A wall-mounted gas convection boiler with an atmospheric burner operating in the double modulation mode

Abstract

Introduction. Apartment heating requires the thermal capacity of no more than 1.0–2.5 kW; hot water preparation needs 15–25 kW. Convection gas boilers cannot operate efficiently, if a change in the range of smooth modulation reaches 20 times. Discrete modulation is triggered in the heating mode, which is also accompanied by a substantial increase in greenhouse gas emissions and a sharp decline in energy efficiency. The heating of such premises requires heat generators operating in the two ranges of thermal capacity. Materials and methods. The author analyzes the operation of a wall-mounted convection gas boiler with an atmospheric burner equipped with a three-section manifold that ensures a smooth modulation range of 2.4–6 kW, when the boiler is in the heating mode, and the modulation range of 15–24 kW, when the boiler is in the hot water supply mode (HWS). Results. The author made boiler efficiency diagrams for the heating and HWS modes during the steady boiler operation; the author also made boiler diagrams for discrete modulation modes and the regular on-off switching of the boiler. A direct method, that entailed the study of the flow rates of gas and heat conductor, as well as the boiler inlet and outlet temperatures, was employed to find the energy efficiency values. Conclusions. The use of conventional wall-mounted gas convection boilers as a source of heating for the 60 m2 premises entails discrete capacity modulation, that causes a substantial reduction in the energy efficiency of a heating system and rises greenhouse gas emissions. The application of efficiency indicators to different modes of operation of boilers does not convey the real mode of operation of a boiler during the heating period, since it entails a substantial overestimation, while wall-mounted convection boilers, having atmospheric burners with two ranges of smooth modulation, ensure highly efficient apartment heating.