Measurements of solid particle suspension concentrations in boiling pools

Abstract

An experimental study was performed to measure vertical particle suspension concentrations in contaminated boiling pools. The study was conducted in a nucleate boiling regime. Tests were conducted with distilled water and solid nickel particles ranging in size from 5 to 40 μm. The test apparatus was 30 cm wide and 120 cm high. Particle concentrations were on the order of milligrams per cubic centimeter of slurry. Heat fluxes on the order of 100 kW m −2 were attained by electrical bottom heating. Corresponding superficial vapor velocities were on the order of several centimeters per second. Measurements were aimed to reveal the dependence of dilute particle suspension distributions on the pool depth, heat flux and particle loading. The results indicate that only a fraction of the particle loading gets suspended. This fraction turns out to be largely dependent on the pool depth and heat flux, but is insensitive to particle loading variations. The particle distribution within the suspension was analyzed with the dispersion–sedimentation model. The work demonstrates the applicability of this model for the conditions of boiling pools and partial particle suspensions. Furthermore, the results indicate that for shallow pools and small size particles the distributions are fairly uniform. Consequently, the suspension concentration is substantially a function of the fraction suspended. The work provides experimental data to evaluate this fraction for a range of heat fluxes and pool depths. The knowledge of particle suspension concentrations has important industrial and environmental applications in the power generation, nuclear and chemical engineering industries. For example, the results could be used to evaluate the amount of particle released from a contaminated boiling-pool spill, or could be used to reduce conservatism applied in analyses of pools containing larger particles.