Numerical analysis on thermal-hydraulic performances of staggered tube bundles for an aero-engine compact precooler

The deeply precooled air-breathing technique is an effective approach to cool down the extreme hot incoming air for hypersonic engine. This paper investigates the thermal performance of staggered mini-tube bundle as the compact precooler for aero-engine application. The coupling heat exchange between the hot air and in-tube coolant is explored. Two methods (i.e., surface temperature method and LMTD method) are used to evaluate the airside heat transfer characteristics. Comparison of predicted Nusselt number and empirical correlations shows that both methods have acceptable discrepancies, especially for surface temperature method. In addition, Nusselt number predicted by the surface temperature method almost keeps identical at different coolant velocities, while the LMTD method is sensitive to the flow velocity of in-tube coolant. In order to better understand the influences of boundary conditions, the detailed analysis for parameters such as inlet pressure, inlet temperature, transverse pitch, coolant velocity and property variation on thermal performance of the tube bundle is carried out.