AbstractAn experimental study of heat transfer from a horizontal tube to a fluidized bed was carried out in the presence of nearby unheated tubes. The effect of the number of tubes, their size, configuration, and the type of fluidized materials was studied. Certain configurations caused as much as a 56% reduction in heat transfer over the most favorable case. The top of the tube was covered by stagnant solids, the bottom partially by a gas film, and the sides by a small region of vigorously agitated solids. Most of the heat transfer occurred in the side region. An overall heat transfer coefficient of 35 Btu/hr‐ft2‐°F. was found at the best condit