Simulation And Experimental Study Of Vertical Ventilation Pigsty Environment Based On Slatted Floor

Proper ventilation of pigsty is an important means to improve the pigsty environment,which can effectively adjust the temperature,relative humidity,wind speed,harmful gas concentration and other environmental factors of pigsty,provide a comfortable growth environment for pigs,ensure the healthy growth of pigs and give full play to the production potential.Therefore,the systematic,accurate and rapid design and evaluation of piggery environment is particularly important for pig breeding.Piggery vertical ventilation mode is used in piggery ventilation in recent years,a new technology with air flow path independence,uniform temperature distribution,and low concentration of harmful gases,but compared with horizontal ventilation,the top-down air motion path using computational fluid dynamics(CFD)simulation evaluation of inner environment,needs to be leak floor modeling according to the actual structure,size,to ensure the reasonable and accurate simulation.However,due to the large size difference between the slot of the slatted floor and the pigsty and the cesspool,the problems such as the large number of mesh,poor quality,long solving time and the difficulty of calculation convergence are caused.In the process of CFD solving,different turbulence models are different for the air flow under specific conditions,so the selection of turbulence model is particularly important.Based on the above reasons,the experimental equipment of vertical ventilation piggery was made in this paper according to the proportion of model/prototype=1/5,and the numerical simulation of the environment of vertical ventilation piggery was studied comprehensively.In addition,CFD technology was applied to explore the influence of slot width on temperature field,relative humidity field and airflow velocity field distribution in vertical ventilated pigsty.This study can provide reference for the numerical simulation of the vertical ventilation pigsty environment and its optimal design in the future.The main research contents and conclusions are as follows:(1)Based on CFD technology,the calculation of the viscosity and inertial drag coefficients in the porous media model was carried out,and the numerical simulation of how to use porous media to replace the actual structure of the slatted floor was studied.The results showed that: the pressure drop data was calculated by numerical simulation method,and then use the least squares fitting method to calculate the drag coefficient of the pressure drop data is reasonable,porous media model instead of numerical simulation of the structure of the actual leak floor plan is feasible.(2)By comparing the simulation results of five turbulence models for the vertical ventilation piggery environment,it is found that the RKE turbulence model has the best simulation effect and the SKE turbulence model is also better.(3)By comparing two different modeling methods: porous media and the actual structure of slatted floor,it is found that the porous media model can not only deal with the problems of large number of grids,poor quality and difficulty in calculation convergence caused by the large size difference between slatted floor slot and pigsty,but also improve the simulation quality and computational efficiency.The simulated NMSE values of overall wind speed,temperature and relative humidity in the porous media calculation domain decreased by 36%,11% and 10% respectively,and the calculation time was saved by about 75%.(4)Through the study on the slatted floor with slot widths of 30 mm,20mm and10 mm,it is found that narrowing slot widths can increase the wind speed and reduce the temperature in the pigsty,and the wind speed field,temperature field and relative humidity field in the pigsty are more evenly distributed,and the concentration of harmful gases in the pigsty can be reduced to improve the growing environment of pigs.