The mirror. (Stillwater, Minn.) 1894-1925, 1918-01-31

Q:-What is the nickname given St. PAUL. II. L.
Alt is sometimes referred "The Gem City, and
'"The Sanity City, and ''Sin Paul.
o. Secretary of State and Secretary of War
under President Jackson? Obs
A:Martn Van Buren, Secretary of State; John H. Eaton
Secretary of War;
OILS the when superheated more effective for
than the saturated steam the secret of
advantage of superheng? Is the expansive energy
after cutoff takes place? &C. E. D.
Ain reading the following carefully, the of super
heated will without doubt become clear to you
The efficiency of engine depends ratio of the
temperatures between which operates and mechan
cal construction In the actual engine the
steam is lost by radiation conduction condensation leakage
and imperfect action of the valves The cylinder walls the
theoretical engine supposed be made
material while In the actual engine the walls metal which
admits of ready interchange of heat between cylinder
steam In theoretical engines expands without loss
any heat while in the actual engine large
lost by radiation and condensation Consider engine
atng with admission 100 pounds absolute
pounds absolute The temperature admission 327 and
exhaust 2224. The metal walls of cylinder being good
conductors and radiators of heat cooled by the low temper
AZURE of the exhaust, that the entering passing
through the and into the cylinder subjected
peature than 1907 cooler This means
that heat must flow from the steam the metal until both
of the temperature This the give up
of its latent heat and saturated lose any its
heat without condensation cylinder covered
with film of moisture usually spoken of initial condensation.
This condensation in simple unacketed engines may easily
2O of the entering The moisture cyn
der has, however, the temperature the has
simply lost its heat of vaporzation
The first condensed in the cylinder does no
works its heat used the cylinder and later when
reevaporated, it works only during part expansion
and reduced efficiency because is reevaporaed
admission If the cutoff is short, perhaps 2O% of the
condensed be during expansion; the cutoff
is long, 1917 may be reevapoated the remaining in the
cylinder release still in the form of moisture. Thus
entering passes through cylinder
after CUTOFF and still more entirely through without
doing any work.
Suppose engine using 80 pounds of steam per p.
per hour and admission 100 pounds absolute The latent
of vaporizaon this pressure 1874 B. T. US. per
pound If the condensation 335 then 10 pounds
condensed and there lost 10 times 1884, 1884 B. T. U.s.
per hour, 147.3 per mnute and since 4242 B. T. Us=1
horsepower there is lost by condensation 47 8 4242 3a
horsepower If the the cutoff shortened the condensation
increases and 5O% Of less is used
short cutoff than with long cutoff and in many
5O% of the short cutoff great absolute
quantity as 3O% at a long cutoff
In addition the actual loss from the condensation in the
cylinders is still another loss due Incorporation, known
Suppose before that 10 pounds
condensed in the cylinder and that 2O% of this
Grated during expansion This will pounds be
during the exhaust Suppose that the exhaust
pounds above atmospheric pressure Then the heat of
vaporizaon T. US. per pound steam will
require times $685. 1868 B. T. U.s. evaporae the
pounds All of this taken from the cylinder leaving
engine much cooler than would be for this
evaporation
From the above you will understand why the efficiency
engine low and how be large
by superheatng the The following five items
give real purpose of upeheaed in few words
possible:
CD Raising the temperature which constitutes the upper
limit operation of the engine in such
increase thermodynamc efficiency of the working fluid
(2 To charge with heat that give up
much as may be required prevent initial condensation
the cylinder and still perform the work of
pansioo condensation cooling of the surrounding
walls of the cylinder.
(3 To weight of the entering the condenser
final heat charge minimum, with view to the reduc
volume of the condensng and magnitude and
cost of the pump and condenser system a minimum.
Ia To the back and thus increase the power
developed given charge of and efficiency of the
engine.
(5 To increase the efficiency boilers by
ton of the quantity demanded from the original
heating and by increasing the of the heating surface
employed the furnace fue and also
evadng the production OF wet
commonly called, saturated steam.
The items depend upon fundamental fact-the
poor conductivity of dry To the property OF
ducvy of heat upeheaed seam due its great advantage
greatest gains from the of superheated be
gotten the uneconomica plants That is the per
cent of saving by of superheaed in a simple
engine greater compound engine, and for
pound engine comprred with triple expansion engine
now reduce engine
with in the diameter of its cylinder
use of supeheated The combination simple engine
with low pressure and superheaed will give
all operators. %. c. L.