Fan Airflow Rate Research Articles

2階機械給排気方式及び床下給気方式についての実験と数値計算 : 住宅用ハイブリッド換気システムの性能評価に関する研究 その2

For the purpose of complementing the lack of ventilation airflow rate on the 2nd floor, the mechanical supply for the 2nd floor with passive exhaust system and the crawl space supply with hybrid exhaust system were suggested. Experiments and long-term numerical analysis were carried out for evaluating the system performance. As the results, the followings are reported; About the forth system, airflow rate of mechanical supply showed close connection to the balance of ventilation airflow rate. High building air-tightness and large amount of fan airflow rate for the 2nd floor are desirable for cold climate area especially. In the case of crawl space supply with hybrid exhaust system, good balance of ventilation airflow rate was obtained by adjusting the air inlet opening area on the 1st floor and the crawl space temperature. According to the calculation result for hybrid ventilation system, no correlation was shown with regional climate differences. It was found that airtight building needed larger air inlet opening area on the 1st floor for the balance of ventilation airflow rate.

Hydrogen sulphide emission from two large pig-finishing buildings with long-term high-frequency measurements

Hydrogen sulphide (H2S) is a common toxic air pollutant and is emitted from decomposing manure at animal facilities. However, there have been only a few studies of H2S emissions from animal buildings, especially those involving long-term, high-frequency measurements. In the current study, H2S emissions from two, 1000-head pig-finishing buildings in Illinois, USA, were monitored with a high-frequency measurement system for 6 months in 1997 during two, partial, pig-growth cycles. Air sample streams were continuously taken from the pit headspace, and the pit and wall fan exhaust air. Hydrogen sulphide concentration was measured at each location with H2S converters and sulphur dioxide (SO2) analysers during 16 or 24 sampling cycles per day, resulting in 4544 sampling cycles and 219 days of reliable data. Building ventilation rate was the summation of pit fan and wall fan airflow rates. Airflow rates of the underfloor manure pit fans were measured directly with full-size impeller anemometers or calculated from airflow/voltage relationships of the fans. Airflow rates of the wall fans were calculated from fan operation and differential static pressure data and fan performance curves. Mean H2S emission was 0·59 kg/day per building, 0·74 g/day per m2 of pit surface area, or 6·3 g/day per animal unit (AU = 500 kg animal weight). The determination of H2S emission per AU was restricted to 193 days when building occupancy was at least 700 pigs per building. Higher temperatures and building ventilation rates resulted in significantly higher H2S emissions per AU.

EFFECT OF A MANURE ADDITIVE ON AMMONIA EMISSION FROM SWINE FINISHING BUILDINGS

The effect of a commercial manure additive (Alliance®) on ammonia (NH 3 ) emissions was evaluated in commercial 1000-head grow-finish swine buildings over a six-month period. The test was conducted in two treated and two control buildings at a modern swine-finishing site consisting of nine identical buildings. Automatic spray application systems in the treated buildings intermittently sprayed the additive onto the surfaces of the below-floor manure storages. Ammonia concentrations were measured with a chemiluminescence analyzer at three location groups in each building over 7 or 12 min periods every 1.0 to 1.5 h. Pit fan airflow rates were measured continuously with impeller anemometers. Wall fan airflow rates were calculated from fan pressure/airflow curves and measured static differential pressure between indoor and outdoor air. Nearly 7,000 data subsets from 332 building-days of testing were obtained for comparing NH 3 emission rates between control and treated buildings. The mean NH 3 emission rate per AU (animal unit or 500 kg live weight) from the treated buildings (96.4 g/day·AU) was 24% (P < 0.05) lower than the control buildings. The volume of additive solution was sufficient to dilute the fresh manure by 20%, but the effect of dilution only on NH 3 emission was not measured.

EVALUATION OF A FREELY ROTATING IMPELLER TO MEASURE FAN AIRFLOW RATES IN LIVESTOCK BUILDINGS

This study was conducted to develop and evaluate a method to continuously measure fan airflow rates inlivestock buildings. The method involved measurement of the rotational speed of a freely rotating impeller, which wasinstalled upstream or downstream of the exhaust fan. Laboratory tests showed a linear relationship between impellerrotational speed and fan airflow rate (R2 = 0.99; p < 0.05). The upstream position with respect to the fan provided betterperformance than the downstream position. For the axial fans tested with this setup and at a fan static pressure of 25 Pa,the absolute deviations of predicted from measured values ranged from 36 to 78 m3/h. Additionally, this setup had onlyslight effects on the performance of the smaller fans (30 and 41 cm). This study demonstrated the potential of this methodfor continuous measurement of fan airflow rates in livestock buildings.

DEVELOPMENT OF A LARGE PADDLE FAN FOR COOLING POULTRY

A 2.5 m (8.2 ft) diameter paddle fan was developed for cooling floor-raised poultry. An experimental prototype with plywood blades was used to determine effects of blade pitch angle and rotational speed on fan power and air velocities near the floor. Prediction equations were obtained for the area-averaged velocity 25 cm (10 in.) above the floor, over an 11 × 17 m (35 × 55 ft) area below the fan. Energy efficiency was defined as the ratio of area-averaged velocity to the power consumption. A fan speed of 150 rpm and blade pitch angle of 15° were determined in order to produce area-averaged velocity of 1.2 m/s (240 ft/min) at maximum energy efficiency. Two commercial prototypes were then developed using gearmotors, hubs made from formed steel plates, and plywood or fiberglass blades. Based on velocity traverses below the fan blades, the fan airflow rate was 12 m3/s (25,000 cfm) for both types of blades, and the conventional energy efficiency (ratio of airflow rate to fan power) was 0.036 and 0.046 m3/(s-watt) (76 and 97 cfm/watt) for the plywood and fiberglass blades, respectively. Area-averaged velocity 25 cm (10 in.) above the floor was 1.11 and 1.23 m/s (218 and 242 ft/min) for the plywood and fiberglass blades, respectively. The fans produced desirable air velocities in turkey and broiler houses in summer conditions without problematic bird crowding behavior.

Field Measurements of Fan Speed and Power Use in Poultry Houses

Fans are essential for effective air mixing and ventilation in poultry housing. Although performance data useful in selecting or comparing fans can be measured by qualified testing services, onsite measurements of fan speed and power use are also useful in evaluating operation of a given fan. In order to assess variation in fan operation, fan speed and power consumption were measured on thirty-five poultry farms in North Carolina. Both belt and direct drive fans up to 5 yr in age ran at nearly rated speeds. As fan age increased, variability in fan speeds of older fans increased due to factors such as variation in fan maintenance and fan and motor quality. Belt wear alone reduced the speed of one fan by over 20%, even though the worn belt appeared to have the proper tension. Since fan airflow rate is proportional to fan speed, the timely replacement of fan belts is essential and measurement of fan speed may be necessary to diagnose ventilation problems. The fans consumed considerably more power than their nominal power rating, so appropriate adjustments must be made to predict fan energy costs accurately.