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J APPL POULT RES 2008. 17:283-295. doi:10.3382/japr.2006-00055
© 2008 Poultry Science Association
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Field Reports

On-Farm Ventilation Fan Performance Evaluations and Implications

K. D. Casey*,1, R. S. Gates{dagger}, E. F. Wheeler{ddagger}, H. Xin§, Y. Liang#, A. J. Pescatore|| and M. J. Ford||

* Texas AgriLife Research, Texas A&M System, Amarillo, TX 79106;{dagger} Biosystems and Agricultural Engineering, University of Kentucky, Lexington 40546; {ddagger} Agricultural and Biological Engineering, Pennsylvania State University, University Park 16801; § Agricultural and Biosystems Engineering Department, Iowa State University, Ames 50011; # Biological and Agricultural Engineering, University of Arkansas, Fayetteville 72701; and || Animal and Food Sciences, University of Kentucky, Lexington 40546

1 Corresponding author: kdcasey{at}ag.tamu.edu


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Fans are key components of mechanically ventilated poultry housing. When installed, the fan is often fitted with 1 or more accessories, including safety guards, shutters, and discharge cones. These first 2 accessories usually reduce the airflow and fan efficiency, whereas discharge cones improve airflow. Field performance of a fan is further impacted by accumulated dirt on the blades and shutters, mechanical wear, and degree of maintenance. Performance of all ventilation fans on 2 commercial broiler farms was determined during an air emission monitoring project. Each fan was tested using the Fan Assessment Numeration System at a range of static pressures typical of its regular operating range. The performance of otherwise identical fans was shown to vary by up to 24%. This variation in performance is attributed to accumulated dirt and corrosion, differences in the resistance to flow imposed by the shutters, and differences in motor and bearing wear due to run time and aging. A small reduction in fan speed from slipping or worn belts had a large effect on airflow generated by the 1,220-mm (48 in.) diameter fans. The power consumption of each fan was also measured as part of the evaluation process and revealed considerable variation among these fans.

Key Words: air movement • ventilation system maintenance • poultry housing • energy consumption • broiler • layer


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Ventilation fans are key components of mechanical ventilation systems in confined animal housing facilities for swine, dairy, and poultry. Fans are used to create both airflow and air exchange. The fresh air conveyed by the fans supplies oxygen to the animals and removes heat, moisture, and aerial contaminants from the facility. The amount of air exchange required depends on animal size, stocking density, type, and incoming air temperature.

Fans are usually selected by a designer based on a fan performance characteristic relating air-flow rate at a design resistance against which the fan is operating (i.e., static pressure difference between the air inside and outside of the house). Fans in livestock and poultry houses typically operate at static pressures of 10 to 25 Pa (0.04 to 0.10 in.H2O) [1]. Fans in new, wide poultry houses typically operate at static pressures of 25 to 37 Pa (0.10 to 0.15 in.H2O) to achieve the required air throw requirements. Proper environmental control inside the livestock or poultry house relies on the fan capacity to supply the required volume of air at the static pressure differential chosen for the house as well as properly configured and operated inlets for fresh air distribution. In the United States, inlets are typically controlled by maintaining static pressure with an independent controller. The static pressure differential setpoint is often varied during the year to create airflow patterns within the house to suit the growth stage of the animals and to accommodate incoming air temperature.

During hot weather conditions, broiler houses operate in tunnel ventilation mode, in which air is drawn through evaporative cooling pads at 1 end of the building and exhausted by large capacity fans at the opposite end. Tunnel ventilation systems are typically designed to achieve a velocity of 2.54 to 3.05 m/s (500 to 600 ft/min) over the average cross-sectional area of the house. In tunnel ventilation mode, the fans operate against 2.5 to 30 Pa (0.01 to 0.12 in.H2O) of static pressure, and it is generally recommended to keep static pressure low to maximize airflow rate and velocity.

