Characteristics of microencapsulated PCM slurry as a heat-transfer fluid

The hydrodynamic and heat-transfer characteristics of slurry containing mic roencapsulated phase-charge materials (MCPCMs) were investigated experiment ally for use as a heat-transfer fluid. Pressure drop, and local convective heat-transfer coefficients of die slurry flows in a circular tube with unif orm heat flux were measured. Slurries consisting of octadecane (C18H38) con tnined in 2-10-mu m-dia. microcapsules and pure water were used! The partic le volume fractions in the slurry,were varied up to 0.3. Results showed tha t increases in particle volume fractions caused the slurry flow structure t o charge from turbulent to laminar, and the pressure-drop reduction of the slurry flow relative to a single-phase water flow was under the same flow-r ate conditions. The heat-transfer performance of the slurry also depended o n the change in flow structure. When the MCPCMs melted the local heat-trans fer coefficients for turbulent slurry flows increased relative to those for nonmelting slurry. Tills phenomenon was influenced by the MCPCM fraction, the degree of turbulence, and the heating rate at the tube wall. The experi mental data will be useful in the design of thermal-energy transportation s ystems using MCPCM slurry.