US20110146652A1

US20110146652A1 - Direct fired heaters with in-shot burners, tubular combustion chambers, and/or variable venturi

Info

Publication number: US20110146652A1
Application number: US12/640,803
Authority: US
Inventors: James Eugene Kovacs
Original assignee: Cambridge Engineering Inc
Current assignee: Cambridge Engineering Inc
Priority date: 2009-12-17
Filing date: 2009-12-17
Publication date: 2011-06-23

Abstract

Exemplary embodiments of the present disclosure include direct fired heaters and methods relating to the operation of direct fired heaters. An exemplary embodiment of a direct fired heater generally includes one or more in-shot burners and one or more combustion tubes configured to receive combustion air emanating from the one or more in-shot burners. The direct fired heater includes a passageway having an inlet configured to receive or intake a circulating air flow. The passageway may include a venturi portion downstream of the inlet in fluid communication with the exit ends of the combustion tubes. The flow of circulating air through the venturi portion may induce flow of combustion air through the one or more combustion tubes.

Description

FIELD

The present disclosure generally relates to direct fired heaters.

BACKGROUND

This section provides background information related to the present disclosure which is not necessarily prior art.
Many gas fired residential furnaces and small commercial heaters (unit heaters under 400,000 BTU per hour (BTU/h)) vent the products of combustion to the outdoors. In these types of furnaces and heaters, the products of combustion from a burner, such as a ribbon type burner, pass through a heat exchanger, such as a clamshell-type heat exchanger, and the flue gasses are routed to the outdoors. Circulating air from within the space to be heated is forced over the heat exchangers by a circulating fan, and then distributed throughout the space.
With the requirement for improved efficiency, more recent designs for small residential heaters use relatively small diameter tubular heat exchangers in the form of elongated tubes that are generally U-shaped or serpentine shaped. In these designs, the flame is directed into the end of each elongated tube by a burner known as an “in-shot” burner. Smaller diameter tubes, which have higher restriction to the flow rate of flue gas relative to larger diameter tubes, provide improved heat transfer. But combustion air will not pass through the small diameter tubular heat exchangers by convection alone, and a draft inducer fan is required to draw the combustion air through the heat exchanger tubes and exhaust flue to the outdoors. A circulating blower is still used to force circulating air over the heat exchangers, which is then distributed throughout the space.
Direct fired commercial heaters are usually large, (from 400,000 Btu/h to several million Btu/h), complex, expensive and either of a draw through or blow through design. In direct fired commercial heaters, circulation air and products of combustion are vented directly into the space being heated, unlike indirect fired heaters that vent combustion products to the outdoors. Circulating air may be partially or completely drawn from outside, and circulation air flow to the heater is provided by a circulating air blower. Since all of the heat from combustion remains in the space, efficiency tends to be about 92% for natural gas. (100% less the heat of vaporization of the water in the flue products). The inventor has also recognized that the draw through design is further limited in maximum temperature rise, since the heat from combustion passes over components, such as the circulating blower motor and through the blower itself.

SUMMARY

This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
Exemplary embodiments of the present disclosure include direct fired heaters and methods relating to the operation of direct fired heaters. An exemplary embodiment of a direct fired heater generally includes one or more in-shot burners and one or more combustion tubes configured to receive combustion air emanating from the one or more in-shot burners. The direct fired heater includes a passageway having an inlet configured to receive or intake a circulating air flow. The passageway may further include a venturi portion downstream of the inlet in fluid communication with the exit ends of the combustion tubes. The flow of circulating air through the venturi portion may induce flow of combustion air through the one or more combustion tubes.
Another exemplary embodiment of a direct fired heater generally includes a passageway having an inlet configured to intake circulating air and a venturi portion downstream of the inlet. The direct fired heater includes baffle movable between at least a first height in which the venturi portion has a first cross-sectional area and a second height lower than the first height such that the venturi portion has a second cross-sectional area larger than the first cross-sectional area. A rotating cam device is pivotably coupled to the baffle for pivotal movement between a first position in which the baffle is at the first height and a second position in which the baffle is at the second height. An actuator is coupled to the rotating cam device for rotating the rotating cam device between the first and second positions to selectively change the height of the baffle between the first and second heights.
Another exemplary embodiment of a direct fired heater generally includes one or more combustion chambers each having an exit end. The direct fired heater includes a circulating air blower configured to establish a flow of circulating air and a passageway. The passageway has an inlet in communication with the circulating air blower and a venturi portion downstream of the inlet in fluid communication with the exit ends of the one or more combustion chambers. The passageway is configured such that circulating air flow through the venturi portion creates a venturi effect that induces flow of combustion air through the one or more combustion chambers, without requiring operation of any blower other than the circulating air blower.
Another exemplary embodiment of a direct fired heater includes one or more in-shot burners and one or more combustion tubes configured to receive combustion air emanating from the corresponding one or more in-shot burners. Each combustion tube has an exit end. A passageway includes an inlet configured to intake circulating air and an outlet downstream of the exit ends of the one or more combustion tubes. The passageway is configured such that combustion air and circulating air are mixed downstream of the exit ends of the combustion tubes and discharged from the outlet of the passageway.
An exemplary embodiment of a method relating to the operation of a direct fired heater generally includes inducing combustion air flow through one or more combustion chambers by forcing circulating air through a venturi portion in fluid communication with the exit ends of the one or more combustion chambers.
Another exemplary embodiment of a method relating to the operation of a direct fired heater generally includes operating one or more in-shot burners configured to fire into the one or more combustion tubes having exit ends. The method may also include mixing combustion air and circulating air downstream of the exit ends of the one or more combustion tubes. The method may further include discharging combustion air and circulating air from an outlet of a passageway that is downstream of the exit ends of the one or more combustion tubes.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 is a perspective view of a direct fired heater according to an exemplary embodiment;

