Flue pipe control

Information

  • Patent Grant
  • 6584940
  • Patent Number
    6,584,940
  • Date Filed
    Wednesday, January 9, 2002
    23 years ago
  • Date Issued
    Tuesday, July 1, 2003
    21 years ago
Abstract
An improved flue pipe construction particularly adapted for a fuel fired water heater is disclosed which serves to reduce or minimize heat loss when the water heater is in a standby mode. The flue pipe construction comprises inner and outer concentric flue pipes which define an air space therebetween and one or more valve arrangements associated therewith to selectively restrict air flow through such air space. The valve arrangements include a thermally responsive actuator operative to open and close the valve member in response to heat generated by firing of the burner assembly without the need for any external power supply or interlocks.
Description




BACKGROUND AND SUMMARY OF THE INVENTION




The present invention relates generally to an improved flue pipe assembly particularly adapted for improving the efficiency of hot water heaters and more specifically to such apparatus which is designed to inhibit heat loss from the hot water within the water heater storage tank of a water heater.




Conventional gas fired water heaters in use today incorporate a center flue pipe which extends upwardly through the water storage tank and which is generally cylindrical in shape. Hot combustion gases from a gas fired burner assembly positioned below the water storage tank are directed upwardly through this center flue pipe which serves to transfer heat therefrom to the stored water surrounding the outer surface of the flue. In many cases the flue will include a device operative to induce turbulence into the flowing hot gases to improve heat transfer to the surrounding water. Such devices are commonly referred to as baffles and typically comprise an elongated zig zag or spiral shaped member suspended in the center of the flue. The combustion gases typically exit the top of the water heater and are directed out of the building within which the water heater is located via a vent or smoke pipe.




When the burner assembly is not firing, ambient air will flow through this flue pipe and cool the heated water in the storage tank thus reducing the overall efficiency of the water heater. In recent years increasing emphasis has been placed on improving the ability of such water heaters to efficiently heat the stored water and to reduce the heat loss therefrom when in a standby mode (i.e. burner assembly in an off condition) to thereby improve the overall operating efficiency.




Various types of insulation have been added to the outer surface of the water storage tank which have greatly reduced heat loss through these outer walls. Additionally, various types of damper arrangements have been incorporated into the external vent pipe to reduce air circulation through the flue pipe during standby periods. However, these damper arrangements generally require a power supply for operating same as well as safety interlocks to insure they are opened before the burner is fired. In some cases these devices may incorporate an arrangement that insures they are in an open position in the event of a power supply failure. Nevertheless, such devices are complex and costly to manufacture and because they require an external power supply, they also result in increased installation costs. Further, gas fired water heater manufacturers generally prefer to avoid the need for an external power supply for operation of their products. Additionally, because these devices are commonly incorporated in the external vent pipe and the internal flue pipe of the water heater is open to the surrounding environment via the vent hood, such dampers are not totally effective in preventing air flow through the flue pipe.




The present invention, however, overcomes the problems associated with the prior art devices by providing an effective insulating barrier between the wall of the flue and any air flow through the flue pipe thereby greatly reducing heat loss when the heater is in the standby mode while still ensuring good effective heat transfer through the flue pipe to the water when the water heater is firing. The primary objective of the present invention is to provide an arrangement which is highly efficient in transferring heat from the combustion gases to the water when the burner is firing but minimizes heat transfer from the water to gases flowing through the flue pipe when the water heater is in a standby mode.




In one embodiment an open cylindrical member of a diameter less than that of the flue pipe is positioned concentrically within the flue pipe and includes a plurality of openings in the sidewalls thereof with radially inwardly extending flanges positioned above the respective openings. A self powered thermally responsive valve assembly operates to selectively open and close the annular space between the inner cylindrical member and the flue pipe at the upper end thereof in response to firing of the burner assembly. Because the center of the cylindrical member is continuously in open communication with the water heater venting system there is no need for costly and complex interlocks with the burner control system. Further, the system does not require any external power supply for operation thus avoiding any increased installation expenses by the end user of the water heater.




In another embodiment, a similar valve assembly is also provided to open and close off the annular space between the cylindrical liner and flue pipe at the lower end thereof to further isolate the air volume in this annular space from convection air currents.




Each of these embodiments offer the advantage of effectively restricting heat loss from the heated water in the tank to air currents flowing through the center of the water heater while in a standby mode and yet also ensures good heat transfer to the tank water from the combustion gases when the burner is firing. For each case the path from burner assembly to the external venting system is continuously open thus eliminating the need for any complicated safety interlocks with the burner controls. Further because the system is self activating, there is no need for any external or auxiliary power supply which would increase installation costs or require periodic maintenance.











Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.




BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of a conventional gas fired hot water heater with portions thereof broken away;





FIGS. 2 and 3

are schematic views of a portion of a flue pipe assembly for a water heater illustrating a preferred embodiment of the present invention in a standby mode and firing mode respectively;





FIG. 4

is a fragmentary section view of an upper portion of a water heater incorporating the embodiment of

FIGS. 2 and 3

and showing the valving arrangement utilized therein in a closed position, all in accordance with the present invention;





FIG. 5

is viewed similar to that of

FIG. 4

but showing the valving arrangement in an open position;





FIG. 6

is a plan view of the valving arrangement shown in

FIG. 4

;





FIG. 7

is a view of the valve assembly of

FIG. 6

as seen looking in the direction of arrow


7


and with portions of the water heater shown in section;





FIG. 8

is a plan view of one of the valve members incorporated in the valving arrangement of

FIG. 6

;





FIGS. 9 and 10

are elevational views of the valve member of

FIG. 8

, the respective views being taken at right angles to each other;





FIGS. 11

,


12


and


13


are side, plan and front views respectively of an actuator bracket forming a part of the valve assembly of

FIG. 6

;





FIGS. 14 and 15

are side and plan views of a mounting bracket forming a part of the valve assembly of

FIG. 6

;





FIG. 16

is a view similar to that of

FIG. 4

but showing an alternative valving assembly in accordance with the present invention;





FIG. 17

is a plan view of the valving assembly of

FIG. 16

;





FIG. 18

is a view similar to that of

FIG. 16

but showing the valving assembly rotated by 90°;





FIG. 19

is a view similar to that of

FIG. 2

but showing the inclusion of a second thermally actuated valve at the lower ends of the inner and outer flue pipes;





FIGS. 20 and 21

are fragmentary sectional views of another valving arrangement in accordance with the present invention with the valving arrangement shown in open and closed positions respectively;





FIG. 22

is a section view of the embodiment shown in

FIGS. 20 and 21

, the section being taken along lines


22





22


of

FIG. 21

;





FIG. 23

is an elevational view of a bimetallic valving member forming a part of the embodiment of

FIGS. 20 and 21

; and





FIGS. 24 and 25

are enlarged fragmentary section views of yet another embodiment of the present invention with the valving shown in closed and open positions respectively.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring now to the drawings and more specifically to

FIG. 1

, there is shown a conventional gas fired water heater indicated generally at


10


. Water heater


10


includes an outer housing


12


within which is disposed a water storage tank


14


surrounded by a layer of insulation


16


and a gas fired burner assembly


18


.




Water storage tank


14


has a generally elongated cylindrical shape, is positioned above burner assembly


18


and includes an outer shell


20


, a generally conically shaped hood portion


22


sealingly secured to a lower portion of shell


20


and overlying the burner assembly and an axially elongated flue pipe


24


which is sealingly secured to hood portion


22


at its lower end and which projects outwardly through outer housing


12


at the upper end


26


thereof. Flue pipe


24


is connected to a smoke or vent pipe not shown via a draft hood


28


. In operation, combustion gases generated by the firing of burner assembly


18


are directed upwardly through flue pipe


24


via hood


22


and serve to transfer heat to the water contained within storage tank


14


. In many cases, a spirally shaped or zig zag baffle member


30


is supported within flue pipe


24


and serves to create a mixing of the combustion goods as they flow upwardly through flue pipe


24


to improve heat transfer to the water by reducing any thermal boundary layer that may form along the sidewalls of flue pipe


24


.




Water heater


10


also includes suitable fittings


32


and


34


for connection to a supply of water and a water distribution system with water inlet


32


being provided with a dip tube


36


which serves to direct the inflow of cold water to the bottom of the tank


14


.




Additionally, water heater


10


includes a control assembly


37


for controlling the supply of gas to burner assembly


18


in response to the sensed temperature of the water within tank


14


. A drain spigot and valve assembly


39


is also provided for enabling the user of the water heater to periodically flush debris from the bottom of tank


14


as well as to drain same should this be desired.




As thus far described, water heater


10


is of a construction typical for gas water heaters currently in use.




