The effects of dispersed (kerosene) and continuous (water) phase velocities and particle size (1.0, 2.1, 3.0 or 6.0 mm) on the heat transfer coefficient, dispersed phase holdup and bed porosity in liquid-liquid-solid fluidized beds have been determined. With increasing dispersed phase velocity, the heat transfer coefficient and bed porosity increase in the bed of larger particle sizes (d(p) greater than or equal to 3.0 mm), whereas they exhibit local minimum values in the bed of smaller particle size (d(p) less than or equal to 2.1 mm). The heat transfer coefficient increases with increasing particle size but it exhibits a local maximum with increasing continuous phase velocity and bed porosity. The heat transfer coefficient has been correlated with the surface renewal theory with the concept of isotropic turbulence and the energy dissipation rate. (C) 1999 Elsevier Science Ltd. All rights reserved.