U.S. patent application number 13/295136 was filed with the patent office on 2012-05-24 for premix air heater.
This patent application is currently assigned to THOMAS & BETTS INTERNATIONAL, INC.. Invention is credited to Chris Grammens, Niko Raes.
Application Number | 20120125311 13/295136 |
Document ID | / |
Family ID | 45023695 |
Filed Date | 2012-05-24 |
United States Patent
Application |
20120125311 |
Kind Code |
A1 |
Grammens; Chris ; et
al. |
May 24, 2012 |
PREMIX AIR HEATER
Abstract
A gas-fired heater includes a gas supply line, an air supply
line, a valve coupled to the gas supply line and a controller
coupled to the valve. The controller is configured to control the
valve to control a gas-air mixture. The gas-fired heater also
includes a burner configured to receive the gas-air mixture and
burn the gas-air mixture, and a heat exchanger coupled to the
burner. The heat exchanger is configured to perform a heat exchange
process and output heated air. The gas-fired heater further
includes a combustion fan located downstream of the heat exchanger,
the combustion fan being configured to pull or draw flue gases
through the heat exchanger.
Inventors: |
Grammens; Chris; (Oedelem,
BE) ; Raes; Niko; (Zwijnaarde, BE) |
Assignee: |
THOMAS & BETTS INTERNATIONAL,
INC.
Wilmington
DE
|
Family ID: |
45023695 |
Appl. No.: |
13/295136 |
Filed: |
November 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61414997 |
Nov 18, 2010 |
|
|
|
Current U.S.
Class: |
126/116R |
Current CPC
Class: |
Y02B 30/102 20130101;
F24H 3/105 20130101; F24H 8/00 20130101; F23N 3/082 20130101; F23N
5/184 20130101; F23N 2233/10 20200101; Y02B 30/00 20130101; F28D
21/0008 20130101; F23N 2005/182 20130101; F23N 1/022 20130101; F23N
2233/04 20200101; F23N 2900/05181 20130101; F24H 3/087
20130101 |
Class at
Publication: |
126/116.R |
International
Class: |
F24H 3/02 20060101
F24H003/02 |
Claims
1. A gas-fired heater, comprising: a gas supply line; an air supply
line; a valve coupled to the gas supply line; a controller coupled
to the valve, the controller configured to control the valve to
control a gas-air mixture; a burner configured to receive the
gas-air mixture and burn the gas-air mixture; a heat exchanger
coupled to the burner, the heat exchanger configured to perform a
heat exchange process and output heated air; and a fan located
downstream of the heat exchanger, the fan being configured to draw
flue gases through the heat exchanger and provide negative pressure
to draw the gas-air mixture through the burner and the
valve-venturi system.
2. The gas-fired heater of claim 1, further comprising: an
enclosure to house the burner and heat exchanger, wherein the
enclosure includes no secondary air inlets such that no air other
than air included in the gas-air mixture is provided to the
burner.
3. The gas-fired heater of claim 1, further comprising: a collector
box coupled to the heat exchanger and the combustion fan.
4. The gas-fired heater of claim 3, further comprising: a
condensate drain coupled to the collector box, the condensate drain
being configured to drain condensation from the gas-fired
heater.
5. The gas fired heater of claim 1, wherein the fan comprises a
variable-speed fan that does not affect the gas-air ratio provided
to the burner.
6. The gas-fired heater of claim 1, wherein the controller
comprises: a pressure regulator configured to: measure a pressure
drop of air in the air supply line across a venturi, and control
the valve to release an amount of gas based on the measured
pressure drop.
7. The gas-fired heater of claim 6, wherein when controlling the
valve, the pressure regulator is configured to provide a gas
pressure corresponding to or in a fixed relationship to the
measured pressure drop.
8. The gas-fired heater of claim 1, further comprising: a venturi
coupled to the burner and gas valve, wherein a pressure drop is
measured over the venturi.
9. The gas-fired heater of claim 1, wherein the controller is
configured to: provide a constant gas-to-air mixture to the
burner.
