US2987305A

US2987305A - Methods of and apparatus for generating and transferring heat

Info

Publication number: US2987305A
Application number: US662796A
Authority: US
Inventors: Jr John V Calhoun
Original assignee: J V CALHOUN Co
Current assignee: J V CALHOUN Co
Priority date: 1957-05-31
Filing date: 1957-05-31
Publication date: 1961-06-06
Anticipated expiration: 1978-06-06

Description

N, JR 2,987,305

FOR GENERATING NG HEAT June 6, 1961 J. v. CALHOU METHODS OF AND APPAR AND TRANSFE 4 Sheets-Sheet 1 Filed May 31, 1957 June 6, 1961 J v. CALHOUN, JR 2,987,305

METHODS OF AND APPARATUS FOR GENERATING AND TRANSFERRING HEAT Flled May 31, 1957 4 Sheets-Sheet 2 'IIIIIIIIIIIIIIIII June 6, 1961 J. v. CALHOUN, JR

METHODS OF AND APPARATUS FOR GENERATING AND TRANSFERRING HEAT 4 Sheets-Sheet 3 Filed May 31, 1957 June 6, 1961 J. v. CALHOUN. JR

METHODS OF AND APPARATUS FOR GENERATING AND TRANSFERRING HEAT 4 Sheets-Sheet 4 Filed May 31, 1957 United States Patent Ofice 2,987,305 Patented June 6, 19 61 2,987,305 METHODS OF AND APPARATUS FOR GENERAT- ING AND TRANSFERRING HEAT John V. Calhoun, Jr., Stratford, Pa., assignor to J. V. Calhoun Company, Bala-Cynwyd, Pa., a corporation of Pennsylvania Filed May 31, 1 957, Ser. No. 662,796 16 Claims. (Cl. 2 63-6) This invention relates to methods of an apparatus for the internal heating of hollow cylinders.

Hollow cylinders in the form of drums, rollers and the like have for many years been used in many industries with heat applied interiorly thereof as by steam and other heating mediums. In some instances it has been proposed to place within the cylinder burners and to'burn fuel within the cylinder for heat transfer to the interior surface. Where fuel has been burned within the cylinder, the heat transfer rates have been relatively low because of several factors. First, there is inherently present adjacent the inner surface of the cylinder relatively dead air which in itself forms the principal heat insulator and reduces the rate of heat transfer. The withdrawal of the spent products of combustion represents a further problem and in the past has produced eddy currents and other flow of products of combustion in directions away from the interior surface of the cylinder.

In accordance with the present invention, high rates of heat transfer to the interior surface of hollow cylinders have been attained, transfer rates as high as 30,000 B.t.u.s per hour per square foot of said cylindrical surface. Such high rates of heat transfer have been accomplished by eliminating substantially entirely the dead air space adjacent the inner curved surface, the avoidance of any tendency of the flame and hot products of combustion to move away from the interior surface of the cylinder, and by the attainment of unexpectedly high efliciency in the COaIIEICCl'lOH transfer of heat from the gases to the cylinder w In carrying out the invention in one form thereof, a mixture of fuel and air is directed at high veloo yat an angle to the interior surface and insuch angular relation that as the pro-mixed fuel is burned, there are developed tangential forces fromthe expanding gases, and products of combustion which maintain them against the concave surface of the cylinder. The gases move alongthe curved surface of the cylinder in high-speed turbulent flow. By

reason of the high-speed flow and the constantly changing area wipedby the gases, any dead air space is eliminated to such degree that its eflfeetv on heat transfer is inconsequential. Further to increase the attainable rates of heat transfer, the cylinder is rotated so that itsjnner surface, moves in .counterllow with therapidly flowing products of combustion toproduce turbulent flow adjacent the curved surface. Further to maintain the high-speed curved path of the hot gases, there is provided an exhaust manifold having anjinlet means. spaced lengthwise of the roll and under substantial negative pressure. In this manner there are withdrawn through the exhaust manifold the gases .while {they are. disposed closely against the interior sur ac ofth h l ow y s {I'heyeylinder itself is-closed at its ends, and means are vprcwided ,forrelative adjustment of the locations of the exhaust manifold and burnerv so that the angular spacing maybe .uaried while maintaining the flow of gases in close of transfer.

, By rotating the hollow cylinder 10 in a clockwise direction For further objects and advantages of the invention, reference is to be had to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an isometric View of'an embodiment of the invention with supporting parts omitted;

FIG. 2 is a sectional view of the cylinder-heating arrangement of FIG. 1; i

FIG. 3 is a sectional view, taken on the line 33 of FIG. 2, of a preferred modification of the cylinder-heating apparatus;

FIG. 4 is a sectional view taken on the line 44 of FIG. 3;

FIG. 5 is a sectional view taken on the line 5-5 of FIG. '3;

FIG. 6 is an isometric view of a fractional part of the burner and associated apparatus; and

FIG. 7 diagrammatically illustrates a complete system of control of and operation of'the cylinder-heating apparatus. 1

Referring to FIG. 1, the invention in one form has been shown applied to a hollow cylinder 10 of the type which may be utilized for the drying of webs and sheet material of many kinds and character, the idler rollers and threading mechanism for such material having been omitted in order to simplify the drawings. Within the hollow cylinder 10 there is located a burner 11 having a plurality of openings 12 distributed lengthwise of the cylinder 10 and located in close proximity to the concave interior surface 10a. A mixture of fuel, preferably gas and air, under pressure, is introduced by way of supply line13. The premixed fuel flowsjto the burner by way of

