Furnaces – Arch or roof structure – Planar surface area
Reexamination Certificate
2000-01-03
2001-06-12
Ferensic, Denise L. (Department: 3749)
Furnaces
Arch or roof structure
Planar surface area
C110S314000, C110S336000, C110S337000, C110S338000, C110S180000, C165S073000, C165S128000, C249S083000
Reexamination Certificate
active
06244197
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to walls, doors, lids, covers and other elements of industrial furnaces and the like that are formed from components subjected to high heat during use that are provided with chimney-like internal passages through which flows of ambient air are induced to circulate without being blown, pressurized or otherwise forced to flow, to perform a cooling function. Stated in another way, the present invention relates to methods and means for providing cooling flows of ambient air that self establish through interior regions of heated components of industrial furnaces and the like, by providing elongate chimney-like passages that extend internally through the heated components, with the passages defining inlets and outlets near opposite end regions thereof that communicate with a body of ambient air, and with the outlet of each passage being located higher than the inlet so that ambient air 1) may enter the inlet, 2) may become heated and rise in the chimney-like passage as the ambient air is exposed to the hot interior of at least one of the heated components, and 3) may discharge through the outlet so as to carry heat energy away from the interior of at least one of the heated components. The outlet end regions of the passages may be of greater cross-sectional area than the inlet end regions to encourage ambient air that becomes heated and expands within the chimney-like passages to discharge from outlets that are less restrictive than the inlets. If the passages are defined by conduits made from high heat resistant metal such as stainless steel, and if the conduits have central regions that are embedded within furnace components formed from cast refractory material, conduit end regions that project from the cast refractory components may be connected to a supporting framework, by which arrangement the conduits serve not only to cool the cast refractory components but also to mount the cast refractory components on the framework.
2. Prior Art
Industrial furnaces are well known that employ wall, door, lid and cover components that will provide improved service longevity if they are cooled during use to minimize the detrimental effects of a high heat environment. While efforts have been made to provide such components with coolant tubes through which flows of coolant (such as water or refrigerant) may be circulated by means of pumps, blowers, compressors and the like, these forced flow coolant systems have many drawbacks including complexity, high cost, and the need for active programs of maintenance to ensure that coolant circulates properly at times when the components are subjected to high heat.
Many components that are subjected to high heat (such as components that are used in forming walls, doors, lids and covers of industrial furnaces and the like) can be formed advantageously from castable refractory material. Normally castable refractory furnace components are held in place with the aid of metallic anchors that are positioned and oriented to favor (i.e., positioned near and/or extending toward) the cold face of the refractory components to ensure that the anchors remain as cool as possible. While these metallic anchors often are formed from stainless steel (to provide reasonably priced anchors that will offer relatively good resistance to high heat), the failure of these anchors in refractory systems that are exposed to high heat temperatures as high as 2800 to 3100 degrees Fahrenheit is quite common.
The complex nature of forced coolant flow systems that employ fans, pumps, blowers, or compressors together with coolant reservoirs and interconnecting coolant supply lines renders the use of forced flows of circulating coolant impractical and unworkable with many types of industrial furnace components. Thus, a long-standing need has existed for a much simpler method and means for cooling heated components of industrial furnaces and the like to lengthen the service life of these furnace components by permitting these components (and metallic elements that are embedded within many of these components) to operate at cooler temperatures.
The applicant, Gary L. Coble, is the named inventor in several patents that feature related subject matter. While many patents disclose industrial furnace components of a type that would benefit from the provision of a simple cooling method and means, U.S. Pat. Nos. 5,335,897 and 5,483,548 issued to Gary L. Coble provide good examples thereof, hence the disclosures of these patents are incorporated herein by reference. The manner in which cast refractory components are made and put to use in the bases of annealing furnaces is disclosed in U.S. Pat. Nos. 5,562,879, 5,575,970, 5,578,264, 5,681,525 and 5,756,043 issued to Gary L. Coble, and the disclosures of these patents also are incorporated herein by reference.
SUMMARY OF THE INVENTION
In accordance with the preferred practice of the present invention, chimney-like passages are used to duct flows of ambient air through interior regions of heated components of industrial furnaces and the like to cool the components, typically to improve service longevity of the components and of metal structures that may be embedded within these components. The passages are oriented and configured so that cooling flows of ambient air self establish within the passages once the furnace components are heated to temperatures significantly higher than ambient air temperatures, without a need employ fans, pumps, blowers, compressors or other complex paraphernalia characteristically found in forced flow coolant systems.
In accordance with one form of preferred practice, a component of an industrial furnace or the like is cooled 1) by providing at least one passage through a selected interior region of the component, namely a elongate passage that extends continuously between spaced openings located near opposite ends of the passage, and 2) by positioning the component so that, when the component becomes heated during normal service (due, for example, to operation of the furnace or the like), the spaced openings communicate with a body of ambient air, with at least one of the openings defining an inlet that is located below at least another one of the openings which defines an outlet, so that ambient air may enter the inlet, may become heated and rise within the passage (just as heated expanding gas rises in a chimney), and may discharge from the outlet to thereby establish a flow of ambient air through the passage to cool the component.
If a passage is provided with more than one inlet or more than one outlet, all of the outlets should be located above the highest one of the inlets to ensure that heated ambient air enters the passage through the inlet(s) and discharges through the outlet(s).
While, in most installations, it is preferred that the cross-sectional area of the outlet of a passage not be less than the cross-sectional area of the inlet of the passage, there may be some installations wherein the outlet is located so much higher than the inlet that a smaller area outlet than inlet can be tolerated. In many installations, however, it is preferred that the cross-sectional area of the outlet of a passage be at least about ten percent larger than the cross-sectional area of the inlet of the passage so that, as ambient air becomes heated and expands within the passage, it will be encouraged to discharge through the less restrictive, larger area outlet than through the smaller area inlet.
The preferred way of providing an outlet that is of larger cross-sectional area than the associated inlet is to provide the passage with an increase in cross-sectional area somewhere along a central region of the passage (i.e., between opposite end regions of the passage). The increase in cross-sectional area can be provided at a specific location along the length of a passage, or at a plurality of locations along the length of a passage, or may be defined by one or more tapered regions of the passage so that the increase in area is gradual rather than
Burge David A.
Ferensic Denise L.
Rinehart K. B.
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