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The author shows that the commonly used heat balance based on the first law of thermodynamics does not allocate the losses in a power plant in such a manner as to reveal the best points of attack on the problem of improving power-plant economy. The application of the second law gives a quite different statement of the losses of energy from the coal pile to the stack and engine exhaust. As an example, the performance of a locomotive is analyzed by both the first- and second-law methods.

Based on the furnace heat balance, an empirical “effectiveness factor” is derived for water-cooled surfaces therein, relating the heat radiated by the burning fuel and products of combustion to the furnace-outlet temperature. The value of this factor is calculated from certain experimental data for turbulent horizontally fired pulverized-coal furnaces with bare water-cooled tube walls. For these experimental data, the fraction radiated of the heat liberated in the furnace has also been calculated and is compared with Broido’s curve and with the value calculated by the Orrok-Hudson formula. The method of applying the effectiveness factor to design problems is illustrated by showing the effect of preheated-air temperature upon the furnace-outlet temperature.