Recently, interest in spiral heat exchangers has grown for high temperature, high cycling applications, especially in the gas turbine industry. Air and gas flow distribution in heat exchangers is known to play a major role in their pressure drop performance and effectiveness. Modelling this distribution is needed to optimise the primary surface geometry. This optimisation has been applied to the ACTE spiral recuperator and resulted in smaller and lighter recuperators thanks to a better use of the metal. A specific CFD code was developed and used to investigate different ‘state of the art’ flow configurations and hydraulic diameters. The best of these was then adapted to ACTE’s manufacturing technology. The model has been validated by pressure drop, velocity profile and effectiveness measurements. The improved geometry consists of a primary surface cross-corrugated pattern for both air and gas flows (see fig. 4 and 5). The pattern includes a central zone with a half angle of 30° for counterflow and two lateral zones with a half angle of 45° for fluid distribution and collection. The corrugations are not strictly sinusoidal but include a flat area that allows welding the two sheets together. The sheet pair (or “doublet”) is thus made resistant to ballooning. It is also used to hoop the annular heat exchanger.

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