US3399833A

US3399833A - Low intensity radiant heater system and burner therefor

Info

Publication number: US3399833A
Application number: US601700A
Authority: US
Inventors: Arthur C W Johnson
Original assignee: Comb Res Corp
Current assignee: Combustion Research Corp
Priority date: 1966-12-14
Filing date: 1966-12-14
Publication date: 1968-09-03
Anticipated expiration: 1985-09-03

Description

Sept 3, 1968 A. c. w. JOHNSON 3,399,833

LOW INTENSITY RADIANT HEATER SYSTEM AND BURNER THEREFOR Filed Dec. 14. 1966 4 Sheets-Sheet l I I 52 -30 |8 -30 l 34 I 3: /2s 28 28\ -50 32 54 lo l2 48 M 24 I 1 I 1 If I INVENTOR. ARTHUR C. W. JOHNSON ATTORNEY Sept; 3, 1968 A. c. w. JOHNSON 3,399,833

LOW INTENSITY RADIANT HEATER SYSTEM AND BURNER THEREFOR Filed Dec. 14, 1966 4 Sheets-Sheet 2 k 60 @fwo {I02 J} 64 763C- --|OO H23 :1

u u 44% H4 K46 45 I26 .0 & la-:12, 6-? v INVENTOR. ARTHUR C. W JOHNSON ATTORNEY P 1968 A. c. w. JOHNSON 3,399,833

LOW INTENSITY RADIANT HEATER SYSTEM AND BURNER THEREFOR Filed Dec. 14, 1966 4 Sheets-Sheet :5

, INVENTOR. ARTHUR c. w. JOHNSON ATTORNEY Sept. 3, 1968 A. c. w. JOHNSON LOW INTENSITY RADIANT HEATER SYSTEM AND BURNER THEREFOR 4 Sheets-Sheet 4 Filed Dec. 14, 1966 FIG. l2

INVENTQR. ARTHUR c. w. JOHNSON BY 3 m ATTORNEY U i d S te at o 73 ABSTRACT OF THE DISCLOSURE This invention relates to a low intensity radiant heater system and burner or a plurality of burners therefor, and more particularly to a gas-, or optionally an oil-fired burner unit in and associated with a radiant heating system, wherein the air for the burner, and optionally the burner structure itself with its controls and piping, are taken from an input section located outside of the structure enclosing an area to be heated, and the products of combustion from the burner(s) are discharged by an exhaust fan at the output end of the system, outside of the structure within which the radiant heating is generated and effected.

- The invention generally involves a system in which the chemical energy of the fuel is converted into thermal energy to heat the wall of a conduit which in turn radiates'a large percentage of the conducted thermal energy to a ground floor plane, directly but preferably in conjunction with a reflector disposed above the conduit. The preferred heating system further involves an input conduit supplying air from outside a structure to be heated to a burner conduit in the stream of flow, a burner unit, a length of radiant conduit fabricated from materials having relatively high emissivity values, such as oxidized or or painted steel, porcelainized steel, etc., heated by gas radiation and convectively by the combustion gases generated by the burner, an exhaust or suction fan located in the output portion of the conduit for drawing (1) air through the input portion of the conduit into the burner unit and (2) the products of combustion generated by the burner within the conduit for discharge outside of the building in-which the radiant heater system functions. Another function of the exhaust fan, particularly from a safety standpoint, is to draw room air into the system through the conduit connectors where leakage occurs or a seal may be broken, instead of-as in a pressure systemdischarging the dangerous products of combustion into an enclosed space through 'such leakage ports.

In brief, any fuel-fired heating system operates by conversion of the chemical energy of the fuel into thermal energy to impart its heat into the system by convection and radiant energy. The radiant component of thermal energy is capable of being guided in conduits or deflected and directed by means of reflectors so that broad band areas or relatively confined areas can be heated by this radiant component. In more accepted conventional commercialspace heating systems the chemical energy in the fuel is transferred or converted into thermal energy to heat fluids such as air or water, which is usually directly or indirectly converted into warm air directed by fans or gravity in such. a way that the thermal energy becomes easily deflected and dissipated by air currents. Within the past decade, attempts have been made, with varying degrees of success, to introduce radiant heating systems as a supplement for other methods of heating, suchas embedding hot water pipes in floor structures to heat them by conduction.

The heating system of this invention reduces the amount of maintenance usually required and is substantially maintenance free, because air taken to use in the Pi atented Sept. 3, I968 burner and heating system of this invention is relatively clean, b'ein'g' taken from outside of the building or from within the building" if such airis relatively freeof corrosive vapors and dirt and substances that'gum up-the air passing components and their ports, while air-taken from withina building having commercial or industrial activity is usually dirtyand maintenance charged. The air required for combustion at the burner can be brought into the heating system from outside-of the buildingby the operation of the suction fan located adjacent the output end of the system, if conditions within the building do not permit. This air should be relatively free of dust, dirt, fumes, vapors and other contaminants which normally are present within the confines of an industrial building, manufacturing facility or other active commercial establishment. Inasmuch as the system is operated under negative pressure (suction) at all times, the air required for combustion should be relatively dirt free to prevent clogging of the burner, a condition that ultimately affects combustion efiiciency as time elapses. The system can be completely independent of the environment within which heating will be effected. The system, although of relatively low intensity, has a high enough temperature to allow a large percentage of its energy to be transferred by direct and indirect radiation, but the burner unit is designed and/ or controlled so that it will not operate at too high a temperature, permitting the use of steel or similar low cost conventional materials and yet avoid the creation of problems of oxidation within the system leading to the corrosive deterioration thereof. The system, nevertheless, is eflicient and provides simple heating means, particularly for industrial and commercial areas, that avoid many of the heating problems inherent in systems utilizing air currents within the building that can only produce serious maintenance and replacement problems, and which allow most of their heat energy to be wasted in the upper reaches of the building and to be substantially dissipated by air currents entering through doors and cracks.

The system of this invention and the burner used therein can be either gas or oil fired. It is a high efficiency radiant heating system, offering high thermal efficiencies and consequent economy of operation. This beneficial result is achieved by a large radiating surface that can be extended by the system from the burner unit through an entire structural area, with a minimum of localized hot spots due to local concentrations of combustion or convection-type units. In fact, the heating system of this invention can also be re-circulating in design. A significant result is that, by virtue of the inventive concept, an optimum amount of heat can be given up by radiation within the inside of a building without producing severe or serious corrosive problems such as result from the use of a conventional high intensity unvented radiant heating system producing a condensation of the products of combustion in an inadequately vented building. Since the heating system of this invention is basically a radiant energy system, localized portions or areas of a building structure can be heated more effectively than by convection means.

Although little or no attempt is normally made in commercial fuel-fired heating and burner systems to control the mechanism, temperature and effects of the flame, in the system of the instant invention such control has been attempted and effected in the following manner. All of the air required for combustion in the burner and heating system, as well as some excess air, is introduced through a regulated inlet section at the input end of the burner system. This inlet section is usually located outside of the building and in such event is provided with a bird screen or shield over its input end. In some instances the inlet section is located within the building structure where the air to be used for combustion is relatively dirt free and is satisfactory for use with the burner unit and will not substantially reduce the efficiency of the burner over a period of time. The air is conducted to the burner unit by a conduit which may, but need not necessarily, be of the same diameter or cross-sectional magnitude as the conduit of the heating system to which it is directly connected. The burner unit is preferably located relatively close to the input end of the system, and the air brought into the system is introduced into the burner assembly in such quantity and at such a rate as to limit the temperature of the products of combustion generated by the burner. In so doing, the temperature of the radiant conduit is controlled to a lower order of both temperature and radiation. Thereby, the radiant conduit achieves a more uniform temperature throughout and the radiant drop is relatively less than those achieved by other systems. Obviously, the temperature at the burner and in the combustion area can be regulated over a wide range depending upon the amount of gas or fuel introduced at this point. Although the products of combustion leaving the burner will be up to this controlled limit temperature, they will also contain an excess of oxygen, so that the percentage of such excess of oxygen will be inversely proportional to the amount of oxygen consumed by the combustion of the fuel gases.

