Experimental investigation of the machine-free method of temperature separation of air flows based on the energy separation effect in a compressible boundary layer

The process of energy (temperature) separation in an airflow is experimentally investigated in a device consisting of two coaxial channels with heat-conducting walls. The air flows at a supersonic velocity along the inner channel and at a subsonic velocity in the outer channel. The initial total temperatures of the flows are the same. Heat transfer arises due to the energy separation effect in the boundary layer of the compressible flow at Pr ≠ 1. The parameters varied in the process of investigation are the initial flow temperature, the supersonic flow velocity (Mach number), the mass fraction of the subsonic flow, the scheme of the flow organization in the device, and the presence/absence of heat transfer intensifiers in the subsonic channel. In all the regimes considered the subsonic flow cooling and the supersonic flow heating were fixed. The total pressure of the subsonic flow was almost conserved in the maximum cooling regimes. An engineering method of calculating the temperature separation in the similar devices is proposed. The expressions for the limiting values of the flow heating and cooling corresponding to the energy separation using this technique are obtained. The flow parameters that have an effect on the temperature separation efficiency are determined.