U.S. patent application number 12/326551 was filed with the patent office on 2009-06-11 for furnace heat exchanger.
This patent application is currently assigned to BEKAERT COMBUSTION TECHNOLOGY B.V.. Invention is credited to Dirk Ten HOEVE.
Application Number | 20090145419 12/326551 |
Document ID | / |
Family ID | 40720348 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090145419 |
Kind Code |
A1 |
HOEVE; Dirk Ten |
June 11, 2009 |
FURNACE HEAT EXCHANGER
Abstract
The present invention provides an alternative single burner heat
exchanger combination for a gas-fired furnace for hot air
generation to be used to heat spaces in residential and commercial
settings. The fuel fired furnace is compiled of the known set-up of
a plurality of spaced heat exchangers wherein each heat exchanger
has an inlet port for receipt therein of combustion gases. The
single burner is a premix burner providing an excellent combustion
of the gas-air mixture. The burner is in fluid communication with
each port of each heat exchanger through a dilution zone and a
distributor. Preferably, these are all airtight connected to each
other as can be seen in FIG. 2. The combustion gases produced by
the premix burner are mixed with secondary air flows entering the
system in this dilution zone, whereby diluted combustion gases are
obtained. These diluted combustion gases will then enter the heat
exchangers via the distributor. The combustion gases, having a
temperature of about 1600.degree. C. are diluted with the secondary
air flows to a temperature of about 600.degree. C. The premix
burner is surrounded by a shield, which prevents a direct cooling
of the flames on the burner membrane. When flames are cooled by an
air flow, CO levels rise because complete combustion of the
combustible air/gas mixture is prevented. In the system of the
invention a complete combustion of the combustible air/gas mixture
is achieved and the right temperature of gases is delivered to the
heat exchangers, without creation of undesirable combustion
products since cooling of the flames is avoided.
Inventors: |
HOEVE; Dirk Ten; (LD
Ruinerwold, NL) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
BEKAERT COMBUSTION TECHNOLOGY
B.V.
|
Family ID: |
40720348 |
Appl. No.: |
12/326551 |
Filed: |
December 2, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60992545 |
Dec 5, 2007 |
|
|
|
Current U.S.
Class: |
126/116R ;
165/47 |
Current CPC
Class: |
F24H 3/087 20130101 |
Class at
Publication: |
126/116.R ;
165/47 |
International
Class: |
F24H 3/00 20060101
F24H003/00; F24H 9/00 20060101 F24H009/00 |
Claims
1. A single burner heat exchanger combination for a gas-fired
furnace, comprising: at least one or a plurality of spaced apart
heat exchanger elements, each heat exchanger element having an
inlet port for receipt therein of combustion gases, and a premix
burner for producing combustion gases, said burner being in fluid
communication with each port through a dilution zone and a
distributor, said dilution zone being fed by said combustion gases
and a secondary air flow and providing diluted combustion gases,
said distributor feeding said diluted combustion gases to said heat
exchanger elements, said burner being surrounded by a shield.
2. The single burner heat exchanger combination of claim 1, wherein
said burner comprises a self regulating system for proper gas-air
ratio supply to the mixing chamber of the premix burner.
3. The single burner heat exchanger combination of claim 2, wherein
said self regulating system comprises a bi-metal.
4. The single burner heat exchanger combination of claim 1, wherein
said burner is a tubular burner comprising a burner membrane and an
endcap, wherein said burner membrane comprises a perforated sheet
metal, preferably made of refractory steel.
5. The single burner heat exchanger combination of claim 1, wherein
said burner is a tubular burner comprising a burner membrane and an
endcap, wherein said burner membrane comprises a metal fibre burner
membrane.
6. A gas fired furnace comprising a single burner heat exchanger as
defined in claim 1.
7. Use of a single burner heat exchanger combination as defined in
claim 1, in a gas-fired furnace for hot air generation.
8. The single burner heat exchanger combination of claim 2, wherein
said burner is a tubular burner comprising a burner membrane and an
endcap, wherein said burner membrane comprises a perforated sheet
metal, preferably made of refractory steel.
