CA1288297C - Commercial storage water heater - Google Patents
Commercial storage water heaterInfo
- Publication number
- CA1288297C CA1288297C CA000520985A CA520985A CA1288297C CA 1288297 C CA1288297 C CA 1288297C CA 000520985 A CA000520985 A CA 000520985A CA 520985 A CA520985 A CA 520985A CA 1288297 C CA1288297 C CA 1288297C
- Authority
- CA
- Canada
- Prior art keywords
- burner
- tank
- water
- combustion tube
- tube
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 67
- 238000002485 combustion reaction Methods 0.000 claims abstract description 35
- 239000007789 gas Substances 0.000 claims abstract description 29
- 239000000203 mixture Substances 0.000 claims abstract description 16
- 239000000835 fiber Substances 0.000 claims abstract description 12
- 238000012546 transfer Methods 0.000 claims abstract description 9
- 239000011159 matrix material Substances 0.000 claims abstract description 8
- 239000000446 fuel Substances 0.000 claims description 14
- 230000005855 radiation Effects 0.000 claims description 5
- 238000013022 venting Methods 0.000 claims description 4
- 239000002344 surface layer Substances 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 2
- 239000002244 precipitate Substances 0.000 claims description 2
- 238000012423 maintenance Methods 0.000 claims 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 abstract description 6
- 239000003345 natural gas Substances 0.000 abstract description 3
- 239000010410 layer Substances 0.000 description 10
- 238000009413 insulation Methods 0.000 description 9
- 239000000919 ceramic Substances 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 239000008233 hard water Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- -1 e.g. Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
Landscapes
- Heat-Pump Type And Storage Water Heaters (AREA)
Abstract
ABSTRACT
A commercial storage water heater including a storage tank which is heated by a fiber matrix radiant burner positioned within an upright combustion tube at the lower end of the tank. A mixture of natural gas and air is forced by a blower at the upper end of the tank down through an inlet conduit and into the burner with combustion taking place flamelessly along the outer surface of the burner to radiate thermal energy to the combustion tube which in turn heats the water. Exhaust gases from the burner are direct-ed along a path leading upwardly through a plurality of flue tubes which transfer a part of the residual energy of the gases into the water. Exhaust gases exiting the flue tubes are directed through an outlet port and vented to a stack. The combustion tube and outlet port are positioned radially offset and on opposite sides of the longitudinal axis of the tank to facilitate access to the combustion tube and burner.
A commercial storage water heater including a storage tank which is heated by a fiber matrix radiant burner positioned within an upright combustion tube at the lower end of the tank. A mixture of natural gas and air is forced by a blower at the upper end of the tank down through an inlet conduit and into the burner with combustion taking place flamelessly along the outer surface of the burner to radiate thermal energy to the combustion tube which in turn heats the water. Exhaust gases from the burner are direct-ed along a path leading upwardly through a plurality of flue tubes which transfer a part of the residual energy of the gases into the water. Exhaust gases exiting the flue tubes are directed through an outlet port and vented to a stack. The combustion tube and outlet port are positioned radially offset and on opposite sides of the longitudinal axis of the tank to facilitate access to the combustion tube and burner.
Description
~ 97 COMMERCIAL STORAGE WATER HEATER
This invention relates to water heaters for commercial application, and particularly relates to commercial storage water heaters of approximately 3,785 liters/day capacity hot water demand.
Conventional commercial water heaters typically employ an upright cylindrical tank~having the burner unit mounted beneath the tank. The burner units are of the natural draft, gas-fired type which produce an open flame trans-ferring heat primarily by convection to the tank bottom lO wall, and flue tubes extend upwardly through the tank with the exhaust gases ventin~ from the upper end. Water heaters of this type normally operate with no better than about 78% steady state efficiency. The open flame burners can also produce significant amounts of pollutant NOX
15 emissions. In hard water environments the conventional heaters can encounter reduced operating life due to liming in which a buildup of insoluble deposits on the inside bottom of the tank gradually forms an insulation layer between the water and the burners, and this can lead to hot spots and burnout in the tank bottom wall. The mounting of the burners, air/fuel inlets and burner controls beneath the tank near the supporting floor also creates potential service interruption problems, such as from water flooding reaching the controls.
