Improvements in Steam and Air Superheaters.
Year: 1892

page_text: Date of Application, 23rd June, 1892
Complete Specification Left. 13th Mar.. 1893-Accepted. 17th June. 1893
PROVISIONAL SPECIFICATION.
Improvements in Steam and Air Superheaters.
1, WILHELM SCHMIDT, of Henkel Villa, Wilhelmshöhe near Cassel, in the
Province of Hesse-Nassau, Kingdom of Prussia, Empire of Germany, Civil
Engineer do hereby declare the nature of this invention to be as follows:-
My invention relates to a superheater of an improved construction, which
prevents the walls of said superheater becoming injured by excessive heating.
The experiments made on the employment of superheated steam for steam engines
have yielded the result, that a sensible useful effect is obtained only at very high
temperatures (heating up to 572° and more), as at this temperature no condensation
takes place in the cylinder, even when a strong expansion is adopted.
It is obvious that such an elevated temperature easily injures the walls of the
superheater, which is liable to become red-hot; this must be prevented at any rate,
or explosions might be expected.
Therefore it is necessary to effectively cool the walls of the superheater,
especially at the place next to the furnace, where the combustion gases have their
highest temperature.
I have now attained this object, which was but imperfectly attained hitherto, by
three novel means, that is to say,
1. By introducing very wet steam into the superheater, which I accomplish by
making the steam to pass into the same directly from the steam-room of an ordinary
boiler;
2. By causing the steam to travel with a considerable velocity through the
superheater, which is constructed as a continuous coiled pipe, or a series of such
pipes;
3. By arranging the superheater in such a manner, that in the first part of the
same the most wet steam is subjected to the action of the hottest gases of combustion,
thus effecting a thorough cooling of the latter, and the steam travels through the
second part of the superheater in a direction opposite to that of the surrounding
combustion gases; during this last period the steam becomes actually superheated.
The form of the superheater which I have adopted moreover ensures a great
surface of contact between the steam and the walls surrounded by the combustion
gases, and thus increases the efficiency of the whole apparatus.
In order that my invention may be better understood, I will proceed to describe
the same by the aid of the accompanying drawings, in which:
Fig. 1 is a sectional elevation of a superheater constructed according to my
improvements, in which spirally coiled pipes are employed.
Fig. 2 is a similar view of another superheater constructed substantially in the
same manner, and arranged directly on the top of a boiler.
Fig. 3 is likewise a central sectional elevation of a modification in which helically
coiled pipes are employed.
Similar letters refer to similar parts throughout the several views.
In Fig. 1 the wet steam coming directly from a boiler enters through the pipe a
into the interior spirally coiled pipe a', which is placed vertically and centrally
over the furnace c. The turns of the spiral are closely in contact with each other,
so that the combustion-gases can only ascend inside the coil a'. Thus it will be
seen that in this first coil of the superheater the direction in which the steam and
the combustion gases travel is the same. The latter strike against a cover k
provided at the top of the second spirally coiled pipe a², and descend in the annular
space between the coils a' and a². The steam, at the top of coiled pipe a', enters
the connecting tube e, and thus arrives at the top of the second coiled pipe a², through
which it passes from top to botton.. This spiral coil is arranged substantially in

page_text: the same manner as coil a', each two consecutive convolutions of the spiral being in
close contact. It will be observed that in this second coil the steam flows likewise
in the same direction as the combustion gases heating the coil. The steam having
travelled through the described path, is very nearly superheated, and the com-
bustion gases are strongly cooled, yet not so much as to prevent their employment
for heating the steam once more. The latter proceeds, through a connecting pipe a¹,
to the top of the last, exterior spirally coiled pipe a³. The convolutions of this coil
need not be in contact with each other, and I prefer to place them a small distance
apart, as shown. By this arrangement the combustion gases, which in this last
part of the apparatus travel opposite to the steam, may heat the latter more
thoroughly. Finally the steam, being perfectly superheated, leaves the apparatus
by the pipe f. It will be seen that the steam, as it approaches the end of coil a³, is
subjected to more intense heat.
In Fig. 2 I have shown a form of construction in which the superheater is
attached directly to the top of a boiler of the "Field" type, the gases proceeding
from the furnace of this boiler being also utilized for heating the coils of the
superheater. By this arrangement a considerable loss of heat by radiation is
prevented.
bis a boiler of the "Field" type, and the tube through which the combustion gases
ascend to the superheater. A pipe d leads the wet steam from the boiler into
the innermost coiled pipe a', and the construction of the two coils a¹ and a², and the
manner of leading the steam through the same, are exactly the same as described
with reference to Fig. 1. The difference in the construction of the superheater
resides especially in the arrangement of the exterior coiled pipe a³. Instead of
employing a single coil, but of greater diameter, as shown at Fig. 1, I arrange two
parallel spiral coils a³, into which the steam is introduced simultaneously through
the pipe a, and which it leaves at the bottom through the pipe f. The operation
and effect of this apparatus corresponds exactly to those of the form of construction
described in the first place, and therefore does not require any further explanation.
