Wang, Yi (2019-10). Flow Behavior and Heat Transfer Performance of Microencapsulated Phase Change Material Slurry in Coiled Tubes with Reversed Loops and Wire Coil Inserts. Doctoral Dissertation.
Thesis
The purpose of this study was to evaluate the thermal performance of modified helical coils by using water and an advanced heat transfer fluid consisting of microencapsulated phase change material (MPCM) slurry. The helical coiled tubes consisted of 360? reversed plastic tubing with or without wire coil inserts placed at every 180? of the coil to promote fluid mixing. The experimental system was validated by comparing water pressure drop and heat transfer data in a conventional plain helical coil with well-established correlations. Thermo-physical properties of MPCM slurry were experimentally characterized at MPCM mass fractions of 5.4% and 9.7%. Viscosity results showed that MPCM slurry behaved as a Newtonian fluid at mass fractions less than 10%. Flow and heat transfer characteristics of water and MPCM slurry were tested in the modified helical coil configurations. New friction factor and Nusselt number correlations for water and MPCM slurry flowing through helical coils with reversed loops and wire coil inserts were postulated based on experimental data. Furthermore, the performance enhancement index of MPCM slurry in the modified configurations under different experimental conditions was obtained to evaluate the overall system effectiveness. The results of this study reveal that there is an optimal combination of MPCM slurry mass fraction, helical coil configuration and experimental conditions, which can lead to optimal heat transfer performance. In the future, results from this study can be used to design industrial heat exchangers and to validate numerical models for energy-transport systems that make use of MPCM slurry
