Improved Apparatus for Heating a Stream of Water.
Year: 1895

page_text: Date of Application, 23rd Aug., 1895
Complete Specification Left, 23rd May, 1896-Accepted, 11th July, 1396
PROVISIONAL SPECIFICATION.
Improved Apparatus for Heating a Stream of Water.
I, HUGO JUNKERS of 33, Wilhelmstrasse Dessau in the Empire of Germany,
Civil Engineer, do hereby declare the nature of this invention to be as follows:-
This invention has for its object to convey, through metallic walls as completely
as possible to a constantly flowing stream of water, the heat produced by the
combustion of liquid or gaseous fuel, in order to obtain in the shortest time and
at the smallest cost, warm water of any desired temperature and quantity for bath
and other like purposes.
The apparatus consists essentially of a long vertical pipe which forms the
combustion chamber and widens out into a chamber which is closed at the top,
from which chamber narrow tubes arranged in a ring round the combustion pipe,
convey the gases of combustion vertically or obliquely downwards to the outside,
either directly or by means of an annular smoke chamber with a lateral exit, or by
means of an outside casing which carries the gases upwards into the outer air.
The combustion pipe is surrounded by another somewhat wider tube and the water
is conveyed from a suitable pipe into the annular space thus formed by means of
a distributing ring, having holes opening into said space. The water then rises
in the lower narrow part of the annular water chamber formed by the two pipes
as aforesaid under the pressure of the main into the upper and wider part of said
water chamber through which runs the series of tubes and in which chamber the
direction of movement of the water is opposite to that of the gases in the tubes
therein. The water thus heated is discharged from above the enclosed upper end
of the combustion chamber through a suitable exit pipe. When very small tubes
for the gases of combustion are employed, they easily become stopped by the
water condensed and deposited from the waste gases. This is avoided by cutting
these pipes off obliquely at their lower part, so that the water deposited in the
pipes from the gases of combustion easily trickles out and is caught in a cup or
annular receptacle. This cup also serves for stiffening the outer casing.
For heating the apparatus, either liquid or gaseous fuel may be employed.
This apparatus for heating a stream of water combines in itself a number of
advantages which are founded on the following principles.
The flame can develop upwards free and unimpededly in the long vertical
combustion pipe, so that a thorough combustion takes place before the flame comes
In this
in contact with the cool walls of the tubes for the gases of combustion.
manner not only incomplete combustion but also the formation of soot is avoided,
and all the drawbacks connected therewith are dispensed with, more particularly
the bad conducting of heat produced by the formation of layers of soot, and the
defective draught caused by the pipes being stopped with soot and the trouble
and cost resulting from the frequent necessary cleaning. Finally noxious and bad
smelling gases arising from incomplete combustion are avoided. The long tubular
form of the vertical combustion chamber, and the high temperature of the gases
contained in it produce a powerful upward draught of the latter, so that the heating
apparatus develops a strong draught in spite of the tendency of the gases, which
move downwards in the tubes to act in an opposite direction, this tendency being
however only small on account of the low temperature and the short distance to
be travelled. The vertical combustion pipe forms accordingly to a certain extent
a combined cbimney which renders superfluous a special chimney for drawing in

page_text: the necessary air for combustion. The gases of combustion may be cooled down
to their original temperature without endangering complete combustion through
insufficient air supply. If a separate chimney be employed the action of the same,
as a draught producer, involves the necessity of the waste gases on their
discharge from the stove having a somewhat high temperature, which prevents a
thorough utilization of the heat, and may cause disturbances in the working of the
stove, such for instance, as loss of heat and a down draught. The special
arrangement of the combustion chamber which acts as a combined chimney forms
thus an essential characteristic which particularly distinguishes this heating
apparatus from others.
By the hot gases being carried downwards through a series of small tubes, the
gases are evenly distributed and cooled down in all the tubes in such a way that
any tendency to interrupt the regular working is automatically removed. This is
owing to the following reasous-If a current of gases rising in a tube is
distributed in two small upwardly-directed pipes of equal capacity and position,
the distribution of the gases in both pipes is equal, when the dranght of the gases
themselves is equally great in both pipes. The latter however depends upon the
mean temperature of the gases. As soon as the temperature is greater in one
pipe than in the other, the pipe with the higher temperature will show a stronger
draught, and consequently a greater speed of the gas. A greater speed however
causes a slower cooling action, and a further increase of the mean temperature.
