| The present work investigates the heat transfer enhancing capability of phase change slurries in natural convection, in rectangular enclosures heated from below. The working fluid used, was a suspension of phase change microcapsules. The vertical walls of the test section are insulated, the lower horizontal wall is a constant heat flux surface and the upper wall is isothermal. The work quantifies the heat transfer rate in parameter ranges hitherto not investigated (DeltaRa∼104 and DeltaSte∼10 2).; The results indicate a significant potential for enhancing the heat transfer rate using phase change slurries. Heat transfer rates increased by as much as 110% with low concentration slurries. The enhancement in heat transfer is strongly influenced by the conductivity ratio of the two phases, the quality of the suspension and the Rayleigh number range. Analysis also reveals that less than 3% of the total phase change material in the slurry at any time actually melted. Idealized estimates indicate that even in the best designed slurries, the very design of the phase change slurry ensures that approximately half the phase change material in a capsule cannot be utilized. Correlations quantifying the Nu variation with Ra and Ste have been developed. |
