Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 BOILER ~ ~ 5
_ Description
3 The invention concerns a boiler, especially one to be used
4 with a multistage or modulating burner, with a heat-exchanger
space accommodated inside a water jacket, which has an outer
6 wall and an inner wall, and accommodating another water
7 jacket that extends along some of the length of the heat-
8 exchanger space, accordingly leaving an intermediate space
9 and surrounding an interior space.
11 French Patent 2 154 347 describes a boiler with two
12 concentric cylindrical water jackets. The inner space,
13 surrounded by the inner water jacket constitutes the
14 combustion space, whereas the intermediate space between the
water jackets acts as a flue-gas channel. The flue-gas
16 channel accommodates a helical insert. Manufacture is
17 accordingly relatively expensive and service is difficult and
18 time-consuming. A particular drawback is the hazardous cold
19 points that can occur when the burner is being operated at
less than full capacity, precipitating contaminants from the
21 flue gases, which leads in turn to corrosion. This boiler is
22 accordingly not very appropriate for use with a multistage
23 boiler. Furthermore, the known boiler lacks any means of
24 conditioning hot water-- conditioning processing water in
other words.
26
27 It is important for the boiler's output to match that of the
28 burner, and it has always been necessary until now to use
29 boilers of different dimensions, graduated at increments of
approximately 5 kW, in the lower-capacity range.
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1 The object of the present invention is accordin ~ ~ ~i~m~le
and inexpensive boiler with a high thermal efficiency. The
3 boiler should also be appropriate for use with a multistage
4 or modulating burner with no risk of corrosion. Furthermore,
the boiler should not allow much heat to be lost while the
6 burner is not in operation and should be especially
7 appropriate for conditioning hot water.
9 This object is attained in accordance with the present
invention in a boiler of the aforesaid type characterized by
11 a flue-gas outlet from the intermediate space and a flue-
12 gas outlet from the interior space and by means of
13 regulating the flow of flue gas from the outlet from the
14 intermediate space and/or from the outlet from the interior
space. The boiler can be operated at full capacity as long
16 as the means of regulating the flows of flue gas allow the
17 gas to flow out of both the intermediate space and the
18 interior space. The gases can accordingly flow through both
19 the intermediate space between the two water jackets and the
interior space inside the second jacket, losing enough heat
21 to the jacket to exit the boiler as exhaust at a relatively
22 low temperature. When on the other hand the boiler is
23 operated at a lower capacity, 30% of full capacity for
24 example, the outlet from the intermediate space will be
closed and the flue gases can flow only through the interior
26 space. There will be no risk of the gases cooling too
27 rapidly and causing condensation problems in the rear of the
28 boiler. The boiler is accordingly appropriate for use with a
29 two-stage burner. It would, however, also be possible to
employ a modulating boiler that adjusts continuously from
2 ~
1 minimal to full capacity. In this case it is practical to
z motorize the flue-gas valve so that it as well can be
3 operated continuously. This approach makes it possible to
4 control how much flue gas will flow through the intermediate
space. Another advantage of the present invention is that
6 one size of boiler can be employed over a relatively wide
7 range of output. When the boiler is used with a single-stage
8 burner, a single size can be used for a relatively wide
9 range of outputs. Boilers will accordingly need to be
manufactured and inventoried in substantially fewer sizes
11 than up to now. The result is considerably lower
12 manufacturing and warehousing costs. When a boiler is
13 installed with a single-stage burner, it is only necessary to
14 manually adjust the means of regulating the flue-gas flows to
conform to burner output or optimal exhaust-gas temperature.
16
17 It is practical for the means of regulating the flow of flue
18 gas to be a damper. The outlets can open into a single flue
19 and the damper can open the outlet from the interior space
while it closes the outlet from the intermediate space. For
21 maximal burner output, accordingly, the damper can be
22 positioned at midpoint and, for minimal burner output, the
23 outlet from the intermediate space can be closed. When the
24 damper is at midpoint, it will choke the two outlets hardly
at all. When the damper is motorized, however, it is also
26 possible to position it where it can exert a choking action
27 on one of the outlets.