pipes

14 and 15 into the burner manifold. After ignition, the burning p're-mixed fuel under pressure is directed angularly to ward the internal surface 10a. The angle 0 has been shown in FIG. 2 as between a radial line or plane 16 extended from the axis of the cylinder through a burner opening 12 and a line 1'7 coaxial of the opening 12. Thus, it will be seen that each opening 12 directs the burning fuel in the form of a jet 12a angularly toward the inner surface 10a. By reason of the angularity of the jets relative to the surface 10a, the initialpressure with which the pre-mixed fuel is released through the openings 12, and the forces developed by the expanding, burning gals, substantial tangential forces are developed tending to move the flame and products of combustion I upwardly and counterclockwise of the internal surface 10a as viewed in It has been found that if fuel underpressure be burned in the form of a plurality of angularly directed jets in the manner described, the forces resulting from the expansion of combustion gases developed as an incident tojthe burning of the fuel are substantial and are effective to move the combustion gases along and in intimate convective heat transfer with the interior surface 10a. In accordance with the present invention, the production of and the continual expansion of gases incident to the burning of fuel are so controlled, by means .of thedirected jets and the constantly changing curved surface 10a, that there is produced along and adjacent that surface 10a what appears to be a confined region for the flow of the combustion gases. As will now be explained, there is produced turbulent flow of the gases and products of combustion along the surface 10a. The products of combustion move in wiping engagement withjsurface 10a with'the elimination of the dead air blanket which would otherwise be as viewed in FIG; 2, i.e., in counterflow'with the directed streams of combustion gases, the heat ti'ansfer rate is further increasedand the periphery of the drum as a whole is elevated to high temperatures for application of heat "to webs and strip or sheet material of all kinds.

If the surface region a now be considered, the layer of gases adjacent that surface will be moving in a clockwise direction. These gases, as their forward velocity decreases, will exhibit a pressure change in respect to the forward moving gases. Thus, with some of the gases moving counterclockwise and some clockwise, there will be induced rotary motion or swirls which will extend along the surface 10a and will contribute to a high turbulent flow which is a condition desired and attained for maximum convection transfer to the cylinder wall by way of the surface 10a.

The length of the path of the force-directed flow of combustion gases is varied in accordance with the rate of firing of the fuel, assuming that air is always present in amount corresponding with the theoretical amount needed for complete combustion of the fuel. The provisions made for relative adjustment as between the burner 11 and a combustion withdrawing head 18 will be later described in detail.

The exhausting head or manifold 18 has suction applied to it to establish a region of low pressure in close proximity to the inner surface 10a and circumferentially spaced from the burner 11 for tangential withdrawal of the products of combustion while they are to some degree force-held against the internal surface 10a. In this manner, there is minimized any tendency of the products of combustion to move into the interior region of the cylinder 10 and thereby to create eddy currents which would interfere with the actions above described.

In addition to the forces developed by the expanding gases and the increasing velocity of the gases as a result of combustion of the fuel, there are other forces developed which contribute to the high heat transfer rates attainable in accordance with the invention. The expanding gases are, by the constraint imposed by the curved surface 10a, forced to move in a circular path. The result will be the development of centrifugal forces which areeifective on the gases, which do have mass, to move them toward and against the surface 10a. Thus, there is produced a thick moving blanket of hot products of combustion along the heat-transferring area between the burner 11 and exhaust manifold 18 which presses against a layer in turbulent flow in Contact with surface 10a. The several factors mutually contribute to the attainable high rates of heat transfer.

With fuel supplied at relatively high rate, it has been found that the exhaust manifold 18 may be located at least 180 away from the burner 11, and with still higher rates of combustion of fuel, the self-generated forces will be effective to maintain the gases in close proximity to the concave surface 10a through more than 270 of its area.

7 Typical operating data for one embodiment of the invention will be. later set forth.

Further in accordance with the invention, the rate of 7 fuel delivery from the burner 11 through the plurality of openings 12 is controlled lengthwise of the burner 11 for the production of a uniform temperature from one end of the roll to the other. More particularly, the burner openings, adjacent the respective ends of the cylinder,

' supply fuel at somewhat greater rates than the openings spaced from the ends.

In this manner, compensation 1s had for certain amount of heat loss near the respective ends of the cylinder. In practice it has been found that the temperature differential, taken along a line parallel to 7 enhanced. In connection with the indicated variation in temperature lengthwise of the roll, it is to be noted that 7 available measuring instruments are relatively inaccurate 7 "as applied to rotating surfaces, and thus it is believed fthatthe; uniformity of the temperature, notwithstanding J. the high rates, is considerably better than that indicated.

Contributing to the' uniformity .of temperature lengthwise of the roll 10 is the exhaust manifold 18, the entrance area of the inlet means 18a of which is adjusted for a uniform differential of pressure lengthwise of the roll modified at the ends, however, to take care of the greater rates of flow of fuel adjacent such end portions of the cylinder. This adjustment is desirable by reason of the additional fact that the exhaust pipe 19 is connected to the manifold 18 at a point nearer the left-hand end than the right-hand end, as viewed in FIG. 1. A suctionadjusting plate 32 fastened by a series of bolts 33 is provided with slots so that the plate 32 may be inclined at an angle for a greater area at the right-hand .portion of the suction opening 18a than at the left-hand end.

In the preferred form of the invention, as illustrated in FIG. 3, it will be noted that the suction plate 32' is provided with inclined

upper surfaces

32a and 32b which meet in the region of the exhaust pipe 19, thus to provide a minimum cross-sectional area for the suction opening 18a in the region of the pipe 19. The upper edge of plate 32 can be a curved surface if desired, though in practice it has been found that providing the angular shape of FIG. 3 will be satisfactory. Suction is applied to the manifold 18 by way of

pipes

19, 20 and 21. The pipe 21 is closed at its inner end and has extending therefrom a bearing 23 in the form of a hollow cylinder which encloses a stub shaft 22 carried by the inner closed end of the fuel supply pipe 14. This bearing 23 and external bearing means (not shown in FIG. 1) provide for the angular adjustment of the suction head 18 relative to the burner 11.

Externally of the cylinder 10, the pipe 21 terminates in an elbow 26, from which there extends a flexible length of pipe 27, such for example, as a flexible steam coupling. This flexible steam coupling is shown with a curved portion which provides needed length for rotation of pipe 21 and elbow 26 for angular adjustment of the exhaust manifold 18 relative to burner 11. In practice, a flexible length of pipe 27 may readily provide for an angular adjustment of the manifold 18 through at least 30, an amount adequate for most practical applications. Where a greater angular adjustment is desired, it may be facilitated as shown in FIG. 7 where pipe 21 nests within a second pipe 21b extending axially thereof as at 85b with suitable packing therebetween. With this arrangement, the manifold 18 may be moved to any angular position and without the limitation by the flexible length of pipe 27.

