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Патент USA US2119817

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June 7, 1938.
' 2,119,81 7
Filed Sept. 21, 1937
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Patented June 7,- 1938 '
Curt Keller, Zurich, Switzerland; assignor to ~
Aktiengesellschaft fuer Technische Studien,
Zurich, Switzerland, a corporation of Switzer
Application September 21‘, 1937, Serial No. 164,955
In Switzerland October 12, 1936
10 Claims.
other gases, which is heated to high'tempera
This invention relates to a tubular gas heater
for attaining high gas temperatures.
tures by the combustion of a gas, and which is
economical to construct because the structural
One ?eld of use for devices of this character
is as a component of thermal power plants in
air, describes a closed circuit through a heater
This heater has a series of ‘tubes arranged 5
around the central furnace and the flue gas
such as herein‘described, expands with'the de
velopment of external work in at least one tur
bine and is thereafter compressed in at least one
10 turbo-compressor.' In a device of this type, it is
chamber. Each tube is in the form of a sinuous
coil having a plurality of vertical runs connected
by 180° bends. 'Each coil lies in a radial plane
with respect to the furnace chamber, the various '1()_
5 which a gaseous working medium, for example,
necessary to heat the air to quite high tempera
tures, for example, temperatures of the order of
500° C. This relatively high temperature intro
vertical runs being sustained at their upper ends
duces serious practical difficulties. For example,
an outside sustaining frame by means of tie rods.
In such a heater, the tube c'oils, which are to all 15
in a supporting plate of ?re resistant material.
Such supporting plate isfreely suspended from
1;, ii air is to be'heated in its passage through tubes,
by means of ?ue gases ?owing over the exterior
intents and purposes, supported only at their
upper ends by the supporting plate, above men
tioned, arefree to’expand downwardly, with the
result that such expansion of the tubes takes
tural elements or limit such cooling to small‘ .place without the development of stress. -Con-. 20
sequently the supporting plateQBJries si-mplyvthe
amounts, the requirements are very severe.
of the tubes, the use of high heat resistant mate
rial is essential. If efficiency‘ considerations pre
clude the use of arti?cial cooling of the struc
At about 500° C. the permissible loading of
steel and other structural material diminishes
very rapidly, with the result that in conventional
,,5 structures the parts become quite massive, a fact
weight of the tubes.
plate with the ‘outersustaining frame are stressed
in tension only; All of these parts or compo- 25
which further contributes to the stresses which '
' must be sustained. The use of massive construc
tions to sustain the‘banks of tubes, insulating
material, and other components, results in ex
nents require a. comparatively small quantity of
structural material and have'to transmit slight
bending stresses, if‘ any at all. The sustaining
frame, which is outside the range of high tem
perature, and consequently comparatively cool, 30'
30 cessive construction costs, and impairs the eco
carries vall of the inner parts. It need not be
made of expensive material, a fact which is a
nomical performance of the entireinstallation.
A further difficulty encountered in the con
struction oi high temperature gas'heatersilows
source of substantial economy.
From the"'ab'ove
'it results that the use of expensive heat resistant
from the great temperature differences and con
35 sequent differential expansion as between diiler- '
supporting material is reduced to the practicable 35
minimum. . These advantages are attainable in a
ent parts of the device. These are particularly
pronounced at the commencement of the heating
marked degree if the tie rods are suitably united
with the outer sustaining frame and if the shell
plates and insulation which enclose the furnace
period but also occur under normal working con
ditions, as an incident to load ?uctuations. ,
The‘ tie rods which connect the supporting
If the heater is constructed with‘ a central fur- ‘ chamber are not carried by the upper plate.
A preferred embodiment of the invention will
nace chamber the interior of said chamber is at .
now be described in‘connection with'the accom
panying drawing which shows, by way of (ex
ample, a simple embodiment of the invention.
a very high temperature, while the enclosing or
outer parts are less highly heated. The differen
tial expansion which is inherent in such a situa
45 tion gives rise to severe stresses, increasing the,
. load on some parts beyond safe limits.