When installed in an animal house, the fan is fitted with safety guards, shutters, and other accessories, including discharge cones. Guards and shutters reduce the airflow and fan efficiency, whereas discharge cones increase air-flow. These accessories are necessary for the proper functioning of the ventilation systems [2]. Shutters typically reduce airflow and efficiency by 10 to 25%, with the lower value for intake-side shutters and higher value for discharge-side shutters [2]. Guards typically reduce airflow and efficiency by less than 5% [2]. The effect of these accessories may not be included in the fan performance characteristics supplied by the manufacturer or published by independent fan test laboratories.

The field performance of a fan is also influenced by its installation, maintenance, and cleanliness. Researchers have observed that airflow through a 1,220-mm (48-in.) diameter fan was reduced by 2% when it was positioned within 300 mm (12 in.) of another fan [3]. Although fans are equipped with shutters to prevent uncontrolled backflow through fans that are not operating, their presence has been related to airflow reductions of 23 to 39% [4]. The presence of a clean shutter on a 915-mm (36-in.) diameter fan was shown to reduce airflow by 11% [5]; however, accumulated dirt on the shutters can further reduce airflow by up to 40% [2]. In 1 study, a clean broiler house fan was tested at the beginning of a broiler flock and again at the end of the first growout and without cleaning at the end of the subsequent growout. An airflow reduction of 16.3% was observed due to the dirt accumulated on the shutters after 1 broiler flock and 23.5% after 2 flocks [5].

Loose belts are another source of performance loss. Improvements in airflow of 30 to 60% have been measured for fans tested in the field that had their belts adjusted to the proper tension [6]. Researchers have observed that poorly tensioned belts, worn belts, or both could result in substantial reductions in fan performance [6, 7]. In a survey of broiler house fans, it was observed that both belt and direct drive fans up to 5 yr old ran at nearly rated speeds [7]. These researchers concluded that this unchanged fan speed indicated no deterioration in fan performance.

Determining the airflow through a fan under field conditions has always been difficult. However, with the development of the Fan Assessment Numeration System (FANS) by researchers at the USDA-Agricultural Research Service Southern Poultry Research Laboratory [8], and with further refinements by the University of Kentucky [9], in-field determination of fan air-flow has become practical and quite accurate, within 1% [9]. The wider availability of FANS resulting from its use in several emissions measurement projects [10, 11] to determine fan performance characteristics has provided the ability to accurately investigate fan performance under field conditions.

The FANS incorporates a horizontal array of 5 propeller anemometers to perform a real-time traverse airflow entering ventilation fans up to 1,370 mm (54 in.) in diameter. Approximately 1.8 million velocity readings are obtained as the anemometers traverse the flow field in about 180 s. The average velocity is multiplied by the effective cross-sectional area to obtain the mean ventilation rate. Figure 1Go is a photograph of the FANS unit in operation to characterize the performance curve of an exhaust fan at site KY-A.


Figure 1
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  		Figure 1. Testing 1,220-mm (48-in.) diameter fans at site KY-A using the Fan Assessment Numeration System. The 5 anemometers traverse the flow field, acquiring approximately 1.8 million data points in about 180 s. The average velocity is multiplied by the effective cross-sectional area to obtain the mean airflow rate. The system is controlled by the laptop computer in the foreground.

 
This paper’s purpose is to report the results of using FANS for in-field measurement of fan performance at 8 broiler houses on 2 farms and to discuss the potential sources of the observed variation in both fan airflow performance and power consumption.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Building Description
As part of a multistate poultry ammonia emissions project [10], ventilation fans at 2 Kentucky poultry (broiler) farms were monitored, each with 4 houses, for replications of conditions. The farms were under contract to different integrator companies. Dropped triply ceilings with blown-in insulation were used in all houses. Each broiler house was 12.2 x 152.5 m [40 x 500 ft; except house 4 at site KY-A, which was 12.2 x 157.4 m (40 x 516 ft)] and contained a nominal 20,000 or 25,000 birds at 10.75 or 13.44 birds/m2 (1.0 to 0.80 ft2/bird), respectively, depending upon finished bird requirements. The houses at site KY-A were built in 2000 (except house 4, which was built in 1995), whereas those at Site KY-B were constructed in 1997.