In the modification illustrated by Fig. 3 I employ a superheater of a somewhat
different construction, and have also shown that a continuous shell may be employed
for the boiler (the construction of which is not altered) and the superheater. The
latter is constructed in the following manner: It consists of a series of helically
coiled pipes arranged in horizontal planes one above the other, and connected
alternately at their outer ends by means of connecting pipés i, and at their inner
ends by means of similar pipes . Two of the adjoining helically coiled pipes,
however, are not connected with each other, but the lower of the same, being the
top coil r, connects with the uppermost of the coils by means of the pipe a'.
The lowest of the coils is in communication with the pipe f through which the
superheated steam leaves the apparatus. The combustion gases are directed in
such manner as to strike chiefly against the convolutions of the helical coils, as
indicated on the drawing.
The wet steam coming from boiler proceeds through pipe d to the undermost
helical coiled pipe r, passes through the same and then ascends to the second
coil and so on, leaving finally the uppermost coil by the pipe at and proceeding
to the top coil. Up to this point the steam has travelled in the same direction
as the combustion gases. Now, in order to superheat said steam completely, it is
made to pass through the helical coiled pipes from the top to the bottom, that is
to say, opposite to the path of the combustion gases. The steam, being completely
superheated by this arrangement, leaves the apparatus by the pipe f
The same arrangements which I have described with reference to their application
for superheating wet steam for steam engines, may be also employed for super-
heating moist air for steam-and-air engines.
Dated this 20th day of June 1892.
WILHELM SCHMIDT,
By H. F. Boughton, M.I. Mech. E.,
Commercial Street, Sheffield, Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Steam and Air Superheaters.
I, WILHELM SCHMIDT, of Villa Heukel, Wilhelmshöhe near Cassel, in the
Province of Hesse-Nassau, Kingdom of Prussia, Germany, Civil Engineer do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
My invention relates to a superheater of an improved construction, which
prevents the walls of said superheater becoming injured by excessive heating.
The experiments made on the employment of superheated steam for steam
engines have yielded the result, that a sensible useful effect is obtained only at
very high temperatures (heating up to 600° F. & more) as at this temperature no
condensation takes place in the cylinder, even when a strong expansion is adopted.
It is obvious that such an elevated temperature easily injures the walls of the
superheater, which is liable to become red-hot; this must be prevented at any
rate, or explosions might be expected.
Therefore it is necessary to effectively cool the walls of the superheater, especially
at the place next to the furnace, where the combustion gases have their highest
temperature.
I have now attained this object, which was but imperfectly attained hitherto, by
three novel means, that is to say,
1. By introducing very wet steam into the superheater, which I accomplish by
making the steam to pass into the same directly from the steam-space of an ordinary
boiler;
2. By causing the steam to travel with a considerable velocity through the
superheater, which is constructed as a continuous coiled tube, or a series of such
tubes;
3. By arranging the superheater in such a manner, that in the first part of the
same the wettest steam is subjected to the action of the hottest gases of combustion,
thus absorbing the greatest part of their heat, whereas the steam travels through
the second part of the superheater in a direction opposite to that of the surrounding
combustion gases; during this last period the steam becomes actually super-
heated.
The form of the superheater which I have adopted moreover ensures a great
surface of contact between the steam and the walls surrounded by the combustion
gases, and thus increases the efficiency of the whole apparatus.
In order that my meaning may be fully understood, I will proceed to describe
my invention by the aid of the drawings sent in with the Provisional Specification,
in which:
Fig. 1 is a sectional elevation of a superheater constructed according to my
improvements, in which spiral coiled tubes are employed.
Fig. 2 is a similar view of another superheater constructed substantially in the
same manner, and provided directly on the top of a boiler.
Fig. 3 is likewise a central sectional elevation of a modification in which tubes
coiled in form of watch springs are employed.
Similar letters refer to similar parts throughout the several views.
