Convective heat transfer coefficients for irregular particles immersed in non-newtonian fluid during tube flow☆

Abstract Convective heat transfer coefficients were determined for mushroomshaped aluminum castings immersed in a Power-law pseudoplastic liquid during tube flow. The effect of particle size, fluid flow rate and tube-mean apparent viscosity were investigated. Flow rates were varied from 0.076 to 0.287 kg s−1 and mean apparent viscosities from 2.08 to 17.70 Pa s (corresponding consistency coefficients ranged from 2.34 to 30.50 Pa sn and flow behavior indices from 0.95 to 0.71 respectively). Convective heat transfer coefficient values ranged between 548 W m−2 K−1 and 1175 W m−2 K−1 for the range of particle and fluid variables studied. The convective heat transfer coefficient values increased with increasing particle size and fluid flow rate and decreasing apparent viscosity. A dimensionless Nusselt number correlation (r2 = 96.92%) was obtained in terms of generalized Reynolds and Prandtl numbers, and particle-to-pipe diameter ratios.