Abstract:
Objective Aiming at the problem that the traditional finned-tube heat exchanger with a conventional in-line circular tube structure is prone to flow separation and increased pressure loss under the high-velocity operating conditions of the bypass duct in the cooling air system of aero-engines, this study aims to achieve the balance between heat transfer enhancement and pressure drop control by optimizing the base tube type and tube bundle arrangement, thereby improving the comprehensive performance of the heat exchanger.
Method A comparative analysis was carried out on the flow and heat transfer characteristics of finned-tube heat exchangers with three base tube types (circular, elliptical, and combined circular-elliptical tubes) under in-line and staggered arrangements. A numerical simulation method was adopted, employing the j/f factor as the comprehensive performance evaluation index, and the variations in the velocity field, temperature field, pressure drop, heat transfer coefficient, and fin efficiency of the six configured heat exchangers were systematically investigated.
Result The results indicate that the elliptical tube has a streamlined structure, which can significantly suppress flow separation; the staggered arrangement generally leads to higher heat transfer coefficient and j factor than the in-line arrangement of the same tube type by enhancing flow disturbance, but its influence is weaker than that of the tube geometry; the performance of the combined circular-elliptical tube configuration lies between the above two types.
Conclusion The staggered elliptical tube configuration exhibits the optimal comprehensive performance: at a flow velocity of 120 m/s, its j/f factor reaches 0.0503, representing a 63.2% improvement over the conventional in-line circular tube configuration, which achieves the optimal balance between heat transfer enhancement and flow resistance under high-velocity conditions. This study provides a reference for the structural design and performance optimization of finned-tube heat exchangers applied in high-velocity operating conditions.
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