US2998807A

US2998807A - Water tube boiler or steam generator

Info

Publication number: US2998807A
Application number: US489060A
Authority: US
Inventors: Clarkson Alick; Donald W Miller
Original assignee: Vapor Heating Corp
Current assignee: Vapor Heating Corp
Priority date: 1955-02-18
Filing date: 1955-02-18
Publication date: 1961-09-05
Anticipated expiration: 1978-09-05
Also published as: DE1186876B

Description

Sept. 5, 1961 A. CLARKSON EI'AL 2,998,807

WATER TUBE BOILER 0R STEAM GENERATOR 4 Sheets-Sheet 1 Filed Feb. 18, 1955 ALICK CLABKSON DONALD W. MILLER Sept. 5, 1961 A. CLARKSON ET AL 2, 0

WATER TUBE BOILER 0R STEAM GENERATOR Filed Feb. 18, 1955 4 Sheets-Sheet 2 TIIIIIIIIJ "I IIIIIIII) ALICK CLAeKsoN DONALD W. MILLER P 1961 A. CLARKSON ETAL 2,998,807

WATER TUBE BOILER OR STEAM GENERATOR Filed Feb. 18, 1955 4 Sheets-Sheet 3 ALICK CLAEKSON DONALD W. MILLER Sept. 5, 1961 A. CLARKSON ET AL 2,998,807

WATER TUBE'BOILER OR STEAM GENERATOR 4 Sheets-Sheet 4 Filed Feb. 18, 1955 17251-2 243:5 ALICK CLABKSON DONALD W. MILLER United This invention relates to boilers and steam generators of the Water tube type and has for its principal object the provision of an improved water coil construction which will define the fire chamber of the boiler or steam generator and will insure a high degree of thermal efliciency to insure operating economy at both high and low fire operation.

A further object is to provide in a boiler of the above type a coiled water tube construction which in addition to providing [for high efliciency in heat transfer also provides a high degree of compactness, whereby the heat output from the boiler or steam generator, as. the case may be, will be relatively large for its size. In this connection the water heating coils are wound to provide a closed wall fire chamber having corrugated wall surfaces which induce high turbulence within the fire chamber and thereby insure more intimate mixing of the combustion air and gases to effect more perfect combustion of the fuel and insure recurrent wiping of the hot gases against the walls of the fire chamber to efiect maximum heat transfer.

The improved coil construction makes further provision for high turbulence in that the coil arrangement, in certain of the embodiments herein, which define the limits of the fire chamber also define a re-entrant path for the products of combustion, that is to say, a path in which the fuel and air mixture is introduced into the fire chamber in the form of a central core or jet and with sufiicient force to carry it to the opposite end wall of the chamber whereby its contact with the surrounding ignited gases and its impingement against said end wall causes the ignited products to return with a toroidal swirling movement along the corrugated side wall surfaces toward the inlet end or the fire chamber. This central core and the toroidal returning movement of the hot swirling gases are such that they are caused to traverse the entire length of the fire chamber at least twice and are repeatedly brought into wiping contact with the side wall surface of the fire chamber and are thrown back into revitalizing mixing engagement with the central core or jet of burning gases for recirculation and wall wiping engagement before they are discharged from the chamber into a surrounding heat transfer passage leading to the exhaust conduit of the boiler.

According to the present invention, close positioning of the adjacent convolutions of the water tubes in certain longitudinal regions of the boiler structure establishes, in effect, not only a generally cylindrical confining wall for the fire chamber in which the convexity of the tubes provide sinuous side and end walls for the fire chamber to increase the heat transfer area of said walls, but also establishes on the other or outside faces of the coils a similar solid outwardly facing generally cylindrical wall having a corrugated configuration and across which partially spent portions of the combustion gases are directed so that these gases are caused to give up turther heat to the water tubes prior to being discharged from the boiler, with the same high turbulence, effective wiping action and large heat-transfer area being maintained.

