U.S. patent application number 10/840952 was filed with the patent office on 2005-06-23 for heat exchanger, combination with heat exchanger and method of manufacturing the heat exchanger.
This patent application is currently assigned to Aalborg Industries A/S. Invention is credited to Jorgensen, Lars S., Nielsen, Mosekaer B.I., Spender-Andersen, Niels.
Application Number | 20050133202 10/840952 |
Document ID | / |
Family ID | 34680188 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133202 |
Kind Code |
A1 |
Jorgensen, Lars S. ; et
al. |
June 23, 2005 |
Heat exchanger, combination with heat exchanger and method of
manufacturing the heat exchanger
Abstract
A heat exchanger for heat exchange between a first and a second
fluid and comprising a cylindrical casing 2, a cylindrical fluid
conduit 5 arranged inside the casing such that an axially extending
tubular space 8 is defined, at least one helical coil 9, 10 of a
finned or corrugated tube being arranged inside the tubular space,
and adjustable throttle means 17, 17a, 18 adapted and arranged for
adjustably throttling flow of the first fluid through the conduit 5
to adjust the flow of the first fluid through the conduit and the
first tubular space for adjusting the heat exchange between the
first fluid and the second fluid flowing through the helical coils
9, 10.
Inventors: |
Jorgensen, Lars S.;
(Gandrup, DK) ; Spender-Andersen, Niels;
(Stovring, DK) ; Nielsen, Mosekaer B.I.; (Aalborg
Ost, DK) |
Correspondence
Address: |
KLEIN, O'NEILL & SINGH
2 PARK PLAZA
SUITE 510
IRVINE
CA
92614
US
|
Assignee: |
Aalborg Industries A/S
Aalborg
DK
|
Family ID: |
34680188 |
Appl. No.: |
10/840952 |
Filed: |
May 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10840952 |
May 7, 2004 |
|
|
|
PCT/DK02/00748 |
Nov 7, 2002 |
|
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Current U.S.
Class: |
165/103 ;
165/156 |
Current CPC
Class: |
F28F 27/02 20130101;
F28F 2250/06 20130101; F28D 21/0007 20130101; F24D 2200/18
20130101; F28D 7/024 20130101; F28F 1/36 20130101 |
Class at
Publication: |
165/103 ;
165/156 |
International
Class: |
F28F 027/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2001 |
DK |
DK PA 2001 01661 |
Claims
1. A heat exchanger for heat exchange between a first fluid and a
second fluid and comprising: a generally cylindrical casing with a
first inlet and a first outlet for allowing said first fluid to
flow through said casing in a generally axial direction, a
generally cylindrical fluid conduit arranged inside said casing
generally coaxial therewith so that an axially extending first
tubular space is defined between said conduit and said casing, said
conduit having a second inlet and a second outlet for allowing said
first fluid to flow through said conduit in a generally axial
direction, and said first tubular space having a third inlet and a
third outlet for allowing said first fluid to flow through said
tubular space in a generally axial direction, at least one helical
coil comprising a tube selected from the group consisting of a
finned tube and a corrugated tube arranged inside said first
tubular space generally coaxial therewith and having a fourth inlet
and a fourth outlet for allowing said second fluid to flow through
said tube.
2. A heat exchanger according to claim 1 further comprising first
adjustable throttle means for adjustably throttling said flow of
said first fluid through said conduit and second adjustable
throttle means for adjustably throttling said flow of said first
fluid through said first tubular space.
3. A heat exchanger according to claim 2, wherein said first
throttle means comprise a first butterfly valve, arranged adjacent
one of said second inlet and said second outlet, and said second
throttle means comprise a second butterfly valve, arranged adjacent
one of said third inlet and said third outlet.
4. A heat exchanger according to claim 2, wherein said first
throttle means comprise a first butterfly valve, arranged adjacent
one of said second inlet and said second outlet, and said second
throttle means comprise a ring having planar dimensions
corresponding to the cross section of said first tubular space and
being arranged for being displaced from a heating position wherein
said flow of first fluid through said tubular space is
substantially unhindered to a bypass position wherein said flow is
substantially obstructed.
5. A heat exchanger according to claim 2, wherein said first and
second throttle means comprise: a fixedly arranged stationary plate
with first and second apertures provided therein arranged such that
said second and third inlets or outlets are obstructed by said
plate such that the flow of first fluid through said conduit and
said first tubular space takes place through said first and second
apertures, respectively, in said stationary plate, and at least one
movable plate with third and fourth apertures provided therein and
arranged so as to be displaceable from a bypass position overlying
said stationary plate, wherein said third apertures coincide with
said first apertures and said fourth apertures do not coincide with
said second apertures, to a heating position overlying said
stationary plate wherein said fourth apertures coincide with said
second apertures and said third apertures do not coincide with said
first apertures.
6. A heat exchanger according to any of the claims 2-5 and further
comprising actuating means for adjusting the throttling effect of
said first and second throttle means.
7. A heat exchanger according to claim 6, wherein said throttling
means and said actuating means are adapted such that substantially
any rate of flow between a maximum and minimum rate of flow of said
first fluid through said second inlet and said third inlet may be
obtained.
8. A heat exchanger according to claim 7, wherein said minimum rate
is substantially equal to zero.
9. A heat exchanger according to claim 1 and comprising at least
two coil arranged concentrically and such that mutually adjacent
coils are radially spaced such that an axially extending second
tubular space is provided between said mutually adjacent coils.
10. A heat exchanger according to claim 1, wherein the outer
surface of said conduit is spaced radially from the coil adjacent
said surface such that an axially extending third tubular space is
provided between said surface and said adjacent coil.
11. A heat exchanger according to claim 9 or 10, wherein the radial
dimensions of said second and third tubular spaces are adapted so
as to achieve a certain pressure loss for a given rate of flow of
said first fluid through said first tubular space.
12. A heat exchanger according to claim 1, wherein the coil has
mutually adjacent individual windings that are mutually axially
spaced such that a helically extending space is provided between
said adjacent windings.
13. A heat exchanger according to claim 1 and comprising three or
more helical coils arranged concentrically, each comprising a
finned tube one of the coils being an innermost coil and another of
the coils being an outermost coil, the interior diameter of the
finned tubes constituting the coils being the same, wherein third
throttling means are provided in the tubes constituting the coils
located radially inwards of the outermost coil for increasing the
pressure loss through the tubes of the remaining coils so as to
compensate for the shorter length of said tubes relative to the
length of the tubes of the outermost coil such that the rate of low
of said second fluid through the tubes of all the coils is
substantially the same for a given uniform pressure in said second
fluid at said fourth inlets.
