Experimental Study of Microencapsulated Phase Change Slurry in Shell-and-Tube Heat Exchanger

Abstract

Microencapsulated phase change slurry (MPCS) can release and store heat during phase transitions, allowing for a thermal energy transfer to occur when the core material transitions between solid and liquid phases. Numerical and experimental research has shown that MPCS slurries, using water as a base fluid, can improve thermal performance. To investigate the use of MPCS as a working fluid, this study considers slurry synthesis, characterization, and experimental investigation of the MPCS in a shell-and-tube heat exchanger. Characterization of the slurry was performed through thermal analysis, rheometry, and zeta potential measurements. The heat transfer performance and pressure drop across the heat exchanger were benchmarked against a baseline case of water. The effect of particle concentration and Reynolds number on the heat transfer performance of the slurry were evaluated. The results indicate that particle concentration improves heat transfer performance but also increases the pumping requirements due to the exponential increase in viscosity along with particle concentration. The maximum average heat transfer coefficients of 5% and 7.5% mass fraction MPCS was 16.7% and 21.6% higher, respectively, than that of water under the same conditions. Pressure drop increased by 288.1% and 321.2% compared to water for 5% and 7.5% MPCS respectively. A performance enhancement criterion (PEC) was utilized to compare gains in heat transfer performance with increases in pumping power. Despite higher heat transfer coefficients (HTC) at greater Reynolds numbers, water had superior thermo-hydraulic performance at Re > 1550 due to lower residence times and increased pumping power required for the slurries.