The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1841-10-15 00:00:00

THE POLYTECHNIC SOCITEY.

The general monthly meeting of this Society took place on
Tuesday evening, at the Royal Institution, Colquit-street,
and was numerously attended. Mr. John Grantham, Pre-
sident of the Society, occupied the chair, and called on
C. W. Williams, Esq. for his promised communication

ON INCREASING THE EVAPORATING POWER OF BOILERS

Mr. WILLIAMS, who was provided with a number of
working models and other apparatus, wherewith to illustrate
his views, addressed the meeting in a very clear and scientific
manner on this important subject, developing a most inter-
esting discovery of his own, which, (already practically
tested,) will be extremely valuable as effecting a more rapid
generation of steam without increasing the size of the vessel,
or the requirement of additional fuel. The question, he
said, involved the improvement of our boilers by a very sim-
ple contrivance, whether as applied to land engines, or to the
advancement of steam navigation. There were two leading
consideration) in the application of fuel, which were un-
happily confounded—one the generation of heat, and the
other its judicious application. The first appertained more
peculiarly to chemical science, which it was not his present
object to dwell upon ; and the second to mechanical appli-
ance, to which he should more immediately address himself.
The object in view was to transmit the greatest possible amount
of heat for the generation of steam, with a given quantity of
fuel. Heat was imparted by two distinct media, namely,
radiation and conduction. By radiation, heat was conveyed
to bodies not placed in contact with the burning matter or
actual flame, but at some short distance from it, as was evinced
by placing the hand pretty close to the flame of a candle, or
near a fire. By conduction, heat was conveyed by metal or
other substances not consumable: as. for instance, by a
boiler placed on a fire, or a piece of wire put into a fire, or
the flame of a candle, and which would so conduct it
to the hand that held it, that it must soon be relin-
quished. In the heating of boilers, to cause the ebulition
of water, both modes were necessarily operative. In
radiation the heat evolved proceeded in direct lines, or radii
from the combustion to the boiler or other body exposed to
it. It a thermometer were placed with the ball near the
candle, though not touching it, the mercury would rise by
radiation ; but if placed immediately over the flame the
heating would be greater, but different in the mode ; for in
this case it was not fairly radiation, but a compound medium,
radiation and the heated and ascending gas being combined.
The speaker then exhibited the model of a boiler with its
tortuous flues, through which the several gasses passed ; and
expressed his conviction that nine-tenths of the heat in
marine and land engine-boilers was immediately received from
the furnace, and not from the gasses, which might be. made
available to the same end by an improved construction of
boiler. The general opinion of parties working steam-engines
was, that to add an inch to the furnace would add to the
heating of the whole boiler; but this, he considered, was
treating the boiler with great neglect, for the object could be
accomplished without such increase of the furnace. He then
proceeded to describe the principle and effect of his improve-
ment which he illustrated by a small plate of metal peforated
in the centre in a round hole, into which a moveable iron pin
was inserted, projecting on either side. The means of con-
ducting heat to water in boilers had been much neglected,
reliance being almost solely placed on effecting the object in.
view by increasing the size and immediate heating power of
the furnace, to the disregard of the use and economising of
the heating gasses. His plan was to insert a number of iron
pins through the plates of the boiler, one end of them pro-
jecting into the flue, and the other into the water in the
boiler. These pins, exposed at one end to the heat in the
flue, became hot, and acted as powerful conductors, through
the boiler plates, of the heat into the water. Hitherto, the
question of the mere smooth surface of the boiler exposed to
the flues had been alone considered; and the only remedy for
defective generation of steam was conceived to be an in-
crease of that surface, or of the furnace, or both. The pins,
however, thickly inserted, (which he had successfully
applied to the boiler of a steam-boat,) were found to arrest
the heating gasses in their progress along the plates of the
boiler, and greatly to hasten and maintain the heating
of the water and the consequent generation of steam.
A pin of half-an-inch in diameter projecting three inches into
the flue, gave a heating surface of 41 inches, and by its con-
ducting power and interior projection (as we understood the
speaker) that half-inch gave as much heat as 9 inches on the
outer surface of the plate. Air was a good conveyer, but a
bad conductor (or depositor) of heat; for it carried most of it
out of the chimney. His object was to arrest the heat in its
progress, and give it out at the right place. The current of
heat passing along the plates of the boiler rendered them only
tranverse conductors ; but the heated pins were longitudinal
conductors. The speaker here exhibited three small model
boilers, placed in a row, and detached from each other, but
purposed to be heated by one common round flue. He showed
a portion of a flue, equal in length and diameter to that under
one of them, and studded or bristled inside and out with
small pins or bolts; and stated that by placing this under
either of the boilers, he had found the evaporating power
greatly increased, with the same quantity of fuel be-
fore used. lie also showed several iron pins that had long
been experimentally in use in the boiler of a steam vessel
with great success. Ile had endeavoured to ascertain the
proper length of which they should be, so as to remain as du-
rable conductors of heat. One of seven inches in length
(about half of which projected inside the boiler, and the
other half into the flue) had become slightly oxidized. Ano-
ther, of 4 inches long, was so little affected that the smallest
mark of the hammer, which it originally bore, was distinctly
visible. He, therefore, considered about 4 inches to be the
proper length. These pins could be so applied that a super-
ficial foot of boiler plate was rendered equal in the property
of heating to a foot and a-half in the ordinary way. In other
words, there was an actual gain of 50 per cent. He further
illustrated his invention by three evaporating pans, one of
them with pins projecting into the boiler and also into the
flues, which he called double condurtors ; another with pins
or bolts, having merely a rounded head driven up in the in-
terior of the boiler to the surface of the plates, and projecting
like the others into the flue only,—called single conductors ;
and the third, a plain boiler, on the usual plan without any
such conductor. The first he had found the more powerful
in producing speedy evaporation ; though the second with
solid rounded heads like those of a brass nail were scarcely
inferior, inasmuch as the heat was strongly suffused in the
water, in radii from the beads or knobs in the boiler. The
third, or plain boiler, was greatly behind either in evapora-
ting power. A gas lamp was affixed at one end of the double
conducting pan, containing 22lbs. of water, and the evapora-
tion appeared to be rapid. With 30 feet of gas it had been
brought to the boiling point in 2 hours and 46 minutes. The
others required a longer time, and the evaporation was less
and the waste more. The following was the result of nume,
rous experiments

Waste
406
.. 320
.. 284

Common Pan
Single Conductors.... 7
D- ble Ditto 8