28
29 It is practical for the water jacket around the heat-
exchanger space to be double, with an inner compartment and
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1 an outer compartment separated by a partition. When a
boiler with this embodiment is started, the water in the
3 inner compartment will heat up more rapidly than the water in
4 the outer compartment. When starting cold, accordingly, the
risk of condensation exists for only a very limited time.
6 Furthermore, the relatively cool water that returns for
7 recirculation while the boiler is in operation can
8 accordingly not come into contact with the inner surface of
9 the jacket, whereas the water in the inner compartment will
act as a buffer, preventing the surface from cooling
11 excessively. This is a particular advantage in low-
12 temperature heating systems, where the temperature of the
13 recirculating water is relatively ow. There will
14 accordingly be no risk of undesired condensation that might
result in corrosion. Another important advantage of the
16 embodiment just described is that out-of-operation heat
17 losses will be extensively decreased. The water in the inner
18 compartment will insulate the outer compartment while the
19 burner is not in operation.
21 It has been demonstrated to be especially practical for the
22 distance between the inner wall and the partition of the
23 double jacket to be relatively short, preferably 5 to lS mm.
24 This approach will prevent layers of different temperature in
the water in the inner compartment. The temperature
26 distribution will accordingly be satisfactory. Ebullition
27 noise will also be eliminated. The inner compartment will
28 contain relatively little water. The advantage of this
29 feature is that the water in the inner compartment will heat
up rapidly in operation, eliminating corrosion problems and
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1 allowing the water to be exploited when necessary to fill up
2 a hot-water tank quickly. The tank can accordingly be fairly
3 small and still supply hot water almost as rapidly as a
4 continuous-flow heater.
6 Since the inner compartment contains little water, relatively
7 little heat will be lost as the water cools off while the
8 system is out of operation once the boiler is full. Hot
9 running water will accordingly be provided at a very high
overall efficiency even in summer. This feature is in marked
11 contrast to known boilers, the total efficiency of which is
12 notoriously low enough in summer to make electric heating
13 generally recommended during that season.
14
It is also practical for the distance between the partition
16 and the outer wall of the double jacket to be substantially
17 greater than the distance between the inner wall and the
18 partition. The boiler can accordingly hold enough hot water
19 to heat up a room for example.
21 It is practical for the second water jacket to be
22 approximately half as long as the first water jacket. The
23 result will be a long-diameter combustion chamber at the
24 burner end, which is particularly appropriate for
contemporary gasification burners with powerfully expanding
26 flames. Powerfully expanding flames have a beneficial
27 temperature that results in the creation of very few nitric
28 oxides.
29
The second water jacket is secured to advantage to the rear
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1 wall of the heat-exchanger space. The result is a boiler of
2 simple design with an interior that is readily accessible for
3 cleaning.
It is practical for the space inside the second water jacket
6 to accommodate a core, with an intermediate space between the
7 core and the jacket. This intermediate space channels the
8 flue gases in a way that promotes heat transfer. It is an
9 advantage for the various components of the boiler to be
cylindrical. This approach allows well organized and cost-
11 effective manufacture, especially when the various
12 components are assembled coaxial. The boiler can for example
13 be welded together from sheet steel. The second water jacket
14 and core can also be accommodated in a more or less helical
flue-gas channel. Since such channels constitute a
16 relatively long distance for the gases to travel, heat-
17 exchange will be optimal. The gases will flow over every
18 heat-exchange surface uniformly. There is an additional
19 advantage to this system in that the risk of water condensing
from the gases will be decreased even more. It is of
21 advantage to dimension the gas channels to allow the boiler
22 to operate with its combustion chamber pressurized to
23 approximately 0.5 to 6 mmHg. This approach assumes the use
24 of means of generating pressure, a fan for example. A burner
with a fan operates very quietly. The flue-gas channel can
26 comprise an insert made from coils of sheet metal. Such an
27 embodiment is extremely inexpensive. Another advantage of
28 the embodiment is that an insert made from coils of sheet
29 metal can easily be removed for cleaning.
2 ~ 3 ~
1 It is an advantage for the cross-section of the flue-gas
2 channels to decrease from front to rear. The volume of the
3 gases will decrease as they travel downstream and cool off
4 and they will not occupy as much space. This decrease in
cross-section entails the advantage that the channel can be
6 longer. It is a particular advantage that such a channel
7 will powerfully attenuate noise in that the tapering prevents
8 the establishment of vibrations. The continuous decrease in
9 cross-section can be obtained for example by decreasing the
pitch of the coils of sheet metal from front to rear. Since
11 a coiled strip of sheet metal is relatively unstable, it is
12 practical to connect the coils with spacers. This system
13 makes it possible to maintain a desired distance between each
14 pair of coils.