10. A system, comprising: a gas-fired heater, the gas-fired heater
comprising: a gas supply, an air supply, a valve coupled to the gas
supply, a controller coupled to the valve, the controller
configured to control the valve to control a gas-air mixture, a
burner configured to receive the gas-air mixture and burn the
gas-air mixture, a heat exchanger coupled to the burner, the heat
exchanger configured to output heated air, and a fan located
adjacent the heat exchanger, the fan being configured to pull flue
gases through the heat exchanger and the gas-air mixture through
the burner, the valve and a venturi coupled to the air supply.
11. The system of claim 10, wherein the gas-fired heater further
comprises: an enclosure to house the burner and heat exchanger,
wherein the enclosure includes no secondary air inlets.
12. The system of claim 10, wherein the gas-fired heater further
comprises: a collector box coupled to the heat exchanger and the
fan, and a condensate drain coupled to the collector box, the
condensate drain being configured to drain condensation from the
system.
13. The system of claim 10, wherein the fan comprises a variable
speed fan that does not affect the gas-air ratio provided to the
burner.
14. The system of claim 10, wherein the controller comprises: a
zero pressure regulator configured to: measure a pressure drop of
air in the air supply across a venturi, and control the valve to
release an amount of gas based on the measured pressure drop.
15. The system of claim 10, wherein the gas-fired heater further
comprises: a venturi coupled to the burner.
16. The system of claim 10, wherein the controller is configured
to: provide a constant gas-to-air mixture to the burner.
17. The system of claim 10, further comprising: an air handling
unit coupled to the gas-fired heater.
18. The system of claim 10, wherein the heat exchanger comprises a
plate heat exchanger.
19. The system of claim 10, wherein the heat exchanger comprises a
combination tube and plate heat exchanger.
Description
RELATED APPLICATION
[0001] This application claims priority under 35 U.S.C. .sctn.119
based on U.S. Provisional Patent Application No. 61/414,997, filed
Nov. 18, 2010, the disclosure of which is hereby incorporated
herein by reference.
BACKGROUND INFORMATION
[0002] Conventional premix gas fired air heaters typically use a
combustion fan to push a gas/air mixture through a heat exchanger.
This is accomplished by means of a combustion fan located upstream
of the heat exchanger, which pushes the gas/air mixture towards the
combustion chamber. One drawback with using such conventional
premix heaters is that the combustion chamber and heat exchanger
are often over-pressurized by the combustion fan.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1 is a schematic diagram of a premix heater consistent
with an exemplary implementation;
[0004] FIG. 2 is a simplified functional block diagram of the
premix heater of FIG. 1;
[0005] FIGS. 3A and 3B are isometric views of an exemplary premix
heater consistent with an exemplary implementation;
[0006] FIG. 4 is an isometric view of an exemplary heat exchanger
that may be used in the premix heater of FIG. 1;
[0007] FIG. 5 is an isometric view of another exemplary heat
exchanger that may be used in the premix heater of FIG. 1; and
[0008] FIG. 6 is an isometric view of yet another exemplary heat
exchanger that may be used in the premix heater of FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0009] The following detailed description refers to the
accompanying drawings. The same reference numbers in different
drawings may identify the same or similar elements. Also, the
following detailed description does not limit the invention.
[0010] Embodiments described herein provide a premix air heater
that includes a downstream fan that pulls or draws air through a
heat exchanger. As a result of the location of the fan, the heat
exchanger is effectively under a negative pressure, which helps
prevent introduction of flue gases into an interior space. For
example, a small leak in the combustion chamber or heat exchanger
will not result in flue gases being expelled into the interior
space. The fan may also be a variable speed fan that does not
affect the gas-air mixture provided to the combustion chamber,
which allows the air heater to achieve high efficiency at all
loads.
[0011] FIG. 1 is a schematic view of a premix heater unit 100 in
accordance with an exemplary implementation. Referring to FIG. 1,
heater unit 100 may include gas intake supply 110, valve 120,
controller 122, air intake supply 130, burner 140, heat exchanger
150 and fan 160. The exemplary configuration illustrated in FIG. 1
is provided for simplicity. It should be understood that heater
unit 100 may include more or fewer components than illustrated in
FIG. 1.