As noted above, such water heaters are relatively efficient in transferring heat from the combustion process to the water within tank


14


. Additionally, great care has been taken in the design of such systems to reduce heat loss to the environment through the outer walls of the tank


14


. Such efforts include surrounding the outer wall


20


with insulating materials and minimizing the size and number of penetrations through such insulating material


16


. However, the flue pipe


24


is in continuous open communication with the environment at both the upper and lower ends thereof. As a result, when the water heater is in the standby mode, air within flue pipe


24


will absorb heat from the hot water in tank


14


via flue pipe


24


and create a convection draft therethrough resulting in more frequent firing of the burning assembly to maintain the desired water temperature. The heat loss occasioned by this convection draft may result in a significant reduction in the overall operating efficiency of the water heater.




In order to minimize this convection draft heat loss while maintaining or perhaps even improving heat transfer to the water from the combustion gases, the present invention incorporates a modified flue pipe assembly


38


which, as shown in

FIGS. 2 and 3

, includes an elongated generally cylindrically shaped outer flue pipe


40


and a smaller diameter inner flue pipe


42


of substantially equal length. Inner flue pipe


42


is preferably supported concentrically within outer flue pipe


40


so as to define an annular space


41


therebetween and includes a plurality of circumferentially and axially spaced openings


44


therein. A louver


46


extends generally radially inwardly immediately above each of the openings


44


and is angled axially somewhat in a downward direction toward burner assembly


18


. Annular space


41


is in open communication with the burner assembly


18


at its lower end and is closed off at the upper end of flue pipes


40


and


42


by a temperature responsive valve assembly


48


. Valve assembly


48


includes a thermally responsive actuator


50


centrally positioned over the open upper end of inner flue pipe


42


and oppositely moveable valves


52


and


54


. When burner assembly is in a standby mode (i.e. not firing), valve assembly


48


will be in a closed position effectively sealing off the upper end of the annular space


41


between inner and outer flue pipes


42


and


40


. As a result, annular chamber


41


will effectively create a dead air space thereby insulating outer flue pipe


40


and the heated water radially outwardly thereof from air circulation through inner flue pipe


42


. When burner assembly


18


is fired, the hot combustion gas will initially flow upwardly through inner flue pipe


42


and heat actuator


50


of valve assembly


48


which will operate to move valve members


52


and


54


into an open position thereby opening the upper end of chamber


41


and allowing flow of hot combustion gases into intimate contact with the inner surface of outer flue pipe


40


. Heat from the combustion gases will then be transferred through outer flue pipe


40


to heat the water.




It is believed that the combination of the openings


44


in inner flue pipe


42


and the angled louvers


46


will cooperate to enhance flow of hot combustion gases into annular chamber


41


thereby enhancing heat transfer to the surrounding water when valve assembly


48


is in an open position. However, when the water heater is in a standby mode, it is believed that inner pipe


42


with louvers


46


will assist in reducing air circulation into and out of annular chamber


41


as well as reducing the air flow velocity therethrough thus enhancing the insulating effort of the “dead” air space provided between the two flue pipes. It should also be noted that because valve assembly


48


only closes off annular chamber


41


, the entire area within inner flue pipe


42


is continuously open, to the vent system. Thus there is no need to provide any interlocks with the controls for burner assembly


18


because should valve assembly


48


fail to open on firing of burner


18


, the hot combustion gases will still be vented via inner flue pipe


42


. It should be noted that modeling analysis has indicated that the use of an inner flue pipe


42


without the inclusion of a valve assembly reduces the fluid flow velocity in the gap between the inner and outer flue pipes and thus reduces standby heat loss even without the inclusion of valve assembly


48


.




Thermally actuated valve assembly


48


is shown in greater detail and will be described with reference to

FIGS. 4 through 15

. With reference to

FIGS. 4 and 5

, valve assembly


48


includes a pair of valve members


52


and


54


pivotably supported on an upper surface


56


of hot water heater


58


via brackets


60


and


62


and suitable support members


64


and


66


. Additionally thermal actuator


50


extends between valve


52


and


54


and includes a pair of actuator brackets


68


and


70


and an interconnecting rod


72


extending therebetween. A pair of compression springs


74


and


76


are provided on rod


72


adjacent opposite ends thereof and serve to bias brackets


68


and


70


toward each other. A center thermally responsive opening member


78


is also provided on rod


72


positioned between brackets


68


and


70


and acting in opposition to respective springs


74


and


76


.




