The use of enhanced heat transfer phase change materials (PCM) to improve the coefficient of performance (COP) of solar powered LiBr/H 2 O absorption cooling systems

2016 ◽  
Vol 87 ◽  
pp. 229-239 ◽  
Author(s):  
Francis Agyenim
2019 ◽  
Vol 92 (3) ◽  
pp. 285-301 ◽  
Author(s):  
Wei Li ◽  
Yan Dong ◽  
Jun Wang ◽  
Yong Zhang ◽  
Xu Zhang ◽  
...  

Author(s):  
Yahya Sheikh ◽  
Mohamed Gadalla ◽  
Muhammed Umair ◽  
Elmehaisi Mehaisi ◽  
Ahmed Azmeer

Abstract Phase change materials (PCM) are materials that absorb/release large amounts of thermal energy at constant temperatures during phase change. Consequently, PCMs could be effective when electronic cooling systems such as heat sinks and heat pipes are considered. In the selection of PCMs for cooling systems, bio-based PCMs are more effective when compared to inorganic PCM. However, bio-based PCMs have poor thermal conductivity and therefore suffer from poor heat transfer characteristics. The diffusion of certain additives within the PCM has proven successful in the enhancement of heat transfer during the cooling process. Graphene Nanoplatelets (GNPs) presents itself as one such additive. Using PureTemp PCM as a heat sink for an electric heater, this paper experimentally investigates the cooling performance of the heat sink when GnPs and various surfactants such as, SDS, SDBS and SSL, are added to the bio-based PCM. Finally, results indicate that the addition of GnPs increased the time taken for the heater to reach a reference temperature of 43 °C by nearly 12% when compared to PurePCM heat sink, indicating an improved cooling performance of the PCM heat sink when GnP’s were added. Furthermore, the experiment indicated that SSL surfactant showed a 9% increase in time taken to reach the reference temperature when compared to other surfactants. SDS surfactant indicated the highest increase in thermal conductivity when compared to other surfactants as it reported the highest increase of 147% when compared with the thermal conductivity of PurePCM.


Author(s):  
Yasmin Khakpour ◽  
Jamal Seyed-Yagoobi

This numerical study investigates the effect of using a blend of micro-encapsulated phase change materials (MEPCMs) on the heat transfer characteristics of a liquid in a rectangular enclosure driven by natural convection. A comparison has been made between the cases of using single component MEPCM slurry and a blend of two-component MEPCM slurry. The natural convection is generated by the temperature difference between two vertical walls of the enclosure maintained at constant temperatures. Each of the two phase change materials store latent heat at a specific range of temperatures. During phase change of the PCM, the effective density of the slurry varies. This results in thermal expansion and hence a buoyancy driven flow. The effects of MEPCM concentration in the slurry and changes in the operating conditions such as the wall temperatures compared to that of pure water have been studied. The MEPCM latent heat and the increased volumetric thermal expansion coefficient during phase change of the MEPCM play a major role in this heat transfer augmentation.


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