Note: Descriptions are shown in the official language in which they were submitted.
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BOILER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to various boilers including
a steam boiler, a hot water boiler, a heat medium boiler, a waste
heat boiler, and an exhaust gas boiler. In particular, the present
invention relates to a multitubular boiler including a boiler body
and longitudinal fins, the boiler body.having a plurality of
vertical heat transfer tubes arranged to form a cylindrical shape
so as to connect an upper header to a lower header, the longitudinal
fins being provided, in at least a part in a peripheral direction
of the plurality of the vertical heat transfer tubes arranged to
form the cylindrical shape, to gaps between the adjacent vertical
heat transfer tubes.
The subject application claims a benefit of the priority of
JapanesePatent Application No.2007-11222$filed on April 20, 2007,
and contents thereof are herein incorporated.
2. Description of the Related Art
There are known as multitubular boilers ones disclosed in
Japanese Patent Application Laid-open No. Sho 62-155401 (page 3,
line 19 of upper left column to line 14 of lower left column, FIGS.
1 to 3) and Japanese Patent Application Laid-open No. 2004-225944.
The boiler body of the boiler of this type includes the plurality
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of the water tubes between the upper header and the lower header
each formed in an annular shape. The plurality of the water tubes
are arranged in the peripheral direction of the upper header and
the lower header in a form of inner and outer concentric circles.
The plurality of the water tubes constituting the inner water tube
row is called inner water tubes. The plurality of the water tubes
constituting the outer water tube row is called outer water tubes.
The inner water tubes are provided with the inner longitudinal fins
downwardly extending from the upper header. The outer water tubes
are provided with the outer longitudinal fins upwardly extending
from the lower header.
In the boiler including the above-mentioned boiler body, the
inside of the inner water tube row is the combustion chamber, and
the space between the inner water tube row and the outer water tube
row is the combustion gas flow path. At the lower portion of the
inner water tube row, the combustion chamber communicates with the
combustion gas flow path through the gaps between the inner water
tubes formed in the portion where the inner longitudinal fins are
not provided. Further, at the upper portion of the outer water tube
row, the combustion gas flow path communicates with the flue through
gaps between the outer water tubes formed in the portion where the
outer longitudinal fins are not provided.
When a fuel is burned so as to generate. flame from a burner
installed in an upper portion of the boiler body toward the
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combustion chamber, a combustion gas is reversed in a lower portion
of the combustion chamber and flows upwardly through the combustion
gas flow path between the inner water tube row and the outer water
tube row to be discharged as an exhaust gas to the flue from the
upper portion of the boiler body. In the meantime, the combustion
gas undergoes heat exchange with water in each of the water tubes,
thereby allowing the water in each of the water tubes to be heated.
In the conventional boiler body, as clearly described in
Japanese Patent Application Laid-open No. Sho 62-155401, both ends
in the width direction of the inner longitudinal fin are welded
to the outer peripheral surface of the adjacent inner water tubes.
That is, the adjacent inner water tubes are connected to each other
through an intermediation of the inner longitudinal fin.
In the case where the adjacent inner water tubes are connected
to each other through the intermediation of the inner longitudinal
fin as disclosed in Japanese Patent Application Laid-open No. Sho
62-155401, both sides of the longitudinal fin are restricted.
Accordingly, thermal expansion of the inner water tubes or the
longitudinal fins due to combustion in the combustion chamber cannot
be-relieved. In particular, the inner water tubes are subjected
to high thermal stress because combustion gas temperature is high.
In order to relax the thermal stress, in the invention
disclosed in Japanese Patent Application Laid-open No. 2004-225944,
the height positions of the lower ends of the adjacent inner
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longitudinal fins are made different. However, also in this case,
both ends in the width direction of the inner longitudinal fin are
also welded to the outer surfaces of the adjacent inner water tubes.
Accordingly, fundamental solution for relaxing the thermal stress
is not reached. Further, the inner longitudinal fins have
different sizes, so commonality of components cannot be achieved.
Further, in either conventional technologies, both ends in
the width direction of' the inner longitudinal fin are welded to
the outer peripheral surfaces of the adjacent inner water tubes,
so the number of welding processes tends to increase. Moreover,
regarding either of the inner water tube row and the outer water
tube row, in order to weld both ends of the longitudinal fin to
the outer peripheral surfaces of the water tubes, it is necessary
that the inner water tubes and the outer water tubes be first
installed between the upper header and the lower header, and the
longitudinal fins are then welded to the inner water tubes and the
outer water tubes. Accordingly, the longitudinal fins of the inner
water tubes constituting the inner water tube row cannot be welded
from an outer side of a furnace, and the longitudinal fins of the
outer water tubes constituting the outer water tube row cannot be
welded from an inner side of the furnace. As a result, the water
tubes and the longitudinal fins are not firmly integrated to each
other, so there is room for improvement in heat conductivity from
the longitudinal fins to the water tubes and mounting strength.
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SUMMARY OF THE INVENTION
An object of the present invention is to relax thermal stress
acting on water tubes or longitudinal fins and to achieve
commonality of components of inner longitudirial fins, improvement
in assembling workability of a boiler body, improvement in heat
conductivity from longitudinal fins to the water tubes, and
improvement in mounting strength of the longitudinal fins with
respect to the water tubes.
According to a first aspect of the present invention, there
is provided a boiler including: a plurality of heat transfer tubes
arranged to form a cylindrical shape between an upper he.ader and
a lower header to constitute a heat transfer tube row; and a
plurality of longitudinal fins provided to close gaps between the
heat transfer tubes without connecting the adjacent heat transfer
tubes, the plurality of longitudinal fins being provided to a
portion other than one of one end in a vertical direction of the
heat transfer tube row and a part in a peripheral direction thereof..
