ABSTRACT
There are two variables in dry gas loss: stack temperature of the gas and the weight of the gas leaving the unit. Stack temperature varies with the degree of deposition on the heat-absorbing surfaces throughout the unit and with the amount of excess combustion air. The effect of excess air increases the gas weight and raises the exit gas temperature; both effects reduce efficiency. A 40°F (22°C) increase in stack gas temperature on coal-fired installations gives an approximate 1% reduction in efficiency.
