AU631177B2 - Apparatus and process for generating radiant energy - Google Patents

Description

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C~i- i -li CII-LL--- COMMONWEALTH OF AUSTRALIA Patents Act 1952 COMPLETE SPECIFICAT ION

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Class Int. Class Application Number Lodged Complete Specification Lodged Accepted Published WX 11 7 Priority 28 March 1989 Related Art 00 00 0 0 0 0o o00 0 0 0000 o 0 0 0 000ooo0 0 0000 Name of Applicant -WIlL-IE -H--JESTI- Itc\Ia- h Sc~r ~Z k i Address of Applicant Actual Inventor (5) 0000 000 00° Address for Service 00 0 0 oo 3aaoc0 fL 0,0v- 'bV-k \I-C 8C The Heritage, Columbia-; -South Carolina, United Statesof- Amer-ica-->i Willie H. Besti F.B. RICE CO., Patent Attorneys 28A Montague Street BALMAIN NSW 2041 Complete Specification for the invention entitled: o 0 o.0.o APPARATUS AND PROCESS FOR GENERATING RADIANT ENERGY The following statement is a full description of this invention including the best method of performing it known to iXS/me:- BACKGROUND OF THE INVENTION 1i. Field of the Invention This invention relates to an apparatus and process for generating radiant energy, and is more particularly concerned with a radiant wall structure employed in an industrial oven.

The structure includes a radiant wall, the temperature profile of which can be varied along selected areas, by increasing or decreasing the velocity of heated gases passing throuyh a combustion chamber.

00 0 2. Description of the Prior Art 00 o Various means have been utilized in the past to 00000o *I 0 0 generate radiant energy for use, for example, in industrial 00 0 o[&S ovens to cure coatings. In the conventional design of heated air ovens, it has been a common practice to provide the heated air for the oven from an external heater house containing a burner, and which utilized a fan to recirculate the heated air to and from the oven. These heater houses were interconnected to the oven with supply and return air ducts. When incinerators ore used in conjunction with conventional ovens to oxidize the volatile organic compounds (VOC's) which are S generated in the drying (curing) process, the incinerators are also interconnected to the ovens with external air ducts. In most instances, these ducts to and from the heater houses and/or the incinerator must be insulated. This duct work and I Iii -he heater houses or incinerators occupy valuable space within the manufacturing facility. The external heater houses and associated duct work increase the mass of the oven that must be heated on each heat-up cycle of the oven. This increases the time from when the oven is started to when it is ready for use. On each cycle of the oven, the energy that is consumed in heating the mass of the oven is lost to the environment during the period the oven cools down. The external duct work and heater houses also increase the exposed surface area of the oven, therefore increasing the transmission losses. Not only is this lost energy costly, but often this necessitates the 00oo Co 0 0 operation of additional, costly air conditioning apparatus to 0oo So remove this wasted heat from the work environment.

oooooo 00. In many applications of ovens using external heater 0oo 0015 houses, the recirculating fans operate at a high level of 00ooo0 noise, which adversely impacts the working environment. The recirculating fans used in the external heater houses require "00 extensive maintenance and consume large quantities of energy.

0000 oooo It is common for each recirculating fan in large oven installations, such as those used in the automotive and truck industry, to require fan motors of 25 horsepower and larger.

In a large installation of conventional ovens using heater 0 0o houses, a typical cost of electric energy to drive the recirculating fans is estimated to be in excess of approximately $500.00 per day, or more than approximately $100,000.00 per year. The recirculating fans and the inherent -3disadvantage of their use is eliminated by the present invention. Also, all external or remote heater houses and associated duct work is eliminated by the structure disclosed herein.

A means for generating radiant energy is disclosed in my U.S. Patent No. 4,546,553, for a Radiant Wall Oven and Proceso of Drying Coated Objects. This oven generates radiant energy by igniting a combustible fuel mixture behind the radiant wall, and employing a series of propeller fans to direct the heated gases within a chamber against the radiant wall. The heated gases within the chamber are in a turbulent 00 0 0 0 condition, and therefore, the radiant wall is heated oo 0 0 substantially uniformly throughout its entire surface area.

0 0 00. While this oven provides an efficient and reliable means for drying coated objects, it is practically impossible to 0 0.3 selectively vary the radiant energy emitted by different portions of the wall. Further, the fans which direct the heated gases against the radiant wall have many of the inherent o o disadvantages previously discussed.

Con ve CAOfr) In my U.S. Patent No. 4,785,552 for aAConvntic-n Q 0 0 0 00 Stabilized Radiant Oven, I disclose an oven in which radiant emitter walls emit radiant energy within a drying chamber, accomplishing highly efficient heat transfer by infra-red radiation. Overhead fans circulate the air within the drying chamber to control the equilibrium temperature of the surface of the object in the oven, and to minimize the variation of the -4- .Ir i-

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temperature distribution in the oven. To generate the radiant energy, a separate furnace utilizing a gas burner assembly is disposed adjacent to the oven. Blowers force heated gas from the furnace through ducts and into outer plenum cavities. The heated gas is directed under pressure through nozzles, and impinges on the inner surface of a radiant emitter wall. While the temperature of the entire radiant emitter wall can be selectively controlled, there is no means to controlled the radiant energy emitted by selected portions of the wall.

Further, the separate furnace and its associated duct work and fans also necessarily incorporate the disadvantages previously discussed.

0 0 0 on o o o o, 0 Q1 03 0 0 0 0 0 f C O 0 0 0 00 0 00125 0 Oo o o 0 0 0010 o o a o f o* 0 0 0 SUMMARY OF THE INVENTION Briefly described, the present invention includes an apparatus, namely a radiant wall structure having a pair of spaced walls forming a combustion chamber between their respective inner sides. The first wall or radiant emitter wall 1 V~'L l L I 1 4 1 L~ I rT rr about a horizontal axis. The outer side of the radiant itter wall (radiant wall) is preferably coated with igh emissivity material. The second wall is also c ilinear, and is spaced o 00 0 0 0 from the inner side of the iant wall, at various distances along their resp ive vertical dimensions or increments. The combusichamber formed between the radiant wall and the secnodn-,-all i-s further de--iR--by-a b-tt- f-l--a.-u-pt-fe-a- 1 ff *I J1^ r 74 0zo 6 is curvilinear, being continuously concave along its exterior side and curving about a horizontal axis. The exterior side of the radiant emitter wall (radiant wall) is preferably coated with a high emissivity material. The second wall is also preferably curvilinear, and is spaced from the interior side of the radiant wall at various distances along their respective vertical dimensions or increments. The combustion chamber formed between the radiant wall and the second wall may be further defined by a bottom wall and upstanding side walls. A longitudinally extending exhaust duct is preferably disposed along the o top of the walls, defining an exhaust aperture. Disposed o on the bottom wall along the length of the combustion chamber is a means for providing heated gases which may be o 15 in the form of a line burner which ignites a combustible 0 fuel mixture and delivers heated gases upwardly between 0.0 the spaced walls. The heated gas impinges on the radiant wall, transfers energy to the radiant wall in the form of 0 9 2 heat. Since this energy is partially dependent upon the velocity of the heated gases contacting the wall, by varying the velocity of the gases contacting various increments of the radiant wall, the energy transferred to that increment of the wall can be selectively controlled.

The radiant energy emitted from the radiant wall can therefore, likewise, be controlled in this manner.

The velocity of the heated gases contacting the radiant wall is controlled by incrementally varying the distance between the first and second walls, thereby changing the cross-sectional area of the combustion chamber. The energy transferred to the radiant wall can also be controlled by altering the vertical and horizontal position of the burner within the combustion chamber, and by the inclusion of baffles or vanes within the combustion chamber. The radiant energy emitted by the radiant wall can be varied using cascade plates mounted to the outer side of the emitter wall. An exhaust fan Ao0i reiviOve- Scommunicating with the exhaust apertureAEeome':cE the heated exhaust gases from the upper portion of the combustion chamber.

