Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1891-07-26

IHe IUO 1detiOdS VI DtOgTIHD.
purposes, such as welding, heating rolls for
Photographic burnishers, heating wires for
cauterizing purposes and in many other
cases where comparatively small amount
of energy is transformed into heat; but it is
proposed to show that the broad statement
that the dynamo and its adjuncts can be
made to take the place of the steam radi-
ator, hot air furnace and other systems,
which may, in comparison with the cleo
trical, be termed direct systems, is errone-
Gus and that the plan cannot be success in
the present state of the art of generating the
electrical current
To show this will confne myself to acou-
parison of the fuel bills for q steam heating
and electrical heating system respectively.
The steam heating plant will consist essen
TALLY of boiler and furnace to generate the
steam and a number of radiators to transmit
the heat to the air in several rooms to be
heated, together with the piping, traps,
cocks, valves, etc.
The Cost of Steam Heating.
will assume that the building is heated
IL hours per day for six months in the year
and that the steam system requires 100 tons
of coal at 81 so per ton to keep the rooms
at the required temperature during this
period, giving fuel bill fS1 80 multiplied
by 100 or $50. Now this $3.50 covers a
period of II multiplied by 30 multiplied by
60 or 2, 16O hours Therefore the cost per
hour will be $50 divided by 2, 100 or .OS115-
that is 815c. The amount of coal consumed
each hour will be 100 tons multiplied by
1000, for there are 1000 pounds in a ton,
divided by 2, 160 hours, which gives 92.6
pounds. 1 may fairly assume that the steam
plant will evaporate nine pounds of waterinto
steam for every pound of coal used in the
furnace and that all the latent heat of the
steam, that is, the heat which the steam
gives out on being condensed in the radia-
tors, is utilized in heating the air in the
rooms.
This latent heat amounts to 965 heat units
for every pound of steam, and as l have as
sumed above that every pound of coal pro-
duces nine pounds of steam it is evident
that for each pound of coal used we trans
NIT to the air in the rooms multiplied by
965, or 8, 6S5 heat units; and since there are
92.6 pounds of coal used each hour the heat
transmitted per hour will be s6s5 multiplied
by 926, or SH 231 heat units. This latter fig
ure is the actual amount OF heat necessary
to warm the air in the building for one hour,
and as far as the amount is concerned is
matters not IN what manner we get it.
The Cost for Electrical Heating.
II derived from electrical energy plant
ing essen tial items: First, boiler and fur
mace, by means of which the heat energy OF
combustion is made to appear as potential
energy in the pressure OF steam; second, an
energy is transformed into a mechanical
equiva ent; third, a dynamo to convert the
mec ha nical energy into electrical energy;
four tn, set OF resistance COILS, which in
this caSe we may call radiators, whose
double function is (a) to transform the elec-
trical energy, into heat, and (b) to transmits
hot han fFsF Fha RTr
Now, let US proceed to estimate what this
heat will cost per hour when maintained in
the manner above outlined. 1t has been
shown that the heat per hour must De SO4, 231
heat units, and as the heat equivalent of one
horse power per hour is 2,555 heat units, the
horse power of the electrical current would
be SOL 81, divided by 256j, or 3l3.5. Taking
the efficiency of the dynamo and line at s.
per cent that is, allowing for a loss of l5 per
cent In converting the mechanical into
electrical energy, the horse power of the en-
gine driving the dynamo must be 3i3.5 di-
vided by .S5, or 1858 net, on "brake" horse
power, which is that power delivered at the
rim Of the engine pulley, and does not in
clude the friction of the engine itself Tho
average engine likely to be used for this
work will maintain a horse power for an
hour, with an expenditure of "a pounds of
coal, and to maintain 358.S horse power will
require evidently 36S.S multiplied by 215 or
922 pounds. From this we can readily calCu-
late the cost per hour, for if a ton of coal
cost 81 80, one pound would cost S0O09 and
go pounds would cost So, or 81 cents. By
only S% cents, so the electrical heating costs
ten times as much
The Advantages Inconsiderable.
Now, are the advantages secured by using
electricity sufficiently great to Offset such an
costf 1t is hard to see what these
advantages are-possibly little greater
facility in regulating the temperature, less
steam fitting and danger OF loss from leak
age of water and few minor items OF not
much importance and that is all.
The comparative directneSs Of the two
systems may be shown graphically by the
figure accompanying this article, in which
the lines represent conditions OF the energy
In the several steps of transmission, while
the small circles represent the machines or
appliances by means of which the trans
formation is accomplished. The common
source of heat is, OF course, in both Cases
coal and the common point to which the
heat is transmitted is the air in the several
rooms. The upper course represents the
steam system, the lower the electrical plan.
1t will be seen that the steam system takes
the heat directly to the point OF application
without any transformation Whatever, W nile
the electrical system requires that the heat
energy must pass through three tranSiorna-
tion5, two OF hIcn are accompanied by Un-
avoidable losses, before we can get it into
the necessary form Tor utilizing.
Nothing has here .been said as to the rela-
tive cost of the two plants and OF the outlay
for wages wear anu tear, interest or depre-
citation, which are plainly in favor OF steam.
The more direct systems can never be re-
placed by the electric current until the
problem of generating electricity directly
rom coal is solved and the question will
sven then depend on the cost of production
)f the current as this elements the ultimate
es5 by which all inventions or processes
ItaQd or fall WILLIAM XHIGHAM