14. A heat exchanger according to claim 13, wherein said third
throttling means are constituted by a reduction of the cross
sectional area of the flow of said second fluid relative to the
internal cross sectional area of said tubes.
15. A heat exchanger according to claim 14 and further comprising
an inlet header tube and an outlet header tube in fluid
communication with said fourth inlets and fourth outlets,
respectively, of all said tubes through corresponding communication
apertures in said header tubes, said reduction of flow cross
sectional area being constituted by reduced size of said
communication apertures in one of said inlet header tube and said
outlet header tube.
16. A heat exchanger according to claim 1, wherein the helical coil
comprises two or more helically wound finned tubes extending
adjacent one another with the same pitch.
17. A combination of a heat exchanger according to claim 1 and an
exhaust gas generating combustion means selected from the group
consisting of at least one of a natural gas fired turbine, an
internal combustion engine, a furnace, a burner, an incinerator,
the combination comprising interconnection means for
interconnecting an exhaust gas outlet of the combustion means with
said second and third inlets of the heat exchanger such that said
exhaust gas constitutes said first fluid.
18. A combination according to claim 17 and further comprising heat
exchanging means for heat exchange between said second fluid and at
least one of a third fluid and the surroundings of said heat
exchanging means, said heat exchanging means being in fluid
communication with said fourth outlet, measuring means for
measuring the rate of heat exchange of said heat exchanging means,
signal output means for emitting a signal representing the result
of a measurement carried out by said measuring means, and first
control means for controlling the adjustment of said first and
second throttle means and adapted for receiving said signal.
19. A combination according to claim 17 or 18 and further
comprising second control means for controlling the adjustment of
said first throttle means such that the throttling effect thereof
is at a minimum during the start up phase of the combustion
means.
20. A combination of a heat exchanger for heat exchange between a
first fluid and a second fluid and an exhaust gas generating
combustion means, the heat exchanger comprising: a generally
cylindrical casing with a first inlet and a first outlet for
allowing said first fluid to flow through said casing in a
generally axial direction, a generally cylindrical fluid conduit
arranged inside said casing generally coaxial therewith so that a
axially extending first tubular space is defined between said
conduit and said casing, said conduit having a second inlet and a
second outlet for allowing said first fluid to flow through said
conduit in a generally axial direction, and said first tubular
space having a third inlet and a third outlet for allowing said
first fluid to flow through said tubular space in a generally axial
direction, and at least one helical coil comprising a tube selected
from the group consisting of a finned tube and a corrugated tube
arranged inside said first tubular space generally coaxial
therewith and having a fourth inlet and a fourth outlet for
allowing said second fluid to flow through said finned tube, the
combination comprising interconnection means for interconnecting an
exhaust gas outlet of the combustion means with said second and
third inlets of the heat exchanger such that said exhaust gas
constitutes said first fluid.
21. A combination according to claim 20 further comprising first
adjustable throttle means for adjustably throttling said flow of
said first fluid through at least one of said conduit and second
adjustable throttle means for adjustably throttling said flow of
said first fluid through said first tubular space.
22. A combination according to claim 21, wherein said first
throttle means comprise a first butterfly valve, arranged adjacent
one of said second inlet and said second outlet, and said second
throttle means comprise a second butterfly valve, arranged adjacent
one of said third inlet and said third outlet.
23. A combination according to claim 21, wherein said first
throttle means comprise a first butterfly valve, arranged adjacent
said one of second inlet and said second outlet, and said second
throttle means comprise a ring having planar dimensions
corresponding to the cross section of said first tubular space and
being arranged for being displaced from a heating position wherein
said flow of first fluid through said tubular space is
substantially unhindered to a bypass position wherein said flow is
substantially obstructed.
24. A combination according to claim 21, wherein said first and
second throttle means comprise: a fixedly arranged stationary plate
with first and second apertures provided therein arranged such that
either said second and third inlets or said second and third
outlets are obstructed by said plate such that the flow of first
fluid through said conduit and said first tubular space takes place
through said first and second apertures, respectively, in said
stationary plate, and at least one movable plate with third and
fourth apertures provided therein and arranged displaceable from a
bypass position overlying said stationary plate, wherein said third
apertures coincide with said first apertures and said fourth
apertures do not coincide with said second apertures, to a heating
position overlying said stationary plate wherein said fourth
apertures coincide with said second apertures and said third
apertures do not coincide with said first apertures.
25. A combination according to claim 21 and further comprising
actuating means for adjusting the throttling effect of said first
and second throttle means.
26. A combination according to claims 21, wherein said throttling
means and said actuating means are adapted such that substantially
any rate of flow between a maximum and minimum rate of flow of said
first fluid through said second inlet and said third inlet may be
obtained.
27. A combination according to claim 26, wherein said minimum rate
is substantially equal to zero.
28. A combination according to claim 21 and comprising two or more
helical coils arranged concentrically and such that mutually
adjacent coils are radially spaced such that an axially extending
second tubular space is provided between said mutually adjacent
coils.
29. A combination according to claim 21, wherein the outer surface
of said conduit is spaced radially from the coil adjacent said
surface such that an axially extending third tubular space is
provided between said surface and said adjacent coil.
30. A combination according to claim 28, wherein the radial
dimension of said second tubular space is adapted so as to achieve
a certain pressure loss for a given rate of flow of said first
fluid through said first tubular space.
31. A combination according to claim 29, wherein the radial
dimension of said third tubular space is adapted so as to achieve a
certain pressure loss for a given rate of flow of said first fluid
through said first tubular space.
32. A combination according to claim 21, wherein the mutually
adjacent individual windings of a coil are mutually axially spaced
such that a helically extending space is provided between said
adjacent windings.
33. A combination according to claim 21 and comprising three or
more helical coils arranged concentrically, one of said coils being
an outermost coil, each of the coils comprising a finned tube, the
interior diameter of the finned tubes being the same, wherein third
throttling means are provided in the tubes of the coils located
radially inward of the outermost coil for increasing the pressure
loss through the tubes of said radially inward located coils so as
to compensate for the shorter length of said tubes of said radially
inward located coils relative to the length of the tubes of the
outermost coil such that the rate of low of said second fluid
through the tubes of all the coils is substantially the same for a
given uniform pressure in said second fluid at said fourth
inlets.
34. A combination according to claim 33, wherein said third
throttling means are constituted by a reduction of the cross
sectional area of the flow of said second fluid relative to the
internal cross sectional area of said tubes.
