Improvements in Apparatus for Heating Air for Steam Boiler Furnaces.
Year: 1893

page_text: Date of Application, 13th June, 1893
Complete Specification Left, 12th Mar., 1894-Accepted, 5th May, 1894
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Heating Air for Steam Boiler
Furnaces.
I, JAMES HOWDEN, of 8, Scotland Street, Glasgow, in the County of Lanark,
North Britain, Engineer, do hereby declare the nature of this invention to be as
follows, that is to say :-
My said invention relates to steam boilers the furnaces of which are supplied
with air heated by heat remaining in the fire gases after they have acted on the
heating surfaces of the boiler. In a common type of marine steam boiler the fire
gases pass through horizontal tubes in the boiler to a smoke box or boxes, and
thence, in one form of heating apparatus, through vertical tubes to the uptake,
these vertical tubes being in a casing through which the air passes from fans or
other blowing apparatus on its way to the furnaces. The object of my present
invention is to render the heating action of the fire-gas tubes more efficient, and
to make the passage of the air through the casing easier and more economical in
propelling power.
In order to utilise a substantial amount of the heat of the fire gases the vertical
tubes through which the gases pass should be as long as the space available will
allow. In arrangements of air heating casings heretofore in use, the stream of air,
or each stream when there has been more than one bas traversed the casing from one
side to the other, or from the middle to the sides through a space of considerable
depth depending on the length of the tubes, and such that the air is not uniformly
distributed over the tubes, but passes irregularly to the outlet from the casing. It
is this defective action which I propose to remedy.
In carrying out my invention according to one modification in a case, for example,
in which the air-heating tubes are 40 inches or more in length, I have the air
casing divided by a middle vertical partition into right and left compartments.
At
The delivery pipe of the fan or blower is arranged to deliver the air close to the
middle partition; equally on each side of it, and from the top to the bottom of
it or nearly so. Each compartment is by three horizontal partitions, through
which the tubes pass, divided into four horizontal spaces which may be of equal
or varied depths. The horizontal partitions extend close to the middle vertical
partition so that altogether the entering air is subdivided into eight streams.
the outer ends of the horizontal partitions the four streams of air of each set unite
and pass down to the casing from which the air is distributed through separately
adjustable valves above and below the grates of the furnaces. Each of the sub-
divided streams of air is compelled to pass in contact with the tubes in the space
it passes through, in an effective manner; and as the aggregate cross-sectional
area of the air passages is comparatively large the rate of flow is comparatively
slow, the air thus having more time to take up heat, and requiring less power to
propel it owing to diminished resistance.
In some cases in which the air-heating tubes are comparatively short there may
be in each compartment only two or even only one instead of three horizontal
partitions; and on the other hand there may be more than three horizontal
partitions if found advantageous.
In another modification in which the air-heating casing is divided by a middle
vertical partition, each compartment receives an equal supply of air at its outer
upper corner and each supply is divided by horizontal partitions into two streams
which first proceed towards the middle and then return through lower spaces tc
.

