Fire Tube Heater

Abstract

A fire tube heater assembly, sometimes referred to as boilers and/or water heaters, and method of accommodating elongation of the fire tubes associated with such heating devices. The fire tube heater assembly includes a plurality of fire tubes that are configured and oriented to effectuate efficient thermal exchange between the heating fluid, commonly a gas combustion product, and the fluid being heated. At least one end of the plurality of tubes are supported by a tube support. The tube support includes a bellows or other deformable structure that accommodates changes in the longitudinal length associated with thermal expansion and contraction of the fire tubes during operation of the first tube heater assembly and in a manner that maintains segregation between the heating and heated fluid flows.

Claims

1. A fire tube heater assembly comprising: a housing; a plurality of tubes disposed in the housing; and a tube support constructed to support at least two of the plurality of tubes and maintain a segregation between a combustion gas flow and a fluid disposed in the housing and effectuate thermal exchange therebetween, the tube support including a bellows section constructed to accommodate changes in the length of the at least two of the plurality of tubes caused by thermal response to operation of the fire tube heater.

2. The fire tube heater assembly of claim 1 wherein the plurality of tubes is further defined as a first group of tubes and a second group of tubes that are both supported by the tube support.

3. The fire tube heater assembly of claim 2 wherein the bellows section is disposed between the first group of tubes and the second group of tubes.

4. The fire tube heater assembly of claim 1 wherein the plurality of tubes are oriented in a concentric circular pattern.

5. The fire tube heater assembly of claim 1 wherein each of the plurality of tubes has an elongated cross-sectional shape.

6. The fire tube heater assembly of claim 1 further comprising a first inlet and a first outlet through the housing that are fluidly connected to a chamber configured to contain the fluid and a second inlet and a second outlet through the housing associated and fluidly connected to the plurality of tubes.

7. The fire tube heater assembly of claim 1 wherein the bellows section is nearer a bottom of the housing than a top of the housing.

8. The fire tube heater assembly of claim 7 further comprising a baffle configured to direct the fluid toward the plurality of tubes.

9. The fire tube heater assembly of claim 1 further comprising a divider cylinder disposed about the plurality of tubes and positionally fixed relative to the housing and configured to segregate the fluid from the combustion gas flow.

10. The fire tube heater assembly of claim 1 further comprising a burner configured to generate the combustion gas flow and fluidly connected to the plurality of tubes.

11. A method of accommodating elongation of fire tube heater tubes during operation of a fire tube heater, the method comprising: supporting a plurality of fire tubes with a tube support structure that is deformable to concurrently accommodate changes in a longitudinal length of more than one of fire tubes.

12. The method of claim 11 wherein the tube support structure is formed as a bellows section and a first end of the bellows section is secured to a housing of fire tube heater and a second end of the bellows section is secured to each of the plurality of fire tubes and is movable relative to the first end.

13. The method of claim 12 wherein the second end of the bellows section moves away from the first end in a direction aligned with a longitudinal axis of the plurality of fire tubes as a temperature of the fire tubes increases.

14. The method of claim 12 further comprising aligning the first end and the second end of the bellows section when the fire tube heater is near an unheated condition.

15. The method of claim 11 further comprising rigidly supporting a longitudinal end of each of the plurality of fire tubes that is opposite the tube support.

16. The method of claim 11 further comprising providing a baffle to direct a flow of a fluid being heated in a radial direction toward the plurality of fire tubes.

17. A boiler tube support assembly comprising: a body configured to sealing cooperate with an end portion of a plurality of fire tubes; and a bellows section that extends in an outward direction aligned with a longitudinal axis of the plurality of fire tubes and which is disposed between a first portion of the body that is positionally secured relative to a housing disposed about the plurality of fire tubes and a second portion of the body that is movable relative to the first portion along the longitudinal axis in response to changes in temperature of the plurality of fire tubes.

18. The boiler tube support assembly of claim 17 wherein the first portion of the body and the second portion of the body both extend in a direction that is transverse to the longitudinal axis associated with the plurality of fire tubes.

19. The boiler tube support assembly of claim 17 wherein the bellows section is constructed to maintain separation between a heating fluid flow and a heated fluid flow.

