Study on flow and heat transfer characteristics of cross-jet impingement cooling

Parallel-jet impingement cooling is critical for thermal protection in liquid rocket engines due to its high heat flux and uniformity. However, the impact of practical jet misalignment (e.g., from hydraulic flip or installation deviations) on film cooling remains insufficiently understood. This study addresses this research gap by quantifying the effects of jet Reynolds number (Re), spacing (L_N), and cross angle (Φ) on film flow and heat transfer for cross-jet impingement. Key findings reveal that while increasing jet spacing or reducing cross angle expands the film wetted area, the configuration with large cross angle (Φ=60°) disrupts the expected wetted area growth with Re due to fountain sheet dynamics, complicating the achievement of precise control. Crucially, compared to parallel-jet impingement cooling (Φ=0°), cross-jet impingement with Φ=60° significantly enhances the local maximum heat flux and Nusselt number at specific points but markedly reduces overall cooling uniformity. Quantitatively, at identical jet spacing, the maximum heat flux of cross-jet impingement exceeds that of parallel-jet by 2.78 % on average, while the cooling uniformity index is reduced by 13.56 % on average. Through scaling analysis, novel semi-empirical correlations are established to predict the maximum surface heat flux and Nusselt number along the stagnation line, explaining their deviation from local velocity trends under different boiling modes. These findings provide valuable data and a significant reference for optimizing liquid film cooling systems and mitigating catastrophic failures in thermally critical applications.