To cool the exhaust gases, an air inlet 30 and valve 30a admit air as a cooling fluid for mixture with the gases exhausted from the cylinder 10. The temperature requirements on the flexible pipe 27 and the subsequent disposal piping and associated equipment connected to the pipe 31 are reduced by admitting the cooling air to the exhaust gases shortly after leaving the cylinder 10.

7 Though not shown in FIG. 1, the branch inlet 30 includes rates.

a filter to prevent entry of any combustible matter into the hot combustion gases. In some applications the exhaust gases may be utilized as a by-product of the heating of the cylinder 10, since they are substantially oxygenjective of providing new methods and systems of generating and transferring heat by means of an internally heated cylinder or roll having exceptionally high heat transfer For example, in the preferred modification illustrated in FIGS. 3-6, it will be observed that the cylinder 10 is provided with a plurality of fins/35 whichare illustrated as ofwasher-like sha per Though they may be welded to the inner surface 10a, it is preferred that they be formed by machining and thus to be integral with the wall of the cylinder. The fins 35 perform a number of functions. First, they greatly increase the heat transfer area in contact with the hot products of combustion flowing between the burner 11 and the exhaust manifold 18. The fins 35 additionally subdivide the hot gases into a multiplicity of individual streams in the region of surface a with the overall blanket of rapidly moving gases superimposed above the subdivided streams.

While the heat transfer rates are extremely high in the regions of the surface 10a and of the fins 35,

annular slots

36 and 37 provide heat transfer barriers to decrease the flow of heat toward the supporting

heads

39 and 40. The

slots

36 and 37 are of greater importance in the ar rangement shown in FIG. 1 where there are not provided the flow-subdividing heat-transfer fins. In that modification, the hot products of combustion from the end-burner openings tend to expand along surface 10a and, accordingly, to transfer heat to the heads. In the modification of FIG. 3, the

slots

36 and 37 may be omitted, providing the burner openings 12 terminate short of the end-most fins. Thus, the end-most fins themselves establish heat barriers relative to the heads and act to prevent flow of gases endwise of the cylinder.

Because of the high rates of heat transfer and the great release of heat within the cylinder 10, provisions are made to minimize the temperature rise of the bearings, thereby to avoid the need of cooling fluid for such bearings. As shown in FIG. 3, the-cylinder 10 is journaled in bearings 41 and 42 carried by

supports

43 and 44. The

heads

39 and 40 have welded thereto

cylindrical journals

45 and 46. The journals are provided with closure members 45a and 46a. For purposes of increasing strength and rigidity of the heads 39 and 40 a plurality of

gusset plates

47 and 48 are welded to the

respective heads

39 and 40 and to thejournals 45 and 46. The subassemblies comprising the

journals

45 and 46, the

gusset plates

47 and 48, and the

heads

39 and 40 provide the needed strength to support the cylinder10 for rotation at any desired speed.

As best shown in FIGS. 3 and 4, openings 49 are provided between each of thegusset plates 47. These openings, besides lightening the subassembly, provide heattrausfer barriers, that is to say, they decrease the-crosssectional area of the path from which heat can flow from the periphery of the cylinder 10 toward the journal 45 andbearing 41.

Further toreduce the'transfer of heat readily inwardly from the periphery of drum 10, there are secured, FIGS. '3 and 5,'to*the' outer faceof the-head 39 aplurality of heat flingers-'50. 'Similar'heat flingers 51 are secured to the head 40, FIG. 5. Each array of fingers 50 and 51-is formed integrally with backing plates 52 and 53. As

shown inFIG. 5,'the heat flingers 51 are inclined with :respect'to radial lines and together form a fan-like structure-which produces flow of a large amount of air outwardly from the journal 46, FIG. 3, along the head 40. By thus, providing'for forced cooling of the head 40, the temperature of the journal 46 and of bearing 42, FIG. 3, is maintained within reasonable limits and within a range for whichthe bearing 42 may be'operated without the needofcooling fluid. In some instances, it may be desirable to. provide cooling fluid for the bearings. In such event, the features just described contribute to; a reduction ofthe amount of available cooling fluid which need be utilized, and thus such features are of advantage, either with or without cooling of the bearings.

Further contributing to the dissipation of heat is the selection of materials within the heat flow path. The

heads

39 and 40 and the

gusset plates

47 and 48 are preferably of a material havingalow heat-transfer coeflicient, such for example, asstainless steel, whereas the heatflingers 50 and 51 are-of a material having a high heat-transfer coeflicient, such for example, as aluminum.

Thus, in the multiplicity of heat-transfer pathsofhigh heat conductivity, there is a rapidly moving amount of cooling air to move the heat conducted thereto outwardly and away from the

journals

45 and 46. In contrast, the heat-transfer path to the

journals

45 and 46 is of low heat conductivity. In this connection, it will be noted that the

heat flingers

50 and 51 terminate short of the journal 46, FIG. 5, the annular space between their inner ends providing an inlet for the flow of air between them, that annular space being in close proximity with the journal 46 and providing substantial cooling thereof.

While it may be considered that the multiplicity of gusset plates 47 and .48 within the cylinder would tend to increase the flow of heat to the

journals

45 and 46 to a point which would indicate their omission, such is not the case. Aside from the required rigidity for the journal subassembly, the effective flow path for heat is sufliciently reduced and the cooling adequate for reasonably low operating temperatures for the bearings. Thus, an inspection of FIG. 4 reveals that in the region between adjacent holes 49 there is a greatly restricted cross-sectional area for flow of heat. In this region between adjacent openings, the flingers are moving a substantial amount of cool ing air to transfer from that region the heat conducted thereto. Accordingly, the

flingers

50 and 51 are securely fastened -to the

heads

39 and 40 in said regions between said openings 49 as by cap screws located within the aforesaid regions. These cap screws have not been shown in the drawings but extend through the heat flingers 51 on opposite sides of the location of the plates 47 and insure maximum rates of heat transfer from the heads to the heat flingers and the cooling air moving through them.

