Simulation on the enhancement of cryogenic removal of volatile organic compounds by sawtooth plate

The corrugated channel can be used to break the accumulation of non-condensable gas (NCG) layers and reduce the resistance to mass transfer in the cryogenic removal of volatile organic compounds (VOCs). In this study, a two-dimensional model for the cryogenic removal of low concentration R134a from nitrogen on a sawtooth corrugated plate channel was established, and the impact of the sawtooth bottom angle on the removal performance of R134a were revealed. The results showed that the isosceles triangular sawtooth corrugated plate can significantly improve the removal efficiency of R134a on the cold wall surface per unit area compared with the flat plate channel. The spatio-temporal average phase change rate (α) of R134a on the sawtooth plate under the conditions of present study was 0.1268g/(m2·s), which increased by 144.6% compared with flat surface. The NCG flow near the cold wall surface will convert from the flowing adjacent to the wall, to off-wall mixing with the bulk flow, and finally to forming the flow blocking zone with stable vortex with the increase in the bottom angle (θ) of the sawtooth corrugated plate. Significant off-wall mixing with the bulk flow of the NCG layer occurred when θ was 13.30° —35.45°, with α ranged from 0.082—0.1268g/(m2·s). The α reached the maximum value of 0.1268g/(m2·s) when θ was 17.46°. The effect of the off-wall mixing with the bulk flow of the NCG layer will decay and the α will keep at a lower level when θ deviated the aforementioned range. The present study can provide a reference for the design of sawtooth corrugated plate structure for cryogenic condensation-freeze removal of low concentration VOCs. © 2023 Chemical Industry Press. All rights reserved.