US20150211752A1 - Radiant heat reflector and heat converter - Google Patents
Radiant heat reflector and heat converter Download PDFInfo
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- US20150211752A1 US20150211752A1 US14/680,441 US201514680441A US2015211752A1 US 20150211752 A1 US20150211752 A1 US 20150211752A1 US 201514680441 A US201514680441 A US 201514680441A US 2015211752 A1 US2015211752 A1 US 2015211752A1
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- 238000002485 combustion reaction Methods 0.000 description 2
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D5/00—Hot-air central heating systems; Exhaust gas central heating systems
- F24D5/06—Hot-air central heating systems; Exhaust gas central heating systems operating without discharge of hot air into the space or area to be heated
- F24D5/08—Hot-air central heating systems; Exhaust gas central heating systems operating without discharge of hot air into the space or area to be heated with hot air led through radiators
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D19/00—Details
- F24D19/06—Casings, cover lids or ornamental panels, for radiators
- F24D19/062—Heat reflecting or insulating shields
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
- F24C15/00—Details
- F24C15/22—Reflectors for radiation heaters
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24D—DOMESTIC- OR SPACE-HEATING SYSTEMS, e.g. CENTRAL HEATING SYSTEMS; DOMESTIC HOT-WATER SUPPLY SYSTEMS; ELEMENTS OR COMPONENTS THEREFOR
- F24D3/00—Hot-water central heating systems
- F24D3/02—Hot-water central heating systems with forced circulation, e.g. by pumps
Definitions
- Embodiments described herein relate to a radiant heater, and more particularly to a reflector and a heat converter in a radiant heater.
- tubular conduits e.g., “tubes”
- a heated fluid (provided by a power plant) passes through the tube and heats the tube.
- the tube radiates heat waves (e.g., heat transfer by radiation) to an adjacent area, such as toward the floor.
- a reflector may direct the radiated heat in a desired direction.
- a heating system of this type may warm objects or people on loading docks, near open doorways, or where conditions may cause a high heat loss.
- FIG. 1A is a diagram of a radiant heater
- FIG. 1B is a cross-sectional drawing of the radiant heater of FIG. 1A ;
- FIG. 2A is a diagram of an exemplary embodiment of a radiant heater
- FIG. 2B is a cross-sectional drawing of the exemplary radiant heater of FIG. 2A ;
- FIG. 3A is a perspective drawing of an exemplary embodiment of a reflector in the exemplary radiant heater of FIGS. 2A and 2B ;
- FIG. 3B is a disassembled, cross-sectional drawing of the exemplary reflector of FIG. 3A ;
- FIG. 4A is a cross-sectional drawing of an exemplary embodiment of a radiant heater with a heat converter hood
- FIG. 4B is a perspective drawing of the exemplary reflector and exemplary heat converter hood of the radiant heater of FIG. 4A ;
- FIG. 5A is a projection drawing of an exemplary converter hood of the radiant heater of FIG. 4A ;
- FIG. 5B is a cross-sectional drawing of the exemplary converter hood of FIG. 5A ;
- FIG. 5C is a disassembled, cross-sectional drawing of the exemplary converter hood of FIG. 5A ;
- FIG. 6 is a cross-sectional drawing of an exemplary embodiment of a radiant heater including an insulation layer
- FIGS. 7A through 7F are plots of exemplary curves that describe the reflector of FIG. 3A ;
- FIGS. 8A through 8D are additional plots of exemplary curves that describe the reflector of FIG. 3A .
- Embodiments described herein provide for a reflector to reflect heat radiated from a tube.
- a reflector to reflect heat radiated from a tube.
- One of these embodiments allows the reflected heat to avoid the tube itself, e.g., the reflected heat energy being directed around the tube rather than impinging on the tube.
- Other embodiments provide for a hood converter to capture heat, where the hood may radiate the captured heat.
- FIG. 1A is a diagram of a radiant heater 100 .
- Radiant heater 100 may hang from a ceiling, for example, for the purpose of radiating heat downward toward a floor.
- FIG. 1B is a cross-sectional drawing of radiant heater 100 of FIG. 1A .
- Radiant heater 100 includes an emitting tube 102 , a reflector 104 , and a space 106 separating emitting tube 102 and reflector 104 .
- Radiant heater 100 may also include an insulation layer 114 , shown only in FIG. 1B .
- Emitting tube 102 carries a heated fluid (e.g., hot flue gas), which heats emitting tube 102 to high temperatures.
- emitting tube 102 radiates heat waves 110 (e.g., heat wave 110 - 1 , 110 - 2 , 110 - 3 , and 110 - 4 , shown in FIG. 1B as solid lines parallel to the direction of travel of the waves).
- heat wave 110 - 1 radiates directly toward a floor 108 , where the heat is desired, for example.
- Heat waves 110 - 2 , 110 - 3 , and 110 - 4 radiate toward reflector 104 .
- Reflector 104 reflects heat waves 110 - 2 , 110 - 3 , and 110 - 4 toward floor 108 as reflected heat waves 112 (e.g., heat waves 112 - 1 , 112 - 2 , and 112 - 3 shown in FIG. 1B as dashed lines parallel to the direction of travel of the waves).
- Heat wave 112 - 3 is also reflected toward emitting tube 102 and emitting tube 102 may absorb portions of heat wave 112 - 3 and its energy. In this example, portions of heat wave 112 - 3 may not reach floor 108 and energy may be potentially lost.
- Space 106 and reflector 104 may become hot themselves (e.g., the air in space 106 being in contact with emitting tube 102 (conduction), the convection in the air, and the contact of the air with reflector 104 ).
- an insulation layer 114 may reside above reflector 104 .
- FIG. 2A is a perspective drawing of an exemplary radiant heater 200 in one embodiment.
- Radiant heater 200 may hang from a ceiling, for example, for the purpose of radiating heat downward toward a floor.
- FIG. 2B is a cross-sectional drawing of radiant heater 200 .
- Radiant heater 200 includes an emitting tube 202 , a reflector 204 , and a space 206 separating emitting tube 202 and reflector 204 .
- Emitting tube 202 carries heated fluid (e.g., hot flue gas), which may heat emitting tube 202 to high temperatures.
- heated fluid e.g., hot flue gas
- emitting tube 202 radiates heat waves 210 (shown in FIG. 2B as solid lines parallel to the direction of travel of the wave).
- emitting tube 102 radiates heat waves in all directions, only heat waves radiated toward the left portion of reflector 204 are shown in FIG. 2B for simplicity.
- Reflector 204 reflects heat waves 210 toward a floor 208 as reflected heat waves 212 (shown in FIG. 2B as dashed lines parallel to the direction of travel of the waves). Unlike reflector 104 , however, reflector 204 is shaped to reflect heat waves 210 substantially around emitting tube 202 . This embodiment may allow for fewer heat waves being reflected back to and be absorbed by emitting tube 202 . Instead, this embodiment may allow for more heat waves (e.g., more energy) to be reflected toward floor 208 , where the heat is desired. In one embodiment, substantially all the radiation that impinges on reflector 204 is reflected around emitting tube 202 . A more detailed description of embodiments of the shape of reflector 204 is discussed below with respect to FIGS. 7A through 7F and 8 A through 8 D.
- reflector 204 may include a first curved surface 204 - 1 and a second curved surface 204 - 2 that meet at a junction 220 .
- Emitting tube 202 may be considered a line source P (also referred to as “center axis P” or “point source P”) emitting radiation 210 .
- the properties and shape of first surface 204 - 1 allows emitted radiation 210 to be reflected (e.g., radiation 212 ) around emitting tube 202 , with a clearance distance D.
- the dimensions of emitting tube 202 may be sized to have a radius greater than R.
- emitting tube 202 may have a radius of R+D before reflected radiation 212 would impinge on emitting tube 202 .
- the area/volume from line source P to R+D may be known as a reflection-free envelope, inside of which may be substantially free of reflected radiation.
- emitting tube 202 may be sized larger, in one embodiment emitting tube 202 is kept a distance from the reflection envelope and junction 220 .
- the distance from emitting tube 202 to junction 220 may be between 35 to 40 millimeters (mm), 30 to 35 mm, 25 to 30 mm, 20 to 25 mm, 15 to 20 mm, 10 to 15 mm, 5 to 10 mm, or less than 5 mm.
