BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein:
FIG. 1 is a cross-sectional lateral view of a self-recuperating, flat radiant panel heater in accordance with one embodiment of this invention;
FIG. 2 is a view of a portion of the self-recuperating flat radiant panel heater shown in FIG. 1 along the line II-II;
FIG. 3 is a cross-sectional lateral view of a self-recuperating, flat radiant panel heater in accordance with one embodiment of this invention; and
FIG. 4 is a lateral, partial cross-sectional view of a flat radiant panel heater in accordance with one embodiment of this invention disposed within a heating chamber wall opening.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The flat radiant panel heater 10, in accordance with one preferred embodiment of this invention as shown in FIG. 1, comprises a housing having a back wall 13, an opposed heat radiating wall or panel 11, and at least one side wall 12 connecting the back wall 13 with the heat radiating wall 11. Disposed within the housing is a cone-shaped combustion chamber wall 18, forming a cone-shaped combustion chamber 16. An exhaust gas plenum wall 19 is disposed between combustion chamber wall 18 and back wall 13, forming oxidant plenum 20 between exhaust gas plenum wall 19 and back wall 13 and forming exhaust gas plenum 17 between exhaust gas plenum wall 19 and combustion chamber wall 18. Nozzle mix burner nozzle 24 having a fuel inlet 25, an oxidant inlet 26 and a fuel/oxidant mixture outlet 32, in which fuel and primary oxidant are mixed prior to being introduced into combustion chamber 16, extends through nozzle opening 23 formed by back wall 13 into the housing and through exhaust gas plenum wall 19 and combustion chamber wall 18 terminating in the apex portion 30 of combustion chamber 16. Oxidant supply conduit 33 having oxidant supply inlet 34 and oxidant supply outlet 35 is shown extending through opening 14 of back wall 13, providing fluid communication between the exterior of the housing and oxidant plenum 20. By virtue of this arrangement, oxidant that is introduced through oxidant supply conduit 33 into oxidant plenum 20 is heated by transfer of heat from exhaust gases disposed within exhaust gas plenum 17 through exhaust gas plenum wall 19 prior to being introduced into nozzle mix burner nozzle 24.
In accordance with one preferred embodiment of this invention, radiant panel heater 10 further comprises oxidant permeable distributor wall 22 disposed within oxidant plenum 20 at a distance from exhaust gas plenum wall 19, forming primary oxidant plenum 21 there between. Oxidant permeable distributor wall 22 forms primary combustion oxidant outlet 28 in fluid communication with primary combustion oxidant conduit 27 through which primary combustion oxidant is provided to nozzle mix burner nozzle 24.
In accordance with one preferred embodiment of this invention, nozzle mix burner nozzle 24 comprises a reducing diameter pipe section 36 into which the first stage of oxidant, preferably in the range of about 50% to about 99% of the stoichiometric requirement for complete combustion of the fuel, is introduced. The reducing diameter pipe accelerates the oxidant flow and helps to establish the desired flame pattern. Located coaxially within the reducing diameter pipe section 36 is a fuel nozzle 38 through which a gaseous or liquid fuel is injected into the nozzle mix burner nozzle 24. As shown in FIG. 1, the fuel outlet end 37 of fuel nozzle 38 is disposed upstream of the fuel/oxidant mixture outlet 32 of nozzle mix burner nozzle 24. By virtue of this arrangement, the fuel is injected into the primary combustion oxidant stream flowing around fuel nozzle 38. When ignited, the fuel/oxidant mixture burns in a thin sheet of an oxygen-deficient flame, which is attached to the at least one combustion chamber wall 18. The oxygen-deficient conditions minimize NOx formation by reducing the availability of oxygen for NOx formation as well as the flame temperature. The reduced flame temperature, together with the longer flame resulting from the deficiency of oxygen, increase the temperature uniformity of flat radiant panel 11, which, in turn, increases its life as well as the quality of the material being heated.
