Thermal and rheological properties of microencapsulated phase change materials
Zhang, Guan H. and Zhao, Chang-Ying. (2011) Thermal and rheological properties of microencapsulated phase change materials. Renewable Energy, Vol.36 (No.11). pp. 2959-2966. ISSN 0960-1481
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Official URL: http://dx.doi.org/10.1016/j.renene.2011.04.002
The use of microencapsulated phase change materials (MPCMs) is one of the most efficient ways of storing thermal energy. When the microencapsulated phase change material (MPCM) is dispersed into the carrier fluid, microencapsulated phase change slurry (MPCS) is prepared. Due to the relatively large surface area to volume MPCM and its large apparent specific heat during the phase change period, better heat transfer performance can be achieved. Therefore, MPCS can be used as both the energy storage and heat transfer media.
This paper studies the thermal and rheological properties of a series of prepared MPCS. In the experiment: MPCS fabricated by dispersing MPCM into water with an appropriate amount of surfactant. The mass ratio of MPCM to water and surfactant was 10:90:1, 25:75:1, 35:65:1 in prepared MPCS samples, respectively. Then the thermal conductivity and specific heat of MPCS were measured by the Hot Disk. The melting/crystallizing temperature and fusion heat/crystallization heat of the phase change materials were obtained from a DSC (differential scanning calorimetry) during the heating/cooling process. Physical properties, such as viscosity, diameter and its size distribution of MPCS were investigated by a rheometer and a particle characterization system. Meanwhile, the chemical structure of the sample was analyzed using Fourier Transformed Infrared spectroscopy (FTIR).
The results showed that the thermal conductivity and the specific heat of MPCS decreased with particle concentration for the temperatures below the melting point. Overall, the MPCS can be considered as Newtonian fluid within the test region (shear rate >200 s−1 and mass fraction <0.35). The viscosity is higher for bigger particle slurries. The findings of the work lead to the conclusion that the present work suggested that MPCMs can be used in “passive” applications or in combination with active cooling systems; and it also provided a new understanding for fabricating microencapsulated phase change slurry, it is for sure that to have a better potential for energy storage. Accordingly, it has demonstrated that the MPCS fabricated in the current research are suitable for potential application as heat transfer media in the thermal energy storage.
|Item Type:||Journal Article|
|Subjects:||Q Science > QC Physics
T Technology > TJ Mechanical engineering and machinery
|Divisions:||Faculty of Science > Engineering|
|Library of Congress Subject Headings (LCSH):||Phase transformations (Statistical physics), Heat -- Transmission , Microencapsulation|
|Journal or Publication Title:||Renewable Energy|
|Official Date:||November 2011|
|Number of Pages:||8|
|Page Range:||pp. 2959-2966|
|Access rights to Published version:||Restricted or Subscription Access|
|Funder:||Engineering and Physical Sciences Research Council (EPSRC), Guo jia zi ran ke xue ji jin wei yuan hui (China) [National Natural Science Foundation of China] (NSFC), Birmingham Science City|
|Grant number:||EP/F061439/1 (EPSRC), 51071184 (NSFC), SY/SP8008 (BSC)|
 S.S. Al-Jandal, A.A.M. Sayigh, Thermal performance characteristics of STC system with Phase Change Storage, Renewable Energy, 5 (1994) 390-399.
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