In a gas heater the conditions are much more
severe than in a steam generator. In media
- capable of forming drops, for example, water, the
‘if 50 heat transmission is much better than in the case
of a gas. In a boiler the water or steam cools
the heated parts and lowers the temperature ac
gas heater, the plane of section being indicated
by the line I—l on Fig. 2.
Fig. 2 is a half plan of the heater shown in
Fig. 1, the left half of the view being broken _50
away on the line 2--2 of Fig. l to indicate the
internal construction in section. :
Fig. '1 is a vertical axial section through :the
Fig. 3 is afragmentary sectional view showing
The present invention meets the above require - a, preferred construction for connecting the tubes
“ ments and provides-a tubular heater for air or‘ to the top plate.
the heat of thefumace the space between
plate II and the beams It is ?lledwith insulat
Fig. 4 is a similar view showing a modi?cation
of this feature.
The gas heater has a central furnace and ?ue
lng material encloses the discharge header and
gas chamber I, in which is ?tted a cylindrical
metal bailie 2 sustained by a cylindrical base 3.
the tie rods hereinbefore described. This in
sulating material extends downward at the mar
gin and laps the upper end of the insulated shell
- The burner 4 is mounted in the lower part of the
chamber l and the products of combustion ?ow
upward within the bafile 2 and then downward
I, 8, further affording protection to the col
outside this baiiie to an oiftake 26. .
plates 6.
The gas to be heated, forexample air, enters
_A cylindrical shell 5 of insulating material en
closes the furnace ‘chamber and encircles and is
spaced from the baiile 2. The insulation 5 may
comprise slag wool, aluminum foil, spun glass or
the like con?ned between inner and outer shell
through the connection ?fwhich leads to the
distributing header II. From this the-gas passes
in parallel through the various tubular coiisl, Y
the. direction of ?ow being indicated by‘ the arrows A. After psssingupward through the ?rst 15
pass voutside the baille 2, it ?ows downward
The cylindrical enclosure made up of the shells
i and the intervening insulation 5 rests upon 1 through the second ,pass and upward through
a supporting plate ‘I which is carried by the base ‘the third pass, to the discharge header Ii, from
which it ?ows to the point of use through the.
ring i of the heater.
Mounted in the furnace chamber are a pm
connection 2!.
The products of. combustion ?ow, as indicated
by the arrows B, that. is, they ?ow upward, radi
ally outward over the baffle 2, and .then down
ward between the bailiel and the enclosing shell
rality of ?at coils radially arranged. Each coil
is made up of a tube 9 with vertical runs pro-v
duced by bending‘ the tubes 180° upon themselves
so 'as to produce spaced parallel runs, as shown.
The 180“ bends or “return bends” are indicated
5, i, to the offtake 2..
From the above construction it follows tha
at It, and in the embodiment illustrated there
the various coils are sustained at their upper‘
ends inthe plate It and are free to expand
are two vertical runs inside and one vertical run
outside the bafile 2. The precise number of runs
and their distribution between the spaces inside
30 and outside the ba?ie are matters of design and
are subject to variation.‘
downward so that they introduce no stresses in
the plate if such as might overload the latter.
The ?exible connection to the header ll avoids '
the development of undue stress in either the
The various coils are connected to the lower
coils or the header.
supply header or main III to which the gas to
While the coils might be mounted 'in- various
ways in the plate It, a preferred and an altema 35
tive' construction are shown in Figs. 3 and 4.
be heated is supplied. The coils are also con
nected to the upper collecting main or header ll
through which the heated .gas is discharged. '
The upper ends ,of each tube 9 are bent 90°
Referring ?rst to Fig. 3 nipples 21 are shown 7
threaded-into the plate It. These nipples after
and enter the collecting header II in a hori
zontal direction, the purpose being to afford a
yielding or ?exible connection. Each tube 8 is
installation are connected with the tubes by
welding, as indicated at 28. ‘It will be observed
that these welds are at the upper ends of the
formed with a reverse bend‘ at its lower end,
the purpose being to a?'ord ?exibility and thus nipples and since the tubes do not make a tight
minimize the development of local stresses be-' fit in "the nipples a limited degree of ?exibility
is a?orded. The‘clearance is so small that it is
tween each coil and the supply header It.
