定点送风降温对母猪周围温度和对流换热的影响

Effects of fixed-point air supply cooling system on airflow and temperature around sows and convective heat transfer of sows

为了满足高温高湿地区或密闭性较差的哺乳猪舍的降温需求,该研究基于计算流体力学(Computational Fluid Dynamics,CFD)数值模拟技术,研究了正压定点送风降温方式下不同进风口直径、进风风速和进风温度对哺乳母猪周围气流场、温度场以及机体对流换热量的影响。结果表明:当进风温度为25~27℃、进风风速为4~8 m/s、进风口直径为8和12 cm时,母猪周围大部分区域风速低于0.5 m/s、温度高于27℃。在相同进风风速和进风温度条件下,进风口直径为12和16 cm的母猪对流换热量高于进风口直径为8 cm的母猪对流换热量。考虑到母猪周围风速和温度的分布以及母猪散热的情况,当进风口直径为12 cm时,既能保证母猪周围区域风速、温度能满足哺乳仔猪的需求,又能保证母猪有较高的对流散热量,推荐在实际生产中使用该尺寸的进风风口。该研究通过CFD模拟分析了定点送风降温方式中相关参数对仔猪活动的产床区域风速和温度分布及母猪对流换热量的影响,为该降温方式在哺乳母猪舍的应用提供理论依据。

Ventilation and cooling have been highly required in large-scale lactating pig houses,particularly in areas of high temperature and high humidity.This study aims to evaluate the effects of different inlet diameters,air speed,and temperature on the airflow and temperature field around lactating sows,as well as the heat dissipation of lactating sows under the fixed-point air supply cooling system using computational fluid dynamics(CFD)numerical simulation.The length,width,and height of the pig house were set as 2.5,1.8,and 6 m,respectively,all the same as the experimental and simulation.The temperature and humidity at six points were measured on Z=0.53 m plane.The results showed that the air speed of each measuring point after the second point was less than 0.5 m/s at the different inlet air speeds when the air inlet temperature was constant and the inlet diameter was 8 cm.The air speed of each measuring point after the fourth point was less than 0.5 m/s when the inlet diameter was 12 cm and the inlet air speed was 6 m/s.The air speed of the sixth measuring point was less than 0.5 m/s when the inlet diameter was 16 cm and the inlet air speed was 4 m/s.There was about a 1.7℃temperature difference between each measuring point under the conditions of the same inlet air temperature and different inlet diameters.The average temperature of the second to sixth measuring points corresponding to the three air inlet diameters was lower than 27℃,when the inlet air temperature was 23℃.There was about a 1.8℃temperature difference between each measuring point,under the conditions of the same inlet diameter and different inlet air temperatures.The average temperature of the second to sixth measuring points was lower than 27℃when the inlet diameter was 16 cm and the inlet air temperatures were 23℃and 25℃.The convective heat-transfer coefficient of sows significantly increased with the increase of inlet diameter and inlet air speed,whereas,there was no significant effect from the inlet temperature.Once the diameter of the air inlet was 12 cm,the air speed and temperature in the area around the sows had fully met the needs of suckling piglets,where the sows behaved the high convective heat dissipation.Therefore,the air inlet of 12 cm was recommended in this case for the actual production.Specifically,the inlet air speed increased by 1 m/s,and the convective heat transfer of sows increased by 28.76 W,where the inlet diameter was 12 cm and the inlet temperature was 25℃.Furthermore,the inlet air temperature decreased by 1℃,and the convective heat transfer of sows increased by 16.61W,where the inlet diameter was 12 cm and the inlet air speed was 6 m/s.Therefore,the fixed-point air supply cooling system posed a great impact on the air speed and temperature distribution in the activity area of piglets,together with the convective heat transfer of sows.The finding can provide the theoretical basis for the cooling mode in the lactating sow houses.