As indicated above, the suction manifold 18 and the burner 11 are angularly adjustable relative to each other to control the length and area of the flow path of gases against the inner surface 10a of cylinder 10. For angular adjustment of burner 11, there is included in the supply line 13, FIG. 3, for the pre-mixed fuel and air a length 13a of flexible pipe-coupling, such for example, as used in steam lines. The flexible coupling 13a permits rotation of the pipe assembly extending to and supporting the burner 11. As shown, the burner supply pipe 14 and the exhaust pipe 21 are provided with the bearing means 22 and 23 midway of the cylinder and also with supporting bearings 54 and 55. Preferably, clamping means 56and 57 in the form of set screws are provided in association with each of bearings 54 and 55 to hold in fixed angular position the burner 11 and the exhaust manifold 18. To simplify the construction and for the use of standard parts, it will be seen from FIG. 5 that the fuel supply line 14 extends in Off-center relation through the hollow journal 46. This provides the space needed for

conductors

69 and 61 and for a fuel supply line 62 which extends to a pilot burner'63. The offset relationship of pipe 14 is provided by an offset 14a as between the pipe 14 and the elbow 64. Another offset 65 in line 14 brings the T-fitting 66 to a position concentric with the cylinder and with the supporting bearings.

It is to be understood that the burner assembly and the exhaust manifold assembly may each be supported in cantilever fashion as by two external bearings, FIG. 7. If so used, the plug and socket bearings '22, 23 may be omitted.

Returning now to the burner assembly and referring particularly to FIG. 6, it will be observed that the fuel line 62 terminates at the pilot burner 63 which projects a flame 63a along one or more of the openings 12 of the burner 11. Included in the pilot burner 63 is an ignition device 67 sometimes referred to as a sparkplug. High-voltage current is supplied to the device 67 by way of

conductors

60, 69 and 68. The

conductors

60 and 69 are suitably insulated from their associated supporting structure as by ceramic spacers included in the supporting tube 70. To initiate operation, a control circuit (not shown) is closed to produce a spark within the pilot burner'63. 'This ignites the pre-mixed fuel'then flowing matically ignites in succession the streams of fuel issuing from the adjacent openings. It will be observed that the flame 63a from the pilot burner 63 impinges upon a flame rod 71, which flame rod is also disposed within the flame produced by the prc-mixed fuel issuing from one of the openings 12. The flame rod 71 is conventional. By change in itsresistance due to rise in temperature, a

1 safety circuit, including conductor 61 insulated by ceramic spacers, maintains open a fuel supply valve (such as valve 90, FIG. 7) and closes that valve upon flame failure.

' ,,For an understanding of additional control features forming a part of this invention, reference will now be had to the operation as a whole.

Referring now to FIG, 7, it will be assumed that a motor 80 is, through a sprocket 81 and chain 82, driving a sprocket 83 secured to the hollow journal 45 of the cylinder 10 for rotating "it at a selected speed. The motor 80 may be a variable speed motor, or the speed of drum 10 may be controlled through gears or other speed-changing mechanism.

With the cylinder 10 rotating at the speed desired for a web of paper or other material undergoing drying (such web being partially wrapped around the cylinder 10 and a section of which is shown at 10w), the pre-mixed fuel and air will enter by way of the fuel pipe 14 as previously explained.

In FIG. 7, instead of illustrating the flexible section of pipe as shown in FIG. 3, overlapping lengths of pipe as indicated at 85a are to be taken as symbolic of an airtight rotatable connection between pipe 14 and the supply pipe 14b. The pipe 14b includes a Venturi tube 86, and in conjunction with fuel mixing valve 87, of 35 conventional construction, adds fuel to the line 14b in fixed proportion to the rate of flow of air entering the Venturi as at the region 88. The fuel control valve 87 includes a connection 89 responsive to the pressure at the low-pressure section of the Venturi tube 86. As the flow of air through the Venturi tube increases, so does the amount of fuel supplied from the line 13. The valve 90 is a safety shut-01f valve which for the operation now being described will be considered fully open.

To simplify FIG 7, there have been omitted the pilot burner, the flame rod, and associated auxiliary control equipment which includes numerous interlocking circuits which do not affect the operations so long as the motors and equipment are functioning normally. Upon the failure of any significant component, the system will automatically shut down.

The flow of air to the Venturi tube 86 is provided by an air blower 93 provided with a filter 94 at the air inlet. The blower is driven by a motor 92. In the outlet line from the blower 93 a control valve 95 is utilized to vary the amount of air supplied to the burner 11. Though the air control valve 95 may be manually set to predetermine the rate of combustion within the cylinder 10, it has been illustrated as under the control of a thermocouple 96 responsive to the temperature of the cylinder at a selected location on its external surface. The external temperature of the cylinder varies with change in heat load imposed by web 10w.

The thermocouple 96 is included in a measuring circuit 97 of the potentiometer type and which includes a variable resistor or slidewire 98 and a detector 99 illustrated by the broken lines as driving a pen-index relative to a chart and associated scale of a recorder 100., The measuring circuit and indicator-recorder 100 may be of the type illustrated in Williams Patent No. 2,113,164, dated April 5, 1938. As the temperature of the external surface of the roll 10 changes, the thermocouple 96 will respond, and the detector 99 will not only move the penindex of the recorder 100, but through the mechanical connection 101 will adjust the movable contact 102a of,

an input potentiometer 103 for introducing an input signal to an amplifier 104 which controls the 'energization of a motor 105 to adjust the position of the control valve 95. Thus, the position of the movable contact 102 with respect to its associated slidewire will always be representative of the temperature as measured by thermocouple 96'. r :The amplifier 104 and the motor 105 are representative of control systems of the' type disclosed in Davis Patout No. 2,666,170, dated January'12, 1954, the input slidewire 102 corresponding with the slidewire 31 of that patent. It is to be noted that the control system as represented by the amplifier 104 includes proportional, rate and reset actions. It will be preferred that the reset 'and rate actions be set at relatively low'values for the reason that other adjustments can take place which may affect the positioning of the air control-valve 95. In this connection, it is to be noted that adjustment of the air control valve 95 effectively changes the fuel input to the cylinder 10. Accordingly, it is correct to say that the control system responsive to change in the temperature of thermocouple 96 directly regulates the fuel input to the cylinder 10. By functioning through and by means of the air control valve 95, it is likewise assured that increased or decreased amounts of fuel will be burned within the cylinder 10 with the proper amount of combustion air for 100% combustion.