[0012] Gas intake supply 110 may include a gas line or a connection
to a gas line that supplies gas to heater unit 100. Valve 120 may
be a control valve that operates in conjunction with controller 122
to provide a constant gas-to-air volume or ratio with respect to
heater unit 100. For example, controller 122 may include a
pneumatic controller or electronic controller that opens/closes
valve 120 to a point that ensures that the gas/air ratio provided
to burner 140 is provided at the desired level, as described in
more detail below.
[0013] Air intake supply 130 may include an air intake area in
which air may be received, as illustrated by the arrow in FIG. 1.
For example, air may be received through an air inlet connection
located on the external side of heater unit 100. In an exemplary
implementation, air intake supply 130 may include restrictions 132,
also referred to herein as venturi 132, that control the air flow
in heater unit 100. For example, restrictions 132 may create a
narrowing or venturi to reduce the size of the openings in air
intake supply 130. Such restrictions 132 may decrease the pressure
of air on the downstream side of the restrictions.
[0014] As illustrated in FIG. 1, after gas flows through valve 120,
gas from gas intake supply 110 is mixed with air at area 136. A
gas/air mixture may then be provided to burner 140 at the input to
burner 140, illustrated as area 138 in FIG. 1. In an exemplary
implementation, controller 122 may ensure that the gas-to-air
(gas/air) ratio provided to burner 140 is constant. That is,
regardless of the speed of fan 160, the gas/air ratio is maintained
at a constant level. This may help heater unit 100 achieve and
maintain heating efficiency at all loads or modulation levels.
[0015] Burner 140 may include a burner/combustion unit that is used
to provide combustion to burn the incoming gas/air mixture. Heat
exchanger 150 may be coupled to burner 140 and may operate to
perform heat transfer with respect to output from burner 140 and
output heated air for warming an interior space.
[0016] Fan 160 may be a variable speed fan that acts to "pull" or
draw the gas/air mixture through heat exchanger 150. For example,
fan 160 may essentially produce a negative pressure with respect to
heat exchanger 150. This negative pressure acts to pull the gas/air
mixture from area 138 through burner 140 and heat exchanger 150.
The downstream location of fan 160 with respect to the flow of the
gas/air mixture to burner 140 and heat exchanger 150 also prevents
flue gases from entering the interior space. That is, all gases
will be pulled through heat exchanger 150 and will not be expelled
directly into the interior space. As a result, heater unit 100 may
provide little to no risk of dangerous emissions into an interior
space, thereby achieving maximum safety.
[0017] An enclosure (not shown in FIG. 1) may be used to house the
components of heater unit 100. For example, the enclosure may be
metal or some other material (e.g., a composite).
[0018] FIG. 2 illustrates a simplified functional view of heater
unit 100 of FIG. 1 in accordance with an exemplary implementation.
Referring to FIG. 2, heater unit 100 may include gas/air controller
210, venturi 132, burner 140, heat exchanger 150 and variable speed
fan 160. Gas/air controller 210 may include valve 120 and
controller 122 of FIG. 1. In an exemplary implementation, gas/air
controller 210 may include pneumatic controls that provide a zero
pressure governor that releases an amount of gas from gas intake
supply 110 corresponding to or in a fixed relationship to the
pressure drop of combustion air over a venturi (e.g., venturi 132)
located in air intake supply 130. For example, gas/air controller
210 may measure the air pressure drop in air supply line 130 caused
by venturi 132 (FIG. 1). Gas/air controller 210 may then control
valve 120 to provide gas pressure corresponding to the measured air
pressure drop caused by venturi/restrictions 132. In this manner,
gas/air controller 210 may provide a constant gas/air mixture to
burner 140 that is independent of the speed of fan 160.
[0019] As illustrated in FIG. 2, gas/air controller 210 may be
coupled to venturi 132. In an exemplary implementation, venturi 132
may be mounted or coupled directly to burner 140. Burner 140 may
include a burner box to burn the gas/air mixture provided via
venturi 132. Heat exchanger 150 may receive the output from burner
140 and perform a heat exchange process to provide heated air to an
interior space. In an exemplary implementation, burner 140 and heat
exchanger 150 may be contained within a sealed box/enclosure that
includes no secondary air inlets. That is, air received via venturi
132 and used during combustion by burner 140 is premixed with the
gas.
