Many of the reactions performed in fluidized-bed reactors are exothermic and catalytic. Overheating of the solid catalyst particles must be prevented through effective particle-liquid heat transfer. A rapid and accurate measurement technique for particle-liquid heat transfer was developed. A model which describes the basic physical mechanisms yielded an expression without new empirical coefficients for robust, approximate predictions of the particle-liquid heat transfer coefficient in liquid-solid and gas-liquid-solid fluidized beds. This model takes into account three main effects of neighboring particles on particle heat transfer: the increase in approach liquid velocity, the particle-particle contacts and the impairment of conduction and natural convection.