Rheological and energy transport characteristics of a phase change material slurry

Abstract

A phase change material slurry – TBAB (tetra-n-butyl ammonium bromide) CHS (clathrate hydrate slurry) has received intensive attractions in recent years due to its dual-function as thermal energy storage and transport media simultaneously in air conditioning and refrigeration applications. In the present study, the rheological characteristics of TBAB CHS were measured using a rheometer at various solid fractions and in a shear rate range of smaller than 1000 s−1. The results indicated that TBAB CHS was a pseudo-plastic non-Newtonian fluid which showed shear-thinning characteristics. The flow behaviour indices and fluid consistencies of type A and type B TBAB CHS were determined based on the power-law fluid model, which showed good consistency with the previous results obtained from the pressure drop measurements in straight tubes. The apparent viscosity of type A TBAB CHS was larger than that of type B TBAB CHS. The obtained apparent viscosities were compared to the calculated results by using the empirical equations, and the reason for the discrepancies was discussed. Based on the obtained rheological characteristics, the pumping power consumption of TBAB CHS as a secondary refrigerant was estimated and compared to that of chilled water at the same cooling capacity. The result showed a drastic reduction of pumping power when using TBAB CHS in lieu of chilled water.