How to estimate thermal efficiency of gas fired boilers?

The thermal efficiency of small and medium-sized gas fired boilers can be calculated by the following formula:
η=96.646-0.043θ+0.248D
θ is the exhaust gas temperature, °C
D is the rated evaporation capacity, t/h
1. The estimation formula contains only two parameters of exhaust temperature and rated evaporation. The calculation and application are very convenient. The ability of the exhaust gas temperature to affect the thermal efficiency is quantitatively given. The exhaust gas temperature is reduced by 10 degrees, and the thermal efficiency is improved. 0.43%, the dew point temperature of the gas fired boiler is very low, reducing the exhaust gas temperature and recovering the sensible heat of the flue gas can increase the thermal efficiency by 2% to 3%, and the energy saving potential is huge;
2. The estimation formula is based on the fire tube gas fired boiler, the technical data of the comprehensive industry gas fired boiler manufacturer, the data fitting, the approximate formula obtained by linear processing with high precision;
3. The estimation formula is based on the fuel combustion characteristics of gas fired boilers and the heat loss characteristics of small and medium-sized boilers. It is further analyzed and simplified by heat balance, and is suitable for small and medium-sized gas fired boilers below 10t/h;
4. When the estimation formula is applied to a gas fired hot water boiler, the rated thermal power of the hot water boiler is converted into the corresponding evaporation amount of the steam boiler;
5. The estimation formula can also be used as a reference for testing and evaluating the thermal efficiency of gas fired boilers in rated load operation. Considering the influence of heat loss, it is necessary to make certain corrections for use under non-rated conditions