In the boiler according to the first aspect of the present
invention, the adjacent heat transfer tubes are not connected to
each other by the longitudinal fins, so thermal stress caused in
the heat transfer tubes and the longitudinal fins can be relaxed.
Further, the gaps between the adjacent heat transfer tubes are
closed by the longitudinal fins, so short path of the combustion
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gas can be prevented.
In the boiler according to the first aspect of the present
invention: the heat transfer tube row may include, in order to close
gaps between each of the plurality of heat transfer tubes and the
heat transfer tubes adjacent to both sides thereof, a plurality
of double-fin heat transfer tubes each having the longitudinal fins
on both sides thereof and a plurality of no-fin heat transfer tubes
free from having the longitudinal fin; the plurality of double-fin
heat transfer tubes and the plurality of no-fin heat transfer tubes
may be alternately arranged one by one; and the boiler may further
include a combustion chamber on an inner side of the heat transfer
tube row, which communicates with a combustion gas flow path on
an outer side of the heat transfer tube row through a portion free
from having the longitudinal fin at the one end in the vertical
direction of the heat transfer tube row.
In the boiler according to the first aspect of the present
invention, the heat transfer tube row is formed of alternately
arranging the double-fin heat transfer tubes and the single-fin
heat transfer tubes one by one. Accordingly, commonality of
components can be achieved and assembling workability can be
improved. Further, after the longitudinal f.ins are fixed to the
heat transfer tubes, those may.be arranged between the upper header
and the lower header, so operability at the time of assembly is
improved. Further, the longitudinal fins can be welded to the heat
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transfer tubes in advance not only on an outer side._of a furnace
but also on an inner side of the furnace. Accordingly, mounting
strength of the longitudinal fins with respect to the heat t-ransfer
tubes is improved, and further, owing to firm integration between
the heat transfer tubes and the longitudinal fins, heat conductivity
from the longitudinal fins to the heat transfer tubes can be
improved.
In the boiler according to the first aspect of the present
invention: the heat transfer tube row may include, in order to close
gaps between each of the plurality of heat transfer tubes and the
heat transfer tube adjacent to one side thereof, a plurality of
single-fin heat transfer tubes each having the longitudinal fin
on one side thereof; and the boiler may further include a combustion
chamber on an inner side of the heat transfer tube row, which
communicates with a combustion gas flow path on an outer side of
the heat transfer tube row through a portion free from having the
longitudinal fin at the one end in the vertical direction of the
heat transfer tube row.
In the boiler according to the first aspect of the present
invention, the heat transfer tube row is formed by successively
arranging the single-fin water tubes, so the commonality of the
components can be achieved and the assembling workability can be
improved. Further, after the longitudinal fins are fixed to the
heat transfer tubes, those may be arranged between the upper header
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and the lower header, so operability at the time of assembly is
improved. Further, the longitudinal fins can be welded to the heat
transfer tubes in advance not only on an outer side of a furnace
but also on an inner side of the furnace. Accordingly, mounting
strength of the longitudinal fins with respect to the heat transfer
tubes is improved, and further, owing to firm integration between
the heat transfer tubes and the longitudinal fins, heat conductivity
from the longitudinal fins to the heat transfer tubes can be
improved.
In the boiler according to the first aspect of the present
invention, the plurality of longitudinal fins may have a size
achieving closure of gaps between the adjacent plurality of heat
transfer tubes owing to thermal expansion by one of a combustion
gas and an exhaust gas.
In the boiler according to the first aspect of the present
invention, since the longitudinal fins close the gaps between the
adjacent heat transfer tubes owing to the thermal expansion, the
short path of the combustion gas can be prevented more reliably.
According to a second aspect of the present invention, there
is provided a boiler including: a plurality of heat transfer tubes
arranged adjacent to each other; and a longitudinal fin provided
between the adjacent heat transfer tubes, in which: one end of the
longitudinal fin is fixed to one of the adjacent heat transfer tubes;
and another end of the longitudinal fin abuts on another of the
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adjacent heat transfer tubes owing to thermal expansion by
combustion of a fuel in a combustion chamber.
In the boiler according to the second aspect of the present
invention, since the adjacent heat transfer tubes are not connected
by each of the longitudinal fins, thermal stress caused in the heat
transfer tubes and the longitudinal fins can be relaxed. Further,
in a portion where the longitudinal fin is provided, gaps between
the adjacent heat transfer tubes are reliably closed owing to the
thermal expansion of the longitudinal fin.
In the boiler of the present invention, the thermal stress
acting on the longitudinal fins or the heat transfer tubes can be
relaxed. Further, it is possible to achieve commonality of
components of the inner longitudinal fins, improvement in
assembling workability of the boiler body, improvement in the heat
conductivity from the longitudinal fins to the water tubes, and
improvement in the mounting strength of the longitudinal fins with
respect to the water tubes.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is a schematic vertical sectional view showing a boiler
according,to Embodiment 1 of the present invention;
FIG. 2 is a sectional view taken along the line II-II of FIG.
1;
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FIG. 3 is an enlarged cross sectional view schematically
showing a part of an inner water t.ube row of the boiler shown in
FIG. 1 and showing a cold state of the boiler;
FIG. 4 is an enlarged cross sectional view schematically
showing the part of the inner water tube row of the boiler shown
in FIG. 1 and showing a combustion state of the boiler;
FIG. 5 is an enlarged cross sectional view schematically
showing a part of the inner water tube row of the boiler shown in
FIG. 1 and showing a state where an inner longitudinal fin of a
double-fin water tube is disposed on a straight line connecting
centers of adjacent inner water tubes;
FIG. 6 is an enlarged cross sectional view schematically
showing a part of an outer water tube row of the boiler shown in
FIG. 1;
FIG. 7 is a schematic cross sectional view showing a
modification of the inner water tube row of the boiler shown in
FIG. 1;
FIG. 8 is a schematic cross sectional view showing a boiler
according to Embodiment 2 of the present invention; and
FIG. 9 is a schematic cross sectional view showing a boiler
according to Embodiment 3 of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Next, embodiment modes of the present invention will be
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described.
