It is known to use a damper in a water heater flue. Known dampers use a physical obstruction to close the flue during standby. One example of a physical obstruction type damper is disclosed in U.S. Pat. No. 4,953,510.
The invention provides an apparatus for heating a medium. The apparatus comprises a combustion chamber; a burner within the combustion chamber and operable to create products of combustion for heating the medium to be heated; a conduit for the exhaust of the products of combustion; and an airflow apparatus. The airflow apparatus is capable of creating airflow in the absence of any opposition to the airflow, the airflow having a pressure, the airflow apparatus communicating with the conduit and operable such that the pressure of the airflow resists standby convection flow of gases out of the conduit when the burner is not operating. The airflow apparatus is adjustable to vary the magnitude of the airflow to substantially equalize the airflow and the standby convection flow of gases to create a substantially stagnant state within the conduit when the burner is not operating.
In one embodiment, for example, the apparatus for heating a medium may include a water tank. In such an embodiment, the medium to be heated may be water in the water tank, and the conduit may include a flue extending vertically through the water tank such that the hot products of combustion heat the water through the flue walls.
In some embodiments, the airflow apparatus may include first and second electrodes having opposite polarities and spaced from each other. The apparatus may also include a power source interconnected between the first and second electrodes to create a voltage difference between the first and second electrodes. The first electrode creates ions that are biased for movement toward the second electrode to generate the airflow. The magnitude of the airflow may be varied by adjusting the voltage difference.
In some embodiments, the airflow apparatus may be operable to create a second airflow having a second pressure, and the second pressure may assist the flow of gases out of the conduit when the burner is operating. The apparatus may also include a catalytic converter communicating with the conduit. The second airflow may mix into the products of combustion air from a source of air to increase the effectiveness of the catalytic converter.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.
Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order.
In operation, the burner 42 burns the fuel supplied by the fuel line 43, along with air drawn into the combustion chamber 22 through one or more air inlets 47. The burner 42 creates products of combustion that rise through the flue 26 and heat the water by conduction through the flue walls. The flow of products of combustion is driven by natural convection, but may alternatively be driven by a blower unit (not shown) communicating with the flue 26. The above-described water heater 10 is well known in the art.
During standby of the water heater 10 (i.e., when the burner 42 is not operating), the air and other gases in the flue 26 (collectively, “flue gases”) are heated by the water in the tank 14 and by the flame of the pilot burner 46. This creates natural convection currents and imparts a buoyancy to the flue gases that causes the flue gases to flow toward the upper end 38 of the flue 26. As used herein, “standby convection” means the natural convection within the flue 26 that occurs when the burner 42 is not operating, and that is caused by the water in the tank 14 and/or the flame of the pilot burner 46 warming the flue gases by heat transfer through the flue walls. Unrestricted flow of warm flue gases out of the flue 26 due to standby convection will result in standby heat loss from the water heater 10.
As seen in
As used herein, the term “airflow apparatus” means an apparatus capable of creating airflow in the absence of any opposition to the airflow. The apparatus 54 includes a tubeaxial fan 56 having rotatable blades that create a flow of air parallel to an axis of rotation 58 of the fan blades. The axis of rotation 58 is disposed horizontally, and the fan 56 is exposed to the ambient air surrounding the water heater 10 such that air is drawn into the damper assembly 48 substantially along the axis of rotation 58. The housing 50 defines an annular cavity surrounding the upper end 38 of the flue 26. Circumferential slots or apertures 66 are provided in the annular cavity, and the slots 66 are preferably angled down to direct airflow out of the annular cavity into the upper end 38 of the flue 26. With some modifications to the housing 50, the tubeaxial fan 56 may be replaced with a radial fan.
The fan 56 is preferably turned on during water heater standby, when the burner 42 is not operating. The fan 56 creates a downward pressure or back pressure zone over or within the upper end 38 of the flue 26. The fan 56 and the standby convection currents create countervailing downward and upward pressures, respectively, within the flue 26. In other words, in the absence of the fan 56, standby convection would cause the flue gases to move vertically upward out of the upper end 38 of the flue 26. In the absence of standby convection, the fan 56 would push air downwardly through the flue 26 and out of the air inlets 47.
