Study On Environmental Simulation And Ventilation Optimization Of Northern Growing Pig Houses In Summer

Large-scale pig farms have high feeding density,the high density of pig distribution deteriorates the growing environment of the pig house,which in turn will affect the health ang growth of pigs.The northern pig house is hot in summer and cold in winter,many pig farms do not pay enough attention to the environment of the pig house,especially in the summer,the temperature and ventilation of the pig house can not be reasonably adjusted,resulting in high temperature and poor air quality in the pig house,which affects the normal growth of pigs.Therefore,it is necessary to make in-depth research on the pig house environment,analyze the environment characteristics of the pig hosue in summer,study the control ways and measures to improve the pig house environment,and provide a more suitable environment for the growth of pigs,so as to achieve the purpose of improving the breeding level and economic benefits.The research object of this thesis is the growing pig hosue of a large-scale pig farm in Shandong province in summer,the temperature field,wind speed field and CO2 concentration field of the growing pig house was tested on the spot,and the measured data were analyzed.Then,the model of the pig hosue was established for numerical simulation,and the simulated values was compared with the measured values,which verifies the feasibility of the model and conducts in-depth analysis of the simulation results.Finally,in view of the existing problems in the growing pig house,the air flow organization form and air supply parameters are optimized in turn,so that the temperature,wind speed and CO2 concentration of the pig activity area are suitable for pig growth,and a comparative study was made on the angled air supply air of the square diffuser and the vertical supply air of the round mouth.The main result of this thesis are as follows:(1)By analyzing the measured results of the growth piggery,it can be seen that the temperature,wind speed and CO2 concentration of the pig house are unevenly distributed in the direction of height,the values of different measuring points differ greatly.The temperature and the concentration of CO2 are negatively correlated with height,and the wind speed is positively correlated with height.At the height of 0.6m,the temperature is always above 25℃,while the wind speed in most areas is below 1.0m/s and the CO2 concentration is up to more than 900ppm.(2)It can be known from the numerical simulation research on the growing pig house that the position of the wet curtain has a great influence on the flow field,leading to a vortex area in some pig pen areas.At the same time,it was also found that the temperature field in the house has obvious stratification in height.The wet curtain airflow flows in the upper space of the pig house,and only part of the air flow can sink to the pig activity area,which results in low ventilation efficiency,difficult temperature regulation and poor air quality.(3)The air distribution form of the growing pig house was optimized under the air supply volume and air supply parameters remained unchanged.Before carried out the numerically simulation,taking the top air supply layout and the proportion of the leaky floor as the optimization parameters then formulating the optimization scheme.The optimized air supply outlet made the air flow from the top to the lower space,which not only improved the cooling effect,but also increased the air flowing in the lower part.After the average temperature,average wind speed,CO2 average concentration and non-uniformity coefficient before and after optimization were compared,the best air distribution form is determined.Under the best air distribution form,the average temperature in the pig activity area decreased by 1.14℃,the average wind speed increased by 0.04m/s,the CO2 average concentration decreasaed by 190ppm.(4)Under the best air distribution form,the air supply parameters of growing pig house were optimized.By setting different air supply temperature and air supply speed,the optimization scheme was put forward and simulated.It was found that when the air supply temperature was 21.0℃ and the air supply speed was 3.5m/s,the average temperature was 22.72℃ and the average air speed was 0.79m/s,the CO2 average concentration was 674ppm,and the growing environment of pigs was obviously improved.(5)In the case of keeping the same air supply parameters,the round air outlet vertical air supply and the square diffuser air supply were compared,and it was found that the optimization effect of the diffuser air supply on the temperature was better than that of the round mouth vertical air supply,and the average wind speed in the pig activity area gradually decreased with the increase of the supply air angle,but the uniformity of the wind speed distribution was improved.