[0020] Fan 160 (also referred to herein as combustion fan 160), as
described above, may be a variable speed fan located downstream of
heat exchanger 150. As described above, the downstream location of
combustion fan 160 with respect to heat exchanger 150 effectively
creates a negative pressure on burner 140 and heat exchanger 150.
As a result, flue gases are "sucked" through heat exchanger 150.
Therefore, if a leak occurred in burner 140, extra air may be
sucked into heat exchanger 150. Flue gases, however, would not
escape heat exchanger 150 and would not enter the interior space.
In this manner, fan 160 reduces the potential for harmful emissions
into an interior space.
[0021] The exemplary configuration illustrated in FIG. 2 is
provided for simplicity. It should be understood that heater unit
100 may include more or fewer devices than illustrated in FIG.
2.
[0022] FIG. 3A illustrates a three dimensional graphical view of
heater unit 100 consistent with an exemplary implementation.
Referring to FIG. 3A, heater unit 100 may include enclosure 300
that houses elements discussed above with respect to FIGS. 1 and 2.
For example, enclosure 300 may house burner 140, heat exchanger 150
and combustion fan 160. Enclosure 300 may also house burner box
310, tubes 320, collector box 330 and main air fan 340, as
illustrated in FIG. 3A. The sides of enclosure 300 are not shown in
FIG. 3A. However, as discussed above, enclosure 300 may form a
complete enclosure around the components illustrated in FIG.
3A.
[0023] Referring to FIG. 3A, burner 140 may receive the gas/air
supply via, for example, a gas/air supply inlet. A venturi (not
shown), such as venturi 132 (FIG. 1), may also be coupled to
gas/air supply inlet. Burner 140 may be included in burner box 310,
which may be a completely sealed box made from, for example,
stainless steel. As described above, burner box 310 may include no
secondary or supplemental air inlets. That is, all the air used
during combustion is provided by the gas/air mixture provided via a
gas/air supply inlet.
[0024] In the implementation illustrated in FIG. 3A, tubes 320 may
be coupled (e.g., welded) to burner box 310 and may be made of, for
example, stainless steel. A turning box (not shown) may be coupled
to tubes 320 to collect condensation on low loads. Tubes 320 may
also guide flue gases to heat exchanger 150. A condensate drain may
also be used to guide the condensate from the turning box to
collector box 330.
[0025] Heat exchanger 150 may include any number of different types
of heat exchangers. For example, in one implementation, heat
exchanger 150 may include a shell and tube heat exchanger. In other
implementations, heat exchanger 150 may include a plate heat
exchanger. In still other implementations, heat exchanger 150 may
include a combination of shell and tube heat exchanger and a plate
heat exchanger. In the implementation illustrated in FIG. 3A,
assume that the heat exchanger 150 includes a number of plate heat
exchangers. The plate heat exchangers may be fabricated separately
with a turning box, or in a single U-shape. In either case, heat
exchanger 150 may be configured/designed such that condensation is
always achieved, even while heater unit 100 is at full load. That
is, heater unit 100 will not have to introduce additional/secondary
supply air to burner 140 to achieve condensation. This helps ensure
that heater unit 100 will have very good efficiency regardless of
the speed of combustion fan 160 and that high efficiency may be
maintained at all modulations of heater unit 100.
[0026] Collector box 330 may be coupled to heat exchanger 150 and
may include a single condensate drain that drains all condensate
from heater unit 100. Collector box 330 may also be coupled to
combustion fan 160 and a supply duct (not shown) that provides
heated air to an interior space. For example, speed controlled fan
160 may be mounted adjacent collector box 330, as illustrated in
FIG. 3A. Combustion fan 160, also referred to herein as exhaust
flue fan 160, may include outlet connection 352 for exhausting flue
gases from heater unit 100.
