| Boiler Pressure in Lbs. Above the Atmosphere | Area of Orifice in Sq. In. for Each Sq. Ft. of Heating Surface. |
|---|---|
| 0.25 | .022794 |
| 0.5 | .021164 |
| 1. | .018515 |
| 2. | .014814 |
| 3. | .012345 |
| 4. | .010582 |
| 5. | .009259 |
| 10. | .005698 |
| 20. | .003221 |
| 30. | .002244 |
| 40. | .001723 |
| 50. | .001389 |
| 60. | .001176 |
| 70. | .001015 |
| 80. | .000892 |
| 90. | .000796 |
| 100. | .000719 |
| 150. | .000481 |
| 200. | .000364 |
FEED WATER HEATERS.
Fig. 97.
There are two forms of feed water heaters: (1) The closed heater, where the feed water passes through tubes, which are enclosed in a shell, through which the exhaust steam passes. (2) The open heater, in which the steam and water come into contact. In the latter the water is sprayed into a space, through which the exhaust steam passes, or is run over a number of inclined perforated copper plates, mingled with the exhaust steam.
The original feed water heater called a “pot heater,” consisted of a vessel so constructed that the feed water was sprayed through the exhaust steam into a globe formed tank, from the bottom of which the heated water was pumped into the boiler; its name was originally the “pot heater,” but as it was open to the air through the exhaust pipe, it was, with its successively improved forms called the open heater.
All the heat imparted to the feed water, before it enters the boiler, is so much saved, not only in the cost of fuel, but by the increased capacity of the boiler, as the fuel in the furnace will not have this duty to perform. There are two sources of waste heat which can be utilized for this purpose: the chimney gases and the exhaust steam. The gases escaping to the chimney after being reduced to the lowest possible temperature contain a considerable quantity of heat. This waste of heat energy may be largely saved by the device illustrated on page [186.]