Simulation And Optimization Study Of Ventilation In Piggery With Air Filtration

With the continuous large-scale and intensive development of pig breeding industry,the density and total amount of pig breeding have increased sharply,and the importance of biosafety for pig production has become increasingly prominent,especially the outbreak of African swine fever in China in recent years.How to improve the prevention and control ability of pig house disease has become the focus of research.Has attracted much attention of the piggery vertical ventilation air filter function,the use of air filtration technology to prevent outside germs enter the pigpen,and vertical ventilation mode can reduce the bacteria levels within diffusion ability,but the structure of air filtration system and vertical ventilation airflow movement is more complex,the lack of related research for this kind of new type ventilation piggery condition.In recent years,Computational fluid dynamics(CFD)is often used in the research of pig barn ventilation due to its advantages of low cost,visualization and systematic analysis.Due to the large number of pores,small size and random distribution of the filter in the air filtration system,it is difficult to model the filter entity and the simulation cannot be carried out.Therefore,this paper tries to simplify the solid modeling of filters by using porous media model,and then completes the CFD simulation and optimization research on the ventilation of this kind of piggery.The main research contents and conclusions are as follows:(1)Aiming at the problems of air filtration effect,service cost and life of air filtration system,this paper studied and designed a piggery air filtration system composed of three layers of filters.In view of the porous structure of the filter,this paper tries to use porous media model instead of solid filter modeling.In order to verify the accuracy of the simplified model of filter porous media,the filter used in the above design was used to build a test device,and the accuracy of the simplified model was verified by CFD simulation values and measured values of wind speed at 36 verification points inside the device.The results show that: Normalized Mean Square Error(NMSE)of CFD simulation reliability evaluation is 0.007,which is within the acceptable range.The Normalized mean square error(NMSE)of CFD simulation reliability evaluation is 0.007.It shows that the porous media model can replace the filter solid modeling.(2)In order to study the ventilation of this new type of piggery with air filtration function,this paper completed CFD simulation of the internal air flow track and air flow field distribution of the piggery based on the model simplification method mentioned above,and verified the accuracy of the simulation results through the simulated and measured wind speed values of 72 test points in the piggery.Finally,the ventilation of the new piggery is studied according to the simulation results.The results show that the mean absolute error,relative error and NMSE are 0.221 m/s,15.6% and 0.009 respectively.The simulation results are reliable.The overall wind speed in Peihuaishe pig breeding area is about 0.4-0.8m /s.The maximum wind speed at the outlet of the ventilation pipe is about7m/s,and the minimum wind speed is about 6m /s.There are problems of uneven ventilation..(3)In view of the problems in the ventilation of the piggery,combined with the measured wind speed of the outlet of the ventilation pipe of all the piggery in the test farm,this paper selected the finishing barn with the most serious problems to carry out optimization research.It is proposed that the ventilation duct with equal cross-sectional area should be optimized as the ventilation duct with the distance from the fan position decreasing from large to small,and the ratio of the cross-sectional area of the large and small ends is 2 to 1.Through the simulation of piggery ventilation before and after optimization,the maximum wind speed at the outlet of ventilation pipe is about 9.5m /s,and the minimum wind speed is about 7.5m /s.After optimization,the wind speed of all air outlets is about 8 m/s,and the uniformity of ventilation is improved to complete the optimization design.This paper provides a reasonable,reliable and economical method for the simulation study of the ventilation of the new piggery,and provides ideas and guidance for the optimization of its ventilation design.