16 It is of advantage for the core to be hollow. It may also
17 have openings in its surface for example. The hollow in the
18 core has a vibration-attenuating action. The gas inside the
19 core can accommodate the different pressures that occur as a
result of what is called start-up shock when the flame is
21 ignited. The core accordingly functions as a noise -
22 suppressor. Particularly satisfactory noise-suppression
23 properties are obtained when the hollow is loosely packed
24 with mineral fibers, rock wool for example. The same
packing will also extensively prevent undesired heat
26 transfer.
27
28 It is an advantage for the second water jacket to
29 communicate in series with the inner compartment of the
double jacket. This approach will allow hot water to flow
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l out of the inner compartment and into the second water
2 jacket, rapidly increasing the temperature above the
3 condensation-point range and preventing further
4 condensation. It is advantageous to position a pump between
the second water jacket and the inner compartment. This
6 system will ensure satisfactory circulation and hence a
7 satisfactory distribution of temperature. Since the volume
8 of water is relatively small and can accordingly be rapidly
9 recirculated, the heat will be quickly diverted and boiling
noises will be avoided. There can also be a valve for
11 filling a hot-water tank.
12
13 It is practical for the outgoing section and the return
14 section of the circulating heating system to communicate with
lS the outer compartment of the double jacket, in which case it
16 is of advantage for the outgoing section to be at one end of
17 the double jacket and the return section at the other end.
18
19 The invention also concerns a boiler with a heat-exchanger
space accommodated inside a water jacket, which has an outer
21 wall and an inner wall. This boiler is characterized in
22 accordance with the present invention in that the water
23 jacket is a double jacket with an inner and an outer
24 compartment separated by a partition. This boiler is a
simplification of the boiler previously described herein.
26 What is of essence here is that the same components can for
27 the most part be employed for both types of boiler. It turns
28 out in this case to be an advantage for a core to be
29 accommodated in the compartment, leaving an intermediate
space. This design entails the additional advantage of
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l beneficial flue-gas conveyance, whereby a helical flue-gas
2 channel of the type previously described herein can also be
3 employed.
The invention will now be described with reference to the
6 drawing, wherein
8 Figure 1 is a schematic illustration of a boiler
9 employed in a heating plant with a two-stage or
modulating burner and
11
12 Figure 2 is a simplified embodiment of the boiler
13 that is particularly appropriate for a heating
14 plant with a single-stage burner.
16
17 The heating plant in Figure 1 has a boiler 10 heated by a
18 multistage, two-stage for example, or modulating burner 11.
19 A heat-exchanger space 13 is accommodated in a water jacket
15. The water jacket is a double jacket with an inner
21 compartment 17 and an outer compartment 19. The inner
22 compartment is separated from the outer compartment by a
23 partition 21. The distance between an inner wall 23 and
24 partition 21 is relatively short, 10 to 15 mm for example.
For a boiler with an output of 25 kW, the volume of water in
26 the inner compartment will be limited to approximately 5
27 liters. The distance between partition 21 and outer wall 25
28 is substantially longer, depending on the particular
29 application, than that between inner wall 23 and partition
21. Since more contaminants are emitted when the system is
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1 turned on and off, it is important to keep the burner running
2 for fairly long periods. The amount of water in the outer
3 compartment must be determined accordingly. The relatively
4 small volume of water in inner compartment 17 can be rapidly
brought to the operating point. Concentric with the
6 preferably cylindrical double water jacket 15 is another
7 cylinder water jacket 27. Inner compartment 17 communicates
8 in series with second water jacket 27 by way of a line 28,
9 preventing the formation of condensation water and corrosion
problems. Second water jacket 27 is secured to the rear wall
11 29 of heat-exchanger space 13 and extend over only part, half
12 for example, of the length of that space. The front 31 of
13 heat-exchanger space 13 accordingly represents a combustion
14 space with a relatively long diameter, a type that is
especially appropriate for modern gasification burners with a
16 powerfully expanding flame. The space between double water
17 jacket 15 and second water jacket 27 has a flue-gas outlet 33
18 at the rear that can be closed off with a damper 39. The
19 interior 35 of second water jacket 27 also has a flue-gas
outlet 37. Damper 39 is operated by a solenoid or motor 41.
