Computational Fluid Dynamics and Measurement of Flow Field and Wall Temperature Distribution in a Scraped Heat Exchanger Crystallizer

During crystallization the control and effective distribution of heat transfer from the solution to the heat exchanger (HE) plays an important role. Inhomogeneity in temperature on the HE-surface limits the production capacity and increases the tendency of an isolating scale layer formation. To avoid scaling, scraper blades on the HE are commonly used. In a typical axi-symmetric geometry the scale layer formation was investigated. In a previous paper [ROD08] we studied the influence of the flow field on the actual heat transfer distribution 1) by directly measuring the surface temperature field of the HE using LCT and 2) by measuring the flow field inside the crystallizer using 3C-PIV. Due to the difficulty to measure the scraping area, in this paper we studied by computational fluid dynamics simulations the flow characteristics in this area and compare them for verification with the previous experimental results. The large eddy simulations (LES) performed here using Lattice Boltzmann scheme confirmed the measurements results and gave accurate information of the not measurable area between scrapers just above the HE surface. We tested also the strength of LES Lattice Boltzmann simulations for complicated geometries such scraped heat exchanger crystallizers.