I will apply Carnot's doctrine to this case.
Potential energy of the fuel with respect to absolute zero:
| Units. | |
| 239.25 lb. × 530° abs. × 0.238 | = 30,053 |
| 194.46 lb. × 17-1/8 × 530° × 0.238, the weight and heat of air | 420,660 |
| 194.46 × 14,544 units heat of combustion of carbon | 2,828,200 |
| ———— | |
| Total energy | 3,278,813 |
| Heat absorbed in evaporating 26.08 lb. of water in fuel | -29,888 |
| ———— | |
| Available energy | 3,248,425 |
Temperature of furnace—
The whole of the fuel was heated up, but the heat absorbed in the evaporation of the water lowered the temperature of the furnace, and must be deducted from the heat of combustion.
| Units. | |
| Heat of combustion | 2,828,200 |
| Heat of evaporation of 26.08 lb. water | -29,888 |
| ——— | |
| Available heat of combustion | 2,798,312 |
| Dividing by 238.25 lb. gives the heat per 1 lb. of fuel used | = 11,745 units. |
And temperature of furnace:
| 11,745 units (18.125 lb. × 0.238) | + 530° | = 3,253° |
| Temperature of chimney 700° + 460° | = 1,160° | |
| Maximum duty | (3,253° - 1,160°) 3,253° | = 0.643° |
Work of displacing atmosphere by smoke at 700°:
| Cubic feet. | |
| Volumes of gases at 70° | = 228.3 |
| Volumes of gases at 700° | = 499.8 |
| ——— | |
| Increase of volume | 271.5 |
| Work done= | Units. |
| (194.46 lb. × 271.5 cub. ft. × 144 sq. in. × 15 lb.) 722 units | = 147,720 |
| Maximum amount of work to be expected = 3,248,425 × 0.643 | = 2,101,700 |
| Deduct work of displacing atmosphere | = 147,720 |
| ———— | |
| Available work | 1,953,980 |