IL use -Ae ~e 4 radiant wall directs radiant energy toward a vertical plane spaced outwardly from and running the length of the radiant wall. Using the above-described invention, the radiant energy emitted along the vertical dimension of the radiant wall can be selectively controlled. No fans, external heater houses or duct work are needed to deliver the energy to prefere b ly the radiant wall, only an exhaust fan isAused to remove gases.

Another advantage of the oven of this invention is that the ra diaIrL shape of theAemitter wall can be changed to accommodate the o a o processed object. As an example, there are usually heavier Smembers in the floor of a truck or automobile body than in the side walls and the emitting wall can be extended in the 00 0115 direction of the center line of the oven at the bottom to concentrate additional energy on the heavier members. Also on the lower portion, a more curved wall (shorter radius) toward 0 the center line of the oven can be used in combination with the burner location to concentrate the radiation intensity around 4 0 20 and under the processed object such as a truck or automobile 04 O0 00 body.

0 0 0 0 a o rr In another embodiment, an aperture is provided in the (o lower portion of the radiant wall to allow the air in front of the radiant wall to be drawn by the exhaust fan into the lower portion of the combustion chamber. In this area, any VOC's in i i 1_ LU~IY IIEIt~L~ 1CI~ -Y1 i the air are incinerated, and the products of incineration are exhausted. While incineration of the exhaust gases is desirable in some applications, it should be understood that the majority of the VOC's expelled during the coatings process does not occur in the ovens. Most of the VOC's evaporate during the spraying of the coatings and while the coatings are allowed flash time prior to entering the oven. Previous investigations have revealed that less than 10% of the VOC's are evaporated in the oven. However, because of the misconception that most of the VOC's are discharged into the oven, most ovens are over-exhausted. This practice contributes 0 greatly to the w,te of energy. When too much exhaust is used and incineration is required, the energy required for the i incineration can exceed the required energy of the oven.

Unless there is another use for this excess energy, it is lost oo ,I to the atmosphere. In order for all VOC's to be oxidized, they ,j must reach their 'auto' ignition temperature. Most VOC's will oxidize at about 1250 0 F at a dwell time of 7/10's seconds.

oo However, in order to be sure that all of the VOC's are I 6°20 oxidized, incineration temperatures up to 1450 0 F are used.

The oven of this invention can incinerate a normal exhaust rate for most coatings operation without a sacrifice in ni efficiency. Tests and studies by me have shown that the oven iof this invention can incinerate exhaust rates up to 30 SCFM per foot of oven for most coatings applications. Higher exhaust rates can be accommodated if the heat load to the oven -8h6 II1..LI-~ i .1I^ I .I exceeds about 33,000 Btu/Hr./Ft. of oven. However, if the exhaust rate is increased to the point where the energy required for incineration exceeds the energy input of the oven, then the excess energy has to be discharged from the oven.

Just as when a conventional incinerator is used, this excess energy can be used in other processes, but a means has to be provided to expel this energy from the oven or the oven would overheat beyond its control temperature. The ofiest- simples+ method to deal with this problem with thie oven of this invention is to increase the distance between the radiant wall and the second .e-or4i4 wall. This lowers the velocity of the o~ i G gases and allows them to be discharged at a higher 0 temperature. In other words, the efficiency of the heat o transfer system is deliberately decreased to deal with the excess energy due to incineration of excess exhaust rates.

0 Other methods of dealing with this problem would involve a means such as a separate exhaust duct communicating with the combustion chamber, to bleed the exhaust gases out of the combustion chamber after incineration has occurred. If the radiant wall temperature reached an overheated condition, a ,0 00 'blower attached to the separate exhaust duct would bleed more of the exhaust gases from the combustion chamber, therefore o decreasing the amount of energy to be given up to the radiant wall.

In most applications, the energy required for incineration of the exhaust will be less than the required energy of th -i oven and the incineration is accomplished as a -9c- 1~1 by-product of the basic heating system of the oven with little or no increase in the cost of energy and very little increase in the cost of the equipment. In conventional systems, the incinerator is a separate piece of capital equipment that is in addition to the cost of the oven. It would not be uncommon for incineration and associated duct work and equipment to add more than $400 in cost per foot of oven to ovens with exhaust gas incineration.

In another embodiment, the radiant wall structure is incorporated into an oven housing so that a heating chamber exists between the second wall and the respective oven housing j side wall. An exhaust port defined by a duct passing °transversely through the combustion chamber exhaust duct, %,%permits air from in front of the radiant wall to pass into the o 1j,5°heating chamber. This air passes downwardly through the 000 heating chamber where it is heated by convection from the second wall. The air then passes through an aperture in the 00 obottom wall of the heating chamber and then into lower portion o 0o of the combustion chamber. Any VOC's contained in this air are incinerated by the burner in the combustion chamber, and the 0 00 products of combustion are then exhausted.

In another embodiment, a fresh air duct extends 0 00 downwardly within the heating chamber, then passes through the second wall and the radiant wall, and terminates defining an open port in the area in front of the radiant wall, or the drying chamber. A fresh air inlet defined along the bottom of i i -I r O the oven housing side wall permits fresh air to enter the heating chamber, where the fresh air is drawn upwardly through the heating chamber and preheated. The heated ai then forced downwardly through the fresh air duct in the heating chamber, and into the drying chamber, outwardly from the bottom portion of the radiant wall, to add preheated make-up air to the drying chamber.

In another embodiment, while exhaust gases from the drying chamber are circulated through an exhaust gas heating chamber and into the combustion chamber for incineration, fresh make-up air is simultaneously forced through a fresh air duct oo nJ o running downwardly through a fresh air heating chamber and into 00 the drying chamber. Both fresh air and exhaust gases are 00ooo0o00 .oo simultaneously preheated in this manner, while being segregated 0, °o35) to avoid contamination of the fresh make-up air.

,O00 In still another embodiment, a radiant wall structure is installed in an existing, conventional industrial oven in order to convert only a portion of the oven to include a 0 0oooo 00oo radiant zone. In many applications of convection ovens, it is O0 r 020. desirable to convert a portion of the oven to a radiant zone.

0o0 0 In recent years, increased importance has been placed on the quality of the finish on automobiles and trucks. A major 0 00 0o"" contributing factor in improved paint quality is the elimination of dirt or foreign particles in the cured coating.

It has been established that the dirt and foreign particles in coatings can be greatly reduced or eliminated by not exposing -11- 12 an oo oo o on ocr eoone o e 1~ o oo oo 1 ~r-in no a a 0 oa 0 a r i o a 0 r a o eo 0011;3 00

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the wet coating to an environment in which there is forced air movement. Therefore it is desirable and widely practiced to set the coating to a tack-free condition in a radiant zone before the object is introduced to a heat transfer process involving forced air movement.

Accordingly, in one broad form the present invention provides an apparatus for generating radiant energy, 0 comprising: S a continuously concave first wall for emitting radiant heat; a second wall adjacent to and spaced from said first wall; means for closing the end portions of said first wall and said second wall, for defining, with said first 15 wall and said second wall, a chamber; means for providing heated gases for movement along a path of travel through said chamber and for heating said first wall; the cross-sectional area of said chamber varying 20 along said path of travel for varying the velocity of said gases moving in said chamber to thereby vary the amount of heat delivered to increments of said first wall.

Another broad form of the present invention provides a process for providing radiant heat comprising: disposing a radiant wall in a position in which one surface thereof, when the radiant wall is heated, will emit radiant energy; passing a heated gas along the outer surface of said radiant wall for heating respective increments of said radiant wall wall sufficiently for said one surface to emit said radiant energy; and changing the velocity of said gas contacting said increments of said radiant wall to thereby vary the amounts of heat respectively delivered to said increments.

A further broad form of the present invention provides a radiant wall structure, comprising:

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aras~- rra~;uslrur~ 13 a continuously concave radiant emitting wall having a concave exterior radiant energy emitting surface and a convex interior surface; a second wall spaced a distance from the interior surface of said radiant emitting wall for defining a combustion chamber therebetween; and heating means disposed within said combustion chamber for delivering heated gas in a direction through i said combustion chamber, and imparting heat to said radiant emitting wall whereby the distance between said radiant emitting wall and said second wall is selectively varied to vary the velocity of said heated gases to i thereby vary temperature along said radiant emitting wall.

