Numerical investigations of heat transfer over a moving surface due to impinging knife-jets

Turbulent flow field and heat transfer from an array of impinging horizonta l knife jets on a moving surface have been investigated using large eddy si mulation (LES) with a dynamic subgrid stress model. The surface velocity di rected perpendicular to the jet plane is varied up to two times the jet vel ocity at the nozzle exit. Performance of a horizontal knife jet with an exi t angle of 60 degrees is compared with the standard axial jet. It has been observed that increasing surface motion reduces heat transfer for both type s of jets. However, the amount of heat transfer from the knife jets is more than that from the axial jets when the surface velocity is within the orde r of half the jet velocity at the nozzle exit. For further increase in surf ace velocity, heat transfer from the knife jets is, however, less than that in the case of axial jets if the Reynolds number (Re) is low. For higher R e and higher surface velocity, the heat transfer from either type of jets i s of comparable magnitude.