A sufficient length of conduit is added to the burner tube in order to reduce the products of combustion to a temperature of approximately 200 F. so as to minimize possible condensation problems before discharging them through the exhaust assembly out of the building into the atmosphere.

The burner of this invention is so constructed that the flame generated by the fuel-air combination is relatively shielded, the flame being confined substantially to the central portion of the radiant tube by means of a spin vane plate mounting the burner jet and by air ports in the plate adjacent the jet for greater efficiency of combustion. The ports and the spacing between the vanes of the plate provide a total area for the passage of air sufiicient to produce and maintain combustion of the fuel issuing from the burner jet, the excess quantity of air passing through the spin vanes adjacent the inner surface of the conduit, whereby the flame of combustion and the combustion products are surrounded substantially by a cylinder of relatively cooler air, reducing the temperature of the radiant conduit in and adjacent the burner unit, and producing a more uniform combustion over a longer distance within the central portion of the tube. Such relatively concentric flow of the excess air adjacent the inner wall of the conduit and about the products of combustion tends to promote complete combustion of the gases and in a more diffused manner over a longer distance of travel in the radiant conduit.

The inventive system utilizes a reflector positioned above and about the radiant conduit so as to deflect the radiation emitted by the pipe toward the floor or toward any other area to be heated. In so doing, the radiant energy is more efiiciently utilized. The reflectors may be made in various shapes and are usually constructed of highly reflective materials such as aluminum, nickeloid, chrome plated steel, polished stainless steel, etc., selected to give the desired heating patterns and to confine and localize the radiant energy to areas requiring heat and minimize the heat loss occasioned by free convection currents flowing over the pipe. Some reradiation from the primary heated tube will, of course, spread radiant energy and heat to other areas, and the radiant efficiency can be affected if free convection currents are allowed to materially cool the radiant conduit.

The heating system of this invention is designed to be erected and installed by means of open suspension hooks supporting the radiant conduit, the reflectors being supported by the radiant conduit and secured thereto by C- hooks and support plates at a height as low as practical to conserve energy without creating excessivelocal floor temperatures uncomfortable to work under. In this way the suspension hooks can be first installed by chains attached to roof or ceiling beams, or installed by supporting them from the steel trusses of the building, and the radiant conduit and superposed reflector simply laid into the complementary support of the suspension hooks.

The present inventionprovides a' low intensity radiant heater system in which the heat is relatively uniformly spread throughout the area to be heated and comprises a radiant conduit, a burner unit serving to heat the conduit, an air intake portion for the burner unit, and an exhaust assembly discharging the products of combustion to the atmosphere outside of the buildinggThe system is capable of being mounted at a relatively .low height in industrial buildings, most of them having an inside height of from 12 to 16 feet. An inlet assembly preferably, but not necessarily as indicated above, protrudes through a wall of the structure and operatively connects a first end of the conduit to the outside of the structure. By installing the inlet end of the conduit outside of the building structure, the amount of dirt and contaminants that enter the conduit are minimized. Such contaminants can affect the air ports, reducing combustion efliciency over prolonged periods of time. Another advantage obtained from an inlet section disposed outside of a building is the avoidance of taking in explosive fumes, or fumes which may become exploive when introduced to the burner unit. The exhaust assembly includes a motor driven exhaust fan which creates a negative pressure or suction throughout the conduit and inlet assembly so that air is continually drawn through the burner unit and the radiant conduit, and the products of combustion and excess air are expelled out of the conduit through the exhaust assembly to the outside of the structure.

A burner unit is operatively connected to the conduit at, in or near the first end of the conduit. The burner unit includes a spin vane plate, and a spark igniter mounted adjacent the burner jet. A source of fuel is provided with associated valve means and fuel pipes to conduct the fuel to the burner jet. The spin vane plate is disposed in the burner unit so that its major surface is transverse to the stream of air being drawn into and through the conduit, and there is a gap between the periphery of the spin vane plate and the inside surface of the burner unit. The spin vane plate has at least one air port therein disposed near the burner jet, a plurality of slits therein adjacent the periphery of the spin vane plate, and an angled vane adjacent each of the slits. The spark igniter ignites at predetermined times the fuel issuing from the burner jet to pro duce a flame which heats the air and other substances which in turn heat the conduit. An air port or ports in the spin vane plate closely adjacent the jet supplies sufiicient air to the burner jet to ensure more rapid combustion of the fuel. The slits and vanes of the spin vane plate cause a portion of the incoming air to spin or swirl, which elongates the flame and keeps it central of the conduit. The gap between the periphery of the spin vane plate and the inside surface of the burner unit tends to provide a tube of incoming air to surround the flame and stabilize it over a longer distance, and simultaneously offsets the gas radiation effect on the conduit in the region of the maximum combustion.

It should be understood that the burner unit of this invention is designed to operate at about 100,000-115,000 B.t.u.s per hour, which is comparable to the size and capacity of unit air heaters, but a larger burner can be used for large commercial or industrial use witha capacity of up to and including 400,000 B.t.u.s without generating such high temperatures that expensive alloy or fragile ceramic pipe constructions are necessary, and minimizing the number of expensive control assemblies required to heat a particular area. Burner units presently available with only 40,000 B.t.u.s/hr. capability generate much higher temperatures and crystallize the conduit piping 5, due to overheating in the flame propagation area, as little or no attempt is made to control the effects of flame impingement upon the radiant conduit.

A reflector is disposed adjacent and usually directly above the conduit to direct the radiation emanating from the heated conduit toward the areas, usually'downward, which are to be heated.- 1 a It is an' object of the present invention to provide a heater system'which attains complete combustion of a fuel in a relatively low temperature conduit.

Another object of the invention is to'provide an infrared heater systemwhich is completely independent of the air, fumes, or other substances within the structure enclosing the area(s) to be heated.

An additional object is to provide a radiant heater system having a novel burner unit which controls the temperature, permitting the use of relatively inexpensive conventional construction materials at optimum temperatures, and the effects of the flame generated thereby.

' Another object is to provide a low temperature radiant heater system which is always fully vented and which prevents fuel leaks and reduces health and fire hazards to a minimum under the adverse operating conditions usually present in industrial buildings.

A further object is to provide an automatic ignition radiant heater system which attains complete combustion of the fuel so that the CO produced is considerably less than 400 parts per million, and will maintain this limit when conditions in the heated area are not condu'cive to good operating conditions.

A further object is to provide a recirculating radiant heater system which allows larger burner units to be used, whichlimits the number of units required to do a given heating job and consequent cost of multiplicity, with a minimum of controls, and which avoid oxidation of the system components while simultaneously limiting and controlling the operating temperature in the system to circa 930 F. where plain or treated aluminized steel is used in the burner and the radiant conduit. These and other objects and advantages of the present invention will be apparent to those skilled in the art upon reference to the drawings'annexed hereto and to the specification.

