The purpose of this work is to study the thermal stress of the furnace of a fire-tube boiler and its effect on the design of the boiler. To study the effect of thermal stress and furnace proportions on the ratio of heating surface areas, the calculated resistance was tested. Calculations of heat-tube boilers of sectional hot-water boilers with different proportions of the furnace at different thermal loads of the same furnace volume are performed. The calculation of each heating surface is carried out by the method of successive approximations, based in this case on the chord method. In the calculation process, the flue gas temperature at the outlet of the heating surface was first set, and then refined by successive approximations. To reduce the overall balance of the boiler, another global approximation is made when the temperature determined at the outlet of the last heating surface is set at the beginning of the calculation – in the heat balance, where it affects the loss with outgoing gases and the efficiency of the boiler. It is determined that the optimal.

Keywords: energy efficiency, fire-tube boiler, heat supply, thermal voltage, resource conservation