25 It is a general object of the invention, therefore, to provide a new and improved water heater for use in :: , ' ' .', . . .
- ~
~ . .
: . .
~ .
- . ' ' :
.
Z~3 commercial applications which obviates or reduces the limitations of conventional water heaters.
The present invention provides a water heater comprising the combination of a tank forming a chamber for storing water, an elongate cylindrical combustion tube mounted vertically within the chamber with the outer wall of the tube in heat exchange relationship with the water, a fiber matrix radiant burner of cylindrical shell configuration concentrically mounted vertically within and radially spaced from the combustion tube, said burner being mounted within the tube at a position disposed below the mid-span of the combustion tube, means for directing a mixture of fuel and air into the center of the burner with the mixture diffusing radially outwardly for flameless combustion uniformly about the outer surface layer of the burner to transfer thermal energy sub-; stantially by radiation uniformly to the inner surface of the combustion tube, and means for directing exhaust gases from the burner along a path through the chamber in heat exchange relation-ship with the water for transferring residual thermal energy to the water.
In it:s preferred embodiments this commercial storage water heater operates with improved efficiency and thereby lower fuel costs for comparable hot water requirements. It also operates with reduced pollutant exhaust emissions as compared to conven-tionalwater heaters. The water heater is dependable in operation with the burner controls and air/fuel inlets positioned at or near the upper end of the storage tank. The water heater herein described has the potential for a relatively longer life cycle as compared to conventional heaters.
, ' . ' " ~-. ~ :
~ ~88~
-2a-The foregoing and additional features of the invention will appear from the following specification in which the several embodiments have been set forth in detail in conjunction with the accompanying drawings.
'~
.
3~ 9'i' Figure 1 is a perspective, partially cut-away, view of a commercial storage water heater of the invention.
Figure 2 is a vertical axial section view to an enlarged scale of the water heater of Figure 1.
Figure 3 is a cross-section view taken along the line 3-3 of Figure 2.
In the drawings the commercial storage water heater incor-porating a preferred embodiment of the invention is illus-trated generally at 10. The heater is comprised of a tank 10 11 formed by a cylindrical side wall 12 and upper and lower ends 14, 16 which define a water storage chamber 18. Tank 11 is sized according to the specifications and require-ments for a particular application, and for the typical commercial water storage application the tank capacity 15 would be sufficient to supply hot water demand of at least 1,900 liters/day. The tank is thermally insulated by an insulation layer 20 mounted completely around the side wall, a bottom insulation layer 22 spaced below tank lower end 16, and a top insulation layer 24 spaced above upper end 14. A plurality of feet 26 depend ~elow lower layer 22 for supporting the tank upright with its longitudinal axis vertical.
At a position radially spaced from center axis 28 of the tank a circular opening 30 is formed through top insulation layer 24, and a concentric opening 32 of smaller diameter is formed through tank upper end 14. An elongate cylind-rical shell 34 fitted at its upper end with a cylindrical mounting plate 36 is inserted through the openings 30 and 32 with the mounting plate detachably secured to tank upper end 14 for holding the shell upright along an axis spaced radially outwardly from the center axis of the tank. The lower end of shell 34 is mounted through an opening 38 formed in tank lower end 16.
329~
A fiber matrix burner 40 of cylindrical shell configuration is mounted concentric with and radially spaced within a combustion -tube 42 which is defined by the lower portion of shell 34. Burner 40 is suspended within the combustion tube by an inlet condult 44 which extends down through an opening concentrically formed ln mounting plate 36. The lower end of conduit 44 is connected through a union 46 with an inlet pipe 48 which leads through a divider plate 49 into the inner volume 50 of the burner. Inlet pipe 48 projects through an opening in an insulation collar 52 mounted within shell 34. An insulation end cap 54 is provided at the lower end of the burner to prevent over-heating of the burner metal support structure.