FIGURE 1 is a-side elevational view of a typical installation=in a building of a first embodiment of the 'radiantheater system of the present invention;

FIGURE 2 is a v'erticalsection view longitudinal of a novel burner unit-which-may be used in the radiant heater'system of the present invention;

FIGURE-3 is a transverse vertical section taken substantially along line 3-'-3 of FIGURE 2 looking toward the gas jet and spin vane plate;

' 1 FIGURE 4 is a circuitdiagram of a direct spark ignition control system;

-FIGURE 5 is an enlarged top plan view of the control box, with its cover removed,"-showing the components of the direct spark ignition control system;

FIGURE 6 is a top pIan'vieW of a second embodiment of the present invention' illustrating a novel recirculating radiant heater system; a I

FIGURE 7 is an enlarged plan view of the inlet and outlet section, the burner unit, and the fan zone of the recirculating system shown in FIGURE 6;

FIGURE 8 is a perspective view of the spin vane plate, the fuel supply tube and burner jet and the air input damper combination, arranged in the burner unit tube shown in broken lines; FIGURE 9 is a fragmentary'vertical longitudinal section view through that portion of a burner conduit show ing a modified combination of the spin vane plate, the burner jet and its supply tube;

FIGURE 10 is'a fragmentary vertical elevational view, partially in section, taken substantially on the line 1010 of FIGURE 9;

FIGURE 11 is a view similar to that shown in FIG- URE 9 showing a further modification of the combination of a spin vane plate and the burner jet.

FIGURE 12 is a diagrammatic outline in the general form of a plan view of a heating system arranged with parallel burners and radiant conduits connected together by a manifold leading to a gas exhaust'section.

Referring to FIGURE 1, there is shown a first embodiment of the present invention of a low intensity radiant heater system 10 having a single run of radiant conduit 12 installed in a building, factory, plant, or other type of structure 14. The building shown has a floor 16, a roof 18, and

walls

20 and 22. The work areas to be heated are designated by the reference number 24. The radiant conduit 12 may be positioned at any height above the floor 16 and at any horizontal location, to heat a predetermined area or portion of the radiation absorbin matter within the building, as may be desired or required. The novel radiant heater system directs a high percentage of radiant heat only where needed, and limits the free flow of such energy to those areas within the building which require little or no heat, such as the space adjacent the roof 18 or areas normally unused or unoccupied by workers or other persons.

The radiant conduit 12 is supported by conduit supports 26 which are of an open C type design so that they may be readily placed in position to suspend the conduit 12 (see FIGURE 3). Each conduit support 26 is hooked onto a suspension hook 28 which is connected to the roof 18 or roof support members by means'of a suspension bar or chain 30.

A regulated inlet section 32 permits all the air required for combustion, and some excess air, to enter the heater system 10 only from outside of the building or structure. The inlet section 32 includes a bird screen 34 and a damper plate 36 having an air port 37 therein (see FIG- URE 2). The inlet section 32 protrudes through the wall 20, the clean air brought in through the inlet section 32 being conducted to the burner unit 40 by a conduit 42.

In the first embodiment of the invention illustrated, a gaseous fuel is introduced into the burner unit 40 and is there ignited by a spark igniter 44, which operates similar to an automobile spark plug. The sprak igniter 44 is a component of a direct spark ignition control system (see FIGURES 4 and 5), most of which is housed within a control box 46. The control box 46 is mounted above and upon the burner unit 40.

The fuel and air mixture ignited in the burner unit forms a flame which is regulated in the present invention. The air entering the conduit 12 by way of the inlet section 32, the regulated flame and the products of combustion formed by the burner unit 40 in the conduit 12 are always under suction in this construction to prevent fumes and the gases of combustion from entering the work area. This negative pressure in the combustion chamber is produced by an exhaust fan device 48 driven by its motor 50 located in the exhaust assembly 52. The thermal radiation emitted by the conduit 12 is reflected and directed to the areas 24 to be heated by an elongated reflector 54 (see FIGURES l and 3) supported by and upon the conduit 12. The motor driven exhaust fan device 48 is operatively connected to the downstream end of conduit 12 for creating a reduced pressure or suction in the inlet section and the main radiant conduit and for driving the gases and combustion products out through the exhaust assembly 52. The exhaust assembly 52 has a portion thereof protruding through the wall 22 so that the exhaust gases and products of combustion are discharged outside of the building. The exhaust assembly 52 includes a bird screen 56.

FIGURE 2 shows some of the details of the burner unit 40 and its associated control box 46, illustrated generally in FIGURE 1. The control box 46 and the reflector 54 are supported on the conduit 12 by U-clamps 58 which allow free expansion between the reflector 54 and the radiant conduit 12. The burner unit 40 and control box 46 can thus be clamped together as one integral package 7 and assembled with a small length of conduit 60 which serves as a combustion chamber and is of the same crosssection as the radiant conduit 12. The control box 46 is easily connected to a source of electricity and a source of gaseous fuel, and is readily detachable from the conduit 60 or burner unit 40.

The gaseous fuel is admitted through a gas inlet pipe 62 (see FIGURES 3 and leading to a gas valve 64 (see FIGURES 4 and 5) housed within the control box 46. The gas valve 64 employed may be a combination gas control which includes a manual ON-OFF gas cock 66, a 90-volt operator 68, a pressure tap with plug 70, and a pressure regulator 72. A gas lead-in pipe 74 (see FIG- URES 2, 3 and 5) emanates from the outlet side of the combination gas control and communicates with the gas burner pipe 76 which lies generally axially of the conduit 60. The gas burner pipe 76 conducts the fuel gas through the center of an air flow deflecting member such as the spin vane plate 78 to a burner jet 80 protruding from the combustion chamber side of the spin vane plate 78.

The incoming air is regulated in part by the orifice 37 in damper plate 36 and by an air flow switch 82 which is controlled by a thermostatic controller 104 positioned adjacent and in the work areas 24. The exhaust fan motor is controlled by the thermostatic controller 104, and the air flow resulting from the exhaust fan operation causes activation of the air flow switch 82 which energizes the burner control system 102. As best seen in FIGURE 3, the spin vane plate 78 has a plurality of air ports 84 in the body of the plates relatively close to the burner jet 80. The air ports 84 are of predetermined dimensions and are placed in predetermined locations relative to the burner jet 80 to ensure that sutficient incoming air is available at the burner jet 80 to produce a localized combustible mixture with the fuel. The air ports 84 are arranged in the body of the plate on a concentric bolt circle intermediate the axis and the perimeter of the plate, and preferably in a medial zone therebetween. The function of the air ports is to permit a quantity of air to pass through the plate relatively adjacent the burner jet 80 to feed the same with some oxygen so as to support combustion but to provide only enough oxygen at this point for such purpose and not to develop complete combustion.