35. A combination according to claim 34 and further comprising an
inlet header tube and an outlet header tube in fluid communication
with said fourth inlets and fourth outlets, respectively, of all
said tubes through corresponding communication apertures in said
header tubes, said reduction of flow cross sectional area being
constituted by reduced size of said communication apertures in one
of said inlet header tube and said outlet header tube.
36. A combination according to claim 21, wherein a helical coil
comprises two or more helically wound finned tubes extending
adjacent one another with the same pitch.
37. A combination according to claim 21 and further comprising heat
exchanging means for heat exchange between said second fluid and at
least one of a third fluid and the surroundings of said heat
exchanging means, said heat exchanging means being in fluid
communication with said fourth outlet, measuring means for
measuring the rate of heat exchange of said heat exchanging means,
signal output means for emitting a signal representing the result
of a measurement carried out by said measuring means, and first
control means for controlling the adjustment of said first and
second throttle means and adapted for receiving said signal.
38. A combination according to claim 21 and further comprising
second control means for controlling the adjustment of said first
throttle means such that the throttling effect thereof is at a
minimum during the start up phase of said combustion means.
39. A combination according to claim 20, wherein said exhaust gas
generating combustion means is chosen from the group comprising a
natural gas fired turbine, an internal combustion engine, a burner,
a furnace and an incinerator.
40. A method of manufacturing a heat exchanger according to claim 1
and comprising the steps of: providing a first length of tube
selected from the group consisting of a finned tube and a
corrugated tube, providing a body having a substantially circular
cylindrical surface, providing rotating means for causing relative
rotation of said tube and said surface, arranging a lead portion of
said tube abutting against said surface, causing relative rotation
of said surface and said lead portion such that said first length
of tube is helically wound on said surface to form a first helical
coil.
41. A method according to claim 40 and comprising the further steps
of: providing spacing means, attaching said spacing means to said
first helical coil, providing a second length of tube selected from
the group consisting of a finned tube and a corrugated tube,
arranging a lead portion of said second length of tube abutting
against said spacing means, causing relative rotation of first
helical coil and said lead portion of said second length of tube
such that said second length of tube is helically wound on said
spacing means to form a second helical coil radially spaced from
said first helical coil.
42. A method according to claim 40 and comprising the further steps
of: fixating said helical coil relative to said body, and
subjecting said body and said coil to annealing heat treatment.
43. A method according to claim 41 and comprising the further steps
of: fixating said second helical coil relative to at least one of
said body and said first helical coil, and subjecting said body and
said first and second coils to annealing heat treatment.
Description
[0001] The present invention relates to a heat exchanger for heat
exchange between a first fluid and a second fluid and comprising a
generally cylindrical casing with a first inlet and a first outlet
for allowing said first fluid to flow through said casing in a
generally axial direction, and at least one helical coil of a
finned or corrugated tube arranged inside said casing.
[0002] Heat exchangers of this type are known where the first fluid
is forced to flow from inside the coil or coils outwards or vice
versa. The transfer of heat from the first fluid to the second
fluid in the coils is not very well controlled and therefore not as
efficient as possible.
[0003] It is an object of the invention to provide a heat exchanger
of the type in reference where the flow of first fluid, for
instance exhaust gas from a natural gas fired turbine, an internal
combustion engine, an incinerator, a furnace, a burner or the like,
takes place around the finned tube in a well controlled and
efficient manner affording a highly efficient heat transfer from
the first fluid to the second fluid, for instance water.
[0004] According to the invention this object is obtained by
providing a generally cylindrical fluid conduit inside said casing
generally coaxial therewith so that an axially extending first
tubular space is defined between said conduit and said casing, said
conduit having a second inlet and a second outlet for allowing said
first fluid to flow through said conduit in a generally axial
direction, and said first tubular space having a third inlet and a
third outlet for allowing said first fluid to flow through said
first tubular space in a generally axial direction, the at least
one helical coil of a finned or corrugated tube being arranged
inside said first tubular space generally coaxial therewith and
having a fourth inlet and a fourth outlet for allowing said second
fluid to flow through said finned tube.
[0005] Hereby, the first fluid is forced to flow around the finned
tube coil windings in a very efficient manner for heat exchange.
This also reduces the space requirements for the heat exchanger,
the so-called "footprint".
[0006] According to the invention, the heat exchanger further
comprises first adjustable throttle means for adjustably throttling
said flow of said first fluid through said conduit and/or second
adjustable throttle means for adjustably throttling said flow of
said first fluid through said first tubular space.
[0007] Hereby, the flow of first fluid may by-pass the finned tube
coils so that the heat transfer to the second fluid may be reduced
according to the demand for heated second fluid. Furthermore, the
pressure loss from the inlet of the casing to the outlet thereof
may be reduced by by-passing the finned tube coils which is
desirable during start up of for instance a gas fired turbine
generating the first fluid in the form of exhaust gas from the gas
combustion.
[0008] In one of the currently preferred embodiments of the heat
exchanger according to the invention, said first throttle means
comprise a first butterfly valve, preferably arranged adjacent said
second inlet or said second outlet, and said second throttle means
comprise a second butterfly valve, preferably arranged adjacent
said third inlet or said third outlet. Hereby, rather simple
mechanisms that are simple to adjust and regulate are provided.
[0009] In an alternative embodiment, said first throttle means
comprise a first butterfly valve, preferably arranged adjacent said
second inlet or said second outlet, and said second throttle means
comprise a ring having planar dimensions corresponding to the cross
section of said first tubular space and being arranged for being
displaced from a heating position wherein said flow of first fluid
through said tubular space is substantially unhindered to a bypass
position wherein said flow is substantially obstructed. In this
embodiment, the space requirements are reduced.
[0010] In another currently preferred embodiment, said first and
second throttle means comprise a fixedly arranged stationary plate
with first and second apertures provided therein arranged such that
said second and third inlets or outlets are obstructed by said
plate such that the flow of first fluid through said conduit and
said first tubular space takes place through said first and second
apertures, respectively, in said stationary plate, and one or two
movable plates with third and fourth apertures provided therein and
arranged displaceable, preferably rotatably displaceable, from a
bypass position overlying said stationary plate, wherein said third
apertures coincide with said first apertures and said fourth
apertures do not coincide with said second apertures, to a heating
position overlying said stationary plate wherein said fourth
apertures coincide with said second apertures and said third
apertures do not coincide with said first apertures. This
embodiment of the first and second throttle means requires a
minimum of space and is particularly well suited for precise
adjustment of the by-pass flow through the conduit relative to the
heat transfer flow through the tubular space.