At site KY-B, 8 ventilation fans, 1,220 mm (48 in.) in diameter [12], and 6 fans, 915 mm (36 in.) in diameter [13], were in each house. Box inlets were located along both sidewalls and were automatically controlled via cable based on maintenance of setpoint static pressure difference. The ventilation control system at this site used individual thermostats on each fan. Each of the six 915-mm (36-in.) diameter fans was equipped with a 10-min electromechanical cycle timer. These cycle timers were only active on the two 915-mm (36-in.) diameter fans being used for minimum ventilation, which were located in the nonbrood sections at opposite ends of the house, set to either 3 or 5 min on during a 10-min cycle. Details of the 915-mm (36-in.) diameter fans at site KY-B are provided in Table 1Go, and the details of the 1,220-mm (48-in.) diameter fans are provided in Table 2Go.


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  		Table 1. Site KY-B fan details—915-mm (36-in.) diameter fans
 

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  		Table 2. Site KY-B fan details—1,220-mm (48-in.) diameter fans
 
At site KY-A, each house had eight 1,220-mm (48-in.) fans [14] and three 915-mm (36-in.) fans [15]. Box inlets were located along both sidewalls and were automatically controlled based on static pressure difference. The ventilation system at this site was controlled by an electronic controller [16]. A single 1,220-mm (48-in.) fan in a nonbrood section of each house was used for minimum ventilation. Details of the fans at site KY-A are provided in Table 3Go.


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  		Table 3. Site KY-A fan details
 
Because the ammonia emissions project required both the ammonia concentration and the volume of exhaust air to be determined, a motor logger was installed on the power cable to each fan [17, 18]. This logger recorded each time the fan was switched on or off. The amount of time that each fan operated during each batch was determined from these records.

Field Fan Performance Measurements
As a component of the multistate poultry ammonia emissions project [10], the fans in each of the 4 houses at the 2 Kentucky farms were characterized using the FANS unit during the monitoring period. The FANS unit was positioned in front (upstream) of the fan under test and sealed to the wall using duct tape to prevent air from being drawn around the FANS unit. Evaluation of the performance characteristic of a fan at 6 static pressures from free air to approximately 40 Pa (0.16 in.H2O) takes 30 min once the system is set up. It can then take up to 30 min to reposition the FANS unit at the next fan. Thus, a poultry house with 11 to 14 fans could be characterized in 1 d. The method used to set the static pressure with the house during each test varied between the 2 farms, based on the house layout and environmental controller design.

Site KY-B.
At site KY-B, the fans in all 4 houses were characterized over a 4-d period while the houses were empty for the annual litter cleanout. As part of this normal annual maintenance procedure, the poultry grower had removed the fans from the houses and conducted necessary maintenance, thoroughly cleaning them before replacing them in the houses. After the FANS was set into place at a chosen fan, a static pressure was set via the house controller [19], which utilizes a separate, differential pressure indicator/switch [20] and was used to control the inlets. The static pressure needles used to define the maximum and minimum static pressures were set to within about 0.5 mm (0.02 in.) of each other so that static pressure was kept in a very narrow range by the inlet controller. Once the static pressure was stabilized, a FANS traverse was run. Static pressure was varied from free air to approximately 40 Pa (0.16 in.H2O) in 5 steps. The calibration of each house’s differential pressure indicator/switch [20] was checked following the fan measurements with a pressure calibrator [21]. The corrected static pressure readings were used in the development of fan performance characteristics. While each fan test was being conducted, a measurement of the supply voltage, current draw, and power consumption of the fan was made using a power analyzer [22].

