Enhancement of Forced Convection Subcooled Film Boiling Heat Transfer Using Gas Sheet Collapse by Electric Field Application

摘要

Enhancement of forced-convection boiling heat transfer by electric field is investigated experimentally. When a high-temperature horizontal filament is immersed in water, a gas sheet is formed around and the above filament due to liquid boiling, in the early immersion process. This gas-sheet markedly decreases the boiling cooling rate of the filament. Here, forced collapse of the gas sheet is attempted by imposing an electric field to enhance the boiling cooling rate, In the experiments, a horizontal platinum wire of 0.5 mm in diameter is immersed in pure water under atmospheric pressure, and a DC voltage up to 600 V is applied between the wire surface and an electrode made of glass placed 10 mm apart. The whole boiling curve is measured under different applied voltages and wire-falling velocities in 0.5 to 2.0 m/s range, and at subcooling of 60 K. The experimental results show that the electric field is effective in promoting the disintegration of the gas sheet. Under the tested conditions, boiling cooling rate increased two-fold for an applied electric field of 600 V/cm. This result shows that the use of an electric field to break up the gas-sheet has resulted in a remarkable increase in the cooling rate at high superheats during initial cooling period, which is even greater than that used in the existing material manufacturing processes by the rapid cooling method, and therefore, this method may contribute to developing new materials.