A Preliminary Study of the Effects of Micro-Encapsulated Phase Change Materials Intermixed With Grout in Vertical Borehole Heat Exchangers

2019 ◽  
Author(s):  
Ahmad Aljabr ◽  
Andrew Chiasson ◽  
Abinesh Selvacanabady ◽  
Ali Sulaiman Alsagri
Keyword(s):  
Thermal Conductivity ◽  
Melting Temperature ◽  
Phase Change Materials ◽  
Peak Load ◽  
Temperature Transition ◽  
Apparent Heat Capacity ◽  
Complete Melting ◽  
Preliminary Study ◽  
Capacity Method ◽  
Vertical Borehole

Abstract A thermal analysis of a GCHP system is performed to investigate the effect of adding micro-encapsulated PCM into the borehole grout to improve the thermal performance of GCHP systems. The apparent heat capacity method is used in the numerical model, simulated in COMSOL. The PCM’s thermal properties were varied to study the effect of each property, such as PCM melting temperature, transition temperature range, PCM thermal conductivity, and the amount of PCM within the grout. Even though the low thermal conductivity of PCM compared to ordinary grout adversely affects the GCHP system performance, a potential reduction (∼2%) in borehole length is achieved. The best melting temperature is that which results in a complete melting of PCM around the peak load, instead of around the average load. The melting temperature must be chosen properly for each GCHP scenario, otherwise the benefit from using PCM may not be achieved. There is an insignificant change in the heat pump consumption because EFT is more favorable in PCM cases around the melting temperature, but less favorable after melting completely.

Latent Heat of Fusion and Melting Temperature of Molten Salt Based Carbon Nanotube Suspensions Used as Phase Change Materials

2015 ◽  
Author(s):  
Pau Gimenez-Gavarrell ◽  
Vincent D. Romanin ◽  
Sonia Fereres
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Melting Temperature ◽  
Latent Heat ◽  
Base Fluid ◽  
Phase Change Materials ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
Base Materials ◽  
Nanoparticle Suspensions

Thermal Energy Storage (TES) can improve the efficient and economical use of available resources associated with renewable energies. The choice of Phase Change Materials (PCM) for TES applications is particularly attractive, since PCMs provide high energy storage densities, low costs, and allow energy storage at constant temperatures during the melting/solidification process. However, most commonly used PCMs have low thermal conductivity values, typically less than 1 W/mK. This leads to insufficient heat exchange rates in many applications, where power is as important as the amount of energy stored. Previous studies have shown that adding nanoparticles to molten salts can enhance the thermal conductivity and heat capacity, thus improving performance in TES systems. This study analyzes how adding nanoparticles to ionic liquids/solids affects the latent heat of fusion and melting temperature, critical characteristics of many thermal management systems. An important aspect of nanoparticle suspension preparation is the synthesis method, both from the point of view of scalability and effect on thermophysical properties. Several nanoparticle suspensions are synthesized with carbon nanotubes (CNT) and salt or ionic liquid base materials, using different synthesis methods and sonication times. The melting point and latent heat of fusion are measured for the base materials and nanoparticle suspensions using a Differential Scanning Calorimeter (DSC). The change in latent heat and melting temperature of the nanofluid with respect to the base fluid is shown to be present but not substantial. Possible explanations for the modification of thermal properties with respect to the base fluid are discussed.

Thermal Modeling Solid-Liquid Phase Change Materials (PCMs)

2013 ◽  
Vol 746 ◽  
pp. 161-166
Author(s):  
Tao Hu ◽  
Yan Li ◽  
Duo Su ◽  
Hai Xia Lv
Keyword(s):  
Heat Capacity ◽  
Phase Change ◽  
Temperature Control ◽  
Phase Change Materials ◽  
Thermal Modeling ◽  
Effective Heat Capacity ◽  
Apparent Heat Capacity ◽  
Effective Heat ◽  
Solid Liquid ◽  
Capacity Method

Three thermal modeling methods for phase change materials (PCMs): enthalpy-based method, effective heat capacity method and apparent heat capacity method, are presented in details. Their characteristics and application limitations are compared and discussed. We found that enthalpy-based method and effective heat capacity method are both approximation treatments, and can be well used in steady state problems, while apparent heat capacity method tracks the moving phase change boundary in PCMs, and it is the most accurate and applicable method of the three for dealing with transient processes. This work might provide useful information for the study of using PCMs in temperature control field, especially in aircraft environmental temperature control and thermal management.

