This study deals with the modeling and the search for the optimum production capacity of a tunnel-dryer of the Californian type. The model is obtained from the heat and mass transfer balances at two levels, the product (fruits) level and inside the tunnel itself. The optimum condition is given by the maximum production capacity of a plum dryer satisfying the final product quality. This choice is determined by the fact that a large amount of fruit must be dried in a short time to have a minimum of loss. Recirculation of a proportion of the exhaust air improves the dryer efficiently in terms of energy.