. nog ■ M
its specific heat, allowing for the exposed side of the cylinder decreasing, is equal
to that of
200 (l + d) d 7T
16
cubic feet of steam heated one degree; but the temperature will rise to the mean
between the condensing and boiling points, or to
160 + 212 igQ 0
2
or the addition of heat will be 26 degrees. The whole quantity of heat consumed
will therefore be
200 x 26 (l + d) dK
16
This divided by the capacity of the cylinder, or gives
50 x 26 (l + d)
Id ’
the loss it would sustain in temperature, or
r = ^, l and d being here both expressed in feet.
When the length of the cylinder is twice its diameter, or 2 d = /, the loss becomes
r = 1950
d
Now one-fifth of the whole power is lost by imperfect condensation, more
than in engines with a separate condenser; which is equal to
—= 225 degrees of heat;
and by the condensation and cooling in the cylinder, we have found
1950
d
Hence the total heat, over and above what is required in other engines, is equi
valent to converting into steam
225 + 1559
d
1500
times the water necessary for the steam engine, with a condenser and steam
pressure.
With a cylinder T5 feet diameter, double the fuel is required, but for a 6-feet
cylinder only one-third more than in the single engine of Watt’s construction.
164. This enables us to illustrate the fact observed by Mr. Watt, when he