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COMBINED HEAT RECOVERY AND AMMONIA CONTROL SYSTEM FOR

BROILER BROODING

Investigators:

PI: Sanjay Shah, PhD, Professor

NC State University, Raleigh, NC 27695-7625

Phone: (919)515-6753

Email: sanjay_shah@ncsu.edu

Biological and Agricultural Engineering

Co-PI: Edgar O. Oviedo-Rondón, Professor, Prestage Dept. of Poultry Science

Co-PI: Praveen Kolar, PhD, Associate Professor, Biological and Agricultural Engineering Dept.

NORTH CAROLINA STATE UNIVERSITY

Date of Completion: May 31, 2018

Funded by U. S. Poultry & Egg Association

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INDUSTRY SUMMARY

Poultry brooding requires a considerable amount of propane. Propane use is also increased because heating is needed at the floor level and warm air rises to the ceiling resulting in temperature differentials of up to 20°F between the floor and the ceiling. Reducing this temperature stratification by transporting the warm air near the ceiling down to bird-level could reduce energy use. Researchers have reduced temperature stratification using different types of fans. However, using mixing fans to break thermal stratification could transport the lighter-than-air ammonia accumulating near the ceiling down to bird-level. Increased ammonia concentrations can increase susceptibility to many respiratory diseases and reduce performance. Equipping mixing fans with some type of ammonia filter can result in warm, low-ammonia air being recirculated in the house. This could result in reduced energy use, better indoor air quality and improved bird performance. The overall objective of the research project was to design and evaluate a combined heat recovery – ammonia control (HRAC) system. The specific objectives were to select the most cost-effective filter medium, design and build a prototype, and test the prototype in both controlled pen studies and in the field. Several filter materials were evaluated and burlap cloth soaked in 15 percent citric acid was chosen because of its low cost and safety. The pen-scale HRAC units provided modest ammonia reductions and also reduced ammonia concentrations at the floor level. In addition, the pen-scale HRAC reduced thermal stratification in the pens. The full-scale HRAC units provided inconsistent ammonia removal in a commercial broiler house during brooding and did not consistently reduce floor-level ammonia concentrations. This occurred because dust built up on the filters and reduced air circulation through the filtration system. A shaker system was designed and installed on the full-scale HRAC units to shake dust from the filters. The shaker was only partially effective in reducing dust accumulation on the full-scale HRAC unit filters. This study clearly demonstrated that mixing fans can reduce thermal stratification, increasing floor temperature, and may thus, reduce heat energy use, and perhaps, improve bird performance. Coupling an ammonia filtration system to reduce ammonia concentration in the warm air directed down to the birds using the HRAC worked well in controlled pens but did not perform adequately in the field because of dust accumulation on the filters. This research demonstrates that ammonia filtration inside a poultry house may have a practical application. Further research is required to design and test an ammonia filtration system that can operate and be maintained in a dusty commercial poultry house.

SCIENTIFIC REPORT

A. Materials and Methods

Lab-testing: Selection of cost-effective filter medium

Based on literature review, several different types of hydrophobic porous media (polyurethane,

polyester, coated fiberglass) and four types of activated carbon-impregnated filter materials were

considered. Three activated carbon-impregnated polyester filter options were eliminated based on high

cost per unit area and difficulty of use (not available in large sheets or rolls). Several cellulose-based

materials that are inexpensive and readily-available, e.g., burlap (jute), natural cotton batting, and coco

peat (coir) liner were also considered. Pressure drop across each of these materials, at varying

thicknesses, were measured using a system built in our lab.

Since ammonia is mildly-alkaline, the filter material needed to be treated with an acid to improve

ammonia absorption. Several acids, e.g., 5% boric acid (safe and inexpensive), 5% acetic acid (stronger

acid than boric acid, safe and inexpensive), sodium bisulfate, PLT (safe, inexpensive, likely to be on hand

on poultry farm, familiar to producers, effective in controlling ammonia in poultry houses), and 15%

citric acid (inexpensive and safe) were considered. Based on ammonia breakthrough (described in detail

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in our progress report for Jan. – Jun. 2015), cost, and safety issues, burlap was chosen as the filter

medium and citric acid was chosen as the acid medium.