Valve members


52


and


54


are substantially identical in construction and hence only valve member


52


will be described in detail with corresponding portions of valve member


54


being indicated by the same reference numbers primed. As best seen with reference to

FIGS. 6-10

, valve member


52


includes a substantially planar semicircular portion


80


from which a supporting flange


82


extends upwardly from a location substantially equidistant from the opposite ends thereof. Supporting flange


82


includes an elongated center portion


84


having a laterally extending slot


86


positioned adjacent the upper end thereof and a pair of laterally spaced outwardly extending pivot flanges


88


,


90


adjacent the planar portion


80


. Aligned openings


94


are provided in respective pivot flanges


88


and


90


and are sized to receive a pivot pin


96


by which valve member


52


may be pivotably supported via bracket


60


and support member


64


. A suitable heat resistant resilient sealing material


98


is suitably secured to lower surface


100


of planar portion


80


and is suitably sized so as to matably engage the upper edges of inner and outer flue pipes


40


and


42


when valve member


52


is in a closed position.




Actuator bracket


68


is also substantially identical to actuator bracket


70


and hence only bracket


68


will be described, it being understood that corresponding portions of bracket


70


will be indicated by the same reference numbers primed.




As best seen with reference to

FIGS. 11

,


12


and


13


, actuator bracket


68


includes an elongated substantially planar portion


102


having an upstanding flange portion


104


provided at one end thereof. A reduced width tab portion


106


is provided at the opposite end of planar portion


102


from flange


104


and is adapted to be received within slot


86


of valve member


52


. Preferably, tab


106


will have a width and thickness so as to be relatively loosely fitted within slot


86


. Flange portion


104


includes an opening


108


therein suitably sized to slidingly receive rod


72


therethrough.




Bracket


60


is substantially identical to bracket


62


and hence only bracket


60


will be described in detail it being understood that corresponding portions of bracket


62


will be indicated by the same reference numbers primed. As shown in

FIGS. 14 and 15

, bracket


60


is generally rectangular in shape and includes an upstanding portion


110


through which bore


112


extends. Bore


112


is suitably sized to receive pivot pin


96


so as to thereby enable valve member


52


to be pivotably supported therefrom in cantilevered relationship. As noted above, bracket


60


is suitably fixedly supported on water heater


10


by a suitable support member


64


affixed to the upper surface


56


of water heater


10


. Alternatively, bracket


60


may be directly secured to water heater


10


if desired.




Referring once again to

FIGS. 4 through 7

, valve members


52


and


54


are pivotably supported with opposite ends


114


,


116


and


114


′,


116


′ of semicircular portion


80


in opposed relationship and sealing material


98


,


98


′ provided thereon in sealing engagement with the upper end of flue pipes


40


and


42


. Respective tabs


106


,


106


′ of actuating brackets


68


and


70


are loosely received within respective slots


86


,


86


′ of valve members


52


and


54


and interconnecting rod


70


extends through openings


108


,


108


′ of upstanding flange portions


104


,


104


′. As noted above, flange portions


104


,


104


′ are acted on opposite sides by respective compression springs


74


and


76


and thermally responsive opening member


78


.




In operation, as thermally responsive opening member


78


is heated by combustion gas flowing upwardly through inner flue pipe


42


, it will operate to exert oppositely directed forces on respective actuator brackets


68


and


70


thereby causing them to overcome the biasing forces of springs


74


and


76


and to move outwardly along rod


72


. As actuator brackets


68


and


70


are biased outwardly along rod


72


, the opposite ends thereof will operate against flange portion


82


,


82


′ thereby causing respective valve members


52


and


54


to pivot about respective rods


96


and move sealing members


100


,


100


′ out of engagement with flue pipes


40


,


42


and open the upper end of chamber


41


. Thereafter, the hot combustion gases will be directed through openings


44


into intimate heat transfer relationship with outer flue pipe


40


to heat the water within tank


14


and then exhausted via the open upper space between flue pipes


40


,


42


.




Once the water temperature has reached the preset temperature, controller


37


will shut down burner assembly


18


thereby discontinuing the supply of heat to thermally responsive opening member


78


and allowing same to cool. As thermally responsive opening member


78


cools and contracts, the biasing action of springs


74


and


76


will cause actuator brackets


68


and


70


to move along rod


72


toward each other thereby allowing valve members


52


and


54


to move into a closed position as shown in

FIG. 4

in which convection draft air flow through annular chamber


41


is effectively resisted. The thus confined “dead” air space will then serve as an insulating layer against heat loss to air that may circulate through inner flue pipe


42


.