20. The boiler tube support assembly of claim 19 further comprising at least one baffle disposed in the housing and oriented to direct the heated fluid flow in a radial direction toward the plurality of fire tubes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings illustrate preferred embodiments presently contemplated for carrying out the invention. In the drawings:

[0015] FIG. 1 is an elevational cross section view of a fire tube heater assembly or apparatus according to the present invention;

[0016] FIG. 2 is a top plan view a fire tube mounting structure of the fire tube heater assembly shown in FIG. 1;

[0017] FIG. 3 is an elevational cross section view of the fire tube mounting structure shown in FIG. 2;

[0018] FIG. 4 is a perspective view of the view shown in FIG. 3;

[0019] FIG. 5 is an elevational cross section view of a portion of the fire tube heater assembly shown in FIG. 1 proximate the fire tube mounting structure shown in FIGS. 2-4; and

[0020] FIG. 6 is a graph that shows efficiencies associated with operation of the fire tube heater assembly shown in FIG. 1 as a function of the temperature of the heated fluid inlet flow.

DETAILED DESCRIPTION

[0021] FIG. 1 shows a cross-sectional view of a water heater, water heating apparatus, boiler, or fire tube heater assembly 10 according to the present invention. Fire tube heater assembly 10 includes a housing 12 that generally defines a vertically oriented footprint of the device. A burner 14 is associated with a combustion chamber 16 which is configured to generate a combustion gas flow 18 associated with generating the thermal exchange associated with operation of fire tube heater assembly 10. It should be appreciated that the operation of burner 14 can be configured and/or otherwise manipulated to satisfy various demands associated with the desired volumes, throughputs, and parameters associated with the intended demand associated with use of fire tube heater assembly 10.

[0022] Fire tube heater assembly 10 includes a plurality of fire tubes or simply tubes 20, 22 that extend in a longitudinal direction, indicated by arrow 24, within the confines of housing 12. Fire tube heater assembly 10 includes a first or top tube sheet or upper tube support 28 and a second or bottom or lower tube support 30. Understandably, the terms top, bottom, upper, and lower are indicative of heater assemblies having generally vertical operating orientations but it is appreciated that the present invention is applicable to other heater configurations and that the functions associated with the same could be provided in alternate orientations.

[0023] Tube supports 28, 30 are disposed at generally opposite longitudinal ends of tubes 20 and/or tubes 22 and are constructed to provide a desired orientation of the plurality of tubes 20, 22 relative to the generally surrounding housing 12. A heated fluid cavity 34 is formed to generally encircle the surface areas associated with tubes 20, 22 to effectuate an efficient thermal exchange between tubes 20, 22 and the fluid, such as water, that surrounds them.

[0024] Although described hereafter as water and/or combustion gas fluid passages and/or portions thereof, it is appreciated that fire tube heater assembly 10 can be utilized to effectuate thermal exchanges between various fluid flows wherein it is desired to maintain fluid isolation between the respective fluid flows regardless of the composition or constituencies of the discrete fluid flows. For brevity, the fluid flow passage associated the combustion gas fluid path is hereafter referred to as heating fluid flow path and features whereas the fluid paths associated with the alternate fluid, whether provided as water or another fluid, are referred to as features of the heated fluid flow path and/or features. It should be appreciated that such monikers or nomenclature are utilized to designate the discrete features of fire tube heater assembly 10 associated with the direction of the thermal exchange between the respective fluid flows during operation of the fire tube heater assembly during demand or ON conditions. When utilized as a water heating appliance, fire tube heater assembly 10 includes a heated fluid inlet or water inlet 36 and a heated fluid outlet or water outlet 38 associated with the flow of the heated fluid through fire tube heater assembly 10. As should be appreciated, during a demand condition, the temperature associated with the fluid flow at heated fluid inlet 36 is less than the temperature associated with the fluid flow at heated fluid outlet 38 due to the thermal exchange associated with the thermal interaction of the water fluid flow being directed over and about tubes 20, 22 associated with the combustion gas flows.

[0025] During operation, heated combustion gases travel through tubes 20 in a generally downward direction, indicated by arrows 40, pass through lower tube support 30, are directed toward the plurality of radially outward oriented tubes 22, and exit fire tube heater assembly 10 at a vent pipe 46. Such a flow methodology is only one exemplary flow methodology associated with the present invention. Any condensate generated on the heating fluid side of fire tube heater assembly 10 during the thermal exchange with the heated fluid can be removed from the system via a condensate trap and/or drain 47 disposed in a lower portion of fire tube heater assembly 10.

[0026] During operation, such as during start up, shut down, and deviations associated with the load or demand upon fire tube heater assembly 10, the longitudinal length of one or more of tubes 20, 22 changes in response to the thermal exchange between the combustion gases associated with the internal volume defined by tubes 20, 22 and the flow of the heated fluid around the tubes 20, 22. That is, as the thermal output of the combustion process increases and/or decreases, the temperature of the input water increases and/or decreases, and/or the demand increases and/or decreases, the longitudinal lengths of tubes 20, 22 increases and decreases due to the thermal properties of tubes 20, 22 and in response to the deviations in the thermal operations of fire tube heater assembly 10.