9. The single burner heat exchanger combination of claim 3, wherein
said burner is a tubular burner comprising a burner membrane and an
endcap, wherein said burner membrane comprises a perforated sheet
metal, preferably made of refractory steel.
10. The single burner heat exchanger combination of claim 2,
wherein said burner is a tubular burner comprising a burner
membrane and an endcap, wherein said burner membrane comprises a
metal fibre burner membrane.
11. The single burner heat exchanger combination of claim 3,
wherein said burner is a tubular burner comprising a burner
membrane and an endcap, wherein said burner membrane comprises a
metal fibre burner membrane.
12. A gas fired furnace comprising a single burner heat exchanger
as defined in claim 2.
13. A gas fired furnace comprising a single burner heat exchanger
as defined in claim 3.
14. A gas fired furnace comprising a single burner heat exchanger
as defined in claim 4.
15. A gas fired furnace comprising a single burner heat exchanger
as defined in claim 5.
16. Use of a single burner heat exchanger combination as defined in
claim 2, in a gas-fired furnace for hot air generation.
17. Use of a single burner heat exchanger combination as defined in
claim 3, in a gas-fired furnace for hot air generation.
18. Use of a single burner heat exchanger combination as defined in
claim 4, in a gas-fired furnace for hot air generation.
19. Use of a single burner heat exchanger combination as defined in
claim 5, in a gas-fired furnace for hot air generation.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims benefit of priority to U.S.
Provisional Application Ser. No. 60/992,545, filed Dec. 5, 2007,
the entire contents of which is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates to gas-fired furnaces for hot
air generation to be used to heat spaces in residential and
commercial settings. More in particular, the present invention
relates to a single burner used in combination with multipass heat
exchangers.
BACKGROUND ART
[0003] A typical residential furnace has a bank of heat exchange
panels arranged in parallel relationship such that the circulating
blowing air passes between the panels or heat exchanger elements to
be heated before it passes to the distribution duct. The panels
define an internal flow path for hot combustion gases supplied by
burners. Each of the panels is typically formed of a clamshell
structure which has an inlet end into which the flame of a burner
extends to heat the flue gas, an outlet end which is fluidly
connected to an inducer for drawing the heated flue gas there
through, and a plurality of legs or passes through which the heated
flue gas passes.
[0004] A common arrangement for gas fired furnaces is to provide an
individual burner associated with each heat exchanger, as can be
seen in EP1318362. A fuel gas mixture is delivered through a
manifold. The manifold has a plurality of outlets corresponding
with the number of heat exchangers employed in the furnace.
Interposed between the heat exchangers and the manifold outlets are
a horizontally spaced series of shot-type fuel-air burners provided
in one-to-one correspondence to the number of heat exchangers. The
gas/air mixture is injected by burner into the open end of a heat
exchanger. As a part of the injection process, additional air is
drawn into the heat exchanger so that the gas may be fully
combusted within the heat exchanger. The hot combustion gases are
caused to flow in a tortuous path within each heat exchanger, by an
induction draft fan which creates a negative pressure through the
heat exchangers.
[0005] A blower receives cold room air from the area which is to be
heated, forces that air over the heat exchanger, where after the
air is collected and returned to the rooms to be heated.
[0006] Further examples of such heat exchanger arrangements can be
seen in U.S. Pat. No. 4,467,780; U.S. Pat. No. 5,271,376 and U.S.
Pat. No. 7,096,933.
[0007] In similar arrangements as described above, each heat
exchanger has its own burner. Use of multiple burners generally
increases the cost of the furnace unit. Furthermore, as multiple
burners must be individually ignited, a manifold must be used to
bring the gas fuel to the burner. The manifold must employ
specifically configured orifices at the openings to provide the
proper amount of gas to each burner. The manufacture and
maintenance of this manifold device also increases the cost of
manufacture and maintenance of the furnace. Furthermore, the
efficient operation of the furnace depends largely on the proper
burning of each burner. In a multiple burner situation, it is often
difficult to detect improper operation of an individual burner.
Improper operation of any individual burner may result in the
creation of undesirable combustion products and/or reduce the
operating life of the heat exchanger.