Pen-scale testing: Chicken Testing Unit (CTU), NCSU, Raleigh, NC

The pen study which was not planned, was necessitated because broiler producers refused to give us

access to commercial houses due to concerns about avian influenza in late-2015 and early-2016. The

study involving one flock of broilers was conducted at the NC State University’s CTU in Raleigh during

3 February through 9 March 2016. The room where the study was conducted had 16 pens, eight on each

side separated by 10-ft aisle; the floor was concrete. Fresh air was brought in through sidewall inlets and

the stale air was exhausted through four 18-in fans on the end wall. The pens (8 ft by 10 ft) were framed

with dimension lumber and chicken wire on three sides while the fourth side was a metal wall. There

were two 60,000 Btu/h propane heaters in the aisle. Day-of-hatch chicks were placed on 3 February and

removed on 9 February 2016.

There were two treatments – Test and Control and for each treatment, there were three replications

(pens). For the study, six middle pens on the south side were used; one pen at each end was kept empty.

To isolate the north side pens from the pens used in the study, we lined the entire aisle with plastic sheet

from floor to ceiling and also disconnected the two 18-in fans on the north side. To reduce cost, each pen

was partitioned into two spaces (56 ft2 and 24 ft2) with a 3-ft high screen. On 3 February, 50 female

chicks were placed in the 56 ft2 pen on built-up litter and the remaining space which was adjacent to the

metal wall was kept empty. All the chicks in a pen were weighed before placement. Hence, there were

150 birds per treatment and 300 birds in all. The birds were fed the same diet in both treatments. Feed

consumed in each pen was determined daily by placing a known mass in the feeders and weighing the left

over feed. The birds were given starter diet for the first 14 days and were then switched to grower diet for

the rest of the study.

The pen partition and door were lined with plastic to isolate it from its neighboring pen. Each pen

had an air inlet while the exhaust was an opening in the plastic sheet with a flap about 2 ft above the litter

(Fig. 1). We used an Alnor balometer to confirm that all pens had similar (with ±5%) ventilation rates; to

adjust ventilation rates, we changed the size of the opening. Each pen had two feeders, two waterers, and

two 175-W brooding lamps. The lamps in each pen were controlled by a thermostat and the temperature

was changed weekly; the thermostat sensor hung in the geometric center of the pen, away from the direct

glare of the brooder lamps, at about 12 in. height. Temperature settings on the electric brooders and

propane heaters (in the aisle) were changed weekly. Because it was winter, only one 18-in fan was used

to provide ventilation; the ventilation rate was changed weekly by changing the timer settings.

In each of the three Test pens, we hung a pen-scale HRAC unit at about 9 ft from the litter floor. The

HRAC (Fig. 2) consisted of a 120-V computer fan with its intake covered by a wire mesh sleeve (5 in. by

6 in.); the wire mesh sleeve was covered with two layers of burlap bags soaked in 15% citric acid. Prior

to deployment, airflow rate of the three HRAC units were measured with a balometer; they were all 80

cfm. This airflow rate (80 cfm) was equivalent to 15% of the volume of the pen; the industry

recommends a range of 10 to 15%. The amount of citric acid retained on the burlap bags was based on

stoichiometry, taking into account assumed airflow rate, incoming ammonia concentration, and exhaust

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ammonia concentration (15 ppm). The HRAC moved air parallel to the ceiling from left to right, so that

when the air hit the sidewall, it traveled down along the sidewall at low speed down to the birds. The

HRAC was turned off for 30 min after 5.5 hours of operation.

Each pen had two temperature and RH sensors, at 1 ft above the floor and 9 ft above the floor to see if

there was thermal stratification. Each temperature/RH sensor had its WiFi microcontroller that

transmitted the data to a Raspberry Pi 2 (single board computer); there were two such computers, one for

each treatment. Temperature and RH data were uploaded to the Raspberry Pi 2 every 5 min and could be

accessed using a smart phone or stored on a lap top. In all pens, ammonia concentration at 1 ft above the

floor was measured with acid scrubbers. The acid scrubber drew air from two manifolds that spanned the

entire width of the pen. These scrubbers had a duty cycle of 75% between 3 and 9 February, and 50%

thereafter. In the HRAC, separate acid scrubbers were used to measure ammonia concentrations in the

inlet air as well as in the outlet to allow evaluation of the removal efficiency of the HRAC; along with the

HRAC fan, these inlet and out acid scrubbers were turned off for 30 min after 5.5 hours of operation. All

acid scrubbers using 250 mL of 2% boric acid and their initial and final airflow rates were measured.