In a presently preferred embodiment, it is contemplated that thermally responsive opening member


78


will be in the form of a helical coiled spring fabricated from a shape memory alloy material. Such materials are known in the art and exhibit the ability to rapidly change from a given shape to a “remembered” shape upon being heated to a predetermined temperature and to return to a deformed shape upon cooling below the predetermined temperature. In the particular embodiment described, the “remembered” shape would be a longer helical coil and the “deformed shaped” would be a shortened helical coil.




It should be noted that because thermally responsive opening member


78


is centrally disposed above the open inner flue pipe


42


it will be immediately subjected to heating by the combustion gases upon firing of burner assembly


18


and will thus be quickly responsive to same to open valve members


52


and


54


. Further, because the center of inner flue pipe


42


is continuously open to the vent system, combustion gas will always be free to flow to and through the associated vent system and exhausted to the outside even in the event valve assembly


48


should fail to open. Thus, it is not necessary to incorporate any interlock system between valve assembly


48


and control


37


although this could be done if desired. It should also be noted that while a shape memory alloy material is presently preferred, other types of thermally responsive opening devices could be substituted therefor, the only requirements being that the device be capable of generating a sufficient force to move valve members from a closed position to an open position in response to an increase in temperature thereof.




Referring now to

FIGS. 16-18

, there is shown another embodiment of a valve assembly


118


in accordance with the present invention. In this embodiment, valve assembly


118


comprises a valve member


120


in the form of an annular ring having an open center portion


122


aligned with the open center of inner flue pipe


42


and a pair of diametrically opposed radially outwardly projecting extensions


124


,


126


. A suitable heat resilient sealing material


128


is secured to the lower surface


130


of valve member


120


and serves to sealingly engage the upper ends of inner and outer flue pipes


40


,


42


in the same manner as material


98


when valve member


120


is in a closed position.




In order to retain valve member


120


in position with respect to inner and outer flue pipes


40


and


42


, as well as to guide opening and closing movement thereof, an elongated generally U-shaped guide member


132


is provided which includes a pair of leg portions


134


,


136


extending through suitable openings provided in respective extensions


124


,


126


with the terminal ends thereof being secured to upper surface


138


of hot water heater


10


′.




An actuator assembly


140


is also provided which includes a second generally U-shaped elongated member


142


having a pair of leg portions


144


,


146


and an interconnecting portion


148


. As shown, member


142


is positioned substantially perpendicular to member


132


with interconnecting portion


148


being affixed to member


132


at the point of intersection. Legs


144


and


146


each project through valve member


120


and are secured to outer flue pipe


40


. A pair of thermally responsive opening members


150


,


152


are provided on leg members


144


,


146


each having one end fixedly secured to an annular flange member


154


,


156


each of which are in turn fixedly secured to respective leg portions


144




146


adjacent the upper end thereof. The opposite ends of thermally responsive opening member


150


,


152


are secured to the upper surface


158


of valve member


120


.




In operation, when burner assembly


18


is fired, the hot combustion gas flowing through inner flue pipe


42


will operate to heat thermally responsive opening members


150


,


152


. Once the temperature of thermally responsive opening member


150


,


152


exceeds a predetermined temperature, they will contract thereby lifting valve member


120


upwardly away from inner and outer flue pipes


40


,


42


and allowing the hot combustion gases to flow through annular chamber


41


in the same manner as described with respect to valve assembly


48


. When burner assembly


18


is shut down, thermally responsive opening members


150


,


152


will cool and thus return to their elongated state thereby moving valve member into a closed position as shown.




Preferably, as with valve assembly


48


, thermally responsive opening members


150


,


152


will be in the form of helical coils of shape memory alloy material although in this embodiment, the “remembered” hot shape will be a shorter helical coil. Again, it should be noted that other devices having the ability to move valve member


120


upwardly in response to an increased temperature may be substituted therefor.




While the above embodiments have been described with the use of only a single thermally responsive valve assembly positioned at the upper end of flue pipes


40


,


42


, it may in some applications be desirable to incorporate a second valve assembly at the lower end of flue pipes


40


,


42


. Such an embodiment is illustrated schematically in

FIG. 19

in which both upper


160


and lower


162


valve assemblies are incorporated to close off annular space


41


between inner and outer flue pipes


40


,


42


during the standby mode. Either valve assemblies


48


or


118


may be used for either of valve assemblies


160


,


162


or alternatively one or both may be of the type described below with reference to

FIGS. 20 and 21

. Further, if desired, a single valve assembly may be provided at the lower end of flue pipes


40


,


42


.





