FAN AND VENTILATION RATE MONITORING OF CAGE-FREE LAYER HOUSES IN CALIFORNIA

摘要

Ventilation rates were continuously monitored from 1 March 2012 to 13 May 2013 in two cage-free layer houses in California. The average number of brown Lohmann laying hens in each house was 33,300. Temperature, relative humidity, static pressure, and running status of 48 ventilation fans were continuously monitored and recorded every minute. Regression models were developed to relate house temperature and ventilation rate to inlet air temperature and to relate airflow rate to building static pressure (R-2 = 0.98). Results showed that the daily mean ventilation rate per hen ranged from 1.91 to 8.72 m(3) h(-1) hen(-1), averaging 4.49 +/- 1.53 m(3) h(-1) hen(-1). The standard uncertainty of daily mean ventilation rate was determined to be 3.7%. The 91 cm and 130 cm fans were found to perform at 82% and 63% of the manufacturer-rated airflow rates, respectively. Minimum and maximum static pressures were 11.0 and 50.6 Pa, respectively, corresponding to 2 and 16 running tunnel fans. When the house temperature exceeded 30 degrees C, an evaporative cooling system was activated, which could reduce the inlet air temperature by 6.3 degrees C and concurrently increased the indoor air humidity ratio by 3.4 g per kg dry air. Cooling pad efficiency was 66%. The sidewall fans and tunnel fans were operated at 65% and 20%, respectively, of the total time when layers occupied the houses. A new rational formula for calculating dry base ventilation rate was developed based on the ratio of water vapor volume to moist air volume. The developed models and data collected in this research can be used to calculate the ventilation rates in cage-free layer houses to ensure the healthy conditions needed for laying hens. The models and data can also be used in the design of cage-free houses and in calculating emissions of air pollutants from these houses.