CFD Simulation And Effect Test Analysis Of Thermal Environment In Summer And Winter In The Stepped Cage Brooding Chicken House

The consumption of poultry eggs has increased year by year with the rapid development of China’s economy.The number of large-scale poultry farms has increased sharply in order to meet the market demand.In order to save costs and avoid risks such as cross-infection of chickens,a separate breeding model of laying hen farms and brooding chicken farms has been formed.Chickens have higher requirements on the growing environment.The hot water radiating fan heating system is adopted by the brooding chicken house in order to comprehensively control the heating and ventilation of the whole house.In summer,the wet curtain-fan ventilation system is usually used for cooling.However,the opening angle of the hot water radiating fan shutters is mostly determined by experience,and there are few studies on the heating air inlet angle and its influence on the heating effect in the house.At present,the research objects are mostly adult chicken houses and less for brooding chicken houses in the research on the wet curtain cooling system of the chicken house in summer.In this study,a stepped cage brooding chicken house in Wenxian County,Henan Province was used as the research object.The model was established by field measurements,and the accuracy of the model was verified by comparing the field measurements with CFD simulation results.The effects of the heating air inlet angle of the hot water radiating fan and the opening angle of the wet curtain air outlet deflector on the airflow velocity,temperature and relative humidity in the brooding chicken house were evaluated and optimized.On the basis of this,effect tests were conducted to analyze the effects of the heating air inlet angle and wet curtain deflector opening angle on the growth performance,behavior,mental and health conditions of chickens.The main findings of the study are as follows:1)In this study,a three-dimensional model of the brooding chicken house was established and numerically simulated through actual measurements.In winter,when the air inlet angle of the hot water radiating fan was 45°,the average relative errors of wind speed and temperature measurement points were 15.9% and 1.5%,respectively,and the root mean square error RMSE was 0.08 m/s and 0.49 ℃,respectively.In summer,when the opening angle of the wet curtain air outlet deflector is 30°,the average relative errors of wind speed,temperature and relative humidity were 18.7%,1.1% and 4.0%,respectively,and the root mean square error RMSE was 0.29 m/s,0.32 ℃ and 3.30%,respectively.The simulated and measured values are in good agreement and the model is valid.2)As the heating air inlet angle increases,the main findings are as follows: The airflow uniformity among the three rows of cages increased.The airflow velocity in the lower cages(Z<0.55 m)was more influenced by the heating air inlet angle,while the upper cages(Z>0.55 m)were less influenced by the heating air inlet angle.The temperature distribution was more uniform along the height direction and among the rows of cages when the heating air inlet angle was 45°.After adjusting the air inlet angle to 45°,the final body weight of chickens increased by 5.3% and the average feed conversion ratio decreased by 3.9% compared with the control group(37.5°)after four test weeks.Within three weeks,the chickens’ fear of new objects and their listlessness condition improved compared with the control group,but there were no significant difference in their eating and drinking behaviors.3)As the opening angle of the wet curtain air outlet deflector increases,the main findings are as follows: The airflow velocity inside the cage increased,and the uniformity of airflow distribution between three rows of cages decreased.The maximum average temperature difference between three rows of cages decreased from0.45 ℃ to 0.25 ℃,and the maximum temperature difference inside a single row of cages decreased from 2.47 ℃ to 1.6 ℃,which indicated the temperature uniformity was improved.The uniformity of relative humidity distribution among the three rows of cages improved.The airflow,temperature and relative humidity distribution inside and outside the cages were more uniform when the opening angle of the deflector was 45°.The results showed that the temperature and humidity index THI<79,and the effective temperature ET<26.75,which was suitable for the growth of chicks.After adjusting the opening angle of the wet curtain air outlet deflector to 45°,the final body weight of chickens increased by 3.3% and the average feed conversion ratio decreased by 3.4%compared with the control group(30°)after four test weeks.The experimental group(45°)chickens had better eating and drinking performance than the control group during the experimental period,but there were no difference in their mental and health condition.