A mixture of air and fuel, e.g., natural gas, is directed under pressure into the burner by means of an air blower 56 mounted by supports 58 on top of the tank within an enclosure 60. An air filter 62 is mounted above enclosure 60 and connects through tube 66 with the inlet of the blower. ~he blower is powered by a motor 68 operated by a suitable control circuit, which can be of conventional design, contained within the enclosure 60.
Supply tubing, not shown, connects the gas inlet pipe with a suitable gas valve operated under influence of the control circuit directing such gas through opening 78. The pressurized air mixes with the supply of gas and flows downwardly into the inner volume 50 of the burner, with the gas diffusing outwardly through the interstitial spaces between the fibers of the burner shell 80.
~ 3~3~ 7 -4a-Burner shell 80 is comprised of a fiber matrix composition in which the buxner shell is made from a slurry composition of ceramic fibers, binding agent and filler which are vacuum-formed about a metal screen. ~fter high temperature firing the burner shell is comprised of a porous layer of ' ~ ~
- - -: .
3~
randomly-oriented ceramic fibers with interstitial spaces through which the air/fuel mixture diffuses outwardly.
Operation of the burner is characterized in that combustion takes place flamelessly and uniformly on the outer surface layer at about ~800F, and with relatively little noise.
The incandescent, hot surface of the burner shell transfers approximately one-half of the fuel's available energy directly by thermal radiation to the opposing heat sink comprising the combustion tube 42 which in turn heats the 10 surrounding water by conduction and convection. The relatively low thermal conductivity of the fibers in the burner shell, as well as the convective cooling from the incoming flow of air/fuel, allows the burner to operate safely without flashback. This burner is further charac-15 terized in operating at very low excess air levels, withrelatively low pressure drop, turns on and off instanta-neously, and the fiber matrix layer is not suscepti~le to thermal shock. As a result of the relatively low com-bustion temperature on the burner surface, the resulting 20 NOX emissions are less than 15 ppm. The emissions of CO
and unburned hydrocarbons are also lower. The burner operates at a heat release rate per unit area of burner surface on the order of 120,000 ~tu/hr-ft2. For a typical commercial storage water heater application burner 40 can 25 be sized on the order of 59 kW (200,000 Btu/hr).
Igniter elements 82 depend from plate 49 within the com-bustion tube 42 and the tips of the elements extend over the upper-end surface of the burner 40. The igniter elements can be either of two types of ignition systems.
3a Direct spark ignition, as shown in Figure 2, ig~ites the fuel/air mixture by means of an electrical spark. Alterna-tively, hot surface ignition, in which a silicon carbide igniter is electrically heated above the fuel/air ignition temperature, can be used. Control circuits appropriate to 35 either ignition system activate the ignition elements through wires, not shown, which extend down through the inside of shell 34. The igniter elements are typically 3~297 operated only during burner startup. A flame sensing element 83 also activated by the control circuits appropri-ate to either ignition system senses the presence of a flame using the principle of flame rectification. Ignition control systems employing either direct spark or hot surface ignition with flame rectification flame sensing are commercially available and well known to those knowledge-able in the art.
10 The products of combustion flow downwardly from the burner and exit through the open end 84 of combustion tube 42 into a flue inlet header 86 which is defined by the space between tank lower end 16 and bottom insulation layer 22.
From the inlet header the exhaust gases flow upwardly 15 through a plurality, shown as eight, of flue tubes 88-102 extending vertically through water chamber 18 and which are mounted at their opposite ends throu~h openings formed in the upper and lower ends of the tank. Flue baffles 104, 106 are mounted within each of the flue tubes for creating 20 turbulent flow to enhance heat exchange with the tube walls. A substantial portion of the residual thermal energy in the exhaust gases is thereby transferred to the water within the tank.
Exhaust gases discharge from the upper ends of the flue tubes into an outlet header 108 defined by the space between tank upper end 14 and the top insulation layer 24.