- the distance from emitting tube 202 to junction 220 is 29.29 mm, where the radius of emitting tube 202 is 38.05 mm and the distance between center axis P is 67.34 mm.
- the distance from emitting tube 202 to junction 220 is 16.54 mm, where the radius of emitting tube 202 is 50.8 mm and the distance between center axis P is 67.34.
- the dimensions of emitting tube 202 may also be scaled smaller such that its radius may be smaller than radius R shown in FIG. 2B .
- the dimensions of reflector 204 may be correspondingly scaled down before reflected radiation 212 would impinge on emitting tube 202 .
- the dimensions of reflector 204 may be increased and reflected radiation 212 may still avoid emitting tube 202 .
- reflector 204 may be designed to accommodate many different sizes of emitting tubes.
- FIG. 3A is a perspective drawing of reflector 204 .
- Reflector 204 may be formed of a metal, such as stainless steel.
- reflector 204 is formed of one sheet of metal that is continuous from a first lip 304 - 1 to a second lip 304 - 2 (lips 304 ) of reflector 204 .
- Lips 304 may provide strength to support the weight of reflector 204 when installed and may provide rigidity along the length of reflector 204 (e.g., parallel with emitting tube 202 ).
- reflector 204 may be rolled, drawn, or pressed into the shape shown.
- reflector 204 may be constructed of aluminized steel.
- reflector 204 may be formed of multiple (e.g., two) sheets of metal.
- FIG. 3B is a disassembled, cross-sectional drawing of reflector 204 formed from two sheets of metal.
- reflector 204 comprises a first sheet 302 - 1 and a second sheet 302 - 2 .
- Reflector 204 may include more or fewer portions than shown.
- First and second sheets 302 - 1 and 302 - 2 may be rolled, drawn, or pressed into the shapes shown. Sheets 302 - 1 and 302 - 2 may allow for a compact, disassembled reflector 204 for easier transportation of radiant heater 200 .
- First sheet 302 - 1 may include first lip 304 - 1 and a first flange 306 - 1 that may run along junction 220 .
- Flange 306 - 1 may provide rigidity along the length of sheet 302 - 1 and may overlap with a portion of second sheet 302 - 2 to allow first and second sheets 302 - 1 and 302 - 2 to be joined together by, for example, bolts along the length of such an overlap.
- Second sheet 302 - 2 may include second lip 304 - 2 and a second flange 306 - 2 .
- Flange 306 - 2 may also overlap with a portion of first sheet 302 - 1 to allow first and second sheets 302 - 1 and 302 - 2 to be joined together by, for example, bolts along the length of such an overlap.
- a joining strip 310 may overlap with first sheet 302 - 1 and second sheet 302 - 2 along their lengths. Joining strip 310 may allow first and second sheets 302 - 1 and 302 - 2 to be joined together by, for example, bolts along the length of the overlap between joining strip 310 and first sheet 302 - 1 and bolts along the length of the overlap between joining strip 310 and second sheet 302 - 2 . In an embodiment with joining strip 310 , for example, flanges 306 - 1 and 306 - 2 may be omitted.
- joining strip 310 is short compared to the length of reflector 204 .
- multiple joining strips may be used along the length of reflector 204 .
- a joining strip 310 may be used at each end of reflector 204 and a joining strip 310 may be used in the middle of reflector 204 .
- reflector 104 in the configuration of FIG. 1A was compared to reflector 204 (in the configuration of FIG. 2A ).
- reflector 204 (1) increased maximum radiation measured under the radiant heater by 12%; (2) increased global radiation by 1.2%; (3) decreased convective heat from 234° C. to 175° C., (4) lowered the highest temperature (measured on top of emitting tube 102 ) by 11%, and (5) increased combustion efficiency of the power plant by 0.6%.
- FIG. 4A is a cross-sectional drawing of one embodiment of an exemplary radiant heater 400 with a heat converter hood 402 .
- converter hood 402 converts and directs heat energy.
- Radiant heater 400 like radiant heater 200 , includes emitting tube 202 and reflector 204 .
- Converter hood 402 is placed above reflector 204 to form a space 404 between reflector 204 and converter hood 402 .
- FIG. 4B is a perspective drawing of radiant heater 400 showing an exemplary positioning of converter hood 402 with respect to reflector 204 .
- the distance from junction 220 of reflector to converter hood 402 may range, for example, from 40 to 35 mm, 35 to 30 mm, 30 to 25 mm, 25 to 20 mm, 20 to 15 mm, 15 to 10 mm, 10 to 5 mm, or less than 5 mm. In one embodiment, the distance from junction 220 of reflector 204 to converter hood 402 is approximately 24 mm.
- Emitting tube 202 becomes hot as a result of hot gasses passing through emitting tube 202 .
- emitting tube 202 heats the air in space 206 surrounding emitting tube 202 (e.g., through contact of the air with emitting tube 202 , or conduction). Heat may also transfer through the air in space 206 as well as the air in space 404 between reflector 204 and converter hood 402 (e.g., through convection). Reflector 204 may also conduct heat from space 206 to space 404 .
- Hot air in space 404 is depicted in FIG. 4A as amorphous shapes.
- Heat may build up in space 404 between reflector 204 and converter hood 402 , and particularly at the surface of converter hood 402 by the convection of the air in space 404 .
- converter hood 402 may capture this heat energy (e.g., become hot itself) and may begin to radiate energy.
- converter hood 402 may convert the heat energy transferred through convection to the surface of converter hood 402 into heat energy radiated through space.
- FIG. 4A converter hood 402 radiates heat waves 406 (also referred to as radiation 406 , depicted as solid lines in the direction of the travel of the wave). Radiation 406 is in addition to reflected radiation 212 and emitted radiation 210 .
- Converter hood 402 may include corrugated portions to capture heat more effectively and to help distribute the heat energy throughout space 404 . Capturing and converting heat energy around emitting tube 202 , by converter hood 402 , allows emitting tube 202 to operate at lower temperatures. Operating emitting tube 202 at lower temperatures may extend the life of emitting tube 202 , or may allow more hot fluid to pass through emitting tube 202 without reaching its maximum rated temperatures.
- FIG. 5A is a perspective drawing of converter hood 402 .
- FIG. 5B is a cross-sectional drawing of converter hood 402 .
- Converter hood 402 may include angled or corrugated portions 508 along the sides and a flat portion 510 along the middle of converter hood 402 .
- Converter hood 402 may be formed from a single piece of sheet metal from one end (e.g., a first flange 506 - 1 ) to the other end (e.g., a second flange 506 - 2 ).
- Converter hood 402 may be rolled, drawn, or pressed into the shape.
- Corrugated portions 508 may increase the surface area of converter hood 402 , allowing it to absorb more heat and convert more energy into radiated heat.
- corrugated portions 508 include angles (e.g., angle 520 ) between 35 to 50° (e.g., 35 to 40°, 40 to 45°, 45 to 50°), 50 to 60°, or 60 to 70°, or 25 to 35°.
- Corrugated portions 508 may include angles greater than 70° or less than 25°, for example.
- corrugated portions 508 include 45° angles, increasing the area of converter hood 402 by a factor of 1.414.
- Corrugated portions 508 may also trap hot air and allow heat to be more evenly distributed along converter hood 402 than if, for example, converter hood 402 were not corrugated at all, which may result in more hot air accumulating at the top portion of converter hood 402 .
- corrugated portions may include curves rather than angles.
- Flat portion 510 lacks corrugations, which may also help prevent hot air from accumulating at the top portion of converter hood 402 . Like corrugated portions 508 , flat portion 510 may allow heat to be more evenly distributed along converter hood 402 than if, for example, the top portion were corrugated.
- FIG. 5C is a disassembled, cross-sectional drawing of exemplary converter hood 402 .
- converter hood 402 may include a first side portion 502 - 1 , a second side portion 502 - 2 , a first top potion 504 - 1 , and a second top potion 504 - 2 .
- Converter hood 402 may include more or fewer portions than shown.
- Portions 502 - 1 , 502 - 2 , 504 - 1 , and 504 - 2 may allow for a more compact, disassembled converter hood 402 for easier transportation of radiant heater 400 .
- Portions 502 - 1 , 502 - 2 , 504 - 1 , and 504 - 2 may be rolled, drawn, or pressed into the shapes shown.