While the temperature of the external convex surface of the cylinder 10 is measured at a single point, it is to be 0 remembered that the cylinder is rotated at relatively high A speed by the motor 80. Regardless of speed, the thermocouple 96 of the contact type measures the average temperature of the roll, which average temperature will be approximately thesame throughout the circumference for anygiven instant. It is preferred that the thermocouple 96, or other roll-temperature measuring device, be located within the combustion zone between the burner 11 and the exhaust manifold 18,, since. any change in the rate of tiring may be more quickly detected by the thermocouple. There will then be less lag in the control fimctions which have been partly set forth. It will now be assumed that the heat load imposed by e the web 10w on the heat-generating and transferring cylinder 10 is such that the air valve 95 is halfway between 'its maximum and minimum positions for producing a temperatureas measured by the thermocouple 96 at the set point. In order to have a numerical illustration, it will be assumed that the set point as established by a Y control-setter in amplifier l04 (suchas the control point 'setter'42 of the aforesaid Davis patent) will be 600 F., though it is to be understoodthe cylinder is capable of 'operation at temperatures as high as 1200 F. If the temperature decreases, the valve 95' will be opened a greater amount. Since there will be an increase in fuel delivery to the cylinder 10, it will be deslrable immediately to increase the angular separation between the burner 11 and the exhaust manifold 18. The increased separation, as already explained, will increase the amount ofheat transferred to the cylinder wall. Accordingly, 7 there is provided a control system for regulating the angularseparation between burner lland exhaust manifold 18. This system, like the one disclosed in the aforesaid Davis patent, includes an'input slidewire 112. A ,movable c0ntact 112a is adjus ted in response to change in the flow of air through the'line 88. A flow meter 113 is included in this line and through

mechanical connections

114, 115 drives, themovable contact 112a. Accordingly, the input signal to an amplifier 116 which coni trols'the energization'of a motor .117 has a magnitude [dependent upon the rate of flow of fuel to the cylinder 10. The motor'117, through a drive sprocket 120, a driving f chain 121, a;nd a sprocket 122, rotates the burner 11 about 'fthe axis of cylinder10 to change its angular position relative to the' e'xha'ust manifold '18 If,desired, there may be provided a mechanical connection from motor 117 as through the gears 123, a sprocket 124, a chain 125, and a sprocket 126 for rotating the exhaust manifold 18 about the axis of cylinder for concurrent adjustment to vary the angular separation between burner 11 and manifold 18.

It may here be observed that the fuel and air line 14 extends telescopically within fuel and air supply line 14b, the overlapping portion shown at 85a having suitable packing to prevent leakage. A similar arrangement is provided for the outlet or exhaust line 21 as indicated by the overlapping or telescopic relationship of the line 21 with the line 2111 as indicated at the region 85!). It is to be further noted that there is provided a pair of bearings for the

lines

14 and 21 so that the burner 11 and the manifold 18 are both cantilever-supported within cylinder 10.

While the arrangement of the lengths of flexible pipe as shown in FIG. 3 will be preferred, the present arrangement has been illustrated to indicate a. further modification. When flexible couplings are included to provide for the angular adjustment of the burner 11 and manifold 18, the limit switches of said Davis patent (as shown therein at 82 and 86) will be provided with each of them set for the respective limits of rotation for the burner and manifold.

By increasing the area of the heat-transferring surface with increase of'heat load on the cylinder 10 and as the fuel supply is increased to take care of that load, there will result a transfer of a greater amount of heat without substantial decrease in the efiiciency of operation of the system. More particularly, fora selected set point, for example, the aforesaid 600 F., there will be a dependent relation between various heat loads imposed upon the cylinder 10 and the angular separation between the burner 11and the exhaust manifold 18. For a 50% heat load, the separation distance will be made the optimum, i.e., for maximum efliciency in terms of heat input to the cylinder. The control 116 will thereafter vary the angular separation to maintain high efiiciencies with change in heat load in'either direction.

As fuel is'delivered to cylinder 10 at greater rate, the quantity of 'products of'combustion will increase and it will, accordingly, be desirable to increase the suction to the manifold 18, both to take account of the larger quantity of combustion products as well as the increased separation distance between burner 11 and suction manifold 18. Accordingly, as the heat load on the cylinder 10 is increased and there is a resultant change inrate of flow of fuel, as indicated by a change in the rate of flow of air as detected by the flow meter 113, a suction-controlling valve 130 is automatically positioned to increase the suction With increase of load and to decrease the suction with decreaseofload. This adjustment is made automatically bymeans of'a'motor 131 whose energization is under the control'of an amplifier 132 having in its 'input'c'ircuita slidewire 133 with its movable contact 13311 adjusted by way of the mechanical connection 114 extending from theliow m'e'ter113. In general, it will be preferred that the control system 131-132 (like that of the aforesaid Davis patent) be primarily a proportional system, i.e., one that sets minimum suction for a minimiim rate of fuel delivery to the cylinder 10 and maxi- 'mum suction for a maximum rate of fuel delivery to the cylinder 18.

The control system of said Davis patent also includes an adjustment for the extent of change of position of 'valve130 for a given change in output from the flow meter 113. Thus, the characteristics of a particular o1i the cylinder at widely differing set point temperatures.

In "some instances, it "may be desirable automatically to position the valve 30a in the cooling-air inlet line 30. In 'such event, a thermocouple 150 responsive to the products of combustion issuing from cylinder 10 can control the positioning of the valve by way of an amplifier 151 and a motor 152 which increases the opening of the valve with increase of temperature and reduces the opening of the valve with decrease of temperature. These provisions will be particularly desirable for the fully automatic system of control.

It is to be understood that in many applications it will be entirely satisfactory manually to set the angular relationship between burner 11 and exhaust manifold 18, and likewise manually to position the suction valve and the cooling-air inlet valve 300, since the load changes which may occur through long periods of operation may not be sufficiently great as to justify the expense of the added control equipment.

From the foregoing, it will be seen that the variablearea heat-transferring apparatus may be manually, automatically, or semi-automatically controlled, depending upon the requirements of particular applications. It is to be further understood that the electrical control mechanisms illustrated may be replaced by pneumatic control devices which are in general use in the combustion field. The amplifier and control motors have been illustrated as symbolic of conventional control mechanisms responsive to temperature and utilized for the positioning of valves and flow-controlling devices.