The exhaust gases flow from the header through an outlet port 110 and connector tube 112 for venting to a stack, not shown.
30 A cold water inlet opening 114 is provided at the lower end of the tank, and a hot water outlet opening 116 is provided at the upper end. Alternatively, the water inlet and outlet openings can be set in the tank upper end 14 to allow for water connections through the top of the tank.
In such a configuration a dip tube, not shown, would direct the cold inlet water to the bottom of the tank. A pressure ~ S~3 7 relief valve 118 is mounted at the upper end of the tank and a water drain 120 is provided at its lower end.
The use and operation of the invention will be described as applied to a commercial water storage application with tank 11 sized to provide a hot water demand capacity of 3,785 liters/day and with the fiber matrix burner sized at 59 kW.
It is understood that systems could be scaled up or down from these sizes and retain essentially the same perfor-mance. Under influence of the control circuit the gas 10 valve in enclosure 60 is opened to direct natural gas into inlet 78, and the blower motor is powered to draw air downwardly through filter 62 into blower 56 which forces pressurized air past the gas inlet for mixing with the supply of gas. The air/fuel mixture is forced under 15 pressure into the inner volume of burner 40 where it diffuses outwardly through the burner shell. Actuation of the igniter elements 82 then ignites the mixture which combusts flamelessly and uniformly across the entire active burner surface in a relatively shallow combustion zone.
The incandescent burner shell transfers thermal energy primarily by radiation to combustion tube 42 which in turn heats the water. Exhaust gases from the burner flow through inlet header 86 and pass upwardly through the flue tubes which t,ransfer residual thermal energy to the water.
Water temperature is sensed by a dual bulb thermostat 122 mounted on the side of the tank, and when the preset water temperature is reached the control circuit shuts off the gas valve and deactivates the blower.
Operation of the water heater of the invention has been demonstrated to achieve a steady state efficiency on the order of 84% as compared to efficiencies in the range of 78% from water heaters of conventional design employing natural draft open flame burners. The increased efficiency of the invention is realized by the novel configuration which achieves more uniform heat transfer and particularly more efficient heat transfer in the radiant zone. Approxi-:~ ' . .
-3~3Z~
mately one-half of the available energy is transferred by radiation through the combustion tube into the surrounding water, with a substantial portion of the residual energy being transferred to the water from the flue tubes. The burner also operates with substantially reduced NOX
emissions as compared to conventional heaters employing open-flame type burners.
Other advantages from the invention include the provision of the vertically oriented combustion tube which minimizes the problem of liming inherent in conventional water heaters heated from below. Precipitation build-up of insoluble compounds around the heat transfer surfaces, as is common in hard water environments, is lessened because of the more uniform heat flux along the heat transfer surfaces thus minimizing hot spots, and precipitate that does form on the vertical tubes will settle onto the tank lower end 16, thus having less of an impact on heat ex-change to the water storage tank. This will increase the heater life and reduce the life-cycle cost. Water heater 10 is also safer and more dependable in operation due to the arrangement in which the burner is mounted internally - with no open flame exposed to ambient, and is less suscep-tible to damage by water flooding.
25 While the foregoing embodiment îs at present considered to be preferred it is understood that numerous variations and modifications may be made therein by those skilled in the art and it is intended to cover in the claims all such variations and modifications as fall within the true spirit 30 and scope of the invention.
This invention relates to water heaters for commercial application, and particularly relates to commercial storage water heaters of approximately 3,785 liters/day capacity hot water demand.
Conventional commercial water heaters typically employ an upright cylindrical tank~having the burner unit mounted beneath the tank. The burner units are of the natural draft, gas-fired type which produce an open flame trans-ferring heat primarily by convection to the tank bottom lO wall, and flue tubes extend upwardly through the tank with the exhaust gases ventin~ from the upper end. Water heaters of this type normally operate with no better than about 78% steady state efficiency. The open flame burners can also produce significant amounts of pollutant NOX
15 emissions. In hard water environments the conventional heaters can encounter reduced operating life due to liming in which a buildup of insoluble deposits on the inside bottom of the tank gradually forms an insulation layer between the water and the burners, and this can lead to hot spots and burnout in the tank bottom wall. The mounting of the burners, air/fuel inlets and burner controls beneath the tank near the supporting floor also creates potential service interruption problems, such as from water flooding reaching the controls.