[0027] Referring to FIGS. 1-5, lower tube support 30 is defined by a body 100 that includes a first portion 102 and a second portion 104 that are movable relative to one another in a generally axial direction aligned with a longitudinal axis 24 of one or more of tubes 20, 22. An outer wall 106 of body 100 extends from first portion 102 of lower tube support 30 so as to define a cavity 110 therebehind. First and second portions 102, 104 of lower tube support plate 30 are supported by a bellows structure, bellows assembly, or simply a bellows 120 that accommodates deviations in the longitudinal length of one or more of tubes 20, 22 in response to changes in the longitudinal length of tubes 20, 22 as a function of the thermal performance of fire tube heater assembly 10.

[0028] Although bellows 120 is disclosed below as accommodating changes to the longitudinal length of tubes 20, associated with the primary heat exchange with the heated fluid, it is appreciated that fire tube heater assembly 10 could be configured so that all of tubes 20, 22 were associated with the movable portion of lower tube support 30.

[0029] Bellows 120 is defined by a first portion 122 that extends in a generally downward and circumferential direction from first portion 102 of lower tube support 30. A second portion 124 of bellows 120 extends from a free or cantilevered end of first portion 122 of bellows 120 in a circumferential and longitudinal direction toward second portion 104 of lower tube support 30. An upper circumferential edge associated with second portion 124 of bellows 120 is sealingly secured to second portion 104 of lower tube support 30. Second portion 124 of bellows 120 has a generally serpentine cross-sectional shape whereas first portion 122 of bellows 120 has a generally planar tubular shape. The generally serpentine cross-sectional shape of first portion 122 of bellows 120 accommodates translation of second portion 104 of lower tube support 30 in a direction aligned with the longitudinal axis 24 of tubes 20, 22 relative to first portion 102 of lower tube support 30 during thermal expansion and contraction of tubes 20 during operation of fire tube heater assembly 10.

[0030] Said in another way and referring to FIGS. 3 and 4, longitudinally directed forces directed upon second portion 104 of lower tube support 30 associated with the thermal expansion and contraction of tubes 20 effectuates compression of second portion 124 of bellows 120 thereby translating second portion 124 of bellows 120 in a generally upward or downward axial direction relative to first portion 122 of bellows 120. Although first and second portions 102, 104 of lower tube support 20 are show as being generally contained in a common plane that is oriented generally transverse to the longitudinal direction associated with axis 24, it is appreciated that other relative orientations of first portion 102 and second portion 104 of lower tube support 30 are envisioned. It should be appreciated that the elongation or contraction, or changes to the axial length of tubes 20 during operation of fire tube heater assembly 10 is structurally accommodated by the movement a second portion 104 of lower tube support 30 relative to the first portion 102 of lower tube support 30 and the compression/expansion associated with second portion 124 of bellows 120. It is further appreciated that the generally transverse orientations associated with the interaction of tubes 20, 22 with the respective first and second portions 102, 104 of lower tube support 30 provide a robust sealed interaction between the plurality of tubes 20, 22 and lower tube support 30 in a manner that maintains the relative fluid isolation or segregation associated with the fluid flows such as the combustion gas flows associated with the internal volumes of tubes 20, 22 and the working fluid or heated fluid flows that generally surround the elongated surfaces of tubes 20, 22 within housing 12.

[0031] Lower tube support 30 includes a generally circumferential groove 130 that is formed between first portion 102 and second portion 104 of lower tube support 30 such that a volume 132 formed between first portion 122 and second portion 124 of bellows 120 can be occupied the heated fluid flow during operation of fire tube heater assembly 10 thereby maintaining a desired operating pressure associated with a pressurized side of fire tube heater assembly 10. A volume 140 that generally underlies second portion 104 of lower tube support 30 accommodates the passage of the combustion gases or heating fluid flow associated with the internal passages of tubes 20, supported by second portion 104 of lower tube support 30, between tubes 20, around baffle 120, and toward the radially outward oriented tubes 22.