- First side portion 502 - 1 may include corrugated portion 508 and first flange 506 - 1 .
- First flange 506 - 1 may provide for rigidity along the length of converter hood 402 .
- First flange 506 - 1 may also hold an insulation layer (not shown, discussed below) in place.
- Corrugated portion 508 may also provide for rigidity along the length of converter hood 402 in addition to the features discussed above.
- Second side portion 502 - 2 may include corrugated portion 508 and second flange 506 - 2 , which may provide the same features as the corresponding elements of first side portion 502 - 1 .
- First top portion 504 - 1 may include corrugated portion 508 and flat portion 510 .
- second top portion 504 - 2 may include corrugated portion 508 and flat portion 510 .
- Part of first top portion 504 - 1 may overlap with first side portion 502 - 1 , allowing first top portion and first side portion 506 - 1 to be bolted together.
- part of second top portion 504 - 2 may overlap with second side portion 502 - 2 , allowing second top portion 504 - 2 and second side portion 502 - 2 to be bolted together.
- Part of first top portion 504 - 1 may also overlap with part of second top portion 504 - 2 , allowing first top portion 504 - 1 and second top portion 504 - 2 to be bolted together.
- FIG. 6 is a cross-sectional drawing of a radiant heater 600 including an insulation layer 606 .
- Radiant heater 600 like radiant heater 200 , includes emitting tube 202 , reflector 204 , and converter hood 402 .
- emitting tube 202 , space 206 , reflector 204 , space 404 , and converter hood 402 may become hot.
- Insulation layer 606 may reside above converter hood 402 .
- Insulation layer 606 may slow heat transfer in the upward direction and reduce heat loss.
- insulation layer 606 may allow converter hood 402 to reach higher temperatures than without layer 606 , allowing hood 402 to reradiate more energy with layer 606 than without layer 606 .
- Converter hood 402 may hold insulation layer 606 in place using flanges 506 - 1 and 506 - 2 or other mechanical attachment means.
- FIG. 7A is a plot of an involute curve 704 of a circle 702 , which may be used to define first surface 204 - 1 and second surface 204 - 2 of reflector 204 in radiant heater 200 .
- An involute curve may be obtained by attaching an imaginary, taut string to a first curve and tracing the string's free end as it is wound onto that first curve, thus creating the involute curve.
- Circle 702 is the first curve and that line 706 - 1 is a string 706 attached to circle 702 at a fixed point 708 on one end, and to a pencil 712 on the other end.
- Circle 702 may represent an emitting tube, such as emitting tube 202 .
- the length of string 706 is the same as the circumference of circle 702 .
- string 706 is moved in a direction 710 , string 706 becomes wound around circle 702 and pencil 712 traces involute curve 704 .
- String 706 is shown in many positions ( 706 - 1 , 706 - 2 , etc.) as string 706 is wound around circle 702 .
- involute curve 704 Upon one complete revolution of string 706 around circle 702 , involute curve 704 intersects circle 702 at point 708 because the length of string 706 is the same as the circumference of circle 702 . Involute curve 704 may also be described as the unwinding of string 706 from circle 702 .
- involute curve 704 One property of involute curve 704 is that tangents of circle 702 are perpendicular to involute curve 704 . Because lines 706 - 1 through 706 - 11 are tangent to circle 702 , lines 706 - 1 through lines 706 - 11 are all perpendicular to involute curve 704 .
- FIG. 7B demonstrates another property of involute curve 704 . For simplicity, FIG. 7B shows circle 702 , involute curve 704 , and tangent line 706 - 7 of FIG. 7A . In FIG. 7B , a line is drawn from the center of circle 702 to the intersection of involute curve 704 with tangent line 706 - 7 .
- an angle A between line 710 and involute curve is less than 90°, e.g., angle A is I degrees less than 90°.
- line 710 were a heat wave, such as one of heat waves 210 , then, according to Snell's Law, the angle of reflection is equal to the angle of incidence.
- a reflected wave 712 is R degrees (R equal to I) below tangent line 706 - 7 .
- Being below tangent line 706 - 7 means that reflected wave 712 clears circle 702 (e.g., emitting tube 202 ).
- involute curve 704 may vary in distance to tangents of circle 702 (e.g., emitting tube 202 ), but the distance, in one embodiment, may not exceed one half of the circumference
- the relationship shown in FIG. 7B may apply to all lines (e.g., emitted waves 210 ) from the center of circle 702 (e.g., emitting tube 202 ).
- an emitted wave 710 ′ is reflected away from circle 702 as reflected wave 712 ′.
- FIG. 7D shows another involute curve 704 ′, which is symmetrical to involute curve 704 along a center line 720 .
- FIG. 7E shows involute curve 704 and involute curve 704 ′ superimposed on each other.
- FIG. 7F shows only a portion of the superimposed involute curves 704 and 704 ′, the portion shown having the characteristics of reflector 204 discussed above with respect to FIG. 2B .
- heat waves emitted from emitting tube 202 e.g., circle 702
- emitting tube 202 is spaced apart from reflector 204 .
- 204 may also be referred to as a “bi-involute” reflector.
- the spacing between emitting tube 202 and reflector 204 may be the result of fixed point 708 not being directly above the center of circle 702 .
- fixed point 708 is approximately 29° away from being directly above the center of circle 702 .
- Other angles are possible, such as an angle between approximately 0-5°, 5-10°, 10-15°, 15-20°, 20-25°, 25-30°, 30-35°, etc. (e.g., 5n to 5n+5, where n is zero or a positive integer). Angles above 360° are also possible.
- Curves 704 and 704 ′ may formed by circle 702 with a diameter of approximately 76.1 mm.
- diameters are possible, such as between 5-10 mm, 10-20 mm, 20-30 mm, 30-40 mm, 40-50 mm, 50-60 mm, 60-70 mm, 70-80 mm, 80-90 mm, etc. (e.g., 10u to 10u+10 mm, where u is a positive integer).
- the surfaces of reflector 204 may end a distance H above the bottom of emitting tube 202 .
- H is chosen such that direct heat waves 210 disperse as widely as possible, but do not impinge on converter hood 402 .
- H may be (1) large enough such that a straight line from line source P to the space just below the bottom edge of converter hood 402 is unobstructed by reflector 204 ; and (2) small enough such that a straight line from line source P to the space just above the bottom edge of converter hood 402 is obstructed by reflector 204 .
- direct heat waves 210 are dispersed as widely as possible, and heat waves 210 that would otherwise impinge on converter hood 402 are reflected.
- This embodiment also allows for more radiated heat waves 406 (emitted by converter hood 402 ) to reach floor 208 without impinging on converter hood 402 (as compared, for example, to H being zero or extending below the edge of converter hood 402 ).
- these properties of reflector 204 may increase the heating efficiency of radiant heater 200 and radiant heater 400 . These properties may also allow the temperature of emitting tube 202 to be lower than in conventional systems (as compared to emitting tube 102 , for example).
- FIG. 8A is a diagram of an alternative involute curve 804 around circle 702 .
- Involute curve 804 begins at fixed point 808 , which is directly above the center of circle 702 , unlike fixed point 708 which is not directly above the center of circle 702 .
- FIG. 8B shows another involute curve 804 ′, which is symmetrical to involute curve 804 along a center line 820 .
- FIG. 8C shows involute curve 804 and involute curve 804 ′ superimposed on each other.
- FIG. 8D shows only a portion of the superimposed involute curves 804 and 804 ′ (e.g., reflector 204 ′), the portion shown having the characteristics similar to reflector 204 discussed above with respect to FIG. 2B .
- heat waves emitted from emitting tube 202 are reflected by reflector 204 ′ down and away from emitting tube 202 .
- the distance between emitting tube 202 and reflector 204 ′ is less than with reflector 204 .
- an emitter tube may be used that has a smaller radius than emitting tube 202 . In this case, the smaller emitter tube may be spaced farther from reflector 204 ′, but may still have the same center as circle 702 .
- reflector 204 / 204 ′ allows for more reflected energy to pass around emitting tube 202 .
- the shape of reflector 204 / 204 ′ may help reduce heat buildup under the reflector. Reducing heat under reflector 204 / 204 ′ may result in lower temperatures on the hottest points of emitting tube 202 .