Prior to analysis of total ammoniacal N (TAN) in the scrubber solution, the volume of solution remaining

was determined. The acid scrubber was replaced every 2-3 days. Electricity use in each treatment was

measured with a sub-meter.

Day-of-hatch chicks were banded, weighed individually and placed in pens. The chickens were again

weighed at 14 d and at the end of the study (35 d). On both of those days, foot pad dermatitis (FPD),

valgus, and hock burn were evaluated for all the birds in both treatments. Average daily weight gain

(ADWG) and feed conversion ratio (FCR) were also determined. At the end of the study, composited

litter samples from each pen was analyzed for total Kjeldhal N (TKN), TAN, pH, and moisture content.

Commercial-scale testing: Broiler house, Star, NC

Due to reduced concerns about AI outbreak in early-spring 2016, an integrator allowed us access to a

broiler farm in Star, NC, to test a full-scale HRAC during the first week of brooding (March 14-21,

2016). Two adjacent, identical houses were used in the study, Control and Test. The houses were 500 ft

by 40 ft and had a maximum ceiling clearance of 9 ft; 19,000 birds were raised to 9 lb ea. Brooding was

done in the middle-third of the house with brood curtains being placed at both ends of the chamber.

Minimum ventilation was provided by two 36 in fans at opposite ends and fresh air during brooding was

brought in through sidewall inlets. Supplemental heating was provided using propane furnaces. The

houses had built-up litter that were more than a year old. Both houses used in the study had individual

propane meters.

In the Test house, two HRAC units were installed. The HRAC units were built using Aerotech 18 in.

panel fans with a maximum airflow rate of 4,350 cfm. Assuming a pressure drop of 0.25 in, per the fan

curve supplied by Aerotech, each fan could move 3,600 cfm. Hence, for a brood chamber volume of

48,000 ft3, the two HRAC fans could mix 15% air volume per min. As shown in Fig. 3, the fan’s intake

was screened by a triple layer of 15% citric acid treated burlap bags (45 in by 68 in) supported on a

welded wire frame (42 in 22 in 22.5 in). The two HRAC units in the Test house were installed

parallel to the long axis of the house with a net clearance of 7 ft above the litter and 40 ft away from the

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brood curtains at the opposite ends. So, the warm air pulled by the HRAC units were directed against the

brood curtains. In the Control house, there were seven 18-in stir fans (Directaire, 3,500-4,000 cfm ea.)

moving air along the ridge of the house in opposite directions; those fans were operated during the study.

As in the pen scale study, ammonia removal by the HRAC was measured for each unit using an acid

scrubber near the burlap for the inlet air and using a manifold at the fan for the outlet air stream.

Additionally, ammonia concentrations were measured in both the Test and Control houses at three

locations using 5-ft long sampling manifolds. A pressure manifold was placed upstream of the fan inside

the burlap bag with the holes facing the fan; this manifold was connected to a differential pressure sensor

to detected changes in airflow rate over time. In each house, temperature and RH were measured and

recorded every 15 min at six locations, three 6 in above the floor and three ~8.75 ft above the floor. Two

pairs of sensors were placed about 30 ft in from each brood chamber and one pair was in the middle of the

brood chamber. No bird performance data were collected in this study due to the short duration of

monitoring.

Modification and short-term testing of the full-scale HRAC

Testing of the full-scale HRAC in Star indicated the challenges posed by dust as it clogged the burlap,

reducing air recirculation and increasing loading on the fan. An attempt to reduce dust accumulation by

spraying a known mass of staticide (to reduce static attraction) did not reduce saw dust accumulation.

Therefore, a mechanical shaker was installed inside the welded wire cage of the full-scale HRAC (Fig. 4).

The shaker was operated on a timer and when it came on, it shook the cage and it was expected that it would

reduce dust accumulation. In the lab, the shaking action seemed strong enough to reduce dust accumulation.