[0011] In the currently preferred embodiment, the heat exchanger
according to the invention further comprises preferably motorized
actuating means for adjusting the throttling effect of said first
and second throttle means, and said throttling means and said
actuating means are preferably adapted such that substantially any
rate of flow between a maximum and minimum rate of flow of said
first fluid through said second inlet and said third inlet may be
obtained. Said minimum rate is substantially equal to zero. Hereby,
any distribution of fluid flow between the by-pass conduit and the
tubular space may obtained which allows simple and precise
regulation of the output of the heat exchanger according to the
requirements for heat transfer from the first fluid. By allowing
substantially total by-pass, no heat is transferred to the second
fluid which is advantageous in case no heat transfer is needed to
means exterior of the heat exchanger and therefore no temperature
increase with consequent steam formation will take place in the
finned coil or coils.
[0012] The currently preferred embodiment of a heat exchanger
according to the invention comprises two or more of said helical
coils arranged concentrically and such that mutually adjacent coils
are radially spaced such that an axially extending second tubular
space is provided between said mutually adjacent coils, and the
outer surface of said conduit is spaced radially from the coil
adjacent said surface such that an axially extending third tubular
space is provided between said surface and said adjacent coil, the
radial dimensions of said second and third tubular spaces being
adapted so as to achieve a certain pressure loss for a given rate
of flow of said first fluid through said first tubular space.
[0013] Hereby, the pressure loss from said first inlet to said
first outlet for a given flow of first fluid may be kept at a
minimum while not substantially reducing the efficiency of the heat
exchanger. This is particularly of importance in connection with
gas fired turbines being the origin of said first fluid because gas
turbines are particularly sensitive to the back pressure at the
exhaust outlet thereof.
[0014] Preferably, the mutually adjacent individual windings of a
coil are mutually axially spaced such that a helically extending
space is provided between said adjacent windings. Hereby any
differential thermal expansion or contraction of the casing and/or
conduit relative to the coils in the axial direction will be taken
up by said helically extending space.
[0015] In a currently preferred embodiment of a heat exchanger
according to the invention and comprising three or more of said
helical coils arranged concentrically and the interior diameter of
the finned tubes constituting the coils preferably being the same,
third throttling means are provided in the tubes constituting the
coils located radially inwards of the outermost coil for increasing
the pressure loss through the tubes of said inner coils so as to
compensate for the shorter length of said tubes relative to the
length of the tubes of the outermost coil such that the rate of
flow of said second fluid through the tubes of all the coils is
substantially the same for a given uniform pressure in said second
fluid at said fourth inlets. Hereby, the heat transfer efficiency
of each coil will be substantially the same without having to vary
the diameter of the tubes of each coil to achieve this effect.
[0016] In the currently preferred embodiment of a heat exchanger
according to the invention said third throttling means are
constituted by a reduction of the cross sectional area of the flow
of said second fluid relative to the internal cross sectional area
of said tubes, the heat exchanger preferably further comprising an
inlet header tube and an outlet header tube in fluid communication
with said fourth inlets and fourth outlets, respectively, of all
said tubes through corresponding communication apertures in said
header tubes, said reduction of flow cross sectional area being
constituted by reduced size of said communication apertures in said
inlet header tube and/or in said outlet header tube. This is a
particularly simple and inexpensive way of compensating for the
different lengths of the different coils.
[0017] In case the heat exchanger according to the invention is to
be used for generating steam, then according to the invention each
helical coil may advantageously comprise two or more helically
wound finned tubes extending adjacent one another with the same
pitch. Hereby the number of flow paths is increased which is
advantageous in connection with the large volume expansion of the
water in the coil tubes resulting from the steam generation.
[0018] In another aspect, the present invention relates to a
combination of a heat exchanger according to the invention and an
exhaust gas generating combustion means such as a natural gas fired
turbine, an internal combustion engine based on gasoline, diesel
oil or natural gas, a furnace, a burner, an incinerator and the
like, the combination comprising interconnection means for
interconnecting an exhaust gas outlet of the combustion means with
said second and third inlets of the heat exchanger such that said
exhaust gas constitutes said first fluid.
[0019] The currently preferred embodiment of the combination
according to the invention may further comprise heat exchanging
means for heat exchange between said second fluid and a third fluid
and/or the surroundings of said heat exchanging means, said heat
exchanging means being in fluid communication with said fourth
outlet, measuring means for measuring the rate of heat exchange of
said heat exchanging means, signal output means for emitting a
signal representing the result of a measurement carried out by said
measuring means, and first control means for controlling the
adjustment of said first and second throttle means and adapted for
receiving said signal.
[0020] Preferably, the combination according to the invention
further comprises second control means for controlling the
adjustment of said first throttle means such that the throttling
effect thereof is at a minimum during the start up phase of the
combustion means.
[0021] In yet another aspect, the present invention relates to a
method of manufacturing a heat exchanger according to the invention
and comprising the steps of providing a first length of finned or
corrugated tube, providing a body having a substantially circular
cylindrical surface, providing rotating means for causing relative
rotation of said tube and said surface, arranging a lead portion of
said tube abutting against said surface, and causing relative
rotation of said surface and said lead portion such that said first
length of tube is helically wound on said surface to form a first
helical coil. Hereby, a particularly simple, precise and
inexpensive method of manufacturing a heat exchanger according to
the invention is achieved.
[0022] In connection with heat exchangers according to the
invention having two or more concentric coils, the method according
to the invention preferably comprises the further steps of
providing spacing means, attaching said spacing means to said first
helical coil, providing a second length of finned or corrugated
tube, arranging a lead portion of said second length of finned tube
abutting against said spacing means, causing relative rotation of
first helical coil and said lead portion of said second length of
tube such that said second length of tube is helically wound on
said spacing means to form a second helical coil radially spaced
from said first helical coil.
[0023] So as to avoid inaccuracies in the diameter of the coils and
other disadvantages, the method according to the invention
preferably comprises the further steps of fixating said helical
coil relative to said body, and subjecting said body and said coil
to annealing heat treatment and/or fixating said second helical
coil relative to said body and/or said first helical coil, and
subjecting said body and said first and second coils to annealing
heat treatment. Hereby the diameter alteration of the coils because
of elasticity and stresses in the steel of the coil tubes is
avoided in a simple and cost efficient manner.