- reflector 204 / 204 ′ may increase the reflection efficiency and may increase the radiant efficiency of a heater. This greater efficiency may increase the reliability of the heater and the lifetime of the heater, as component temperature (e.g., the temperature of emitting tube 202 ) may be reduced. Because reflector 204 / 204 ′ may reduce temperatures, relative to reflector 104 , reflector 204 / 204 ′ may allow an increased heat input to achieve the same reliability as reflector 104 .
- junction 220 is directly above emitting tube 202 .
- a central axis (not shown) passes through source point P (the center of emitting tube 202 ) and junction 220 .
- Surface 204 - 1 is such that radiation impinging on reflector 204 closer to junction 220 (and the central axis) is reflected (in its first reflection) farther away from the central axis than radiation impinging on reflector 204 farther away from junction 220 .
- the reflected radiation creates the cross pattern shown in FIG. 2B .
- “Farther away,” in this example means that the reflected energy (in the direction of its first reflection that does not cross the central axis) impinges floor 208 farther away from the central axis.
- first surface 204 - 1 provides for a substantially even distribution of the reflected radiated energy—including areas directly under emitting tube 202 as well as outside the umbrella of reflector 204 .
- Embodiments described herein may allow for (1) higher heat output and/or higher radiant heat intensity, given the same input, for a radiant heater as compared to a conventional heater; (2) reduction of heat loss through roofs and walls; (3) lower and more even air temperatures in a heated area; (4) less thermal loss (e.g., through convection given higher radiant heat downward); (5) faster response and stabilization (e.g., resulting from increased radiant efficiency); and (6) reduced energy consumption (e.g., less fuel spent to heat fluids passing through emitting tubes) and lower carbon dioxide emissions.
- reflector 204 comprises a first sheet 302 - 1 and a second sheet 302 - 2 joined by multiple joining strips 310 .
- first sheet 302 - 1 and second sheet 302 - 2 do not include flange 306 - 1 and flange 306 - 2 .
- an air gap may separate first sheet 302 - 1 and second sheet 302 - 2 (e.g., at junction 220 ), where the air gap is interrupted by joining strips 310 .
- heat transfer may occur through convection by air passing from space 206 to space 404 through the air gap between first and second sheets 302 - 1 and 302 - 2 .
- Converter hood 402 may include an angle immediately above junction 220 to reflect any radiation away from emitting tube 202 .
- converter hood 402 may include a material directly above junction 220 to absorb the energy emitted by emitting tube 202 so that captured energy may be re-radiated from converter hood 402 .
- Air gaps or holes may also be placed in other locations on reflector 204 , such as periodically at the highest points of reflector 204 along its length.
- reflector 204 and/or emitting tube 202 may be suspended from converter hood 402 by a suspension mechanism (e.g., cables or long bolts). In this embodiment, heat may be transferred by conduction of heat along the suspension mechanism directly from reflector 204 /space 204 to converter hood 402 . In another embodiment, reflector 204 and/or emitting tube 202 may be connected to converter hood 402 through a metal conductor (other than a suspension mechanism) to transfer heat by conduction from reflector 204 and/or emitting tube 202 to converter hood 402 .
- a suspension mechanism e.g., cables or long bolts
- reflector 204 may be approximately 300 mm wide from edge to edge and 100 mm tall. In one embodiment, converter hood 402 may be approximately 700 mm wide from edge to edge and 170 mm tall.
- reflector 204 may be used in a radiant heater without the use or converter hood 402 .
- an insulation layer (not shown) may be laid above reflector 204 to slow the heat transfer upward to reduce heat loss.
- converter hood 402 may be used with reflectors of any shape, including reflector 104 of radiant heater 100 .
- a curved surface other than a circle e.g., an ellipse
- emitting tube 202 may still be within the radiation-free envelope created by the involute curved surface.
- shapes that approximate or are substantially similar to the shape of reflector 204 and reflector 204 ′ are possible.
- first lip 304 - 1 and second lip 304 - 2 of reflector 204 may include another bend inward toward first sheet 302 - 1 and second sheet 302 - 2 , respectively.
- radiation 406 emitted by converter hood 402 may reflect away from reflector 204 rather than being trapped in the area formed by lips 304 and sheets 302 .
- reflector 204 and converter hood 402 may both be mounted on the same support structure such that the spatial relationship between the two remains the same.
- reflector 204 , converter hood 402 , and emitting tube 202 may be mounted on the same support structure such that the spatial relationship between the three remains the same.
- emitting tube 202 and reflector 204 may be mounted on the same support structure so that the spatial relationship between the two remains the same.
- reflector 204 , converter hood 402 , and/or emitting tube 202 may be sold, packaged, and shipped in a manner convenient for installation.
- reflector 204 and converter hood 402 may be integrally formed.
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Abstract
A system may include a tube through which hot fluid is transported from one end to another, wherein the tube radiates heat energy and transfers heat energy to surrounding air by convection. The system may also include a reflector that reflects the radiated heat and a hood that captures the heat energy from the surrounding air through convection, wherein the hood radiates the captured heat energy. The reflector may include a bi-involute curved surface.
Description
- This application claims the benefit of U.S. Provisional Patent Application No. 61/237,376 filed Aug. 27, 2009, which is hereby incorporated by reference.
- Embodiments described herein relate to a radiant heater, and more particularly to a reflector and a heat converter in a radiant heater.
- Radiant heaters are frequently used in warehouses, factories, and commercial settings to provide a warm environment during cold weather. In such systems, tubular conduits (e.g., “tubes”) may hang from the ceiling or other overhead structure. A heated fluid (provided by a power plant) passes through the tube and heats the tube. The tube radiates heat waves (e.g., heat transfer by radiation) to an adjacent area, such as toward the floor. A reflector may direct the radiated heat in a desired direction. A heating system of this type may warm objects or people on loading docks, near open doorways, or where conditions may cause a high heat loss.
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FIG. 1A is a diagram of a radiant heater; -
FIG. 1B is a cross-sectional drawing of the radiant heater ofFIG. 1A ; -
FIG. 2A is a diagram of an exemplary embodiment of a radiant heater; -
FIG. 2B is a cross-sectional drawing of the exemplary radiant heater ofFIG. 2A ; -
FIG. 3A is a perspective drawing of an exemplary embodiment of a reflector in the exemplary radiant heater ofFIGS. 2A and 2B ; -
FIG. 3B is a disassembled, cross-sectional drawing of the exemplary reflector ofFIG. 3A ; -
FIG. 4A is a cross-sectional drawing of an exemplary embodiment of a radiant heater with a heat converter hood; -
FIG. 4B is a perspective drawing of the exemplary reflector and exemplary heat converter hood of the radiant heater ofFIG. 4A ; -
FIG. 5A is a projection drawing of an exemplary converter hood of the radiant heater ofFIG. 4A ; -
FIG. 5B is a cross-sectional drawing of the exemplary converter hood ofFIG. 5A ; -
FIG. 5C is a disassembled, cross-sectional drawing of the exemplary converter hood ofFIG. 5A ; -
FIG. 6 is a cross-sectional drawing of an exemplary embodiment of a radiant heater including an insulation layer; -
FIGS. 7A through 7F are plots of exemplary curves that describe the reflector ofFIG. 3A ; and -
FIGS. 8A through 8D are additional plots of exemplary curves that describe the reflector ofFIG. 3A . - The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. The foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
- Embodiments described herein provide for a reflector to reflect heat radiated from a tube. One of these embodiments allows the reflected heat to avoid the tube itself, e.g., the reflected heat energy being directed around the tube rather than impinging on the tube. Other embodiments provide for a hood converter to capture heat, where the hood may radiate the captured heat.
