453
OK ENGINEERING FOBMULÆ.
Joule’s Mechanical Equivalent of Heat.
772 loot-pounds.
Heat requires for its production and produces by' its dis-
appearance, 772 foot-pounds for each ™lt of beat.■ umt
being the amount necessary to increase the temperature ol
one pound of water by one degree Fahrenheit.
Expansion of Steam.
r. _ Length of stroke in inches.
Z = Distance travelled by the piston before the steam 13
cut off. j
R = Ratio of expansion — y •
*H — Hyperbolic Logarithm of R, see Table below.
P = Initial pressure of steam in lbs. per sq. lu., including
atmosphere. . . .
p - Mean pressure during stroke in lbs. per sq. m., in-
cluding atmosphere. ,
v =■ Allowance for imperfect vacuum — about 2} lbs. per
square inch.
pL±J!_!U = PK-i>.
p K
Portion of
Stroke at !
which I
Steam is
cut off. ■
Ratio I
of I
Ex pan-
sion.
R. I
Hyper-
bolic
log.
H.
______
Portion of
Stroke at
which
Steam is
cut off.
I.
Batio
of
Expan-
| siou.
B.
K
Hyp&r- (,r
bolic il-f-H
log. —
10 2-302
8 2-079
5 1-609
4 1-386
3-33 1'203
2'66 '978
•916
•693
P-33 I
•385
• 522
•59B
•661
•744
•766
•846
6
1 O
_7_
1-66
1'6
1-43
1-33
1-25
1'14
1-11
•507 -907
•470 -919
•358 '-949
•285 I"966
•223 '-978
•131 ,’992
•104 '995
* T>.n Hvwerbolic Logarithm of any number is found by mu
lhe “TJXuou LpgwUhm of the number by 2-3Ü2686.