In the regions of the boiler where the combustion gases pass out of the fire chamber and are caused to reverse their direction to flow across the outwardly facing tates Patent surfaces of the closely positioned convolutions of the coils, an efiective spacing of the heat-transfer areas of a relatively large group of adjacent turns or convolutions is effected in such a manner that practically all of the available heat-transfer areas thereof are interposed directly in the path of moving hot gases while at the same time axial contiguity ot the adjacent convolutions or turns is maintained, thus increasing the overall number of turns that may be disposed within a given longitudinal boiler dimension.

The invention is susceptible to considerable modification and, in one particular form thereof, two groups or longitudinal extents of contiguous water tube convolulions are provided to give the solid wall effect described above, with one such wall expanse defining internally thereof the fire chamber proper and the other such wall expanse enclosing a group of coils which are efiective- 1y spaced in the manner previously outlined in the regions Where the combustion gases are caused to become reversed in their direction of flow. Additionally, a second group of efiectively spaced convolutions of a water tube coil are positionedwithin the boiler structure near the region where the combustion gases are discharged from the boiler shell and surround the first group of closely spaced on contiguous convolutions so that the outwardly presented surfaces of these lattter convolutions of this water tube coil constitute a barrier against reentry of the partially spent gases into the fire chamber proper while at the same time constraining these gases to flow against and around the second group of effectively spaced tu-be convolutions in maximum heat transfer relation with respect thereto.

In each ot the coil constructions shown "herein the serially arranged convolutions therof are soarrangedthat in general the flow of the water or other fluid to be heated or evaporated is opposed to the flow of combustion gases in order that maximum heat differential with consequent high heat transfer will take place'throughout the entire extent of the heat transferring surfaces associated with the boiler. With the direction of flow of the combustion gases opposed to the direction of flow Ofthfi fluid to be heated, the fluid entering the system at a relatively low temperature will come into heat transfer relation with gases which have previously delivered up heat but which are nevertheless sufficiently hot as to present a high heat differential. As the fluid progresses through the system it comes into heat transfer relation with progressively hotter gases until such time as it leaves the system when it then comes into contact with gases intially undergoing igntion in the fire chamber and which therefore are at their hottest state. By such an arrangement localized overheating at any region within the boiler, with its attendant disadvantages such as the creation of steam slugs within the tube coils, is eliminated.

Other objects and advantages of the invention, not at this time enumerated, will become more readily apparent as the nature of the invention is better'understood.

In the accompanying six sheets of drawings forming a part of this specification, several embodiments of the invention have been shown.

in thesedrawings:

FIG. 1 is a sectional view taken longitudinally and substantially centrally through a water tube boiler constructed in accordance with the principles of the present invention.

FIG. 2 is a sectional view taken substantially along the line 22 of FIG. 1.

FIG. 3 is a sectional view taken substantially along the line 3-3 of FIG. 1.

FIG. 4 is a sectional view taken substantially along the line 4--4 of FIG. 3.

FIG. 5 is a sectional view similar to FIG. 1 showing a modified form of water tube boiler structure.

FIG. 6 is a sectional view taken substantially along the line 66 of FIG. 5.

FIG. 7 is a sectional view taken substantially along the line 77 of FIG. 5, and

FIG. 8 is an enlarged fragmentary section taken on line 8-8 of FIG. 6.

Referring now to the drawings in detail and in particular to FIGS. 1 to 4- inclusive wherein there has been shown a horizontal boiler 10, including an outer casing or shell 11 of cylindrical design and having front and

rear plates

12 and 13 respectively. The rear plate 13 may be permanently secured in position on the shell 11 as by welding but the front plate 12 is removable and constitutes a support for a fire pot assembly 14 in which initial ignition of the fuel takes place and may also constitute a support for the burner unit (not shown) by means of which a liquid or a gaseous fuel may be introduced into the fire pot for subsequent complete combustion within the boiler fire chamber. The front plate 12 is attached to the boiler casing and the entire weight of this plate, together with the burner unit which it supports, is borne by the boiler casing and is transmitted thereto by means of split clamping members 15 of conventional construction. The fire pot 14 is of conventional design and comprises a cylindrical body 16 of refractory material such as fire clay contained within an annular casing 17 and the details thereof are not important insofar as the present invention is concerned except as part of a means for delivering a preregulated mixture of fuel and air into the fire chamber of the boiler in a manner that will be set forth presently through the fire pot opening or passage 18. An exhaust conduit 19 communicates with the interior of the casing 11 near the rear end thereof.