A still further broad form of the present invention ~o 0 15 provides a process for directing radiant energy from a 0o0 radiant wall structure inclilding a radiant wall having a continuously convex inner surface and a continously concave outer surface and a second wall spaced from the I 0: inner surface of said radiant wall for defining a 20 combustion chamber therebetween, comprising: 00 generating heated gases by igniting a combustible fuel mixture; 0:00: delivering said heated gases against the inner surface of said radiant wall; and selectively varying the cross-sectional area of 1 the combustion chamber, whereby the velocity of said Sheated gases delivered against said radiant wall is I thereby varied.

i~~ 13a- Another broad form of the present invention provides a radiant wall structure comprising an arcuate radiant wall having a continously convex inner surface and a continously concave outer surface and directing radiant energy outwardly from said outer surface, a second wall in spaced relationship to the inner surface of said radiant wall, said radiant wall and said second wall defining a ,passageway through which air is passed, means for directing air through said passageway and heating means disposed in said passageway for heating or w~ a n a 04 00 a nrl

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a r i ~'I"i 'jr r i idii-; b D~ 14 said air as said air is directed through said passageway, the distance between incremental portions of said radiant wall and said second wall varying along said passageway, the variation and distance between increments of said radiant wall and increments of said second wall being sufficient to vary the velocity of the air passing between such increments for thereby altering the velocity of said air with respect to the successive increments so that said air will deliver varying amounts of radiant energy along the surface of said radiant wall as said air changes in rvelocity.

o Furthermore, the present invention provides an oven icomprising: o a housing having a pair of opposed housing side 015 walls defining an oper interior whereby successive objects can be moved through said open interior along a path; a pair of spaced, opposed radiant emitter walls o disposed within said interior of said housing and on opposite eides of said path for defining a longitudinally extending drying chamber with an entrance end and a end, each of the radiant emitter walls having an exterior surface facing the path and an interior surface; 0 0.0o 0 a first wall spaced from the interior surface of one of said radiant emitter walls for defining a first combustion chamber therebetween; a second wall spaced from the interior surface of the other said radiant emitter wall for defining a second combustion chamber therebetween; and heating means disposed in said first and said second combustion chambers for heating said radiant emitter walls for causing said radiant emitter walls to emit sufficient radiant energy inwardly toward said open interior to heat said objects as they pass along the path through said open interior, wherein the temperature gradient along the vertical dimension of said radiant 4 14a emitter walls can be selectively varied by adjusting the distance between each radiant emitter wall and the respective wall which is spaced from the interior surface of that radiant emitter wall.

Other features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings wherein like characters of reference designate corresponding parts through the several views.

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O i t ]l ii BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of an industrial oven incorporating opposed radiant wall structure of the present invention.

Figure 2 is a cross-sectional view of the radiant wall structure illustrated in Fig. 1.

.0 Figure 3 is a cross-sectional, schematized view of another embodiment of the radiant wall structure.

00 .0 0o 0 0 0~ 0 0 o0oo another 0- .0000 Figure 4 is a cross-sectional, schematized view of embodiment of the radiant wall structure.

Figure 5 is a cross-sectional, schematized view of another embodiment of the radiant wall structure.

a a 0 0 0 o Qo another 0 0 t o o a o a Figure 6 is a cross-sectional, schematized view of embodiment of the radiant wall structure.

Figure 6A is a vertical sectional view taken 0 go substantially along line 6A-6A in Fig. 6.

Figure 7 is a cross-sectional, schematized view of another embodiment of the radiant wall structure.

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Figure 8 is a cross-sectional, schematized view of another embodiment of the radiant wall structure.

Figure 8A is a vertical, sectional view taken substantially along line 8A-8A in Fig. 8.

Figure 9 is a cross-sectional, schematized view of another embodiment of a radiant wall structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 00 00 0 0 0 0 Referring now in detail to the embodiments chosen for 00 illustrating the present invention, Fig. 1 depicts an inverted, 0000oooo00o .000 U-shaped oven housing 10 having opposed, spaced upstanding oven a* 0 ol5oside walls 11, which support a horizontal oven top wall 12.

f 000 Oven side walls 11 and top wall 12 are preferably constructed of abutting panels 13 of sheet metal and are joined along their 0o0Oo appropriate edges to form oven side walls 11 and oven top wall 0090 °0 12. Oven housing 10 also preferably includes entrance 00 0 20 vestibule 14 and exit vestibule 15 which are also inverted, U-shaped or channel-shaped members, but each of a smaller dimension than housing 10. The structure of housing 10 and 0 00 00o" vestibules 14 and 15 are known in the art, and disclosed in my previous patents listed above, as well as my U.S. Patent No. 4,235,023 and my U.S. Patent No. 4,426,792. The particular -16- L- a. i -1 i ~-~rc~~PLUilr~yix*Uc__r_ <j shape of housing 10 is not critical, and shapes other than the rectangular housing 10, as shown in Fig. 1, may be employed.

Invented housing 10 and vestibules 14 and 15 define an unobstructed passageway 16 therethrough. The oven housing may include an oven bottom wall 17 which joins the bottom edges of respective side walls 11. Otherwise, oven bottom wall 17 can be eliminated, and the lower edges of side walls 11 can rest on the floor. A conveyor (not shown) can be provided through oven housing 10 to pass objects through passageway 16 to be processed, as is taught in my U.S. Patent No. 4,426,792.

Mounted within passageway 16 of oven housing 10 along o 00 each side wall 11 are a pair of spaced, upstanding, opposed S radiant wall assemblies 20. As shown in Fig. 1, radiant wall 000000oooooo Soooo assemblies 20 are mounted along side walls 11 so as to define o 5, an unobstructed drying chamber 21 therebetween.

0000 Fig. 2 shows one radiant wall assembly 20 in partial cross-section. Each assembly 20 extends vertically from bottom o 0 00 o, wall 17 to top wall 12, and horizontally the entire length of 0000 o0 o housing 10 along respective side wall 11. Radiant wall 0020, assembly 20 includes a radiant emitting first wall or radiant 0 00 wall 22. Radiant wall 22 has a vertical, flat, lower portion 23 and an upstanding curvilinear portion 24 which curves about 0 00 0"00 horizontal axis Z. Radiant wall 22 is substantially concave along its outer side 25 and is constructed of individual panels 26, assembled along their respective edges by any commonly known means, such as that taught in my prior U.S. Patent -17- No. 4,546,553 and U.S. Patent No. 4,785,552, taking into account considerations such as thermal expansion and contraction, as is well known in the art.

Assembly 20 also includes a second, upstanding ox torkior wall 27 spaced eutw.ardly4 from,-ae-d radiant wall 22 and curving about axis Z at a different curvature from that of wall 22, as shown in Fig. 2, so that a tubular combustion chamber 28 is created therebetween. In the embodiment shown in Fig. 2, apart walls 22 and 27 are spaced. tGwutardly from one another a greater distance along their lower end portions, and curve about axis Z so that they are spaced at a lesser distance at Stheir upper end portions. The cross-sectional area of 0 °combustion chamber 28 therefore decreases in the upward vertical direction from wall 17. Assembly 20 includes bottom ov 29 and upstanding side walls (not shown) at each end which close the ends of combustion chamber 28.

The respective upper ends of walls 22 and 27 terminate in spaced relationship, defining longitudinal exhaust port Exhaust port 30 communicates along its entire length with the ,420, bottom wall 31 of exhaust assembly 32. Exhaust assembly 32 is 0 0 of a conventional type, well known in the art, and includes elongate exhaust duct 33 which extends the entire length of walls 22 and 27. Exhaust duct 33 defines ambient exhaust apertures 34 along side wall 35 in spaced relationship allowing communication of drying chamber 21 with exhaust chamber 36, defined by exhaust duct 33. Apertures 34 can be covered with a .E -18-

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i mechanism such as slidable door or louvre (not shown), to selectively regulate the air drawn through each aperture 34 21 from the drying chamberAinto exhaust duct 33, as discussed herein.

