Scientific American Supplement, No. 803, May 23, 1891Various
Science
Scientific American Supplement, No. 803, May 23, 1891
Various
Science -- Periodicals
It was this reduction of wastes that made the Newcomen engine so much
superior to that of Savery. The latter was by far the simpler and less
costly construction; but its enormous losses, both of heat and of
power, mainly the former, however, made it an extravagant expenditure
of money to buy and use it. The Newcomen engine, costly and cumbrous,
comparatively, nevertheless wasted so much less heat and steam and
fuel that no one could afford to buy the cheaper machine. Before
considering what Watt accomplished, we may find it profitable to
examine into the nature of the wastes which characterized this later
and better machine on which he effected his improvements.
The Newcomen engine consisted of a steam boiler, a steam cylinder, a
beam and a set of pumps. By making the boiler do its work separately,
the engine acting independently, and the pumps as a detached portion
of the mechanism, this inventor had reduced to an enormous extent
those wastes of heat and of steam and of fuel which were unavoidable
in the older machines in which all these parts were represented by a
single vessel, or by two at most, in each element. In the Savery
engine, the steam entering first heated up the interior of the working
vessel to its own temperature, and held it at that temperature in
spite of the cooling influence of the water present. This consumed
large quantities of heat. It then was compelled to surrender probably
much greater quantities still to the water itself, coming in direct
contact as it did with its surface. If the water was agitated, either
by the currents produced during its ingress or by the impact of the
steam entering the vessel, this heating action penetrated to
considerable depths and perhaps even warmed the whole mass very far
above its initial temperature. This constituted another and a very
serious loss. Then, again, as the water was gradually driven out of
the containing vessel by the steam pressing on its surface, new
portions of the vessel and new masses of water were continually
brought in contact with the hot steam, taking its full temperature,
and thus, often, probably, finally heating the whole mass of the
forcing vessel, and a large proportion of the water as well, up to the
temperature, approximately at least, of the steam itself. Thus in many
instances, if not always, vastly more heat and steam were wasted, in
this undesirable heating of water and forcing vessel, than were
usefully employed in the legitimate work of raising the water to a
higher level. In fact, in some cases in which these quantities were
measured, the wastes were one hundred times as much as the work done.
One per cent. of the heat supplied did the work; while ninety-nine per
cent. was thrown away. One dollar or one shilling expended for fuel to
do the work was accompanied by an expenditure of ninety-nine dollars
or shillings thrown away, because of the imperfections of the system
and machine. The whole history of the development of the steam engine
Public-domain text, read in full here on John Shaqi.
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