[0024] In the following the invention will be explained more in
detail with reference to different embodiments thereof shown,
solely by way of example, in the accompanying drawings where:
[0025] FIG. 1 is an elevational partly sectional diagrammatic view
of a first currently preferred embodiment of a heat exchanger
according to the invention,
[0026] FIGS. 2-3 are schematic plan views illustrating a fin
configuration of the finned tubes according to the invention,
[0027] FIG. 4 is a schematic bottom view of the embodiment of FIG.
1,
[0028] FIG. 5 is an elevational partly sectional diagrammatic view
of a second currently preferred embodiment of a heat exchanger
according to the invention,
[0029] FIG. 6 is a schematic view of an inlet header tube for an
embodiment of the heat exchanger according to the invention
provided with four concentrically arranged finned tube coils,
[0030] FIG. 7 is a broken away elevational view of a third
embodiment of a heat exchanger according to the invention,
[0031] FIG. 8 is a diagrammatic enlarged scale view of a portion of
the embodiment in FIG. 1 illustrating the spacing of the finned
tubes of the coils,
[0032] FIG. 9 is a schematic elevational, broken away, partly
sectional view of the top of the embodiment shown if FIG. 5
illustrating a first embodiment of throttle means according to the
invention,
[0033] FIG. 10 is a schematic elevational, broken away, partly
sectional view of the top of a fourth embodiment of a heat
exchanger according to the invention illustrating a second
embodiment of throttle means according to the invention,
[0034] FIG. 11 is a schematic top view of the embodiment of FIG.
10,
[0035] FIG. 12 is a schematic elevational, cut away view
illustrating a third embodiment of throttle means according to the
invention,
[0036] FIG. 13 is a schematic top view illustrating a fourth
embodiment of throttle means according to the invention,
[0037] FIG. 14 is a schematic, partly sectional, perspectival,
enlarged scale view of the top header tube and fastening means for
the coils of the embodiment of FIG. 1,
[0038] FIG. 15 is a schematic top view illustrating the method
according to the invention of manufacturing the embodiment of FIG.
5, and
[0039] FIG. 16 is a diagram illustrating one embodiment of control
means according to the invention for adjusting the throttle means
according to the invention.
[0040] Referring first to FIGS. 1 and 4, a heat exchanger 1
according to the invention comprises an outer cylindrical casing 2
provided with a flanged inlet 3 and a flanged outlet 4. An interior
cylindrical casing or conduit 5 having an inlet 6 and an outlet 7
is arranged coaxially with the outer casing 2 thereby defining a
tubular space 8 wherein two coils 9 and 10 of finned tubing are
arranged. The finned tubing consists of a tube 11 provided with
fins 12 arranged generally transversely to the axis of the tube
11.
[0041] The finned tube coils 9 and 10 are arranged mutually
concentric and coaxially with the outer and inner casings 2 and 5.
A flanged outlet header tube 13 and a flanged inlet header tube 14
communicate with the interior of the tubes 11 of the coils 9 and 10
through apertures 15 and 16, respectively.
[0042] A butterfly valve 17 (by-pass valve) is pivotably arranged
on a shaft 18 at the outlet 7 of the conduit 5, a position wherein
the valve 17 is in an intermediate position between fully closing
the outlet 7 and fully opening said outlet 7 being shown with
dotted lines at 17a. Semicircular rings 19 and 20 are arranged for
abutting the rim of the butterfly valve 17 in the closed position
thereof thereby ensuring a good closing function of the valve
17.
[0043] The heat exchanger 1 is primarily intended for use in
combination with a natural gas fired turbine for recuperating and
utilizing the heat of the exhaust gases thereof, but may in
principle be used in combination with any means producing a heated
gas such as internal combustion engines, furnaces, burners,
incinerators and the like.
[0044] During maximum output operation of the heat exchanger 1, the
butterfly by-pass valve 17 is in the closed position shown in full
lines in FIG. 1 whereby all the exhaust gas from the gas turbine
introduced into the inlet 3 flows through the tubular space 8 past
the finned tube coils 9 and 10 as indicated by the full line
arrows. Water to be heated is introduced into the coils 9 and 10
through inlet header 14 and is discharged through apertures 15 and
16 and outlet header 4 after having been heated by heat
transmission from the exhaust gas through fins 12 to the tubes 11
and thereby to the water in said tubes.
[0045] The heated water is transported to not shown exterior heat
exchange means for transmitting some of the heat of the water to
some other fluid or to the surroundings, typically radiators in a
building heating system or a district heating system.
[0046] Either during start up of the gas turbine (when the pressure
loss through the heat exchanger 1 should be at a minimum to
facilitate the turbine start up) or when the exterior heat exchange
means do not require the full heating capacity of the heat
exchanger 1, then the butterfly valve 17 is pivoted on shaft 18 so
as to allow some or all the exhaust gas from the gas turbine to
flow through the internal conduit 5 as indicated with dotted arrows
thereby by-passing the tubular space 8 and the coils 9 and 10.
[0047] Hereby, the pressure loss through the heat exchanger 1 is
decreased and the heat transmission to the water in the tubes 9 and
10 is decreased. The butterfly valve 7 can also be described as a
throttling means and may be substituted by other throttling means
as described in the following in connection with FIGS. 9-13.
[0048] Referring now to FIGS. 2 and 3, a strip 12a of carbon steel
is laterally cut to form tabs or fingers 12b that are bent
transverse to the plane of the strip in alternating directions and
thereafter welded onto the surface of the tube 11 in a spiral
configuration by means of welding seam 12c. Hereby a very effective
heat transfers from the hot exhaust gas to the fingers 12b and
thereby to the tube 11 may be achieved. Other configurations with
circular plate shaped fins or corrugations may also be employed
instead of the serrated spirally wound fins shown in FIGS. 2 and
3.
[0049] Referring now to FIG. 14, the tubes 11 are welded to the
upper header tube 14 around the apertures 15 and 16 thereof whereby
the interior of the tubes 11 communicates with the interior of the
header tube 14, The coils 9 and 10 are attached to and suspended
from the outer casing 2 and the inner conduit 5 by means of a beam
22 welded to said casing and conduit. The beam 22 is welded to two
rings 23 and 24 fitting tightly around the fins 12b of the coils 9
and 10. A similar attachment is carried out at the bottom of the
heat exchanger adjacent the inlet header tube 13.
[0050] Referring now to FIG. 8, the position of the coils 9 and 10
relative to one another and relative to the outer casing 2 and the
inner conduit 5 as well as the spacing between the windings of each
coil is illustrated.
