CO2在纳米流体解吸过程中的微对流现象

建立了一套水平气液界面传质模拟装置，利用粒子成像测速仪（PIV）对CO2从乙醇和乙醇纳米流体中解吸过程液相流场进行了观测和分析。传质发生时，在近界面处均观察到了由Marangoni效应造成的湍动。通过对平均速度的分析，发现在乙醇纳米流体中发生的湍动强度和湍动范围较乙醇溶液中大。纳米流体中的Marangoni效应加剧了纳米粒子的布朗运动，引发了纳米流体中的微对流，从而将界面处的湍动传递至液相主体中，导致液相主体的漩涡增多、流体混合加剧，促进了气液传质。

Microconvection phenomena accompanying CO2 desorption from nanofluids

An experimental system for observing horizontal gas-liquid interface mass transfer process was established.With the aid of particle image velocimetry(PIV),the instantaneous liquid velocity distribution near mass transfer interface was measured in the processes of CO2 desorption from ethanol solution with or without nanoparticles.The occurrence and development of interfacial turbulence caused by Marangoni effect was observed during such processes of mass transfer.It showed that more vortices generated and penetrated deeper into the bulk with the addition of nanoparticles.Then the effect of nanofluid on mass transfer intensification was analyzed based on the calculation of time-average velocity field.The results suggest that the time-average velocity at the interface is larger than that in the bulk liquid,and grows with the increase of N2 flux and nanoparticles concentration.As CO2 desorbs from the bulk liquid,the concentration of CO2 is reduced,the time-average velocity away from the interface in the ethanol solution without nanoparticles decays apparently;nevertheless,it is almost constant in the nanofluid.Compared with the ethanol solution without nanoparticles,the turbulent intensity and turbulent range with nanofluid are greater.It is believed that Brownian movement of nanoparticles,which leads to microconvection of nanofluid,is intensified by Marangoni effect.The microconvection makes the instability occurring initially at the interface enlarge to the bulk.Therefore,the vortices and the fluid mixing of liquid in nanofluid are enhanced,improving the mass transfer between gas and liquid.