Vertical exhaust duct 37 joins exhaust duct 33, passing through top wall 12 and communicating with the low pressure intake side of centrifugal exhaust fan 38. It is readily understood, therefore, that the operation of exhaust fan 38 will pull air from both drying chamber 21 through apertures 34, as well as from combustion chamber 28 through exhaust port 0 0 o Disposed along bottom wall 29 of assembly 20 is line Co ,burner assembly or burner 40. Burner 40 can be of any known, 0 0 conventional line burners, provided that proper input controls o a and air/gas manifolds are incorporated, as is well known in the art. For the most efficient operation, however, the present invention performs optimumly when the burner assembly of my o" 0 .die4ng U.S. Patent appli-cation Szrial No.252 is o°"'outilized. When this burner assembly is employed, many 020 advantages are realized over using a conventional line burner, 00 0 04 as is hereinafter discussed. The present invention, however, is operable when other gas line burners are used.

In operation, burner assembly 40 is ignited to burn an air/fuel mixture which delivers heated gases along a path of travel upwardly through combustion chamber 28. As the heated gases contact radiant wall 22, energy in the form of heat is -19transferred to wall 22 along the entire surface of wall 22.

Radiant energy, as is indicated by arrows 38, is then directed outwardly from radiant wall 22 toward vertical plane P in drying chamber 21.

The gases from the burner 40 are at their highest temperature as they exit the burner surface. The energy that is transferred to the wall 22, at any point or increment of wall 22, is dependent upon the velocity and the temperature of the gases along the surface at that increment. Therefore, when the gas is at its maximum temperature, which is at the bottom increment of wall 22, the flow area in combustion chamber 28 is o o o 0 more open because of the increased distance between walls 0 0 0 0022 and 27. As the heated gas rises within chamber 28, the 0 0 temperature of the gas contained between walls 22 and 27 olo decreases. The flow area of chamber 28 controlled by dimension o is also decreased, which increases the gas velocity to maintain the desired surface temperature on the corresponding increment of wall 22. Therefore, the temperature of increments of radiant wall 22 can be varied in its vertical dimension by varying the dimension d between walls 22 and 27. This feature 0 0 is extremely beneficial in that it provides a method to improve the uniform distribution of the radiant flux density in the b 0.0 vertical dimension of the drying chamber 21, and also provides a method to concentrate more energy at a desired position in chamber 21, when required.

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Referring to Fig. 2, if plane P represents the surface I at which the radiant energy emitted by wall 22 is absorbed, for the same radiation emission level for all surfaces of wall 22, point will absorb more energy than either points or As indicated by arrows 38, point would receive the normal radiation in addition to angular radiation from the top and bottom increments of wall 22. Points and will receive the normal radiation from the wall, but will received the angular radiation from only one direction. The development of a radiant wall structure 20 of the present invention provides a means to improve the distribution of the radiant o.energy at the absorbing plane by increasing the emission otemperature in the lower increments of wall 22 and decreasing 0 .a.te emission temperature in the center increments of wall 22, l8tIen increasing the temperature at the top increments of wall oa;a2. Therefore, by selectively varying the distance between i' walls 22 and 27, thereby varying the cross-sectional area of combustion chamber 28, the velocity of the heated gases ooimpacting wall 22 is also selectively varied, By this method of varying dimension the amount of energy transferred to S 'wall 22, and the amount of radiant energy emitted from wall 22 towards plane can be selectively controlled along any increment of wall 22.

As an additional control of the energy transferred to 25 wall 22, baffles 41 are mounted to the inner side of wall 27 within combustion chamber 28. Baffles 41 are flat, planar, -21- ICI1Cl__i___Cil____~ X1elongate members of sheet metal which are hingedly connected Salong one edge 42 to wall 27, with the opposite edge 43 extending toward radiant wall 22, but spaced therefrom. These baffles 41 have the effect of forcing the hot gases onto wall 22 at the desired increment, for temperature variation. When the baffle 41 is nearly horizontal, or when edge 43 is at its closest distance to wall 22, radiant wall 22 is heated to a higher level at the position of baffle 41. When the baffle 41 is angled upwardly from wall 27, the temperature on wall 22 at tiiat position is decreased. The baffles 41 can be arranged to be mechanically actuated for selective biasing to a desired "position. Such actuation means (not shown), such as a rod S, linkage, are well known in the art and, as is further well Sknown in the art, could be electronically controlled by means responds to a signal from either an electronic controller °6c from a temperature sensor along wall 22. This would cause baffles 41 to change their orientation automatically, depending upon process requirements.

0 °o Fig. 3 illustrates in schematized form a second of a radiant wall assembly 120. In this embodiment, oheat is concentrated on the lower increments of radiant wall 122, and is decreased in the middle increments of wall 122.

This is accomplished by selectively converging walls 122 and 127 where it is required to concentrate the heat, and then 25 diverging the walls 122 and 127 at their upper increments. Th.

velocity of the heated gases from burner 140 is increased at -22s- C _1111-r-.the lower, converging increments of walls 122 and 127, and is decreased as the walls 122 and 127 diverge, thus increasing then decreasing the heat transferred to wall 122. Walls 122 and 127 terminate in spaced relationship at their uppermost ends and connect to duct 133 to define exhaust port 130. Duct 133 in turn interconnects, via duct 137, to exhaust fan 138.

In this embodiment, no preheating of any make-up air is required, nor is there any requirement to incinerate the exhaust gases from drying chamber 121. Therefore, the exhaust gases from drying chamber 121 enter directly into duct 133 through spaced, ambient exhaust apertures 134, and are thereafter exhausted by fan 138. To further confine the heat o o of combustion in chamber 128 to radiant wall 122, the space 144 0 0 ocreated between the second wall 127 and the oven side wall 111 j59° 0 can be insulated. This embodiment of the invention ideally would be used where it would be required to concentrate higher levels of radiant flux density at the lower elevation of the oo""i°odrying chamber 121. This is desirable in an application, for "o0 °example, of drying coatings on the frame of a truck body, in heavy members are located near the floor of the oven.

oo A third embodiment is shown in Fig. 4, and utilizes two separate burner assemblies 240 and 250, adjacent to one another. Burner assembly 240, by the natural flow of the gases, provides more heat toward the bottom increments of wall 222. Burner assembly 250, by natural convection, provides most of the energy from its products of combustion from the bottom -23- IU( llrr- third of wall 222, upwardly. A partition (not shown), can be incorporated between the burners 240 and 250 to further segregate the hot gases.

Burner assembly 250 cou'd also be elevated above bottom wall 229 and burner assembly 240, as shown in phantom lines. In this situation, an elevated burner assembly 250 would direct its hot gases of combustion toward the upper z4-O increments of wall 222, above assembly 4 Since the BTU/hr.

input to burners 240 and 250 can be controlled independently, it is possible to actually control both the vertical So, incremental temperature of the emitter wall 222 as well as the 0O o 0 0 oo temperature along the horizontal dimension of wall 222 from two Sso..c~different positions. Controlling the temperature of the o radiant wall along either the vertical or the horizontal 3"'dimension of the radiant wall by selectively varying the input to the respective sections of the line burner, can be accomplished in all embodiments of the present invention disclosed herein. Although it is commonly knownthat separate ooo oburner input can be accomplished when using conventional line S 2G: burners, this requires much redundant burner structure. The burner assembly of my pending application Serial No. 295,264, 0 much more efficiently controls burner input. However, in most i 0 applications, it will not be necessary to actually control the j vertical incremental temperature of wall 222 from two different positions, but to simply rely upon the fact that a greater proportion of the energy released by the burner 240 nearest to -24r the wall 222, will affect the radiant wall 222 surface temperature more on the lower increments of the wall 222. An embodiment incorporating two or more burners would be used in situations where the requirerents of an industrial oven would be such that the vertical height would be greater than ordinary. Such would be the case in providing an industrial oven to process large objects such as off-road machinery. In this embodiment, it would be highly desirable to insulate the space 244 created between wall 227 and oven wall 211. The obvious reason being that in this embodiment as much energy should be converted to infra-red radiat in from wall 222 as o 0 possible. Because of outside dilution air entei -uch a large oven through its entrance and exit vestibules, it is 0 0 0 "odifficult to raise the ambient temperature in the oven drying I" chamber 221 very much, because of the large open ends that are required to accommodate large objects.

