Numerical investigation of convective heat transfer in pipeline flow of multi-sized mono dispersed fly ash-water slurry

A three-dimensional numerical investigation is performed to understand the influence of dispersed particles on the thermo-fluidic transport of liquid-solid slurry in a horizontal pipe. The study presents some new findings in regard to the heat transfer in a flow regime for a liquid-solid slurry that has not been studied in detail. A dimensional analysis is also carried out to understand the pertinent dimensionless quantities influencing the thermo-fluidic transport. The simulation is carried out by deploying an Eulerian multiphase model incorporated with kinetic theory of granular flow. Spherical coal fly ash particles of five different median diameters: 4, 8, 13, 34 and 78 μm, suspended in water for a mean flow velocity ranging from 1 to 5 m/s and particle concentrations within 0-50% by volume for each velocity are considered as the dispersed phase. The pipe wall is kept at an isothermal condition of 400 K whereas the slurry enters the pipeline at a temperature of 300 K. The results illustrate that for all particle sizes, heat transfer ratio is found to increase with particle concentration up to 3% and then gradually decreases with increased particle concentration and mean velocity of flow. Moreover, the heat transfer ratio and the relative pressure drop increase with the particle size at higher concentrations and mean velocities.