This again has as a consequence an increase in the speed, so that an increase in
the action takes place of itself, until the increased frictional resistance produced
by the increased speed equalises the greater draught, and so a stable equipoise is
produced from the unstable or unequal one. This action of an unequal distribution
of the draught in the separate pipes, which always takes place when gases pass in
an upwardly rising direction through a system of cooling pipes is more particularly
observable in cases where the draught of the gases in the pipes alone is large in
proportion to the total power impelling the gases. The case may thus arise that
in a number of pipes the gases do not even rise but move downwards.
unfavourable action of the draught is removed, and even changed into an opposite.
one, if the gases be conveyed from above downwards through the series of pipes.
Any increased draught produced by an increase of temperature in one of the
pipes then acts against the movement of the gases in this pipe, until its mean
temperature is again equal to that of the remaining pipes. The distribution of
the cooling over all the pipes is thus to a certain extent in a-condition of stable
equipoise. Further an energetic cooling action of the walls of the pipes is obtained
in addition to this equal distribution by conducting the gases in a downward
direction and for the following reasons:-
This
The particles of gas adjacent to the walls of the tubes undergo a stronger;
cooling than those in the centre. The consequence of this is that the outer
particles become specifically heavier than the centre ones, and have a tendency
to fall relatively to the centre ones. This has an extremely favourable effect in
the case of a downwardly directed current of gas, as on the one hand the hot
gaseous particles situated in the centre of the pipes are held back, whilst those.
against the walls of the pipes being cooler pass down with increased speed, and to
a certain extent make way for the warmer particles to come against the cooling,
walls, and thus produce an increased cooling action by this vigorous movement.
Exactly an opposite action takes place when the gases travel from below upwards,
as here the greater draught of the beated gas particles in the centre of the tube
causes an accelerated carrying off of these particles in a still uncooled condition,.
whilst the higher specific gravity of the cooler particles of gas against the walls of
the pipe exerts a delaying action on the latter and thereby diminishes the effective-
ness of the cooling surface.
The gases of combustion move in this system of cooling tubes, where naturally:
the main transfer of heat takes place, from above downwards, that is to say in an;
opposite direction to the liquid which is inserted from below, so that the coolest

page_text: gases encounter the coolest water, by which means as is well known, the maximum
action is attained (counter current principle). This also assists in a good
utilisation of the fuel. The warmth of the water of combustion may be recovered
by condensation, if the gases are allowed to escape at a low temperature. By this
means a considerable recovery of heat may be obtained amounting in case of
ordinary lighting gas to about 10%. The possibility of effecting this condensation
is afforded in this improved heating apparatus on the one hand by the combined
or inserted chimney which allows of the waste gases being considerably cooled,
and on the other hand by the counter current action of water and gas. This
means indeed in consequence of the lower specific gravity of steam (or water vapour)
a slight diminution of the draught, which however need not be taken into account
in view of the strong draught. Ordinary heating apparatuses allow the steam to
escape unutilised in consequence of the high temperatures of the draught. If
however this steam be recovered the percentage of loss in the draught would
become very apparent. The steam- and air-bubbles developed in the water may
rise unimpededly everywhere, and conveniently escape along the conical cover.
The heating surfaces are prevented from becoming uncovered by the liquid, and
the danger of their being thus burnt through is avoided.
The heating tubes are narrow and thereby produce a more favourable radiation
of heat than wider tubes. They may have a round section, or an elliptical, oval
or flattened one. The flat section is to be preferred, because in flat tubes the
distance of the centre of the gases from the wall is smaller, and consequently the
cooling action with a given surface is greater. This advantage is especially
utilised in narrow tubes if they are arranged at equal distances apart and if the
inner walls of the same are also at equal distances. This condition is fulfilled if
the walls of the tubes facing one another are formed according to evolvents of a
circle as evolvents of the same circle are parallel to one another. Such tubes
have also the property in consequence of their curved walls of being more resistant
to outside pressure. The evolvents may be approximated to arcs of circles. The
arrangement described of small tubes is in this apparatus rendered possible by
the special manner in which the flames are conducted, for, as already expressly
stated, any formation of soot under normal circumstances is not to be feared, and
the water condensed or deposited can easily run away.
Dated this 22nd day of August 1895.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.
Improved Apparatus for Heating a Stream of Water.
I, HUGO JUNKERS of 33, Wilhelmstrasse Dessau in the Empire of 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 :-
This invention has for its object to convey through metallic walls as completely
as possible to a constantly flowing stream of water, the heat produced by the
combustion of liquid or gaseous fuel, in order to obtain in the shortest time and at
the smallest cost, warm water of any desired temperature and quantity for bath
and other like purposes.