This embodiment also incorporates cascade plates 251 o hingedly connected along one edge 252 to the concave surface Q '225 of radiant wall 222, and extending outwardly into drying chamber 221. For a fixed horizontal and vertical position of o 0 o either or both of burners 240 or 250 between walls 222 and 227, and at fixed dimension at any point between walls 222 and o o0 226, the emission temperature of the wall 222 can be varied on its surface by the installation of cascade plates 251. These plates decrease the convective energy that is absorbed from wall 222. Any number of plates 251 can be used to control the r ar prat convective energy that is absorbed from wall 222. Also, the width of the plates 251 has an affect on the convective heat transfer (forced or free). The cascade plate 251 is preferably made from a material with a reflective surface, such as stainless steel.

Fig. 5 illustrates a fourth embodiment utilized when the requirements of the curing process do not require preheating of the oven's make-up air, and the VOC's in the exhaust gases in drying chamber 321 are to be directly incinerated by the heat of combustion from burner 340. The S o drying chamber's 321 exhaust gases are introduced directly into 0 0 o the combustion chamber 328 above the burner assembly 340. The oo.negative pressure created within the chamber 328 by the fan 338 0 0 O a"a causes a controlled amount of the exhaust gases to be brought into chamber 328 through spaced, exhaust gas inlet ports 355, having louvres 356, to be incinerated. The incinerated exhaust gases and VOC's, along with the products of combustion from o burner 340, enter duct 333 which ultimately interconnects to °t 0 ^exhaust fan 338. Tests have shown that complete oxidation of the VOC's can be accomplished within 10" to 14" from the surface of the burner 340, depending on the distance 'd' a between walls 322 and 327. A separate exhaust duct is 0| eliminated by this method of incineration.

In this embodiment, the cascade plates 351 can be selectively used, depending upon the emitter temperature requirements. Also, directional vanes, such as %anes 357 and -26-

L

S358, may be selectively used. The directional vanes 357 and 358 are identical elongate, flat plates, hingedly connected at one edge 359 to a zi'pport linkage (no' shown) and supported within combustion chamber 328. The vanes 357 and 358 can be selectively biased in the same manner as baffles 43, previously discussed. The temperature of the surfaces of wall 322 can be varied by the directional vanes 357 and 358. As vane 357 is shown positioned in the direction of the gas flow, the temperature on the surface of the wall 322 immediately above the vane 357 is lowered. When a vane is positioned in the 0: direction opposite to the gas flow, such as vane 358, the 0 00 temperature of the wall 322 is increased immediately below and oat the elevation of the vane 358. Vanes 357 and 358 can be fixed or can be variable by a turning mechanism, also as o o discussed above with reference to baffles 43. In this embodiment of the invention, the cavity 344 formed by the wall 327 and the oven exterior wall 311 could be packed with insulation. However, the oven wall 311 itself usually contains 4" to 8" of insulation, and in some applications additional insulation would not be required.

In a fifth embodiment, provision is made to preheat the exhaust gases from drying chamber 421 prior to introduction 00 0 of gases into combustion chamber 428 for incineration of the VOC's. A series of spaced, transversely extending ducts 434 defined above longitudinal exhaust du, t 433 permit communication of drying chamber 421 with heating chamber 444.

V Bftos -27rr-- i- r, il--i'~-TCC-~=LiiCii;;__ Heating chamber 444 is defined by second wall 427, oven side wall 411, and bottom wall 429, and is closed at each end by upstanding end walls (not shown). Transverse ducts 434 are spaced above the length of radiant wall assembly 420 to allow a 4-21 free flow of exhaust gases along the drying chamberA4-a8 -to enter heating chamber 444.

In this embodiment, the heated gases from burner assembly 440 impinge on wall 422 as in the previous embodiments. Heating chamber 444, however, cannot be filled with insulation, which is an option in the previous embodiments. The heated gases from burner 440 also impinge on o exterior wall 427 which becomes thereby heated, and which also o oemits radiant energy into chamber 444 to heat the inner side 0 0 o- 460 of oven side wall 411. The products of combustion from o0 0 cJ5S 0 assembly 440 are exhausted through duct 437, as in prior ooo embodiments. Heating chamber 444 includes bottom wall 461 which is spaced above wall 429 to create a chamber 462 o o therebetween, which communicates directly with the lower o portion of combustion chamber 428, as shown in Fig. 6. Wall 461 further defines a series of spaced ports or orifices 463 therein, to allow communication of heating chamber 444 with chamber 462. Orifices 463 provide a pressure drop to ensure 0 0 into combustion chamber 428. Alternatively, ports 463 can instead be defined by wall 427 just above the height of burner -28- 9T 0 i assembly 440, to introduce the heated gases directly into combustion chamber 428.

The negative pressure imparted by the exhaust assembly (not shown) connected to exhaust duct 437 as in the prior embodiments, additionally pulls exhaust gas from drying chamber 421, through transverse ducts 434 and into heating chamber 444. The exhaust gases are preheated in chamber 444 by convection from walls 427 and 460 before they are drawn through orifices 463, into chamber 462 and then into combustion chamber 428 at or just above burner assembly 440. The VOC's in the exhaust gases are then incinerated by burner assembly 440, and 0 0 So the products of combustion are exhausted. By preheating the ,exhaust gases prior to incineration, a greater volume of VOC's 0 o .oo. can be incinerated than would be achieved when the exhaust 00 0 0 5 9 gases are not preheated.

o 0 0 i A sixth embodiment is employed in situations where it is desirable to provide controlled, preheated make-up air to the drying chamber 521. Combustion chamber 528 is formed o between radiant wall 522 and second wall 527, and as in the first embodiment, the products of combustion from burner o o o assembly 540 are exhausted through elongate port 530 by an exhaust assembly (not shown). Ports 534 are spaced along 0 00 o o 0 00 longitudinally extending exhaust duct 533 to permit the VOC's contained in the exhaust gases of drying chamber 521 to be directly exhausted, also through ducts 533 and 537.

-29- 1- ~I I 1 Fresh air inlet ports 565 are defined by the lower portion of oven side wall 511 and spaced along wall 511. An adjustable, louvre 566, and filter 583 cover ports 565 to selectively control the fresh air flowing through ports 565.

Wall 561 extends from wall 511 horizontally above bottom wall 529 to second wall 527, so as to define air chamber 562.

Spaced orifices 563 in wall 561 permit the communication ;j ibetween air chamber 562 and heating chamber 544, defined between oven side wall 511 and exterior wall 527.

Extending upwardly from heating chamber 544 through oven top wall 512 is duct 567. Mounted on top wall 512 above oo 0 0o and communicating with duct 567 is blower assembly 568. Blower 00 0 assembly 568 includes centrifugal blower 569 having inlet duct 0 0 S 9ooB. 570 at its low pressure side. Inlet duct 570 is connected to '15 and communicates with the upper end of duct 567, and also to oooo fresh air inlet 571. Air inlet 571 communicates at one end with duct 570 and is open at its other end 572 to the atmosphere outside oven housing 510. Filter 573 covers the 0o °o open end 572 so that any air entering blower assembly 568 i oo20o therefrom is properly filtered to remove suspended foreign 0 o 0 0 00 i matter such as dcust.