To test the effectiveness of the modified HRAC equipped with a mechanical shaker, the system

consisting of three layers of burlap soaked with 15% citric acid was deployed in a large room of the CTU

and tested from 14 to 21 Dec. 2016. This room held an assortment of poultry in pens and was considerably

dusty. Since the ammonia concentration in this room was quite low, we placed a trolley full of litter

upstream of the HRAC and wetted it with garden fertilizer to increase ammonia levels. Measured with gas

tubes, ammonia was 12-15 ppm (n = 2) at the start of the study. The HRAC was installed in the hallway

(Fig. 5) with its center about 6 ft above the floor. Pressure drop across the system was monitored with a

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Dwyer differential pressure transmitter connected to a Hobo data logger that recorded pressure drop every

5 min. Ammonia concentration was of the air entering the HRAC was measured using an acid scrubber

that pulled air from the top, bottom, and back side of the HRAC. At the outlet, air was sampled using a

manifold for ammonia concentration, also using an acid scrubber. Two TinyTag temp/RH sensors are

placed beneath the HRAC to measure and record temp/RH every 5 min. Average of these two readings

were used.

Without any dust deposition but with the acid-treated burlap, the fan pressure drop was 0.2 in which

corresponded to about 3,550 cfm. During 14-16 Dec., the shaker was on for 49 s and off for 950 s but

beginning 16 Dec., the shaker on time was increased to 99 s (off 900 s); the burlap was also cleaned lightly

with a brush which reduced pressure drop to 0.36 in. (corresponding to 2700 cfm). The scrubbers were

turned off when the shaker turned on.

B. Results and Discussion

Since the evaluation of the media and acids were presented in the semi-annual report, they will not be

discussed here. The filter medium used was burlap soaked in 15% citric acid in the testing performed in

the CTU as well as Star, NC.

Pen-scale testing: Chicken Testing Unit (CTU), NCSU, Raleigh, NC

1. Temperature stratification

Average (n = 3) temperatures close to floor (Low) and near the ceiling (High) are presented for the

Control and Test (with HRAC) treatments are presented in Fig. 6. Data were lost for some periods in

both treatments. There was greater thermal stratification (difference between the High and Low

temperatures) in the Control treatment particularly early in the study when ventilation rates were lower

(Fig. 6). As ventilation rates were increased with bird age, thermal stratification decreased (Fig. 6).

Fig. 6. Comparison of temperatures measured at bird height (Low) and near the ceiling (High) in the (a)

Control and (b) Test treatments. Temperatures were measured every 5 min and the lines are averages for

three pens in each treatment. Data were lost in both treatments as indicated by gaps in the trend lines.

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Average Low and High temperatures as well as their difference in the Control and Test treatments

during the five 5 d as well as over the flock are compared in Table 1. For both the 5-d period as well as

the entire flock, the Test treatment with the HRAC showed lower thermal stratification than the Control

(Table 1). In fact, during both of those periods, temperatures close to the floor in the Test treatment

were higher than the temperatures near the ceiling as well as the corresponding location in the Control

treatment (Table 1). Thus, the HRAC reduced thermal stratification and increased floor temperatures.

Table 1. Comparison of average ±SD Low and High temperatures as well as their difference (High-Low)

in the Control and Test treatments during the first 5 d and over the flock.

Period Control Test

Low High Difference Low High Difference

2/3-2/8 25.3±1.4 29±1.1 3.7 27.3±2.4 26.9±2.7 -1.1

Flock 25.7±1.4 26.6±2.4 0.9 26.5±1.7 26.1±1.8 -2.4

2. Electricity use

As was noted earlier, the pens were heated with brooding lamps whereas the aisle was heated with

propane furnaces. However, propane use was not monitored. During the study, the Control and Test

treatments had very similar electricity use (Fig. 7). It should be noted that the three HRAC units in the Test

treatment accounted for about 32 kWh of energy.

Figure 7. Comparison of electrical energy consumption in the Control and Test treatments.

