Heat transport in a three-stage thermal energy system using phase change material slurries

Pruitipong Thaicham*

ABSTRACT: This study investigated the feasibility of creating a phase-change slurry in which a phase-change material is microencapsulated and suspended in a carrier fluid. The heat transportation, pumping power consumption, viscosity, and pressure loss of the flowing slurries were measured in order to determine the most suitable concentration of micro encapsulated phase change material (MCPCM) used in the slurry over the range 5ÿ40%. The effects of repeated use of liquid-solid phase-change particles upon melting and solidifying were studied using a small-scale rig of a closed loop circuit comprised of heating and cooling sections. Results indicated that the use of a MCPCM slurry can improve the performance of a working fluid by up to 52% as compared to a single-phase fluid. However, increasing the concentration of the MCPCM to 40% was found to have little effect on heat transport. MCPCM slurry containing a high concentration of MCPCM had a high apparent viscosity. Use of an ionic surfactant was found to be effective in reducing the viscosity. Results also showed that a 20ÿ30% concentration was the most suitable concentration for the working fluid due to the associated heat capacity and reasonable pressure drop. The use of such a slurry could reduce the power consumption of the pump by 16%. Stratification between the solid particles and the carrier fluid was a major drawback and made it difficult to use a conventional open system. This problem was overcome by combining an open and a closed system into a three-stage (open-closed-open) operation.

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School of Technology, Shinawatra University, 99 Moo10, Bangtoey, Samkok, Pathumthani 12160, Thailand.

* Corresponding author, E-mail: pruitipong@shinawatra.ac.th

Received 15 Aug 2007, Accepted 20 Feb 2008