Influences of Heat Exchanger Aspect Ratio and Carbon Additives on PCM-Mixture Heat Storage
By: Bahraseman, Hamidreza Ghasemi
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Contributor(s): Mohssenzadeh, Morteza | Reilly, Hayden.
Publisher: New Delhi Journals Pub 2018Edition: Vol. 4(2), Jul-Dec.Description: 11-23p.Subject(s): Mechanical EngineeringOnline resources: Click here
In:
International journal of thermal energy and applicationsSummary: Phase change materials (PCM) are a specific classification for materials with a high heat of fusion. This characteristic allows for their use in thermal energy storage due to the large amount of energy required during the transition from the solid to liquid phase. The largest issue with the implementation of PCMs into heat storage is their relatively low thermal conductivity which affects the speed that the materials can accept energy for storage. Using additives in the PCM such as carbon structures, metallic powder, and other nanoparticles have been shown to be effective at combating this problem. This study explores the effects of heat exchanger aspect ratio and the addition of carbon nanoparticles have on the rate of PCM heat storage. Three different heat exchanger geometries were modeled, meshed and analyzed using ANSYS. Within ANSYS the FLUENT solver was used alongside the Melting/Solidification model to perform the calculations. It was found that effectively increasing the contact surface area between the PCM and the heat exchanger produced a decrease in the time required to fully melt the PCM, most notably being 26.19% decrease in time between case 1 and 3. It was then that we could take one step further and explore the additional benefits that carbon nanoparticles would have at various mixture amounts. From our mixture simulations, it was evident that a carbon additive greatly decreases the melting times in comparison to PCM alone. As little as 8% carbon additive results in an elapsed melting time of 11 hours which is strikingly different to the 105 hours it takes to melt PCM alone. A higher aspect ratio symmetrical heat exchanger and the addition of carbon nanoparticles, with costs permitting, would be recommended based on the findings of this study.
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Phase change materials (PCM) are a specific classification for materials with a high heat of fusion. This characteristic allows for their use in thermal energy storage due to the large amount of energy required during the transition from the solid to liquid phase. The largest issue with the implementation of PCMs into heat storage is their relatively low thermal conductivity which affects the speed that the materials can accept energy for storage. Using additives in the PCM such as carbon structures, metallic powder, and other nanoparticles have been shown to be effective at combating this problem. This study explores the effects of heat exchanger aspect ratio and the addition of carbon nanoparticles have on the rate of PCM heat storage. Three different heat exchanger geometries were modeled, meshed and analyzed using ANSYS. Within ANSYS the FLUENT solver was used alongside the Melting/Solidification model to perform the calculations. It was found that effectively increasing the contact surface area between the PCM and the heat exchanger produced a decrease in the time required to fully melt the PCM, most notably being 26.19% decrease in time between case 1 and 3. It was then that we could take one step further and explore the additional benefits that carbon nanoparticles would have at various mixture amounts. From our mixture simulations, it was evident that a carbon additive greatly decreases the melting times in comparison to PCM alone. As little as 8% carbon additive results in an elapsed melting time of 11 hours which is strikingly different to the 105 hours it takes to melt PCM alone. A higher aspect ratio symmetrical heat exchanger and the addition of carbon nanoparticles, with costs permitting, would be recommended based on the findings of this study.
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