[0032] Referring to FIGS. 2 and 4, each of a plurality of elongated slots 150, 152 associated with a respective one of first portion 102 and second portion 104 of lower tube support 30 are constructed to accommodate a secure sealed mechanical cooperation of a respective corresponding tube 20, 22 associated with fire tube heater assembly 10. Preferably, each of tubes 20, 22 is welded to a respective one of the first portion 102 and second portion 104 of lower tube support 30 such that the passages associated with each respective tube 20, 22 is fluidly connected to the volume associated with the opposing lateral side of lower tube support 30 via the respective opening or slot 150, 152 associated with lower tube support 30. It is appreciated that although tubes 20 have a generally elongate cross section shape and are oriented in a generally radially uniform pattern relative to a longitudinal axis of fire tube heater 10 and tubes 22 are oriented in a radially staggered pattern and such that the longitudinal cross section of each tube 22 is oriented as a crossing direction relative to the longitudinal axis associated with the cross section of the nearest radially inward tube 20 as indicated by slots 150 (FIG. 2) is only one exemplary arrangement of the orientation of tubes 20, 22.

[0033] Regardless of the discrete orientations of tubes 20 relative to tubes 22, and vice versa, it should be appreciated from FIG. 1 that the temperature associated with the heating fluid flow will decrease as it passes in a downward relative direction associated with tubes 20 and an upward relative direction associated with tubes 22 as the thermal energy associated therewith transfers to the working or heated fluid. It should further be appreciated that the temperature of the heated fluid will increase as the working or heated fluid passes in a radially inward direction and/or opposing longitudinal directions associated with the plurality of tubes 20, 22 and experiences a thermal exchange with the outer surfaces of the respective tubes 20, 22 and interacts with the respective baffles 120, 121 associated with directing the flow of working or heated fluid thereacross and through fire tube heater assembly 10.

[0034] The movable association of second portion 104 of lower tube support 30 relative to first portion 102 of lower tube support 30 accommodates changes to the longitudinal length of tubes 20 secured thereto in response to deviations associated with the operating load caused by the thermal expansion of the respective tubes 20 and/or 22. As should be appreciated, second portion 104 of lower tube plate 30 accommodates the elongation of a plurality of tubes 20 associated with operation of fire tube heater assembly 10. That is, rather than providing discrete tubes that are each individually tailored and constructed to accommodate the thermal elongation and/or contraction associated therewith, or providing a slidable association between discrete separate portions of housing 12, deformable lower tube support 30 facilitates a robust and secure tube mounting structure such that body 100 associated with lower tube support 30 accommodates deviations in the longitudinal length associated with the plurality of the respective tubes 20, 22 of fire tube heater assembly 10 caused by changes in the thermal loading associated therewith while maintaining of the desired fluid isolation between the combustion gas or heating fluid side or passages and the water or heated fluid side or passages associated with operation of fire tube heater assembly 10.

[0035] Referring to FIG. 6, the efficiency associated with the operation of fire tube heater assembly 10 can be affected by the heated fluid inlet flow rate and temperature. Efficiencies of approximately 96.5% to approximately 99.3% can be achieved during various heated fluid flow rater at heated fluid inlets flow temperatures of approximately 4.4 degrees Celsius (approximately 40 degrees Fahrenheit). The efficiency of operation of fire tube heater assembly 10 as well as the difference between the efficiencies associated with a minimum inlet heated fluid flow (indicated by trend A) and a maximum inlet heated fluid flow (indicated by trend B) gradually decreases as the inlet heated fluid flow temperature increases. As shown in FIG. 6, the efficiency associated with operation of fire tube heater assembly 10 can range from approximately 88.6% to 99.5% as the inlet heated fluid flow temperature ranges between the a lower input heated flow and higher input heated fluid flow and from temperatures of approximated 4.4 degrees Celsius to approximately 76.7 degrees Celsius (approximately 170 degrees Fahrenheit) and thereby provides an improved operating efficiency throughout the range of operation of similar fire tube heater assemblies. Fire tube heater assembly 10 is constructed to accommodate a range of on-demand throughputs from approximately 100% of the heated fluid throughputs to approximately 4% of the heated fluid throughout with a negligible deviation to the efficiency associated with fire tube heater assembly 10. Said in another way, the efficiency associated with operation of fire tube heater assembly 10 is maintained across the firing or on-demand operation of the assembly 10.

[0036] Those skilled in the art will appreciate that other advantages and features can be realized from the operating parameters associated with fire tube heater assembly 10 which are only exemplary of specific implementations of the present invention. While certain embodiments of the invention have been illustrated and described for purposes of the present disclosure, changes in the arrangement and construction of parts may be made by those skilled in the art and such changes are encompassed within the scope and spirit of the present invention as defined by the appended claims. The present invention has been described in terms of the preferred embodiment, the embodiment disclosed herein is directed to the assembly as generally shown in the drawings. It is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, to the embodiments summarized, or the embodiment shown in the drawings, are possible and within the scope of the appending claims. The appending claims cover all such alternatives and equivalents.