11/19/2009. Poultry house ventilation system. Poultry house ventilation system design. Example: Exhaust fan capacity rule of thumb

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1 Poultry house ventilation system Basically consists of exhaust fans and air inlets. Exhaust fan draw in fresh air Poultry House Ventilation System Design Michael Czarick III The University of Georgia Poultry house ventilation system design How much exhaust fan capacity should a house have? Basically consists of exhaust fans and air inlets. Exhaust fan draw in fresh air Inlets direct the fresh air to where we want it to go. Exhaust fan capacity rule of thumb Example: 60 X 300 broiler/turkey house 60 X 300 X 7 = 126,000 cfm (25 24 fans) Minimum exhaust fan capacity for a power-ventilated broiler/turkey house: 7 cfm per square foot of floor space (130 m 3 /hr per m 2 ) This should ensure that there is no more than a 5 o F (2.7 o C) increase from the inlet to the exhaust fans 4 5 cfm per square foot of floor space for house which is curtain-ventilated during hot weather 1

2 This is minimum Heat produce by broilers has increased approximately 20% in the last 20 years. The typical U.S. broiler/turkey house: 8 10 cfm per square foot of floor space. 60 X 300 = 144, ,000 cfm 50 years ago 30 years ago Today Turkeys have changed as well What type of fan should a house be equipped with? Exhaust fan selection criteria 1. To obtain desired air exchange rate exhaust fan capacity must be determined at a minimum static pressure of 0.10 (25 Pa). Exhaust fan selection criteria 2. Energy efficient It is not how much power a fan uses it is how many cubic feet per minute it can move with each watt of power: Cfm/watt The higher the rating the lower your operating costs will be. Desired energy efficiency rating Should have an energy efficiency of at least 20 (34 cmh/watt)..ideally cfm/watt (35 cmh/watt) or better 2

3 Not only do we want a fan that is energy efficient, we want a powerful fan as well. 3. Exhaust fan air flow ratio An indicator of how well the fan will hold up to high static pressures caused by: Dirty fan shutters Clogged inlet screens Fan output vs. static Pressure (48 fans, between 20,000 and 22,000 cfm) Air flow ratio = air flow (0.20 )/ airflow (0.05 ) Cfm 26,000 24,000 22,000 20,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2, Static Pressure Not only do we want a fan that is energy efficient, we want a powerful fan as well. 3. Exhaust fan air flow ratio An indicator of how well the fan will hold up to high static pressures caused by: Dirty fan shutters Clogged inlet screens Winds A fan with a high air flow ratio is less affected by the wind Wind pressure (in) Wind speed (mph) This is a serious problem with variable speed fans! Fan output vs. static Pressure (48 fans, between 20,000 and 22,000 cfm) Air flow ratio = air flow (0.20 )/ airflow (0.05 ) Cfm 26,000 24,000 22,000 20,000 18,000 16,000 14,000 12,000 10,000 8,000 6,000 4,000 2, Static Pressure

4 Air flow ratio Minimum acceptable = 0.73 Ideal = 0.78 or higher Fan performance information is available at Exhaust fan selection criteria 4. Size Keep small fans to a minimum They are very effective for minimum ventilation but Small fans are a very poor investment: Higher initial cost Higher operating cost Higher maintenance cost Estimated initial fan cost 60 X 300 house with 126,000 cfm of fan capacity Fan Cost ($) $12,000 $11,000 $10,000 $9,000 $8,000 $7,000 $6,000 $5,000 $4,000 $3,000 $2,000 $1,000 $ Fan Size ( ) Fan size and energy efficiency (the larger the fan the more energy efficient it tends to be) ency (cfm/watt) Energy Efficie Fan Size ( ) Fan operating cost (,000 cfm for 24 $0.10 per Kw*hr) $29.00 $27.00 $25.00 $23.00 $21.00 $19.00 $17.00 $15.00 $13.00 $11.00 $9.00 $7.00 $ Fan Size ( ) 4

5 This does not mean you can t install a few small fans but The optimal exhaust fan system stages from small to large fans quickly: Two - four 24 fans minimum ventilation fans Two - four36 fans moderate weather Then 48 fans or larger for the remainder of the required fan capacity hot weather Another advantage of keeping the number of small fans to a minimum Reduces the potential for shutter air leakage ½ the shutters ½ the cold spots.0 F 60.0 F Cold spots near exhaust fans Fan shutter leakage Problems with leaky shutters can be further reduced by placing exhaust fans in groups Minimizing cold spots Leakage exits adjacent minimum ventilation fans 5

