Study On Mass Transfer Of CO₂ Absorbed Into Ionic Liquid Mixed Solution In Microchannel

In recent years,micro-chemical technology has attracted widespread attention due to its great heat and mass transfer performance.Study on gas-liquid two-phase flow and heat/mass transfer in microchannel is of fundamental importance for the design and application of microreactor.The gas-liquid two-phase flow and mass transfer for carbon dioxide absorption into ionic liquid mixtures were studied by a high speed camera and pressure transducers in microchannel.The effects of gas and liquid two-phase flow rates and ionic liquid mass fraction in solution on flow pattern,void fraction,pressure drop and mass transfer performance,were investigated experimentally.The gas and liquid two-phase flow patterns in microchannel were real-time visualized and recorded by a high speed camera,the bubble-slug flow,slug flow and slug-annular flow were observed.Flow pattern map and transition lines were obtained according to experimental data.As ionic liquid mass fraction increased,slug flow zone and transition lines moved to the higher superfacial gas flow rates.Flow pattern transition equations applicable for gas-liquid two-phase flow accompanying mass transfer in microchannel were put forward,with a good predicting performance.Void fraction under slug flow pattern was obtained by photogrammetry.The increase of gas flow rate and the decrease of liquid flow rate and ionic liquid mass fraction could all lead to the increases of bubble length and void fraction.A void fraction prediction model based on Lockhart-Martinelli model was proposed,with little deviation between the predicted values and experimental data.Pressure drop between the inlet and outlet of the microchannel was measured.Results showed that,the increase of two-phase flow rates and ionic liquid mass fraction could result in the increase of total pressure drop.A semi-theoretical prediction model for pressure drop was obtained,with a good predicting performance.Specific surface area,liquid side volumetric mass transfer coefficient and liquid side mass transfer coefficient were calculated by photogrammetric processing of experimental pictures.Specific surface area would increase as the increase of gas flow rate and the decrease of liquid flow rate and ionic liquid mass fraction.With the increase of two-phase flow rate ratio,liquid side volumetric mass transfer coefficient and liquid side mass transfer coefficient could increase and flatten out gradually.There is a critical flow rate ratio,before which the liquid side volumetric mass transfer coefficient and liquid side mass transfer coefficient decreased with increasing ionic liquid mass fraction.While after the critical ratio,they increased with increasing ionic liquid mass fraction.Based on experimental data,a dimensionless correlation for predicting liquid side volumetric mass transfer coefficient was proposed.The model has a great predicting performance.