In Fig. 1 the wet steam coming directly from a boiler enters through the pipe a
into the interior spiral coiled pipe a¹ which is placed vertically and centrally over
the furnace c. The turns of the spiral are closely in contact with each other, so
that the combustion-gases can only ascend inside the coil a'. Thus it will be seen
that in this first coil of the superheater the direction in which the steam and the
combustion gases travel is the same. The latter strike against a cover k provided
at the top of the second spiral coiled pipe a², and descend in the annular space
between the coils a¹ and a². The steam, at the top of coiled tube a¹, enters the

page_text: e,
connecting tube and thus arrives at the top of the second coiled tube a², through
which it passes from top to bottom. This spiral coil is arranged substantially in
the same manner as coil a', each two consecutive convolutions of the spiral being
in close contact. It will be observed that in this second coil the steam flows
likewise in the same direction as the combustion gases heating the coil. The steam
having travelled through the described path, is very nearly superheated, and the
combustion gases are strongly cooled, yet not so much, as to prevent their employ-
ment for heating the steam once more. The latter proceeds, through a connecting
tube a', to the top of the last, exterior spiral coiled tube a³. The turns of this
coil need not be in contact with each other, and I prefer to place them a small
distance apart, as shown. By this arrangement the combustion gases, which in
this last part of the apparatus travel opposite to the steam, may heat the latter
more thoroughly. Finally the steam, being perfectly superheated, leaves the
apparatus by the pipe f. It will be seen that the steam as it approaches the end
of coil a³, is subjected successively to more intense heat, because the heat of the
combustion gases increases from above to below.
In Fig. 2 I have shown a form of construction in which the superheater is
attached directly to the top of a boiler of the "Field" type, the gases proceeding
from the furnace of this boiler being also utilized for heating the coils of the
superheater. By this arrangement à considerable loss of heat by radiation is
prevented.
b is a boiler of the "Field" type, and the tube through which the combustion
gases ascend to the superheater. A pipe d leads the wet steam from the boiler b
into the innermost coiled pipe a¹, and the construction of the two coils a¹ and a²,
and the manner of leading the steam through the same, are exactly the same as
described with reference to Fig. 1. The difference in the construction of the
superheater resides especially in the arrangement of the exterior coiled pipe a³.
Instead of employing a single coil, but of greater diameter, as shown at Fig. 1,
I arrange two parallel spiral coils a³, into which the steam is introduced
simultaneously through the pipe a', and which it leaves at the bottom through the
pipe f. The operation and effect of this apparatus corresponds exactly to those
of the form of construction described in the first place, and therefore does not
require any further explanation.
r
In the modification illustrated by Fig. 3 I employ a superheater of a somewhat
different construction, and have also shown that a continuous shell may be
employed for the boiler (the construction of which is not altered) and the super-
heater. The latter is constructed in the following manner: It consists of a series
of tubes and coiled in a form of watch springs arranged in horizontal planes
one above the other, and connected alternately at their outer ends by means of
connecting pipes i, and at their inner ends by means of similar pipes . Two of
the adjoining helical coiled pipes, however are not connected with each other, but
the lower of the same, being the top coil r, connects with the uppermost of the
coils by means of the pipe a. The undermost of the coils is in communication
with the pipe f, through which the superheated steam leaves the apparatus. The
combustion gases are directed in such a manner as to strike chiefly against the
turns of the helical coils, as indicated on the drawing.
?"
The wet steam coming from boiler proceeds through pipe d to the undermost
coiled tube r, passes through the same and then ascends to the second coil and
so on, leaving finally the uppermost coil by the pipe a' and proceeding to the top
coil. Up to this point the steam has travelled in the same direction as the
combustion gases. Now, in order to superheat said steam completely, it is made to
pass through the coiled tubes r¹ from the top to the bottom, that is to say, opposite
to the path of the combustion gases. The steam, being completely superheated by
this arrangement, leaves the apparatus by the tube f.
The same arrangements which I have described with reference to their application
for superheating wet steam for steam engines, may be also employed for super-
heating moist air for steam- and air-engines.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In superheaters: The combination of two series of coiled tubes, in one of
which, exposed at first to the action of the combustion gases the wet steam passes
in the same direction as the combustion gases, absorbing the greatest part of their
heat and preventing the tubes from being injured by the heat of the combustion
gases, and in the second of which the steam, passing in the opposite direction to
the course of the combustion gases, becomes actually superheated, substantially
and for the purpose as described.
2. In superheaters of the kind described, the combination with a cover k, of two
spirally coiled tubes a¹ and a², the turns of which touch each other, forming an
annular space for the passage of the raised combustion gases, so arranged, that the
wet steam passes them in the same direction as that of the combustion gases, for
the purpose as described.
3. In superheaters of the kind described, the combination with the spirally coiled
tubes a' and a², of one or more spirally coiled tubes a³, the turns of which are in
contact with each other, or are separated, so arranged, that the steam passes them
in the direction opposite to the course of the combustion gases, for the purpose as
described.
4. In superheaters of the kind described, the combination of two series of tubes r
and, coiled in form of watch springs, arranged in such a manner, that in the
tubes r, struck at first by the combustion gases, the steam is passing in the same
direction and in the tubes the steam is passing in the opposite direction to the
course of the combustion gases, for the purpose as described.
Dated this 11th day of March 1893.
WILHELM SCHMIDT,
By Robert Deissler,
38, Alexander Strasse, Berlin, C., Germany, Agent for the Applicant.