FIGS. 20-23

illustrate yet another embodiment of the present invention. In this embodiment, a valve assembly


164


is secured to the upper end of inner flue pipe


166


and operates to selectively open and close off the annular area


168


between inner and outer flue pipes


166


and


170


. Valve assembly


164


comprises first and second substantially identical elongated bimetal strips


172


,


174


each of which includes a plurality of upwardly projecting fingers


176


separated by notches


178


extending laterally inwardly from the upper edge thereof. As shown, the lower edges of first and second strips


172


and


174


are secured to the upper edge of inner flue pipe


166


in any suitable manner such as by a plurality of circumferentially spaced rivets


180


. Preferably, second strip


174


is circumferentially offset from first strip


172


such that fingers


176


of one strip overlie notches


178


of the other strip. Strips


172


and


174


are fabricated from a suitable bimetal material having the ability to resist the by-products of combustion contained in the combustion gases passing through flues


166


,


170


.




When the water heater is in a standby mode, the ends of fingers


176


will extend axially and radially outwardly into engagement with outer flue


170


. The overlapping arrangement of the respective fingers and notches


176


,


178


will enable the bimetal strips to effectively close off the upper end of annular space


168


thereby resisting cooling convection gas currents and reducing the resulting standby heat loss. When the water heater burner assembly is actuated, the hot combustion gases traveling through the flue pipe will heat respective first and second bimetal strips


172


,


174


and, as a result of the differential in the coefficient of expansion between the layers of the bimetal strips, fingers


176


will move radially inwardly to the position shown in

FIG. 21

thereby opening the upper end of annular space


168


thus enabling the flow of gases therethrough.




Once the water has been heated to the desired temperature, the water heater burner assembly will be shut down and bimetal strips


172


,


174


will cool thus causing fingers to return to the closed position as shown in FIG.


20


. It should be noted that strips


172


and


174


may alternatively be fabricated from a shape memory alloy if desired.




Referring now to

FIG. 24

, a further embodiment of the present invention is shown. This embodiment is similar to that of

FIGS. 2 and 3

with the exception that fixed louvers


46


have been replaced with thermally actuable louvers


182


. As shown, louvers


182


are preferably fabricated from a suitable bimetal material and are secured to inner flue pipe


184


in overlying relationship to respective openings


186


provided therein thus closing off communication between annular space


188


disposed between inner and outer flue pipes


184


,


190


and the open interior space


192


defined by inner flue pipe


184


when the water heater is in a standby mode. When the burner assembly fires, the hot combustion gases traveling through space


192


will heat bimetal valves


182


in response to which they will move into a position similar to that of louvers


46


shown in

FIGS. 2 and 3

. Upon a return of the burner assembly to a standby mode, bimetal valves


182


will cool and return to their respective closed positions as shown in FIG.


24


.




It should be noted that while it is believed preferable to utilize one of the valve assemblies described above to close off the upper and/or lower openings between inner and outer flue pipes


184


and


190


in combination with valves


182


, valve assemblies


182


could be used alone although it is believed the resulting improvements in operating efficiency for the water heater will not be as great. Also, as mentioned above, valves


182


may be fabricated from a shape memory alloy in lieu of a bimetal material if desired.




It should be noted that with respect to all of the embodiments above, the diameter of inner flue pipe


42


,


166


,


184


must be selected relative to the size of the burner assembly so as to provide adequate flue area for proper venting of the combustion gases. Further, the number and positioning of the louvers should be such that they do not prevent the proper venting of the combustion gases even when the valve assembly is in a closed position. Also the number and positioning of the openings


44


,


186


as well as the shape and angulation of the louvers and the spacing between the inner and outer flue pipes


40


,


42


;


166


,


170


;


184


,


190


will be selected so as to maximize the heat transfer to the surrounding water when burner assembly


18


is being fired and yet minimize the cooling effect of convection drafts on the heated water while the water heater is in a standby mode.




As may now be appreciated, the present invention provides a relatively inexpensive easily fabricated flue pipe assembly which is highly effective in reducing standby heat losses for water heaters. Because the present invention enables full flow of combustion gas even when the valve assemblies are in a closed position, no interlocks are required. Further, the present invention achieves these objectives without requiring any additional external connections upon installation of the water heater such as for auxiliary power.




While it will be apparent that the preferred embodiment of the invention disclosed is well calculated to provide the advantages and features above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.



