METHOD OF OBTAINING FURNACE TEMPERATURE An approximate method of obtaining the tempera ture of the furnace.
Apparatus.
A piece of ordinary fire-clay brick weighing about two pounds and the sharp edges of which have been rounded to prevent small pieces being broken off in handling.
A metal pail of about i 2 to 14 quarts capacity.
A long handled, narrow shovel made with a piece of pipe and a sheet of about " iron.
Weigh the pail empty and also when about two thirds full of clear water, and record the temperature of the water.
Weigh the brick when dry.
Place brick in furnace where the temperature is desired and allow it to come to the temperature of the furnace.
Remove brick by means of the long handled shovel and place it in the pail of water as quickly as possible to minimize the heat loss due to radiation, and note carefully the maximum temperature rise of the water. Then the heat absorbed by the water and pail is equal to the heat given up by the brick, neglecting radiation.
In actual practice, the excess air supply when using coal will be considerably greater than when using oil, which will increase the furnace losses for coal due to the heat used to heat this air from F. to F. and the available heat for steam making will be correspondingly less. Deducting 3% from the
heating value of each fuel to cover the losses due to furnace radiation (this will be about right for well designed boiler settings), we have: Coal = 9,619— (i3,102 x 3%) = 9,226 B.T.U. Oil = 16,16o— (19,191 x 3%) = 15,584 B.T.U.
As an illustration of the close regulation of air supply with oil as compared to coal, these figures are very instructive: With 15,584 B.T.U. available for steam making we should obtain, with oil, = 16.06 970.4 lbs. equivalent evaporation per lb. of oil, and the fact that 16 lbs. is sometimes obtained, indicates that the air supply is very close to that theoretically required, which accounts in a great measure for the high boiler and furnace efficiency obtainable with oil fuel.
With 9,226 B.T.U. available for steam making we should obtain with coal, 9,226 9.5 lbs. equivalent evaporation per lb. of coal, while in actual operation test of this coal would probably give results in the neighborhood of 7 lbs. to 8 lbs., the difference be ing largely due to the excess air supply.
A flue gas temperature drop of F. was observed, during a recent boiler test, when the fire was being replenished with coal.