Site KY-A.
At site KY-A, the fans were characterized during the 5- to 7-d period between flocks. Due to the critical activities to prepare the house for the next flock that also had to take place during this period, usually only 1 d was available during which FANS testing was possible. As a result of this short time window of house availability, support staff availability, and equipment failure, typically the fans in only 1 house could be evaluated after each flock. Hence, these evaluations took place over a period of about 9 mo, and the procedure used evolved as experience with the FANS unit and the operating characteristics of the houses was gained.

Static pressure was varied from free air to approximately 40 Pa (0.16 in.H2O) in 5 steps. With the test fan operating, the number of fully open inlets and the number of other operating fans was varied to achieve the desired static pressure. The static pressure was monitored using a recently calibrated digital manometer [23], and an average static pressure for each run was manually recorded. In the case of houses 2 and 4, the output from a differential pressure transducer [24] was also recorded by a datalogger [25] once per second. The average was computed for each FANS run from the logged static pressure recordings. As per the standard between-flock maintenance procedure, fans were cleaned, usually with compressed air, and then tested. While each fan test was being conducted in houses 2 and 4, a measurement of the supply voltage, current draw, and power consumption of the fan was made using a power analyzer [22]. In houses 1, 2, and 4, the fan speed was measured during each FANS run using a noncontact digital tachometer [26].


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Results of the field evaluation for fan airflow performance and power consumption are summarized by fan size for the 2 sites in the following paragraphs. Fan performance results are provided in Figures 2Go to 6GoGoGoGo. Fan performance and energy efficiency results are provided in Table 4Go. Results from testing fans at site KY-A are limited to house 4, because the testing protocol used in this house most closely followed that used at site KY-B. The other 3 houses at KY-A were evaluated earlier in the project following an evolving testing protocol; data were not collected in a way, or with elements, consistent with the test procedure reported here.


Figure 2
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  		Figure 2. Fan performance characteristics—site KY-B, houses 1 and 2 (H1 and H2, respectively), 1,220-mm diameter fans.

 

Figure 3
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  		Figure 3. Fan performance characteristics—site KY-B, houses 3 and 4 (H3 and H4, respectively), 1,220-mm diameter fans.

 

Figure 4
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  		Figure 4. Fan performance characteristic—site KY-A, house 4, 1,220-mm diameter fans.

 

Figure 5
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  		Figure 5. Fan performance characteristics—site KY-B, houses 1 and 2 (H1 and H2, respectively), 915-mm diameter fans.

 

Figure 6
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  		Figure 6. Fan performance characteristics—site KY-B, houses 3 and 4 (H3 and H4, respectively), 915-mm diameter fans.

 

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  		Table 4. Fan energy consumption (W) and energy efficiency (m3/h per W; cfm/W) for all fans in site KY-B
 
1,220-mm Diameter Fans
The fan performance characteristics for the 1,220-mm (48-in.) diameter fans in houses 1 and 2 and 3 and 4 at site KY-B and house 4 at site KY-A are shown in Figures 2Go, 3Go, and 4Go, respectively. In the 4 houses at site KY-B, the best-performing fan moved 28,000 m3/h (16,480 cfm), whereas the worst performer moved 21,500 m3/h (12,654 cfm), a difference of 6,500 m3/h (3,826 cfm) or 23%. The difference in best performance between fans at the 2 sites (9,000 m3/h or 5,297 cfm) is primarily attributed to difference in fan models. At a static pressure of 15 Pa (0.06 in.H2O), the best-performing fan at KY-A moved 37,000 m3/h (21,777 cfm), and the worst performer moved 31,500 m3/h (18,540 cfm), a difference of 5,500 m3/h (3,0237 cfm) or 15%.

