US 2781188 A
Description (OCR text may contain errors)
' Feb. 3.2, 1957' c. G. MQKEOWN MEANS FOR COOLING THE LOAD OF A COIL ANNEALING FURNACE OR THE LIKE 3 Sheets-Sheet 1 Filed July 6, 1953 CUBE Dunn ORNE Feb. 12, 1%? c. G. M KEOWN 978L188 MEANS FOR COOLING THE LOAD OF A COIL ANNEALING FURNACE OR THE LIKE Filed July 6, 1955 3 Sheets-Sheet 2 CHARLES GEORGE "McKEOW/V A 7' OHNE "W e1 13 EQEE). i2, 1%? c. G. MOKEQWN 2 ?81,E8
MEANS FOR COOLING THE LOAD OF A COIL ANNEALING FURNACE OR THE LIKE Filed July 6, 1953 5 Sheets-Sheet 3 //v VENTOR V W raw 5 United States Patent Ofice 2,781,188 Patented Feb. 12, 1957 NIEANS FOR COOLING THE LOAD OF A COIL ANNEALING FURNACE OR THE LIKE Charles George McKeown, Dudley, England, assignor to Controlled Heat & Air Limited, Smethwick, England, a British company Application July 6, 1953, Serial No. 366,277
1 Claim. (Cl. 266-2) This invention relates to an improved means for cooling the load of a coil annealing furnace after the heating cycle and has for its object to reduce the time taken in cooling thereby increasing the output of the furnace.
In coil annealing furnaces as at present in use, the load to be treated is contained within an inner casing within which a purging gas is circulated by means of a fan located at the bottom of the load and is sealed from the products of combustion. The outer casing of the furnace fits over the load casing and during the heating phase heat is transferred to the load through the load casing by radiation and convection. In present practice after the heating and soaking phase is completed the outer casing of the furnace is removed and the circulation of the purging gas within the load casing is maintained, whilst the heat that is transferred from the load to the load casing by means of radiation and convection is dissipated to atmosphere by the natural cooling of the load casing. Thus the speed of cooling of the load is dependent upon the rate at which the load casing can transfer to still atmospheric air the heat it receives from the load.
According to the present invention means for cooling the load of a coil annealing furnace is provided comprising a cover adapted to be fitted over and around the load casing of the furnace after the heating casing of the furnace has been removed said cover defining with the load casing 21 space surrounding the load casing through which air is drawn upwardly by a fan situated within an aperture in the upper portion of the cover.
A convenient embodiment of the present invention will now be described as applied to a coil annealing furnace of the kind incorporating a plurality of load casings each enclosing a load and in the following description reference will be made to the accompanying drawings in which:
Fig. 1 is a part sectional side elevation showing the base of a coil annealing furnace having four load casings mounted thereon with the heating casing removed and replaced by a cover in accordance with the present invention. In this drawing the left hand load casing is shown in section, the adjacent load casing is shown in side elevation and the pair of load casings on the right hand side of the drawing are hidden by the cover which is shown in elevation.
Fig. 2 is a section on the line AA of Fig. 1 looking in the direction of the arrows, and
Fig. 3 is a sectional plan of Fig. l, the section line being taken on the line BB for the two left hand load casings, and on the line CC for the two right hand load casings.
In the drawings 4 represents the normal base of the coil annealing furnace which incorporates the usual form of sand seal 5 for the outer heating casing of the furnace when in position. Also mounted on this base are a plurality of, in the present instance four, cylindrical load casings 6 in which the coil loads 7 are disposed. Fans 8 are provided on the base for circulating a purging gas through the load 7 in each load casing 6 in normal manner.
According to the present invention, after the outer heating casing has been removed at the completion of the heating and soaking phase there is fitted in its place over the load cylindrical casings 6 of the furnace, the cover 9 which is open at its lower end and is provided with a surrounding seal 10 which engages with the sand seal 5 on the base 4 in a similar manner to the outer casing of the furnace when the latter is in position.
The cover 9 is of such a shape that it is spaced from the load casings 6 so as to leave a surrounding passageway 11 which is of uniform cross-section except for those portions 11A, which are between two adjacent load casings, 6. Where the coil annealing furnace incorporates only one load casing 6, then it will be appreciated that the cooling cover 9 will be of a contour which will leave an annulus 11 of uniform cross-section throughout.
In the cover 9 and co-axia-lly disposed one above each cylindrical load casing 6 are converging/diverging ducts 12, within the narrowest portions whereof are disposed fans 13 of the axial flow type, having a large volume low pressure ratio characteristic which are adapted to be driven by individual electric motors 14.
The cover 9 is provided around the lower portion of its periphery with a plurality of equally spaced inlet ports 15 through which atmospheric air is adapted to be drawn by the fan 13 into the space 11 between the load casings 6 and the cover 9 and upwardly therein for discharge to atmosphere by the fans 13 through the ducts 12 at the top of the cover 9.
Auxiliary air inlets 17 may be provided around the periphery of the cover at points above the main air inlets 15, said auxiliary air inlets 17 being provided with doors or valves whereby they may be opened or closed.
In order to shield each motor 14 from radiant heat emitted from the associated casing 6 and also to improve the air flow through the duct 12, in which it is accommodated, there is positioned within the converging and lower portion of each duct 12, a cone 16.
When the cover 9 is in position and the fans 13 are operating the flow of cooling air from the main air inlets 15 upwardly through the space 11 to the fan traverses the full surface of the load casings 6 to which heat is being imparted by the scrubbing action of the purging gas circulating within the load casings.
It is a well established fact that the rate of heat flow from a hot surface to air or gas is greatly accelerated if air or gas is caused to move in turbulent flow in close contact with the hot surface. The application of the cover 9 over the load casings 6 in accordance with the present invention forms a defining path wherein the cooling air is caused to move in intimate contact with the outer wall of the load casings 6, thereby transferring the heat relatively quickly from the load casings 6 to the air which is being discharged at the top of the cover through the ducts 12 by the fans 13. It may be pointed out that since the cover 9 fits over the load casing or casings 6 in a similar manner to the heating casing of the furnace a usual form of sand seal between the load casing 6 and the base 4 as illustrated is not disturbed and further, due to the fact that the flow of cooling air is in an upward direction from a point above this seal the seal is not disturbed during the cooling phase.
Cooling means for loads being processed in a coil annealing furnace having a base surmounted by load casings with substantially cylindrical vertical walls, said cooling means comprising means for circulating purging gas within said load casings and along the inner surfaces of said walls, a thin metal cover adapted to be lowered over such load casings, said cover having curved vertical wall sections which when said cover is so'lowered are substantially uniformly radially spaced from the cylindrical vertical walls of such load casings, said cover being formed with converging-diverging ducts which when said cover is so lowered are located axially above the respective load casings, an axial flow type fan mounted within each of said converging-diverging ducts to evacuate air from within said cover by drawing such air upwardly along the vertical wall sections of said cover and along the outer surfaces of the cylindrical vertical walls and over the tops of said load casings, thereby abstracting heat from said load casings, transferring heat to said cover and I carrying heat away through said ducts, a conical shield positioned below each said 'fan with its apex pointing upwardly, each of said curved vertical wall sections being provided with a plurality of main inlet ports adjacent its lower end to admit air to the space surrounding the load casings, each of said curved wall sections being provided also with an auxiliary inlet port located above said main inlet port and damper doors for regulating the inflow of air through said auxiliary inlet ports.
References Cited in the file of this patent UNITED STATES PATENTS 2,249,411