The spin vaneplate is arranged with a perimeter of radial slits 86 and adjacent angled radial vanes or blades 88 formed in the outer circumferential portion of the spin vane plate 78. The outer diameter of the spin vane plate is less than the inside diameter of conduit 60, leaving a relatively small concentric opening 90 between the blades at the perimeter of the plate and the inner surface of the conduit for the free passage of air, much of which flows through as a tube of air adjacent and about the spinnin'g, swirling air flow generated by the angled vanes 88. The clean air sucked in by the motor driven exhaust fan 48 is caused to swirl, spin and undergo a relatively helical motion as it passes through the slits 86 and over the angled vanes 88. The swirling air feeds and elongates the flame generated at the burner jet so that the flame is caused to extend a substantial distance downstream of the burner jet and into the main radiant conduit 12. At the same time, the flame gases and the products of combustion are fed by the spinning, swirling, helical flow of air relatively concentric about the flame and then, or relatively simultaneously, by the outer more cylindrical flow of air adjacent the inner surface of the conduit 12 which came through the gap between the spin vane plate 78 and the conduit 60.

At this time there is no way of precisely determining the flow pattern of the input air, the flame gases and the products of combustion as they come through the burner, the conduit 60 and the radiant conduit 12. But What appear to be features of the flow pattern may be deduced from some operating results of the system. These results will be described more fully below.

As shown in FIGURES 2 and 3, the clearance or gap 90 between the circumference of the spin vane plate 78 and the inner wall surface of the conduit 60 is substantially concentric about the axis of the plate. The air passing over the spin vane plate 78 through the annular clearance 90 tends to keep the inner wall of conduit 60 downstream of the plate relatively cool and to surround the central flame 'and' the swirling flow of air coming from the blades 88 within a cylinder or tube of relatively cooler air. This airflow pattern contributes to the attainment of an important feature of the present invention, namely, a stable efficient flame, and consequent complete combustion of the fuel with more uniform temperatures throughout the system. The temperature generated by the burner unit 40 in the conduit 12 therebeyond is so controlled that it allows the use of low cost conventional construction materials and tends to prevent recrystallization or appreciable oxidation of portions of the burner unit 40 and the portion of the radiant heater system immediately adjacent the burner unit, while producing sustained radiant energy from the conduit 12 to heat work areas 24 at relatively high efficiencies and at relatively lower temperatures of operation. The straight through system having a single mass flow achieves a more uniform temperature and more complete combustion at relatively low temperatures, while producing approximately five percent of CO on the basis of natural gas. The system of this invention utilizes an air to gas ratio of 20 to l, which is below the lower inflammability limits of combustion, and thus the mixture in the conduit 12 is nonexplosive.

Directly below the spark igniter 44 and as a flame check device, there is provided a short visual indicator tube 92 (see FIGURES 2 and 3) having a flat glass plate or window 94 forming part of its threaded bottom cover 96. The visual indicator tube 92 is preferably arranged to face the floor 16 so that an individual standing under the burner unit 40 can tell at a glance the nature and condition of the flame, if any, by merely looking up through the glass plate 94.

An open end of a pressure sensing tube 98 (see FIG- URES 2, 3 and 5) communicates with the interior of the visual indicator tube 92 for sensing the pressure or negative pressure in the combustion chamber of the burner unit on the downstream side of the spin vane plate 78. The pressure sensing tube 98 communicates with the air flow switch 82 (FIGURE 5) mounted in the control box 46. Another pressure sensing tube 100 (see FIGURES 2, 3 and 5) communicating with the air flow switch 82 senses the pressure upstream of the spin vane plate 78. The air flow switch 82 operates as a pressure regulator switch or control for the gas valve 64 to control the operation thereof in response to the difference in pressures sensed by the

pressure sensing tubes

98 and 100. There are two taps (connections) to the switch 82 so that it can sense the differential pressure over the spin vane plate 78, thus measuring and monitoring the air flow. The switch 82 is adjustable to accurately determine and monitor the safe flow condition, and when so adjusted to shut the system 102 down if the air fl'ow conditions do not correct themselves to meet the differential limits set by the adjustment of the switch. The switch 'is calibrated to remain open upon a predetermined differential in pressure, and when such differential is' absent the switch closes and causes the operator 68 to close the gas valve 64.

The burner unit 40 is provided with an automatic sparking system and time trial ignition device with fail safe controls. This comprises a directspark ignition system 102 such as is illustrated in FIGURES 4 and 5. The control system shown and described in'connection with the present embodiment is for a gas-fired unit. An oil-fired unit would be equipped with a'different sensor to suit the particular requirements of oil safety equipment; Such sensor could be either a' stack switch or a lead sulphite cell. r r

The direct spark ignition system 102 shown ignites the burnerjet 80 by mcans of'the spark igniter 44 each'timc for the control box'46.

the line voltage thermostat controller 104 calls for heat. This eliminates continuous pilot operation during the OFF-period and OFF-season, andmakes relighting a pilot burner unnecessary. If the spark igniter fails to light the burner jet 80, the ignition system automatically-locks out in a safety shutdown condition, and the lighting of an alarm signal. lightrThe ignition system can then be reset for operation only by manually resetting and lowering the line voltage thermostat controller 104 setting for several minutes, and then returningthe controller to its normal setting. 1

As shown in FIGURE 4, a.power supply feeds the line voltage thermostat controller 104 which is connected in series with a manually operable toggle switch 120, and with the air flow switch 82. These components and the power supply are connected to an ignition timer 108. The ignition timer 108 is a component-part of a bridge circuit which includes a heater-operated safety switch to shut off the gas valve 64 and the spark igniter 44 in the event that the contacts of a flame sensor 110 do not open to balance the bridge circuit. I

The ignition timer 108 is connected to an ignition transformer 112 which provides sufficient voltage (e.g., 4200 volts nominal) to operate the spark igniter 44. The ignition transformer 112 should be connected to a common ground 114 with the mounting bracket of the spark igniter 44. The ignition timer 108 is also connected to the flame sensor 110 which reacts to temperature change. The contacts of the flame sen-sor 110 open-on a temperature rise (burner jet on) to balance the bridge circuit which will shut off the spark igniter. 44. The contacts of the flame sensor 110 close on atemperature fall (burner jet off) to unbalance the bridge circuit for the next ignition cycle. The spark igniter 44 is connected across the secondary winding 116 of the ignition transformer 112, and operates similar to an automobile spark plug. The ignition timer 108 is also connected to the gas valve 64 which controls the quantityof gas supplied to the burner jet' 80. The actual mounting of thecomponents of the control system "may be seen best in FIGURE 5 which gives a top viewof the control box 46 with its cover 118 removed.

The *manual'toggle switch 120 is employed in series with the 'air flow'switch 2, which i provided with a fine adjustment screw1'124 operatively connected to the air flow switch 82. An electrical service cable 122 may optionally be used for protecting the input electrical wiring A'riumber of single run heater systems can be arranged with their conduits 12 conn'ected to a manifold having a single exhaust fan 48 to draw the products of combustion from the conduit-s 12 and the manifold and discharge them through an outlet section '52 to the outside of the structure 14.

Negative pressure in'the combustion chamber of the burner unit allows the system controls to achieve full or more than their rated capacity: A negative pressure throughout the system up to the exhaust fan eliminates leakage of gases into the's-pace areas being heated, removing a health haiard and causing all gases to be drawn into rather than out "ofthe joints of the system.

FIGURES 6 and 7relate toand illustrate another embodiment of the invention whichinvolves a recirculating type of low intensity radiant heater system. Reference numerals-corresponding to those employed in connection with the single run embodiment are also used in connection with. the recirculating embodiment where the ele- 'ments involved are substantiallyi-dentical or functionally similar. V

In the recirculating heater system .126, the inlet assembly and the exhaust assembly are formed with concentric or

coaxial conduits

42 and 128, respectively. Clean outside air is induced into the inner inlet conduit 42 by-a recirculating and exhaust fan 130 driven by a motor 50 which createsa suction in the inlet conduit 42 and the main radiant conduit 12 to produce a recirculation of air, flame gases and the products of combustion. The same recirculating and exhaust fan also forces combustion products through the outer exhaust conduit 128 to the atmosphere outside the building.