A fan performance characteristic was also obtained from the fan manufacturer [27] for site KY-B. This fan performance characteristic is also plotted in Figures 3Go and 4Go (called manufacturer-supplied performance characteristic) and is reasonably close to the mean of the set of fans tested at site KY-B. For example, at a static pressure of 15 Pa (0.06 in.H2O), the manufacturer’s fan performance characteristic indicates that these fans should be moving 24,500 m3/h (14,420 cfm). This is about 12% more (3,000 m3/h, 1,766 cfm) than the worst-performing fan and 14% less (3,500 m3/h, 2,060 cfm) less than the best-performing fan. A fan performance characteristic was requested from the manufacturer of site KY-A 1,220-mm fans [28], but they indicated that this fan was now obsolete and instead provided a fan performance characteristic that they stated best described the fan model installed. This characteristic (called manufacturer-supplied performance characteristic) is also shown in Figure 4Go. At a static pressure of 15 Pa (0.06 in.H2O), the manufacturer-supplied fan performance characteristic indicates that a fan should be moving 40,000 m3/h (23,543 cfm), which was 8,500 m3/h (5,003 cfm) or 21% more than the worst-performing fan and 3,000 m3/h (1,766 cfm) or 8% more than the best-performing fan.

At KY-B, fans in houses 1 and 2 had aluminum shutters (Figure 2Go), whereas fans in houses 3 and 4 had plastic shutters (Figure 3Go). This may explain some of the performance difference between fans at this site. The average airflow rate of all 1,220 mm (48 in.) in each house at 3 nominal static pressures is presented in Table 5Go. The performance of those fans equipped with plastic shutters was consistently better than those with aluminum shutters with the performance differential increasing at higher static pressures. Fans fitted with plastic shutters moved 6.0, 10.3, and 13.3% more air than their aluminum shutter equipped equivalents at nominal static pressures of 0, 22, and 37 Pa, respectively.


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  		Table 5. Average fan performance by house at site KY-B1
 
Because the KY-B fans were a direct drive design with no belts to wear or lose their tension, the difference in performance among otherwise identical fans may be attributed to differences in wear due to run time and age and difference in the resistance to flow imposed by the shutters. The line voltage was monitored during the performance evaluations and averaged 240 V (range 236 to 245 V). Thus, variations in supply voltage during the evaluation do not explain the performance differences observed among fans.

Also shown in Figure 4Go are concurrent fan speed measurements for each belt-drive 1,220-mm fan at site KY-A during the fan characterization procedure. It is interesting to note that while the static pressure was increased from free air to more than 35 Pa (0.14 in.H2O) and the airflow rate was reduced by 19% (7,000 to 10,000 m3/h; 4,120 to 5,886 cfm), the rotational speed of the individual fan varied from unchanged to a reduction of only 3 rpm (0.5%). The fan with the lowest speed was also the fan with the poorest performance, although no physical characteristics were noted to explain why. However, this fan was utilized as the minimum ventilation fan and hence had experienced the most operational hours. Curiously, the fan with the best airflow performance was not the fan with the highest fan speed. Based on other reported field research, fan belt replacement, retensioning, or both, can restore fan performance to near the specifications of the manufacturer [6].

Because changes in fan speed and airflow rate are proportional by the fan laws, other investigations have concluded that fans in their survey had not deteriorated significantly after up to 5 yr of use, because speed had reduced less than 4% during this time [7]. It can be seen from the results of the research on the 8 fans reported here that over a small range of only 10 rpm (1.7%) between fans, airflow rate at free air was reduced 12.8% from approximately 39,000 down to 34,000 m3/h (22,955 to 20,012 cfm; 12.8%). Thus, it would seem that at least for some fans, speed uniformity by itself is not a good indicator of fan airflow performance.

Site KY-B: 915-mm Diameter Fans
The fan performance characteristics for the 915-mm (36-in.) diameter fans in houses 1 to 4 at site KY-B are shown in Figures 5Go and 6Go. There was considerable variation in performance among these 56 fans. At a static pressure of 15 Pa (0.06 in.H2O), the best-performing fan moved 17,000 m3/h (10,005 cfm), whereas the worst performer moved 13,000 m3/h (7,652 cfm), a difference of 4,000 m3/h (2,354 cfm), or 24%.