The fire chamber proper, previously referred to, is designated at 20 and exists solely by virtue of the provision of a water tube coil composed of a series of helically wound turns or convolutions which constitute part of a coil assembly 21, the latter of which extends from the front plate 12 axially rearwardly to a region adjacent the rear plate 13 with each intermediate helical turnin the series being contiguous to a pair of adjacent turns. As shown in FIG. 1, the first turn or convolution of the series communicates with a water inlet conduit 22 which enters the boiler shell through the plate 13 near the bottom thereof and which extends forwardly along the structure coextensively therewith. The next several turns or convolutions of the tubing (approximately fourteen as illustrated herein) are contiguous for the most part to each other axially along the series but the individual turns thereof are generally of polygonal configuration and are so arranged that a series of open spaces are provided between the adjacent turns, all in a manner and for a purpose that will appear presently. This group of polygonal turns is designated in its entirety at 23 and includes the first turn as well as a last turn which communicates with the first turn of a series of circular contiguously arranged convolutions or turns 26 (consisting of approximately eighteen turns) extending from the turn 25 to an end turn 27 of the coil assembly. The remaining tube turns 28 in the entire series 21 are spirally wound in radial alignment and the inermost turn thereof communicates with an outlet conduit 30 passing through the rear plate 13 and extending horizontally along the boiler axis. The group 28 of tube turns is partially embedded in a refractory material 31 of a header assembly 29 including a cup-shaped shell 32 which embraces the group 28 as well as the last turn or end coil 27 of the group 26.

The group 26 of contiguous helical circular turns and the group 28 of spiral turns, together with a limited portion of the header assembly, define the generally cylindrical fire chamber 20 by presenting what in effect amounts to a solid cylindrical wall surrounding the chamber and a similarly solid radial wall at the end of the chamber remote from the fire pct 14. These walls, since they are comprised of the exposed inner curved surfaces of the various tube turns of the groups 26 and 28, present a generally corrugated or sinuous heat transfer area having increased surface area over the usual smooth cylindrical surface presented in conventional boiler constructions, but what is equally important is the fact that these corrugated or sinuous surfaces permit what may aptly be called a wiping action by the highly turbulent end of the fire chamber 20 and caused to take a path back through the chamber to create toroidal swirls as shown by the arrows in FIG. 1 with portions thereof recurrently wiping against the inner faces of the contiguous tubes. In this manner any pockets of unburned gases are wiped clear of the surface of the tubes and are drawn back into the central core of combustion where they will comingle with the burning gases and become reheated and intermixed with vitalized fuel and air mixtures.

The influx of freshly ignited fuel and air in the chamber in the form of a central core or jet provides pressure which forces the products of combustion forwardly again in the combustion chamber and causes them to be directed against the group 23 of contiguous tubes which provide discharge passages by virtue of their polygonal configuration. As shown in FIG. 3, each turn or helical convolution in the group 23 includes substantially linear lengths 35 of the tubing which are connected together by obtuse bends 36, there being an even number of bends 36 for example four and an uneven number of linear tube lengths, for example four and one-half of the linear tube lengths 35 so that, axially along the group 23, the bends 36 and also the straightaway portions 35 are staggered thus creating a series of open spaces shown at 37 in FIGS. 1 and 4 between the contiguous tube turns through which the hot gases issuing from the combustion chamber 20 may pass. A cylindrical baffle or sleeve member 38 which may be formed of sheet metal surrounds a rear portion of the group 23 of tube turns and prevents short circuiting of the gases radially outwardly through the passages 37 and compels the gases to flow forwardly along the group 23 to the extreme front region of the boiler, after which these gases will become reversed and again flow rearwardly through an annular channel 39 defined by the cylindrical shell 11 and baffle 38. From the above description it will be seen that although the tube turns or convolutions in the group 23 are in contiguity, adequate flow spaces are provided so that the gases which pass forwardly through this group of turns between the bafile 38 and fire pot 14 will not be unduly restricted and intimate contact with substantially all of the surface areas of each turn is effected so that maximum heat transfer will be obtained.