Claims
  • 1. An improved flue pipe assembly for selectively promoting and inhibiting heat transfer between a fluid flowing through the interior of a flue pipe and a fluid surrounding the exterior of said flue pipe, said flue pipe assembly comprising:a generally elongated flue pipe having an inner surface and an outer surface, said flue pipe being adapted to conduct a flow of a first fluid through the interior thereof, and a second fluid surrounding said outer surface and being in heat transfer relationship therewith; and apparatus within said flue pipe for selectively promoting and inhibiting heat transfer between said first fluid and said second fluid through said flue pipe.
  • 2. A flue pipe assembly as set forth in claim 1 wherein said apparatus operates to promote heat transfer from said first fluid to said second fluid and to inhibit heat transfer from said second fluid to said first fluid.
  • 3. A flue pipe assembly as set forth in claim 1 wherein said apparatus is operative to provide an insulating layer along said inner surface when said first fluid is below a predetermined temperature to inhibit heat transfer from said second fluid to said first fluid.
  • 4. A flue pipe assembly as set forth in claim 3 wherein said insulating layer comprises a substantially non-flowing layer of said first fluid.
  • 5. A flue pipe assembly as set forth in claim 4 wherein said apparatus includes an inner flue pipe supported within said elongated flue pipe and spaced therefrom to define an annular flow path therebetween and a valve assembly selectively operable to allow and inhibit flow of said first fluid through said annular flow path.
  • 6. A flue pipe assembly as set forth in claim 5 wherein said valve assembly is self powered.
  • 7. A flue pipe assembly as set forth in claim 1 wherein said valve assembly is thermally actuated from a closed position in which flow of said first fluid through said annular flow path is inhibited to an open position to allow flow of said first fluid through said annular flow path.
  • 8. A flue pipe assembly as set forth in claim 7 wherein said valve assembly is actuated to said open position in response to an increase in the temperature of said first fluid.
  • 9. A flue pipe assembly as set forth in claim 8 wherein said valve assembly is located at one end of said flue assembly.
  • 10. An improved flue pipe assembly for effecting heat transfer from a first fluid flowing through an interior of said flue pipe assembly to a second fluid surrounding an outer surface of said flue pipe assembly and for resisting heat transfer from said second fluid to said first fluid, said flue pipe assembly comprising:a first outer flue pipe having an inner surface and an outer surface, said outer surface being adapted to be in contact with said second fluid; a second inner flue pipe positioned within said first flue pipe and having an inner surface defining an interior space adapted to allow flow of said first fluid therethrough and an outer surface positioned in spaced opposed relationship to said inner surface of said first flue pipe to define a fluid flow space therebetween; and a valve assembly associated with said flue pipe assembly, said valve assembly being movable between a first open position in which said first fluid may flow through said fluid flow space and a second closed position in which fluid flow through said fluid flow space is restricted.
  • 11. A flue pipe assembly as set forth in claim 10 wherein said valve assembly is self powered to move between said open and closed position.
  • 12. A flue pipe assembly as set forth in claim 11 wherein said valve assembly includes a thermally responsive actuator, said actuator being operable to move said valve assembly to said open position in response to an increase in the temperature of said first fluid above a predetermined temperature.
  • 13. A flue pipe assembly as set forth in claim 10 wherein said inner flue pipe includes a plurality of spaced openings therein whereby said first fluid may flow from said interior space into said fluid flow space when said valve assembly is in said open position.
  • 14. A flue pipe assembly as set forth in claim 13 further comprising a flange member projecting into said interior space adjacent at least some of said openings.
  • 15. A flue pipe assembly as set forth in claim 14 wherein said flange member projects at an angle into the direction of flow of said first fluid.
  • 16. A flue pipe assembly as set forth in claim 10 wherein said valve assembly is positioned adjacent one end of said flue pipe assembly.