-
FIG. 1A is a diagram of aradiant heater 100.Radiant heater 100 may hang from a ceiling, for example, for the purpose of radiating heat downward toward a floor.FIG. 1B is a cross-sectional drawing ofradiant heater 100 ofFIG. 1A .Radiant heater 100 includes anemitting tube 102, areflector 104, and aspace 106 separatingemitting tube 102 andreflector 104.Radiant heater 100 may also include aninsulation layer 114, shown only inFIG. 1B . - Emitting
tube 102 carries a heated fluid (e.g., hot flue gas), which heats emittingtube 102 to high temperatures. As a result, emittingtube 102 radiates heat waves 110 (e.g., heat wave 110-1, 110-2, 110-3, and 110-4, shown inFIG. 1B as solid lines parallel to the direction of travel of the waves). As shown inFIG. 1B , heat wave 110-1 radiates directly toward afloor 108, where the heat is desired, for example. Heat waves 110-2, 110-3, and 110-4, on the other hand, radiate towardreflector 104. -
Reflector 104 reflects heat waves 110-2, 110-3, and 110-4 towardfloor 108 as reflected heat waves 112 (e.g., heat waves 112-1, 112-2, and 112-3 shown inFIG. 1B as dashed lines parallel to the direction of travel of the waves). Heat wave 112-3, however, is also reflected toward emittingtube 102 and emittingtube 102 may absorb portions of heat wave 112-3 and its energy. In this example, portions of heat wave 112-3 may not reachfloor 108 and energy may be potentially lost. -
Space 106 andreflector 104 may become hot themselves (e.g., the air inspace 106 being in contact with emitting tube 102 (conduction), the convection in the air, and the contact of the air with reflector 104). To slow heat transfer in the upward direction (e.g., away from floor 108) and to reduce heat loss, aninsulation layer 114 may reside abovereflector 104. -
FIG. 2A is a perspective drawing of an exemplaryradiant heater 200 in one embodiment.Radiant heater 200, likeradiant heater 100, may hang from a ceiling, for example, for the purpose of radiating heat downward toward a floor.FIG. 2B is a cross-sectional drawing ofradiant heater 200.Radiant heater 200 includes an emittingtube 202, areflector 204, and aspace 206separating emitting tube 202 andreflector 204. - Emitting
tube 202 carries heated fluid (e.g., hot flue gas), which may heat emittingtube 202 to high temperatures. As a result, emittingtube 202 radiates heat waves 210 (shown inFIG. 2B as solid lines parallel to the direction of travel of the wave). Although emittingtube 102 radiates heat waves in all directions, only heat waves radiated toward the left portion ofreflector 204 are shown inFIG. 2B for simplicity. -
Reflector 204 reflectsheat waves 210 toward afloor 208 as reflected heat waves 212 (shown inFIG. 2B as dashed lines parallel to the direction of travel of the waves). Unlikereflector 104, however, reflector 204 is shaped to reflectheat waves 210 substantially around emittingtube 202. This embodiment may allow for fewer heat waves being reflected back to and be absorbed by emittingtube 202. Instead, this embodiment may allow for more heat waves (e.g., more energy) to be reflected towardfloor 208, where the heat is desired. In one embodiment, substantially all the radiation that impinges onreflector 204 is reflected around emittingtube 202. A more detailed description of embodiments of the shape ofreflector 204 is discussed below with respect toFIGS. 7A through 7F and 8A through 8D. - As shown in
FIG. 2B ,reflector 204 may include a first curved surface 204-1 and a second curved surface 204-2 that meet at ajunction 220. Emittingtube 202 may be considered a line source P (also referred to as “center axis P” or “point source P”) emittingradiation 210. The properties and shape of first surface 204-1 allows emittedradiation 210 to be reflected (e.g., radiation 212) around emittingtube 202, with a clearance distance D. As shown inFIG. 2B , the dimensions of emittingtube 202 may be sized to have a radius greater than R. For example, emittingtube 202 may have a radius of R+D before reflectedradiation 212 would impinge on emittingtube 202. The area/volume from line source P to R+D may be known as a reflection-free envelope, inside of which may be substantially free of reflected radiation. - Although emitting
tube 202 may be sized larger, in oneembodiment emitting tube 202 is kept a distance from the reflection envelope andjunction 220. For example, the distance from emittingtube 202 tojunction 220 may be between 35 to 40 millimeters (mm), 30 to 35 mm, 25 to 30 mm, 20 to 25 mm, 15 to 20 mm, 10 to 15 mm, 5 to 10 mm, or less than 5 mm. In one embodiment, the distance from emittingtube 202 tojunction 220 is 29.29 mm, where the radius of emittingtube 202 is 38.05 mm and the distance between center axis P is 67.34 mm. In another embodiment, the distance from emittingtube 202 tojunction 220 is 16.54 mm, where the radius of emittingtube 202 is 50.8 mm and the distance between center axis P is 67.34. The dimensions of emittingtube 202 may also be scaled smaller such that its radius may be smaller than radius R shown inFIG. 2B . - Viewed in another way, the dimensions of
reflector 204 may be correspondingly scaled down before reflectedradiation 212 would impinge on emittingtube 202. Alternatively, the dimensions ofreflector 204 may be increased and reflectedradiation 212 may still avoid emittingtube 202. Thus,reflector 204 may be designed to accommodate many different sizes of emitting tubes. -
FIG. 3A is a perspective drawing ofreflector 204.Reflector 204 may be formed of a metal, such as stainless steel. In one embodiment,reflector 204 is formed of one sheet of metal that is continuous from a first lip 304-1 to a second lip 304-2 (lips 304) ofreflector 204. Lips 304 may provide strength to support the weight ofreflector 204 when installed and may provide rigidity along the length of reflector 204 (e.g., parallel with emitting tube 202). In this embodiment,reflector 204 may be rolled, drawn, or pressed into the shape shown. In one embodiment,reflector 204 may be constructed of aluminized steel. - In another embodiment,
reflector 204 may be formed of multiple (e.g., two) sheets of metal.FIG. 3B is a disassembled, cross-sectional drawing ofreflector 204 formed from two sheets of metal. InFIG. 3B ,reflector 204 comprises a first sheet 302-1 and a second sheet 302-2.Reflector 204 may include more or fewer portions than shown. First and second sheets 302-1 and 302-2 may be rolled, drawn, or pressed into the shapes shown. Sheets 302-1 and 302-2 may allow for a compact, disassembledreflector 204 for easier transportation ofradiant heater 200. - First sheet 302-1 may include first lip 304-1 and a first flange 306-1 that may run along
junction 220. Flange 306-1 may provide rigidity along the length of sheet 302-1 and may overlap with a portion of second sheet 302-2 to allow first and second sheets 302-1 and 302-2 to be joined together by, for example, bolts along the length of such an overlap. Second sheet 302-2 may include second lip 304-2 and a second flange 306-2. Flange 306-2 may also overlap with a portion of first sheet 302-1 to allow first and second sheets 302-1 and 302-2 to be joined together by, for example, bolts along the length of such an overlap. - In one embodiment, a joining
strip 310 may overlap with first sheet 302-1 and second sheet 302-2 along their lengths. Joiningstrip 310 may allow first and second sheets 302-1 and 302-2 to be joined together by, for example, bolts along the length of the overlap between joiningstrip 310 and first sheet 302-1 and bolts along the length of the overlap between joiningstrip 310 and second sheet 302-2. In an embodiment with joiningstrip 310, for example, flanges 306-1 and 306-2 may be omitted. - In one embodiment, joining
strip 310 is short compared to the length ofreflector 204. In this embodiment, multiple joining strips may be used along the length ofreflector 204. For example, a joiningstrip 310 may be used at each end ofreflector 204 and a joiningstrip 310 may be used in the middle ofreflector 204. - In test results, reflector 104 (in the configuration of
FIG. 1A ) was compared to reflector 204 (in the configuration ofFIG. 2A ). In these test results, reflector 204 (1) increased maximum radiation measured under the radiant heater by 12%; (2) increased global radiation by 1.2%; (3) decreased convective heat from 234° C. to 175° C., (4) lowered the highest temperature (measured on top of emitting tube 102) by 11%, and (5) increased combustion efficiency of the power plant by 0.6%. In the above test results, global radiation was determined by taking the average of the measured radiation impinging on a surface beneath emittingtubes 102 or 202 (e.g., a surface 3 m by 1 m oriented along emittingtubes tubes reflector 204 orreflector 104. Tests also showed that, in one embodiment,reflector 204 may allow lower temperatures of emittingtube 202 while still increasing radiation and improving combustion parameters. -