FIG. 2 is a front view of the direct fired heater shown in FIG. 1;

FIG. 3 is another front view of the direct fired heater shown in FIG. 1 with the doors removed so as to illustrate interior areas and components of the direct fired heater;

FIG. 4 is another perspective view of the direct fired heater shown in FIG. 1 with portions removed so as to illustrate interior areas and components of the direct fired heater;

FIG. 5 is a perspective view of a portion in FIG. 4 illustrating in-shot burners and tubular combustion chambers or tubes of the direct fired heater shown in FIG. 1 with the burner mounting bracket hidden for clarity;

FIG. 6 is another front view of the direct fired heater shown in FIG. 1 with portions removed so as to illustrate interior areas and components of the direct fired heater;

FIG. 7 is a view of a portion in FIG. 6 illustrating one embodiment of a venturi portion having an adjustable opening area that may be included in the direct fired heater shown in FIG. 1;

FIG. 8 is a side view of the direct fired heater shown in FIG. 1 with portions removed so as to illustrate the exit ends of the tubular combustion chambers or tubes of the direct fired heater;

FIG. 9 is another perspective view of the direct fired heater shown in FIG. 1 with portions removed so as to illustrate interior areas and components of the direct fired heater;

FIG. 10 illustrates an exemplary embodiment of a venturi portion having an adjustable opening area that may be included in the exemplary direct fired heater shown in FIGS. 1 through 9, and illustrating the cam in the up position when there is no power to the actuator and illustrating the height of the opening in inches for purposes of illustration only according to exemplary embodiments;

FIG. 11 illustrates the exemplary embodiment shown in FIG. 10 but with the cam in the down position when the actuator is powered on and illustrating the height of the opening in inches for purposes of illustration only according to exemplary embodiments; and