A boiler according to the present invention is not limited
to a certain type and is, for example, a steam boiler, a hot water
boiler, a heat medium boiler, a waste heat boiler, or an exhaust
gas boiler. In any case, the boiler is a multitubular boiler and
is typically a multitubular small once-through boiler.
Specifically, the boiler includes an upper header, a lower
header, and a boiler body including a plurality of heat transfer
tubes connecting the upper header to the lower header. The upper
header and the lower header are arranged at a vertical distance
in parallel to each other. Each of the upper header and the lower
header forms a hollow annular shape. All the plurality of the heat
transfer tubes are vertically arranged and are disposed between
the upper header and the lower header. That is, upper ends of the
heat transfer tubes are connected to the upper header and lower
ends thereof are connected to the lower header. The heat transfer
tubes are arranged between the upper header and the lower header
in a peripheral direction thereof, thereby constituting a heat
transfer tube row of a cylindrical shape.
The heat transfer tube row is not limited to a single row,
and may be two rows, three rows, or more. For example, the boiler
body includes an inner heat transfer tube row and an outer heat
transfer tube row. In this case, the inner heat transfer tube row
includes a plurality of inner heat transfer tubes arranged to form
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a cylindrical shape between the upper header and the lower header.
Further, the outer heat transfer tube row includes a plurality of
outer heat transfer tubes arranged to form a cylindrical shape
between the upper header and the lower header so as to surround
the inner heat transfer tube row. In the above-mentioned case where
there are provided the plurality of the heat transfer tube rows,
the heat transfer tube rows are arranged in concentric cylindrical
shapes.
The boiler body is normally closed at one end thereof in a
vertical direction and has a burner at the other end thereof in
the vertical direction. With this structure, an inside of the heat
transfer tube row arranged on an innermost side constitutes a
combustion chamber. It is possible to burn a fuel so that flame
is generated from the burner toward the combustion chamber. Note
that, in a case of the waste heat boiler or the exhaust gas boiler,
the boiler body is closed at one end thereof in the vertical
direction and has an opening portion at the other end thereof in
the vertical direction, through which an exhaust gas is introduced
into the boiler. That is, in the case of the waste heat boiler or
the exhaust gas boiler, an exhaust gas is introduced into a space
on an inner side of the heat transfer tube row arranged on the
innermost side. In both cases, an outer peripheral portion of the
boiler body is covered by a boiler body cover.
The boiler body cover is a cylindrical member provided between
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the upper header and the lower header so as to surround the heat
transfer tube rows. An upper end of the boiler body cover and the
upper header are hermetically sealed. A lower end of the boiler
body cover and the lower header are also hermetically sealed. The
boiler body cover is connected to a flue. A combustion gas from
the combustion chamber (exhaust gas in the case of waste heat boiler
or exhaust gas boiler) undergoes heat exchange with a heat carrier
(such as water) flowing through each of the heat transfer tubes,
and is then discharged from the flue as the exhaust gas.
In order to achieve effective heat exchange with a heat
carrier flowing through the heat transfer tubes, the combustion
gas flows through a space between the outer heat transfer tube row
and the inner heat transfer tube row and a space between the outer
heat transfer tube row and the boiler body cover through a
predetermined passage. Alternatively, the combustion gas flows
through one of the space between the outer heat transfer tube row
and the inner heat transfer tube row, and the space between the
heat transfer tube rows and the boiler body cover through the
predetermined passage. In order to define the passage, a part or
an entire portion of the inner heat transfer tube row is provided
with, except at an end in the vertical direction thereof or a part
in the peripheral direction thereof, inner longitudinal fins
provided to close gaps between the adjacent inner heat transfer
tubes. Further, a part or an entire portion of the outer heat
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transfer tube row is provided with, except at an end in the vertical
direction thereof or a part in the peripheral direction thereof,
outer longitudinal fins provided to close gaps between the adjacent
outer heat transfer tubes.
In this case, the longitudinal fins in the part or the entire
portion of each of the heat transfer tube rows are provided without
connecting the adjacent heat transfer tubes. As structures
therefor, the following three embodiment modes can be suggested.
In a first embodiment mode of the present invention, each of
the heat transfer tube rows is formed of a plurality of double-fin
heat transfer tubes and a plurality of no-fin heat transfer tubes
which are alternately arranged one by one. The double-fin heat
transfer tube is a heat transfer tube having longitudinal fins on
both sides thereof so that gaps betw2en each of the heat transfer
tubes and the heat transfer tubes adjacent to both sides thereof
are closed. The no-fin heat transfer tube is a heat transfer tube
which does not have the longitudinal fin. Each of the double-fin
heat transfer tubes is provided such that distal ends of the
longitudinal fins thereof are close to outer peripheral surfaces
of the other adjacent heat transfer tubes. In this embodiment, in
a case where the longitudinal fins are provided ove'r an entire
periphery of the heat transfer tube row, in consideration to a
structure where the plurality of the double-fin heat transfer tubes
and the plurality of the no-fin heat transfer tubes are alternately
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provided, it is preferable that the heat transfer tube row be formed
of an even number of heat transfer tubes. Note that when single-fin
heat transfer tubes described below are used in a part of the heat
transfer tube row, the heat transfer tube row can be formed of an
odd number of heat transfer tubes.
In a second embodiment mode of the present invention, the heat
transfer tube row is formed of aplurality of single-fin heat
transfer tubes. The single-fin heat transfer tubes are heat
transfer tubes each having a longitudinal fin on one side thereof
such that gaps between each of the heat transfer tubes and the heat
transfer tube adjacent to one side thereof are closed. Each of the
single-fin heat transfer tubes is provided such that a distal end
of the longitudinal fin is close to an outer peripheral surface
of another adjacent heat transfer tube.
