n).

Loss in B. t. u. per pound =
per cent C x per cent ash x 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.

TABLE 57

DATA FROM WHICH HEAT BALANCE
(TABLE 58) IS COMPUTED

+------------------------------------------------------+
|+----------------------------------------------------+|
||Steam Pressure by Gauge, Pounds | 192 ||
||Temperature of Feed, Degrees Fahrenheit | 180 ||
||Degrees of Superheat, Degrees Fahrenheit |115.2||
||Temperature of Boiler Room, Degrees Fahrenheit| 81 ||
||Temperature of Exit Gases, Degrees Fahrenheit | 480 ||
||Weight of Coal Used per Hour, Pounds | 5714||
||Moisture, Per Cent | 1.83||
||Dry Coal Per Hour, Pounds | 5609||
||Ash and Refuse per Hour, Pounds | 561||
||Ash and Refuse (of Dry Coal), Per Cent |10.00||
||Actual Evaporation per Hour, Pounds |57036||
|| .- C, Per Cent |78.57||
|| | H, Per Cent | 5.60||
||Ultimate | O, Per Cent | 7.02||
||Analysis -+ N, Per Cent | 1.11||
||Dry Coal | Ash, Per Cent | 6.52||
|| '- Sulphur, Per Cent | 1.18||
||Heat Value per Pound Dry Coal, B. t. u. |14225||
||Heat Value per Pound Combustible, B.