再生冷却通道中超临界氨换热特性数值研究OA

Significant coking of hydrocarbon fuels was observed in regenerative cooling channels at high Mach numbers,replacing hydrocarbon fuels with liquid ammonia as a coolant is an effective solution to this problem.Numerical study on flow and heat transfer of supercritical-pressure ammonia in the regenerative cooling channel was conducted,with a focus on exploring the influences of operating pressure(12 MPa,15 MPa)and flow cross-sectional shape(square,trapezium,circle)on heat transfer.The radial and axial conduction characteristics of heat and momentum were elucidated through the distributions of temperature and velocity fields,and the evolution process of vortex structures was revealed through the streamline distributions.The distributions of wall temperature and heat flux were discussed.The mechanism of heat transfer deterioration was elucidated based on the radial distribution of boundary layer fluid mass flow velocity and specific volume heat capacity,as well as the axial distribution of thermal resistance.The heat transfer correlations for supercritical-pressure ammonia in three channels were proposed(error within±15%).The numerical results indicate that the prominent heat transfer deterioration problem is observed on the inner-wall of channel heating side,and the low mass flux,low heat capacity,and high thermal resistance of wall boundary layer are the direct causes of heat transfer deterioration.Abnormal spirals and strong mixing of streamlines were observed in the middle of channel,corresponding to the strongest secondary flow,which is caused by a sudden increase in the fluid density gradient in the cross-section as the bulk fluid enters the pseudo-critical region.The circular cross-section channel has higher flow velocity and more uniform heat flux distribution,resulting in better heat transfer performance compared to trapezoidal and square channels.