Experimental Study of Flow and Separation in Vortex Tubes With Application to Gaseous Fission Heating

Abstract

An experimental investigation of the flow in simple jet driven vortex tubes under conditions dynamically similar to those estimated to be necessary for operation of a vortex cavity reactor indicated that viscous retardation of the vortex motion near the periphery is severe. Estimates of virtual viscosities and skin friction coefficients based on an assumed two dimensional flow field were correlated in terms of the peripheral tangential Reynolds number based on the tube diameter. Friction coefficients so defined for vortex flow appear to be high by a factor of about two compared with those for turbulent flow along a flat plate with zero pressure gradient. Observed tangential velocities are compared with theoretical calculations for viscous vortex flow in terms of the turbulent radial Reynolds number. This comparison suggests that virtual viscosity probably decreases with decreasing radius. Extrapolation of the experimental results to typical reactor operating conditions indicated the need for small diameter tubes and recirculation of a large fraction of the inlet gas in order to achieve adequate vortex strength without exceeding an allowable exit mass flow rate. Quantitative measurements of concentration profiles for separation of helium and a heavy fluorocarbon vapor were made using a radial gas sampling probe andmore » thermal conductivity analysis. The data are compared with laminar flow separation theory. (auth)« less