25 It is a general object of the invention, therefore, to provide a new and improved water heater for use in :: , ' ' .', . . .
- ~
~ . .
: . .
~ .
- . ' ' :
.
Z~3 commercial applications which obviates or reduces the limitations of conventional water heaters.
The present invention provides a water heater comprising the combination of a tank forming a chamber for storing water, an elongate cylindrical combustion tube mounted vertically within the chamber with the outer wall of the tube in heat exchange relationship with the water, a fiber matrix radiant burner of cylindrical shell configuration concentrically mounted vertically within and radially spaced from the combustion tube, said burner being mounted within the tube at a position disposed below the mid-span of the combustion tube, means for directing a mixture of fuel and air into the center of the burner with the mixture diffusing radially outwardly for flameless combustion uniformly about the outer surface layer of the burner to transfer thermal energy sub-; stantially by radiation uniformly to the inner surface of the combustion tube, and means for directing exhaust gases from the burner along a path through the chamber in heat exchange relation-ship with the water for transferring residual thermal energy to the water.
In it:s preferred embodiments this commercial storage water heater operates with improved efficiency and thereby lower fuel costs for comparable hot water requirements. It also operates with reduced pollutant exhaust emissions as compared to conven-tionalwater heaters. The water heater is dependable in operation with the burner controls and air/fuel inlets positioned at or near the upper end of the storage tank. The water heater herein described has the potential for a relatively longer life cycle as compared to conventional heaters.
, ' . ' " ~-. ~ :
~ ~88~
-2a-The foregoing and additional features of the invention will appear from the following specification in which the several embodiments have been set forth in detail in conjunction with the accompanying drawings.
'~
.
3~ 9'i' Figure 1 is a perspective, partially cut-away, view of a commercial storage water heater of the invention.
Figure 2 is a vertical axial section view to an enlarged scale of the water heater of Figure 1.
Figure 3 is a cross-section view taken along the line 3-3 of Figure 2.
In the drawings the commercial storage water heater incor-porating a preferred embodiment of the invention is illus-trated generally at 10. The heater is comprised of a tank 10 11 formed by a cylindrical side wall 12 and upper and lower ends 14, 16 which define a water storage chamber 18. Tank 11 is sized according to the specifications and require-ments for a particular application, and for the typical commercial water storage application the tank capacity 15 would be sufficient to supply hot water demand of at least 1,900 liters/day. The tank is thermally insulated by an insulation layer 20 mounted completely around the side wall, a bottom insulation layer 22 spaced below tank lower end 16, and a top insulation layer 24 spaced above upper end 14. A plurality of feet 26 depend ~elow lower layer 22 for supporting the tank upright with its longitudinal axis vertical.
At a position radially spaced from center axis 28 of the tank a circular opening 30 is formed through top insulation layer 24, and a concentric opening 32 of smaller diameter is formed through tank upper end 14. An elongate cylind-rical shell 34 fitted at its upper end with a cylindrical mounting plate 36 is inserted through the openings 30 and 32 with the mounting plate detachably secured to tank upper end 14 for holding the shell upright along an axis spaced radially outwardly from the center axis of the tank. The lower end of shell 34 is mounted through an opening 38 formed in tank lower end 16.
329~
A fiber matrix burner 40 of cylindrical shell configuration is mounted concentric with and radially spaced within a combustion -tube 42 which is defined by the lower portion of shell 34. Burner 40 is suspended within the combustion tube by an inlet condult 44 which extends down through an opening concentrically formed ln mounting plate 36. The lower end of conduit 44 is connected through a union 46 with an inlet pipe 48 which leads through a divider plate 49 into the inner volume 50 of the burner. Inlet pipe 48 projects through an opening in an insulation collar 52 mounted within shell 34. An insulation end cap 54 is provided at the lower end of the burner to prevent over-heating of the burner metal support structure.