The various coils are sustained at their upper , impossible to show it correctly on the drawing,
ends by means of the supporting plate I! but it should be understood that the tubes make
through which the upper terminal portions of a ratherloose ?t in the nipples 21. The struc
the straight runs of the tubes pass, and inywhich ture has the de?nite advantage that the rela
tively .thin tube is not welded directly to the
they are ?xed, as hereinafter described.
supporting plate It. Such welding would
The plate It comprises" a ?re-resistant struc
cause warping of the plate and would be objec
tionable. The-slight elasticity secured by the
structure shown is-a matter of substantial im
tural element, preferably of chrome-nickel steel,
a material which has su?icient mechanical
strength under the temperature conditions en
countered. The supporting plate " is ?exibly
suspended by means of vertical tie rods it from
an outer sustaining frame.
The alternative construction-shown in Fig. 4
' is similar. In this the supporting plate is indi
This frame comprises two beams Ii arranged
at right angles to each other and extending ra
dially in plan with reference to the circular fur
nace. They are sustained at their outer ends
on columns ll, as shown. Suspended from the
beams I6 is the ring ii to which the tie rods ll
are directly connected. In this way ?exibility is .
secured. The annular collecting header H is
similarly supported by means of tie rods II
which are sustained by a supporting ring II
also attached to the beams II.
The columns II are connectedat their lower
ends by the gussets ii 'to the supporting plate
70 ‘I and are. also braced by stiffening rings 22,
two such rings being shown.
To sustain the plate It againstlateral dis
placement a number of tie rods II connect the
cated, at “a and one of the tubes at la.- The
plate. “a is counter-bored for the insertion of‘a
cylindrical nipple II. This nipple is welded at
its upper end, as indicated at- 32, to the tube to.
If desired itmay also be spot-welded at about
its mid-1mm, as indicated at 3| to the plate .
"a, but this last welding is not necessary. , This
connection, like that‘shown in Fig. 3, ‘has the
advantage of flexibility and the further advan
tage that the new of heat between the tube and
the supporting plate is to some extent impeded.
While I have shown a furnace of cylindrical
form the speci?c form is subject to variation and
is not a feature of the invention.
The radial 10
arrangement of the tubes, while preferred, may
be departed from. Furthermore, the direction of
?ow of the gas through the heater might be re
plate with the columns 2| adjacent the upper‘ _ versed and under certain conditions it might be
"ring". Toprotectthefrsmestructurefrom found desirable .to reverse it.
The important feature of the invention is the
heat exchanging‘ surface, 1. e., the tubes, sus
pended from above and carried by a sustaining
structure which is wholly outside the furnace and '
consequently subject to relatively low tempera
tures. ‘ The, connections of each coil with the two
manifolds are ?exible and the whole structure
has been designed so that expansion and con
- ,3
other manifold being located above said heat
resistant plate and suspended by tie rods from
7. The combination de?ned in claim lin which
the vertical passes are ?exibly connected with
said ?re resistant plate, the connection compris
ing tubular nipples which encircle the tubes, pro
Ject above the plate and are sustained bythe
traction and particularly differential expansion . plate, said nipples being welded to the tubes at
points a‘ substantial distance above the plate
,10 and contraction are permitted to occur with
out the development of major stress. This is at
whereby ?exible connections between'the plate
tributable in part to the fact that the coils are and the tube are afforded.
suspended and in part to the fact that'the sus-v
8. A tubular gas heater for obtaining high gas‘
pension is of a ?exible character.