21 No such drive mechanism is necessary if the boiler is used
22 with a single-stage burner, in which event the damper can be
23 manually positioned to optimize the temperature of the
24 exhaust gas. Concentric with second water jacket 27 is a
hollow and cylindrical core 43. The front of the core is
26 closed off by a plate 45 of refractory material. If employed
27 with an atomizing burner, plate 45 will act as an aid to
28 combustion. Any droplets of oil that arrive on the hot
29 surface can evaporate, subsequent to which the resulting gas
will burn practically without emitting any pollutants. The
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1 rear of the core is also closed ofE to advantage by a disk
2 47. Its surface 49 has a number oE openings 51. The cross-
3 section 50 of the core accommodates a packing 52 of rock
4 wool or a similar material. The packing attenuates noise and
extensively prevents any undesired transfer of heat to flue-
6 gas outlet 33. There is a helical flue-gas channel 54 in
7 intermediate space 53 and another helical flue-gas channel 56
8 in intermediate space 55. Channels 54 and 56 consist of a
9 helically coiled strip of sheet metal in the form of an
insert. The pitch of the coils, and accordingly the cross-
11 section of the flue-gas channel, decreases from front to
12 rear. The coils of sheet metal are connected by spacers,
13 (unillustrated) rods for example.
14
Figure 1 illustrates how boiler 10 can be employed in a
16 heating plant. An outgoing section 59 extends from the front
17 of outer compartment 19 to a combining valve 61 and thence by
18 way of a circulating pump 63 to appliances 65. A return
19 section 67 leads from the rear of the boiler to outer
compartment 19. A bypass 70 leads from return section 67 to
21 valve 61.
22
23 An outgoing line 71 leads from second water jacket 27 to the
24 heat-exchanging coil 73 of a hot-water tank 75. The return
line 77 from coil 73 leads by way of a valve 79 and a pump 81
26 to inner compartment 17. A bypass 83 leads from outgoing
27 line 71 to valve 79.
28
29 Reference number 85 labels schematic illustrated controls
that govern the heating plant.
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1 The simplified embodiment of the boiler illustrated in Figure
~ 2 differs from that illustrated in Figure 1 in having no
3 second water jacket or additional flue-gas outlet with a
4 damper. The diameter of core 43 is accordingly longer,
equalling that of the second water jacket 27 in Figure 1.
6 The boiler illustrated in Figure 2 can accordingly be
7 constructed from practically the same components as the
8 boiler illustrated in Figure 1, which has a practical effect
9 on manufacturing costs and on inventory. Since the second
water jacket 27 in Figure 1 is absent, the outgoing line 71
11 in the embodiment illustrated in Figure 2 leads from inner
12 compartment 17 to coil 73. The heating plant is otherwise
13 identical with that in Figure 1 and need not be described
14 again.
16 Various modifications are possible without departing from the
17 concept of the invention. The boiler can for example be of
18 the upright type.
19
Some comments on how the heating plant illustrated in Figure
21 1 works follow.
22
23 The burner operates at full load while the boiler is filling
24 up. Pump 81 pumps relatively cool water into inner
compartment 17, whence the water is distributed fairly
26 rapidly and uniformly throughout the cross-section of the
27 jacket. The preliminary heating is rapid, subsequent to
28 which the water flows into second water jacket 27, where it
29 is further heated and whence it flows back to the coil 73 in
tank 75. The processing water is heated by heat exchange in
1 tank 75. When controls 85 demand the generation of hèat to
2 heat a building interior, pump 81 will be operating even when
3 there is no need to fill tank 75. Since, on the other hand,
4 the water heated in the inner water jacket will flow through
bypass 83, it will arrive without significant heat loss
6 inside inner compartment 17. The heat deriving from inner
7 compartment 17 or heat-exchanger space 13 will then be
8 transmitted directly by way of partition 21 to outer
9 compartment 19, wherein pump 63 generates a circulation that
promotes heat exchange.
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