Where still higher rates of heat transfer are desired and for still higher temperatures, upwardly of about 900 F., it will be desirable to provide fluid-cooled supply lines for the pre-r'nixed fuel and air, since the temperatures within the cylinder will be quite high. In other Words, the fuel lines will be jacketed for circulation of cooling fluid to maintain the pre-mixed fuel and air below the combustion'point. By reason of the high heat transfer rates attainable, there is realized a considerable reduction in the number of drying rolls required for a given installation. For example, where 40 or 50 steam heated drying rolls are now required in paper making, the number may be reduced to 15 or 20 with a corresponding decrease in required floor space for a given paper-treating system.

In the preferred embodiment described above in connection with FIGS. 37, the cylinder had a diameter of 48", a length of 54". The cylinder rotated at 50 r.p'.m. It was this apparatus that has developed transfer rates as high as 30,000 B.t.u.s per hour per square foot of cylinder surface and at unexpectedly high efficiency, approaching 70%. The reference to each square foot of the cylinder surface is to the entire internal cylindrical surface and is not limited to the area of the concave surface over which the'hot combustion products flow. Where the requirements are for cylinders of still greater diameter, it is contemplated that additional burners and suction heads may be provided, each pair to operate over a difierent segment of internal concave surface, and each pair to be angularly adjustable as described above over its own Billocation of the curved heating member or cylinder.

What is claimed is:

1. The method of heating a hollow cylinder at rates not limited by the presence of an insulating layer of air between the internal curved surface of said cylinder and products of combustion within said cylinder, which comprises directing burning high velocity streams of premixed fuel and air at a substantial angle to the internal curved surface along'a path which is angularly displaced from a radius of said cylinder for development of substantial forward velocity of all of said burning fuel and air and in a zone extending lengthwise of the cylinder and in close proximity to said curved internal surface, constraining the flow path of the burning streams of premixed fuel and air along the curved inner surface of the cylinder, whereby the initial-velocity of said pre-mixed locity throughout a large circumferential area of the cylinder, applying suction across the arcuate path traversed by the products of combustion for withdrawing the products of combustion tangentially of said cylinder in a region extending lengthwise of said cylinder and adjacent said surface, and regulating the angular spacing between the points of initiation of said burning streams and said region of withdrawal in accordance with change in a variable affecting the transfer of heat to said cylinder.

2. The method of heating a hollow cylinder at rates not limited by the presence of an insulating layer of air between the internal curved surface of said cylinder and products of combustion within said cylinder, which comprises directing burning high velocity streams of premixed fuel and air at a substantial angle to the internal curved surface along a path which is angularly displaced from a radius of said cylinder for development of sub- 7 stantial forward velocity ofall of said burning fuel and air and in a zone extending lengthwise of the cylinder and in close proximity to said curved internal surface, constraining the flow path of the burning streams of premixed fuel and air along the curved inner surface of the cylinder, whereby the initial velocity of said pre-mixed fuel and air and the expansion of the gases incident to :tween the internal curved surface of said cylinder and products of combustion within said cylinder, which comprises directing burning high velocity streams of pre mixed fuel and air at a substantial angle to the internal curved surface along a path which is angularly displaced from a radius of said cylinder for development of substantial forward velocity of all of said burning fuel and air and in a zone extending lengthwise of the cylinder and in close proximity to said curved internal surface,

constraining the flow path of the burning streams of premixed fuel and air along the curved inner surface of the cylinder, whereby the initial velocity of said pre-mixed fuel and air and the expansion of the gases incident to the combustion thereof maintains the high initial velocity throughout a large circumferential area of the cylinder, applying suction across the arcuate path traversed by the products of combustion for withdrawing the products of combustion tangentially of said cylinder in a region extending lengthwise of said cylinder and adjacent said surface, concurrently regulating the angular spacing between the points of initiation of said burning streams and said region of withdrawal, and varying the suction pressure at the region of withdrawal in accordance with change in said flow of fuel and air. v

4. The method of heating a hollow cylinder at high rate I which comprises directing a plurality of streams of buming pre-mixed fuel and air along the length of the cylinder and in close proximity to the internal curved surface thereof and at an angle to said internal curved surface for developing tangentially directed forces to maintain the hot products of combustion along and in intimate contact with said internal curved surface, rotating said cylinder in a direction opposite to the directed travel path of said flame and hot products of combustion to increase the 7 rate of transfer by convection of heat to said hollow cylinder by way of the internal curved surface thereof, withdrawing tangentially of the cylinder the products of combustion in a region of reduced pressure and adjacent said inner curved surface, and regulating the spacing between'the points of initiation of said streams and said 12 region of low pressure to produce continuous flow of the products of combustion along said internal curved surface and thence into said region of low pressure.

5. The method of heating a hollow cylinder at rates not limited by the presence of an insulating layer of air between the internal surface of said cylinder and products of combustion within said cylinder, which comprises directing burning high velocity streams of pre-mixed fuel and air at a substantial angle to the inner surface along a path which is angularly displaced from a radius of said cylinder for development of substantial forward velocity of all of said burning fuel and air and in a zone extending lengthwise of said cylinder and in close proximity to said internal surface, constraining the flow path of the buming streams of pre-mixed fuel and air along the curved inner surface of the cylinder, whereby the initial velocity of said pre-mixed fuel and air and the expansion of the gases incident to the combustion thereof maintains the high initial velocity throughout a large circumferential area of the cylinder, rotating said cylinder to move said internal surface in counterflow to that of all of said products of combustion to produce a turbulent wiping and scrubbing action of said products of combustion against said surface, and applying suction for withdrawing the products of combustion tangentially of said cylinder in a region extending lengthwise of said cylinder and adjacent said surface.