The fan performance characteristic of the manufacturer is also plotted in Figures 5Go and 6Go (called manufacturer-supplied performance characteristic) [27] and indicates that at a static pressure of 15 Pa (0.06 in.H2O), the fan should be moving 14,500 m3/h (8,534 cfm). Measured airflow rates ranged from 1,500 m3/h (883 cfm; 10%) more than the worst-performing fan to 2,500 m3/h (1,471 cfm; 17%) less than the best-performing fan tested. Some of the performance difference among fans may be explained by the fact that houses 3 and 4 had plastic shutters, whereas houses 1 and 2 had aluminum shutters. The average airflow rate of all 915 mm (36 in.) in each house at 3 nominal static pressures is presented in Table 5Go. The performance of those fans equipped with plastic shutters was consistently better than those with aluminum shutters, with the performance differential increasing at higher static pressures. At a nominal static pressure of 22 Pa (0.09 in.H2O), fans fitted with plastic shutters moved 1,590 m3/h (936 cfm) or 6.7% more air than their aluminum shutter-equipped equivalents.

Although the fans were purchased together, examination revealed 2 different blade styles (Table 1Go) and a number of different motors (perhaps indicating a motor replacement due to failure). All of these fans were direct drive with no belts to wear or lose their tension. Differences in wear due to run time and age, and difference in the resistance to flow imposed by the shutters, may have contributed to the difference in performance observed among these fans, although this was not established conclusively as the reason for the +10 to –17% difference from manufacturer specifications. On average, the curve of the manufacturer was a reasonable estimate of fan performance (i.e., it falls in the middle of the measured fan performance characteristics).

Fan Power Consumption and Energy Efficiency
Fan power consumption and energy efficiency of the 1,220- and 915-mm (48-and 36-in.) diameter fans at site KY-B are given in Table 4Go. Similar to airflow rate, the power consumption exhibited considerable variation within each size classification. In general, the fans were evenly scattered between the best and worst performers for the 1,220-mm (48-in.) fans. Comparison of the fans’ airflow performance characteristics with their power consumption performance characteristic did not reveal a correlation.

Of considerable interest is the energy efficiency of ventilation fans, typically expressed on a volumetric airflow rate per watt of power consumed, at expected operating static pressure. Values for these fans of the 4 houses at KY-B are provided in Table 4Go for free air and approximately 22 Pa (0.09 in.H2O) and 37 Pa (0.15 in.H2O). Current recommendations for ventilation fans are to select those with efficiencies greater than about 34 m3/h per watt (20 cfm/W) at 25 Pa (0.1 in.H2O) [29]. By contrast, these fans displayed a range of 10.8 m3/h per watt (6.4 cfm/W; fan 1, house 2) to 28.5 m3/h per watt (16.8 cfm/W; fan 11, house 4) with an average of 23.8 m3/h per watt (14.0 cfm/W) and SD of 2.8 m3/h per watt (1.6 cfm/W) at about 22 Pa (0.09 in.H2O). Thus, the fans are not considered energy efficient.

The cumulative operating time for each fan during flock 5 at site KY-B is tabulated in Table 6Go, as a percentage of maximum possible running time. Flock 5 occurred during summer with the fans operating for significant periods during the flock, removing heat from the house and supplying convective cooling to the birds via tunnel ventilation. Not all fans operated for the same period of time, depending upon the stage of the fan. Given the range in energy efficiency noted in Table 6Go and the range in run operating time for fans depending on their use and ventilation stage assignment, perhaps there would be potential to reduce ventilation energy cost by reordering the fan staging such that the most efficient fans in a batch of similar fans were used where the greatest demand for run time existed. However, such a strategy would require full assessment of each fan performance using the FANS or other approach, to assess which fans are most efficient. Whether the energy savings would offset this cost would need to be evaluated.