A mixture of air and fuel, e.g., natural gas, is directed under pressure into the burner by means of an air blower 56 mounted by supports 58 on top of the tank within an enclosure 60. An air filter 62 is mounted above enclosure 60 and connects through tube 66 with the inlet of the blower. ~he blower is powered by a motor 68 operated by a suitable control circuit, which can be of conventional design, contained within the enclosure 60.
Supply tubing, not shown, connects the gas inlet pipe with a suitable gas valve operated under influence of the control circuit directing such gas through opening 78. The pressurized air mixes with the supply of gas and flows downwardly into the inner volume 50 of the burner, with the gas diffusing outwardly through the interstitial spaces between the fibers of the burner shell 80.
~ 3~3~ 7 -4a-Burner shell 80 is comprised of a fiber matrix composition in which the buxner shell is made from a slurry composition of ceramic fibers, binding agent and filler which are vacuum-formed about a metal screen. ~fter high temperature firing the burner shell is comprised of a porous layer of ' ~ ~
- - -: .
3~
randomly-oriented ceramic fibers with interstitial spaces through which the air/fuel mixture diffuses outwardly.
Operation of the burner is characterized in that combustion takes place flamelessly and uniformly on the outer surface layer at about ~800F, and with relatively little noise.
The incandescent, hot surface of the burner shell transfers approximately one-half of the fuel's available energy directly by thermal radiation to the opposing heat sink comprising the combustion tube 42 which in turn heats the 10 surrounding water by conduction and convection. The relatively low thermal conductivity of the fibers in the burner shell, as well as the convective cooling from the incoming flow of air/fuel, allows the burner to operate safely without flashback. This burner is further charac-15 terized in operating at very low excess air levels, withrelatively low pressure drop, turns on and off instanta-neously, and the fiber matrix layer is not suscepti~le to thermal shock. As a result of the relatively low com-bustion temperature on the burner surface, the resulting 20 NOX emissions are less than 15 ppm. The emissions of CO
and unburned hydrocarbons are also lower. The burner operates at a heat release rate per unit area of burner surface on the order of 120,000 ~tu/hr-ft2. For a typical commercial storage water heater application burner 40 can 25 be sized on the order of 59 kW (200,000 Btu/hr).
Igniter elements 82 depend from plate 49 within the com-bustion tube 42 and the tips of the elements extend over the upper-end surface of the burner 40. The igniter elements can be either of two types of ignition systems.
3a Direct spark ignition, as shown in Figure 2, ig~ites the fuel/air mixture by means of an electrical spark. Alterna-tively, hot surface ignition, in which a silicon carbide igniter is electrically heated above the fuel/air ignition temperature, can be used. Control circuits appropriate to 35 either ignition system activate the ignition elements through wires, not shown, which extend down through the inside of shell 34. The igniter elements are typically 3~297 operated only during burner startup. A flame sensing element 83 also activated by the control circuits appropri-ate to either ignition system senses the presence of a flame using the principle of flame rectification. Ignition control systems employing either direct spark or hot surface ignition with flame rectification flame sensing are commercially available and well known to those knowledge-able in the art.
10 The products of combustion flow downwardly from the burner and exit through the open end 84 of combustion tube 42 into a flue inlet header 86 which is defined by the space between tank lower end 16 and bottom insulation layer 22.
From the inlet header the exhaust gases flow upwardly 15 through a plurality, shown as eight, of flue tubes 88-102 extending vertically through water chamber 18 and which are mounted at their opposite ends throu~h openings formed in the upper and lower ends of the tank. Flue baffles 104, 106 are mounted within each of the flue tubes for creating 20 turbulent flow to enhance heat exchange with the tube walls. A substantial portion of the residual thermal energy in the exhaust gases is thereby transferred to the water within the tank.
Exhaust gases discharge from the upper ends of the flue tubes into an outlet header 108 defined by the space between tank upper end 14 and the top insulation layer 24.
