The methods to be followed in expressing and calculating those results
which are not self-evident are explained as follows:
(A) _Efficiency._ The "efficiency of boiler, furnace and
grate" is the relation between the heat absorbed per pound of
coal fired, and the calorific value of one pound of coal.
The "efficiency of boiler and furnace" is the relation between
the heat absorbed per pound of combustible burned, and the
calorific value of one pound of combustible. This expression of
efficiency furnishes a means for comparing one boiler and
furnace with another, when the losses of unburned coal due to
grates, cleanings, etc., are eliminated.
The "combustible burned" is determined by subtracting from the
weight of coal supplied to the boiler, the moisture in the coal,
the weight of ash and unburned coal withdrawn from the furnace
and ashpit, and the weight of dust, soot, and refuse, if any,
withdrawn from the tubes, flues, and combustion chambers,
including ash carried away in the gases, if any, determined from
the analysis of coal and ash. The "combustible" used for
determining the calorific value is the weight of coal less the
moisture and ash found by analysis.
The "heat absorbed" per pound of coal, or combustible, is
calculated by multiplying the equivalent evaporation from and at
212 degrees per pound of coal or combustible by 970.4.
Other items in this section which have been treated elsewhere are:
(B) Corrections for moisture in steam.
(C) Correction for live steam used.
(D) Equivalent evaporation.
(E) Heat balance.
(F) Total heat of combustion of coal.
(G) Air for combustion and the methods recommended for
calculating these results are in accordance with those described
in different portions of this book.