While I have described one embodiment of the
invention and prefer the one shown, this is in
tended to be illustrative and not limiting. Modi
temperatures, comprising in combination, a can: .
tral furnace and ?ue gas chambenan insulating 15
shell enclosing said chamber, a plurality of tubu
lar coils‘ mounted in the furnace and ?ue cham
?cations within the broad‘ scope of the invention - ber, means for conducting gas to and from said
are contemplated, as pointed out above.
> coils, an external supporting frame arranged out
What is claimed is:
. '
-> 1. A tubular gas heater designed for operation
side said insulating shell, and a heat resistant 20
carrier platesuspended in a freely movable man
at high temperatures, comprising in combination,
.ner from said frame at the upper end of- said
an external supporting frame; an insulating shell
shell, said coils being supported from said carrier
plate and passing slidably therethrough, so. that‘
‘ mounted within said frame; a heat resistant plate
25 suspended from said frame at the upper end of
said‘ shell, said plate being formed with aper-e
they can expand unimpeded downwards. '
9. A tubular'gas heater for obtaining high'gas
tures; a plurality of tubular coils having passes temperatures, comprising in combination, a cen
connected by return bends, said coils passing. tral furnace and ?ue gas chamber, an insulating
through the apertures in said plate near the up
shell enclosing said chamber, a plurality of tubular
80 per extremity of the coils, whereby the coils are coils mounted in the furnace and ?ue chamber, 30
sustained by the plate within said insulating means for conducting gas to and from said co?s,
shell; means for conducting gas to and from said an external’supportingframe arranged outside .
coils; and combustion means within said shell, said insulating shell, and-comprising beams cross
so arranged that the products ‘.of combustion pass ing each other, a heat resistant ‘carrier plate dis
in heat exchange relation with said coils.
posed at the upper end of said furnace and ?ue
2. The combination de?ned in claim 1, in which gas chamber, tie rods pivotally connecting said
carrier plate to the beams of the supporting
' a cylindrical ba?le mounted within said shell, ex
tends between adjacent passes of‘ the ‘coil and
frame, and means affording ?exible connections '
directs the products of combustion in a sinuous
between the carrier plate and upper portions of
path in contact with said coils.
said coils, so arranged that the coilsv are sus
pended and free to expand downward.
10. A tubular heater for, heating gases to high '
.the ?re‘resistant plate is suspended from the.
frame by tie rods ?exibly connected to the frame. ‘ temperatures,v comprising a heat insulating shell
4. The combination de?ned in claim 1 in which enclosing the sides of a furnace chamber; a sup
the ?re resistant plate. is suspended from the porting structure external to and structurally in
frame by tie rods ?exibly connected to the frame, dependent of said shell; ‘a heat resisting plate
. and heat insulating material is interposed between suspended from said supporting structure and,
substantially closing the upper end of said chama
‘said ?re resistant plate and said frame and en
ber; a plurality of heat transfer ‘coils having
1 closes said tie rods. I
3. The combination de?ned in claim 1 in which
5. The combination de?ned in claim 1 in which " upper portions which pass freely through said
the various coils are radially arranged and in plate; means supported by the plate and con
which the means for conducting gas to and from '_nected with portions of the coils above the plate
the coils comprises two manifolds each ?exibly ‘to suspend the vcoils from the plate with their .
major portions in said chamber while permitting
connected to the coils, one manifold being lo
cated at the lower end of said chamber and the limited lateral movement of the coils; heat in
other manifold being located above said heat sulating means above said plate; ?exible inlet and
discharge connections forsaid coils; and combus
resistant plate.
, _
8. The combination de?ned in claim 1 in which ' tion means including means for directing prod
the various coils are radially arranged and in ucts of combustion in an extended path through
which the means for conducting gas to and from said chamber in heat exchanging relation with Q
the coils comprises two manifolds each ?exibly said coils.
connected to the co?s, one manifold being lo
cated at the lower end of said chamber and ‘the I
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