Abstract. This publication presents the experiences and results of generalization criterion equation of importance in the analysis of the processes of heat transfer and thermal calculations of low-power heat generators cooled combustion chambers. With generalizing depending estimated contribution of radiation and convective heat transfer component in the complex for the combustion chambers of small capacity boilers. Determined qualitative and quantitative dependence of the integrated radiative-convective heat transfer from the main factors working combustion chambers of small volume.Study of heat transfer in cooled combustion chambers and study the effect on the intensity of various factors is difficult and urgent task.From the analysis of theoretical and experimental data on heat transfer in combustion chambers of various plants it should be that the existing methods do not take into account the peculiarities of heat transfer in furnaces of small dimensions and can't be used for their thermal design.The process of heat transfer in furnaces from the radiating flow of combustion products is determined by the intensity of convection, molecular and radiative transfer, depending on the conditions of entry, ignition and combustion of the fuel-air mixture, changes in physicochemical properties of the medium, the hydrodynamic process conditions and other factors. Convective heat transfer, radiation and molecular thermal conductivity as heat transfer components of the complex, depending on the conditions of development of the process and make a different to-quantitative contribution to the resulting heat transfer. Neglecting any of these components without a detailed analysis of the process may lead to a distortion of the actual physical side of heat transfer and, consequently, to incorrect quantitative relations in the process. The same result is obtained and the analysis of the individual contribution of each component without consideration of their mutual influence [1].Analysis of heat transfer by convection processes, molecular and turbulent heat conduction and radiation in the flow of gas leads to a system of differential equations to be solved simultaneously. The mathematical difficulties in solving this system, make it necessary to search for an approximate solution methods. The basic assumption in this case is connected with the exception of the integral members of the energy transfer equations, which are introduced into it as a result of the presence of radiation. The operation exception