin
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Binary Systems ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Thermal Storage ◽  
Phase Change Temperature ◽  
Change Temperature ◽  
Materials Used ◽  
Change Material

Solid-solid phase change material can increase the thermal storage capacity of the wall, decrease the indoor temperature fluctuation and building energy consumption when it was used in the phase change material (PCM) wall. This paper investigated experimentally the phase change temperature and latent heat of polyalcohols binary system with different component, and analyzed the feasibility of phase change wall. The results show that binary systems have suitable phase change temperature and bigger phase change latent. They are ideal phase change materials used in the wall.

Experimental Research on Shape-Stabilized Phase Change Materials Applied in the Phase Change Wall

2013 ◽  
Vol 800 ◽  
pp. 243-246
Author(s):  
Li Hang Yue ◽  
Quan Ying Yan ◽  
Zhen Bang Ruan
Keyword(s):  
Phase Change ◽  
Latent Heat ◽  
Mass Fraction ◽  
Phase Change Materials ◽  
Critical Mass ◽  
Phase Change Temperature ◽  
Change Temperature ◽  
Save Energy ◽  
The Stability ◽  
Change Material

Shape-stabilized phase change materials can store thermal energy and save energy when it is added into the wall. The phase change temperature, latent heat and the stability of shape-stabilized phase change materials with different component were studied experimentally. The critical mass fraction of paraffin required in the materials is given. It is proved that the shape-stabilized phase change material is ideal material used in the phase change wall because it has good stability and uniformity, higher latent heat and suitable phase change temperature.

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