In a third embodiment of the present invention, the heat
transfer tube row is formed of a plurality of double-fin heat
transfer tubes. In this case, the double-fin heat transfer tubes.
are provided such that distal ends of the longitudinal fins are
close to distal ends of the longitudinal fins of the other adjacent
heat transfer tubes. That is, the adjacent double-fin heat
transfer tubes are arranged such that distal ends of the
longitudinal fins thereof abut each other.
In all the embodiment modes, it is preferable that the
longitudinal fins have such a size that achieves tight closure of
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gaps between the adjacent heat transfer tubes through thermal
expansion thereof owing to heating by the combustion gas.- That is,
each of the gaps formed between the distal end of the longitudinal
fins and the adjacent heat transfer tube main body or the
longitudinal fin thereof is preferably substantially the same as
an amount of elongation involved in temperature rise of the
longitudinal fin at the time of operation of the boiler. As a result,
in the first embodiment mode of the present invention, each of the
longitudinal fins of the double-fin heat transfer tube abuts on
the outer peripheral surface of another adjacent heat transfer tube.
Further, in the second embodiment of the present invention, the
longitudinal fin of the single-fin heat transfer tube abuts on the
outer peripheral surface of another adjacent heat transfer tube.
Further, in the third embodiment of the present invention, each
of the longitudinal fins of the double-fin heat transfer tube abuts
on one of the longitudinal fins of another adjacent double-fin heat
transfer tube.
In a case where the heat transfer tube row of those structures
is applied to the inner heat transfer tube row, the combustion
chamber on the inner side of the heat transfer tube row communicates
with a combustion gas flow path on an outer side of the heat transfer
tube row through a portion free from having the longitudinal fins
at one end in the vertical direction of the heat transfer tube row
or in a part in a peripheral direction thereof.
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The double-fin heat transfer tube and the single-fin heat
transfer tube may be formed by extrusion molding such that the
longitudinal fin(s) and the heat transfer tube main body are
integrated with each other. However, a normal heat transfer tube
with a fin is formed by disposing a square bar constituting the
longitudinal fin to an outer peripheral surface of a circular tube
constituting the heat transfer tube main body in an axial direction
of the circular tube, and welding the square bar to the circular
tube. With the either heat transfer tubes, after the longitudinal
fin(s) is provided to the heat transfer tube main body, the heat
transfer tube can be provided between the upper header and the lower
header. That is, when the heat transfer tubes are installed between
the upper header and the l-ower header, the longitudinal fins can
be welded to the heat transfer tubes in advance not only on an out'er
side of a furnace but also on an inner side of the furnace. As a
result, the mounting strength is improved and the heat conductivity
from the longitudinal fin(s) to the heat transfer tube is also
improved because the longitudinal fin (s) is firmly integrated with
the heat transfer tube.
Meanwhile, the longitudinal fin provided to the double-fin
heat transfer tube or the single-fin heat transfer tube is typically
provided so as to protrude radially outwardly from the heat transfer
tube main body. In this case, when each of the longitudinal fins
is arranged on a straight line connecting centers of the adjacent
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heat transfer tubes, the gaps between the adjacent heat transfer
tubes can be closed at a minimum distance. Note that the
longitudinal fins may be provided while being shifted to the inner
side of the furnace or the outer side of the furnace. Further, the
longitudinal fins may not necessarily protrude in the radius
direction of the heat transfer tube main body.
Embodiment 1
Hereinafter, specific embodiments of the present invention
will be described in detail with reference to the drawings.
FIG. 1 is a schematic vertical sectional view showing a boiler
according to Embodiment 1 of the present invention. FIG. 2 is a
sectional view taken along the line II-II of FIG. 1. A boiler 1
of this embodiment is a multitubular small once-through boiler
including a boiler body 2 of a cylindrical shape. The boiler body
2 includes an upper header 3, a lower header 4, and a plurality
of water tubes (heat transfer tubes) 5 and 6 arranged to form a
cylindrical shape to connect the upper header 3 to the lower header
4.
The upper header 3 and the lower header 4 are arranged at a
vertical distance in parallel to each other. Each of the upper
header 3 and the lower header 4 forms a hollow annular shape.
Further, the upper header 3 and the lower header 4 are arranged
horizontally and coaxially.
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The plurality of the water tubes 5 are vertically arranged.
Upper ends of the water tubes 5 are connected to the upper header
3, and lower ends thereof are connected to the lower header 4. The
water tubes 5 are successively arranged in a peripheral direction
of the upper header 3 and the lower header 4, thereby constituting
a water tube row forming a cylindrical shape. On the other- hand,
the plurality of the water tubes 6 are also vertically arranged,
the upper ends of the water tubes 6 are connected to the upper header
3, and the lower ends of the water tubes 6 are connected to the
lower header 4. The water tubes 6 are successively arranged in the
peripheral direction of the upper header 3 and the lower header
4 on the outer side of the cylindrically arranged water tubes 5,
thereby constituting the water tube row forming the cylindrical
shape. In this embodiment, an inner water tube row 7 including the
plurality of the water tubes 5 and an outer water tube row 8 including
th-e plurality of the water tubes 6 are concentrically arranged.
That is, the outer water tube row 8 is arranged so as to surround
the inner water tube row 7. Note that, in the following, the water
tubes 5 are referred to as inner water tubes and the water tubes
6 are referred to as outer water tubes.