[0008] Most of above addressed problems are solved by US
2005/0161036 providing a unitary burner for producing combustion
gases, the burner having a burner face for passing there through a
combustible gas. The inlet port of each heat exchanger is disposed
adjacent to and in fluid communication with the burner face,
whereby combustion gases may flow from the burner into each of the
inlet ports of the heat exchangers. In above described system, a
flame is formed in each heat exchanger or panel. This implicates
that an extra cooling air needs to be drawn into the panel or heat
exchanger as they can only withstand temperatures up-to 800.degree.
C. This extra cooling air also cools the flame, thereby increasing
the levels of undesirable combustion products (e.g. CO) in the flue
gases.
[0009] It would be desirable to have a system wherein an efficient
combustion, without creation of undesirable combustion products, is
guaranteed in a cost effective way.
DISCLOSURE OF INVENTION
[0010] An aspect of the claimed invention provides an alternative
single burner heat exchanger combination for a gas-fired furnace.
The fuel fired furnace is compiled of the known set-up of a
plurality of spaced heat exchangers wherein each heat exchanger has
an inlet port for receipt therein of combustion gases. The single
burner is a premix burner providing an excellent combustion of the
gas-air mixture. The burner is in fluid communication with each
port of each heat exchanger through a dilution zone and a
distributor. Preferably, these are all airtight connected to each
other as can be seen in FIG. 2. The combustion gases produced by
the premix burner are mixed with secondary air flows entering the
system in this dilution zone, whereby diluted combustion gases are
obtained. These diluted combustion gases will then enter the heat
exchangers via the distributor 150. The combustion gases, having a
temperature of about 1600.degree. C. are diluted with the secondary
air flows to a temperature of about 600.degree. C. The premix
burner is surrounded by a shield, which prevents a direct cooling
of the flames on the burner membrane. When flames are cooled by an
air flow, CO levels rise because complete combustion of the
combustible air/gas mixture is prevented. In the system of the
invention a complete combustion of the combustible air/gas mixture
is achieved and the right temperature of gases is delivered to the
heat exchangers, without creation of undesirable combustion
products since cooling of the flames is avoided.
[0011] Another aspect of the claimed invention provides a single
burner heat exchanger combination 1 as described above wherein the
premix burner 130 comprises a self regulating system 210 for proper
gas-air ratio supply to the mixing chamber 136 of the premix burner
130. The burner is self-regulating with regard to the gas-air ratio
needed for a low CO and NOx producing burner. As the induction
draft fan 170 creates a negative pressure, thereby moving a
constant volume through the heat exchangers, the mass of flue gases
going through the system lowers, thereby drawing less heat from the
burner chamber which heats up the burner chamber. Due to this, the
burner chamber is provided with less air, resulting in an improper
combustion, raising CO and NOx levels. This problem is overcome by
the self-regulating system incorporated in the burner. This
self-regulating system causes an extra primary airflow 220 to enter
the mixing chamber of the burner, thereby raising the oxygen
content in the gas air mixture to a preset value of .lamda.
(gas-air ratio) of preferably 1,3. This allows the burner 130 to
burn the gas-air mixture in a proper way, with production of
minimal quantities of noxious gases, through the whole operating
time of the furnace. This property makes the total burner heat
exchanger combination 1 independent from the length of the
induction blower duct or possible leaks in the system.
[0012] Preferably, this self regulating system comprises a
bi-metal, but also alternative thermally responsive switches can be
used.
[0013] Preferably this premix burner is a tubular burner with a
burner membrane at the cylinder surface and an endcap at the end of
the cylinder. The burner membrane comprises preferably a perforated
sheet metal. More preferably the burner membrane comprises a metal
fiber burner membrane as known from e.g. WO97/04152. The use of
such a tubular burner with endcap combined with a bi-metal
containing self regulating system is particularly advantageous, as,
by the system described above, when the induction fan draft pulls a
lower mass through the system, also less heat is drawn from the
combustion chamber, which heats up the burner. As the burner is
made out of metal, and the impermeable endcap, also made out of
metal, the endcap will heat up more than the burner membrane, as
the burner membrane is cooled by the fresh gas-air mixture flowing
through for combustion. The metal endcap will start irradiating
into the burner body and onto the bi-metal which will thereby open
the extra primary air inlet 220, the inlet being more or less
opened depending on the heat radiated onto the bi-metal. In a
preferred embodiment, the bi-metal is configured in such a way that
when the burner is cold, the bi-metal closes of the extra primary
air inlet 220 completely, and when the burner gets warmer, the
bi-metal opens the extra primary air inlet 220 gradually by bending
of the bi-metal. Such a burner is known from utility model DE
29611179, which was used for a tumble dryer, and which is hereby
incorporated by reference.