FIG. 4A is a cross-sectional drawing of one embodiment of an exemplaryradiant heater 400 with aheat converter hood 402. As described below,converter hood 402 converts and directs heat energy.Radiant heater 400, likeradiant heater 200, includes emittingtube 202 andreflector 204.Converter hood 402 is placed abovereflector 204 to form aspace 404 betweenreflector 204 andconverter hood 402.FIG. 4B is a perspective drawing ofradiant heater 400 showing an exemplary positioning ofconverter hood 402 with respect toreflector 204. The distance fromjunction 220 of reflector toconverter hood 402 may range, for example, from 40 to 35 mm, 35 to 30 mm, 30 to 25 mm, 25 to 20 mm, 20 to 15 mm, 15 to 10 mm, 10 to 5 mm, or less than 5 mm. In one embodiment, the distance fromjunction 220 ofreflector 204 toconverter hood 402 is approximately 24 mm. - Emitting
tube 202 becomes hot as a result of hot gasses passing through emittingtube 202. In addition to emitting thermal radiation, emittingtube 202 heats the air inspace 206 surrounding emitting tube 202 (e.g., through contact of the air with emittingtube 202, or conduction). Heat may also transfer through the air inspace 206 as well as the air inspace 404 betweenreflector 204 and converter hood 402 (e.g., through convection).Reflector 204 may also conduct heat fromspace 206 tospace 404. Hot air inspace 404 is depicted inFIG. 4A as amorphous shapes. - Heat may build up in
space 404 betweenreflector 204 andconverter hood 402, and particularly at the surface ofconverter hood 402 by the convection of the air inspace 404. As a result,converter hood 402 may capture this heat energy (e.g., become hot itself) and may begin to radiate energy. In other words,converter hood 402 may convert the heat energy transferred through convection to the surface ofconverter hood 402 into heat energy radiated through space. As shown inFIG. 4A ,converter hood 402 radiates heat waves 406 (also referred to asradiation 406, depicted as solid lines in the direction of the travel of the wave).Radiation 406 is in addition to reflectedradiation 212 and emittedradiation 210. -
Converter hood 402 may include corrugated portions to capture heat more effectively and to help distribute the heat energy throughoutspace 404. Capturing and converting heat energy around emittingtube 202, byconverter hood 402, allows emittingtube 202 to operate at lower temperatures.Operating emitting tube 202 at lower temperatures may extend the life of emittingtube 202, or may allow more hot fluid to pass through emittingtube 202 without reaching its maximum rated temperatures. -
FIG. 5A is a perspective drawing ofconverter hood 402.FIG. 5B is a cross-sectional drawing ofconverter hood 402.Converter hood 402 may include angled orcorrugated portions 508 along the sides and aflat portion 510 along the middle ofconverter hood 402.Converter hood 402 may be formed from a single piece of sheet metal from one end (e.g., a first flange 506-1) to the other end (e.g., a second flange 506-2).Converter hood 402 may be rolled, drawn, or pressed into the shape. -
Corrugated portions 508 may increase the surface area ofconverter hood 402, allowing it to absorb more heat and convert more energy into radiated heat. In one embodiment,corrugated portions 508 include angles (e.g., angle 520) between 35 to 50° (e.g., 35 to 40°, 40 to 45°, 45 to 50°), 50 to 60°, or 60 to 70°, or 25 to 35°.Corrugated portions 508 may include angles greater than 70° or less than 25°, for example. In one embodiment,corrugated portions 508 include 45° angles, increasing the area ofconverter hood 402 by a factor of 1.414.Corrugated portions 508 may also trap hot air and allow heat to be more evenly distributed alongconverter hood 402 than if, for example,converter hood 402 were not corrugated at all, which may result in more hot air accumulating at the top portion ofconverter hood 402. In another embodiment, corrugated portions may include curves rather than angles. -
Flat portion 510 lacks corrugations, which may also help prevent hot air from accumulating at the top portion ofconverter hood 402. Likecorrugated portions 508,flat portion 510 may allow heat to be more evenly distributed alongconverter hood 402 than if, for example, the top portion were corrugated. -
FIG. 5C is a disassembled, cross-sectional drawing ofexemplary converter hood 402. In this embodiment,converter hood 402 may include a first side portion 502-1, a second side portion 502-2, a first top potion 504-1, and a second top potion 504-2.Converter hood 402 may include more or fewer portions than shown. Portions 502-1, 502-2, 504-1, and 504-2 may allow for a more compact, disassembledconverter hood 402 for easier transportation ofradiant heater 400. Portions 502-1, 502-2, 504-1, and 504-2 may be rolled, drawn, or pressed into the shapes shown. - First side portion 502-1 may include
corrugated portion 508 and first flange 506-1. First flange 506-1 may provide for rigidity along the length ofconverter hood 402. First flange 506-1 may also hold an insulation layer (not shown, discussed below) in place.Corrugated portion 508 may also provide for rigidity along the length ofconverter hood 402 in addition to the features discussed above. Second side portion 502-2 may includecorrugated portion 508 and second flange 506-2, which may provide the same features as the corresponding elements of first side portion 502-1. - First top portion 504-1 may include
corrugated portion 508 andflat portion 510. Likewise, second top portion 504-2 may includecorrugated portion 508 andflat portion 510. Part of first top portion 504-1 may overlap with first side portion 502-1, allowing first top portion and first side portion 506-1 to be bolted together. Likewise, part of second top portion 504-2 may overlap with second side portion 502-2, allowing second top portion 504-2 and second side portion 502-2 to be bolted together. Part of first top portion 504-1 may also overlap with part of second top portion 504-2, allowing first top portion 504-1 and second top portion 504-2 to be bolted together. - Test results have shown that (1) the radiant heat intensity under
radiant heater 400 is approximately 20% higher compared toradiant heater 100, (2) the radiant heat intensity underradiant heater 400 is approximately 12% higher compared toradiant heater 200, without an increase in the temperature of emittingtube 202, and (3) the heat input into emittingtube 202 ofradiant heater 400 may be increased by 20% (as compared to radiant heater 100) before reaching the maximum rated temperature of emittingtube 202. - By increasing the heat input 20%, test results have shown that radiant heat intensity under
radiant heater 400 is increased 50% (compared toradiant heater 100 at the same temperature of emitting tube 202). Keeping the same maximum-rated temperature on emittingtube 102 and emitting tube 202 (in radiant heater 400), test results showed a gain of 50% in the efficiency withreflector 204 andconverter hood 402.Radiant heater 400 showed a radiant heat efficiency of 81% (net caloric value (NCV)) and a total heat output efficiency of 93% NCV. On the other hand,radiant heater 100 showed a radiant heat efficiency of 54% NCV and a total heat output efficiency of 63% NCV. -
FIG. 6 is a cross-sectional drawing of aradiant heater 600 including aninsulation layer 606.Radiant heater 600, likeradiant heater 200, includes emittingtube 202,reflector 204, andconverter hood 402. In one embodiment, emittingtube 202,space 206,reflector 204,space 404, andconverter hood 402 may become hot.Insulation layer 606 may reside aboveconverter hood 402.Insulation layer 606 may slow heat transfer in the upward direction and reduce heat loss. As a result, in this embodiment,insulation layer 606 may allowconverter hood 402 to reach higher temperatures than withoutlayer 606, allowinghood 402 to reradiate more energy withlayer 606 than withoutlayer 606.Converter hood 402 may holdinsulation layer 606 in place using flanges 506-1 and 506-2 or other mechanical attachment means. -
FIG. 7A is a plot of aninvolute curve 704 of acircle 702, which may be used to define first surface 204-1 and second surface 204-2 ofreflector 204 inradiant heater 200. An involute curve may be obtained by attaching an imaginary, taut string to a first curve and tracing the string's free end as it is wound onto that first curve, thus creating the involute curve. - For example, assume that
circle 702 is the first curve and that line 706-1 is a string 706 attached tocircle 702 at afixed point 708 on one end, and to apencil 712 on the other end.Circle 702 may represent an emitting tube, such as emittingtube 202. In this example, the length of string 706 is the same as the circumference ofcircle 702. As string 706 is moved in adirection 710, string 706 becomes wound aroundcircle 702 andpencil 712 tracesinvolute curve 704. String 706 is shown in many positions (706-1, 706-2, etc.) as string 706 is wound aroundcircle 702. Upon one complete revolution of string 706 aroundcircle 702,involute curve 704 intersectscircle 702 atpoint 708 because the length of string 706 is the same as the circumference ofcircle 702.Involute curve 704 may also be described as the unwinding of string 706 fromcircle 702. - One property of
