| The farming of pigs has evolved from small mixed farms to large-scale farming bases with specialist facilities.Mechanized and intelligent modes of production have replaced traditional farming methods.However,this type of captive and high-density breeding was prone to uneven distribution of the airflow field and inadequate discharge of harmful gases in piggery.Currently,ventilation is one of the most effective means of regulating the environment in pig houses.The correct ventilation pattern could improve the environment’s quality in a piggery.In this paper,the full-size 1:1 3D pig house model was built in the ANSYS software tool,based on the actual measurement data of a nursery pig house in a farming base in Heilongjiang province.In addition,Computational fluid dynamics(CFD)techniques were applied to numerically simulate the velocity,temperature,and trajectory of airflow in the pig house under the current ventilation model.By ascertaining the model’s reliability,the problems of pig house ventilation were analyzed according to the simulation results and offered rationalized optimization solutions.The main contents and conclusion are as follows:(1)A three-dimensional steady-state model was created using the ANSYS software development environment based on the pig hous e measured wind speed,temperature,and geometry.CFD numerical simulations and experiments were carried out on the 3D model.The results show that the relative error between the simulated an d measured values of airflow velocity was in the range of 5.2% to 21%,the average relative error was 11.4%,and the coefficient of determination was 0.9435.The relative error between the simulated and measured temperature values was from 0.45% to 6.8%,and 75% of the measurement points were less than 5%.It shows that the simulated values are in good agreement with the measured values,and the simulation of the environment was reliable for the established 3D model in the nursery pig house.(2)The results of the simulation were analyzed based on the current ventilation model.It was found that the average velocity of airflow in the pig activity area was 0.16m/s.At the range of 0-7m in the Y direction,there was a large area of dead ventilation space in the pig activity area,the maximum velocity discrepancy of airflow was 0.75m/s,and the distribution uniformity of the airflow trajectory line was inadequate.First three columns of pigs in the activity area,the maximum airflow temperature was 27.5 ℃,and the lowest was 20℃.The temperature difference was large,beyond the comfortable temperature range for nursery pigs.(3)The air inlet and outlet position were optimized for the nursery pig house;the roof air inlet and the air supply and exhaust d uct ventilation modes were proposed.The simulation results showed that the airflow trajectory line in the pig nursery is the most evenly distributed in the combined ventilation mode of supply and exhaust ducts,and the variation of velocity and temperature fields is slight.After optimization,the unevenness coefficient of air velocity distribution decreased by 0.11,0.35,and the average air velocity in the active area of the pig increased to 2m/s.The air average velocity in the manure accumulation area is increased to 0.41m/s,which speeds up the airflow,avoids contact with the pigs during the flow,and has a better ability to remove exhaust gases.It helped to keep the pig house insulation.Furthermore,the distance L between the air inlet and outlet i n the combined ventilation mode of the supply and exhaust air ducts was simulated.The results showed that the number of ventilation dead space in the house was minimized in the case of L=3m,and the ventilation effect was most effective.(4)This study adapted the combination ventilation of supply and exhaust duct to the renovation nursery pig house and tested it.The results showed that the wind speed and temperature in the house matched the simulation results and significantly improved the ventilation effects of the pig house. |
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