New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1905-06-15
WHY SUBWAY STAYS WARM
Electrical Po1Cer PoarS IN Billion
Heat Units a Dag.

In view of the general interest in the foulness
of the subway air. the following extract from
The Engineering News may be regarded by
many readers as particularly appropriate and
suggestive:
1t was, expected by the patrons of the New
York Subway that it would be warm in winter
and cool in summer. The air of the subway has
been decidedly warmer than the air of the
streets during the cold months that have just
passed, but that warmer weather has
come the subway air refuses to conform to ex-
pectations and predictions-t still remains
warmer than the air above ground. What is
the reason? Why is the subway not like a
cellar, a cave, shallow mine? The an
swer to this question is simple, though not self
evident In the subway we have great num-
Der of electrically driven trains almost constant
~ in motion, which is equivalent to saying that
they are consuming great quantities of power
But where does this power gof 1t is not De.
stroyed therefore this visible manifestation or
power is converted into the invisible manifesto
ton which we call heat. The electric motors
must overcome the journal friction of the axes
the rolling friction of the wheels the air frlc-
ton at the heads and sides of the cars ana
the inertia of the train at the time of starting
With the exception of the force used in over
coming inertia the power of the motors is eX-
pended in overcoming friction or, in other
words. is converted into heat. And, in the last
analysis the force used to overcome the
inertia Of the trains is converted into heat, Tor
when the brakes are set to retard the train the
heat developed at the surfaces of contact De-
tween the brake shoes and the tires is equiv,
alent to the electric energy originally expendeu
IN overcoming inertia Even TIE WOih oOiio W
the motors working against the resistance OF
gravity on an ascending grade is converted INTO
heat for, in a round trip of the train. the power
stored in ascending must be given back in de-
scending, and when given back it acts In over
coming the frictional resistances above cited
The electricity that is lost in TRANSMISSION
through the third rail is FRACTIONAL loss; hence
1t is converted into heat The multitude or IN
candescent lamps, both in the cars and along
the interior of the subway, are likewise neat
generators. So, too, the people who ride on
the trains, as well those who work IN the SUD-
way In a word, there is constant and large
conversion of fuel into heat
We have shown that there are more than
every twenty-four hours by the electric current
Possibly 10 per cent of this may be lost by con-
ducton through the roof and sides OF the SUP
way, still leaving 90O,0C0,0OO heat units. which
Is sufficient to heat the whole of the subway air
200 times a day to a temperature degrees
higher than the outside temperature.
The assumption has invariably been that pc
cause the electric motor and the electric light
produce no pollution of the air. therefore ven
used for traction could be ignored We believe
the computations above show the falsity of this
assumption. In previous installations OF electric
traction underground the traffic density, weight
of trains and size of motors have been small
compared with that in the New-York subway,
and the tunnels themselves have been compare
lively short Thus while there have been well
founded complaints of bad ventilation in some
of the earlier electric motor operated tunnels it
demonstrate that the heating effect of the cleo
trio power the subway air is matter that
should be foreseen and considered by the de-
signing engineers.