Patent Application
20090211540
The present invention generally relates to fuel-fired heating appliances and, in a representatively illustrated embodiment thereof, more particularly relates to a fuel-fired water heater having incorporated therein a specially designed draft inducer fan assembly that substantially reduces undesirable heat loss from the water heater during standby periods thereof, thereby desirably increasing the overall energy efficiency of the water heater.
In the area of fuel-fired water heaters a continuing design challenge is the reduction of heat loss from the water heater, which causes an undesirable lessening of the overall energy efficiency of the water heater, during idle or “standby” periods of the water heater. A substantial portion of the standby period heat loss from tank type water heaters occurs at the flue gas discharge area thereof. At such area, convective flows of flue-heated air rising from the water heater, or cold air downflows into the flue, can undesirably reduce the temperature of the tank-stored water, thereby correspondingly diminishing the overall energy efficiency of the water heater.
One conventionally utilized approach to lessening this flue discharge area heat loss is to place a motorized shutoff damper in the flue or in a discharge pipe connected thereto and control the damper in a manner such that it is motor-driven to an open position shortly prior to and during draft inducer fan operation and motor-driven to a closed position during idle periods of the fan corresponding to standby periods of the water heater. However, in various water heater applications, such as in the residential market, this addition of a motorized damper and associated controls to the water heater can increase the production cost of the water heater to an unacceptable extent.
From the foregoing it can be readily seen that a need exists for improved apparatus for lessening the flue gas discharge area heat loss of a fuel-fired water heater during standby periods thereof. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with representatively illustrated embodiments thereof, a specially designed draft inducer fan assembly is provided and is representatively installed on a fuel-fired heating appliance, illustratively a water heater. During firing of the water heater it discharges hot combustion gases through a flue portion of the water heater.
In an exemplary embodiment thereof, the draft inducer fan assembly comprises a housing having an internal wall structure dividing its interior into first and second chambers communicating with one another through an opening in the internal wall structure. The first chamber has an inlet area communicating with the flue to receive hot combustion gases therefrom, the housing further having an outlet area through which the received hot combustion gases may exit the housing. The assembly further comprises a draft inducer fan associated with the housing and operative to sequentially flow the received hot combustion gases from the first chamber through the internal wall structure opening into the second chamber and then outwardly from the housing through the outlet area. A damper portion of the assembly is movable, by fluid pressure force created by operation of the draft inducer fan, from a normally closed position thereof in which the damper substantially prevents gas flow between the housing inlet and outlet areas, to an open position in which the damper permits gas flow between the housing inlet and outlet areas. The damper preclusion of gas flow between the housing inlet and outlet areas substantially prevents convective flow of flue-heated air through the housing during non-firing “standby” periods of the water heater, thereby desirably increasing the overall energy efficiency of the water heater.
Illustratively, the internal wall structure opening is an orifice opening sized and configured to optimize selected operational parameters (such as, for example, draft inducer fan characteristics, flue gas temperature and CO2 percentage) and impede gas flow therethrough from the first chamber into the second chamber as well, and the draft inducer fan has an impeller portion with an inlet communicating with the second chamber. The damper is representatively a gravity damper pivotally carried within the housing for movement between the damper's normally closed and open positions. In one exemplary version thereof the gravity damper, when in its normally closed position, blockingly extends across at least one of the first and second chambers. In another exemplary version thereof the gravity damper, when in its normally closed position, blocks the internal wall structure opening.
In an alternate exemplary embodiment of the draft inducer fan assembly, its housing portion has a dilution air inlet for receiving dilution air from an external source thereof, and the internal wall structure is configured to permit the received dilution air to flow into the second chamber through the wall structure opening when the damper is in its open position. The draft inducer fan has a motor disposed in an interior portion of the housing and is positioned to be impinged upon and cooled by incoming dilution air, the interior portion of the housing communicating with the first chamber therein.
In another exemplary embodiment of the draft inducer fan assembly its internal housing wall structure opening is a first opening, and the internal wall structure further divides the interior of the housing into a third chamber separated from the first chamber and communicating with the second chamber through a second opening in the internal wall structure the housing has a dilution air inlet through which dilution air from an external source thereof may flow into the third chamber for transfer therefrom into the second chamber via the second opening. The damper blocks the first and second openings when the damper is in its normally closed position, and uncovers the first and second openings when the damper is in its open position. The draft inducer fan has a motor disposed within the third chamber and positioned to be impinged upon and cooled by incoming dilution air. In this exemplary embodiment of the draft inducer fan assembly the housing has an internal wall portion that cooperates with the damper, when it is in its normally closed position during standby periods of the water heater, to substantially prevent convective flow of flue-heated air outwardly through either the combustion gas outlet of the housing or its dilution air inlet.
