PREMIX AIR HEATER
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.
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This application claims priority under 35 U.S.C. §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 INFORMATIONConventional 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.
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.
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.
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.
Air intake supply 130 may include an air intake area in which air may be received, as illustrated by the arrow in
As illustrated in
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.
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.
An enclosure (not shown in
As illustrated in
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.
The exemplary configuration illustrated in
Referring to
In the implementation illustrated in
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
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
Air inlet connection 354 illustrated in
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.
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.
As discussed above with respect to
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.
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.
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.
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.
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.
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.
Type: Application
Filed: Nov 14, 2011
Publication Date: May 24, 2012
Applicant: THOMAS & BETTS INTERNATIONAL, INC. (Wilmington, DE)
Inventors: Chris Grammens (Oedelem), Niko Raes (Zwijnaarde)
Application Number: 13/295,136
International Classification: F24H 3/02 (20060101);