ENHANCEMENT OF LAMINAR BOUNDARY LAYER HEAT TRANSFER BY LONGITUDINAL VORTICES

Abstract

This chapter focuses on the enhancement of laminar boundary layer heat transfer by longitudinal vortices with a small additional pressure loss. Longitudinal vortices potentially enhance the heat transfer with a small additional pressure loss. Longitudinal vortices generated by half-delta wings attached to the surface at an angle of attack persist over a long streamwise distance, disturbing the entire velocity and temperature fields. The chapter also discusses a series of experimental and numerical works conducted aiming to understand the heat transfer aspect of flows dominated by longitudinal vortices, and to clarify the mechanism of heat transfer augmentation and get insights in order to propose vortex generators configuration for use in heat transfer equipment. Considerable enhancement of heat transfer occurs with a modest pressure loss penalty. The chapter further discusses the effects of longitudinal vortices generated by a single vortex generator and a pair of vortex generators on heat transfer of an otherwise laminar boundary layer. It describes an experiment in which the angle of attack, height, and geometry of the generators served as a parameter for heat transfer measurements closer to the vortex generators. It was found that large local enhancement was achieved in regions where the regime is predominantly laminar by the boundary layer thinning due to the vortical motion.