The apparatus consists essentially of a long vertical pipe b, Figure 1 of the
accompanying drawings, which forms the combustion chamber and widens out into
a chamber which is closed at the top, from which chamber narrow tubes k
arrauged in a ring round the combustion pipe b convey the gases of combustion
vertically or obliquely downwards to the outside, either directly or by means of an

page_text: .
annular smoke chamber m with a lateral exit, as shown in dotted lines, or by
means of an outside casing o which carries the gases upwards into the outer air.
The combusticn pipe 6 is surrounded by another somewhat wider tube c and the
water is conveyed from a suitable pipe d into the annular space thus formed by-
means of a distributing ring g, having holes opening into said space. The water
then rises in the lower narrow part of the annular water chamber formed by the
two pipes b and c as aforesaid under the pressure of the main into the upper and
wider part of said water chamber through which runs the series of tubes k and in
which chamber the direction of movement of the water is opposite to that of the
gases in the tubes therein. The water thus heated is discharged from above the
enclosed upper end of the combustion chamber through a suitable exit pipe n.
When very small tubes for the gases of combustion are employed they easily
become stopped by the water condensed and deposited from the waste gases. This
is avoided by cutting these pipes off obliquely at their lower part, so that the
water deposited in the pipes from the gases of combustion easily trickles out and
is caught in a cup or annular receptacle p. This cup also serves for stiffening the
outer casing p.
For heating the apparatus either liquid or gaseous fuel may be employed.
In the example shown in the drawing, a gas burner e is employed which is fed
by a pipe f.
This apparatus for heating a stream of water combines in itself a number of
advantages which are founded on the following principles.
The flame can develop upwards free and unimpededly in the long vertical
combustion pipe b so that a thorough combustion takes place before the flame
comes in contact with the cool walls of the tubes k for the gases of combustion.
In this manner not only incomplete combustion but also the formation of soot is
avoided, and all the drawbacks connected therewith are dispensed with, more
particularly the bad conducting of heat produced by the formation of layers of
soot, and the defective draught caused by the pipes being stopped with soot and
the trouble and cost resulting from the frequent necessary cleaning. Finally
noxious and bad smelling gases arising from incomplete combustion are avoided.
The long tubular form of the vertical combustion chamber, and the high
temperature of the gases contained in it produce a powerful upward draught of the
latter so that the heating apparatus develops a strong draught in spite of the
tendency of the gases, which move downwards in the tubes k, to act in an opposite
direction, this tendency being however only small on account of the low temperature
and the short distance to be travelled. The vertical combustion pipe forms
accordingly, to a certain extent, a combined chimney which renders superfluous a
special chimney for drawing in the necessary air for combustion. The gases of
combustion may be cooled down to their original temperature without endangering
complete combustion through insufficient air supply. If a separate chimney be
employed the action of the same, as a draught producer, involves the necessity of
the waste gases on their discharge from the stove having a somewhat high
temperature, which prevents a thorough utilization of the heat, and may cause
disturbances in the working of the stove, such for instance, as loss of heat and a
down draught. The special arrangement of the combustion chamber. which acts
as a combined chimney forms thus an essential characteristic which particularly
distinguishes this heating apparatus from others.
By the hot gases being carried downwards through a series of small tubes k the
gases are evenly distributed and cooled down in all the tubes in such a way that
any tendency to interrupt the regular working is automatically removed. This is
owing to the following reasons.-
-If a
current of gases rising in a tube is
distributed in two small upwardly-directed pipes of equal capacity and position,
the distribution of the gases in both pipes is equal, when the draught of the gases
themselves is equally great in both pipes. The latter however depends upon the
mean temperature of the gases. As soon as the temperature is greater in one pipe
than in the other, the pipe with the higher temperature will show a stronger

page_text: draught, and consequently a greater speed of the gas. A greater speed however
causes a slower cooling action, and a further increase of the mean temperature.
This again has as a consequence an increase in the speed, so that an increase in the
action takes place of itself, until the increased frictional resistance produced by
the increased speed equalises the greater draught, and so a stable equipoise is
produced from the unstable or unequal one. This action of an unequal distribution
of the draught in the separate pipes, which always takes place when gases pass in
an upwardly rising direction through a system of cooling pipes is more particularly
observable in cases where the draught of the gases in the pipes alone is large in
proportion to the total power impelling the gases. The case may thus arise that.
in a number of pipes the gases do not even rise but move downwards. This
unfavourable action of the draught is removed, and even changed into an opposite
one, if the gases be conveyed from above downwards through the series of pipes.
