Improvements in Feed Water Heaters.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements in Feed Water Heaters.
I, JAMES YATE JOHNSON of 47 Lincolns Inn Fields, in the County of Middlesex,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by La Société Augustin Normand & Cie. Engineers
of 67 Rue du Perrey, Havre, in the Republic of France) and in what manner the same
is to be performed to be particularly described and ascertained in and by the
following statement :-
This invention relates to feed water heaters in which the water is heated under
pressure in its passage between the feed pump and the boiler, the heat being derived
either from the steam or from the gaseous products of combustion.
The transference of heat to water which is a poor conductor is rapidly augmented
or accelerated by agitating the water. In surface heaters in which the water passes
in the interior of the tubes it is consequently advantageous to provide obstacles in
the passage of the water so as to agitate the latter. Other things being equal, the
agitation and consequently the transference of heat augment in proportion to the
rapidity with which the water flows through the tubes.
In order to agitate the water and accelerate its speed in surface heaters the
apparatus according to this invention is arranged as hereinafter described.
In each tube of the heater there are placed obstacles or baffles for the purpose
of producing disturbance or agitation of the water. These obstacles may be formed
by plates forming helices or bent or folded so as to obstruct or deflect the stream of
water or by wires provided with rods or plates arranged at right angles to the
direction of their length, or concentric metallic or other rods preferably having
roughened surfaces. Any other suitable arrangement capable of producing a
disturbance or agitation of the water may be employed. For example tubes with
longitudinal ribs such as the Serve tubes may be employed in the improved heater
or tubes that are simply undulated or corrugated so as to present contractions and
enlargements. It is preferred however to employ for this purpose an arrange-
ment of plates threaded on a central rod or wire as hereinafter described with
reference to Figures 3 and 4 of the accompanying drawings.
And in order that the said invention may be fully understood I shall now proceed
more particularly to describe the same and for that purpose shall refer to the
several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
Figure 1 of the accompanying drawings represents in longitudinal or vertical
section a feed water heater tube provided with baffling arrangements according to
this invention and Figure 2 represents the tube in plan.
Figure 3 represents a modified arrangement of the tube in vertical or longitudinal
section this arrangement being represented in plan in Figure 4.
Figure 5 represents in vertical section (on the line XX' Figure 6) a feed water
heater apparatus constructed according to this invention and Figure 6 represents
the same partly in plan and partly in horizontal section on the line Y Y Figure 5.
According to the arrangement illustrated in Figures 1 and 2 the disturbance or
agitation of the water flowing through the heater tube V is produced by means
of a plate T twisted in the form of a helix and bent or folded at intervals as
indicated at T', Figure 1, in order to baffle or impede the flow of the water.
In the arrangement illustrated in Figures 3 and 4 the heater tube V is provided
with a straight central wire or rod S to which are attached at suitable distances
(say from about one to two and a half inches apart for example) thin plates S¹ cut
to a figure contained within the internal diameter of the tube as represented in
Figure 4 so as to leave contracted passages for the water at the edges of the plates,

page_text: The angles of these plates are arranged in different planes not being in the same
generating lines of the tube (Figure 4) so as to more effectually break up or deflect
the streams of water flowing through the passages formed between the said angles.
It is preferred to employ iron instead of copper for the central rods or wires S the
conductivity of the former metal being less and its rigidity greater than that of
copper. The apparatus employed to produce the agitation in each tube is not
designed to impart a more or less uniform mean temperature to the water but
enables the water to become gradually heated and to issue from the heating tube at
a temperature as near as possible to that of the steam outside the said tube. The
central wires S are bent at the upper ends in the form of an S as represented in
the drawing (Figure 3) in order to enable them to be secured in position by
plates R attached to the cover and bearing on the flexible or springy end of the
wire (Figure 3). A similar arrangement is employed in the case of the bent plate
or strip T employed in the arrangement illustrated in Figures 1 and 2. The
wires S provided with the diaphragms or baffle plates S¹ being introduced into the
vertical tubes V from the upper end it is simply necessary to remove the cover of
that part of the heater in order to enable the wires and plates to be removed and
to clean the tubes. As hereinbefore explained the agitation of the water is
greater in proportion as its speed is increased irrespective of the kind of device or
arrangement employed to produce the agitation.
In order to increase the speed or rate of flow of the water it is sufficient to
diminish the sectional area of the passage. This result is obtained by making the
heater as long as possible by combining a number of heaters together or more simply
by dividing a series or set of tubes into several parts presenting approximately
equal heating areas of surface and causing the water to pass through all the said
parts in succession.
This arrangement is illustrated in Figures 5 and 6 of the drawings. In these
figures A is a surface feed water heater arranged according to this invention. The
steam taken for instance from the lower intermediate reservoir of a multiple
expansion engine enters the apparatus at B and escapes at C after condensation on
the external surfaces of the tubes. The feed water from the feed pump enters the
lower end of the heater at D, flows up in a series of tubes on one side of the
apparatus then descends in a series of intermediate tubes and reascends in a third
series of tubes on the other side as indicated by the arrows in Figure 5 being
finally discharged from the upper end of the heater into a pipe E leading to the
boiler.
F is a trap or blow off apparatus for the discharge of the water of condensation
communicating with the heater at the lower part through a valve G provided for
the purpose of enabling the blow off apparatus to be examined without stopping
the heater and connected with the heater at the upper part through a pipe H
likewise provided with a valve or stop cock. An equilibrium of pressure is thus
enabled to be established between the heater A. and the blow off apparatus F the
level of the water in the latter being practically the same as in the heater A
provided that the valve is of suitable diameter.
The trap F may be of any system whatever. The one illustrated in the
drawing consists of a float moving vertically in a cylinder and actuating an
escape valve through a lever, the object of the lever being to lessen the power
necessary for lifting the valve.
A valve I communicating with the outlet through a branch pipe I¹ is provided
for the purpose of drawing off any excess of air contained in the steam that may
have accumulated in the heater and is placed as low down as possible.
The top plate or cover Q and the bottom plate Q₁ of the heater A are each
provided with diaphragms or partitions marked respectively a and b Figure 5
which divide the chambers formed in the said covers into two compartments and
direct the water in such a manner as to cause it to circulate in the tubes three
times as hereinbefore explained. The tube plates are rigid and the partitions a
and 6 fit as closely as possible against the surfaces of these plates between the