6. The method of heating a hollow cylinder at rates not limited by the presence of an insulating layer of air between the curved inner surface and products of combustion within said cylinder, which comprises directing burning streams of pre-r'nixed fuel and air at a substantial angle to said curved inner surface along a path which is angularly displaced from a radius of said cylinder for development of substantial forward velocity of all of said burning fuel and air and in a zone extending lengthwise of the cylinder and in close proximity to said curved internal surface, constraining the flow path of the burning streams of pre-mixed fuel and air along said curved inner surface of the cylinder to develop centrifugal forces urging said combustion gases outwardly against said curved internal surface, the expansion of the gases incident to the combustion thereof maintaining a high velocity of said gases throughout a large circumferential area of the cylinder, rotating said cylinder to move said curved inner surface in counterflow to said products of combustion to cause the adjacent surface layer of said products of combustion to be in turbulent flow, and applying suction for withdrawing the products of combustion tangentially of said cylinder in a region extending lengthwise of said cylinder and adjacent said surface.

7. The method of heating a hollow cylinder at rates not limited by the presence of an insulating layer of air between the curved inner surface and products of combustion within said cylinder, which comprises directing burning streams of pre-mixed fuel and air at a substantial angle to said curved inner surface and in a zone extending lengthwise of the cylinder and in close proximity to said curved internal surface, constraining the flow path of the burning streams of pro-mixed fuel and air along said curved inner surface of the cylinder to develop centrifugal forces urging said combustion gases outwardly against said curved internal surface, the expansion of the gases incident to the combustion thereof maintaining a high velocity of said gases throughout a large circumferential area of the cylinder, rotating said cylinder to move said curved inner surface in counterflow to said products of combustion to cause the adjacent surface layer of said products of combustion to be in turbulent flow, applying suction for withdrawing the products of combustion tangentially of said cylinder in a region extending lengthwise of said cylinder and adjacent said surface, and regulating the angular spacing between the points of initiation of said burning streams and said region of withdrawal in accordance with change in flow of said fuel and air.

8. The method of heating a hollow cylinder at rates not limited by the presence of,an insulating layer of air between the curved inner surface and products of combustion within said cylinder, which comprises directing burning streams of pre-mixed fuel and air at a substantial angle to said curved inner surface along a path which is angularly displaced from a radial line of said member for development of substantial forward velocity of all of said burning fuel and air and in a zone extending lengthwise of the cylinder and in close proximity to said curved internal surface, constraining the flow path of the burning streams of pre-mixed fuel and air along said curved inner said gases throughout a large circumferential area of the cylinder, rotating said cylinder to move said curved inner surface in counterflow to all of said products of combustion to cause the adjacent surface layer of said products of combustion to be in turbulent fiow, applying suction for withdrawing the products of combustion tangentially of said cylinder ina region extending lengthwise of said cylinder and adjacent said surface, and varying the suction pressure at the region of withdrawal in accordance with change in flow of said fuel and air.

, 9,. Themethod of transferring heat to a load by way of the wall of a hollow cylinder at rates notlimited by the presence of an insulating layer of air between the curved inner surface and products of combustion within said cylinder, which comprises directing burning streams of pre-mixed fuel and air at a substantial angle to said curved inner surface along a path which is angularly displaced from a radial line of said member for development of substantial forward velocity of all of said burning ,fuel and air; and in a one extending lengthwise of the cylinder and in close proxiinity to said curved internal surface, constraining the flow path of the burning streams of pre-mixed fuel and air along said curved inner surface .of the, cylinder to develop centrifugal forces urging said combustion gases, outwardly against said curved internal surface, the expansion of the gases incident tothe combustion thereof maintaining a high velocity .of said gases throughout a large circumferential area ofthe cylinder,

rotating said cylinder to move said curved inner surface ,in counterflow to said products of combustion tocause the adjacent surface layerof said products of combustion to be in turbulent flow, applying suction for withdrawing 1 the products ofcombustion tangentially of said cylinder -in a region extending lengthwise of said cylinder and adjacent said surface, and concurrently regulating the angularspacing between the points of initiation of said burning strem and said region of withdrawal and the suction pressure at the region of withdrawal in accordance with changein heat load on said cylinder. {10. A heating system comprising a hollow cylinder,

in, fuel burner having a plurality of fuel-'directingjets ,disposed adjacent the concave internal surface of the cylinder and inclined at an angle with respect thereto for imparting to jets of burning pre-mixed fuel and air a large tangential velocity in the region in whichthe burning ,pre-mixed fuel ,and air impinges upon said surface, an exhaust manifoldwith inlet means distributed along and adjacent said surface, said inlet means dis- 'posed generally tangentially of said cylinder and facing toward said jets for flow tangentially therein of the prodnets of combustion moving along said concave surface,

end;closure members for said cylinder each including a headvhaving a circular array of openings spaced in- I and having, aplurality of air-impeller elements extending outwardly from said plate for producing a flow of air between the impeller plates and in heat exchange with said plate and said head,said heat flin'gers terminating in spaced relation with said journals for producing a flow of air alongv said journals and into and along the space between saidheat flingers.

11. A heating system comprising a hollow cylinder, a fuel burner having a plurality of fuel-directing jets disposed adjacent the concave internal surface of the cylinder and inclined at an angle with respect thereto for imparting 'tojets of burning premixed fuel and air a large tange'ntial velocity in the region in which the burning pr s-mixed fuel and air impinges upon said surface, an exhaust manifold with inlet means distributed along and adjacent said, surface, said inlet means disposed generally tangentially of said cylinder and facing toward said jets 'for flow tangentially therein of the products of combustion moving along said concave surface, rotary support-iii'gmeans for rotation of said cylinder about its longitudinal axis, means for rotating said cylinder, a supplypipe for said fuel burner'displaced from said longitudinal axis and extending through said rotary supporting means, said supply pipe within said cylinder having an offset, a T-fitting connected to said offset portion of said supply pipe and located coaxially of said cylinder, said exit passage being coaxial with said cylinder and including a pipe having structureadjacent one end thereof forming withstructure carried by said T-fitting a bearing, and means for bodily rotating with respect to each other said fuelburner and said exhaust manifold.