3. Ammonia removal by HRAC

Time-averaged inlet and outlet ammonia concentrations into and from the HRAC, p-values (paired

t-test), and HRAC removal efficiency ({inlet [NH3] – outlet [NH3]}/ inlet [NH3]) for the first 4 weeks

of the study are presented in Table 2. Data for the second event (5-9 Feb.) were discarded because of

low scrubber volumes. In the remaining seven of nine events, inlet [NH3] – outlet [NH3] was

significantly greater than 0 ppm, showing that the HRAC significantly reduced concentration of

ammonia passing through it. Removal efficiency was as high as 0.42. Data (including pen ammonia

concentrations discussed below) for the last week (2-9 March was collected but could not be located

due to illness of the graduate student working on this project. However, high ammonia concentration

is more of a concern with younger birds.

At the start of deployment, the HRAC had an airflow rate of 80 cfm with a corresponding pressure

drop of 0.12 in. The HRAC units were lightly brushed on 24 Feb. They were again brushed lightly on

2 March; prior to brushing, their average pressure drop was ~0.23 in with a corresponding airflow rate

of 23 cfm. Post-brushing, their average pressure drop was ~0.15 in. with a corresponding airflow rate

of ~70 cfm. Based on the removal efficiency, the HRAC units provided modest ammonia removal.

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Table 2. Time-averaged inlet and outlet ammonia concentrations (±SD, n = 3) into and from the HRAC,

p-values, and HRAC removal efficiency for the first 4 weeks of the study.

Periods Ammonia conc., ppm

p-value Removal

efficiency Inlet Outlet

3-5 Feb 1±0.1 0.6±0.2 0.01 0.38±0.13

5-9 Feb Not calculated

10-12 Feb 1.2±0.3 1.1±0.2 0.29 0.03±0.1

12-16 Feb 1.8±0 1.7±0.2 0.25 0.06±0.12

16-19 Feb 1.8±0 1.2±0.3 0.03 0.35±0.17

19-22 Feb 1.8±0.3 1±0.1 0.02 0.42±0.08

22-24 Feb 2.1±0.1 1.3±0.2 <0.01 0.37±0.09

24-26 Feb 2.3±1.1 1.9±0.7 0.08 0.17±0.08

26-29 Feb 7.3±3.1 5.7±2.1 0.05 0.21±0.07

29 Feb - 2 Mar 13.2±5.9 9.6±4.4 0.03 0.27±0.03

4. Pen ammonia concentrations and litter analysis

Pen ammonia concentrations in the Control and Test treatments are compared in Table 3 for the

first 4 weeks of study. Using t-test (assuming equal variance), at = 0.1, in two of nine events, pen

ammonia concentrations were significantly lower in the Test pens than the Control pens. Data for the

second event (5-9 Feb.) were discarded due to the low solution volumes (35 mL) in the scrubbers.

Therefore, beginning the 3rd event, scrubber duty cycles were reduced from 75% to 50%. Based on

data in Tables 2 and 3, the HRAC provided moderate reductions in pen ammonia concentrations early

in the flock (first 3 weeks). While not significant, pen ammonia concentrations trended higher later in

the flock which might indicate that HRAC use after 3 weeks may not be helpful.

Table 3. Comparison of pen time-weighted average ammonia concentrations (±SD, n = 3) in the Control

and Test pens

Periods Ammonia conc., ppm

p- value Control Test

3-5 Feb 1.2±0.2 0.9±0.2 0.05

5-9 Feb Not calculated

10-12 Feb 1.6±0.8 1±0.2 0.14

12-16 Feb 2.1±0.2 1.9±0.1 0.19

16-19 Feb 3.3±1.1 1.9±0.4 0.05

19-22 Feb 3.5±1.8 2±0 0.11

22-24 Feb 4.8±2.9 2.5±0.3 0.12

24-26 Feb 3.6±1.9 2.7±1 0.25

26-29 Feb 8.3±2.8 8.4±3.1 0.49

29 Feb - 2 Mar 11.1±4.7 14.5±5.9 0.24

Litter analyses of the Control and Test pens at the end of flock are compared in Table 4. Using the

two-tailed t-test (assuming equal variance), there was no significant difference between the two

treatments in moisture content, TKN and pH (Table 4). However, despite slightly lower pen ammonia

concentrations, the Test pens had significantly higher TAN in the litter (Table 4) which was unexpected.

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Table 4. Comparison of litter properties (average±SD) between the Control and Test pens at the end of the

study.

