Emissions and thermal efficiency for premixed burners in a condensing gas boiler

This work experimentally studied the performance of two types of burners in a condensing gas boiler. The thermal efficiency and emissions of the metal fiber (MF) burner and the stainless steel (SS) burner are compared. When the excess air rate is in the range of 1.15–1.4 and the heat load is 24 kW, the CO emissions of the SS burner are higher than of the MF burner. When the excess air rate is in the range of 1.15–1.4 and the heat load is 24 kW, NOx emission of two burners will below 40 ppm at excess air rate of 1.2. Under the same conditions, the average fan speed of MF burner is higher than that of SS burner. It means that the resistance of MF burner is greater than that of SS burner. When the excess air rate less than 1.25, the thermal efficiency of the MF burner is lower than that of the SS burner. The excess air rate exceeds 1.35, thermal efficiency of the MF burner is higher than that of the SS burner. When adopting metal fiber burner at minimum heat load, the condensing gas boiler has the maximum efficiency.