[0027] Air inlet connection 354 illustrated in FIG. 3A may provide
combustion air to burner 140 to aid in igniting or combustion of
the gas/air mixture provided to burner 140 via area 138 illustrated
in FIG. 1. That is, air inlet connection 354 may provide pure
combustion air to burner 140.
[0028] Main air fan 340 may be used to provide the heated air to
the interior space. In some implementations, main air fan 340 may
not be required. For example, if heater unit 100 is incorporated
into an air handling unit, main air fan 340 may not be
required.
[0029] FIG. 3B illustrates another view of heater unit 100 of FIG.
3A. In FIG. 3B, main air fan 340 is not mounted to enclosure 300.
In addition, the top of enclosure 300 is not shown for simplicity.
As described above, a combustion fan 160 may be mounted adjacent
collector box 330 (not shown).
[0030] In an exemplary implementation, heater unit 100 may be used
as a heater for an interior space, such as for factories, garages,
warehouses, buildings, etc. Heater unit 100 may also be used as a
duct heater or can be used in connection with air handling units.
For example, heater unit 100 may be easily integrated into various
different air handling units. In each case, heater unit 100 may
provide efficient heating with reduced risk of harmful emissions
into an interior space.
[0031] As discussed above with respect to FIGS. 1 and 2, heater
unit 100 may include various different types of heat exchangers.
For example, FIG. 4 illustrates a portion of heater unit 100 in an
exemplary implementation. Referring to FIG. 4, heater unit 100
includes burner box 310, a number of tubes 320 and a number of
plates 410. In this implementation, heat exchanger 150 is a plate
heat exchanger that includes multiple plates 410. Each plate 410
has a relatively large surface area and includes a number of
dimples 412. Dimples 412 aid in maintaining spacing between plates
410 to enhance heat transfer.
[0032] FIG. 5 illustrates a portion of heater unit 100 in another
exemplary implementation. Referring to FIG. 5, heater unit 100
includes burner box 310, a number of tubes 320 and a number of
plates 510. In this implementation, heat exchanger 150 is a
combination of a tube heat exchanger and plate heat exchanger that
includes multiple plates 510. Each plate 510 includes a tube
element 512 and a plate element 514. Each of plate elements 514 has
a relatively large surface area and a number of holes to provide
fluid flow passages for heat transfer.
[0033] FIG. 6 illustrates a portion of heater unit 100 in a yet
another exemplary implementation. Referring to FIG. 6, heater unit
100 includes burner box 310, a number of tubes 320 and a number of
plates 610. In this implementation, heat exchanger 150 is a plate
heat exchanger that includes multiple plates 610. Each plate 610
has a relatively large surface area and includes a number of
indentations or grooves 612 that may increase the surface area of
plates 610 to enhance heat transfer.
[0034] Heater unit 100, consistent with implementations described
herein, may operate to provide heated air to an interior space,
while significantly reducing or eliminating a chance of harmful
emissions into an interior space. Heater unit 100 may also be
relatively compact in size and may be used in conjunction with air
handling units, as a duct heater/furnace or with other
systems/devices.
[0035] The foregoing description of exemplary implementations
provides illustration and description, but is not intended to be
exhaustive or to limit the embodiments described herein to the
precise form disclosed. Modifications and variations are possible
in light of the above teachings or may be acquired from practice of
the embodiments.
[0036] For example, implementations described above refer to heater
unit 100 being used with various types of heat exchangers and/or
burners. It should be understood that heater unit 100 may be used
with other types of burners and/or heat exchangers.
[0037] Although the invention has been described in detail above,
it is expressly understood that it will be apparent to persons
skilled in the relevant art that the invention may be modified
without departing from the spirit of the invention. Various changes
of form, design, or arrangement may be made to the invention
without departing from the spirit and scope of the invention.
Therefore, the above mentioned description is to be considered
exemplary, rather than limiting, and the true scope of the
invention is that defined in the following claims.
[0038] No element, act, or instruction used in the description of
the present application should be construed as critical or
essential to the invention unless explicitly described as such.
Also, as used herein, the article "a" is intended to include one or
more items. Further, the phrase "based on" is intended to mean
"based, at least in part, on" unless explicitly stated
otherwise.
* * * * *