A gate 68 is pivotably mounted in the housing 50 and is adjustable to restrict and open the air flow path from the fan 56 into the annular cavity of the housing 50. The more open the air flow path, the higher the downward pressure exerted by the fan 56 will be. Therefore, for a single-speed fan 56, the gate 68 setting determines the amount of downward pressure. Alternatively, the fan 56 may be a variable speed fan, in which case the downward pressure may be adjusted by adjusting the speed of the fan 56, and the gate 68 would not be necessary.
In one construction, the airflow apparatus 54 is automatically adjustable to vary the amount of the downward pressure, or airflow, to more effectively counteract the standby convection heat loss of the water heater 10. In order to eliminate or control the standby convection currents, the opposing airflow generated by the airflow apparatus 54 must precisely balance the standby convection currents. If the airflow and the standby convection currents are not balanced, one will overpower the other resulting in heat loss from the flue 26. For example, if the airflow apparatus 54 is providing a greater airflow than the standby convection currents, the airflow apparatus 54 will reverse the direction of the standby convection currents causing heat to be lost out the bottom of the combustion chamber 22. Alternatively, if the airflow apparatus 54 provides a lesser airflow than the standby convection currents, the standby convection currents will bypass the airflow apparatus 54 resulting in heat loss out of the flue 26. Therefore, to substantially eliminate heat loss for a given magnitude of standby convection currents, the magnitude of the airflow generated by the airflow apparatus 54 can be adjusted to precisely balance the standby convection currents.
The magnitude of the standby convection currents is dependent upon the temperature of the water stored within the tank 14. However, this temperature is not constant as the temperature of the water stored in the tank 14 varies during the operation of the water heater 10. For example, the magnitude of the standby convection currents increases when the water stored in the tank 14 is elevated and decreases when the water stored in the tank 14 is lowered. Because the magnitude of the standby convection currents is variable with the temperature of the stored water, the adjustability of the airflow apparatus 54 is preferred in order to adjust the magnitude of the generated airflow to respond to the changes in the magnitude of the standby convection currents to create a substantially stagnant state within the flue 26.
The water heater 10 also comprises a control system for the fan 56. With reference to
In another embodiment of the invention, the airflow apparatus 54 is operated during operation of the burner 42 to create a downdraft and back pressure that can be used to assist or replace the baffle 28. The baffle 28 increases pressure drop and residence time of the products of combustion in the flue 26 where heat is transferred to the water stored in the tank 14. The airflow apparatus 54 can be operated during operation of the burner 42 to create a downdraft and increase the residence time of the products of combustion within the flue, thereby potentially allowing removal of the baffle 28. Replacement of the baffle 28 is preferred because the baffle 28 is a fixed entity that cannot be varied during burner operation, whereas, as discussed above, the airflow apparatus 54 is capable of being adjusted to vary the baffle effect during different phases of burner operation to thereby optimize the burner operation.
In another aspect of the invention, an additional airflow apparatus 146 (
Combustion products produce substances that are harmful to the environment. A catalytic converter 112 is an optional way to reduce the amount of harmful substances released to the environment. The catalytic converter 112 contains platinum, palladium, or some other element that speeds the conversion of unburned hydrocarbons and carbon monoxide into water and carbon dioxide. A catalytic converter 112 does not work effectively until it reaches a certain elevated temperature. In the absence of the elevated temperatures, the infusion of air by the airflow apparatus 146 improves the performance of the catalytic converter 112.
In addition to controlling the activation and deactivation of the airflow apparatus 54, the control system also automatically adjusts the magnitude of the airflow generated by the airflow apparatus 54. As discussed above, the magnitude of the standby convection currents is dependent upon the temperature of the water stored within the tank 14. Therefore, to accurately balance the standby convection currents, the magnitude of the airflow can be controlled based upon the temperature of the stored water. In one construction, the controller 69 adjusts the operation of the airflow apparatus 54 based upon the temperature of the stored water measured by a sensor such as a thermistor 114 (illustrated in broken lines in FIG. 1).