  • 17. A flue pipe assembly as set forth in claim 16 further comprising a second valve assembly positioned adjacent the other end of said fluid pipe assembly.
  • 18. A flue pipe assembly as set forth in claim 16 wherein said valve assembly includes a valve member movable into and out of engagement with said inner and outer flue pipe.
  • 19. A flue pipe assembly as set forth in claim 18 wherein said valve member is pivotably supported adjacent said outer flue pipe.
  • 20. A flue pipe as set forth in claim 10 wherein said valve assembly includes a thermally responsive actuation assembly.
  • 21. A flue pipe as set forth in claim 20 wherein said thermal actuator assembly includes a thermally responsive member positioned in overlying relationship to said interior space and operative to open said valve assembly in response to a temperature of said first fluid in excess of a predetermined temperature.
  • 22. A flue pipe as set forth in claim 21 wherein said thermally responsive member is made from a shape memory alloy.
  • 23. An improved flue pipe assembly for use in a fuel fired hot water heater comprising:an outer flue pipe adapted to form part of a reservoir of water to be heated by said water heater and having one end adapted to be positioned in overlying spaced relationship to a burner assembly of said water heater; an inner flue pipe positioned within said outer flue pipe and cooperating therewith to define an annular space between said inner and outer flue pipes, said annular space being open at opposite ends of said inner flue pipe; at least one opening adjacent said one end of said flue pipe assembly, said opening being adapted to allow combustion gases from said burner assembly to flow into said annular space; and a valve assembly positioned adjacent the other end of said flue pipe assembly, said valve assembly being operative to selectively open and close said open annular space at said other end of said flue pipe assembly to thereby resist air flow through said annular space when said burner assembly is in a standby mode.
  • 24. A flue pipe assembly as set forth in claim 23 wherein said valve assembly includes a thermally responsive actuator operative to open said valve assembly in response to heat generated by said burner assembly.
US Referenced Citations (47)
Number Name Date Kind
43313 Kellogg Jun 1864 A
1677630 Haas et al. Jul 1928 A
1773585 Klockau Aug 1930 A
2259845 Valjean Oct 1941 A
3921900 Cole Nov 1975 A
3976245 Cole Aug 1976 A
4076171 Swenson Feb 1978 A
4079884 Sherman Mar 1978 A
4136676 McCown et al. Jan 1979 A
4165833 Nagel Aug 1979 A
4182483 Swenson Jan 1980 A
4213477 Velasquez Jul 1980 A
4225080 Barth Sep 1980 A
4236668 Prikkel, III Dec 1980 A
4249883 Woolfolk Feb 1981 A
4251024 Feinberg Feb 1981 A
4262652 Butzen Apr 1981 A
4266929 Swenson May 1981 A
4267965 Everett May 1981 A
4289271 Barth Sep 1981 A
4294226 Feinberg Oct 1981 A
4299554 Williams Nov 1981 A
RE30936 Kmetz et al. May 1982 E
4372485 McCabe Feb 1983 A
4384671 Hayes May 1983 A
4386731 Barth Jun 1983 A
4390123 McCabe Jun 1983 A
4421096 Butzen Dec 1983 A
4437454 Hayes Mar 1984 A
4439139 Nelson et al. Mar 1984 A
4441653 Grudich Apr 1984 A
4460121 Hedrick Jul 1984 A
4555981 McCabe Dec 1985 A
4587706 Prikkel, III et al. May 1986 A
4770160 Schimmeyer Sep 1988 A
4919329 McCabe Apr 1990 A
4953510 Akkala et al. Sep 1990 A
5082172 Karabin et al. Jan 1992 A
5186385 Karabin et al. Feb 1993 A
5239947 Schimmeyer Aug 1993 A
5345963 Dietiker Sep 1994 A
5393221 McNally Feb 1995 A
5447125 McNally et al. Sep 1995 A
5695116 Karabin Dec 1997 A
5732692 Schimmeyer Mar 1998 A
5787846 Schimmeyer Aug 1998 A
5845632 Schimmeyer Dec 1998 A
Non-Patent Literature Citations (6)
Entry
G-Tech VAV-Boxes, 1997 G-Tech Products, Inc., pp. 1-5.
Energy Design Update, Jan. 1997, vol. 17, No. 1, pp. 1, 11 and 12.
American National Standard/CSA Standard for Gas Water Heaters, ANSI Z21, 10.1-1998, vol. I, Storage Water Heaters With Input Ratings of 75,000 Btu Per Hour or Less, pp. 1, 23, 24, 25, 93, 94, 95, and 96.
American National Standard/CSA Standard For Gas Water Heaters, ANSI Z21.10.3-1998, vol. III, Storage Water Heaters With Input Ratings Above 75,000 Btu Per hour, Circulating and Instanteous, pp. 1, 23, 24, 95, 96, 97, and 98.
Specification sheets—Introduction, p. 2; Power Vented Gas Water Heater Parts List, p. 14; Installation, p. 8; (date unknown).
Appliance Manufacturer, Jan. 1997, p. 76: Supplier Spotlight, Robertshaw Controls, “Good things Come in Small Packages”.