Assessment And Optimization On The Environment Of Laving Hen House In Autumn Based On CFD

The environment inside a laying hen house includes the thermal environment and the air quality.The quality of the environment directly relates to the health and welfare of laying hens and affects egg production and egg quality.Ventilation is an important method to regulate the environment in livestock and poultry houses,because it can efficiently improve the environment in livestock and poultry houses.However,current research on the ventilation system of livestock and poultry houses mainly focuses on the ventilation strategies in summer and winter,with limited research on the ventilation strategies in spring and autumn.Therefore,this study aims to evaluate the indoor environmental quality of a typical laying hen house in autumntime（the autumn ventilation strategy）using computational fluid dynamics（CFD）technology.Hopefully,the results and conclusions could provide a reference for the improvement of the indoor environment and optimization of the ventilation strategy of laying hen houses in autumntime.The study was based on a typical H-type cage laying hen house,located in Ningbo,Zhejiang Province.The air temperature,relative humidity,air velocity,and particulate matter concentration at different locations in the laying hen house were measured on-site for environmental quality assessment and CFD model validation.The thermal environment distribution in the laying hen house under different ventilation strategies（combinations of 2 and 3 operating fans）was simulated using CFD technology.Thermal index,Effective Temperature in particular,was used to evaluate and analyze the ventilation performance under each ventilation strategy.With the results,the optimal ventilation strategy was proposed accordingly.Additionally,the distributions of PM₁₀ concentration at three different ventilation strategies were also simulated and evaluated.According to the results,the following conclusions can be drawn:（1）Low efficiency in the ventilation and great difference in effective temperature occurred at the laying hen house under the current autumn ventilation strategy.Due to the blockage of the egg collection devices,the majority of the incoming fresh air flowed directly to the exhausting fans through the free space either above the hen cage or in the aisles while limited airflow passing through the lower hen cages.In addition,higher effective temperatures occurred in the middle and rear parts of the first and second layers of hen cages because of the accumulation of heat and moisture along with the airflow from inlet to outlet.（2）The thermal environmental quality inside the laying hen house is related to the position of the operating fan.Changing the operating fans’combination mainly affected the air distribution at the rear of the house.The ventilation strategy（operating fans’combination）used in practice was not the optimal one,according to the comparison of the effective temperature in the animal-occupied zone under the various operating fans’combinations.Alternatively,operating fans close to the sidewall can effectively increase the airflow through the hen cages,thus,the ventilation efficiency and the thermal environmental quality could be improved accordingly.（3）The PM₁₀ concentration in the somatosensory area of the laying hens was unevenly distributed under the practical ventilation strategy.The PM₁₀ concentration in the region of the first-and second-layer of hen cages was higher than that of the third-layer.Besides,the PM₁₀concentration in the rear region of the laying hen house was higher than that in the front.Operating fans close to the sidewall could effectively reduce the PM₁₀ concentration in the somatosensory area of the laying hen from tthe practical ventilation strategy（2.21mg/m³）to 1.93mg/m³ and2.07mg/m³ for the cases with two operating fans in the lower row and one operating fan in each upper and lower row respectively on the same side.