In other constructions, the magnitude of the airflow can also be controlled based on the temperature or velocity of the standby convention currents within the flue 26 because the temperature and rate of flow of the flue gases in the flue 26 during standby is directly proportional to the temperature of the flue wall which is in turn directly proportional to the temperature of the water in the tank 14. Due to this proportional relationship, the controller 69 can adjust the operation of the airflow apparatus 54 based on the temperature of the gases within the flue 26 measured by a sensor, such as temperature switch 74 or a thermistor. Alternatively, the controller 69 can adjust the operation of the airflow apparatus 54 based on the velocity of the standby convection currents within the flue measured by a sensor such as an anemometer 116 (shown in broken lines in FIG. 1).
In yet other constructions, the magnitude of the airflow can be controlled based on the setting of the gas valve 44. The gas valve 44 is adjusted to control the desired set temperature of the water within the tank 14. In light of this relationship, the controller 69 can adjust the operation of the airflow apparatus 54 based on the setting of the gas valve 44 measured by a sensor 118 (shown in broken lines in
It is desirable to use as little energy as possible to drive the fan 56. More specifically, the cost of driving the fan 56 should not exceed the cost savings associated with reducing standby heat loss from the flue 26. One way to reduce the cost of driving the fan 56 is to use a thermo-electric generator 75 (illustrated in broken lines in
The second version may also have similar control and power systems as described above, and may operate under the control of a similar controller 69. The second version may also employ a gate 68 or variable speed fan as described above with respect to the first version. As with the first version, a radial fan may be used in place of the tubeaxial fan 56 with some modifications to the housing 50. Because the fan 56 used in the first and second versions would cause a downward flow of air into the flue 26 in the absence of standby convection flow of flue gases, the first and second versions may be termed “circumferential downdraft” versions.
During operation of the fan 94, air is drawn and pushed by the fan 94 from the second chamber 86, through the first chamber 82, across the upper end 38 of the flue 26, into the turn-around chamber 90, and back into the second chamber 86. The resulting curtain of air flowing across the upper end 38 of the flue 26 substantially prevents the flow of warm flue gases out of the upper end 38 of the flue 26 under the influence of standby convection alone. The third version may also have similar control and power systems as described above, and may operate under the control of a similar controller 69. The radial fan 94 of this version may be replaced with a tubeaxial fan with some modifications to the housing 78.
The first electrodes 98 are connected to a device for providing electrical voltage, such as the illustrated spark plug 102. The spark plug 102 is interconnected with a power supply 106 by way of a conductive wire 110. It is preferable to supply DC power to the first electrodes 98, and the power supply 106 may therefore be a DC power source or an AC power source with a DC converter or an AC signal imposed on a DC power source. The power supply 106 is grounded to the flue wall by way of a grounding wire 114, and therefore a portion of the flue wall acts as a second electrode having a polarity opposite the first electrodes 98. There is therefore a high voltage difference between the first electrodes 98 and the flue wall. A voltage difference of 8-10 kV is preferable, but it may also be higher.
When the power supply 106 is actuated, a positive charge is applied to the first electrodes 98. The positive charge ionizes particles in the air around the first electrodes 98, and the ionized particles are drawn or attracted to the oppositely-charged flue wall. The pointed ends of the first electrodes 98 facilitate the creation of the ionized particles, and the relatively large size of the second electrode (i.e., the flue 26) ensures that the ionized particles will be attracted to the second electrode. The ionized particles are therefore biased for movement toward the flue wall, and bump into flue gas particles in or exiting the upper end 38 of the flue 26. This creates a downward pressure on the flue gases that substantially prevents the flue gases from escaping through the upper end 38 of the flue 26. The fourth version may therefore also be considered a downdraft damper.
Alternatively, the first electrodes 98 may be positioned to the side of the upper end 38 of the flue 26 and a second electrode or electrodes may be positioned on the other side of the upper end 38 such that a cross-flow of ionic wind is created across the upper end 38, resulting in an air curtain similar to that described above in the third version. The fourth version may also have similar control system as described above, and may operate under the control of a similar controller 69. In addition, the magnitude of the airflow generated by the fourth version can be adjusted by varying the magnitude of the voltage difference between the first and second electrodes.