The inner water tube row 7 is provided with, except for a
predetermined region at a lower end thereof, inner longitudinal
fins 9 such that gaps between the adjacent inner water tubes 5 are
closed. That is, the gaps between the adjacent inner water tubes
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are closed by the inner longitudinal fins 9 except for the
predetermined region at the lower end thereof. In a portion of the
inner water tube row 7, where the inner longitudinal fins 9 are
not provided, the gaps between the adjacent inner water tubes 5
remain. The gaps constitute communication portions (hereinafter,
referred to as inner row communication portions) 10 for establishing
communication between spaces on the inner side and the outer side
of the inner water tube row 7.
FIGS. 3 and 4 are enlarged cross sectional views each
schematically showing a part of the inner water tube row 7. FIG.
3 shows a cold state of the boiler 1, and FIG. 4 shows a combustion
state of the boiler 1. As shown in FIG. 3, the inner water tube
row 7 is formed of a plurality of double-fin water tubes 11 and
a plurality of no-fin water tubes 12 which are arranged alternately
one by one. Each of the double-fin water tubes 11 is formed of the
inner water tube 5 of a circular tube shape constituting the water
tube main body and the two inner longitudinal fins 9 provided to
both sides of the inner water tube 5 so as to radially protrude
therefrom. On the other hand, each of the no-fin water tubes 12
is formed of the inner water tube 5 of the circular tube shape
constituting the water tube main body and is not provided with the
inner longitudinal fin 9.
The inner longitudinal fins 9 of the double-fin water tube
11 are provided so as to close the gaps between the double-fin water
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tube 11 and the two no-fin water tubes 12 adjacent to both sides
thereof in the peripheral direction. Typically, the two inner
longitudinal fins 9 of the double-fin water tube 11 are provided
so as to protrude radially outwardly from the inner water tube 5.
In this case, the inner longitudinal fins 9 may be provided so as
to protrude in a diameter direction from both sides of the.inner
water tube 5, or may be provided on straight lines connecting the
centers of the adjacent inner water tubes 5. Alternatively, the
inner longitudinal fins 9 may be provided by being shifted-to an
inner side or an outer side of a furnace.
Each of the inner longitudinal fins 9 includes an elongated
bar having a rectangular section and is arranged such that a
longitudinal direction thereof is parallel to an axis of the inner
water tube S. A proximal end (one end in width direction) of the
inner longitudinal fin 9 is welded (welding portion 13) onto the
inner water tube 5 while being brought into abutment on the outer
peripheral surface of the inner water tube 5. In this case,when
the two inner longitudinal fins 9 are simultaneously welded to both
sides of the inner water tube 5, warpage is less prone to occur
in the inner water tube 5. Further, the proximal end of each of
the inner longitudinal fins 9 is fillet-welded to the inner water
tube 5 on the inner side and the outer side of the furnace over
an entire longitudinal region. As a result, the inner water tube
and the inner longitudinal fins 9 are firmly integrated with each
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other. Accordingly, it is possible to improve mounting strength
of the inner longitudi-nal fins 9 with respect to the inner water
tube 5 and to improve heat conductivity from the inner longitudinal
fins 9 to the inner water tube S.
Each of the double-fin water tubes 11 is arranged such that
the distal ends of the two inner longitudinal fins 9 welded to both
sides are close to the outer peripheral surfaces of the adjacent
no-fin water tubes 12. In this case, as occasion needs, the distal
ends of the inner longitudinal fins 9 may be allowed to moderately
abut on the outer peripheral surfaces of the no-fin water tubes
12 or a part of the distal ends may be allowed to abut thereon.
In this case, a distance between each of the distal ends of the
inner longitudinal fins 9 and the outer peripheral surface of the
no-fin water tube 12 is set to an amount of elongation a involved
in temperature rise of the inner longitudinal fins 9 at the time
of combustion of the boiler 1 (see FIG. 5). For example, FIG. 5
shows a state where the inner longitudinal fin 9 of the double-fin
water tube 11 is arranged on the straight line connecting the centers
of the adjacent inner water tubes S. In FIG. 5, when the gap between
the adjacent inner water tubes 5 is b and a width of the inner
longitudinal fin 9 is L, the gap.b is equal to L+a. The width L
of the inner longitudinal fin 9 is not particularly limited, but
is preferably equal to or less than 10 mm for preventing burning,
and is set to 6 mm, for example. Note that an outer diameter of
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the inner water tube 5 is normally about 50 mm.
In a case of this embodiment, to the inner water tube row 7,
the inner longitudinal fins 9 are provided over the entire periphery
thereof so as to close the gaps between the adjacent inner water
tubes 5. As described above, the inner water tube row 7 includes
the double-fin water tubes 11 and the no-fin water tubes 12
alternately arranged one by one. Accordingly, the inner water tube
row 7 is preferably formed of the even number of inner water tubes
5. Note that, when single-fin water tubes 14 (see FIG. 7) described
below are used in a part thereof, the inner water tube row 7 can
be formed of the odd number of inner water tubes.
As described in this embodiment, when the.double-fin water
tubes 11 and the no-fin water tubes 12 are alternately arranged
one by one, that is, when the adjacent inner water tubes 5 are not
welded to each other, the double-fin water tubes 11 each having
the two inner longitudinal fins 9 welded to both sides of the inner
water tube 5 are manufactured in advance, and the double-fin water
tubes 11 can be installed between the upper header 3 and the lower
header 4. That is, in installing the heat transfer tubes between
the upper header 3 and the lower header 4, the longitudinal fins
can be welded not only to the heat transfer tubes on the outer side
of the furnace but also to the heat transfer tubes on the inner
side of the furnace in advance. As a result, the mounting strength
is improved, and further, the inner longitudinal fins 9 are firmly
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integrated with the inner water tubes 5, thereby making it possible
to improve the heat conductivity from the inner longitudinal fins
9 to the inner water tubes S.