12. A system "of heating a hollow cylinder for transfer of heat through the wall thereof to a heat load, which comprises a fuel burner, means for supplying said fuel .ducing flow of said'products of combustion at substantial velocity in intimate heat exchange with said internal surface, means for rotating said cylinder in a direction counter to the flow of said products of combustion for inducing a multiplicity of eddy currents and swirls within the region adjacent said internal surface to increase the ,rate ofheat transfer thereto, said angular disposition of said fuel jets and saidcurved inner suiface giving rise to centrifugal'force's, applying to said swirls and eddy currents forces which tend to maintain them in intimate contact with said inner surface, an exhaust manifold with inlet means distributed lengthwise of said cylinder and adjacent said internal surface of said cylinder, said inlet means disposed generally tangentially of said cylinder and facing toward said jets for flow of said products of combustion into said manifold adjacent said surface, means for applying suction to said manifold for forced flow of combustion products therein and for development of forces tending to maintain the flow of said combustion gases along said inner surface, and means respo'nsive to the heat load for adjusting said angular separation in accordance with change in said heat load.

13.,A system of heating a hollow cylinder for transfer of heat through the wall thereof to a heat load, which comprises a fuel burner, means for supplying said fuel burner with 'pre-mixedfuel and combustion air, said burner having a plurality of fuel-directing jets disposed lengthwise of the cylinder and adjacent the internal surrection counter to the flow of said products of combustio 'for inducing a multiplicity of eddy currents and swirls cylinder and facing toward said jets for flow of said products of combustion into said manifold adjacent said surface, means for applying suction to said manifold for forced flow of combustion products therein and for development of forces tending to maintain the flow of said combustion gases along said inner surface, means for relatively adjusting the angular separation between said fuel burner and said exhaust manifold, and means responsive to the heat load for adjusting said angular separation in accordance with change in said heat load and for concurrently adjusting the suction applied to said manifold for developing maximum heat transfer for a given rate of fuel supply to said burner.

14. A system of heating a hollow cylinder for transfer of heat through the wall thereof to a heat load, which comprises a fuel burner, means for supplying said fuel burner with pre-mixed fuel and combustion air, said burner having a plurality of fuel-directing jets disposed lengthwise of the cylinder and adjacent the internal surface thereof and inclined at an angle for producing along said internal surface flow of burning fuel and hot products of combustion, the combustion of said pre-mixed fuel producing flow of said products of combustion at substantial velocity in intimate heat exchange with said internal surface, means for rotating said cylinder ina direction counter to the flow of said products of combustion for inducing a multiplicity of eddy currents and swirls within the region adjacent said internal surface to increase 'the rate of heat transfer thereto, said angular disposition of said fuel jets and said curved inner surface giving rise to centrifugal forces applying to said swirls and eddy cur- ,rents forces which tend to maintain them in intimate contact with said inner surface, an exhaust manifold with inlet means distributed lengthwise of said cylinder and adjacent said internal surface of said cylinder, said inlet means disposed generally tangentially of said cylinder and facing toward said jetsfor flow of said products of combustion into said manifold adjacent said surface, means for applying suction to said manifold for forced flow of 1 vcombustion products therein. and for development of forces tending to maintain the flow of said combustion y gases along said inner surface, means for relatively adjusting the angular separation between said fuel burner and said exhaust manifold, and means for adjusting the area'of the internal surface in contact with said hot products of combustion in accordance with the magnitude of 7 the flow of fuel to said burner and for increasing said area with increase in said magnitude and for decreasing said-area with decrease of said magnitude.

15. A system of heating a hollow cylinder for transfer of heat through the wall thereof to a heat load, which comprises a fuel burner, means for supplying said fuel burner with pre-mixed fuel and combustion air, said burner having a plurality of fuel-directing jets disposed length- .wise of the cylinder and adjacent the internal surface thereof and inclined at an angle for producing along said velocity in intimate heat exchange with said internal surface, means for rotating said cylinder in a direction counter to the flow of said products of combustion for inducing a multiplicity of eddy currents and swirls within the region adjacent said internal surface to increase the rate of heat transfer thereto, said angular disposition of said fuel jets and said curved inner surface giving rise to centrifugal forces applying to said swirls and eddy currents forces which tend to maintain them in intimate contact with said inner surface, an exhaust manifold with inlet means distributed lengthwise of said cylinder and adjacent said internal surface of said cylinder, said inlet means disposed generally tangentially of said cylinder and facing toward said jets for flow of said products of combustion into said manifold adjacent said surface, means for applying suction to said manifold for forced flow of combustion products therein and for development of forces tending to maintain the flow of said combustion gases along said inner surface, control means responsive toa temperature at a selected location on said cylinder for controlling said fuel supply means to increase the rate of fuel supply with decrease of temperature and for decreasing said rate of fuel supply with increase in said temperature, and control means responsive to said change in said rate of said fuel supply for concurrently varying the area of said internal surface over which said hot products of combustion flow in heat transfer therewith to increase said area with increase in said rate of fuel supply and to decrease said area with decrease in said rate of fuel supply.

16. Heat-transfer means comprising a hollow cylinder, means for heating at least a portion of the internal surface of said hollow cylinder at rates not limited by the presence of an insulating layer of air between the internal curved surface of said cylinder and products of combustion within said cylinder comprising a fuel burner for directing burning high velocity streams of pro-mixed fuel and air at a substantial angle to the internal curved surface of said cylinder along a path which is angularly displaced from a radius of said cylinder for development of' substantial forward velocity of all of said burning fuel and air and in a zone extending lengthwise of the cylinder and in close proximity to its said curved internal surface, said cylinder constraining the flow path ofthe burning streams of pre-mixed fuel and air along said curved inner surface whereby the initial velocity of said pre-mixed fuel and air and the expansion of the gases incident to the combustion thereof maintains the high initial velocity throughout a large circumferential area of the cylinder, means including a suction head extending across the armate path traversed by the products of combustion for applying suction for withdrawal of the products of combustion tangentially of said cylinder in a region extending lengthwise of said cylinder and adjacent said surface, and means responsive to a change in a variable affecting said rate of transfer of heat to said cylinder, said means including pivotal mounting structure, for relatively angularly-changing the separation distance between said fuel tel burner and said suction head to regulate the site of the area over which there is a high rate of transfer of heat to said cylinder..

References Cited in the file of patent UNITED STATES PATENTS 1,240,468 Martin Sept. 18, 1917 1,704,875' Vaughn Mar. 12, 1929 1,768,777 Moller 'July l, 1930 1,945,273 Hetzer Jan. 30, 1934 2,521,371 Hornbostel Sept. 5,1950 2,764,232 Johns Sept. 25, 1956