Evaluating the intermittent ventilation of summer poultry house in Northwest China

Heat stress has posed a significant threat to the laying hens inside the poultry houses in the Northwest region of China. Significant non-uniformities can be found in the thermal distribution and temperature variations in summer. The ventilation system has been the primary measure to regulate the thermal environment in the poultry houses. Excellent airflow arrangement and ventilation strategies are essential for the ventilation efficiency. Still, the continuous operation of fans can inevitably generate the excessive local cold air, thereby wasting the electrical energy for the high cost of environmental control. Alternatively, intermittent ventilation can serve as an efficient way to improve ventilation effectiveness with energy saving. However, it is notably limited to applying to the summer poultry houses so far. In this study, a novel intermittent ventilation was introduced to alleviate the significant temperature fluctuations and ensure the high stability of the thermal environment in the summer poultry houses. According to the internal air temperature, the fan operations were performed on the conventional tunnel-ventilated poultry houses (control house, CH) and sidewall inlets poultry houses (experimental house, EH). Specifically, the fans were regulated, when the temperature exceeded the upper limit. Once the temperature dropped below the lower limit temperature, the fans were deactivated simultaneously, which was different from the continuous operations of fans throughout the summer. The thermal environment was monitored in the operation periods of intermittent ventilation. The environmental conditions inside the poultry houses were also evaluated. The results revealed that the average internal temperatures of experimental and control poultry houses were 25.3 and 26.5 °C, respectively, under the same external environmental temperatures; While the average relative humidity were 65.8% and 62.7%, respectively. The temperature fluctuations during the EH and CH's intermittent and continuous ventilation were 0.6 and 0.7 °C, 1.2 and 1.0 °C, respectively. The maximal difference of temperature in the horizontal direction of EH and CH were 0.3 and 5.2, 0.8 and 4.7 °C, respectively. Temperature variations were assessed in the four-hour intervals. The EH consistently demonstrated more minor temperature fluctuations than the CH when the fans were operated intermittently. The horizontal temperature difference was less than that in the continuous operation in EH. There was no difference in pressure and air velocity under the intermittent and continuous ventilation in the same number of fans. The pressure difference between the interior and the evaporative cooling pad buffer room increased from 17 to 19 Pa from the fan opposite wall to the fan. Average air velocity at the sidewall inlets and along the aisles in the EH were 3.30 and 0.49 m/s, respectively, which were higher by 1.86 and 0.12 m/s, compared with the CH. Therefore, the intermittent ventilation was suitable for the sidewall inlets, to improve the thermal environment within the poultry house significantly. There was great potential for widespread adoption in the Northwest region of China in the summer. The lifespan of the fan was extended for the maximal economic benefits. The intermittent operation times of fans should be determined according to the local climate, poultry houses’ ventilation requirements and the poultry houses’ size. This finding can provide a foundational reference for designing and adjusting the intermittent ventilation in summer poultry houses in the Northwest region of China.