Experimental investigation of the influence of a magnetic field on the hat transfer between an argon plasma flow and the channel walls

Abstract

The influence of an external transverse magnetic field on the heat transfer between a low-temperature argon plasma flow and the channel walls is experimentally investigated for Reynolds numbers in the laminar and transition regions of the flow. It is shown that the magnetic field has only a slight effect on heat transfer within the range of parameters studied. Application of a magnetic field leads to a decrease in heat transfer. From the general statements of magnetohydrodynamics, it is known [1] that an external magnetic field can have a pronounced effect on the flow of an electrically conducting medium and, in the case of ' nonisothermal flow, even on the heat transfer with the environment or with the channel walls. The nature of the influence of the magnetic field depends on various factors. The principal factors are: therelative orientation of the vectors of magnetic induction and of the mean flow rate; the flow regime; the specific characteristics of the conducting medium; the magnitude of magnetic-field induction; and the electrical conductivity of the channel walls. Theoretical and experimental investigations of heat transfer in magnetic fields are concerned mostly with flows of electrically conducting fluids (liquid metals and electrolytes) in channels. A fairly complete survey of the progress in this field is to be found in [2]. Heat transfer involved in low-temperature plasma flows in a magnetic field is characterized by such specific features as the presence of appreciable temperature and conductivity gradients both across the flow and along the channel axis, the Hall effect, and ion recombination. Methods based on approximate physical simulation of plasma flows by conducting fluids are suitable for studying heat transfer of plasma flows only within certain well established limits. Only few papers [3,4] deal with the experimental investigation of the influence of magnetic fields on the heat transfer in low-temperature plasma channel flows. These papers deal primarilywithqualitative determinations of the nature of the influence of a magnetic field in the turbulent range of Reynolds numbers. The aim of the present investigation was to determine the nature and magnitude of the influence of a transverse magnetic field on the heat transfer at the inlet section of the channel for various flow rates, various wall temperatures, and various orientations of the crosssection of a rectangular channel with respect to the magnetic field direction. The influence of a readily ionizable addition introduced into the flow on the behavior of heat transfer in the presence of an applied magnetic field is also studied. 1. The experimental equipment was composed essentially of a plasmatron, a mixing chamber, a useful channel length, a rear eham-