Among the several advantages of a recirculating system 126 are larger burner units-up to 400,000 B.-t.u./hr. or more, resulting in fewer control boxes required per system and consequent reduction in cost; more uniform and higher operating temperaturesfrom about 500 degrees to 930 degrees F. with consequent higher average conduit temperatures resulting in a higher radiant etficiency and with less flue gas losses due to a minimum of excess air present in the burner unit.

It is to be understood, of course, that there are different structural and operational requirements for a burner serving a recirculating system than for a burner in a single run system. Additional consideration and attention must also be given to the purge cycle and the method of ignition as described below, the significance of which is markedly greater in a recirculating system. In either case, however, the advantage present in having the sysstem under negative pressure provides a means for control and safety that is not present and cannot be provide in a pressure system.

The spin vane plate 78, control box 46, and ignition control system 102 are basically the same as used in the single run embodiment. However, higher capacity control components are required in the recirculating system. For example, a larger gas valve 64 which has a gas capacity of 400,000 B.t.u./hr. natural gas may be required. In the single run controls, such gas valve may be of 180,000 B.t.u/hr. capacity.

As best seen in FIGURE 7, the downstream section 132 of the burner unit conduit 60 is modified. This section 132 tapers inwardly at its end to form a venturi in the area where the conduit 60 communicates with the radiant conduit 12.

There are some differences in function of the burner unit 40 in the recirculating system 126 over that in the single run system. One of these is the length of flame. It can be materially shorter in the recirculating system. Another is the reduction in the helical swirling of the air and the mixture of flame and gases as they approach the downstream section 132.

The gases discharged by the recirculating fan 130 are passed through the opening 134 into conduit 128 and into the area of the venturi 136 formed by the" tapering end 132 of conduit 60 and the end portion 138 of conduit 128 there adjacent which terminates at its conjunction with the main radiant conduit 12 in a flowrestricting tapering juncture 140. The pressure generated by the fan 130 is such that the gases will flow into the main conduit 12 and backwardly out the conduit 128 toward its exit end at the bird screen 56. To balance the flow of gases in either direction, a perforated plate 142 is disposed about the conduit 42 and within the conduit 128. The plate 142 has a total area of perforated openings 144 sufficient to allow an exit flow of gases out of conduit 128 in proportion to a flow of such gases through the venturi area 136 and into'the main conduit 12 for recirculation through the conduit, The constriction effected by the tapering juncture 140 tends to limit the flow of gases toward the conduit 12 while the perforated area in plate 142 tends to limit the flow out of the exit conduit 128. These factors are adjustable and controllable and have a correlation to the output capacity and pressure of the recirculating suction fan 130 in the venturi area 136, the tempera-ture of the exhaust gases in such area 136 and the temperature desired and to-be achieved in the main radiant conduit 12.

Since the exit flow of gases through conduit 128 abou the input air conduit 42 is at a relatively elevated temperature, the incoming air will become somewhat heated,

depending upon the length of the input conduit, and when so heated the pressure drop across the spin vane plate 78 will be somewhat less than is present in the straight run embodiment. Under such circumstances, the angularity of the blades 88 in the spin van plate should be reduced in order to increase the pressure drop across the plate to a point and within a range, which is not critical, that effects a more efficient and more stable flame.

Although a reflector 54 for directing radiation from the conduit 12 is not illustrated in FIGURES 6 and 7 for the recirculating heater system 126, it is to be understood that such reflector is a preferred component of the system and is very necessary to obtain maximum utilization of the radiant component when such a system is not located in an oven-type enclosure.

Recirculation of the products of combustion tends to establish a more uniform temperature in the main radiant conduit 12, an important feature of the recirculating radiant heater system 126. It also makes the system more efficient in that less fuel is required to maintain the system at a desired temperature. A controlled minimum amount of excess air is drawn into the burner unit, to produce a complete combustion, but not so much is sucked in as will tend to establish any more than a mini mum temperature gradient in the conduit 12. If the conduit temperatures drop appreciably below 500 degrees F. in the recirculating conduit 12, the radiant efliciency will of course drop appreciably and the percentage of convective losses rise proportionately. The higher the conduit temperature, the higher the radiant efficiency. For the relatively low cost steel conduit utilized in these systems, whether aluminized or not, the optimum maximum operating temperature would appear to be about 930 degrees F. in the conduit.

A modification of the spin vane plate 78 and its combination with the burner jet 80 is illustrated in FIGURES 9 and 10, wherein the air ports 150 are located at the central opening 152 admitting the jet shank 154 and extending radially outwardly a distance past the outer edges of a jet securing fastener such as nut 156. The open area of the ports 150 is such that sufiicient air is drawn therethrough by the action of

exhaust fan

48 or 130 to provide a combustible mixture with the fuel issuing from the burner jet, but which is sufficiently limited so that maximum combustion Will not be effected until the helically swirling stream of air coming from the spin vane blades 88 have begun to intermix with the flame propagated by the combustible mixture at the burner jet.

Another consideration involved, of course, is flame stability. The open free area and the location of the air ports 150 should be such that air is fed to the burner jet at such velocity and rate that it will not smother nor underfeed the flame. Persons skilled in the art will easily be able to adjust such feature of the air ports to suit the requirements of particular applications of the inventive burner unit and heater system.

There may be an area of reduced pressure, conical in shape, that extends from the digital end of the burner jet to the inner edges of the blade slits 86 of the blades 88, which could occasion a toroidal flow pattern from the jet tip to the spin vane plate in the event that the combustible mixture at the burner jet is of too lean proportions. In such event, the air ports 150 should be slightly elongated and/ or widened in order to increase the amount and extent of air flow to the burner jet, to improve the flame propagation and flame stability.

A second modification at the burner jet involves a similar introduction of air to the burner jet at or adjacent its digital end such that a combustible mixture is attained downstream of the spin vane plate. Such modification is illustrated in FIGURE 11, wherein the spin vane plate 78 is provided with a central opening 160 in which a burner jet tube 162 is fixedly secured, a portion 164 extending forwardly of the plate 78 and a portion 166 extending rearwardly. The burner jet 168 is secured in the proximal end 170 of the tube portion 166, in which one or more air ports 172 are disposed adjacent the digital end of the burner jet 168. Thus, as air is drawn into the burner conduit 60, some of it passes through the port or ports 172 to intermix with the fuel issuing from the burner jet 168 to form a combustible mixture in tube 162, ready for ignition at the digital end of tube portion 164, and some of the air passes through the spin plate at the blades 88 to issue in a swirling helical flow pattern and gradually intermix and feed the flame propagated from the tube 162.

Although the building structure 14 is illustrated and described above as a complete housing structure, it will be understood that such structure 14 may be a room or enclosed area within an outer building structure. In such event, the input air can be derived from within or without the outer building structure, and the exhausted products of combustion discharged to the atmosphere outside of the outer building structure.

