Paddle dryer/processor functions as an efficient, mechanically agitated, indirect heat transfer device that adds or removes heat from a process mass. The dryers are used for drying, heating, cooling, pasteurization, crystallizing and reacting of pastes, cakes, powders and granules. Dual counter-rotating shafts with intermeshing wedge-shaped paddles produce intimate mixing and optimize heat transfer. The use of hollow paddles for heat transfer results in a compact machine. The heat transfer medium — which can include steam, oil, thermal fluid, water or glycol — is isolated from the process mass.