Treatment Moisture content (%) TKN (g/kg-db) TAN (mg/kg-db) pH

Control 26.6±2.8 2.63±0.13 2752±115 8.35±0.26

Test 27.8±1.2 2.53±0.08 3044±179 8.29±0.12

p-value 0.52 0.61 0.09 0.72

5. Bird performance

Various bird performance parameters are compared between the Test and Control treatments in

Tables 5 through 7. Body weights of the Test and Control birds were not significantly different at 14

d and 35 d at = 0.1; however, the Control birds were significantly heavier at placement (Table 5)

which may have affected performance later in the flock. At both 14 d and 35 d, there was no significant

treatment effect on FCR (Table 6).

Table 5. Comparison of body weights at 14 and 35 d between the Test and Control treatments

Treatment Hatch 14 d 35 d

Control 48a 432 2005

Test 47b 423 1973

SEM <1 4 24

p-value <0.01 0.18 0.36

Table 6. Comparison of FCR at 14 and 35 d between the Test and Control treatments

Treatment 0-14 d 0-35 d

Control 1.62 1.73

Test 1.60 1.75

SEM 0.03 0.06

p-value 0.66 0.76

At 14 d, the Test treatment had significantly lower footpad dermatitis (FPD) score than the Control

treatment but not at 35 d (Table 7). However, valgus scores were significantly higher in the Test

treatment at 35 d (Table 7). The Test treatment had higher hockburn scores at 14 d (Table 7).

Significantly lower FPD scores but significantly higher hockburn scores in the Test treatment vs.

Control at 14 d seemed contradictory. High FPD and hockburn scores are associated with poor litter

quality and high ammonia levels (Haslam et al., 2006). However, pen ammonia concentrations were

lower in the Test treatment than the Control treatment earlier in the flock (Table 3) while litter quality

was not determined at 14 d. High litter TAN levels at 35 d (Table 4) could have hurt FPD and hockburn

scores but that was not observed in this study (Table 7).

Table 7. Comparison of FPD, valgus, and hockburn at 14 d and 35 d between the Test and Control

treatments in March 2016.

Treatment FPD score1 Valgus2 Hockburn3

14-d 35-d 14-d 35-d 14-d 35-d

Control 1.03a 2.09 0.28 0.45b 0.027b 0.53

Test 0.81b 2.05 0.23 0.57a 0.095a 0.55

SEM 0.07 0.10 0.04 0.04 0.019 0.04

p-value 0.02 0.75 0.32 0.04 0.01 0.72 1Score of 0 (footpad skin with no lesion) to 9 (all footpad and toes severely affected with lesions) 2Score of 0 (no limb deformity) or 1 (present) 3Score of 0 (absent) or 1 (present)

Commercial-scale testing: Broiler house, Star, NC

1. Temperature stratification

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Over the 1-week study, as shown in Table 8, both houses had similar temperature stratification as

indicated by average High and Low values as well as their difference, probably because the Control

house also had mixing fans. Whereas the Control house had seven 18 in fans that were likely moving

~24,500 cfm (at 3,500 cfm/fan), the HRAC units were moving a ~7,100 cfm (3,550 cfm/fan) initially.

Table 8. Comparison of hourly average ±SD Low and High temperatures as well as their difference

(High-Low) in the Control and Test houses during 14 through 21 March, 2016. Birds were placed in the

house on 15 March

Treatment Temperature, C

High Low Difference

Control 31.5±1.3 30.9±1.3 0.6

Test 32.6±1.2 31.9±1.3 0.7

Hourly average Low and High temperature trend lines in the Control and Test houses are plotted

in Fig. 8. Note the gradual decline in temperature over time as set point temperature in the houses were

reduced as the birds grew bigger. Beginning the evening of 19 March, the Low and High temperature

trend lines in the Test house started to diverge which may be due to reduced airflow rate through the

HRAC units as they continued to accumulate dust over the weekend (19-20 March). During the

workweek, the acid-coated burlap was cleaned with a broom daily that reduced accumulation and

maintained a high enough airflow rate to reduce thermal stratification. Hence, in commercial houses,

due to higher dust loads, the HRAC units would require daily cleaning or vacuuming.

Fig. 8. Comparison of hourly temperatures measured at bird height (Low) and near the ceiling (High) in

the (a) Control and (b) Test treatments. Temperatures were measured every 5 min and each temperature

line is the average of two sensors.