[0051] The innermost coil 10 is spaced from the outermost coil 9 by
a tubular space having a thickness or radial dimension t1, while
the innermost coil 10 is spaced from the outer surface of the
conduit 5 by a tubular space having a thickness or radial dimension
t3. The outermost coil 9 is not spaced from the inner surface of
the outer casing 2, i.e. the coil 9 abuts the casing 2.
[0052] The spacings t1 and t3 are chosen such that the loss of
pressure through the tubular space 8 is maintained at a level
acceptable for the optimal operation of the gas turbine (or other
hot exhaust gas generating means) delivering exhaust gas to the
heat exchanger 1. The heat exchange efficiency of the heat
exchanger 1 is not substantially affected by the spacings t1 and
t3. On the other hand, operational tests show that if a spacing
were present between the outer casing 2 and the outermost coil 9,
then the efficiency of the heat exchanger 1 would be considerably
reduced. These two phenomena are at least to a certain degree owing
to, on one hand, turbulent flow between the coils 9 and 10 and
between the conduit 5 and the coil 10 and, on the other hand,
laminar flow in a tubular space between the outer coil 9 and the
casing 2.
[0053] There are several parameters determining the spacings ti and
t3 between the coils and between the innermost coil and the conduit
5. The two most important considerations or parameters are:
[0054] Exhaust Gas Pressure Drop
[0055] The exhaust gas pressure drop or loss is very dependent on
the exhaust gas velocity and the geometry of the heating surface of
the coil windings. The velocity is dependent on the free gas flow
cross sectional area (total area for the gas flow between the tubes
and fins in a cross section).
[0056] .DELTA.p=.xi..multidot.1/2.multidot..rho..multidot.w2,
where
[0057] .DELTA.p: exhaust gas pressure drop [Pa]
[0058] .xi.: pressure drop coefficient, dependent on geometry (fin
shapes, tube diameter, inline/staggered configuration, number of
windings etc),
[0059] .rho.: Density of the gas at mean temperature between inlet
3 and outlet 4 [kg/m.sup.3]
[0060] w: exhaust gas velocity [m/s]
[0061] In most cases, the allowable exhaust gas pressure drop in
heat exchangers and boilers after gas turbines (and engines as
well) is quite limited. For gas turbines it is extremely important
to minimize the exhaust gas pressure drop as the power production
on the turbine (and thus the efficiency of the turbine) is very
dependent on the back pressure. In connection with the heat
exchanger according to the invention the allowable exhaust gas
pressure drop is preferably limited to be below 500 Pa (50 mm water
column), giving very low exhaust gas velocities and thus large
distance between the coils (alternatively more coils giving larger
gas cross section area and larger diameter of the unit).
[0062] Heat Transfer Coefficient
[0063] In general the heat transfer coefficient should be as high
as possible to minimize the heating surface area. The heat transfer
coefficient is increased with higher exhaust gas velocities and
more turbulent flow. For the heating surface chosen (serrated
spiral wound fin tubes) the turbulence of the flow is very good, in
general giving high heat transfer coefficient even for low exhaust
gas velocities.
[0064] Designing the heat exchanger according to the invention with
the spacings t1 and t3 is also advantageous from a production point
of view because it allows the coils to be inserted in the casing
individually as compared with coils designed to abut one another or
to be nested in one another that must be handled and inserted as a
unit comprising several coils.
[0065] Still referring to FIG. 8, a helically extending space is
provided between adjacent windings of each coil 9 and 10, the
thickness or axial dimension of said space being t2. This spacing
t2 of the windings allows the casing 2 and/or the conduit 5 to
thermally expand and contract axially relative to the coils 9 and
10 without causing unacceptable stresses as any differences in such
expansion or contraction is taken up by variations of the spacing
t2 between the windings of the coils.
EXAMPLE
[0066] In the following, the basic technical specifications for a
combination according to the invention of a two coil heat exchanger
according to the invention and a gas fired turbine are listed as a
non-limiting example:
[0067] Dimensions of the Heat Exchanger
1 Height excl. inlet: 1550 mm Diameter excl. insulation: 633 mm
Insulation: 100 mm covered with galvanized steel plate Flue gas
outlet flange: DN 450, DIN 86044 Water inlet/outlet connections:
Carbon steel pipe, OD 60.5 .times. 3.6 mm, 2 "RGW Thickness of
casing (inner 5 and outer 2): 5 mm Weight of heat exchanger excl.
water: 475 kg Weight of heat exchanger incl. water: 500 kg Outside
diameter of tubes 11: 38 mm Tube material thickness: 3.6 mm Fin
type: Serrated spiral wound fins Height of fins: 15 mm Fin density:
250 pcs/m Thickness of fins: 1 mm Material, tube and fins: Carbon
steel Tube configuration: Inline Number of coaxial and concentric
coils: 2 Number of windings: 10 Tube pitch in gas direction: 70 mm
Free spacing t2 between fins on coil windings in gas direction: 2
mm Diameter of by-pass channel (inner casing 5): 323.9 mm Length of
inner casing 5, incl. by-pass valve: 860 mm Centre diameter of
inner coil 10: 401 mm Centre diameter of outer coil 9: 555 mm Free
space t3 between inner casing 5 and fins on inner coil 10: 4.5 mm
Free space t1 between fins on the two coils: 9 mm Free space
between fins on outer coil and inside of outer casing 2: 0 mm Size
of holes 15, 16 in header 13 for coil connection (both coils) 30.8
mm
[0068] Process Data
2 Micro Gas turbine type: HONEYWELL Parallon 75 Max. electric
output power from gas turbine: 75 kW(e) Exhaust gas flow: 0.68 kg/s
Exhaust gas inlet temperature to heat exchanger: 246.degree. C.
Exhaust gas outlet temperature from heat exchanger: 90.degree. C.
Exhaust gas pressure loss across heating surface: 300 Pa Heating
capacity of heat exchanger: 120 kW Water inlet temperature:
50.degree. C. Water outlet temperature: 70.degree. C. Water flow,
approx: 1.44 kg/s Pressure drop, water side: 0.2 bar
[0069] Referring now to FIG. 5, an embodiment of a heat exchanger
31 according to the invention having three concentric coils 32-34
is shown with the same reference numbers being utilized for
elements similar to elements in FIG. 1. The main difference between
the FIG. 1 and FIG. 5 embodiments, apart from the number of coils,
is that inlet apertures 35, 36 and 36 of the outlet header tube 38
are different sizes so as to compensate for the difference in coil
length between the coils 32-34 as explained below.