The exhaust gases flow from the header through an outlet port 110 and connector tube 112 for venting to a stack, not shown.
30 A cold water inlet opening 114 is provided at the lower end of the tank, and a hot water outlet opening 116 is provided at the upper end. Alternatively, the water inlet and outlet openings can be set in the tank upper end 14 to allow for water connections through the top of the tank.
In such a configuration a dip tube, not shown, would direct the cold inlet water to the bottom of the tank. A pressure ~ S~3 7 relief valve 118 is mounted at the upper end of the tank and a water drain 120 is provided at its lower end.
The use and operation of the invention will be described as applied to a commercial water storage application with tank 11 sized to provide a hot water demand capacity of 3,785 liters/day and with the fiber matrix burner sized at 59 kW.
It is understood that systems could be scaled up or down from these sizes and retain essentially the same perfor-mance. Under influence of the control circuit the gas 10 valve in enclosure 60 is opened to direct natural gas into inlet 78, and the blower motor is powered to draw air downwardly through filter 62 into blower 56 which forces pressurized air past the gas inlet for mixing with the supply of gas. The air/fuel mixture is forced under 15 pressure into the inner volume of burner 40 where it diffuses outwardly through the burner shell. Actuation of the igniter elements 82 then ignites the mixture which combusts flamelessly and uniformly across the entire active burner surface in a relatively shallow combustion zone.
The incandescent burner shell transfers thermal energy primarily by radiation to combustion tube 42 which in turn heats the water. Exhaust gases from the burner flow through inlet header 86 and pass upwardly through the flue tubes which t,ransfer residual thermal energy to the water.
Water temperature is sensed by a dual bulb thermostat 122 mounted on the side of the tank, and when the preset water temperature is reached the control circuit shuts off the gas valve and deactivates the blower.
Operation of the water heater of the invention has been demonstrated to achieve a steady state efficiency on the order of 84% as compared to efficiencies in the range of 78% from water heaters of conventional design employing natural draft open flame burners. The increased efficiency of the invention is realized by the novel configuration which achieves more uniform heat transfer and particularly more efficient heat transfer in the radiant zone. Approxi-:~ ' . .
-3~3Z~
mately one-half of the available energy is transferred by radiation through the combustion tube into the surrounding water, with a substantial portion of the residual energy being transferred to the water from the flue tubes. The burner also operates with substantially reduced NOX
emissions as compared to conventional heaters employing open-flame type burners.
Other advantages from the invention include the provision of the vertically oriented combustion tube which minimizes the problem of liming inherent in conventional water heaters heated from below. Precipitation build-up of insoluble compounds around the heat transfer surfaces, as is common in hard water environments, is lessened because of the more uniform heat flux along the heat transfer surfaces thus minimizing hot spots, and precipitate that does form on the vertical tubes will settle onto the tank lower end 16, thus having less of an impact on heat ex-change to the water storage tank. This will increase the heater life and reduce the life-cycle cost. Water heater 10 is also safer and more dependable in operation due to the arrangement in which the burner is mounted internally - with no open flame exposed to ambient, and is less suscep-tible to damage by water flooding.
25 While the foregoing embodiment îs at present considered to be preferred it is understood that numerous variations and modifications may be made therein by those skilled in the art and it is intended to cover in the claims all such variations and modifications as fall within the true spirit 30 and scope of the invention.
Claims (8)
1. A water heater comprising the combination of a tank forming a chamber for storing water, an elongate cylindrical combustion tube mounted vertically within the chamber with the outer wall of the tube in heat exchange relationship with the water, a fiber matrix radiant burner of cylindrical shell con-figuration concentrically mounted vertically within and radially spaced from the combustion tube, said burner being mounted within the tube at a position disposed below the mid-span of the combustion tube, means for directing a mixture of fuel and air into the center of the burner with the mixture diffusing radially out-wardly for flameless combustion uniformly about the outer surface layer of the burner to transfer thermal energy substantially by radiation uniformly to the inner surface of the combustion tube, and means for directing exhaust gases from the burner along a path through the chamber in heat exchange relationship with the water for transferring residual thermal energy to the water.