The outer water tube row 8 is provided with, except for a
predetermined region at the upper end thereof, outer longitudinal
fins 15 such that gaps between the adjacent outer water tubes 6
are closed. That is, the gaps between the outer water tubes 6 are
closed by the outer longitudinal fins 15 except for the
predetermined region at the upper end thereof. In a portion of the
outer water tube row 8, where the outer longitudinal fins 15 are
not provided, gaps between the adjacent outer water tubes 6 remain.
The gaps constitute communication portions (hereinafter, referred
to as outer row communication portions) 16 for establishing
communication between spaces on the inner side and the outer side
of the outer water tube row 8.
FIG. 6 is an enlarged cross sectional view schematically
showing a part of the outer water tube row 8. Similarly to the inner
water tube row 7, the outer water tube row 8 of this embodiment
is formed of the plurality of the double-fin water tubes 11 and
the plurality of the no-fin water tubes 12 arranged alternately
one by one. Each of the double-fin water tubes 11 is formed of the
outer water tube=6 of the cylindrical shape constituting the water
tube main body and the two outer longitudinal fins 15 provided to
both sides of the outer water.tube 6 so as to radially protrude
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therefrom. Each of the outer longitudinal fins 15 is welded to the
outer water tube 6 in the same manner as that of the inner water
tube row 7. However, a width of the outer longitudinal fin 15 may
be larger than the width of the inner longitudinal fin 9. On the
other hand, the no-fin water tube 12 is formed of the outer water
tube 6 of the cylindrical shape constituting the water tube main
body and is not provided with the outer longitudinal fin 15.
The outer water tube row 8 may also have a structure in which,
similarly to the inner =water tube row 7, owing to the thermal
expansion by the combustion of the boiler 1, distal ends of the
two outer longitudinal fins 15 of the double-fin water tubes 11
abut on the outer peripheral surfaces of the no-fin water tubes
12 adjacent to both sides thereof, respectively. Note that, in the
case of the outer water tube row 8, in order to seal in a combustion
gas or an exhaust gas by the outer water tube row 8, the distal
end of each of the outer longitudinal fins 15 may be welded in advance
after being abutted on the outer peripheral surface of the no-fin
water tube 12.
In the outer water tube row 8, similarly to the inner water
tube row 7, the double-fin water tubes 11 each having the two outer
longitudinal fins 15 welded to both sides of the outer water tube
6 are manufactured in advance, and the double-fin water tubes 11
can be installed between the upper header 3 and the lower header
4. That is, when the heat transfer tubes are installed between the
CA 02629479 2008-04-18
upper header 3 and the lower header 4, the longitudinal fins can
be welded not only to the heat transfer tubes on the outer side
of the furnace but also to the heat transfer tubes on the inner
side of the furnace. As a result, the mounting strength is improved,
and further the outer longitudinal fins 15 are firmly integrated
with the outer water tubes 6, thereby making it possible to improve
heat conductivity from the outer longitudinal fins 15 to the outer
water tubes 6. As described above, in a case where, in order to
seal in the combustion gas or the exhaust gas by the outer water
tube row 8, the distal end of each of the outer longitudinal fins
15 is welded in advance to the outer peripheral surface of the no-fin
water tube 12, it suffices that welding is performed from the outer
side of the furnace (welding portion 18 is provided).
Meanwhile, according to needs, each of the inner water tubes
may be further provided with an inner lateral fin (not shown)
protruding from the outer peripheral surface thereof. A plurality
of inner lateral fins may be provided to each of the inner water
tubes 5 at vertical intervals. Further, each of the inner lateral
fins normally protrudes in a flange-like shape in a radially outward
direction of each of the inner water tubes 5. Similarly, according
to needs, each of the outer water tubes 6 may be further provided
with an outer lateral fin (not shown) protruding from the outer
peripheral surface thereof. A plurality of outer lateral fins may
be provided to each of the outer water tubes 6 at vertical intervals.
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Further, each of the outer lateral fins normally protrudes in a
flange-like shape in a radially outward direction of each of the
outer water tubes 6. In this case, each of the lateral fins is
inclined at a predetermined angle with respect to a horizontal
direction, thereby making it possible to generate swirl flow of
the combustion gas. Presence/absence of installation of the
lateral fin, an installation region and an installation position
thereof, the number of' lateral fins to be installed, a shape and
a size, and the like are appropriately set.
Further, between the upper header 3 and the lower header 4,
a boiler body cover 17 of a cylindrical shape is provided so as
to surround the outer water tube row 8. An upper end of the boiler
cover 17 and the upper header 3 are hermetically sealed. A lower
end of the boiler cover 17 and the lower header 4 are also
hermetically sealed. To an upper portion of a peripheral wall of
the boiler body cover 17, a flue 19 is connected. Note that the
outer water tube row 8 may also serve as a part of the boiler body
cover 17. In this case, the boiler body cover 17 is provided so
as to connect a portion of the outer water tube row 8 having the
outer longitudinal fins 15 to the upper header 3.
A lower surface of the upper header 3 is provided with a
fireproof material 20 covering connection portions between the
upper header 3 and the inner water tubes 5 and connection portions
between the upper header 3 and the outer water tubes 6. An upper
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surface of the lower header 4 is also provided with another fireproof
material 20 covering connection portions with respect to the inner
water tubes 5 and connection portions between the lower header.4
and the outer water tubes 6. The fireproof material 20 on the lower
header 4 side is provided so as to also close a central portion
of the lower header 4. A central portion of the fireproof material
20 on the lower header 4 side has a recess of a columnar shape or
a truncated cone shape formed therein.
