Investigation of the Heat Transfer Process in a PCM During Melting Phase

2014 ◽  
Author(s):  
Mohammad Bashar ◽  
Kamran Siddiqui
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Energy ◽  
Transfer Process ◽  
Phase Change Materials ◽  
Waste Heat ◽  
Liquid Fraction ◽  
Local Heat Transfer ◽  
Heat Transfer Process ◽  
Interface Temperature

Thermal energy storage systems are gaining significance due to their potential use to store renewable energy and waste heat. Phase change materials (PCMs) are considered to be an efficient way to store thermal energy. However, the heat transfer process during the phase change is not well understood. We report on an experimental study conducted to investigate the heat transfer process in a PCM during melting phase. A PCM storage system subjected to bottom heating from a horizontal heated cylinder was considered using wax as the PCM. An imaging technique was used to capture the movement of the solid-liquid interface. Temperature was measured at multiple locations to quantify the heat transfer process. The interface was found to move with a relatively uniform velocity throughout the melting process however, the heat transfer rate was significantly enhanced in the melted (liquid) phase. The local heat transfer coefficient was found to decrease with an increase in the liquid fraction.

scholarly journals FAZINIO VIRSMO MEDŽIAGOS CHARAKTERISTIKŲ ŠILUMOS KAUPIKLYJE SKAITINIS MODELIAVIMAS / SIMULATION OF THE PHASE CHANGE MATERIALS’ CHARACTERISTICS IN A THERMAL ENERGY STORAGE

2018 ◽  
Vol 10 (0) ◽  
pp. 1-7 ◽  
Author(s):  
Saulius Pakalka ◽  
Kęstutis Valančius ◽  
Giedrė Streckienė ◽  
Vaidvilė Ulbikaitė
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Heat Transfer Process ◽  
Comsol Multiphysics ◽  
Storage Unit ◽  
Energy Storage Unit

In order to use efficiently residual, waste or renewable energy, the application of phase change materials (PCM) grows in building energy systems. At the same time, this poses new technological challenges in choosing specific materials, system design solutions, because it requires a specific knowledge of the heat transfer process during the phase change. The aim of the work is to investigate the heat transfer in a PCM based thermal energy storage unit using the COMSOL Multiphysics software. In the analysis, the properties of the material were evaluated during the phase change. This allowed to determine that the thermal conductivity of the material is of great importance for the intensification of heat transfer. In addition, the analysis of several points in the analyzed object revealed that the phase change does not occur in the surface layer of the PCM during the period under consideration. In order to avoid that, additional solutions such as integrating heat-conductive materials into the PCM or increasing the surface area of the heat transfer could be used. Santrauka Siekiant efektyviai išnaudoti perteklinę, atliekinę ar atsinaujinančių energijos išteklių gaminamą energiją, vis dažniau taikomas fazinio virsmo medžiagų (FVM) panaudojimas pastato energetinėse sistemose. Kartu tai kelia naujus technologinius iššūkius pasirenkant konkrečias medžiagas, sistemų projektinius sprendinius, nes reikia gerai išmanyti šilumos mainų procesą vykstant fazės virsmui. Šiame darbe siekiama ištirti šilumos mainus šilumos kaupiklyje su fazinio virsmo medžiagomis naudojantis COMSOL Multiphysics programa. Analizės metu įvertintos medžiagos savybės vykstant fazės virsmui. Tai leido nustatyti, kad medžiagos šilumos laidumo koeficientas turi didelę reikšmę šilumos mainų intensyvinimui. Be to, atskirų taškų analizė tyrimo objekte atskleidė, kad per nagrinėjamąjį laikotarpį FVM paviršiniame sluoksnyje fazės virsmas neįvyksta. Siekiant to išvengti, galimi papildomi sprendimai, tokie kaip šilumai laidžių medžiagų integravimas į FVM arba šilumos mainų paviršiaus ploto didinimas.

scholarly journals Enhancement of the Thermal Energy Storage Using Heat-Pipe-Assisted Phase Change Material

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6176 ◽  
Author(s):  
Hamidreza Behi ◽  
Mohammadreza Behi ◽  
Ali Ghanbarpour ◽  
Danial Karimi ◽  
Aryan Azad ◽  
...  
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Heat Pipe ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Liquid Fraction ◽  
Energy Storage Applications ◽  
Change Material

Usage of phase change materials’ (PCMs) latent heat has been investigated as a promising method for thermal energy storage applications. However, one of the most common disadvantages of using latent heat thermal energy storage (LHTES) is the low thermal conductivity of PCMs. This issue affects the rate of energy storage (charging/discharging) in PCMs. Many researchers have proposed different methods to cope with this problem in thermal energy storage. In this paper, a tubular heat pipe as a super heat conductor to increase the charging/discharging rate was investigated. The temperature of PCM, liquid fraction observations, and charging and discharging rates are reported. Heat pipe effectiveness was defined and used to quantify the relative performance of heat pipe-assisted PCM storage systems. Both experimental and numerical investigations were performed to determine the efficiency of the system in thermal storage enhancement. The proposed system in the charging/discharging process significantly improved the energy transfer between a water bath and the PCM in the working temperature range of 50 °C to 70 °C.

Solid/Liquid Phase Change Heat Transfer in Latent Heat Thermal Energy Storage

2009 ◽  
Author(s):  
D. Zhou ◽  
C. Y. Zhao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Calcium Chloride ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Metal Foams ◽  
Chloride Hexahydrate

Phase change materials (PCMs) have been widely used for thermal energy storage systems due to their capability of storing and releasing large amounts of energy with a small volume and a moderate temperature variation. Most PCMs suffer the common problem of low thermal conductivity, being around 0.2 and 0.5 for paraffin and inorganic salts, respectively, which prolongs the charging and discharging period. In an attempt to improve the thermal conductivity of phase change materials, the graphite or metallic matrix is often embedded within PCMs to enhance the heat transfer. This paper presents an experimental study on heat transfer characteristics of PCMs embedded with open-celled metal foams. In this study both paraffin wax and calcium chloride hexahydrate are employed as the heat storage media. The transient heat transfer behavior is measured. Compared to the results of pure PCMs samples, the investigation shows that the additions of metal foams can double the overall heat transfer rate during the melting process. The results of calcium chloride hexahydrate are also compared with those of paraffin wax.

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.

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