As shown in
When the switch 136 is in a first position, the first electrode 120 is interconnected with the power supply 106 through the electrical circuit 134. The power supply 106 is grounded to the third electrode 128 by way of the grounding wire 114, and therefore the third electrode 128 has a polarity opposite the first electrode 120. There is therefore a high voltage difference between the first electrode 120 and the third electrode 128. A voltage difference of 5-10 kV is preferable, but it may also be higher.
When the power supply 106 is actuated, a positive charge is applied to the first electrode 120. The positive charge ionizes particles in the air around the pins 124 of the first electrode 120, and the ionized particles are drawn or attracted to the oppositely-charged third electrode 128. The pins 124 of the first electrode 120 facilitate the creation of the ionized particles, and the relatively large size of the third electrode 128 ensures that the ionized particles will be attracted to the third electrode 128. The ionized particles are therefore biased for movement toward the third electrode 128 (in the direction of arrows 142), and bump into flue gas particles in or exiting the upper end of the flue 26. This creates a downward pressure on the flue gases substantially preventing the flue gases from escaping through the upper end of the flue 26.
When the switch 136 is in a second position, the second electrode 122 is interconnected with the power supply 106 through the electrical circuit 134. The power supply 106 is grounded to the third electrode 128 by way of the grounding wire 114, and therefore the third electrode 128 has a polarity opposite the second electrode 122. There is therefore a high voltage difference between the second electrode 122 and the third electrode 128. A voltage difference of 5-10 kV is preferable, but it may also be higher.
When the power supply 106 is actuated, a positive charge is applied to the second electrode 122. The positive charge ionizes particles in the air around the pins 126 of the second electrode 122, and the ionized particles are drawn or attracted to the oppositely-charged third electrode 128. The pins 126 of the second electrode 122 facilitate the creation of the ionized particles, and the relatively large size of the third electrode 128 ensures that the ionized particles will be attracted to the third electrode 128. The ionized particles are therefore biased for movement toward the third electrode 128 (in the direction of arrows 144), and bump into flue gas particles in or exiting the upper end of the flue 26. This creates an upward pressure that substantially assists the flue gases to escape the flue 26. In this mode of operation, the ionic airflow device 54 operates as a blower unit.
Efficiency, heat transfer, and the amount of heat energy removed from the products of combustion in the flue 26 can be increased in a combustion system through elements that increase the pressure drop in the flue 26, such as the baffle 28. The baffle 28 increases turbulence, heat transfer area, and residence time, however the increase in pressure drop adversely affects the quality of the combustion unless there is compensation for the restriction caused by the baffle 28. When the second electrode 122 is powered, the ionic airflow device 54 acts as a blower to push or draw gas through the flue 26.
It should be noted that the ionic airflow device 54 may also include a similar control system as described above, and may operate under the control of a similar controller 69. The magnitude of the airflow generated by the ionic airflow device 54 can also be adjusted by varying the magnitude of the voltage difference between the first and third electrodes 120, 128 to adjust the magnitude of the downward airflow and between the second and third electrodes 122, 128 to adjust the magnitude of the upward airflow.
As best shown in
In the construction illustrated in
It should be noted that all versions of the illustrated apparatus for creating airflow are able to substantially prevent the flow of flue gases out of the flue 26 under the influence of standby convection without the use of a physical obstruction (e.g., a conventional solid damper valve) being placed over the upper end 38 of the flue 26.
This application is a continuation of U.S. application Ser. No. 10/410,759 filed Apr. 10, 2003 now U.S. Pat. No. 6,745,724, which is a continuation-in-part of U.S. application Ser. No. 09/920,907 filed Aug. 2, 2001 now U.S. Pat. No. 6,557,501. The entire contents of both prior patent applications are hereby incorporated by reference.
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Number | Date | Country | |
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Child | 10842098 | US |
Number | Date | Country | |
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Parent | 09920907 | Aug 2001 | US |
Child | 10410759 | US |