2. HRAC pressure drop

Pressure drop across the two HRAC units are presented in Fig. 9. Initial pressure drop averaged

for the two HRAC units was about 0.24 in which gave an airflow rate of 3,650 cfm. As is clear from

Fig. 9, with increasing dust accumulation, pressure drop increased approximately linearly. During the

work week (3/15-3/18), daily cleaning helped maintain pressure drop to <0.45 in but as pressure drop

increased to about 0.7 in over the weekend (3/18-3/19), airflow rate decreased to ~1,150 cfm.

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Fig. 9. Changes in pressure drops across the two HRAC units during 2016. Rapid decrease in pressure

drop was due to cleaning of the acid-coated burlap sacks with a broom.

3. Energy use

During 14 through 21 March 2016, the Control and Test houses consumed 111 and 145 gal,

respectively, of propane. These differences could be due to slight differences in their ventilation system

components (fans, thermostats, etc.) as well as the houses. However, the 30% higher propane

consumption in the Test house might also be partially explained by the 1.1 C higher temperature than

the Control house. While electricity consumption was not monitored, the seven 18 in. fans would

consume a total of 1.4 hp vs. 0.75 hp for the two HRAC fans.

4. In-house ammonia concentration and HRAC performance

Ammonia measurements were made at bird height with one measurement made mid-way and the

other measurements made adjacent to the HRAC units in the Test house and in the same relative

locations in the Control house. Time-averaged ammonia concentration in the Test and Control houses

are compared in Table 9. While statistics was not used, during 14-17 March, the Test house had higher

floor-level average ammonia concentrations though during 17-21 March, the Control house had higher

concentrations. It should also be noted that the concentrations are quite high.

Table 9. Comparison of time-averaged ammonia concentrations±SD1 in the Test and Control houses

during 2016.

Dates Test Control

14-15 Mar 14.7±4.6 9.4±4.7

15-16 Mar 23.7±3.0 19.2±4.0

16-17 Mar 30.9±6.52 26.1±7.0

17-18 Mar 26.2±0.32 28.4±1.0

18-21 Mar 96±2.4 90.5±10.22

1Based on three 3 replications unless indicated otherwise 22 replications

Removal efficiency of the two HRAC units are shown in Table 10. As shown in Table 10, data for

one HRAC was lost for 17-18 March while on many dates, the HRAC units showed no removal of

ammonia. The first HRAC unit showed higher removal than the second unit. However, the variability

in the removal efficiency is definitely a concern. The higher removal efficiency in both units was

observed during 18-21 March when the units were not cleaned. It is possible that reduced airflow rate

(due to greater dust buildup) combined with the dust absorbing ammonia played a role. Reduced

airflow rate may have increased temperature stratification (Fig. 8) and could also increase the risk of

the fan motors burning out. Therefore, the need to identify methods to reduce dust buildup required

investigation.

Table 10. Removal efficiency of the two HRAC units tested in the commercial broiler house during 2016.

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Dates Removal efficiency

HRAC1 HRAC2

15-16 Mar 0.36 0

16-17 Mar 0 0

17-18 Mar Lost 0

18-21 Mar 0.55 0.14

Modification and short-term testing of the full-scale HRAC

Since the purpose of this test was to evaluate the removal efficiency of the HRAC as affected by the

shaker’s ability to reduce pressure drop, we first present the pressure drop data and then the removal

efficiency. Change in pressure drop measured every 5 min across the three acid-soaked burlap bags is

plotted in Fig. 10. During 2:00 pm of 14 December to 9:00 am of 16 December 2016, the shaker operated

for 5% while the fan operated 95% but as pressure drop continued to increase, for the rest of the test, the

shaker operation time was increased to 10%. However, increased pressure drop due to dust accumulation

might have been due to humid conditions during noon 12/17 through 5:00 pm on 12/18 as shown in Fig.

10. Rapid decrease in pressure drop after 5:00 pm 12/18 could have been due to lower RH combined with

heavy buildup of dust which may have caused it to slough off. While the increased shaker time may have

helped, more research is required to optimize shaker operation time to reduce pressure drop. Starting

airflow rate at the lowest pressure drop of 55 Pa (0.22 in) was ~3,700 cfm whereas the lowest airflow rate

(at the higher pressure drop of 0.71 in or 178 Pa) was ~900 cfm. At the end of the study, at a pressure drop

of 0.42 in (104 Pa) the airflow rate was 2,900 cfm.

