Research On Simulation Of Airflow And Temperature Fields In Non-pregnant Sow House Based On CFD

A good breeding environment is one of the main factors to ensure the healthy growth and production performance of pigs.Due to global warming,the high temperature in summer has made heat stress of sows in actual breeding and production more common,which seriously affects the economic benefits of pig farms.In this study,through field investigation and data measurement,computational fluid dynamics(CFD)simulation technology was used to analyze and evaluate the wind speed and temperature environment in the non-pregnant sow house that uses wet curtain-fan mechanical ventilation in summer.Timely discover and analyze the deficiencies of the current environment in the house,and optimize the design of the target pig house,thereby improving the economic benefits of the pig farm.This paper selects an non-pregnant sow house with wet curtain-fan mechanical ventilation method in Chenzhou City,Hunan Province as the research object,and uses Fluent software to simulate the airflow field and temperature field of the target pig house in a three-dimensional steady state.It aims to provide an effective method for the study of pig house environment simulation,and also provide a theoretical basis for the design and optimization of the pig house ventilation system and structure.The following research results are obtained:(1)On-site inspection,select the target pig house for on-site measurement,establish a three-dimensional model of the pig house based on the measurement data and simulate calculation,and then compare the simulated value with the actual measured value.The results show that the simulated value of the temperature is not much different from the measured value,the maximum relative error is 2.66%,and the NMSE of the temperature at the measuring point is only 0.00034(<0.25);The simulated value of wind speed and the measured value follow a similar law,the maximum relative error is 12.59%,and the NMSE of the wind speed at the measuring point is only 0.0023(<0.25).The results prove that the NMSE of the temperature value and wind speed value at the measuring point are both within the acceptable error value of 0.25,and the simulated value is in good agreement with the measured value.It is feasible to use Fluent software to simulate the airflow field and temperature field of the pig house.(2)Analyzing the environment in the pig house through the simulation results,it is found that there are a large number of airflow dead zones in the pig activity area,and the average wind speed is only 0.32m/s,which is much lower than the comfortable wind speed of 1m/s for non-pregnant sows in summer,which is extremely unfavorable Pig heat dissipation;the temperature of the pig’s active area is relatively high,maintained in the range of 24.3～29℃,61.975% of non-pregnant sows are affected by heat stress.(3)Establish a model and simulate analysis for the target pig house that adopts the new tunnel ventilation and fence type enclosure.The airflow dead zone in the house is reduced,the airflow distribution is more uniform,and the average wind speed in the pig activity area increases by 0.241m/s,the average temperature is reduced by 0.585℃,and the wind speed and temperature environment have been improved.However,there are still 38.75% of empty sows affected by heat stress,and further optimization of the target pig house is required.(4)On the basis of adopting the new tunnel-type ventilation,fence-type enclosure,and without changing the wet curtain-fan mechanical ventilation method,design two optimization schemes,establish models and simulate analysis.In scheme 1,only one partition wall is set in the middle of the dung layer,and in scheme 2,the air outlet is set on the side wall of the dung layer and no partition wall is set on the dung layer.The simulation results of the two scenarios were analyzed,and the following conclusions were drawn: In scenario 1,the wind speed in the pigs’ active area increased by 0.2665m/s and the average temperature decreased by 1.23℃ compared with the original pig house.The area where the non-pregnant sows were affected by heat stress reduced by 48.95%,the wind speed and temperature environment have been improved significantly;in Scheme 2,the wind speed in the pigs’ active area is 0.2425m/s higher than the original pig house,the average temperature is reduced by 1.935℃,and the temperature in the house is lower than the critical heat stress of the non-pregnant sows The value is 26°C.The difference in wind speed improvement effects of the two programs is very small,but program 2 ensures that non-pregnant sows will not be affected by heat stress.The temperature improvement effect of program 2 is significantly better than program 1,so program 2 is better than program 1.