Investigation of the hydrodynamics processes and heat transfer in the combined film-type evaporation apparatus during the concentration of low-level liquid waste containing surfactants

Investigation of the hydrodynamics processes and heat transfer in the combined film-type evaporation apparatus during the concentration of low-level liquid waste containing surfactants.

Khomyakov A. P., Kolupaev D. N., Ponizov A. V., Vasilishin A. V., Shkurin P. A., Prokhorov S. V., Mordanov S. V., Gushshamova V. N., Khomyakova T. V.

The article presents the results of the study of the hydrodynamics processes and heat transfer in the combined film-type evaporation apparatus during the concentration of low-level liquid waste containing surfactants. The experimental study of the heat transfer process was carried out on the experimental evaporation plant at moderate thermal loads in the range from 15.6 to 31.6 kW/m2 for the heating chamber with the falling film and from 10.5 to 20.1 kW/m2 for the heating chamber with the rising film. The irrigation intensity for the heating chamber with the falling film had values in the range of 500–900 kg/(m·h). For evaporation, a simulator solution was used, which had the properties of a low-level liquid waste containing surfactants.
The study of the hydrodynamics of the two-phase flow of the evaporated low-level solution containing surfactants in the heat exchange tubes of the heating chambers of the apparatus was carried out using numerical modeling. The results of numerical modeling are the distributions of local values of the mass flow rate of a low-level solution containing surfactants, the mass flow rate of secondary steam, the velocity of secondary steam, and the absolute pressure along the length of the heat exchange tube, depending on different values of the initial irrigation intensity.
The values of the heat transfer coefficient were obtained in the experimental evaporation apparatus. Under these conditions, evaporation of the simulator solution showed the complete absence of foaming in the separator of the evaporator and the absence of foam in the condensate of the resulting secondary steam discharged from the condenser. Numerical modeling of hydrodynamics has shown the fundamental possibility of evaporation of low-level solutions containing surfactants on the combined film-type evaporation apparatus.
It is shown that it is advisable to use the combined film-type evaporation apparatus when handling liquid radioactive waste from nuclear energy facilities.
Further research directions have been identified.

► Keywords: liquid radioactive waste, film-type evaporation apparatus, heat transfer, numerical modeling.

Article language: Russian. Pp. 28–42. [in Russian]. DOI: 10.26277/SECNRS.2024.112.2.003.