| Photocatalytic oxidation（PCO）,an advanced oxidation technology,has been highly appreciated to improve indoor air quality.In this thesis,we mainly designed the honeycomb photocatalytic reactor with the front deflector and sinusoidal wall annular photocatalytic reactor.Based on computational fluid dynamics（CFD）,the velocity field,concentration field,and turbulent viscosity in the reactor were numerically simulated.We reveal the effect of multiple physical fields on the purification efficiency of the photocatalytic reactor and clarify the mechanism of the reactor’s internal structure on the flow field of the photocatalytic reactor in this thesis.Firstly,the front chamber of the original honeycomb reactor was designed,and different structures of front deflector honeycomb photocatalytic reactors were obtained by arranging deflector plates and porous airflow distribution plates,which were numerically simulated by CFD.The simulation results show that the original model has a huge vortex near the inlet,which leads to uneven velocity and formaldehyde concentration distribution inside the reactor,while the model with a 45°deflector plate（S-4）can effectively overcome these drawbacks compared with the other models.At an inlet velocity of 0.04 m s-1,the formaldehyde photocatalytic conversion of S-4 increased by 7.29%compared to the original model.In addition,the effects of velocity,relative humidity,radiation intensity,and initial formaldehyde concentration on the formaldehyde photocatalytic conversion were also investigated based on the S-4 model.The results showed that the change in inlet velocity had a greater effect on the photocatalytic conversion of formaldehyde.The photocatalytic conversion of formaldehyde increased when the inlet velocity decreased.The relative humidity showed a linear relationship with the photocatalytic conversion of formaldehyde,and as the relative humidity increased,the water molecules competed with formaldehyde for adsorption more intensely,which in turn contributed to the decrease of the photocatalytic conversion of formaldehyde.The formaldehyde photocatalytic conversion increased by 10.78%when the irradiance was increased from 45 to 265 m W cm-2.Secondly,in order to enhance the mass transfer capacity of the annular photocatalytic reactor,the wall coated with photocatalyst was designed as sinusoidal type,and the effects of amplitude and angular frequency on the radiation field,velocity field,turbulence viscosity,and trichloroethylene photocatalytic conversion rate of the annular photocatalytic reactor were analyzed.The results show that the radiation intensity of the photocatalyst surface decreases with the increase in amplitude.In a certain range,increasing the amplitude can reduce the turbulent viscosity and further prolong the contact time between trichloroethylene and photocatalyst,to improve the photocatalytic conversion rate of trichloroethylene.The angular frequency has little effect on the turbulent viscosity.The effects of inlet velocity and initial concentration on photocatalytic trichloroethylene removal rate were investigated.The simulation results show that the photocatalytic conversion rate of trichloroethylene decreases with the increase of inlet velocity and initial concentration of trichloroethylene.The change of inlet velocity will affect the distribution of the velocity field in the reactor,and thus affect the distribution of turbulent viscosity,and further lead to different degradation amounts of trichloroethylene at different locations in the reactor.Overall,the optimized design of a front deflector honeycomb photocatalytic reactor and sinusoidal wall annular photocatalytic reactor in this thesis was carried out to simulate and analyze the flow field,concentration distribution,and radiation field in the reactor,which has theoretical guidance for the future development of high-performance photocatalytic reactor. |