FIG. 12 is a line graph illustrating exemplary combustion test results measured for a prototype of the direct fired heater shown in FIGS. 1 through 9 having the dimensions illustrated in FIGS. 10 and 11.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference to the accompanying drawings.
According to one aspect of the present disclosure, there are provided various exemplary embodiments of direct fired heaters. An exemplary embodiment of a direct fired heater generally includes one or more in-shot burners and one or more combustion tubes configured to receive combustion air emanating from the one or more in-shot burners. The one or more combustion tubes generally include exit ends through which the combustion air passes or is discharged. The direct fired heater further includes a passageway having an inlet configured to receive circulating air flow. The passageway further includes a venturi portion downstream of the inlet and in fluid communication with, at, or proximate the exit ends of the one or more combustion tubes. The passageway and venturi portion are configured such that flow of circulating air through the venturi portion induces or causes flow of combustion air through the one or more combustion tubes, independent of and/or without requiring the use of an additional blower (draft inducer fan) specifically provided to cause or induce combustion air flow.
In one or more exemplary embodiments, the passageway may take the form of a plenum having an inlet in communication with a circulating air blower, an outlet through which both the combustion air and circulating air are discharged, and a venturi-shaped portion downstream of the inlet that defines a constriction between the inlet and the outlet. The venturi portion forms a constriction or reduced cross-sectional area through which circulating air flows, which produces a reduction in fluid pressure downstream of the venturi portion that induces fluid flow through the one or more combustion tubes. As disclosed herein, the one or more combustion tubes may be positioned within the plenum in some embodiments. But in alternative embodiments, one or more combustion tubes may be positioned outside of or external to the plenum, but the exit ends of the one or more combustion tubes may be positioned relative to (e.g., adjacent, at, etc.) the venturi-shaped portion of the plenum in fluid communication with the venturi-shaped portion.
In various exemplary embodiments, the direct fired heater further includes a circulating air blower for establishing circulating air flow. The circulating air blower forces circulating air through the passageway, and through the venturi portion, which may be adjacent or at the exit ends of the tubular combustion chambers or tubes. At the venturi portion, the circulating air flow creates a venturi effect that induces the flow of combustion air through the one or more combustion tubes, without requiring the use of any additional blower other than the circulation air blower. Accordingly, such exemplary embodiments do not require any blower that is configured or employed exclusively for establishing combustion air flow through the combustion tubes, such as a draft inducer fan.
In one or more exemplary embodiments, the direct fired heater may further comprise a venturi portion having an adjustable element, which is movable for varying the cross-sectional opening area within the venturi portion of the passageway (e.g., plenum, etc.). In such embodiments, the direct fired heater is configured to control the movement of the adjustable element for varying the fluid pressure downstream of the venturi portion, which thereby varies the level of combustion air flow through the one or more combustion tubes. This allows for regulation of the rate of combustion air flow and for maintaining carbon monoxide and/or nitrogen dioxide levels below a predetermined amount to provide for safe operation of the direct fired heater.
In various exemplary embodiments, the direct fired heater may further comprise a gas valve in communication with the in-shot burners. The gas valve may be a valve capable of varying the flow rate of gas to the one or more in-shot burners. With such gas valves, the direct fired heater is configured to vary the rate of gas flow to the one or more in-shot burners based on a sensed outlet air temperature and temperature rise though the heater, to thereby indirectly sense the outdoor air temperature and vary the level of heating operation commensurate with the indirectly sensed outside air temperature.
Exemplary embodiments of the present disclosure include direct fired heaters, such as relatively small direct fired commercial heaters that may be 400,000 BTU/h or less. In some embodiments, a direct fired heater includes any one of, any combination of, or all of the following features: in-shot burners, small tubular combustion tubes and/or heat exchangers, venturi-shaped passageways or plenums, and/or venturi portions that are variable, for example, depending on burner inputs. In some embodiments, a venturi-shaped plenum is used in conjunction with a circulating air blower to create a reduced pressure or “negative” pressure at the exit ends of the combustion tubes for inducing or causing flow of combustion air through the combustion tubes. This allows for the elimination of a draft inducer fan that would provide for combustion air flow through the combustion tubes.
In various exemplary embodiments, the direct fired heater includes one or more in-shot burners and one or more corresponding tubular combustion chambers or tubes. The design is modular such that output may be increased by adding tubes and burners. In this example, all air for combustion is drawn from outside, and circulating air may be drawn from outside or inside. Combustion air and circulating air is mixed and vented directly into the space being heated, unlike indirect fired heaters in which combustion air is vented outdoors. Instead of employing a draft inducer fan to establish combustion air flow through the combustion tubes, a negative pressure or reduced pressure is generated by circulating air that is forced through a venturi-shaped plenum, which creates a venturi effect at the exit end of the combustion tubes that induces flow through the tubes. These features and other aspects of the present disclosure will be described in more detail in the following exemplary embodiments.
With reference now to the figures, FIGS. 1 through 9 illustrate an exemplary embodiment of a direct fired heater 100 embodying one or more aspects of the present disclosure. In this example of a direct fired heater 100, the combustion air and circulating air may be drawn from ambient air outside of a building or residence. The entire unit may be placed inside or outside a building. The direct fired heater 100 may be relatively small (e.g., 400,000 Btu/h or less, etc.). Alternative embodiments may include a larger or smaller direct fired heater that is used for commercial and/or residential purposes.
With continued reference to FIG. 2, the direct fired heater 100 includes a heated air discharge 101, a control panel and/or plenum access door 102, and a burner/blower access door 103. A viewport 104 is provided in the door 103 to allow for viewing of the burner compartment 109. Also shown in FIG. 2 are a gas connection 105, electrical connection 106, and an air inlet 107. The heated air discharge 101 and the circulating air intake 107 are also shown in FIG. 6 along with a combustion air intake 120.