page_text: delivery outlets at the sides. The several spaces may communicate with each other
at the middle, or they may be kept separate by curved partitions.
I prefer to construct the apparatus with the middle vertical partition as herein-
before described but such partition may be dispensed with if wished.
Dated this Twelfth day of June 1893.
EDMUND HUNT,
Applicant's Agent,
Per pro David Ferguson.
Improvements in Apparatus for Heating Air for Steam Boiler
Furnaces.
I, JAMES HOWDEN, of 8, Scotland Street, in the County of the City of Glasgow,
North Britain, 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, that is to say:-
My said invention relates to steam boilers the furnaces of which are. supplied
with air heated by heat.remaining in the fire gases after they; have acted on the
heating surfaces of the boiler. In a common type of marine steam boiler the fire
gases pass through horizontal tubes in the boiler to a smoke box or boxes, and
thence, in one form of heating apparatus, through vertical tubes to the uptake,
these vertical tubes being in a casing through, which the air passes from fans or
other blowing apparatus on its way to the furnaces. . The object of my present
invention is to render the heating action of the fire-gas tubes more efficient, and
to make the passage of the air through the casing easier and more economical in
propelling power.
In order to utilise a substantial amount of the heat of the fire gases the vertical
tubes through which the gases pass should be as long as the space available will
allow. In arrangements, of air heating casings heretofore in use, the stream of air,
or each stream when there has been more than one has traversed, the casing from
one side to the other, or from the middle to the sides through a space of considerable
depth depending on the length of the tubes, and such that the air is not uniformly'
distributed over the tubes but passes irregularly to the outlet from the casing.. It
is this defective action which I propose to remedy.
And in order that my said invention and the manner of performing the same
may be properly understood I hereunto append a sheet of explanatory drawings to be
hereinafter referred to, and showing four modifications of my improved apparatus.
Figures, 1, and, 2, of the drawings are sectional elevations as at right angles to
each other of one modification of my improved apparatus as fitted to an ordinary
marine boiler..
1
•
Figure, 3, is a sectional front elevation of a second modification and
Figures, 4, and, 5, are sectional elevations as at right angles to each other
showing a third and a fourth modification.
U
In these drawings the same reference letters are used to mark the same or-
parts wherever they are repeated.
like
1
In carrying out, my invention according to the modification shown in Figures, 1
and, 2, there, are in a casing, A, placed above the smoke boxes, B, vertical air-
heating tubes, C, 40 inches or more in length through which tubes the waste.gases
pass from the furnaces, D, through the boiler tubes and smoke, boxes to the uptake,
the air for combustion in the furnace being heated by passing in contact with these
tubes, C. The air casing, A, is divided by a 'middle vertical partition, E, into
right and left compartments; and a delivery pipe, F, from a fan or blower (not
shown) is arranged to deliver the air close to the middle partition, E, equally on
I. **

page_text: each side of it, and from the top to the bottom of it or nearly so.
Each compart-
ment of the casing, A, is by three horizontal partitions, G, through which the
tubes, C, pass divided into four horizontal spaces which may be of equal or varied
depths. The horizontal partitions, G, extend close to the middle vertical
partition, E, so that altogether the entering air is subdivided into eight streams.
At the outer ends of the horizontal partitions, G, the four streams of air of each set
unite and pass down through passages, H, at each side of the smoke boxes, B, to a
casing, K, encompassing the furnace fronts, L, from which casing the air is
distributed through separately adjustable valves (not shown) above and below the
grates of the furnaces, D. Each of the subdivided streams of air is compelled to
pass in contact with the tubes, C, in the space it passes through, in an effective
manner and as the aggregate cross-sectional area of the air passages is
comparatively large the rate of flow is comparatively slow, the air thus having
more time to take up heat, and requiring less power to propel it owing to diminished
resistance.
In some cases in which the air heating tubes, C, are comparatively short there
may be in each compartment of the casing, A, only two or even only one instead of
three horizontal partitions, G, and on the other hand there may be more than three
horizontal partitions if found advantageous.
The modification shown in Figure, 3, differs from that shown in Figures, 1,
and, 2, only in having two additional downlet passages, M, through which some of
the air from the two lowest horizontal spaces in the casing, A, can pass down to the
casing, K.
In the modifications shown in Figures, 4, and, 5, the air-heating casing, A, is
divided by a middle vertical partition, E, and each compartment receives an equal
supply of air from a delivery pipe, F, (from a fan or blower not shown) placed at
its outer upper corner. Each supply is divided by horizontal partitions, G, into
two streams which first proceed towards the middle and then return through lower
spaces to downlet passages, H, at the sides. The several spaces in each compart-
ment may communicate with each other at the middle as shown in the left-hand
compartment of Figure, 5; or they may be kept separate by curved partitions, N,
as shown in the right-hand compartment of the same figure.
I prefer to construct the apparatus with the middle vertical partition, E, as
hereinbefore described but such partition may be dispensed with if wished.
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. The combination and arrangement of parts constituting my improved
apparatus for heating air for steam boiler furnaces substantially as hereinbefore
described with reference to Figures, 1, and, 2, or, 3, of the accompanying
drawings.
2. The combination and arrangement of parts constituting my improved
apparatus for heating air for steam boiler furnaces substantially as herein before
described with reference to Figures, 4, and, 5, of the accompanying drawings.
.Dated this Tenth day of March 1894.
EDMUND HUNT,
Applicant's Agent.