Fig. 10. Change in pressure drop of the HRAC and relative humidity (RH) in the vicinity of the HRAC

during 2016. Both measurements were taken every 5 min.

Removal efficiency of the HRAC based on time-weighted average inlet and outlet ammonia

concentrations for the 14-21 December 2016 period is shown in Table 11. During this test, performance

of the HRAC was poor.

Table 11. Removal efficiency of the HRAC unit equipped with a shaker tested in CTU during 2016.

Dates Removal efficiency

14-16 Dec. 0.12

16-19 Dec. 0.03

19-21 Dec. 0.03

178

0

50

100

50

100

150

200

12/14 12/15 12/16 12/17 12/18 12/19 12/20 12/21

Rel

ativ

e hum

idit

y,

%

Pre

ssure

dro

p, P

a

Date

Shaker action

Shaker time doubled

Increased pressure drop

due to increased RH?

13

Discussion

Overall, it was observed that both the pen- and full-scale HRAC units were able to reduce thermal

stratification and increase floor temperatures. Therefore, it has the potential to reduce energy use and/or

increase floor temperatures as has been reported by others (e.g., Czarick and Lacy, 2000; Flood et al., 1998).

However, unlike the pen-scale HRAC, the full-scale HRAC units did not provide consistent and appreciable

ammonia removal. One reason for the superior performance of the pen-scale HRAC units could be that

initial surface velocity (80 cfm/1.04 ft2 of surface area) through the acid-soaked burlap was 77 ft/min vs.

124 ft/min for the full-scale units. Longer residence time in the pen-scale HRAC units might have increased

removal efficiency vs. the full-scale HRAC. Another, perhaps, more important reason for superior

performance of the pen-scale unit might have been the much-lower ammonia concentration in the pen study

(Table 3) vs. the full-scale study (Table 9). The mass of citric acid in the burlap is more rapidly saturated

with increasing ammonia concentrations.

Deploying more but smaller units with greater ammonia absorbing capacity and designed for lower

surface velocity might improve ammonia removal and help maintain lower ammonia levels in commercial

houses. The shaker could help reduce pressure drops but would increase the cost.

The HRAC did not improve bird performance in the pens probably because the ammonia concentrations

were already too low to adversely affect bird performance. The commercial house study was very brief

and, very importantly, acidifiers were applied to both the Test and Control houses which reduced initial

ammonia concentrations.

C. Conclusions The HRAC was evaluated for its ability reduce thermal stratification and floor-level ammonia

concentrations in pens as well as a commercial house. Design improvement on the full-scale HRAC was

also investigated. Important findings were:

• The pen-scale HRAC units provided modest ammonia reductions and also showed that they reduce

ammonia concentrations at the floor level.

• The pen-scale HRAC reduced thermal stratification in pens vs. the control pens that had no means for

reducing thermal stratification.

• The full-scale HRAC provided inconsistent ammonia removal in a commercial house. It did not reduce

floor-level ammonia concentrations.

• The shaker was only partially-effective in reducing dust build-up on the full-scale HRAC.

D. References

Aviagen. 2009. Effective management practices to reduce the incidence of ascites in broilers. Technical

note. (http://en.aviagen.com/assets/Tech_Center/Ross_Tech_Articles/Ross-Tech-Note-Ascites.pdf)

Czarick, M., and M. Lacy. 2000. Reducing temperature stratification in houses with forced air furnaces.

Poultry Housing Tips 12(4). Cooperative Extension Service, Univ. of Georgia, Athens, GA.

Flood, C.A., J.L. Koon, R.D. Turnbull, and R.N. Brewer. 1998. Energy savings with ceiling fans in

broiler houses. Appl. Eng. Agric. 14(3):305-09.

Haslam, S.M., S.N. Brown, L.J. Wilkins, S.C. Kestin, P.D. Warriss & C.J. Nicol. 2007. Preliminary study

to examine the utility of using foot burn or hock burn to assess aspects of housing conditions for

broiler chicken. Br. Poult. Sci., 47(1): 13-18, DOI: 10.1080/00071660500475046

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