Although the description given above is that for a gasfired burner unit, it should be understood that an oilfired burner may also be used, and such variation in burner components and controls as may be required is fully within the skill of persons trained in the art to which the invention pertains. representative control system, presently available, s illustrated and described above. Other similar spark ignition or firing ignition systems are also available for use with the burner units of this invention. The control system described operates as follows. When the temperature in the area to be heated falls below the preselected temperature setting of the thermostat 104, the contacts at the thermostat close energizing the exhaust fan motor and, simultaneously, the burner circuits. The

exhaust fan

48 or 130 draws air through each inlet section and burner unit of the particular system. The air flow through any burner unit 40 creates a differential pressure across the spin vane plate 78. The air flow switch 82 senses this dilferential pressure, closes its contacts, and completes the circuit to the direct spark ignition system 102. In the spark ignition system the gas valve 64, the ignition transformer 112, and the safety switch heater of the ignition timer 108 are thus energized causing the burner to ignite. The flame sensor 110 detects the heat of the flame and opens its contact, thus balancing the bridge of the control circuit. When the bridge is balanced the current through the safety switch heater stopsand the safety switch timing system 108 is de-activated. The circuit is now in run condition.

In the event that theflame sensor contact does not open within the 30 to 40 second timing interval of the the spark ignition system. The system thus deenergized the spark ignition system. The system thus deenerized will remain in this state until the power to the entire circuit has been removed for a period of 2 .to 5 minutes.

The spin vane plate 78 performs several functions including the generation of a swirling helical flow stream of air directed by the blades 88, the production of a substantial pressure drop across the plate, and because of its reduced perimeter, the generation of a tubular stream of air within and adjacent the inner wall surface of the burner conduit 60. The angularity of the blades 88 is such as to generate a substantial pressure drop. The plate then becomes an equalizing disc serving heater systems of various lengths and minimizing the pressure losses which marked changes in radiant conduit lengths necessarily produce. However, the gap between the blades 88 and their angularity are not critical, but when arrived at for a main conduit run of say -70 feet can also serve for runs up to about feet, or for runs'appreciably less than 60 feet.

The spin vane plate 78 is supported on the digital end of the gas pipe 76 and secured thereto in any suitable manner, preferably by a nut or nuts on the threaded end of pipe 76, The proximal end of pipe 76 is secured to the wall of conduit 60 at the opening through which the pipe is passed for connection to the gas pipe '74. When so secured, the spin vane plate 78 is positioned substantially concentric in the conduit 60 so that a substantially even gap 90 is present about the perimeter of the plate 78 and within the conduit 60. Should the spin vane plate become eccentric, a wire type spider form (not shown) can be mounted upon-the 'gas'pipe 76 adjacent the plate and bearing upon the inner surface of the conduit 60 to maintain the spin vane plate in concentric relationship to the inner surface of the conduit.

The

exhauster fans

48 and 130 have been described as single speed impeller type centrifugal fans. However, single suction turboblowers may also be used, and multispeed motors may be found desirable in particular applications. In some oven applications, it may be necessary or desirable to provide a proportioning control for the fuel gas to the burner.

In the single run system, in which there is a 20 to 1 air to gas ratio with the products of combustion at a temperature below their lower inflammability limits, the CO output at the exhaust end of the system is approximately 5.00% or less of the total exhaust output.

As illustrated in FIGURE 12, the single run radiant system, suchas' is showng enerally in FIGURES 1-5 and 8 can be combined in number and arranged in a series with individual air intake sections 32, burner units 40 and radiant conduits 12 communicating with and exhausting into a manifold conduit 180 connected to an exhaust section 182'including a conduit 184 connected to and communicating with themanifold 180, an exhaust fan 48 and its motor drive 50, and a gas exhaust discharge pipe or tube 186. Two types of such multiple arrangements are illustrated in FIGURE 12, and it will be understood that other arrangements of multiple heater units and conduits can also be designed to serve the areas to be heated'as' particular requirements for heating may dictate. i l

There is a minimum of excess air in the recirculating system. The CO present in themain 'radiant conduit portion of this system will normally be in the order of 11 to 12% minimizing thermal energy. waste in the flue gases. .The amount of air taken'in at the inlet section of the recirculating system will'be appreciably less than that taken in for the single 'r'un'conduifsystem, the air to gas ratio beingfabout ll to l'instead'of about 20 to 1 for the single .run system. For this reason, it is not advisable to .allow -fullgas to be admitted, loading the system with an explosive mixture in 2 to 4 seconds, and it will be necessary to start the-burner on a reduced ga's input, as by a pilot light. This is. done by additional switching controls operating through supervisory contacts in the timing or controller switch, with an extra pilot or main gas valve. The air flow switch 82 operatesas a purge time delay unit. Such delay "period can be controlled by the adjusting screw 124 on the air flow' switch 82 ,the purge time being variable (as for instance for a minimum of four multiple changes of air) before 'ignitfion'of the fuel gas can be effected Such purgeftirne delay period is of course important in any heating 'system,' but"it is of particular importance in the recirculatingsystem where the amount of excessair available is 'at 'a markedly reduced level.

To' improve'theradiant efficiency the outer surface of the conduit 12 should be a black body emitter for maximur'n'radiant effect. The color or condition of the conduit will not affect the 'c'onvectivecooling action of air currents passing over it.'On the other hand, to minimize the radiation effect in a localized area, the outer surface of the conduit can be made reflective over such area. .Normally, the radiant conduit 12 is made up of tube lengths cut from standard lengths of 6 to 20 feet or more, joined together with sleeve type outer' couplings. The tube material is of relatively light gage cold or hot rolled steel, in lock seam, seamless or spiral form, and it may optionally be coated on the inside surface with aluminum andblack on the outer surface, or porcelain coated to minimize oxidation.

With radiant heaters of the type disclosed herein, the higher the temperature of the radiant conduit the higher the ratio of radiant to convective energy. Therefore, in the recirculation system, the individual burner units can be of higher capacity and the temperature of the radiant can be more easily controlled to maintain higher radiant efficiencies for a complete system from inlet to outlet, while limiting the temperature of the radiant conduit for other practical considerations.

Since the present invention derives its combustion air from outside the building or the enclosure to be heated and exhausts its waste material to outside the building, the present heating system is normally completely independent of the atmosphere or conditions within the building unless air is taken from within such building. Although the products of combustion are normally discharged into well ventilated atmospheric areas outside of the heated structure, it is also possible to discharge such noxious fumes to an area within the structure if such latter area and the structure are suitably, adequately and positively vented and ventilated. The system design keeps dust, dirt, corrosive fumes, gummy materials, oxidizing materials, and explosive fumes out of the burner and system. Thus, the system eliminates major maintenance problems and is maintained at substantially initial operating settings and conditions, conditions that usually are easily aflected by a lack of maintenance. Further, the system of this invention can be designed in sizes comparable to unit air heaters, and yet not have the same large number of expensive multiple units to obtain the same total heating effect.

Having described the invention in its simplest forms, it is to be understood that the features of construction may be changed and varied in greater or lesser degree without departing from the essence of the invention defined in the appended claims.