Meanwhile, in the illustrated example, a lower end of each
of the inner water tubes 5 is formed with a small diameter portion
21 having a diameter smaller than that of the other portion. The
small diameter portions 21 are provided so as to ensure a
predetermined flow rate of the combustion gas passing through the
inner row communication portions 10. Accordingly, in a case where,
even without the small diameter portions 21, the predetermined flow
rate of the combustion gas passing through the inner row
communication portions 10 can be ensured, the small diameter
portions 21 are not necessary. A size of each of the inner row
communication portions 10 depends on the gap between the adjacent
inner water tubes 5 and a position of the lower end of the inner
longitudinal fin 9 in a height direction thereof. Accordingly,
instead of providing the small diameter portions 21, those
dimensions may be adjusted. Note that, in the illustrated example,
the small diameter portion 21 is not formed on the upper end of
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each of the outer water tubes 6. However, similarly to the inner
water tubes 5, the small diameter portions 21 may be formed thereon.
In a central portion of the upper header 3, there is provided
a burner 22 for generating flame downwardly. The burner 22 is
supplied with a fuel and a combustion air. By operating the burner
22, combustion of the fuel is performed in the boiler body 2. In
this case, an inside of the inner water tube row 7 functions as
a combustion chamber 23.
A combustion gas generated by the combustion of the fuel in
the combustion chamber 23 is delivered to a combustion gas flow
path 24 between the inner water tube row 7 and the outer water tube
row 8 through the inner row communication portions 10. The
combustion gas is discharged as an exhaust gas to the outside through
the outer row communication portions 16 and the flue 19 of the boiler
body cover 17. In the meantime, the combustion gas undergoes heat
exchange with water in the inner water tubes 5 and water in the
outer water tubes 6. As a result, the water in the water tubes is
heated. The heated water can be taken out from the upper header
3 in a form of steam. The steam which is taken out is sent to steam
using equipment (not shown) through a water separator (not shown).
or the like.
In this embodiment, the inner water tube row 7 is provided
with the inner longitudinal fins 9 provided to close the gaps between
the adjacent inner water tubes S. The outer water tube row 8 is
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provided with the outer longitudinal fins 15 provided to close the
gaps between the adjacent outer water tubes 6. As a result, while
flow of the combustion gas into the gaps between the inner water
tubes 5 and into the gaps between the outer water tubes 6 is enabled,
thereby preventing the gaps from being dead spaces. Further, by
the inner longitudinal fins 9 and the outer longitudinal fins 15,
heat conduction efficiency from the combustion gas to the inner
water tubes 5 and the outer water tubes 6 can be enhanced. In
addition, after the combustion gas is radially discharged from the
entire periphery of the outer water tube row 8, the exhaust gas
is introduced to the flue 19 through the space between the outer
water tube row 8 and the boiler body cover 17. Accordingly; uniform
flow of the exhaust gas over an entire area in the peripheral
direction of the outer water tube row 8 can be realized.
FIG. 7 is a schematic cross sectional view showing a
modification of the inner water tube row 7. As shown in FIG. 7,
the inner water tube row 7 may be formed of a plurality of single-fin
water tubes 14 which are successively arranged, instead of the
plurality of the double-fin water tubes 11 and the plurality of
the no-fin water tubes 12 which are alternately arranged one by
one. Each of the single-fin water tubes 14 is formed of the inner
water tube 5 of the cylindrical shape constituting the water tube
main body, and the one inner longitudinal fin 9 provided to one
side of the inner water tube 5 so as to protrude in the radius
CA 02629479 2008-04-18
direction thereof. Each of the single-fin water tubes 14 is
arranged such that the distal end of the one inner longitudinal
fin 9 welded on the one side is close to the outer peripheral surface
of the adjacent single-fin water tube 14. Also in this case, at
the time of combustion of the boiler 1, the gaps between the inner
water tubes 5 are completely closed owing to the thermal expansion
of the inner longitudinal fins 9.
The inner water tube row 7 may be formed of the double-fin
water tubes 11 which are successively arranged instead of the
single-fin water tubes 14 which are successively arranged. In this
case, each of the double-fin water tubes 11 is arranged such that
the distal ends of the two inner longitudinal fins 9 welded to both
sides abut on the distal ends of the inner longitudinal fins 9 of
the double-fin water tubes 11 which are adjacent thereto. Also in
this case, at the time of combustion of the boiler 1, the gaps between
the inner water tubes 5 are completely closed owing to the thermal
expansion of the inner longitudinal fins 9.
The modification. as described above can be applied not only
to the inner water tube row 7 but also to the outer water tube row
8 in the same manner. In a case where the outer water tube row 8
also serves as the boiler body cover 17, the distal ends of the
outer longitudinal fins 15 are welded to the other adjacent outer
water tubes 6 or the longitudinal fins 15 thereof in the same manner.
Further, in the case of either modification, after the inner
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longitudinal fins 9 are welded to the inner water tubes 5 or the
outer longitudinal fins 15 are welded to the outer water tubes 6,
those are provided between the upper header 3 and the lower header
4, thereby enhancing assembling workability and enabling improving
the heat conductivity from the longitudinal fins 9 and 15.
Embodiment 2
FIG. 8 is the schematic longitudinal sectional view showing
a boiler according to Embodiment 2 of the present invention. The
boiler according to Embodiment 2 is basically the same as the boiler
1 of the above Embodiment 1. In the following, a description will
be centered on a difference therebetween, and corresponding
portions are denoted by the same reference numerals.
The boiler 1 of the above Embodiment 1, the inner row
communication portions 10 are provided to the lower end of the inner
water tube row 7, and the outer row communication portions 16 are
provided to the upper end of the outer water tube row 8. With this
structure, the combustion gas from the burner 22 on an upper portion
of the boiler body 2 flows through the inner row communication
portions 10 at the lower end of the inner water tube row 7 into
the combustion gas flow path 24 and is discharged to the boiler
body cover 17 from the outer row communication portions 16 at the
upper end of the outer water tube row 8. On the other hand, the
boiler 1 according to Embodiment 2, the inner row communication
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portions 10 are provided to the upper end of the inner water tube
row 7, and the outer row communication portions 16 are provided
to the lower end of the outer water tube row 8. With this structure,
the combustion gas from the burner 22 in the upper portion of the
boiler body 2 flows from the inner row communication portions 10
at the upper end of the inner water tube row 7 into the combustion
gas flow path 24 and is discharged from the outer row communication
portions 16 at the lower end of the outer water tube row 8 to the
boiler body cover 17.
