The experimental research on subcooled flow boiling in vertical narrow rectangular channels with relatively Wide-Ranged parameters

Abstract

A series of tests are performed for subcooled boiling heat transfer characteristics of water in narrow rectangular channels. The channel sizes are 50mm×3mm×1000mm, 60mm×3mm×1000mm and 50mm×2mm×1000mm. The test matrix covers a relative wide range of conditional parameters with a mass flux range of 2003000kg/m2∙s, a system pressure range of 0.25.5MPa and an inlet subcooling of 20100K. The images of bubble behaviors are caught by high-speed camera. The images analysis and sensitive study on each parameter of boiling incipience and subcooled boiling heat transfer characteristics are carried out. The effect of forced convection could not be neglected in wall temperature of ONB prediction. Subcooled boiling heat transfer capacity gets enhanced by bubble sliding. According to the force balance analysis and bubble behavior photograph, flow condition is the main factor to promote bubble departure. To consider the appearance of confined bubble in narrow rectangular channel, the particular confined aspect ratio number α∗ is proposed. By measuring α∗, the effect of geometric characteristic on subcooled boiling heat transfer could be known. The new correlation for ONB prediction and subcooled boiling heat transfer in narrow rectangular channel is developed within the deviation of ±20%. In particular, the ONB prediction correlation shows good performance in prediction based on the database from other literatures.