An analysis of the results obtained makes it possible to draw the important practical conclusion that the use of a more open charge leads to intensification of heat exchange only in the high-temperature portion of the kiln (the firing zone) while in the low temperature zones use of a more open charge does not lead to significant intensification of heat exchange. Therefore in rapid heating kilns the ratio of the dimensions of the heating zones must be changed in the direction of a relative increase in the size of the low-temperature zones (heating and cooling). For a pile of a charge heated on all sides it is necessary to find the optimum values of porosity since small values of it are unfavorable for intensification of heat exchange while with high porosities the kiln productivity drops.