THERMOPHYSICAL PROPERTIES CHARACTERIZATION OF MICROENCAPSULATED PHASE CHANGE MATERIAL SLURRY

摘要

Current chilled water systems require vast amount of water and pumping power to meet increasing cooling demands. Existing cooling and heating distribution systems have an inherent thermal capacity limitation (e.g., specific heat, mass flow rate, delta T), which is often neglected when adding new buildings to military, industrial or commercial facilities, resulting in higher equipment and infrastructure costs. Through the use of an advanced material concept, namely Microencapsulated Phase Change Materials (MPCM), performance enhancement of an improved heat transfer fluid is now being pursued. This paper discusses the status of experimental efforts using a linear alkane phase change material intended for a secondary coolant for space cooling applications. Initial quantitative characterization of MPCM material properties including latent heat of fusion, melting and freezing points, and temperature- and concentration-dependent viscosity data are presented. State-of-the-art equipment was used to characterize the MPCM slurry including the use of a differential scanning calorimeter and a temperature-controlled concentric viscometer. Results indicate that the freezing and melting points of microencapsulated n-Tetradecane differed by 5℃ or more when no effective nucleating agent was used. Current efforts have yielded the identification of a very effective nucleating agent, which can suppress supercooling almost entirely. Other experimental results indicate that MPCM slurry viscosity significantly depends not only on volume fraction but also on temperature, which can have an impact on the heat transfer process. MPCM slurry has the potential to become a successful heat transfer fluid, which may result in significant energy and cost savings.