Numerical study of the effect of flow nonuniformities on the low-pressure side of a Cooled Cooling Air heat exchanger

The Cooled Cooling Air (CCA) heat exchanger is a precooler that cools the bleed air from the compressor stages and is located inside the bypass duct of the aeroengine. Nonuniform flows enter the core of the heat exchanger because the cold side is the off-take from the fan flow, compromising its aerothermal performance. These aspects has been disregarded in the literature until now. In this study, the aerothermal performance of a CCA heat exchanger with flow nonuniformities on its Low-Pressure (LP) side is investigated. Three-wire meshes were designed using correlations from the literature, showing three off-design cases, namely, Cases 1, 2, and 3. The porous media and dual cell heat exchanger models were used in numerical simulations for the baseline and off-design cases. Experiments were performed at hot and cold conditions to validate the numerical simulations under actual gas turbine operating conditions. It has been found that heat transfer rate increases in Case 1 and 2 by 1.0% and 1.5%, as the flow non-uniformity is symmetric with respect to XZ plane. In contrast, in Case 3, the heat transfer rate reduces by 4.2% because the flow non-uniformity is asymmetric with respect to XZ plane, inducing cross-flows immediately upstream of the heat exchanger core.