DESIGN STUDY OF COAL-FIRED CORED BRICK REGENERATIVE HEAT EXCHANGERS
A design study was conducted for cored ceramic brick regenerative heat exchangers for use as air preheaters in coal-fired open cycle magnetohydrodynamic (MHD) power generation systems. These systems consist typically of eight to twenty-four identical heat exchangers each of which cycle between blowdown (where compressed air is heated) and reheat (with slag and seed laden coal combustion products). Air preheater designs for a 2000 megawatt electrical MHD power plant were analyzed with a computer code that simulates the transient cyclic behavior of the heat exchangers, uses local instantaneous ceramic and gas properties, and contains a Nusselt number correlation which includes rough surface and entrance effects.
The design problem was formulated such that only the reheat inlet velocity and ceramic bed length must be determined to complete a design. These are presented as functions of the ratio of reheat/blowdown heat exchangers and total cycle time for fixed core geometry and stress levels. Also presented are ceramic mass requirements, flow passage roughness effects, and the sensitivity of air preheater performance to variations in the geometrical and operational parameters.