CO and CO_{2} = per cent of CO and CO_{2} by volume from flue gas
analysis.
10,150 = the number of heat units generated by burning to CO_{2} one
pound of carbon contained in carbon monoxide.
(E) Loss due to unconsumed carbon in the ash (it being usually assumed
that all the combustible in the ash is carbon).
Loss in B. t. u. per pound =
per cent C × per cent ash × B. t. u. per pound of combustible in the ash
(usually taken as 14,600 B. t. u.) (36)
The loss incurred in this way is, directly, the carbon in the ash in
percentage terms of the total dry coal fired, multiplied by the heat
value of carbon.
To compute this item, which is of great importance in comparing the
relative performances of different designs of grates, an analysis of the
ash must be available.
The other losses, namely, items 2, 5 and 8 of the first classification,
are ordinarily grouped under one item, as unaccounted for losses, and
are obviously the difference between 100 per cent and the sum of the
heat utilized and the losses accounted for as given above. Item 5, or
the loss due to the moisture in the air, may be readily computed, the
moisture being determined from wet and dry bulb thermometer readings,
but it is usually disregarded as it is relatively small, averaging, say,
one-fifth to one-half of one per cent. Lack of data may, of course, make
it necessary to include certain items of the second and ordinary
classification in this unaccounted for group.