FIG. 3 illustrates the direct fired heater 100 without the doors 102, 103 in order to illustrate the interior areas and components of the direct fired heater 100. The direct fired heater 100 includes one or more in-shot burners 108, each in-shot burner having an inlet end 108A and an outlet end 108B. The in-shot burners 108 are located within the burner compartment 109. The direct fired heater 100 further includes one or more open-ended combustion tubes 122 (FIG. 6). Each combustion tube 122 has an inlet end 121 (FIG. 5) and an exit end 123 (FIG. 7). The inlet ends 121 of the one or more combustion tubes 122 are configured to receive combustion air emanating from the corresponding outlet ends 1088 of the one or more in-shot burners 108. Thus, in-shot burners 108 are configured for firing into the open ended combustion tubes 122 (FIG. 6) (e.g., aluminized steel tubing, etc.). While the tubes 122 are shown with circular cross-sections in FIG. 8, other embodiments may include one or more tubes with a non-circular cross section (e.g., rectangular, oval, square, triangular, etc.). In addition, other embodiments may include more or less than the five in-shot burners 108 and more of less than five combustion tubes 122 shown in the figures. In one example embodiment, the direct fired heater 100 includes five combustion tubes each of which are 3 feet long with a 2.25 inch diameter, and five in-shot burners having 0.8 inch diameters and 0.116 inch orifices. The specific dimensions in this paragraph (as are all dimensions set forth herein) are provided for purposes of illustration only and not for limitation, as other embodiments may be configured differently so as to include differently configured (e.g., larger or smaller, etc.) combustion chambers and/or burners (e.g., burners of different sizes and/or types besides in-shot burners, etc.).
As shown in FIG. 3, the direct fired heater 100 includes a control panel 110. Also shown in FIG. 3, the heater 100 further includes motor and sheave 112, belt 113, and blower and sheave 114, which are part of the circulating air blower 118 (FIG. 4). The circulating air blower 118 is configured to establish the flow of circulating air into the direct fired heater 100. The circulating air blower 118 is configured to force circulating air through the passageway 111, which is described below.
The passageway 111 has an inlet 111A in communication with the circulating air blower 118. The passageway 111 further includes a venturi portion 115 that is downstream of the inlet 111A. The venturi portion 115 is in fluid communication with and proximate the exit ends 123 (also shown in FIG. 8) of the combustion tubes 122. The passageway 111 may further include an outlet 111B through which both combustion air and circulating air are discharged.
While the exemplary direct fired heater 100 is described with reference to a passageway 111, it should be noted that the passageway 111 may more specifically comprise a plenum, but may be any shape or construction suitable for communication of circulating air therethrough. The passageway 111 shown in FIG. 3 may take the form of a plenum having an inlet 111A in communication with a circulating air blower 118, an outlet 111B through which both the combustion air and circulating air are discharged, and a venturi-shaped portion 115 downstream of the inlet 111A. The venturi-shaped portion 115 defines a constriction, throat, or reduced cross-sectional area between the inlet 111A and the outlet 111B. Specifically, the cross-sectional area of the opening in the throat or venturi-shaped portion 115 through which circulation air flows is smaller than the cross-sectional area of the inlet opening 111A. Also, the tubes 122 are disposed within the generally box-shaped plenum chamber that tapers or narrows in the direction of air flow through the plenum. In alternative embodiments, however, the combustion tubes 122 may be outside of or external to the passageway 111.
The passageway 111, as disclosed herein, may eliminate the need for a draft inducer fan. The passageway 111 and venturi portion 115 are configured such that the circulating air flow through the venturi portion 115 creates a venturi effect that induces or causes flow of combustion air through the combustion tubes 122, without operation of any additional blower (draft inducer fan) other than the circulating air blower 118. For this illustrated embodiment, the direct fired heater 100 does not require any additional blower that is configured or employed exclusively for establishing combustion air flow through the combustion tubes, such as a draft inducer fan. The venturi portion 115 establishes a constriction or reduced cross-sectional area through which the circulating air flows, to produce a reduction in fluid pressure at the exit ends 123 of the combustion tubes and downstream of the venturi portion 115. The reduced pressure, which may be called a negative pressure relative to pressure upstream, creates a venturi-effect that induces combustion air flow through the one or more combustion tubes. Accordingly, the illustrated direct fired heater 100 does not include a draft inducer fan or induced draft fan.
Also shown in FIG. 4 is a gas valve 117 of the direct fired heater 100, which is in communication with the in-shot burners 108. The gas valve 117 supplies a gas, such as natural gas or propane gas, to the in-shot burners 108. The gas is preferably supplied to the in-shot burners 108 through a gas manifold 116 that is in communication with the inlet ends 108A of the one or more in-shot burners 108.
In one example construction of the exemplary embodiment, the direct fired heater 100 may have a venturi portion 115 that includes an adjustable element 127 for varying the cross-sectional area of the opening within the venturi portion 115. The direct fired heater 100 is configured to control the movement of the adjustable element 127 to change the cross-sectional opening area of the constriction provided by the venturi portion, for varying the fluid pressure downstream of the venturi portion 115. By varying the venturi portion's cross-sectional opening area, the fluid pressure downstream of the venturi portion 115 and venturi effect can be changed, to thereby vary the level of combustion air flow through the combustion tubes 122. This allows for regulation of the rate of combustion air flow, and for maintaining carbon monoxide and/or nitrogen dioxide levels below a predetermined amount to provide for safe operation of the direct fired heater 100.
In FIG. 7, there shown an exemplary means or assembly by which the fluid pressure at the ends 123 of the tubular combustion chambers or tubing 122 may be adjusted, to vary the venturi effect that controls the rate of combustion air flow through the combustion tubes 122. As used herein, the venturi effect generally refers to the reduction in fluid pressure that results when a fluid flows through a narrower section or constriction at an increased fluid velocity through the narrower section or constriction.