According to other aspects of the invention, in various exemplary embodiments thereof, the draft inducer fan is operative to exert oppositely directed fluid pressure forces on the damper to move it from its normally closed position to its open position thereof, and the assembly may further comprise damper stop structure operative to blockingly and sealingly engage the damper when the damper is in its normally closed position, sealing enhancement apparatus, connected to the damper, for forcing it against the damper stop structure when the damper is in its normally closed position.
Schematically depicted in
During firing of the water heater 10, and entry of combustion air 25 into the combustion chamber 16 through suitable side wall openings thereof, hot combustion products 26 created by burner 18 within combustion chamber 16 are drawn upwardly through the flue 20 by the operation of a draft inducer fan 28 forming a portion of a specially designed draft inducer fan assembly 29 embodying principles of the present invention. Draft inducer fan 28 has a motor 30 and an impeller 32 driven by the motor 30. Disposed above the open upper end of the flue 20, and also forming a portion of the overall draft inducer fan assembly 29 is a fan assembly housing 34 which is vertically divided by an internal horizontal plate 36 into upper and lower chambers 38 and 40.
With reference now to
During firing of the water heater 10, and operation of the draft inducer fan 28, the fan 28 causes the gravity damper 42 to pivot in a clockwise direction from its solid line closed position to its dotted line open position to thereby communicate the subchambers 38a and 38b and also communicate the subchambers 40a and 40b as shown. It should be noted that the fan 28 exerts a “push-pull” combination of rotational forces on the damper 42, with the inlet side of the fan creating a clockwise rotational “pulling” force on a lower portion 42a of the damper blade, and the outlet side of the fan creating a clockwise rotational “pushing” force on an upper portion 42b the damper blade. As compared to an installation in which the damper 42 extended across only one of the chambers 38,40 instead of both of them as shown, this permits the damper 42 to have a larger blade area and thus an advantageously larger overall available peripheral sealing area. Additionally, the “push-pull” torque exerted on the damper 42 enables it to be opened to a wider angle, and overcome higher frictional forces thereon. With the damper 42 opened by fan-created flow forces, combustion gases 26 exiting the open upper end of the flue 22 sequentially pass through the subchambers 40b, 40a, 38a and 38b before being discharged from the fan assembly housing 34 via the flue gas outlet opening 44 therein.
When firing and fan operations cease, the gravity damper 42 automatically pivots back to its normal solid line position to thereby seal off the interior of the housing 34, in a manner subsequently described herein, to substantially hinder upward convection heat flow from rising therethrough or cold air from falling downwardly therethrough. Because of the unique configuration and operation of the draft inducer fan assembly 29 of the illustrated water heater 10, the overall energy efficiency of the water heater is substantially improved by reducing heat loss therefrom during standby periods thereof. Water heater 10 is representatively of a “non-dilution” type, meaning that the combustion gases 26 are discharged therefrom without first mixing the combustion gases 26 with a flow of cooling or “dilution” air.
With reference to
A second exemplary embodiment 292 of the previously described draft inducer fan assembly 29 is schematically shown in
The first difference between the fan assemblies 29 and 292 is that, in the fan assembly 292, during firing of the water heater 10, and operation of the draft inducer fan 28, ambient dilution air 61 is drawn into the housing subchamber 40a, via dilution air openings 63 in the side wall of the housing 34, for mixing with and cooling of the hot combustion products 26 entering the subchamber 38a via the opening 43. The second difference between the fan assemblies 29 and 292 is that in the assembly 292 the pressure tap 46 is relocated as shown in
With reference now to
As previously mentioned, the damper 42 is a gravity type damper, with the weight of the damper being balanced in a manner such that it exerts a sealing force on the gasket material 66 when the damper is in its closed position. Such sealing force may be increased, using sealing enhancement apparatus as will now be described, by drivingly coupling a small electric closure motor 72 to the damper 42 as schematically depicted in
Alternatively, using another sealing enhancement apparatus embodiment as schematically shown in
As can be seen from the foregoing, using principles of the present invention undesirable heat loss from the water heater 10 during standby periods thereof is substantially reduced by the damper stop/gasket structure 62 sealingly contacted by the damper 42 in it closed position.