An electronically operated controller 575 controls the 0 ij position of damper 576, which is contained in fresh air inlet !571. Thus, an electronic signal from controller 575 causes damper 576 to bias to an opened or closed position in inlet 571, controlling the amount of fresh air entering blower C assembly 568 through inlet 571. The controller can receive a signal from a sensor (not shown) in the drying chamber to initiate its actuation, or can be actuated by a manual control means. These elements for automatically controlling damper 576 are well known and understood by those in the art. Extending downwardly through top wall 512 from the high pressure side of centrifugal blower 569 is make-up air heating duct 577. Duct 577 communicates at its upper end 578 with the high pressure side of centrifugal blower 569 and extends downwardly through heating chamber 544, and connects to horizontal make-up air o o supply duct 579. Duct 579 extends horizontally within heating ,o chamber 544 along the length of radiant wall structure o Spaced along duct 579 and attached thereto and communicating with duct 579 are spaced outlets 580. Outlets 580 extend I '40 through walls 527 and 522 and terminate along the lower portion of wall 522 in drying chamber 521 to define outlet ports 581.

Spaced access plates 582 in wall 523 are releasably secured to ao «wall 523 to cover access ports (not shown) in wall 523. Burner assembly 540 can thus easily be accessed for maintenance.

Access plates 582 can be incorporated into any of the embodiments of the present invention.

This sixth embodiment operates in a similar fashion to the assembly 20 of the first embodiment, except for the preheating and delivery of make-up air to drying chamber 521.

The operation of blower 569 causes a negative pressure in heating chamber 544, which draws fresh air through louvre 566 -31vihii giwii .11, I I I I I jand filter 583, and into chamber 562, then through spaced orifices 563 and upwardly into heating chamber 544. In heating chamber 544 this fresh air is heated by convection from wall 527. The heated fresh air is drawn upwardly through duct 567 and into inlet duct 570, where it is mixed with outside fresh air which is drawn by blower 569 though filter 573 and fresh air inlet 571. The controller 575 operates damper 576 to selectively control the amount of unheated fresh air that mixes with the heated fresh air in duct 570, so that the temperature of the mixed air is equal to the ambient temperature of the oven. This mixed air is forced by blower 569 downwardly boe j through make-up air heating duct 577, into make-up air supply Sduct 579 and then into respective spaced outlets 580. This [*0 filtered, heated make-up air is then delivered through ports 15 581 into drying chamber 521 along the length of radiant wall 522.

In this embodiment the input to the burner 540 is preferably controlled by a proportioning temperature controller o (not shown) which receives its signal directly from a sensor (not shown) which measure the radiant wall's 52'; temperature.

J, 4 The amount of heat transferred to the make-up air through wall 527, with few exceptions, should always be greater than the amount of energy required, and therefore the final temperature of the air entering the drying chamber 521 is controlled by diluting the heated air with a proportional amount of filtered room air.

-32- The seventh embodiment, illustrated in Fig. 8 is similar to that of the sixth embodiment, except that means is included to preheat the exhaust air exhausted from drying chamber 621, and simultaneously heat filtered, fresh, make-up air for delivery back into drying chamber 621.

This embodiment includes an upstanding third wall 685 spaced outwardly from second wall 627 and inwardly from oven side wall 611 to divide heating chamber 644 into two chambers, fresh air heating chamber 644 and exhaust air heating chamber 686. Third wall 685 extends upwardly from bottom wall 661 to oven top wall 612 so that no communication is permitted between "'fresh air heating chamber 644 and exhaust air heating chamber a G 6,86. In this embodiment, port 665 is defined in the lower "6*p'o tion of oven side wall 611 above transversely extending wall 661. Bottom wall 661 is, as in the previous V"mbodiment, spaced upwardly from bottom oven wall 617 to define a chamber 662 therein. However, bottom wall 661 does not include any apertures positioned to allow communication between &'camber 662 and either fresh air heating chamber 644 or exhaust 0 air heating chamber 686. Further, in this embodiment, make-up 'ag'i heating duct 677 extends downwardly from the high pressure 669 side of centrifugal blower 4 through heating chamber 644, ahY through bottom wall 661, where heating duct 677 terminates 40 at and communicates with longitudinally extending supply duct i 25 679. Supply duct 679 empties through spaced ports 687 into chamber 662. Chamber 662 is further defined to extend below -33burner assembly 640 and terminating at bottom portion 623 of radiant wall 622 at spaced ports 681, which open into drying chamber 621. Additionally, second wall 627 defines elongate, longitudinally extending, aperture 663 defined along its lower portion, at or slightly above the level of burner assembly 640, as shown in Fig. 8. Transverse air ducts 634 are disposed above longitudinally extending exhaust ducts 633 at spaced locations along the upper edges of walls 622 and 627, to permit communication of the drying chamber 621 to the exhaust gas heating chamber 686, without allowing communication of combustion chamber 628 with either drying chamber 621 or with 0 oo00 exhaust heating chamber 686.

ae a In operation of the seventh embodiment, heated exhaust 'gases are delivered upwardly from burner 640 through combustion I 1, chamber 628, being drawn upwardly by an exhaust assembly (not shown) out of combustion chamber 628. Simultaneously, the negative pressure created by the exhaust assembly (not shown) is communicated through elongate aperture 663 to exhaust gas 0 0 oo heating chamber 686. Thus, exhaust gas, includini the VOC's contained therein, is pulled from drying chamber 621, through I transverse ducts 634 and downwardly into exhaust gas heating chamber 686. The exhaust gas is heated by convection 'rom second wall 627 as it passes downwardly through chamber4---r Further, third wall 685 is also heated by the radiant energy 25 emitted by wall 627 through chamber 686. The exhaust gases then pass through elongate aperture 663 and into combustion -34- L r~u~p llllll chamber 628. This preheated exhaust gas is then incinerated by burner 640 and drawn upwardly through chamber 628 and exhausted therefrom. Simultaneously, centrifugal blower assembly 668 pulls fresh make-up air through louvres 666 and filter 683 and into heating chamber 644. As the fresh make-up is drawn upwardly through heating chamber 644 it is heated by convection form third wall 685. The air is then drawn through duct 667 and into fresh air inlet duct 670, where it is mixed with fresh outside air drawn by blower assembly 668 through fresh air inlet 671. This mixed air is forced by blower assembly 668 downwardly through make-up air heating duct 677 and into 0 longitudinally extending make-up air supply duct 679. The filtered, preheated air is then forced through chamber 662 and through spaced ports 681 and into drying chamber 621. Thb"s, in the present embodiment, exhaust gases are preheated and delivered to the combustion chamber for incineration of the VOC's therein, and also fresh air is preheated and delivered to OOOOo the drying chamber for convective heat transfer in the drying chamber 621.

20 This embodiment of the present invention provides for all of the heat transfer modes within the confines of the oven exterior walls 611. Infrared radiation is generated from the radiant wall 622 and is directed into Lhe drying chamber 621.

Also, some convective energy is created by wall 622. The j single source of energy from burner 640 is further used to Ohl- provide the energy to preheat the exhaust products and to ultimately incinerate them.

A radiant wall structure of the present invention can be incorporated into an existing oven housing to convert all or 5 a portion of the oven to a radiant energy emitting type of -s Soven. Fig. 9 depicts a radiant wall insert 720 placed within an existing oven enclosure 710. An aperture 730 defined at the top of radiant wall 722 permits the hot products of combustion to be discharged directly into drying chamber 721. In such a conversion, propeller-type turbulator fans (not shown) could be used to circulate the gases within drying chamber 721, or the o 0 0 S° products of combustion could be expelled into a duct (not 0 -shown) for discharge. This embodiment of the present invention ,o can be constructed very narrow in width (dimension d) of 9 0 0 1 or less, which allows relatively easy installation into 0000 S 0 most oven-type enclosures.

It should be understood that the baffles 43 cascade .o--.plates 251 or vanes 358 can be incorporated into any of the o° 'oabove-described embodiments to assist in controlling the heat 0 20 transfer processes.

It will further be obvious to those skilled in the art that many variations may be made in the above embodiments here o oo 0o.0chosen for the purpose of illustrating the present invention, and full result may be had to the doctrine of equivalents without departing from the scope of the present invention, as defined by the appended claims.