Preparation and Properties of Capric-Lauric-Palmitic Acid Eutectic Mixtures/Expanded Graphite Composite as Phase Change Materials for Energy Storage

2014 ◽  
Vol 1028 ◽  
pp. 40-45 ◽  
Author(s):  
Xue Huang ◽  
Yling De Cui ◽  
Bu Ning Zhang ◽  
Guo Qiang Yin ◽  
Guang Zhu Feng
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Melting Temperature ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Ternary Eutectic ◽  
Eutectic Mixture ◽  
Expanded Graphite ◽  
Mass Ratio ◽  
Eutectic Mixtures

This work is focused on the preparation and properties of ternary fatty acid eutectic mixtures/ expanded graphite form-stable phase change materials (PCMs). Based on the theoretical calculation of the mass ratio and ternary eutectic melting temperature, the ternary eutectic mixture of capric acid (CA), lauric acid (LA) and palmitic acid (PA) was prepared firstly, which is for the sake of decreasing the phase transformation temperature. Thermal characteristics such as melting temperature and latent heat of fusion of these developed eutectics measured by using Differential Scanning Calorimetry (DSC) technique, which also showed that the eutectic mixture was composed by CA, LA and PA in the mass ratio of 59.7:30.1:10.02. Then the CA–LA–PA was absorbed in expanded graphite (EG), which acts as a supporting material, the optimum mass ratio of CA–LA–PA to EG is 17:1. The CA–LA–PA/EG composites were characterized by the scanning electronic microscope (SEM), differential scanning calorimeter (DSC). The SEM observations showed that the CA–LA–PA was adsorbed into the porous structure of EG, instead of any chemical action. The DSC results indicated that the phase change temperature and latent heat of the CA–LA–PA and CA–LA–PA/EG were 19.92 °Cand 19.48 °C, and 135.49 J/g and 130.73 J/g respectively. The thermal conductivity of CA–LA–PA /EG composite PCM was improved by the high thermal conductivity of the EG. Thermal cycling test showed that the CA–LA–PA/EG composite had a good thermal reliability. All results indicated that CA–LA–PA/EG composite PCM has a proper melting temperature and latent heat for building energy conservation.

High Thermal Conductivity Shape-Stabilized Phase Change Materials

2000 ◽  
Vol 661 ◽  
Author(s):  
Min Xiao ◽  
Luyi Sun ◽  
Chengya Huang ◽  
Yonghua Zhang ◽  
Kecheng Gong
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Phase Change Materials ◽  
Expanded Graphite ◽  
Thermoplastic Elastomer ◽  
Complete Melting ◽  
Styrene Butadiene Styrene ◽  
Styrene Butadiene ◽  
Butadiene Styrene

ABSTRACTIn this paper, shape-stabilized phase change materials (PCMs) based on paraffin and thermoplastic elastomer poly(styrene-butadiene-styrene) are prepared. The shape-stabilized PCMs can keep the same shape in a solid state even when their temperature is above the melting point of the paraffin. They exhibit same phase transition characteristics as paraffin and up to 80% of the latent heat of paraffin. Thermal conductivity of the shape-stabilized PCMs is increased significantly by the introduction of expanded graphite (EG). The time for complete solidification and complete melting of the composite P(80)/S(20)/EG(3) is two ninths and two fifths of paraffin, respectively.

Optimization of thermal conductivity in composites loaded with the solid-solid phase-change materials

2018 ◽  
Vol 25 (6) ◽  
pp. 1157-1165
Author(s):  
Taoufik Mnasri ◽  
Adel Abbessi ◽  
Rached Ben Younes ◽  
Atef Mazioud
Keyword(s):  
Thermal Conductivity ◽  
Phase Change ◽  
Phase Change Materials ◽  
Solid Phase ◽  
Spherical Inclusions ◽  
First Case ◽  
The Matrix ◽  
Composite Conductivity ◽  
First Time

AbstractThis work focuses on identifying the thermal conductivity of composites loaded with phase-change materials (PCMs). Three configurations are studied: (1) the PCMs are divided into identical spherical inclusions arranged in one plane, (2) the PCMs are inserted into the matrix as a plate on the level of the same plane of arrangement, and (3) the PCMs are divided into identical spherical inclusions arranged periodically in the whole matrix. The percentage PCM/matrix is fixed for all cases. A comparison among the various situations is made for the first time, thus providing a new idea on how to insert PCMs into composite matrices. The results show that the composite conductivity is the most important consideration in the first case, precisely when the arrangement plane is parallel with the flux and diagonal to the entry face. In the present work, we are interested in exploring the solid-solid PCMs. The PCM polyurethane and a wood matrix are particularly studied.

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