involute curve 704 is that tangents ofcircle 702 are perpendicular toinvolute curve 704. Because lines 706-1 through 706-11 are tangent tocircle 702, lines 706-1 through lines 706-11 are all perpendicular toinvolute curve 704.FIG. 7B demonstrates another property ofinvolute curve 704. For simplicity,FIG. 7B showscircle 702,involute curve 704, and tangent line 706-7 ofFIG. 7A . InFIG. 7B , a line is drawn from the center ofcircle 702 to the intersection ofinvolute curve 704 with tangent line 706-7. Because tangent line 706-7 is perpendicular toinvolute curve 704, an angle A betweenline 710 and involute curve is less than 90°, e.g., angle A is I degrees less than 90°. Ifline 710 were a heat wave, such as one ofheat waves 210, then, according to Snell's Law, the angle of reflection is equal to the angle of incidence. Thus, a reflectedwave 712 is R degrees (R equal to I) below tangent line 706-7. Being below tangent line 706-7 means that reflectedwave 712 clears circle 702 (e.g., emitting tube 202). As shown,involute curve 704 may vary in distance to tangents of circle 702 (e.g., emitting tube 202), but the distance, in one embodiment, may not exceed one half of the circumference - The relationship shown in
FIG. 7B may apply to all lines (e.g., emitted waves 210) from the center of circle 702 (e.g., emitting tube 202). Thus, as shown inFIG. 7C , an emittedwave 710′ is reflected away fromcircle 702 as reflectedwave 712′. -
FIG. 7D shows anotherinvolute curve 704′, which is symmetrical toinvolute curve 704 along acenter line 720.FIG. 7E showsinvolute curve 704 andinvolute curve 704′ superimposed on each other. Finally,FIG. 7F shows only a portion of the superimposedinvolute curves reflector 204 discussed above with respect toFIG. 2B . As discussed above, heat waves emitted from emitting tube 202 (e.g., circle 702) are reflected down and away from emittingtube 202. In addition, emittingtube 202 is spaced apart fromreflector 204. 204 may also be referred to as a “bi-involute” reflector. - The spacing between emitting
tube 202 andreflector 204 may be the result of fixedpoint 708 not being directly above the center ofcircle 702. For example, inFIGS. 7A through 7F ,fixed point 708 is approximately 29° away from being directly above the center ofcircle 702. Other angles are possible, such as an angle between approximately 0-5°, 5-10°, 10-15°, 15-20°, 20-25°, 25-30°, 30-35°, etc. (e.g., 5n to 5n+5, where n is zero or a positive integer). Angles above 360° are also possible.Curves circle 702 with a diameter of approximately 76.1 mm. Other diameters are possible, such as between 5-10 mm, 10-20 mm, 20-30 mm, 30-40 mm, 40-50 mm, 50-60 mm, 60-70 mm, 70-80 mm, 80-90 mm, etc. (e.g., 10u to 10u+10 mm, where u is a positive integer). - As shown in
FIG. 7F , the surfaces ofreflector 204 may end a distance H above the bottom of emittingtube 202. In one embodiment, H is chosen such thatdirect heat waves 210 disperse as widely as possible, but do not impinge onconverter hood 402. In other words, H may be (1) large enough such that a straight line from line source P to the space just below the bottom edge ofconverter hood 402 is unobstructed byreflector 204; and (2) small enough such that a straight line from line source P to the space just above the bottom edge ofconverter hood 402 is obstructed byreflector 204. In this embodiment,direct heat waves 210 are dispersed as widely as possible, andheat waves 210 that would otherwise impinge onconverter hood 402 are reflected. This embodiment also allows for more radiated heat waves 406 (emitted by converter hood 402) to reachfloor 208 without impinging on converter hood 402 (as compared, for example, to H being zero or extending below the edge of converter hood 402). - As discussed above, these properties of
reflector 204 may increase the heating efficiency ofradiant heater 200 andradiant heater 400. These properties may also allow the temperature of emittingtube 202 to be lower than in conventional systems (as compared to emittingtube 102, for example). -
FIG. 8A is a diagram of an alternativeinvolute curve 804 aroundcircle 702.Involute curve 804 begins atfixed point 808, which is directly above the center ofcircle 702, unlike fixedpoint 708 which is not directly above the center ofcircle 702.FIG. 8B shows anotherinvolute curve 804′, which is symmetrical toinvolute curve 804 along acenter line 820.FIG. 8C showsinvolute curve 804 andinvolute curve 804′ superimposed on each other. Finally,FIG. 8D shows only a portion of the superimposedinvolute curves reflector 204′), the portion shown having the characteristics similar toreflector 204 discussed above with respect toFIG. 2B . As discussed above, heat waves emitted from emitting tube 202 (e.g., circle 702) are reflected byreflector 204′ down and away from emittingtube 202. In the design ofreflector 204′, however, the distance between emittingtube 202 andreflector 204′ is less than withreflector 204. Withreflector 204′, however, an emitter tube may be used that has a smaller radius than emittingtube 202. In this case, the smaller emitter tube may be spaced farther fromreflector 204′, but may still have the same center ascircle 702. - As discussed above,
reflector 204/204′ allows for more reflected energy to pass around emittingtube 202. The shape ofreflector 204/204′ may help reduce heat buildup under the reflector. Reducing heat underreflector 204/204′ may result in lower temperatures on the hottest points of emittingtube 202. Thus,reflector 204/204′ may increase the reflection efficiency and may increase the radiant efficiency of a heater. This greater efficiency may increase the reliability of the heater and the lifetime of the heater, as component temperature (e.g., the temperature of emitting tube 202) may be reduced. Becausereflector 204/204′ may reduce temperatures, relative toreflector 104,reflector 204/204′ may allow an increased heat input to achieve the same reliability asreflector 104. - Returning to
FIG. 2B ,junction 220 is directly above emittingtube 202. A central axis (not shown) passes through source point P (the center of emitting tube 202) andjunction 220. Surface 204-1 is such that radiation impinging onreflector 204 closer to junction 220 (and the central axis) is reflected (in its first reflection) farther away from the central axis than radiation impinging onreflector 204 farther away fromjunction 220. In other words, the reflected radiation creates the cross pattern shown inFIG. 2B . “Farther away,” in this example means that the reflected energy (in the direction of its first reflection that does not cross the central axis) impingesfloor 208 farther away from the central axis. - In addition, as shown in
FIG. 2B , radiation is distributed acrossfloor 208. In one embodiment, first surface 204-1 provides for a substantially even distribution of the reflected radiated energy—including areas directly under emittingtube 202 as well as outside the umbrella ofreflector 204. - Embodiments described herein may allow for (1) higher heat output and/or higher radiant heat intensity, given the same input, for a radiant heater as compared to a conventional heater; (2) reduction of heat loss through roofs and walls; (3) lower and more even air temperatures in a heated area; (4) less thermal loss (e.g., through convection given higher radiant heat downward); (5) faster response and stabilization (e.g., resulting from increased radiant efficiency); and (6) reduced energy consumption (e.g., less fuel spent to heat fluids passing through emitting tubes) and lower carbon dioxide emissions.
- As discussed above, in one embodiment,
reflector 204 comprises a first sheet 302-1 and a second sheet 302-2 joined by multiple joiningstrips 310. In this exemplary embodiment, first sheet 302-1 and second sheet 302-2 do not include flange 306-1 and flange 306-2. Instead, an air gap may separate first sheet 302-1 and second sheet 302-2 (e.g., at junction 220), where the air gap is interrupted by joiningstrips 310. In this embodiment, heat transfer may occur through convection by air passing fromspace 206 tospace 404 through the air gap between first and second sheets 302-1 and 302-2. In this embodiment, reflected radiation may not be reduced significantly because it is atjunction 220 where radiation may otherwise reflect downward toward emittingtube 202.Converter hood 402 may include an angle immediately abovejunction 220 to reflect any radiation away from emittingtube 202. Alternatively,converter hood 402 may include a material directly abovejunction 220 to absorb the energy emitted by emittingtube 202 so that captured energy may be re-radiated fromconverter hood 402. Air gaps or holes may also be placed in other locations onreflector 204, such as periodically at the highest points ofreflector 204 along its length. - In another embodiment,
reflector 204 and/or emittingtube 202 may be suspended fromconverter hood 402 by a suspension mechanism (e.g., cables or long bolts). In this embodiment, heat may be transferred by conduction of heat along the suspension mechanism directly fromreflector 204/space 204 toconverter hood 402. In another embodiment,reflector 204 and/or emittingtube 202 may be connected toconverter hood 402 through a metal conductor (other than a suspension mechanism) to transfer heat by conduction fromreflector 204 and/or emittingtube 202 toconverter hood 402. - In one embodiment,
reflector 204 may be approximately 300 mm wide from edge to edge and 100 mm tall. In one embodiment,converter hood 402 may be approximately 700 mm wide from edge to edge and 170 mm tall. - The foregoing description of exemplary embodiments provides illustration and description, but is not intended to be exhaustive or to limit the embodiments described herein to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the embodiments.