A third exemplary embodiment 293 of the previously described draft inducer fan assembly 29 is schematically shown in
The difference between the fan assemblies 29 and 293 is that in the assembly 293 an additional damper stop/gasket structure 62 is operatively installed in the upper chamber 38 in a manner such that when the damper 42 is in its closed position its lower portion 42a sealingly engages the gasket material on the lower damper stop/gasket structure 62, and its upper portion 42b sealingly engages the gasket material on the upper damper stop/gasket structure 62. Thus, during standby periods of the water heater 10 undesirable upward convective heat flow from the flue through the housing 34, and downward flow of cold air therethrough, are substantially prevented by two separate seal structures operatively associated with the fan pressure-driven oversized damper 42. As in the case of the previously described fan assembly 29, the closing and sealing force of the gravity damper 42 in the assembly 293 may be augmented by the addition thereto of the previously discussed sealing enhancement structure shown in
Schematically depicted in
A horizontal dividing wall 100 within the interior of the assembly housing 94 vertically divides a left interior portion thereof into a flue gas receiving chamber 102 disposed beneath the dividing wall 100, and a mixing chamber 104 disposed above the dividing wall 100 and bounded on its right side by the fan impeller housing 96. Chamber 102 communicates with the chamber 104 via a transfer opening 106 in the dividing wall 100, and chamber 104 communicates with the interior of the fan impeller housing 96 via an inlet opening 108 therein. Impeller housing 96 has a top side outlet 110 that is coupled to a suitable discharge conduit 112. A gravity damper 114 is pivotally connected, as at 115, to the dividing wall 100, and is shown in its raised, open position. In its normally closed position the damper 114 falls to a horizontal position in which it overlies and blocks the transfer opening 106. The flue gas receiving chamber 102 communicates with the dilution air chamber 98 via a passage 116 beneath the lower side of the fan impeller housing 96.
With continuing reference to
A first portion of the incoming air 124 flows through the upper outlet branch 120 into the chamber 98 as dilution air 128 which flows externally around and cools the fan motor 30 within the chamber 98. The dilution air 128 then passes into the chamber 104, via the passage 116, and then enters the chamber 104 through the transfer opening 106. Next, together with combustion gases 26 within the chamber 104, the dilution air 128 enters the fan impeller housing 96 wherein it cools the combustion gases 26 such that they exit the fan impeller housing 96 as cooled combustion gases 130. The remainder of the incoming ambient air 124 continues downwardly through the air supply conduit 118 as combustion air 25 which flows into the combustion chamber 16 via the lower outlet branch 122 of the air supply conduit 118.
When firing of the water heater 10 ceases, and the draft inducer fan 28 then shuts down, the gravity damper 114 downwardly pivots to its normally closed position in which it blocks the transfer opening 106, thereby preventing convective upflows from the flue 20 from escaping from the system via the fan housing 96 during standby periods of the water heater 10 and desirably reducing standby heat losses therefrom. Such automatic closure of the damper 114, which was previously opened by fluid forces of the fan 28, also blocks further flow of ambient air 124 through the fan assembly 294 and the combustion chamber 16. As with the previously described exemplary embodiments of the draft inducer fan assembly, the fan assembly 294 is provided with the indicated pressure taps 46,48 which may be utilized to sense the pressure differential between the chambers102 and 104 as previously described in conjunction with the chambers 38a,40a shown in
A fifth exemplary draft inducer fan assembly embodiment 295 is schematically depicted in
A first difference between the draft inducer fan assemblies 294 and 295 is that in the assembly 295 the chambers 102 and 98 are separated from one another by a vertical dividing wall 132 extending downwardly from the horizontal dividing wall 100 to the top end of the water heater 10 and horizontally disposed between the open upper end of the flue 20 and a lower side portion of the fan impeller housing 96. A second difference between the draft inducer fan assemblies 294 and 295 is that in the assembly 295 an additional transfer opening 134 is formed in the horizontal dividing wall 100 between the vertical dividing wall 132 and the fan impeller housing 96. Chamber 102 communicates with the chamber 104 through the transfer opening 106, and chamber 98 communicates with the chamber 104 through the transfer opening 134. A third difference between the draft inducer fan assemblies 294 and 295 is that in the assembly 295 the gravity damper 114 is sized in a manner such that when it is downwardly pivoted to its normally closed position it blocks both of the transfer openings 106 and 134.
With continuing reference to
During standby periods of the water heater 10 the closed damper 114 prevents convective heat migration from the flue 20 into the chamber 104 and then outwardly through the draft inducer fan 28, and the vertical dividing wall 132 prevents such convective heat migration from the flue 20 into and outwardly through the air supply conduit 118 via the dilution air chamber 98. The use of separate transfer openings 106,134 to permit inflows of combustion gases 26 and dilution air 128, respectively, into the chamber 104 during operation of the draft inducer fan 28 and firing of the water heater 10 permits the flow rate of such inflows to be separately regulated by appropriately sizing the relative areas of the transfer openings 106 and 134.
A sixth exemplary draft inducer fan assembly embodiment 296 is schematically depicted in
In the draft inducer fan assembly 296, the air supply conduit 128 shown in
A seventh exemplary draft inducer fan assembly embodiment 297 is schematically depicted in
In the draft inducer fan assembly 297, the air supply conduit 128 shown in
As can be seen from the foregoing, each of the exemplary draft inducer fan assemblies 29-297 desirably limits the standby heat loss of its associated water heater 10 using a shutoff damper structure driven by fluid pressure generated by a draft inducer fan. While principles of the present invention have been representatively incorporated in a fuel-fired water heater, those of skill in this particular art will readily appreciate that such principles may also be incorporated to advantage in other types of fuel-fired heating appliances such as, for example, boilers and furnaces.
The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.
