The addition of latent heat storage systems in solar thermal applications has several benefits including volume reduction in storage tanks and maintaining the temperature range of the thermal storage. A phase change material (PCM) provides high energy storage density at a constant temperature corresponding to its phase transition temperature. In this paper, a high temperature PCM (melting temperature of ) made of a composite of paraffin and graphite was tested to determine its thermal properties. Tests were conducted with a differential scanning calorimeter and allowed the determination of the melting and solidification characteristics, latent heat, specific heat at melting and solidification, and thermal conductivity of the composite. The results of the study showed an increase in thermal conductivity by a factor of 4 when the mass fraction of the graphite in the composite was increased to 16.5%. The specific heat of the composite PCM (CPCM) decreased as the thermal conductivity increased, while the latent heat remained the same as the PCM component. In addition, the phase transition temperature was not influenced by the addition of expanded graphite. To explore the feasibility of the CPCM for practical applications, a numerical solution of the phase change transition of a small cylinder was derived. Finally, a numerical simulation and the experimental results for a known volume of CPCM indicated a reduction in solidification time by a factor of 6. The numerical analysis was further explored to indicate the optimum operating Biot number for maximum efficiency of the composite PCM thermal energy storage.
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e-mail: gonzalez@me.ccny.cuny.edu
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November 2010
Research Papers
Analysis and Design of a Paraffin/Graphite Composite PCM Integrated in a Thermal Storage Unit
R. Pokhrel,
R. Pokhrel
Department of Mechanical Engineering,
Santa Clara University
, Santa Clara, CA 95053
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J. E. González,
J. E. González
Department of Mechanical Engineering,
e-mail: gonzalez@me.ccny.cuny.edu
City College of New York
, New York, NY, 10031
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T. Hight,
T. Hight
Department of Mechanical Engineering,
Santa Clara University
, Santa Clara, CA 95053
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T. Adalsteinsson
T. Adalsteinsson
Department of Chemistry,
Santa Clara University
, Santa Clara, CA 95053
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R. Pokhrel
Department of Mechanical Engineering,
Santa Clara University
, Santa Clara, CA 95053
J. E. González
Department of Mechanical Engineering,
City College of New York
, New York, NY, 10031e-mail: gonzalez@me.ccny.cuny.edu
T. Hight
Department of Mechanical Engineering,
Santa Clara University
, Santa Clara, CA 95053
T. Adalsteinsson
Department of Chemistry,
Santa Clara University
, Santa Clara, CA 95053J. Sol. Energy Eng. Nov 2010, 132(4): 041006 (8 pages)
Published Online: September 3, 2010
Article history
Received:
November 18, 2009
Revised:
February 2, 2010
Online:
September 3, 2010
Published:
September 3, 2010
Citation
Pokhrel, R., González, J. E., Hight, T., and Adalsteinsson, T. (September 3, 2010). "Analysis and Design of a Paraffin/Graphite Composite PCM Integrated in a Thermal Storage Unit." ASME. J. Sol. Energy Eng. November 2010; 132(4): 041006. https://doi.org/10.1115/1.4001473
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