-36- 1

Claims (49)

1. An apparatus for generating radiant energy, comprising: niuosyccae a Afirst wall for emitting radiant heat; a second wall adjacent to and spaced from said first wall; means for closing the end portions of said first wall and said second wall, for defi--ing, with said first wall and said second wall, a chamber; means for providing heated gases for 00 D. 0 movement along a path of travel through said chamber and for 00 0 0 "heating said first wall; 000 00 rSe-o(c theXPAc 3tz ztien area of said chamber .),,varying along said path of travel for varying the velocity of said gases moving in said chamber to thereby vary the amount of heat delivered to increments of said first wall. 0 )00 0 ~o2. The apparatus defined in Claim 1 wherein said chamber is tubular and said heated gases pass through said chamber for progressively contacting successive increments of said wall. 0

3. The apparatus defined in Claim 1 wherein said means for providing heated gases includes a linear gas burner disposed at one end portion of said path of travel and wherein -37- 971 0; Ila ill .Y ~rr~l r l -tLII iii Ssaid gases include air, means for moving said air into said chamber and along said path of travel and out of said chamber and wherein said air passe5 said linear burner after it enters said chamber.

4. The apparatus defined in Claim 1 including: wAic/* is c,--;iuously conoave_ a third wallAfor emitting radiant heat Adisposed in spaced, opposed relationship to said first wall; a fourth wall adjacent to and in spaced relationship to said third wall; means for closing the ends of said third 00 Secon( wall and said fourth wall for defining a chamber between sai 0 ""third wall and said fourth wall; 0.0000o oO means for heating said second chamber for o C) 2 jLSo providing heated gases for movement along a path of travel 0000 through said second chamber; and the cross-sectional area of said second oo.. chamber varying for varying the amount of heat delivered to 0 O oi'. increments of said third wall. 0oo b 00 d The apparatus detined by Claim 4 in which the opposed first wall and third wall define, therebetween, an oven passageway and means for moving successive objects to be dried, through said oven passaoeway. -38- r- I CICII) IIC L -e*lil*rar~lllrC~ l~~

6. The apparatus defined in Claim 4 including in confAvIUously c~ecave which said first wall isarcuatoe curving about a horizontal c-0 w1/ocUs axis within said passageway and said third wall is aw-&ua concave e-urv:ng- about a second horizontal axis within said passageway.

7. Process for providing radiant heat comprising: disposing a radiant wall in a position in which one surface thereof, when the radiant wall is heated, will emit radiant energy; passing a heated gas along the other surface of said radiant wall for heating respective increments of said 0 00 o° radiant wall or aid :radiant w:all sufficiently for said one surface to emit said radiant energy; and g changing the velocity of said gas contacting said increments of said radiant wall to thereby vary the amounts of heat respectively delivered to said increments.

8. The process defined in Claim 7 including forming a tubular chamber in which said radiant wall defines a portion of said chamber and wherein said gas is heated at one end I portion of said channel and is thereafter passed along said tubular channel from one end to the other for progressively contacting successive increments of said radiant wall, and where the cross-sectional area of said chamber is progressively tapered to progressively decrease said cross-sectional area and thereby increase the velocity of said gas. -39- -IWYL~-(~IUI~L ~L~I 111~ 1~

9. A radiant wall structure, comprising: coAfIUqousiy concacve con cqve- a 4 radiant emitting wall having an exterior radiant energy emitting surface andAAe interior surface; a second wall spaced -ut:w a distance 4 e. <f4 4 er1ior sUCr-Cfce. of fromAsaid radiant emitting wall for defining a combustion chamber therebetween; and heating means disposed within said ti q o(recritol combustion chamber for delivering heated gas 4 through said combustion chamber, and imparting heat to said radiant emitting wall whereby the distance between said radiant emitting wall and said second wall is selectively varied to vary the velocity °,of said heated gases to thereby vary temperature along said ao o-0adiant emitting wall. 1 0 0 0000 o,00 10. The radiant wall structure defined in Claim 9, whereby the distance between said radiant emitting wall and scIcf dt'rec i'& said second wall is progressively decreasedAto increase the 'ove'locity of said gas through said combustion chamber, thereby increased temperature to said radiant emitting wall.

11. The radiant wall structure defined in Claim 9, .j aid exhaust means disposed along said radiant wall structure for withdrawing said gas from said combustion chamber. -28- )Ti .~r0

12. The radiant wall structure defined in Claim 9, and baffle means mounted along said second wall within said combustion chamber for forcing said gas against said radiant emitting wall.

13. The radiant wall structure defined in Claim 9, and directional vane means disposed between said radiant emitting wall and said second wall for directing said gas delivered through said combustion chamber.

14. The radiant wall structure defined in Claim 9, -we ex- er;or s.Uf-ace( o-f and cascade plate means mounted alongAsaid radiant emitting o wall for controlling the convective energy which is absorbed from said radiant emitting wall. 0000 o -l a 04GQ o. 15. The radiant wall structure defined in Claim 9, whereby said radiant emitting wall is curvilinear, having a convex side within said combustion chamber and a concave side 00 outside from said combustion chamber. 000 0 0 0 36. -The radiant wall structure defined in Claim9- wherein said second wall is curvilinear g a concave side So within said combus amber and a convex side outside said uition chamber. -41- __lr ;Il; i r; irii e 42

16. The radiant wall structure defined in Claim 9, and a bottom wall secured to the lower edges of said radiant emitting wall and said second wall, and side panels attached to the forward and rearward vertical edges of said radiant emitting wall and said second wall.

17. The radiant wall structure defined in Claim 9, wherein said heating means includes a line burner.

18. The radiant wall structure defined in Claim 16, wherein said heating means is disposed along said bottom 04 On o 10 wall.

19. The radiant wall structure defined in Claim 9, 0 including exhaust means for withdrawing said gas from said o combustion chamber and for withdrawing air from outside of 0 said combustion chamber. 15 20. The radiant wall structure defined in Claim 9, wherein said radiant emitting wall is elongate and °o curvilinear, with the concave exterior surface extending 000 0 °about a longitudinal axis the exterior surface defining a 0000 °J radiant energy emission surface for emitting radiant energy outwardly from said emission surface. oo0:oo 21. The radiant wall structure defined in Claim 9, S.wherein the distance between said radiant emitting wall and said second wall from the respective bottom edges of said radiant wall and said second wall toward the top edges of said walls is progressively decreased then progressively increased. ;g /p>sT LY 43

22. The radiant wall structure defined in Claim 16, wherein said heating means is disposed above said bottom wall within said combustion chamber.

23. The radiant wall structure defined in Claim 9, and access means disposed within said radiant emitting wall for providing access to said combustion chamber.

24. The radiant wall structure defined in Claim 11, and an exhaust chamber interconnecting said combustion chamber and said exhaust means. on oo

25. The radiant wall structure defined in Claim 11, o, wherein said exhaust means includes a centrifugal blower. o oo 26. The radiant wall structure defined in Claim 9, and duct means disposed along an upper portion of said radiant emitting wall for allowing air outside said combustion chamber and along the exterior side of said radiant emitting wall to pass through said duct means and along a 0 side of said second 0o 0* Ok0 o0 o ¢~6 L 44 wall which is outside the combustion chamber, wherein said second wall defines an opening along its lower portion for allowing said air to enter said combustion chamber.

27. The radiant wall structure defined in Claim 9, including fresh make-up air means for delivering air outwardly from the exterior surface of said radiant emitter wall.

28. The radiant wall structure defined in Claim 27, wherein said fresh make-up air means includes a duct spaced from said second wall on the outside of the combustion chamber and wherein a portion of said duct passes through said second wall and said radiant emitting wall with an outlet port spaced outwardly from the o exterior surface of said radiant emitter wall.

29. The radiant wall structure defined in Claim 28, wherein said fresh make-up air means includes blower means for delivering fresh air through said duct and said outlet S.port and outwardly from the exterior surface of said radiant emitting wall.