From the annular channel 39 the gases move rearwardly along the inside surface of the cylindrical shell 11 and come into contact with the outwardly presented surfaces of the group of turns 26 where again a wiping action is obtained. Finally, the gases pass into the outlet conduit 30.

Although the various turns throughout the water tube coil may exist in their free state it is within the purview of the present invention that adjacent turns may be suitably secured together preferably by welding of the same at strategic regions, whereby adjacent turns of the tubing are in intimate heat contact relation with respect to each other as well as being firmly anchored to each other to lend rigidity to the structure as a whole. Where such welding is resorted to, in the group 23 of turns of polygonal configuration, it is obvious that the welded regions will ocur at the several straightaway length of the polygonal turns.

In the modified form of the invention shown in FIGS. 5, 6, 7 and 8 certain constructions are shown which correspond to the like construction of FIGS. 1, 2, 3 and 4, and are designated by the same reference characters with an exponent a? In this modified form, the boiler comprises a pair of concentrically arranged coils which are spaced apart to provide a passageway between them for the passage of gases of combustion from the fire chamber 20a to exhaust outlet 19a. The two coils are connected together so as to provide a continuous flow path for the liquid to be heated, leading from the inlet conduit 22:: through the various turns or helical convolutions of the outer and inner coils to the outlet conduit 30a. The inner coil defines the fire chamber 20a and is constructed in much the same fashion as the embodiment shown in FIGS. 1, 2, 3 and 4, in that it includes a group of helical turns 40 of polygonal configuration surrounding, but in spaced relation to the tire pot 140. Also there are a few more helical turns or convolutions in the group 40 than are shown in FIG. 1 and some of the passages 37a leading from the fire chamber 20a into the space 44 between the concentric coils are positioned inwardly from the discharge end of the fire pot 14a. The cylindrical baflle overlies the polygonal turns adjacent the inner end of the fire pot 14a so that the hot gases leaving the combustion chamber 20a are compeled to pass through the circuitous paths defined by the openings 37a between the tubes. The group 40 of polygonal turns connect with the group 41 of contiguous circular turns leading to the end group of the turns 28a and the outlet 30a.

The outer coil of the said embodiment shown in FIGS. 5, 6, 7 and 8 includes a group 42 of polygonal turns or convolutions which surround the group 41 of inner cylindrical turns forming a part of the inner coil of boiler. The group 42 of polygonal turns connect with a group 43 of cylindrical turns which surround the group 40 of polygonal turns forming a part of the inner coil.

The group 40 of polygonal turns, instead of comprising individual turns having four and one-half straightaway lengths 35, have three and one-half such lengths thereby effecting a lesser number of contact points between adjacent coils and also effecting wider, generally triangular passages 37a between the various adjacent turns. The group 42 consists of contiguous turns which are efiectively spaced in so far as their heat transfer surfaces are concerned by having the individual turns of generally polygonal configuration with each turn including four and one-half straightaway portions 35a and four obtuse arcuate portions 361: as in the case of the previously described group 23. The group 42 concentrically surrounds the group 41 in spaced relationship and the inner surface of the various convolutions thereof oppose the outer surfaces of the convolutions in the group 41 inasmuch as no bafiie is interposed between these two groups. The inlet conduit 22a communicates with the first convolutions in the group 42 and the last convolution in this group communicates with the first convolution in the .group 43. The last convolution in the group 43 communicates with the first coil in the group 40' while the last convolution in this latter group connects with the first convolution in the group 41. The last convolution in the group 4 1 corrrnunicates with the outermost turn in the radial group 38a and the innermost turn of this latter group communicates with the outlet conduit 30a.