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  		Table 6. Relative run time for fans during flock 5 at site KY-B
 

   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 
  1. The ventilation performance of otherwise identical fans was shown to vary by up to 24%. This variation in performance was attributed to accumulated dirt and corrosion, difference in the resistance to flow imposed by the shutters, and differences in motor and bearing wear due to run time and aging. Maintenance of proper tension on drive belts and replacement of worn belts was shown to be very important in maintaining fan performance near specification. A small reduction in fan speed from slipping or worn belts had a large effect on airflow through the 1,220-mm (48-in.) diameter fans. It would appear that, at least for some fans, fan speed uniformity by itself is not a good indicator of fan airflow performance. Regular maintenance of the fans, including checking belt tension and replacing worn belts, is very important in ensuring fan performance is maintained close to specification.
  2. Dirty, corroded, or damaged shutters can impose a significant extra resistance that the fan must operate against, thereby reducing its airflow. The reduced resistance to airflow of plastic shutters could be seen in the improved airflow in houses with plastic shutters when compared with those houses that had aluminum shutters. The aluminum shutters presented greater resistance to airflow by design and also being older and had more accumulated dirt, corrosion, and damage, making them harder to operate.
  3. There was considerable variation in power consumption among otherwise identical fans at each of the sites. Although fans with higher power consumption can be readily identified in the field by a service person with a clamp-on electrical power meter, the cost of repositioning the fans may exceed any saving in the short term. Reordering the assignment of fans to stages in which an electronic controller is used has a greater potential to reduce running cost and also to assure more even wear of the fans. Equally important, identifying low-performing fans and replacing them with higher-performance fans appears to be a realistic means of reducing operating expenses. The wide range (10.8 to 28.5 m3/h per watt) in ventilation efficiency ratio and the low mean value of 23.8 m3/h per watt (14.0 cfm/W) is of concern for energy-efficient broiler housing.


   ACKNOWLEDGMENTS
 
This project was supported by Initiative for Future Agriculture and Food Systems Grant no. 20015210311311 from the USDA Cooperative State Research, Education, and Extension Service.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. MWPS. 1990. Mechanical Ventilating Systems for Livestock Housing. MWPS-32. MidWest Plan Serv., Ames, IA.
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  3. Simmons, J. D., B. D. Lott, and T. E. Hannigan. 1998. Minimum distance between ventilation fans in adjacent walls of tunnel-ventilated broiler houses. Appl. Eng. Agric. 14:533–535.
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  6. Janni, K. A., L. D. Jacobson, R. E. Nicolai, B. Hetchler, and V. J. Johnson. 2005. Airflow reduction of large belt-driven exhaust ventilation fans with shutters and loose belts. Pages 245–251 in Proc. 7th Int. Symp. Livest. Environ., Beijing, China. Am. Soc. Agric. Eng., St. Joseph, MI.
  7. Bottcher, R. W., G. R. Baughman, and J. T. Magura. 1996. Field measurements of fan speed and power use in poultry houses. J. Appl. Poult. Res. 5:56–62.[Abstract/Free Full Text]
  8. Simmons, J. D., T. E. Hannigan, and B. D. Lott. 1998. A portable anemometer to determine the output of large in-place ventilation fans. Appl. Eng. Agric. 14:649–653.
  9. Gates, R. S., K. D. Casey, H. Xin, E. F. Wheeler, and J. D. Simmons. 2004. Fan Assessment Numeration System (FANS). Design and calibration specifications. Trans. ASAE. 47:1709–1715.[Web of Science]
  10. Gates, R. S., H. Xin, E. F. Wheeler, S. Scheideler, J. D. Simmons, D. B. Harris, J. Kuhl, A. J. Pescatore, and M. F. Ford. 2001. Reducing ammonia emissions from poultry houses by enhanced manure and diet management. Proposal to USDA-IFAFS competitive grants program.
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