Study on the improvement effect of spray device on the thermal environment of naturally ventilated dairy barn in southern China
The study focuses on the severe heat stress of dairy cows in natural ventilation cowshed in summer in southern China.Using on-site measurements and computational fluid dynamics(CFD)research methods,a comparative analysis was conducted on the the wind speed field and THI field in a natural ventilation cowshed before and after the addition of the spray device under three different external wind directions,wind speeds,temperature and humidity conditions in a natural ventilation cowshed in southern China.The results showed that:1)The relative error range of each measuring point in the temperature field was 0.04％-1.36％,with an average relative error of 0.43％.The relative error range of each measuring point in the relative humidity field was 0.00-7.43％,with an average relative error was 2.22％.After removing the abnormal values,the relative error range of each measuring point in the air flow field was 0.05％-83.68％,with an average relative error of 38.44％.2)Numerical simulation showed that the high wind speed area was mainly concentrated in the feeding aisle and the edge of the cowshed,ranging from 1.4 to 3.0 m/s.The low wind speed area was mainly concentrated in the cow activity area on the east side of the cowshed,with nearly half of the cows having wind speed below 0.4 m/s.The influence of different wind directions on the edge of the cowshed was different.Under northeast and south wind conditions,there was a high wind speed area in the east of the cowshed,while under northwest wind conditions,the airflow field at the edge of the cowshed was relatively uniform.3)After adding a sprinkler system,different external climates can lead to different effects of spraying.When the temperature and humidity were moderate and the wind speed was relatively small,the addition of the spray device will increase the temperature and humidity index by 0.23,which was significant(P＜0.05)and exacerbates the heat stress of dairy cows.When the wind speed was high,high temperature and low humidity,the addition of the spray device will decrease the temperature and humidity index by 0.97,and the difference was significant(P＜0.05).When the wind speed was high,low temperature and high humidity,the addition of the spray device will decrease the temperature and humidity index by 0.19,and the difference was not significant(P＞0.05).In summary,this study simulated the changes in the thermal environment of the cow house and the improvement of the heat stress of the cows in the house by adding the spray device in three different external environments.The results can provide a basis for the design of naturally ventilated dairy cowshed and the regulation of the thermal environment in the dairy cowshed.
CFDnatural ventilationdairy cowshedspraying devicetemperature and humidity index
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