FIG. 7 illustrates an exemplary embodiment of a venturi portion 115 having an adjustable opening area that may be included in the direct fired heater 100. As shown in FIG. 7, the adjustable venturi portion 115 includes an actuator 124 and a rotating cam 125. The actuator 124 may comprise a two-position actuator having a shaft 126 that is coupled to the rotating cam 125 for controllably rotating the rotating cam 125 between an up or first position (FIGS. 7 and 10) and a down or second position (FIG. 11). In this example, the rotating cam 125 may be in the up position (FIGS. 7 and 10) when there is no power to the actuator 124. But the actuator 124 may be powered on to move the rotating cam 125 to the down or second position (FIG. 11). As can be seen by a comparison of FIGS. 10 and 11, rotating the cam 125 from the up or first position (FIG. 10) to the down or second position (FIG. 11) changes the height of the baffle 127 (e.g., from 3.5 inches to 4 inches in this example, etc.). Thus, the height of the adjustable baffle 127 may be used to vary the cross-sectional opening area of the venturi-shaped portion 115. When the cam 125 is in the up or first position (FIGS. 7 and 10) with no power to the actuator 124, the cross-sectional opening area or size of the venturi portion 115 is smaller than the cross-sectional opening area or size of the venturi portion 115 when the cam 125 is in down or second position (FIG. 11) when the actuator 124 is powered on. The specific dimensions (i.e., 3.5 inches and 4 inches) shown in FIGS. 10 and 11 (as are all dimensions set forth herein) are provided for purposes of illustration only and not for limitation, as other embodiments may be configured differently so as to include a larger or smaller venturi portion.
In some embodiments, an actuator may be provided that is configured to move the adjustable baffle 127 to one or more positions between the positions shown in FIGS. 10 and 11. In such embodiments, the height of the baffle 127 may be controllably adjusted for infinitely adjusting the venturi effect. Providing an adjustable baffle may provide for better regulation of combustion, which may depend on burner input or operating level, as will be explained below.
In one or more embodiments, the gas valve 117 of the direct fired heater 100 may be a modulating gas valve that is capable of varying the flow rate of gas to the one or more in-shot burners 108. The modulating gas valve 117 may be configured to adjust the flow rate of gas between a first, higher flow rate and at least one other reduced flow rate that is lower than first, higher flow rate. Alternatively, the gas valve 117 may comprise a two stage gas valve that is configured to control the flow rate of gas at one of either the first, higher flow rate (which may comprise a maximum flow rate) or a reduced flow rate. In either case, the direct fired heater 100 may be configured to change the rate of gas flow to the in-shot burners 108 based, at least in part, on outdoor air temperature. For example, the direct fired heater 100 may be configured to vary the rate of gas flow to the in-shot burners 108 based on a sensed outlet air temperature and temperature rise though the heater, to thereby indirectly sense the outdoor air temperature and vary the level of heating operation commensurate with the indirectly sensed outside air temperature.
In a modulating burner where the flow rate of gas is varied, the combustion air flow within the combustion tubes 122 is affected by changes in burner fire rate. In the direct fired heater 100, the rate of flow through the combustion tubes 122 may be adjusted as needed to correspond to changes in the rate of gas flow to the in-shot burners 108, by controlling the actuator 124. The fluid pressure at the ends 123 of the combustion tubes 122 may be varied by actuating the rotating cam 125 and actuator 126, for example, to adjust the cross-sectional opening area and resulting venturi effect. In turn, this adjustability may be used, for example, to maintain low carbon monoxide and/or nitrogen dioxide levels (e.g., below a predetermined level as shown in FIG. 12, etc.).
In operation, the direct fired heater 100 may include or be in communication with a temperature sensor for sensing the temperature of the outdoor ambient air. As another example, the direct fired heater 100 may indirectly sense the temperature of the outdoor or outside ambient air by sensing the outlet air temperature and temperature rise though the heater, and then vary the level of heating operation commensurate with indirectly sensed outside air temperature.
The direct fired heater 100 may respond to a moderate outside ambient temperature by controlling the gas valve 117 to establish a reduced gas flow rate (e.g., 50% reduced gas flow rate, etc.). In some embodiments, the gas flow rate may be reduced from an original or initial gas flow rate of 200,000 Btu/hr down to a reduced gas flow rate of 100,000 Btu/hr.
Concurrent with the reduced gas flow rate, the direct fired heater 100 may be configured to control the actuator 124 to move the adjustable baffle 127 to the lower height position for increasing (maximizing in some embodiments) the cross-sectional area of the venturi portion 115. The lower height of the baffle 127 reduces the constriction or increases the cross-sectional opening area, which in turn reduces the venturi effect and induces a lower rate of flow through the combustion tubes 122.
When the outside ambient temperature is cold or low, the direct fired heater 100 may be configured to control the gas valve 117 to establish a higher gas flow rate (which may be a maximum flow rate in some embodiments). An increase in the rate of combustion without an increase in circulation air flow may lead to undesirable levels of carbon monoxide and/or nitrogen dioxide. Thus, concurrent with the switch to the higher gas flow rate (e.g., increasing the gas flow rate from 100,000 Btu/hr to 200,000 Btu/hr in some embodiments, etc.), the direct fired heater 100 may be configured to control the actuator 124 to move the adjustable baffle 127 to the second, higher position for reducing (minimizing in some embodiments) the cross-sectional area of the venturi portion 115. The higher height of the baffle 127 increases the constriction and reduces the fluid pressure, which in turn increases the venturi effect that induces a higher flow rate of combustion air through the combustion tubes 122.
FIG. 12 is a line graph illustrating exemplary combustion test results in parts per million (ppm) measured for a prototype of the direct fired heater 100 shown in FIGS. 1 through 9 having the dimensions illustrated in FIGS. 10 and 11. For this exemplary testing, the prototype included five combustion tubes five combustion tubes each of which are 3 feet long each with a 2.25 inches in diameter, five in-shot burners having 0.8 inch diameters and 0.116 inch orifices, and a one inch top deflector without any nitrogen dioxide baffle. The prototype was configured as a 200,000 BTU/h direct fired heater using natural gas and a variable frequency drive at a frequency of 51.5 Hertz. During this exemplary testing, the ambient carbon monoxide (CO) was measured to be about 3.62 parts per million, the ambient nitric oxide (NO) was measured to be about 0.0013 parts per million, the ambient nitrogen dioxide (NO₂) was measured to be about 0.0164 parts per million, and the ambient temperature was measured to be about 51.2 degrees Fahrenheit (° F.). The shaded area in FIG. 12 indicates CSA allowable combustion, which were satisfied according to the combustion test results for the prototype of the direct fired heater 100. FIG. 12 also shows how the nitrogen dioxide flow rate may be changed by moving the venturi damper position from the up position (FIG. 10) to the down position (FIG. 11), to change the cross-sectional area or size of the venturi portion.
Accordingly, some exemplary embodiments of a direct fired heater may be configured such that they are associated with, allow, or provide one or more of the following features and benefits:

- more heat using less energy with a higher BTU/CFM ratio as compared to some prior heater designs; and/or
- certified for both 160° F. temperature rise and 160° F. discharge temperature at 0° F. outdoor; and/or
- energy efficient direct gas-fired heating unit; and/or
- 100% combustion efficiency (no flue or heat exchanger losses); and/or
- 100% non-recirculated fresh air improves indoor air quality;
- high velocity vertical throw diffuser that reduces stratification, provides more even heating, and saves energy; and/or
- fan only option for summer ventilation; and/or
- three mounting options (Thru-Wall; Rooftop, Under Roof); and/or
- LEED (Leadership in Energy and Environmental Design) Ready, ASHRAE 90.1 compliant design option for LEED/green buildings; and/or
- lower installation costs; and/or
- reduced maintenance costs.

Exemplary embodiments of a direct fired heater (e.g., direct fired heater 100 (FIGS. 1 through 9), etc.) may be sized differently, for example, according to the heating requirements of the intended end use. By way of example, an exemplary embodiment includes a 200,000 BTU/h direct fired heater that is about 30⅞ inches tall, about 21¼ inches wide, about 56¼ inches long with a weight of about 300 to about 320 pounds. The specific dimensions, numerical values, and materials identified in this paragraph (as are all dimensions, numerical values, and materials set forth herein) are provided for purposes of illustration only and not for limitation, as embodiments disclosed herein may be configured differently to have different configurations (e.g., more than or less than 200,000 BTU/h, etc.).
Exemplary embodiments of a direct fired heater (e.g., 100, etc.) may be used inside or outside of a building. Exemplary embodiments of a direct fired heater disclosed herein may be used in warehouses, large storage areas, door/loading dock areas, manufacturing/assembly areas, auto repair/service areas, aircraft hangars/service areas, boat storage buildings, indoor sports facilities, parking garages, green/LEED buildings, etc.
There are also disclosed herein exemplary embodiments of methods, such as methods relating to the operation of a direct fired heater. An exemplary embodiment of a method relating to the operation of a direct fired heater generally includes inducing combustion air flow through one or more combustion chambers by forcing circulating air through a venturi portion in fluid communication with the exit ends of the one or more combustion chambers. Another exemplary embodiment of a method relating to the operation of a direct fired heater generally includes varying a venturi portion depending on burner input. The venturi portion is in fluid communication with the exit ends of one or more combustion chambers. Varying the venturi portion adjusts the rate of combustion air flow induced through the one or combustion chambers when circulating air is forced through the venturi portion.
Another exemplary embodiment of a method relating to the operation of a direct fired heater generally includes operating one or more in-shot burners configured to fire into the one or more combustion tubes having exit ends. The method may also include mixing combustion air and circulating air downstream of the exit ends of the one or more combustion tubes. The method may further include discharging combustion air and circulating air from an outlet of a passageway that is downstream of the exit ends of the one or more combustion tubes.
In a further exemplary embodiment, a method generally includes operating one or more in-shot burners configured to fire into one or more open-ended combustion tubes having exit ends in fluid communication (e.g., proximate, at, etc.) with a venturi portion defining a constriction. The method may also include operating a circulating air blower to force circulating air through the venturi portion, to create a venturi effect for inducing combustion air flow through the combustion tubes. The method may further include mixing combustion air and circulating air downstream of the venturi portion and venting combustion air and circulating air into the space being heated. This method (and other methods) may be performed without using a draft inducer fan. Instead, reduced or “negative” pressure in the one or more combustion tubes may be created via a plenum and venturi at the exit ends of the combustion tubes. This method (and other methods) may include varying or adjusting the cross-sectional opening area of a venturi portion in fluid communication with the exit ends of one or more combustion tubes to adjust the venturi effect for better combustion results. This method (and other methods) may include using one or more in-shot burners configured for firing into opened ended combustion tubing (e.g., aluminized steel tubing, etc.). This method (and other methods) may include increasing heating output capacity of the direct fired heater by adding one or more additional tubular heat exchangers and/or in-shot burners.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The disclosure herein of particular values and particular ranges of values for given parameters are not exclusive of other values and ranges of values that may be useful in one or more of the examples disclosed herein. Moreover, it is envisioned that any two particular values for a specific parameter stated herein may define the endpoints of a range of values that may be suitable for the given parameter (i.e., the disclosure of a first value and a second value for a given parameter can be interpreted as disclosing that any value between the first and second values could also be employed for the given parameter). Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.