[0070] As the length of the tubes 11 of the different coils 32-34
are different and all the coils are interconnected at the outlet
header 38 and at the inlet header 39, a flow distribution will be
established in the coils giving the same pressure loss through each
of the coils.
[0071] Thus, the inner coils 33 and 34 [where the second fluid
(typically water) have shorter flow paths than in the outermost
coil 32] can transport more water than the outer coil 32. The water
in the coils 33, 34 and 35 will then not be heated to the same
temperature and will result in a skewed and reduced recuperation of
the heat contained in the first fluid (for instance exhaust gas
from a gas fired turbine).
[0072] It is therefore desirable that the flow rate through the
coils be regulated so that best possible heat recuperation is
obtained with best possible temperature distribution both in the
water and in the exhaust gas. This is achieved by creating an extra
pressure loss in the inner coils 33 and 34 relative to the outer
coil 35 and each other.
[0073] This can be achieved in two manners:
[0074] By providing the tubes of the coils with different
diameters. From a practical point of view this is not desirable
except in case a large number of concentric coils are involved in
which case 2-3 different tube diameters may be acceptable.
[0075] By installing throttle or baffle means in the tubes or at
the inlet or outlet thereof. As can be seen in FIG. 5 and FIG. 6,
this can be achieved by providing the outlet header tube 38 with
apertures 35-37 and 40-43, respectively, having different
diameters. The diameters of the individual apertures are determined
based on the tube diameter and tube length in the individual coils
of a heat exchanger. As an example of diameters for the four
apertures shown in FIG. 6 for an inner diameter of 56 mm of all
four coil tubes, aperture 40 is 56 mm, aperture 41 is 13 mm,
aperture 42 is 11 mm and aperture 43 is 9 mm. Other throttle or
baffle means well known in the art may also be used to achieve the
different pressure loss coefficients for the individual coil
tubes.
[0076] Referring now to FIG. 7, the inner coil adjacent the inner
conduit 5 comprises two parallel wound finned tubes 50 and 51
establishing two parallel flow paths for the second fluid
(typically water) indicated by the arrows R1 and R2.
[0077] This embodiment is intended for use for steam generation
where it is necessary to take into consideration the large volume
expansion of the mass inside the tubes (at the transition from
liquid to vapour, water to steam) with corresponding increase in
flow rate and velocity as well as pressure loss at the inner
surface of the tubes. So as to provide sufficient inner flow cross
sectional area in the tubes it will therefore often be necessary to
use a larger tube diameter, a larger number of coils or provide for
a larger number of flow paths in other ways.
[0078] Apart from providing many coils, more flow paths may be
obtained by having several parallel extending windings in the same
coil as shown in FIG. 7, i.e. several coils with the same coil
diameter and large pitch "screwed" into each other. Hereby it is
obtained that a larger inner cross section area is achieved without
having a large number of coils with a large diameter of the
outermost coil and therefore the outer casing 2 (large footprint).
This smaller footprint or outer diameter of the heat exchanger
entails important advantages both for the end user and during
manufacture, erection and transport. The axial length or height of
the heat exchanger for a given output will of course be larger, but
this does normally not represent a substantial problem during
manufacture or for the end user.
[0079] Referring now to FIGS. 9-13, various embodiments of throttle
means for throttling the flow of first fluid (typically exhaust
gas) through the conduit 5 and the tubular space 8, respectively,
are shown.
[0080] In the embodiment of FIG. 9, the butterfly valve 17
cooperates with a ring 52 that is suspended in three steel wires 53
attached at equidistant points along the ring 52. The wires 53
extend over pulleys 54 to the shaft 18.
[0081] In the situation shown with full lines, the butterfly valve
17 is closed and does not allow any exhaust gas to flow through
conduit 5 while the ring 52 is in its highest position in which it
does not throttle the flow of exhaust gas through the tubular space
8.
[0082] In the situation shown with dotted lines, the butterfly
valve 17a functions as a by-pass valve and allows unthrottled flow
of exhaust gas through the conduit 5 while the ring 52a is in its
full throttle position supported on tightening rings 55 thereby
preventing flow of exhaust gas through the tubular space 8.
[0083] The shaft 18 may be actuated manually, by an electric motor
or a pneumatic or hydraulic mechanism. In the simplest version, the
wires are wound onto and off not shown pulleys arranged on the
shaft 18 such that rotation of the shaft 18 for opening of the
butterfly valve 17 automatically entails lowering of the ring 52
and vice versa.
[0084] When no heat is required by the external heat consumption
means connected to the heat exchanger 31, then the butterfly valve
17 is in its fully open position (17a) and the ring 52 is in its
lowered fully closed position (52a) so that all the exhaust gas is
by-passed through the conduit 5. Hereby, the water in the finned
tube coils is not heated so that external cooling means to avoid
overheating of this water are not necessary.
[0085] A very simple means for regulating the heat output of the
heat exchanger 31 is thus provided. A temperature sensor and
transmitter (not shown) may be provided in the outlet header 38 for
transmitting a signal to the not shown actuator (electric motor)
for the shaft 18 so that if the temperature measured at the outlet
header does not conform to the required temperature, then the shaft
rotates in the corresponding direction to either open or shut the
by-pass valve 17. Many different regulating circuits are
conceivable depending on the requirements of the end user and the
configuration of the external heat consumption devices connected to
the heat exchanger 31.
[0086] Referring now to FIGS. 10 and 11 showing an elevational and
top view, respectively, of a second embodiment of the first and
second throttling means for the flow of exhaust gas through the
internal conduit and the tubular space, respectively, the internal
conduit 5 is connected to a further conduit 56 having an outlet 57
in which a butterfly valve 58 is rotatably mounted on a shaft 59.
The outlet 57 communicates with the outlet 4 of the casing 5. The
butterfly valve 58 may rotate with the shaft 59 from the shown
closed position wherein the outlet 57 is totally obstructed and an
open position wherein flow of exhaust gas through outlet 57 is
unhindered.
[0087] The tubular space 8 communicates with a space 60 defined by
an extension of the outer casing 2, said space communicating with
the outlet 4 through an aperture 61 in a plate 62. A butterfly
valve 63 is mounted in said aperture 61 on the shaft 59 such that
rotation of the shaft 59 rotates the butterfly valve 63 from the
shown fully open position in which flow of exhaust gas from the
tubular space 8 through the space 60 and through the aperture 61 is
unhindered to a fully closed position in which flow of exhaust gas
through the aperture 61 is totally obstructed. The shaft 59 is
connected to an electric motor 64 for being rotated in opposite
directions so as to rotate the valves 58 and 63 between the two
positions described above and to any intermediate position.