I claim:

1. A low intensity radiant heater system for a structure having areas to be heated wherein said system is closed throughout its extent and open only at its outer ends, comprising:

an air inlet conduit passing through a wall of said structure,

said inlet conduit having an air input end openly communicating with the atmosphere on the outside of said structure,

a burner unit for said heater system comprising a conduit conjoined to and communicating with the output end of said inlet conduit,

an air flow limiting damper at the air input end of said burner conduit,

an air flow deflecting member generating a substantial pressure drop on the downstream side thereof arranged concentrically within said burner conduit and having substantially the entire perimeter of said member spaced slightly apart from said burner conduit, whereby to initially effect a relatively tubular stream of air flow along and adjacent the inner wall surface of said burner conduit and a relatively helically swirling stream of air flow within said tubular stream and closely adjacent and progressively interspersing and intermixing therewith, a fuel jet secured to said air flow deflecting member axially thereof and therethrough and directed downstream thereof for the discharge of fuel,

ports through the body of said air flow deflecting member and spaced outwardly of said burner jet for the passage of air relatively adjacent the burner jet for effecting a combustible mixture of air and fuel adjacent the exit end of said burner jet and so spaced in said body as to produce a relatively stable and efficient flame propagation, controlled means in said burner conduit for igniting said combustible mixture, means for supplying and controlling the supply of fuel to said burner jet,

a main radiant conduit operatively located in the areas to be heated, andconjunctively secured to and communicating with the output end of said burner conduit for convective and radiative absorption of the thermal energy progressively generated by the intermixing of the burner flame, said swirling helical stream of air, said tubular stream of air, and the resultant products of combustion,

and an output assembly comprising a conduit for the exhaustion of said products of combustion having its discharge opening in an area open to the atmosphere on the outside of the space areas being heated by said radiant conduit,

and a controlled power driven exhaust fan device connected to and communicating with said main radiant conduit and said output conduit,

and means for controlling the input quantity and rate of air and fuel into said burner so as to attain and maintain a relatively uniform though gradually decreasing operating temperature in and consequent radiation of energy from said main radiant conduit throughout the effective length of said conduit, and to control the maximum and minimum temperature limits over the effective length of said conduit and the rate of decrease of such temperature within said limits.

2. The system defined in claim 1, and including means for suspending said air inlet conduit, said burner conduit, said main radiant conduit and said output assembly from the superstructure of said structure having areas to be heated.

3. The system defined in claim 1, wherein said exhaust fan draws all of the gases entering said main radiant conduit through any of its openings to it and discharges the same to the atmosphere outside of said structure.

4. The system defined in claim 1, and including a reflector supported upon and disposed adjacent at least said main radiant conduit and throughout the effective length of said conduit to reflect and direct radiant energy emitted by said conduit toward the areas to be heated.

5. The system defined in claim 1, and including an air flow switch,

a first tubular pressure-sensing member communicating with said switch and operatively connected thereto, and having its digital end disposed in said burner unit conduit downstream of said air flow deflecting member and adjacent the zone of flame propagation,

a second tubular pressure-sensing member communicating with and operatively connected to said switch, and having its digital end disposed in said burner unit conduit upstream of said air flow deflecting member,

means connecting said air flow switch with said means supplying and controlling the supply of fuel to said burner jet for operatively controlling the shut-olf of said fuel supply to said burner jet when the pressures on both sides of said air flow deflecting member reach predetermined relatively equilibrium proportions.

. The system defined in claim 1, and including a thermally responsive device in said burner unit for sensing the presence or absence of a flame, disposed downstream of said burner jet,

and a visual indicator in said burner unit having a transparent elementtherein disposed for viewing the flame issuing from said burner jet and said means for igniting said combustible mixture, control means operatively responsive to the sensing of said thermallyv v, responsive device to continue the igniting function during the absence of flame for a predetermined time delay period and to discontinue such function during the presence of a flame. 7. The system defined in claim 1, and including a control box for said burner unit, affixed thereto and supported thereon, having I,

automatic ignition system components, valve means for controlling the supply of fuel to said burner jet, and an air flow switch including means responsive to a decrease in the differential pressure across both sides of the air flow deflecting member for regulation of said valve means. 8. A recirculating low intensity radiant heater system for a structure having space areas to be heated wherein said system is open at its outer ends and closed throughout its entire intermediate extent, comprising air intake and gas exhaust sections,

a radiant conduit disposed in said space areas to be heated,

a burner unit communicating with said air intake section and said radiant conduit,

a gas exhaust device communicating with and connected to said radiant conduit for constantly maintaining a relatively predetermined negative pressure in said intake section, said burner unit and said radiant conduit, and for constantly maintaining a positive pressure above atmospheric pressure in said gas exhaust section so as to discharge some of the products of combustion from said radiant conduit to the atmosphere in the area where the exit end of said gas exhaust section is located,

said air intake section having its air intake opening disposed for admission of air which is relatively free of dirt and contaminants of a corrosive or orifice-occluding character, said gas exhaust section having its gas exhaust discharge opening in an area open to the atmosphere outside of the space areas being heated by said radiant conduit, said burner unit comprising a burner conduit conjoined to and communicating with said air intake section, an air flow deflecting member generating a substantial pressure drop on the downstream side thereof arranged concentrically with said burner conduit and having substantially the entire perimeter of said member spaced slightly apart from said burner conduit, whereby to initially effect a relatively tubular stream of air flow along and adjacent the inner wall surface of said burner conduit and a relatively helically swirling stream of air flow within said tubular stream and closely adjacent and progressively interspersing and intermixing therewith, a fuel jet'secured to said air fiow deflecting member axially thereof and therethrough and directed downstream thereof for the discharge of fuel, ports through the body-of said air flow deflecting member and spaced outwardly of said burner jet for the passage of air relatively adjacent the burner jet for effecting a combustible mixture of air and fuel adjacent the exit end of said burner jet and so spaced and of such magnitude in said body as to produce a relatively stable and eflicient flame propagation, controlled'means in said burner conduit for igniting said combustible mixture, and means for supplying and controlling the supply of fuel to said burner jet,

one end of said radiant conduit being conjoined to and communicating with said gas exhaust section and forming a venturi junction therewith, the other end of said radiant conduit being conjoined to and communieating with said gas exhaust device, for convective and radiative absorption of the thermal energy progressively generated by the intermixing of the burner flame, said swirling helical stream of air, said tubular stream of air, and the resultant products of combustion,

said burner conduit having its discharge end disposed in and spaced apart from said venturi junction,

controlled means in said burner conduit for igniting said combustible mixture,

and means for supplying and controlling the supply of fuel to said burner jet.

14. The structure defined in claim 13, and including an air flow limiting damper at the air input end of said burner conduit.

15. The structure defined in claim 13, wherein said ports through said body are disposed radially of and closely adjacent the axis of said fuel jet, and comprise elongated slots through said body.

16. A burner unit for a low intensity radiant heater system wherein said heater system is open at its outer ends and closed throughout its entire intermediate extent, comprising and means for controlling the input quantity and rate of air and fuel into said burner so as to attain and maintain a relatively uniform though gradually decreasing operating temperature in and consequent gases discharged from said gas exhaust device to the atmosphere. 13. A burner unit for a low intensity radiant heater a burner conduit adapted to be conjoined to and com- -m-unicate with an air intake section,

