Thermal environmental control of high-rise layer houses in California

Abstract

The ventilation systems of two high-rise layer houses in California were monitored from 10/25/07 to 10/31/09 (m/d/y) for the National Air Emission Monitoring Study to facilitate the calculation of air pollutant emission rates. The ventilation systems, building structural design, feeding systems, and manure management practices of the houses were identical. Each house had approximately 32,500 laying hens in cages on the second floor (layer room) and was mechanically ventilated in cross-flow fashion with 12 sidewall single-speed exhaust fans on the first floor, consisting of two 91 cm fans and ten 122 cm fans. The fan rotational speeds, differential static pressure, temperature, relative humidity, and the evaporative misting system of each house and outside weather variables were continuously monitored. All 24 fans were evaluated with a portable fan tester three times during the two-year test. Fan airflow models were developed from in situ fan test data to calculate the fan airflow rates based on house differential static pressure and fan rotational speeds. The results showed that the fan performance factors of the 91 cm and 122 cm fans were 75% and 84% of the airflows, respectively, of new unused fans. The daily mean dry standard house ventilation rate averaged 47 m(3) s(-1) at dry standard conditions and ranged from 12 to 88 m(3) s(-1). The daily mean hen-specific ventilation rates averaged 5 m(3) h(-1) hen(-1) and ranged from 1.3 to 9.8 m(3) h(-1) hen(-1). Relative uncertainties of the hourly mean hen-specific ventilation rates averaged +/- 4.8% and ranged from +/- 2.9% to +/- 8.8%. The house differential static pressures ranged from -35 to -10 Pa 92% of the time. The layer room temperatures were controlled by adjusting the ventilation rate, which generally increased with ambient temperature. The evaporative misting system decreased the layer room temperature by up to 8 degrees C from the ambient, or barn inlet, air temperature while contributing to an increase of up to 3.8 g kg(-1) in the house humidity ratio relative to barn inlet conditions.