As shown in FIG. 1, exhaust gas plenum 17 is disposed around the periphery of conical combustion chamber 16 adjacent to combustion chamber wall 18. Exhaust gas plenum 17 is provided with exhaust gas inlets 29 through which the partial combustion products formed by the oxidant-deficient combustion of the fuel/oxidant mixture in conical combustion chamber 16 are passed into exhaust gas plenum 17 as indicated by arrows 40, 41. Exhaust gas conduit 15, shown in FIG. 1 extending through an opening formed by back wall 13, comprises exhaust gas inlet end 42 which is in fluid communication with exhaust gas plenum 17 and exhaust gas outlet end 43, whereby exhaust gases generated by the combustion process are exhausted from the radiant panel heater 10. Exhaust gas plenum 17 further comprises at least one secondary combustion oxidant opening 44 through which secondary combustion oxidant is introduced into exhaust gas plenum 17. In exhaust gas plenum 17, the secondary combustion oxidant mixes with the partial combustion products exhausted from combustion chamber 16 to form a secondary combustion zone in exhaust gas plenum 17 in which combustion of the combustibles remaining in the partial combustion products is completed. Secondary combustion oxidant represents in the range of about 50% to about 1% of the stoichiometric requirement for complete combustion of the total amount of fuel introduced into conical combustion chamber 16. In accordance with one preferred embodiment of this invention, secondary combustion oxidant opening 44 is disposed proximate the base portion of the conical combustion chamber 16 formed by the at least one combustion chamber wall 18. Because a significant amount of heat from the primary combustion zone is removed through flat radiant panel 11, the secondary combustion oxidant temperature is lowered, as a result of which secondary NOx formation is also reduced. To reduce heat loss through back wall 13, insulating layer 31 is provided on the combustion chamber facing surface of back wall 13.
In accordance with one embodiment of this invention, swirling means for imparting a swirl to the preheated primary combustion oxidant, such as swirler 50 shown in FIG. 2, are disposed within primary combustion oxidant conduit 27. Primary oxidant conduit 27 includes a primary oxidant inlet 28 in fluid communication with oxidant plenum 20 and primary oxidant outlet 26 in fluid communication with nozzle mix burner nozzle 24.
A flat radiant panel heater 110 in accordance with another embodiment of this invention, as shown in FIG. 3, comprises a back wall 113, a heat radiating panel or wall 111 disposed substantially parallel to and spaced apart from the back wall 113, and at least one side wall 112 connected with the back wall 113 and extending to contact the heat radiating wall 111. Disposed between back wall 113 and heat radiating wall 111 is a combustion chamber wall 118, whereby combustion chamber 116 is formed between heat radiating wall 111 and combustion chamber wall 118. Exhaust gas plenum wall 119 is disposed between back wall 113 and combustion chamber wall 118, forming exhaust gas plenum 117 between exhaust gas plenum wall 119 and combustion chamber wall 118. Oxidant plenum wall 120 is disposed between back wall 113 and exhaust gas plenum wall 119, forming a primary oxidant plenum 121 there between. Back wall 113 forms a fuel inlet 123, an oxidant inlet 114 and an exhaust gas outlet 115 through which fuel is introduced into combustion chamber 116, oxidant is introduced into primary oxidant plenum 121, and exhaust gas disposed in exhaust gas plenum 117 is exhausted, respectively. To provide the functionality described in more detail herein below, the radiant panel heater in accordance with one embodiment of this invention further comprises fluid communication means for providing fluid communication between the combustion chamber 116 and the exhaust gas plenum 117, between the primary oxidant plenum 121 and the combustion chamber 116, between the fuel inlet 123 and the combustion chamber 116, between the exhaust gas plenum 117 and the exhaust gas outlet 115, and between the primary oxidant plenum 121 and the oxidant inlet 114. In accordance with one embodiment of this invention, fluid communication between primary oxidant plenum 121 and combustion chamber 116 comprises a plurality of oxidant conduits 129 extending between primary oxidant plenum 121 and combustion chamber 116.
In accordance with one embodiment of this invention, radiant panel heater 110 comprises premixing means for premixing a first portion of an oxidant (primary combustion oxidant) with a fuel for introduction into combustion chamber 116. In accordance with one preferred embodiment of this invention, radiant panel heater 110 further comprises a perforated plate 122 disposed within primary oxidant plenum 121 substantially parallel to and spaced apart from oxidant plenum wall 120 and exhaust gas plenum wall 119. In addition to perforations, perforated plate 122 forms a primary combustion oxidant outlet 128, which is in fluid communication with the premixing means, whereby the portion of oxidant to be premixed with the fuel is provided to the premixing means. Premixing means in accordance with one embodiment of this invention as shown in FIG. 3 comprises nozzle mix burner 124 having fuel inlet 125, oxidant inlet 126 and fuel/oxidant mixture outlet 130, the latter being in fluid communication with combustion chamber 116. Primary oxidant is provided to nozzle mix burner 124 through primary combustion oxidant conduit 127, which is in fluid communication with primary combustion oxidant outlet 128.