Claims

1. A direct fired heater comprising:

one or more in-shot burners;

one or more combustion tubes configured to receive combustion air emanating from the corresponding one or more in-shot burners, each combustion tube having an exit end; and

a passageway having an inlet configured to intake circulating air, and a venturi portion downstream of the inlet in fluid communication with the exits ends of the one or more combustion tubes, the passageway configured such that flow of circulating air through the venturi portion induces flow of combustion air through the one or more combustion tubes.

2. The direct fired heater of claim 1, wherein the passageway is configured such that flow of circulating air through the venturi portion induces flow of combustion air through the one or more combustion tubes, without any blower for exclusively providing combustion air flow.

3. The direct fired heater of claim 1, wherein the passageway further includes an outlet downstream of the venturi portion and the exit ends of the one or more combustion tubes, the outlet operable for discharging combustion air and circulating air out of the direct fired heater.

4. The direct fired heater of claim 1, wherein the venturi portion defines a constriction having a reduced cross-sectional area that is configured such that air flow through the venturi portion produces a reduction in fluid pressure downstream of the venturi portion, which induces combustion air flow through the one or more combustion tubes.

5. The direct fired heater of claim 1, further comprising a circulating air blower in communication with the inlet of the passageway and operable for forcing circulating air through the venturi portion, to create a venturi effect that induces flow of combustion air through the one or more combustion tubes.

6. The direct fired heater of claim 5, wherein the direct fired heater is configured such that combustion air flow is induced through the one or more combustion tubes without operation of any blower other than the circulating air blower.

7. The direct fired heater of claim 1, wherein the venturi portion includes an element that is movable for varying the cross-sectional opening area of the venturi portion.

8. The direct fired heater of claim 7, wherein the direct fired heater is configured to control the movement of the element for varying the fluid pressure downstream of the venturi portion and/or for maintaining carbon monoxide and nitrogen dioxide levels below a predetermined amount.

9. The direct fired heater of claim 1, further comprising a gas valve in communication with the one or more in-shot burners and operable for varying the flow rate of gas to the one or more in-shot burners.

10. The direct fired heater of claim 1, further comprising a baffle movable between at least a first configuration in which the venturi portion has a first cross-sectional area and a second configuration in which the venturi portion has a second cross-sectional area larger than the first cross-sectional area.

11. The direct fired heater of claim 10, further comprising an actuator for moving the baffle between the first and second positions.

12. The direct fired heater of claim 11, wherein the actuator is a two-position actuator that controls the height of the baffle with a rotating cam device, to move the baffle between the first and second positions.

13. The direct fired heater of claim 10, wherein the direct fired heater is configured to control the movement of the adjustable baffle for varying the fluid pressure downstream of the venturi portion, to thereby allow for regulation of the level of combustion air flow through the one or more combustion tubes to maintain carbon monoxide and/or nitrogen dioxide below a predetermined amount.

14. The direct fired heater of claim 10, further comprising a gas valve in communication with the one or more in-shot burners, and configured to vary the rate of gas flow between a first gas flow rate and at least one reduced gas flow rate, wherein the direct fired heater is configured to control the gas valve to establish the first gas flow rate when the baffle is in first configuration and to establish the at least one reduced gas flow rate when the baffle is in the second configuration.

15. The direct fired heater of claim 1, wherein the passageway comprises a plenum.

16. A direct fired heater comprising:

one or more combustion chambers each having an exit end;

a circulating air blower configured to establish a flow of circulating air; and

a passageway having an inlet in communication with the circulating air blower, a venturi portion downstream of the inlet in fluid communication with the exit ends of the one or more combustion chambers, the passageway configured such that circulating air flow through the venturi portion creates a venturi effect that induces flow of combustion air through the one or more combustion chambers, without requiring operation of any blower other than the circulating air blower.

17. The direct fired heater of claim 16, further comprising an adjustable element for varying the cross-sectional opening area of the venturi portion.