DEFINITION
[0014] Premix burner is to be understood as a burner which is
provided with a fully premixed air-combustible gas mixture and
therefore equipped with means for obtaining such a fully premixed
air-fuel mixture. As an overstoichiometric mixture (preferably an
gas-air ratio .lamda. or 1,3) of combustible gas and air is present
at the moment of combustion, a blue flame combustion of the
combustible gas is obtained.
BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS
[0015] FIG. 1 is a schematic side view cross-section of an
embodiment of the present invention.
[0016] FIG. 2 is a schematic top view cross-section of the
embodiment of FIG. 1.
[0017] FIG. 3 is a schematic representation of a burner used in a
preferred embodiment.
REFERENCE LIST
[0018] 1 single burner heat exchanger combination [0019] 110 heat
exchanger element [0020] 120 inlet port of heat exchanger element
[0021] 130 premix burner [0022] 132 primary air [0023] 134 fuel gas
[0024] 136 mixing chamber of burner [0025] 138 hot combustion gases
[0026] 140 dilution zone [0027] 142 secondary air [0028] 144
diluted combustion gases [0029] 150 distributor [0030] 160 shield
around burner [0031] 170 induction draft fan [0032] 210 self
regulating system for proper gas-air ratio supply [0033] 220 extra
primary air via self regulating system
MODE(S) FOR CARRYING OUT THE INVENTION
[0034] FIGS. 1 and 2 show schematically a cross-section of an
embodiment of the present invention. FIG. 1 is a view from the
side, FIG. 2 is a top view. In FIG. 1 the arrows show the flow path
of the gases of the combustion system through the heat exchanger
system. The flow of gases is driven by the induction draft fan 170.
FIG. 2 shows the details of the present invention, the drawing
being cut away where the known heat exchanger setup starts. This
embodiment has four spaced apart heat exchangers 110. Each heat
exchanger 110 has an inlet port 120 for receipt therein of
combustion gases. The single burner is a premix burner providing an
excellent combustion of the gas-air mixture. In this exemplary
embodiment the premix burner is a tubular burner with a burner
membrane at the cylinder surface and an endcap at the end of the
cylinder. The burner membrane comprises a perforated metal sheet.
But also a metal fiber membrane can be used. The burner 130 is in
fluid communication with each port 120 of each heat exchanger 110
through a dilution zone 140 and a distributor 150. These are all
airtight connected to each other. The combustion gases 138 produced
by the premix burner 130 are mixed with secondary air flows 142
entering the system in this dilution zone 140, whereby diluted
combustion gases 144 are obtained. These diluted combustion gases
144 will then enter the heat exchangers 110 via the distributor
150. The combustion gases 138, having a temperature of about
1600.degree. C. are diluted with the secondary air flows 142 to a
temperature of about 600.degree. C. The premix burner 130 is
surrounded by a shield 160, which prevents a direct cooling of the
flames on the burner membrane.
[0035] FIG. 3 shows an alternative embodiment of the present
invention. FIG. 3 only shows the details of this embodiment, the
drawing being cut away where this embodiment overlaps the previous
embodiment of FIGS. 1 and 2. The premix burner 130 comprises a self
regulating system 210 for proper gas-air ratio supply to the mixing
chamber 136 of the premix burner. In this exemplary embodiment, the
self-regulating system 210 is a bi-metal which closes of the extra
primary air intake 220 in cold conditions. When the burner heats
up, the bi-metal bends gradually thereby opening the extra primary
air intake 220.
* * * * *