Any increased draught produced by an increase of temperature in one of the
pipes then acts against the movement of the gases in this pipe, until its mean
temperature is again equal to that of the remaining pipes. The distribution of the
cooling over all the pipes is thus to a certain extent in a condition of stable
equipoise. Further an energetic cooling action of the walls of the pipes is
obtained in addition to this equal distribution by conducting the gases in a.
downward direction and for the following reasons:-
The particles of gas adjacent to the walls of the tubes undergo a stronger
cooling than those in the centre. The consequence of this is that the outer:
particles become specifically heavier than the centre ones, and have a tendency to
fall relatively to the centre ones. This has an extremely favourable effect in the
case of a downwardly directed current of gas, as the hot gaseous particles situated
in the centre of the pipes are held back, whilst those against the walls of the pipes.
being cooler pass down with increased speed, and to a certain extent inake way for '
the warmer particles to come against the cooling walls, and thus produce an.
increased cooling action by this vigorous movement. Exactly an opposite action.
takes place when the gases travel from below upwards, as here the greater draught
of the heated gas particles in the centre of the tube causes an accelerated carrying
off of these particles in a still uncooled condition, whilst the higher specific.
gravity of the cooler particles of gas against the walls of the pipe exerts a
delaying action on the latter and thereby diminishes the effectiveness of the
cooling surface.
The gases of combustion move in this system of cooling-tubes, where naturally
the main transfer of heat takes place, from above downwards, that is to say, in an
opposite direction to the liquid wbich is inserted from below, so that the coolest.
gases encounter the coolest water, by which means as is well known, the maximum
action is attained (counter current principle). This also assists in a good utilisation
of the fuel. The warmth of the water of combustion may be recovered by
condensation, if the gases are allowed to escape at a low temperature. By this.
means a considerable recovery of heat may be obtained amounting in case of
ordinary lighting gas to about 10%. The possibility of effecting this condensation
is afforded in this improved heating apparatus on the one hand by the combined or
inserted chimney which allows of the waste gases being considerably cooled, and
This means.
on the other hand by the counter current action of water and gas.
indeed in consequence of the lower specific gravity of steam (or water vapour) a
slight diminution of the draught, which however need not be taken into account
in view of the strong draught. Ordinary heating apparatuses allow the steam to
escape unutilised in consequence of the high temperatures of the draught. If
bowever this steam be recovered the percentage of loss in the draught would
become very apparent. The steain- and air-bubbles developed in the water may
rise unimpededly everywhere, and conveniently escape along the conical cover.
The heating surfaces are prevented from becoming uncovered by the liquid, and
the danger of their being thus burnt through is avoided.
The heating tubes & are narrow and thereby produce a more favourable radiation
1
:
J
1

page_text: of heat than wider tubes. They may have a round section as shown in Figure 2
or an elliptical, oval or flattened one as shown in Figures 3 and 4. The flat
section is to be preferred because in flat tubes the distance of the centre of the
gases from the wall is smaller, and consequently the cooling action with a given
surface is greater. This advantage is especially utilised in narrow tubes if they
are arranged at equal distances apart and if the inner walls of the same are also at
equal distances. This condition is fulfilled if the walls of the tubes k facing one
another are formed according to evolvents of a circle (Figure 4) as evolvents of
of the same circle are parallel to one another. Such tubes have also the property
in consequence of their curved walls of being more resistant to outside pressure.
The evolvents may be approximated to arcs of circles. The arrangement described
of small tubes is in this apparatus rendered possible by the special manner in
which the flames are conducted, for, as already expressly stated, any formation of
soot under normal circumstances is not to be feared, and the water condensed or
deposited can easily run away.
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. An apparatus for heating liquid, characterized by the heating gases being
caused to rise in a central chimney-like elongated combustion chamber (6) having
at the top a widened chamber (i) and to then pass downwards therefrom through
short and small tubes (k) arranged around the said combustion chamber (b), so
that said gases thereby give up their heat to the water surrounding the heating
tubes, substantially as described.
2. In an apparatus for heating liquid such as described, heating tubes (k) formed
with a section approximating to evolvents of a circle, so that the walls of said
tubes have, as far as possible, an equal distance between them substantially as
described.
Dated this 22nd day of May 1896.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.