30. The radiant wall structure defined in Claim 29, wherein said blower means includes a centrifugal blower.

31. The radiant wall structure defined in Claim 29, wherein said fresh make-up air means includes damper means to vary the quantity of air delivered by said fresh air duct means. i I_ 45

32. The radiant wall structure defined in Claim 31, wherein said damper means includes a damper and controller means connected to said damper to automatically control the actuation of said damper to vary the quantity of air delivered by said fresh air duct means.

33. A process for directing radiant energy from a radiant wall structure including a radiant wall having a continuously convex inner surface and a continuously concave outer surface and a second wall spaced from the S 10 inner surface of said radiant wall for defining a combustion chamber therebetween, comprising: o4 .oo o generating heated gases by igniting a combustible 0 fuel mixture; 0 delivering said heated gases against the inner o oo 15 surface of said radiant wall; and .o44 selectively varying the cross-sectional area of the 000 combustion chamber, whereby the velocity of said heated 0° gases delivered against said radiant wall is thereby varied.

34. The process defined in Claim 33, whereby the velocity of said heated gases is increased as the cross-sectional 0.0o area of the space interim to the inner surface of said radiant wall is decreased. 46 The process defined in Claim 33, whereby the velocity of said heated gases is decreased as the cross-sectional area of the space interim to the inner surface of said radiant wall is increased.

36. The process defined in Claim 33, and forcing increased quantities of said heated gases against selected portions of said inner surface of said radiant wall.

37. The process defined in Claim 33, whereby radiant energy is directed outwardly from the outer surface of said radiant wall. 0 38. The process defined in Claim 37, and varying the :0000radiant energy directed outwardly from said radiant wall. r0 :0 39. The process defined in Claim 37, and disposing cascade plate means along the outer surface of said oo. 15 radiant wall for varying the radiant energy absorbed from the outer surface of said radiant wall.

40. The process defined in Claim 33, and exhausting said gases generated by igniting said combustible fuel mixture.

41. The process defined in Claim 33, and exhausting air from the outer side of said radiant emitting wall.

42. The process defined in Claim 33, and directing air from a space which is outside of the combustion chamber and adjacent the outer side of said radiant emitting wall, past a side of said second wall which is outside the combustion chamber and mixing said air with said heated J gases. Kb* 47

43. The process defined in Claim 33, and mixing the air from the outer side of said radiant emitting wall with said heated gases.

44. The process defined in Claim 33, and directing fresh make-up air to the outer side of said radiant emitting wall. The process defined in Claim 33, and preheating fresh make-up air and directing said preheated make-up air to the outer side of said radiant emitting wall.

46. The process defined in Claim 33, and directing fresh 0o make-up air passed said second wall, and then directing o said fresh make-up air to the outer side of said radiant emitting wall. o 47. A radiant wall structure comprising an arcuate o 15 radiant wall having continuous convex inner surface and a continuously concave outer surface for directing radiant Soenergy outwardly from said outer surface, a second wall disposed in spaced relationship to the inner surface of said radiant wall, said radiant wall and said second wall 0 20 defining a passageway through which air is passed, means for directing air through said passageway and heating *~444 means disposed in said passageway for heating said air as said air is directed through said passageway, the distance between incremental portions of said radiant wall and said second wall varying along said passageway, the variation and distance between increments of said radiant wall and increments of said second wall being sufficient to vary the velocity of the air passing between such increments for thereby altering the velocity of said air with respect to the successive increments so that said air will deliver varying amounts of radiant energy along the surface of said radiant wall as said air changes in velocity. ~DuaaF~ 48

48. An oven comprising: a housing having a pair of opposed housing side walls defining an open interior whereby successive objects can be moved through said oven interior along a path; a pair of spaced, opposed radiant emitter walls disposed within said interior of said housing and on opposite sides of said path for defining a longitudinally extending drying chamber with an entrance end and an exit end, each of the radiant emitter walls having a continuously convex exterior surface facing the path and a C-OCcoLve- continously.onexo interior surface; 00 a first backing wall spaced from the interior 0J 0 surface of one of said radiant emitter walls for defining a first combustion chamber therebetween; o 15 a second backing wall spaced from the interior ooo surface of the other said radiant emitter wall for defining a second combustion chamber therebetween; and heating means disposed in said first and said 0 CLu second combustion chambers for heating said radiant S 20 emitter walls for causing said radiant emitter walls to emit sufficient radiant energy inwardly toward said open interior to heat said objects as they pass along the path ,o through said open interior, wherein the temperature gradient along the vertical dimension of said radiant emitter walls can be selectively varied by adjusting the distance between each radiant emitter wall and the respective wall which is spaced from the interior surface of that radiant emitter wall. i y1 49 -49

49. The oven defined in Claim 48, wherein said heating means generates heated gases by igniting a combustible fuel mixture. The oven defined in Claim 49, and means disposed in said first combustion chamber for forcing said heat gases against said radiant emitter walls.

51. The oven defined in Claim 49, and exhaust means communicating with said first combustion chamber for :O withdrawing said heated gases from said first combustion 10 chamber. a oo S0 52. The oven defined in Claim 48, and exhaust means for 4000 o,0 0 withdrawing air from said heating chamber. oo 53. The oven defined in Claim 48, wherein said heating means includes a linear burner. o~ 15 54. The oven defined in Claim 48, wherein said radiant emitter walls are elongate and curvilinear, having an outer concave side and an inner convex side. The oven defined in Claim 48, wherein the cross-sectional area of the combustion chamber between said radiant emitter walls and said backing walls progressively decreases from the bottom edges of said walls towards the top edges of said w.ls. 50

56. The oven definec. in Claim 48, wherein the cross-sectional area of the combustion chamber between said radiant emitter walls and said backing walls progressively increases from the bottom edges of said walls to the top edges of said walls.

57. The oven defined in Claim 48, and port means defined by one of said radiant emitter walls for allowing the passage of air from said drying chamber into one of said combustion chambers.

58. The oven defined in Claim 48, and cascade plate means mounted to the outer surface of said radiant emitter wall for varying the radiant energy that is absorbed by said objects.

59. The oven defined in Claim 48, wherein one of said backing walls is spaced inwardly from one of said housing walls for defining a first heating chamber therebetween.

60. The oven defined in Claim 59, wherein the other of said backing walls is spaced inwardly from the other of said housing walls for defining a second heating chamber therebetween. S" 61. The oven defined in Claim 59 and duct means mounted along the upper portion of one of said radiant emitter walls for allowing the passage of air from said drying chamber to said first heating chamber. i dil i 51

62. The oven defined in Claim 61, wherein said one of said backing walls defines an opening between said first heating chamber and said first combustion chamber.

63. The oven defined in Claim 59, wherein said first heating chamber contains an insulation material.

64. The oven defined in Claim 59, and fresh make-up air means disposed within said first heating chamber and Oo communicating with said drying chamber for delivering fresh make-up air to said drying chamber.

65. The oven defined in Claim 64, and fresh make-up air means disposed within said first heating chamber and communicating with said drying chamber, said fresh make-up air means also including a mixing chamber communicating i with said first heating chamber, whereby said fresh make-up air within said first heating chamber is mixed sio owith said fresh make-up air outside of said housing side 000.. walls to result in a fresh air mixture which is delivered 0through said air duct means and into said drying chamber.

66. An apparatus or process for generating radiant energy 0 20 as hereinbefore described with reference to the I 0 accompanying drawings. L ~r~rr~ I Ti i *0000 400 I tC~ ^SS^ f^HW w 0 52

67. A radiant wall structure or a process for directing radiant energy from a radiant wall structure as hereinbefore described with reference to the accompanying drawings. 5 69. An oven as hereinbefore described with reference to the accompanying drawings. DATED this 10 day of September 1992 HADEN SCHWEITZER CORPORATION Patent Attorneys for the Applicant: I I I F.B. RICE CO. I 0o o o ou ab o 9 r0 0 IYI