Thermal and hydraulic performance of a compact precooler with mini-tube bundles for aero-engine

It is significant to evaluate whether the classical correlations based on conventional tube size (≥10 mm) is suitable for predicting the flow and heat transfers characteristics of the precooler composed of mini-tube bundles (around 1 mm). In this work, a full-scale heat transfer experiment of precooler is carried out, and the high-temperature incoming air (686 K) in the experiment was produced by burning the mixture of air and alcohol. The numerical simulation of a unit precooler is also conducted with Computational Fluid Dynamics. The classical correlations for the design of heat exchanger are evaluated by both experiments and simulations. The results indicate that the prediction error of classical correlations of flow resistance is less than 10% for both the flow inside the mini-tube and across mini-tube bundles. The classical correlation of heat transfer inside tube can meet the engineering requirements. However, the maximum deviation of Nusselt number prediction for the outside flow across tube bundles reaches 32.1%. A new correlation for calculating heat transfer across a compact precooler composed of staggered mini-tube bundles with a prediction error below 5% is finally established based on the experimental and numerical results.