2. A water heater as in claim 1, in which the tank includes an upstanding cylindrical side wall enclosed by upper and lower ends, said combustion tube is mounted upright within the chamber whereby insoluble compounds which precipitate from the water over time are free to deposit on the lower end of the tank minimizing fouling of the combustion tube.
3. A water heater as in claim 1, in which the means for directing the mixture of fuel and air into the burner includes an inlet conduit extending into the tank and connected with the burner, and blower means for forcing the mixture under pressure through the inlet conduit and into the burner.
4. A water heater as in claim 3, in which the tank in-cludes an upstanding cylindrical side wall enclosed by upper and lower ends, said inlet conduit is upright and extends through the upper end of the tank, and the blower means is mounted above the upper end of the tank.
5. A water heater as in claim 1, in which the means for directing the exhaust gases includes flue tube means having inlet and outlet ends, an inlet manifold for directing exhaust gases from the burner into the inlets of the flue tube means, and an outlet manifold communicating with the outlet of the flue tube means for venting exhaust gases from the heater.
6. A water heater as in claim 5, which includes means forming an outlet port in the upper end of the tank for venting the exhaust gases from the outlet manifold, said outlet port and said combustion tube being positioned radially offset and on opposite sides of the vertical axis of the tank whereby the combustion tube is accessible for maintenance and repair.
7. A water heater comprising the combination of a tank having a vertically arranged cylindrical side wall and upper and lower ends forming a chamber for storing water, an elongate cylindrical combustion tube mounted upright within the chamber and radially offset from the longitudinal axis of the side wall, a fiber matrix radiant burner of cylindrical shell configuration mounted within the lower end of the combustion tube and radially spaced therefrom, an inlet conduit mounted upright with its lower end connected with the burner and with its upper end extending through the upper end of the tank, a blower mounted on the upper end of the tank for directing a mixture of gas and fuel under pressure down through the inlet conduit into the burner for diffusing radially outwardly through the burner wall, means for combusting the mixture to flamelessly burn uniformly along the outer surface of the burner and radiate heat to the combustion tube and thereby heat water within the chamber, a plurality of flue tubes mounted upright within the chamber, means for directing exhaust gases from the burner in a path out of the lower end of the combustion tube and upwardly through the flue tubes, and an outlet port formed in the upper end of the tank for venting exhaust gases exiting from the flue tubes.
8. A heater as in claim 7, which includes gas inlet means connecting with the inlet conduit at the upper end of the tank, and control means on the upper end of the tank for controlling operation of the gas inlet and blower.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000520985A CA1288297C (en) | 1986-10-21 | 1986-10-21 | Commercial storage water heater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000520985A CA1288297C (en) | 1986-10-21 | 1986-10-21 | Commercial storage water heater |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1288297C true CA1288297C (en) | 1991-09-03 |
Family
ID=4134186
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000520985A Expired - Lifetime CA1288297C (en) | 1986-10-21 | 1986-10-21 | Commercial storage water heater |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1288297C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114440459A (en) * | 2020-10-16 | 2022-05-06 | 青岛经济技术开发区海尔热水器有限公司 | Heat exchange system and gas water heater |
| CN117006500A (en) * | 2023-10-07 | 2023-11-07 | 国网辽宁省电力有限公司 | Regional energy heating system |
-
1986
- 1986-10-21 CA CA000520985A patent/CA1288297C/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114440459A (en) * | 2020-10-16 | 2022-05-06 | 青岛经济技术开发区海尔热水器有限公司 | Heat exchange system and gas water heater |
| CN117006500A (en) * | 2023-10-07 | 2023-11-07 | 国网辽宁省电力有限公司 | Regional energy heating system |
| CN117006500B (en) * | 2023-10-07 | 2023-12-01 | 国网辽宁省电力有限公司 | Regional energy heating system |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |