Impact of tunnel ventilation on thermal environment in solar heated swine housing

Abstract: In order to control the ground temperature and relative humidity inside pigpens, the solar piggery with tunnel ventilation was adopted in this study. Pigs usually lay down for more than 70% of the time. The environmental control, especially the temperature control at where they lie down (e.g. floor, bed) is crucial in improving the pigs' performance. This study took the piggery as the research object, using additional solar radiation for the pig beds between the sun and piggery in Changchun. Information on major structures of both the experimental piggery and the control is listed below. The dimensions are 61 m in length, 8.1 m in width, and 3.42 m in height, and the orientation is facing south. The difference between the experimental piggery and the control is that the experimental piggery is mainly divided into two parts, the extra sunspace and itself, which is separated by a common wall. The common wall is a solid wall with a ventilation window and it is covered with an insulating layer during cold seasons. The extra sunspace is arch-shaped, constructed with lightweight steel, and also is covered with an insulating layer during cold seasons. In the experimental piggery, there are 28 units under the pig beds. Each unit 3 500 mm long and 1 970 mm wide and also has its own independent air intake, outlet, and closed airflow tunnel. The positive pressure ventilation axial airflow fan is installed at the air intake in the experimental piggery. The negative pressure ventilation draught fan is fixed at the air outlet. The floor in the control piggery is composed of a cement mortar slope layer, soil compaction, and cement mortar layer. Both experimental barn and control barn housed 275 growing-finishing pigs with mean initial live weight of 28.7?2.2 kg. The pigs were in the growing and fattening stage. With respect to the manner of the tunnel ventilation in the solar piggery, the positive and negative pressure ventilations as well as the fan working at different conditions was applied in experiments. During winter, with temperature about -13℃, the average air temperature inside the piggery was 3.0℃, which was higher than that in the control pig house, while the relative humidity was reduced by 4%, on average. On the floor 2 m away from the air inlet of the experimental house, the average daytime temperature using axial fans was higher than that with natural ventilation and using induced draft fans by 0.7℃ and 1.5℃, respectively, while the corresponding nighttime temperature was higher by 1.1℃ and 2.9℃, on average. On the floor 1 m away from the air inlet of the experimental house, the average daytime temperature using axial fans was higher than with natural ventilation and using induced draft fans by 3.6℃ and 3.8℃, respectively, while the corresponding nighttime temperature was higher by 6.4℃ and 6.9℃, on average. It can be concluded that using a tunnel ventilation system combined with solar energy utilization can greatly increase the floor temperature and decrease the indoor relative humidity simultaneously in the pig house.