18. The direct fired heater of claim 16, further comprising a baffle movable between at least a first configuration in which the venturi portion has a first cross-sectional area and a second configuration in which the venturi portion has a second cross-sectional area larger than the first cross-sectional area.

19. The direct fired heater of claim 16, further comprising one or more in-shot burners configured such that the one or more combustion chambers receive combustion air emanating from the corresponding one or more in-shot burners.

20. The direct fired heater of claim 16, wherein the one or more combustion chambers comprise tubes.

21. The direct fired heater of claim 16, wherein the passageway comprises a plenum and an outlet through which combustion air and circulating air are discharged.

22. A direct fired heater comprising:

a passageway having an inlet configured to intake circulating air and a venturi portion downstream of the inlet;

a baffle movable between at least a first height in which the venturi portion has a first cross-sectional area and a second height lower than the first height such that the venturi portion has a second cross-sectional area larger than the first cross-sectional area;

a rotating cam device pivotably coupled to the baffle for pivotal movement between a first position in which the baffle is at the first height and a second position in which the baffle is at the second height; and

an actuator coupled to the rotating cam device for rotating the rotating cam device between the first and second positions to selectively change the height of the baffle between the first and second heights.

23. The direct fired heater of claim 22, wherein the direct fired heater includes:

one or more in-shot burners, each in-shot burner having an inlet end and an outlet end;

one or more combustion tubes, each combustion tube having an inlet end and an exit end, the inlet ends of the one or more combustion tubes being configured to receive combustion air emanating from the corresponding outlet ends of the one or more in-shot burners, the exit ends in fluid communication with the venturi portion such that circulating air flow through the venturi portion creates a venturi effect that induces flow of combustion air through the one or more combustion tubes.

24. The direct fired heater of claim 23, wherein the direct fired heater includes a circulating air blower in communication with the inlet of the passageway and operable for forcing circulating air through the venturi portion, to create a venturi effect that induces flow of combustion air through the one or more combustion tubes, without requiring the use of an additional blower specifically provided to induce combustion air flow.

25. The direct fired heater of claim 22, wherein the direct fired heater is configured such the height of the baffle between the first and second height is varied based on burner input.

26. A direct fired heater comprising:

one or more in-shot burners;

a passageway having an inlet configured to intake circulating air and an outlet downstream of the exit ends of the one or more combustion tubes, the passageway configured such that combustion air and circulating air are mixed downstream of the exit ends of the combustion tubes and discharged from the outlet of the passageway.

27. The direct fired heater of claim 26, wherein the passageway includes a venturi portion downstream of the inlet in fluid communication with the exit ends of the one or more combustion chambers, the passageway configured such that circulating air flow through the venturi portion creates a venturi effect that induces flow of combustion air through the one or more combustion chambers.

28. The direct fired heater of claim 26, wherein the direct fired heater includes a circulating air blower in communication with the inlet of the passageway and operable for forcing circulating air through the passageway to induce flow of combustion air through the one or more combustion tubes, without requiring the use of an additional blower specifically provided to induce combustion air flow.

29. The direct fired heater of claim 26, further comprising an adjustable element for varying the cross-sectional opening area of a portion of the passageway.

30. The direct fired heater of claim 26, further comprising a baffle movable between at least a first configuration in which a portion of the passageway has a first cross-sectional area and a second configuration in which the portion of the passageway has a second cross-sectional area larger than the first cross-sectional area.

31. The direct fired heater of claim 26, wherein the passageway comprises a plenum.

32. The direct fired heater of claim 26, further comprising:

a baffle movable between at least a first height in which a portion of the passageway has a first cross-sectional area and a second height lower than the first height such that the portion of the passageway has a second cross-sectional area larger than the first cross-sectional area;

33. A method relating to operation of a direct fired heater, the method comprising inducing combustion air flow through one or more combustion chambers by forcing circulating air through a venturi portion in fluid communication with the exit ends of the one or more combustion chambers.

34. The method of claim 33, further comprising varying the venturi portion to adjust the rate of combustion air flow induced through the one or combustion chambers when circulating air is forced through the venturi portion.

35. The method of claim 33, further comprising varying the cross-sectional opening area of the venturi portion.

36. The method of claim 33, wherein the method includes operating a circulating air blower to force circulating air through the venturi portion.

37. The method of claim 33, wherein the direct fired heater does not include a draft inducer fan, and wherein the method includes operating a circulating air blower to force circulating air through the venturi portion to create a venturi effect for inducing combustion air flow through one or more combustion chambers.

38. A method relating to operation of a direct fired heater, the method comprising:

operating one or more in-shot burners configured to fire into the one or more combustion tubes having exit ends;

mixing combustion air and circulating air downstream of the exit ends of the one or more combustion tubes; and

discharging combustion air and circulating air from an outlet of a passageway that is downstream of the exit ends of the one or more combustion tubes.

39. The method of claim 38, further comprising inducing combustion air flow through the one or more combustion chambers by forcing circulating air through a venturi portion of the passageway that is in fluid communication with the exit ends of the one or more combustion chambers.