an air flow deflecting member generating a substantial pressure drop on the downstream side thereof arradiation of energy from said radiant conduit through- 20 ranged concentrically in said burner conduit and havout the effective length of said conduit, and to coning substantially the entire perimeter of said memtrol the maximum and minimum temperature limits ber spaced slightly apart from said burner conduit over the effective length of said conduit and the whereby to initially eifect a relatively tubular stream rate of decrease of such temperature within said of air flow along and adjacent the inner wall surface limits. of said burner conduit and a relatively helically swirl- 9. The system defined in claim 8, and including ing stream of air flow within said tubular stream and a reflector supported upon and disposed adjacent but closely adjacent and progressively interspersing and spaced from said radiant conduit throughout the efintermixing therewith, fective extent thereof to reflect and direct radiant a fuel jet secured to said air flow deflecting member energy emitted by said conduit toward the areas to axially thereof and therethrough and directed downbe heated. stream thereof, comprising 10. The system defined in claim 8, and including a burner jet, means for suspending said air intake section, said burner a tubular member having one end conjoined to and unit, said radiant conduit and said gas exhaust secand communicating with said burnerjet and havtion from the superstructure of said structure having ing its discharge end disposed through and exareas to be heated. tending downstream of said air flow deflecting 11. The system defined in claim 8, wherein member, and having at least one air port through said air intake section and said gas exhaust section are its wall for the admission of air adjacent said arranged concentrically, burner jet to effect a combustible mixture of said air intake section being disposed concentrically air and fuel adjacent the exit end of said within and spaced apart from said gas exhaust burner jet, section. controlled means in said burner conduit for igniting 12. The system defined in claim 11, and including said combustible mixture,

a perforated plate arranged between said air intake secand means for supplying and controlling the supply tion and said gas exhaust section to vent exhaust of fuel to said burnerjet.

17. The structure defined in claim 16, and including an air flow limiting damper at the air input end of said burner conduit.

system wherein said heater system is open at its outer ends and closed throughout its entire intermediate extent, comprising 18. The structure defined in claim 13, and including an air flow switch, a first tubular pressure-sensing member communicata burner conduit adapted to be conjoined to and communicate with an air intake section, an air flow deflecting member generating a substaning with said switch and operatively connected thereto, and having its digital end disposed in said burner unit conduit downstream of said air flow deflecting tial pressure drop on the downstream side thereof member and adjacent the zone of flame propagaarranged concentrically in said burner conduit and tion, having substantially the entire perimeter of said mema second tubular pressure-sensing member communiber spaced slightly apart from said burner conduit, eating with and operatively connected to said switch, whereby to initially effect a relatively tubular stream and having its digital end disposed in said burner unit of air flow along and adjacent the inner wall surface conduit upstream of said air flow deflecting member, of said burner conduit and a relatively helically swirlmeans connecting said air flow switch with said means ing stream of air flow within said tubular stream and pp y q and controlling the pp y f l t s id closely adjacent and progressively interspersing and f l for p f y controlllng the Shut-01f 0f intermixing therewith, said fuel supply to said burner et when the presa burner fuel jet secured to said air flow deflecting sures on both sldes 9 531d P P member axially thereof and therethrough and directed 23533: Predetermmed relatlvely equlhbnum downstream thereof for i (ilscharge of i 19. The structure defined in claim 16, and including ports through the body of said air flow deflecting meman air flow Switch ber and spacied utlvardly i sald burner Jet the a first tubular pressure-sensing member communicating Passage of an Idanydy afhacent burner let for with said switch and operatively connected thereto, effecting a combustible mixture of arr and fueladav and having its digital end disposed and Said burner lacent the exit end of Said burner J and Spaced unit conduit downstream of said air flow deflecting and of such magnitude in Said y as to produce a member and adjacent the zone of flame propagation, relatively stable and eflicient flame propagation, a second tubular pressure-sensing member communicating with and operatively connected to said switch, and having its digital end disposed in said burner unit conduit upstream of said air flow deflecting member,

means connecting said air flow switch with said means supplying and controlling the supply of fuel to said burner jet for operatively controlling the shut-off of said fuel supply to said burner jet when the pressures on both sides of said air flow deflecting member reach predetermined relatively equilibrium proportions.

20. The system defined in claim 8, and including an air flow switch,

21. The structure defined in claim 13, wherein said ports through said body are disposed radially of and spaced from the axis of said fuel jet intermediate the axis and the outer perimeter of said air flow deflecting member, and comprise openings of a total area suflicient to pass air forming a combustible mixture with the fuel issuing from said burner jet,

said ports being so disposed through said body as to substantially limit the amount of reduced pressure immediately adjacent the downstream face of said air flow deflecting member.

22. A low intensity radiant heater system for a structure having space areas to be heated, comprising a plurality of air intake conduit sections each having its air intake opening disposed for admission of air which is relatively free of dirt and contaminants of a corrosive or orifice-occluding character,

a burner unit communicating with and connected to each air intake conduit section,

a radiant conduit disposed in an area to be heated and communicating with and connected to a burner unit,

a manifold conduit connected to and communicating with the exhaust discharge end of each radiant conduit to conduct the exhaust gases therefrom,

a gas exhaust section including a gas exhaust fan device communicating with and connected to said manifold conduit for constantly maintaining a relatively predetermined negative pressure in each said air intake sections, said burner units, said radiant conduits and said manifold conduit, and for constantly maintaining a positive pressure above atmospheric pressure in an exhaust gas discharge tube connected to and communicating with said exhaust fan device, said gas exhaust discharge tube having its discharge opening in an area open to the atmosphere outside of the space areas being heated by said radiant conduits,

each said burner unit comprising a burner conduit conjoined to and communicating with said air intake section, an air flow deflecting member generating a substantial pressure drop on the downstream side thereof arranged concentrically with said burner conduit and having substantially the entire perimeter of said member spaced slightly apart from said burner conduit, whereby to initially effect a relatively tubular stream of air fiow along and adjacent the inner wall surface of said burner conduit and a relatively helically swirling stream of air flow within said tubular stream and closely adjacent and progressively interspcrsing and intermixing therewith,

a fuel jet secured to said air flow deflecting member axially thereof and therethrough and directed downstream thereof for the discharge of fuel,

ports through the body of said air flow deflecting member and spaced outwardly of said burner jet for the passage of air relatively adjacent the burner jet for effecting a combustible mixture of air and fuel adjacent the exit end of said burner jet and so spaced and of such magnitude in said body as to produce a relatively stable and eflicient flame propagation,

controlled means in said burner conduit for igniting said combustible mixture,

and means for supplying and controlling the supply of fuel to said burner jet,

each said radiant conduit producing radiant emissive energy upon convective and radiative absorption of the thermal energy progressively generated by the intermixing of the burner flame, said swirling helical stream of air, said tubular stream of air, and the resultant products of combustion, and means for controlling the input quantity and rate of air and fuel supply into each said burner unit so as to attain and maintain a relatively uniform though gradually decreasing operating temperature in and consequent radiation of energy from each said radiant conduit throughout the effective length of each said radiant conduit, and to control the maximum and minimum temperature limits over the effective length of said conduit and the rate of decrease of such temperature within said limits. 23. The system defined in claim 22, and including a reflector supported upon and disposed adjacent but spaced from each said radiant conduit throughout the effective extent thereof to reflect and direct radiant energy emitted by each said radiant conduit toward the areas to be heated. 24. The system defined in claim 22, and including means for suspending each said air intake section, each said burner unit, each said radiant conduit and said gas exhaust section from the superstructure of said structure having areas to be heated. 25. The system defined in claim 22, and including an air flow limiting damper at the air intake end of each said burner conduit. 26. The system defined in claim 22, wherein said air intake sections, said burner units and said radiant conduits are arranged in a parallel series.

References Cited UNITED STATES PATENTS 2,391,447 12/1945 Edge.

2,505,313 4/1950 Wagoner 23753 2,759,472 8/ 1956 Cartter.

2,941,525 6/ 1960 Harshfield.

3,212,493 10/1965 Lacey.

FREDERICK KETTERER, Primary Examiner.