page_text: tubes so as to limit the number of tubes to which the water in each compartment
of the cover has access.
The elasticity necessary to allow for expansion and contraction is obtained by
means of the outer flanges and if necessary by a corrugation in the casing.
The air contained in the feed water and which is present in considerable quantity
in surface condensing engines has a tendency to greatly retard the transmission of
heat. In that part of the central or intermediate series of tubes in which the water
circulates per descensum this air tends to accumulate in such a manner as to almost
fill the tubes unless some provision is made for separating it from the water.
With this object the partition a in the cover Q is perforated with a hole c
Figure 5 of about one twenty fifth of an inch in diameter or of sufficient size to
allow the air to escape from the first or inlet compartment of the cover into the
second or outlet compartment under the influence of the slight difference in pressure
which exists between the two compartments but which is insufficient to allow of
any material escape of water. This hole may be situated at such a level as to
provide for a small cushion of air in order to obviate concussion. By means of
a similar arrangement the air may be expelled before it can enter the apparatus
but the presence of air in the ascending current is of much less consequence.
A partition & Figure 6 separates the space containing the lower part of the
series of tubes traversed by the water in the first instance, from the space con-
taining the other tubes. The lower part of the space e on one side of this
partition communicates at C with the automatic blow off or discharge apparatus F.
The space on the other side of this partition is connected at g with the discharge
or blow off of all the parts of the engine in which the steam is at a pressure
higher than that of the feed heater.
The water of these blow-offs is partially evaporated and more or less rapidly
acquires the temperature of saturation corresponding with the pressure of steam
in the heater and as it is constantly renewed the lower ends of the tubes in the
two last series traversed by the feed water are continually immersed in water at
a very high temperature. The whole of this water along with that resulting from
the condensation in the heater ultimately passes through the space e and is con-
siderably cooled before it leaves the apparatus.
In place of being divided into three parts the combination of tubes may be.
divided into two series only, the inlet and outlet of the feed water being arranged
at the same end of the casing and preferably at the lower end. It is true that this
arrangement has the effect of diminishing the speed of the water but it presents
the advantage of necessitating only one partition (such as a or b) in the end or
connecting chamber and the labour of remaking the rather troublesome joint
between this partition and the upper tube plate every time that the top plate or
cover is removed in order to examine and clean the interior of the apparatus is
thus obviated.
When the question of saving fuel is of more importance than extra weight and
first cost the temperature of the feed water may be further raised by providing a
second or supplementary heater in which the heat is derived entirely from the
water of condensation discharged at high pressure before it passes into the main
heater. It will be readily understood that in the case of a triple expansion engine
for example in which the live steam is supplied under a pressure of 170 pounds
per square inch (12 kilos. per square centimetre) and at a temperature of
191 degrees centigrade the pressure and temperature in the heater supplied from
the intermediate chamber of the condenser will not exceed 20 pounds (14 k.) and
126 degrees respectively. The discharges from the small valve chest and from the
steam jackets supplied with steam direct from the boiler also have a temperature
of near 191 degrees and if the expansion is considerable will supply a sufficient
quantity of water to make a substantial difference in the temperature of the feed
water. Nevertheless this arrangement, as already explained, is not recommended
except when economy of fuel is of extreme importance.
The invention has been described in connection with tubes fixed in plates at

page_text: both ends but it is evident that other arrangements such as field tubes may be
employed the water being supplied to the inner tube and being afterwards heated
by contact with the large tube. The speed of flow in this case is greater in
proportion as the sectional area of the annular space between the tubes is con-
tracted and the transference of heat is thus increased. This transference may be
further promoted by forming a helix or screw thread upon the inner circulating
tube and dividing the combination of tubes into several parts or series which are
successively traversed by the water.
The invention is not limited to tubular forms of heating surface but with the
high pressures at which modern engines are worked the employment of flat surfaces
is practically out of the question.
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. Baffles deflectors or arrangements for agitating the water flowing in feed
water heater tubes substantially as hereinbefore described with reference to the
accompanying drawings the agitation of the said water being produced by the
action or movement of the water itself and not by the motion of mechanical parts.
2. A feed water heater tube provided with baffles, deflectors or obstacles
consisting of a twisted and bent plate (Figures 1 and 2) or a series of plates fixed
on a central rod or wire (Figures 3 and 4) for the purpose of agitating the stream
of water flowing in the said tube substantially as bereinbefore described.
3. The combinations and arrangements of parts constituting the improvements
in feed water heaters substantially as hereinbefore described and illustrated in the
accompanying drawings.
Dated this 21st day of April 1892.
J. H. JOHNSON & Co.,
Agents.