Full resolution (JPEG) - On this page / på denna sida - Notes on Steam - Steam heating - Value of high and low pressure steam for heating purposes - Hot water heating in dwelling houses - Quantity of water required to make any quantity of steam at any pressure
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454 NOTES ON STEAM.
general rule, one square foot of radiating surface is sufficient
for heating 40 to 60 cubic feet of air in outer or front rooms,
and 80 to 100 cubic feet in inner rooms. The following rule may
be used as a guide for different conditions : One square foot of
radiating surface is sufficient for heating 60 to 80 cubic feet of
space in dwellings, schools and offices ; 75 to 100 cubic feet of
space in halls, store houses and factories ; 150 to 200 cubic feet
of space in churches and large auditoriums.
In heating mills l^-inch steam pipes are generally used,
and one foot of pipe is allowed per 90 cubic feet of space to be
heated.
Value of Low Pressure Steam for Heating Purposes.
When steam at atmospheric pressure is condensed into
water at a temperature of 212°, each pound of steam gives up
966 B. T. U. of heat, but if steam of 100 pounds gage pressure
(115 pounds absolute) is condensed into water at 212 degrees,
each pound of steam must give up 1004 B. T. U., which is only
38 heat units more than steam of atmospheric pressure. Hence
it is evident that for heating purposes there is no advantage in
using steam of high pressure ; one pound of exhaust steam, only
a pound or two over atmospheric pressure, is almost as valuable
an agent for heating purposes as live steam at 100 pounds pres-
sure direct from the boiler.
Hot Water Heating in Dwelling Houses.
One square foot of heating,surface is required per 30 to 60
cubic feet of space heated.
Quantity of Water Required to Make any Quantity of
Steam at any Pressure.
The weight of water required to make one cubic foot of
steam at any pressure is the same as the weight of one cubic
foot of steam as given in the sixth column in Table No. 82.
Therefore, the weight of water is obtained by multiplying
the number of cubic feet of steam required by the weight of one
cubic foot, as given in the table.
Example.
How much water will it take to make 300 cubic feet of steam
at 100 pounds absolute pressure ?
Solution
:
One cubic foot of steam at 100 pounds pressure is given in
the table as weighing 0.2307 pounds, therefore 300 cubic feet
will weigh 300 X 0.2307 = 69.21 pounds of water.
One cubic foot of water may, for any practical purpose, be
reckoned to weigh 62^ pounds and one gallon of water may be
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