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Water cooled panel WATER COOLED ELEMENTS FOR STEELMAKING FURNACES
Covered AC Furnace roofs are typically assembled from a few large, monolithic panels, bolted together along their common edges using an insulation detail to segregate the sub-assemblies electrically.
The panels extend from the periphery of the roof to near the electrode PCD, and the assembly is closed by means of the so-called ‘delta section’.
Each panel incorporates feed, inspection, off-gas and over-pressure control ports in different combinations as required.
Symmetry is difficult to achieve due to layout constraints, making spares rationalisation and storage problematic.
The large panels are difficult to remove and replace during maintenance shutdowns.
The unavoidable triangular shape of the panels, together with discontinuities introduced by the feed ports pose many The Twelfth International Ferroalloys Congress Sustainable Future June 6 – 9, 2010
It challenges to obtain a design that can be water cooled efficiently and is easy to fabricate. The resulting design is often a compromise.
The theoretical maximum surface temperature is acceptable provided that the panel is operated under conditions similar to the assumed boundary conditions.
The internal rectangular, serpentine passages give rise to stagnant flow areas, particularly where the cooling channel pattern is interrupted at the feed port. Note the correlation between stagnation and localised hot spot formation. T
he design criteria for the conceptual design work were to reduce or eliminate the internal passages, improve flow around circular discontinuities such as feed ports, and modularise the roof with smaller, symmetrical panels, which would be easier to replace in service.
A preliminary generic model with representative geometry, heat load and flow rate parameters was evaluated using arrays of small vertically orientated cylindrical baffles to disperse and marshal the flow from a single inlet to a single outlet respectively without the need for serpentine passages.
As an alternative, an array of 4 jets situated at the periphery of the panel was used to induce flow towards a single outlet at the inner edge without serpentine passages.
The results were not convincing, but it was noted that the cylindrical baffles effectively distributed flow across the panel cross section.
The resulting low velocity produced corresponding low heat transfer coefficients, which restricted heat transfer. The rectangular serpentine concept was then revisited and refined, using strategically positioned cylindrical baffles to improve flow in areas where flow stagnation occurred. |
