Fluid to particle convective heat transfer coefficient in a horizontal scraped surface heat exchanger determined from relative velocity measurement

Liquid-to-particle convective heat transfer coefficient (h(fp)) between fluid and particle was investigated in continuous flow through a horizontal scraped surface heat exchanger. The relative velocities between fluid and particle were measured, and h(fp) calculated from well known correlations. Heat transfer coefficients increased with increasing flow rate, rotational speed, and decreased with increasing carrier medium viscosity and particle size. The measured relative velocities during flow visualization studies ranged from 0.04 to 0.29 m/s with corresponding h(fp) values of 597 W/m(2) degrees K and 1975 W/m(2) degrees K, respectively. Even with the most conservative correlation, Nusselt numbers ranged from 12.1 to 49.7; significantly greater than the value of 2.0 for a sphere in a stagnant fluid.