As previously indicated, one of the improved efficiencies of the radiant panel heater of this invention is provided by preheating of the primary combustion oxidant prior to premixing with the fuel. This preheating is accomplished by the transfer of heat in the hot exhaust gas disposed in exhaust gas plenum 117 through exhaust gas plenum wall 119 into primary oxidant plenum 121.
In accordance with one embodiment of this invention, to further promote the transfer of heat within the radiant panel heater, the radiant panel heater comprises at least one heat transfer enhancement. In accordance with one embodiment of this invention, the heat transfer enhancement comprises a plurality of dimples 142 disposed on at least one of the surfaces of exhaust gas plenum wall 119, the purpose of which is to promote turbulent flow of exhaust gases proximate exhaust gas plenum wall 119 and enhance the transfer of heat from the exhaust gases in exhaust gas plenum 117 to oxidant in primary oxidant plenum 121. Similarly, to promote the transfer of heat from the exhaust gases generated in combustion chamber 116 into the exhaust gases disposed within exhaust gas plenum 117, a plurality of dimples 142 are disposed on at least one surface of combustion chamber wall 118 in accordance with one embodiment of this invention. To promote heat transfer between heat radiating wall 111 and the environment proximate heat radiating wall 111 in accordance with one embodiment of this invention, a plurality of dimples 142 are disposed on at least one surface of heat radiating wall 111.
Profiling the heated (or cooled) wall surfaces of the radiant panel heater, in addition to providing enhancements to the heat transfer between fluids disposed on opposite sides of the wall(s), may be used to enhance wall surface corrosion/erosion resistance and/or provide improvements to hydrodynamic and/or combustion stability within the radiant panel heater.
In accordance with one embodiment of this invention, elements of surface roughness and turbulators, such as pimples, studs, cut fins, winglets, and the like, are disposed on at least one surface of exhaust gas plenum wall 119, combustion chamber wall 118 and/or heat radiating wall 111 for the purpose of heat transfer enhancement, corrosion/erosion resistance and/or hydrodynamic and/or combustion stability improvement. In accordance with yet another embodiment of this invention, one or more surfaces of one or more walls of the radiant panel heater are treated, such as by application of a nano coating, for the purpose of heat transfer enhancement, corrosion/erosion resistance and/or hydrodynamic and/or combustion stability improvement.
In accordance with one embodiment of this invention, radiant panel heater 110 further comprises an insulating layer 131 disposed on a combustion chamber facing surface of back wall 113.
FIG. 4 shows one embodiment of the radiant panel heater disposed within a radiant panel heater opening 141 formed by a heating chamber wall 140. As shown therein, in accordance with one preferred embodiment of this invention, radiating wall 111 is integral with the inside surface 144 of heating chamber wall 140.
The method for producing radiant heat in accordance with one embodiment of this invention comprises introducing a mixture of fuel and primary combustion oxidant into a combustion chamber, which mixture comprises less than a stoichiometric requirement for complete combustion of the fuel, and igniting the mixture, forming heated partial combustion products. Thereafter, at least a portion of heat in the heated partial combustion products is transferred to the heat radiating wall. The heated partial combustion products are passed from the combustion chamber into an exhaust gas plenum disposed adjacent to the combustion chamber. Secondary combustion oxidant is introduced into the exhaust gas plenum in an amount sufficient to complete combustion of the partial combustion products, forming exhaust gases. Heat in the exhaust gases is transferred to the primary combustion oxidant disposed in a combustion oxidant plenum disposed adjacent to the exhaust gas plenum. In accordance with one preferred embodiment of this invention, the secondary combustion oxidant, like the primary combustion oxidant, is preheated, preferably by heat from the hot exhaust gases.
In accordance with one embodiment of this invention, the mixture of fuel and primary combustion oxidant comprises in a range of about 50% to about 99% of the stoichiometric requirement for complete combustion of the fuel and the secondary combustion oxidant comprises in a range of about 50% to about 1% of the stoichiometric requirement for complete combustion of the fuel.
In accordance with one preferred embodiment of this invention, the fuel is a gaseous fuel selected from the group consisting of natural gas, coke oven gas, propane, recycled combustible effluent and mixtures thereof, and the oxidant is selected from the group consisting of oxygen, air and oxygen-enriched air.
While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for the purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of this invention.
Patent Application
20080003531