The tube group 41, as previously indicated defines the fire chamber 20a and the turbulent gases of combustion within this chamber perform their wiping action on the inwardly presented solid wall corrugated surface of the tube group 41 and pass forwardly through the passages 37a existing between the adjacent turns of the tube group 40 in the manner described in connection with the form of the invention shown in FIG. 1. Thereafter these gases reverse their direction of flow and pass rearwardly within the boiler structure across the inner surfaces of the tube turns in the group 43 from whence they enter into the annular space 44 between the baffie 38a and the group of tube turns 40, thus giving up further heat to the tube turns of this latter group. Thereafter the combustion gases enter the spaces 37:: existing between the convolu- 6 tions of the group 42 and also pass through the additional spaces 45 existing between the convolutions of the two

groups

41 and 42 from whence they finally pass to the exhaust conduit 19.

In the form of the invention just described it will be obvious that in addition to the heat transfer effect attained in the form of the invention shown in FIG. 1, additional heat transfer operations are eiiected between the products of combustion and the exposed surfaces of the

tube groups

42 and 43. Since the flow of fluid to be heated through the water tube system is generally in a direction opposed to the flow of combustion gases through the various passages provided for it, the same phenomenon of maximum heat transfer between the gases and the fluid to be heated at each turn of the tubing along the system is maintained so that maximum boiler efficiency under conditions of either high or low fire will be effected.

We claim:

1. A boiler or steam generator including a tubular coil structure comprising a length of tubing wound into a helix having a fluid'inlet at one end and a fluid outlet at the other end and composed of a plurality of axially aligned groups of turns, one of said groups being composed of a plurality of turns disposed in contiguity to provide a closed wall portion of a combustion chamber and each turn of another group has a series of circumferentially spaced apart surface portions in contact with surface portions of adjacent turns and also has a series of other portions oiiset radially with respect to said contacting portions at spaced locations circumferentially along each turn to provide discharge passageways for hot gases of combustion from the closed wall portion of the helix.

2. A boiler or steam generator as defined in claim 1 characterized in that the said turns which provide said passageways are of polygonal configuration circumferentially and have their straightaway portions of the polygon misaligned lengthwise of the helix in relation to the straightaway portions of adjacent turns.

3. A boiler or steam generator as defined in claim 2 characterized by the provision of a baffle for surrounding a portion of said spaced apart turns to compel the combustion gases to follow an in and out circuitous path traversing a portion of said spaced apart turns.

4. A boiler or steam generator as defined in claim 3 characterized in that the tubular coil structure includes a second helix enclosing the first mentioned helix but spaced therefrom in concentric relation and cooperating therewith to define an annular space between them for the passage of hot combustion gases, the second helix having a fiuid inlet atone end connected with the outlet of the first mentioned helix and having a fluid outlet at its other end, and composed of a plurality of axially aligned group of turns one of said group comprising a plurality of contiguous turns providing a closed wall opposed to the group of polygonal turns of the first mentioned helix and having a group of turns having radially displaced portions opposed to the closed wall portion cf the first mentioned helix and providing passages for the discharge of gases from said annular space.

5. A boiler or steam generator as defined in claim 4 characterized in that the group of radially disposed turns of the second helix are of polygonal con-figuration circumferentially with the straightaway portions of the polygon being misaligned longitudinally of the helix to form said passageways for the discharge of combustion gases.

6. A boiler or steam generator as defined in claim 5 characterized in that the closed wall portion of the second helix surrounds said bafiie in spaced relation thereto, whereby the combustion gases pass between the battle and the second helix.

7. A boiler or steam generator as defined in claim 6 characterized in that a casing provided with a vent outlet surrounds said tubular coil structure in spaced relation theme and ecsperates with the outer helix to provide an annular space for the passage of combustion gases to 2,645,210

said vent outlet. 2,718,217

References Cited in the file of this patent UNITED STATES PATENTS 5 461,733

1,814,605 Mayr July 14, 1931 985,262

8 Harris et a1. July 14, 1953 Walter Sept. 20, 1955 FOREIGN PATENTS Canada Dec. 13, 1949 France Mar. 7, 1951