[0088] Referring now to FIG. 12, in this embodiment the butterfly
valves 58 and 63 of the embodiment in FIGS. 10 and 11 have been
substituted by a butterfly valve 65 and two butterfly valves 66,
respectively, the operation of the valves 65 and 66 and the shaft
59 being the same as described in connection with the embodiment of
FIGS. 10 and 11.
[0089] Referring now to FIG. 13, a stationary circular plate 70 is
arranged horizontally in an embodiment of the heat exchanger
similar to the one shown in FIG. 1 or FIG. 4 (without the butterfly
valve 17) over the outlet of the conduit 5 and the annular outlet
of the tubular space 8. The plate 70 is provided with apertures 71
communicating with the interior of conduit 5 and apertures 72
communicating with the tubular space 8.
[0090] A rotatably arranged circular plate 73 is arranged on top of
plate 70 on a pivot 74. The plate 73 is provided with apertures 75
identical in shape and distribution to apertures 72 in plate 70 and
with apertures 76 identical in shape and distribution to apertures
71 in plate 70. An electrical motor 77 is arranged for rotating the
rotatable plate 73 in both directions.
[0091] In the position of the rotatable plate shown in FIG. 13 the
apertures 71 and 76 coincide or overly each other so that exhaust
gas can flow practically unhindered through the conduit 5
underlying these coinciding apertures while flow through the
tubular space 8 is obstructed because the apertures 72 and 75 do
not communicate with each other at all. By rotating the plate 73 by
means of the motor 77, a position thereof may be attained where
flow through the tubular space is relatively unhindered because the
apertures 72 and 75 coincide and flow through the conduit 5 is
totally obstructed because the apertures 71 and 76 do not
communicate with each other at all.
[0092] The lower plate 70 may instead be the rotatable one whereby
the pressure from the exhaust gas will press the plate 70 against
the stationary plate 73 and enhance the sealing effect of abutment
of the plates 70 and 73 against each other. Sealing between the
plates may also be achieved in many other ways obvious to those
skilled in the art.
[0093] Referring now to FIG. 15, a method according to the
invention of manufacturing a heat exchanger (the embodiment of FIG.
5) according to the invention is illustrated.
[0094] A cylindrical body 80 is constituted by a steel plate 81
with a thickness of 10 mm, a steel rod 82 inserted between the free
axially extending edges of the plate 81, and not shown
circumferentially extending tightening straps or wires for holding
the plate 81 and rod 82 in the shown cylindrical configuration.
[0095] The inner coil 34 is wound helically around the body or core
80, the leading end (not shown) and the trailing end 11a of the
pipe 11 of the coil 34 being attached to the body by means of
brackets or rods 83 welded to said ends and to the body 80. The
tightening straps mentioned above are located outside the area of
the body 80 to be covered by the coil 34.
[0096] Four cylindrical plates 84 having a quarter circle cross
section and a thickness equal to the required radial dimension t1
(see FIG. 8) are arranged on the outer surface of coil 33 with rods
85 arranged between mutually adjacent axially extending edges of
the plates 84. The plates 84 and rods 85 are held in place by not
shown circumferentially extending tightening straps or wires. The
rods 85 have an oval or elliptical cross section and are placed
between the plates 84 such that the major cross sectional dimension
of the oval or ellipse is tangential to the circular circumference
of the plates 84.
[0097] The next coil 33 is wound helically around the plates 84 and
rods 85 with the leading and trailing ends of the coil 33 being
welded to one of the plates 84 by means of brackets or rods 83 in a
manner very similar to the winding and attachment of the inner coil
34.
[0098] The process is repeated for the next coil 32. If more coils
than three are required, the process described above may be
repeated for any such further coils.
[0099] The unit comprising the body 80, the coils 32-34 and the
plates 84 with rods 85 is thereafter subjected to annealing heat
treatment for avoiding elastic diameter expansion of the coils and
to remove potentially damaging stresses.
[0100] After annealing, the attachments by means of brackets 83 are
removed, the rods 85 are rotated such that the major dimension of
the oval or elliptical cross section is oriented radially whereby
the coils 32-34 are forced to expand slightly such that the
cylindrical plates 84 may be removed. Finally rod 82 is removed
such that the body 80 may be removed. The coils 32-34 are now ready
for being inserted in a casing 2 with a conduit 5 placed inside the
inner coil 34.
[0101] A heat exchanger according to the invention is particularly
well suited for use in a combination or system comprising a gas
fired turbine (or an internal combustion engine utilizing natural
gas as fuel). Such a system is furthermore particularly well suited
for (but not in any way limited to) for use in a system for small
scale combined production of electricity and heat, for instance for
large buildings, hospitals, small district heating systems and the
like.
[0102] Referring now to FIG. 16, a system or combination according
to the invention including a heat exchanger according to the
invention, a gas fired turbine and external heat consuming devices
is shown with the following characteristics:
3 Item Component Description 101 Heat exchanger according to the
invention. 102 Exhaust gas by-pass damper or Can be regulated
manually or as shown valve (butterfly valve for instance) here:
regulated by an actuator (electrical motor), item 11 103 Exhaust
gas stack 104 Gas fired turbine Could be another kind of component
producing exhaust gas 105 Circulation pump A forced circulation
system, to circulate the required water/fluid flow. The pressure
drop on water side in the heat exchanger, valves and piping system
to be taken into account when calculating the delivery head of the
pump. 106 Expansion tank To take the expansion/contraction of the
fluid in the system, when the temperature varies. 107 External end
user Or other heat consumption device. Can be Heat exchanger for
heating use in buildings, in greenhouses, district heating systems
etc. 108 Safety valve To be opened if the pressure in the system
becomes too high 109 Stop valves Normally open. Possible to close
in case of repair. 110 Air venting valve 111 Electrical motor
Electrical motor, automatically controlled by signals from the
temperature transmitter 113. Opens the by-pass valve 102 a little,
if the water temperature becomes too high, closes the valve 102 a
little if the water temperature becomes too low. Set points to be
decided by the end user. 112 Drain valve To drain the water/fluid
from the system 113 Temperature transmitter Sends signal to
electrical motor if temperature measured is too high or too low
[0103] The system can comprise other exhaust gas generating
devices, and the regulation of the heat exchanger's by-pass valve
(and the heat exchanger's throttle valve for throttling fluid flow
through the tubular space containing the finned tube coils) can be
provided for in many different manners depending on the
configuration of the end user's heat consuming devices.
* * * * *