Particle Transport and Heat Transfer in Gas-Solid Suspension Flow Under the Influence of an Electric Field

Abstract

An experimental investigation has been carried out demonstrating the feasibility of improving wall-to-fluid heat transfer in solid-gas suspension flow in which the solid particles were electrically charged and were acted upon by forces due to a fluctuating electric field, normal to the flow stream. The suspension, consisting of 30-μ glass beads in air, flowed vertically downward in a rectangular heat-transfer channel. The flow Reynolds number ranged from 1460 to 5840 and the loading ratio from 0 to slightly above 2. An alternating potential of 10-kV peak-to-peak was applied across the half-channel width of 0.635 cm. At the frequency of 7.7 cycles/sec and the loading ratio of unity, the rate of heat transfer was observed to increase by approximately 30 to 60%, depending on the Reynolds number. It was shown that the increase in heat transfer can be largely accounted for by the heat conveyed by the particles from the heated wall to the flow stream. Under certain simplifying assumptions, the increase in heat flux was expressed in terms of the particle influx at the wall and the degree of accommodation of the particles to the wall and fluid bulk temperatures. The principal simplifying feature of the system was the dominant influence of the applied field on the particle transport behavior.