In the case of Embodiment 2, at least the inner water tube
row 7 is formed by alternately arranging the double-fin water tubes
11 and the no-fin water tubes 12 as in the case of the above Embodiment
1, or by successively arranging the single-fin water tubes 14 or
the double-fin water tubes 11. When the boiler 1 is in the cold
state, the distal end of the inner longitudinal fin 9 is close to
the adjacent inner water tube 5. When the boiler 1 is in the
combustion state, the gap between the adjacent inner water tubes
and 5 is closed. Other constructions are the same as those of
the above Embodiment 1, so the description thereof will be omitted.
Embodiment 3
FIG. 9 is the schematic longitudinal sectional view showing
a boiler according to Embodiment 3 of the present invention. The
boiler according to Embodiment 3 is basically the same as the boiler
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1 of the above Embodiment 1. In the following, a description will
be centered on a difference therebetween, and corresponding
portions are denoted by the same reference numerals.
In the above embodiments, the inner row communication portion
is provided to one end in the vertical direction (upper portion
or lower portion) of the inner water tube row 7. In Embodiment 3
of the present invention, the inner row communication portion 10
is provided to a part in the peripheral direction of the inner water
tube row 7. That is, in FIG. 9, in a predetermined region on a left
peripheral side surface, the inner longitudinal fin 9 (and the inner
water tube 5 in some cases) is not provided to the inner water tube
row 7, and the inner longitudinal fins 9 are provided to the
remaining portion over the entire area in the vertical direction
of the gaps between the inner water tubes 5 and 5.
Further, in the above embodiments, the outer row
communication portion 16 is provided to the other end in the vertical
direction (lower portion or upper portion) of the outer water tube
row 8. However, in Embodiment 3, the outer row communication
portion 16 is provided to the other part in the peripheral direction
of the outer water tube row 8. That is, as shown in FIG. 9, in a
predetermined region on a right peripheral side surface, the outer
longitudinal fin 15 (and the outer water tube 6 in some cases) is
not provided to the outer water tube row 8, and the outer
longitudinal fins 15 are provided to the remaining portion over
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the entire area in the vertical direction between the outer water
tubes.
Also in Embodiment 3, a portion where the inner longitudinal
fins 9 are provided is formed by alternately arranging the
double-fin water tubes 11 and the no-fin water tubes 12 one by one
as in the-case of Embodiment 1, or by successively arranging the
single-fin water tubes 14 or the double-fin water tubes 11. When
the boiler 1 is in the cold state, the distal ends of each of the
inner longitudinal fins 9 are close to the inner water tubes 5
adjacent to both sides thereof. When the boiler 1 is in the
combustion state, the gaps with respect to the inner water tubes
adjacent to both sides are closed.
Further, in the case of Embodiment 3, a space between the outer
water tube row 8 and the boiler body cover-l7 on the outer side
of the outer longitudinal fins 15 is closed by the fireproof material
20 and a heat insulation material or one of those. With this
structure, the combustion gas from the combustion chamber 23 passes
through the inner row communication portion 10 at the one end in
the peripheral direction (left side in FIG. 9) and passes through
the combustion gas flow path 24 between the inner water tube row
7 and the outer water tube row 8 to be discharged through the flue
19 at the other end in the peripheral direction (right side in FIG.
9) The flow path of the combustion gas is a laterally-oriented
w shape, so the boiler body is called a w flow boiler body. Other
CA 02629479 2008-04-18
constructions are the same as those of Embodiment 1, so the
description thereof will be omitted.
The boiler 1 of the present invention is not limited to the
above embodiments and can be modified. For example, in the above
embodiments, while the inner water tube row 7 and the outer water
tube row 8 are provided, the number of water tube rows can be
increased or decreased as appropriate. Further, in the above
embodiments, the lower portion of the boiler body 2 is closed and
the burner 22 is provided to the upper portion of the boiler body
2. Conversely, there may be provided a structure in which the upper
portion of the boiler body 2 is closed and the burner 22 is provided
to the lower portion of the boiler body 2.
Further, in the above embodiments, the description is made
of the example in which the boiler of the present invention is
applied to a steam boiler. However, the boiler of the present
invention may be applied to a hot water boiler or a heat medium
boiler. Further, in the embodiments, instead of providing the
burner 22, by providing a structure with which an exhaust gas is
introduced into the inner side of the inner water tube row 7, the
boiler of the present invention may be applied to a waste heat boiler
or an exhaust gas boiler.
Further, in the above embodiments, the double-fin water tube
11 or the single-fin water tube 14 is obtained by welding the
longitudinal fin (inner longitudinal fins 9 or outer longitudinal
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fins 15) to the water tube main body (inner water tube 5 or outer
water tube 6), but the water tube main body and the longitudinal
fin may be integrally formed. For example, by extrusion molding,
the water tube main body and the longitudinal fin may be integrally
formed.
Further, in the above embodiments, the double-fin water tube
11 or the single-fin water tube 14 may be provided with the inner
longitudinal fin 9 (or outer longitudinal fin 15) having a proximal
end and a distal end each formed in advance in a circular arc shape
so as to be fitted with the outer peripheral surface of the inner
water tube 5 (or the outer water tube 6).
Further, in the above embodiments, heights, widths, and
thicknesses of the longitudinal fins 5 and 6 are appropriately
changed, and, as a matter of course, the numbers of water tubes
and 6 constituting the water tube rows 7 and 8, respectively,
can also be appropriately changed.
37
