Particle residence time distribution and bulk heat transfer coefficients of two-phase flow in scraped surface heat exchanger and holding tubes.

摘要

The residence time and residence-time distribution (RTD) of fresh and simulated particles flowing in a swept surface heat exchanger (SSHE) and holding tube were investigated. The effects of selected experimental conditions on RTD include particle shape (cube, cylinder, and sphere), particle concentration (10, 20, and 30% w/v), particle type (potato, carrot, turkey, green peas, and polystyrene), fluid viscosity (water, 0.5% CMC, and 1.0% CMC), bulk flow rate (;The distribution of residence time curves were narrowed by using higher bulk flow rate and shaft rotational speed, fluid of 0.5% CMC concentration and cubic particles, and by decreasing particle concentration.;It was found that particle residence times in the SSHE were higher than that in the holding tube mainly due to the blades rotation in the heat exchanger. The longest particle residence time was 5.3 times the average bulk residence time of the holding tube while it was 2.62 for the heat exchanger. The fastest particle in the holding tube did not exceed 1.8 times the average bulk velocity while it was 3.27 in the heat exchanger. This finding is within the conservative value of 2.0 considered safe in sizing holding tubes in aseptic processing systems.;A methodology was developed to measure the bulk heat transfer coefficient (h