- For example,
reflector 204 may be used in a radiant heater without the use orconverter hood 402. In this example, an insulation layer (not shown) may be laid abovereflector 204 to slow the heat transfer upward to reduce heat loss. Is another example,converter hood 402 may be used with reflectors of any shape, includingreflector 104 ofradiant heater 100. As another example, a curved surface other than a circle (e.g., an ellipse) may be used to create the involute shape ofreflector 204, even though emittingtube 202 is still a circle. In this example, emittingtube 202 may still be within the radiation-free envelope created by the involute curved surface. Further, shapes that approximate or are substantially similar to the shape ofreflector 204 andreflector 204′ are possible. - As another example, first lip 304-1 and second lip 304-2 of
reflector 204 may include another bend inward toward first sheet 302-1 and second sheet 302-2, respectively. In this embodiment,radiation 406 emitted byconverter hood 402 may reflect away fromreflector 204 rather than being trapped in the area formed by lips 304 and sheets 302. - As yet another example, in one embodiment,
reflector 204 andconverter hood 402 may both be mounted on the same support structure such that the spatial relationship between the two remains the same. In another embodiment,reflector 204,converter hood 402, and emittingtube 202 may be mounted on the same support structure such that the spatial relationship between the three remains the same. In another embodiment, emittingtube 202 andreflector 204 may be mounted on the same support structure so that the spatial relationship between the two remains the same. In this embodiment,reflector 204,converter hood 402, and/or emittingtube 202 may be sold, packaged, and shipped in a manner convenient for installation. In oneembodiment reflector 204 andconverter hood 402 may be integrally formed. - Although the invention has been described in detail above, it is expressly understood that it will be apparent to persons skilled in the relevant art that the invention may be modified without departing from the spirit of the invention. Various changes of form, design, or arrangement may be made to the invention without departing from the spirit and scope of the invention. Therefore, the above mentioned description is to be considered exemplary, rather than limiting, and the true scope of the invention is that defined in the following claims.
- No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
Claims (22)
1. A system comprising:
a tube through which hot fluid is transported, wherein the tube radiates heat energy and transfers heat energy to surrounding air; and
a reflector positioned on a first side of the tube to reflect the radiated heat in a direction outward of the tube, the reflector having a first curved surface and a second curved surface that meet at a junction, the tube spaced from the junction by a distance that is between 30% and 77% of a radius of the tube.
2. The system of claim 1 , wherein the first curved surface is configured as a portion of an involute curve and the reflector and tube are configured such that a plurality of lines tangent to an edge of the tube are perpendicular to the involute curve upon intersection.
3. The system of claim 2 , wherein second lines intersecting a center of the tube and the involute curve create an acute angle between the involute curve and each of the second lines.
4. The system of claim 2 , wherein each plurality of lines tangent to the edge of the tube vary in distance from the involute curve.
5. The system of claim 4 , wherein a longest of the plurality of lines tangent to the edge of the tube does not exceed one half of a circumference of the tube.
6. The system of claim 1 , wherein the first curved surface is configured as a portion of an involute curve, and wherein the involute curve is configured to intersect an edge of the tube at a point that is away from being directly above a center of the tube.
7. The system of claim 6 , wherein the point intersects the edge at an angle of 29° away from being directly above the center of the tube.
8. The system of claim 6 , wherein the point intersects the edge at an angle of between 5° and 35° away from being directly above the center of the tube.
9. The system of claim 6 , wherein the point intersects the edge at an angle of greater than 360° away from being directly above the center of the tube.
10. The system of claim 1 , wherein the first curved surface is configured as a portion of an involute curve, and wherein the involute curve is configured to intersect an edge of the tube at a point that is directly above a center of the tube.
11. The system of claim 1 wherein the first and second curved surfaces end above a bottom of the tube.
12. The system of claim 1 , further comprising a hood spaced from the reflector and configured to radiate a portion of the captured heat energy in generally the same direction as the reflected radiant heat.
13. The system of claim 12 , wherein the hood includes corrugations.
14. An apparatus, comprising:
a tube through which hot fluid is transported, wherein the tube radiates heat energy and transfers heat energy to surrounding air; and
a reflector positioned on a first side of the tube to reflect the radiated heat in a direction outward of the tube, the reflector having a first curved surface and a second curved surface that meet at a junction, at least one of the first curved surface and the second curved surface configured as a portion of an involute curve, and wherein the involute curve is configured to intersect an edge of the tube at a point that is away from being directly above a center of the tube.
15. The apparatus of claim 14 , wherein the tube is spaced from the junction by a distance that is between 30% and 77% of a radius of the tube.
16. The apparatus of claim 14 , wherein the point intersects the edge at an angle of between 5° and 35° away from being directly above the center of the tube.
17. The apparatus of claim 14 , wherein the point intersects the edge at an angle of greater than 360° away from being directly above the center of the tube.
18. The hood of claim 14 , further comprising a hood spaced from the reflector and configured to radiate a portion of the captured heat energy in generally the same direction as the reflected radiant heat.
19. The system of claim 18 , wherein the hood includes corrugations.
20. A system comprising:
a tube through which hot fluid is transported, wherein the tube radiates heat energy and transfers heat energy to surrounding air; and
a reflector positioned on a first side of the tube to reflect the radiated heat in a direction outward of the tube, the reflector having a first curved surface and a second curved surface that meet at a junction, at least one of the first curved surface and the second curved surface configured as a portion of an involute curve and the reflector and tube are configured such that a plurality of lines tangent to an edge of the tube are perpendicular to the involute curve upon intersection;
wherein a longest of the plurality of lines tangent to the edge of the tube does not exceed one half of a circumference of the tube.
21. The system of claim 20 , wherein the tube is spaced from the junction by a distance that is between 30% and 77% of a radius of the tube.
22. The system of claim 20 , wherein the involute curve is configured to intersect an edge of the tube at a point that is away from being directly above a center of the tube.
Priority Applications (1)
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US14/680,441 US20150211752A1 (en) | 2009-08-27 | 2015-04-07 | Radiant heat reflector and heat converter |
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US23737609P | 2009-08-27 | 2009-08-27 | |
US12/563,428 US9022298B2 (en) | 2009-08-27 | 2009-09-21 | Radiant heat reflector and heat converter |
US14/680,441 US20150211752A1 (en) | 2009-08-27 | 2015-04-07 | Radiant heat reflector and heat converter |
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US12/563,428 Continuation US9022298B2 (en) | 2009-08-27 | 2009-09-21 | Radiant heat reflector and heat converter |
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US20150211752A1 true US20150211752A1 (en) | 2015-07-30 |
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US14/680,441 Abandoned US20150211752A1 (en) | 2009-08-27 | 2015-04-07 | Radiant heat reflector and heat converter |
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US12/563,428 Expired - Fee Related US9022298B2 (en) | 2009-08-27 | 2009-09-21 | Radiant heat reflector and heat converter |
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CN106610051A (en) * | 2016-12-28 | 2017-05-03 | 美的集团股份有限公司 | Reflecting cover, heating device and warmer |
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US9080777B2 (en) * | 2012-01-31 | 2015-07-14 | Schwank, Ltd. | Reflector for radiant tube heater |
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Also Published As
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US9022298B2 (en) | 2015-05-05 |
EP2290294A1 (en) | 2011-03-02 |
EP2290294B1 (en) | 2018-10-24 |
US20110049253A1 (en) | 2011-03-03 |
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