6 The fact is that fans do not have to be evenly spaced down the length of the house Poultry house with a single fan and four air inlets Poultry house with two fans and air four inlets Poultry house with a single fan and eight air inlets Poultry house with a single fan and 16 air inlets Poultry house with a single fan and 16 air inlets 6

7 Poultry house with a single fan and 16 air inlets But you MUST establish a negative pressure if you want to gain control over the environment ft/min 950 ft/min 950 ft/min 950 ft/min 950 ft/min 950 ft/min 950 ft/min 950 ft/min Outside Ventilation system design It is very important to realize that though fan placement can be of some importance Inlet design/placement is by far, more important when it comes to maintain proper environmental control +% of ventilation system design is proper inlet design and placement maybe 20% or less is exhaust fan placement Chimney fans? Chimney fans with poor inlets 7

8 Chimney fans with poor inlets Poor side wall inlet Cool side wall Poor conditioning of incoming air Air inlet system design Air inlet capacity How much inlet area should a house have? General rule of thumb: 1 square foot for every 750 cfm of exhaust fan capacity. or 1 square meter for every 4,0 m 3 /hr 8

9 Air inlet example: 40 X 300 with 84,000 cfm (7 cfm/ft 2) Inlet area = 84,000 cfm / 750 cfm = 168 square feet (16 m 2 ) If the house had a single continuous inlet Air inlet system(s) For optimal control a modern poultry house should have a minimum of two inlet system.ideally three Each inlet system is specifically designed to be used to obtain specific objectives Inlet width = total inlet area/ house length = 168 ft 2 /300 ft = 0.56 feet or 6 or 15.2 cm 1) Cold weather inlet system It is specifically designed to bring in just enough air to maintain air quality during very cold weather: Maximize heating of incoming cold air Distribute fresh air throughout the house evenly Without causing drafts Without t causing excessive fuel usage 2) Moderate weather inlet system Designed to control house temperature during moderate weather. 3) Hot weather inlet system Minimum ventilation inlet system Designed to maximize bird heat removal Produce high air velocities over the birds to maximize heat removal 9

10 Minimum ventilation inlet system Specifically designed for use for very cold weather for use with just a few exhaust fans minimum ventilation fans. 1 2 cfm per square foot. 60 X 300 X 1.5 = 27,000 cfm Might consist of only 20 to 30 inlets Minimum ventilation inlet guidelines 1) Located towards the center of the house That is where your hottest air tends to accumulate Furthest distance from the birds F F Example of minimum ventilation inlets Example of minimum ventilation inlets Desired air flow pattern from minimum ventilation inlet Desired air flow pattern from minimum ventilation inlet 96.2 F F 10

11 Minimum ventilation inlet guidelines 2) Draw air out of the attic Less affected by wind Warmer air for a portion of the day Attic vs. outside temperatures 85.0 F F 78.2 F 75 Tempe erature (F) Jan 4-Jan 6-Jan 8-Jan 10-Jan 12-Jan 14-Jan 16-Jan 18-Jan 20-Jan 22-Jan 24-Jan 26-Jan 28-Jan Date 30-Jan 1-Feb 3-Feb 5-Feb 7-Feb 9-Feb 11-Feb 13-Feb 15-Feb 17-Feb 19-Feb 21-Feb 65 attic F Minimum ventilation inlet guidelines 3) Located above a house s heating system to help temper incoming cold air Minimum ventilation inlets above tube heaters F F F F Minimum ventilation inlets above hot water fin pipes Minimum ventilation inlets above hot water system F F 11

12 Generally, it is best to have a single row of minimum ventilation inlets Minimum ventilation inlets Could be single direction inlets, but should be located near centerline Heating system location have reduce problems with minimum ventilation inlets near the side walls Offset minimum ventilation inlets Offset minimum ventilation inlets Generally, it is best to have a single row of minimum ventilation inlets 12

13 Two rows of bidirectional minimum ventilation inlets Two rows of bidirectional minimum ventilation inlets Beam deflecting air jet F F 55.0 F F 60 Beam deflecting air jet A continuous inlet is a very poor minimum ventilation inlet F F 13

14 Very difficult to obtain a uniform small opening Side wall or a ceiling continuous inlet.0 F 60.0 F F.0 F.0 F 60.0 F 60.0 F Continuous inlets do not tend to produce adequate tempering of incoming air To maximize the tempering of the incoming air We must keep the air away from the birds as long as possible 5 C 10 C 15 C 20 C Little tempering/mixing of incoming air Air dumping to floor during minimum ventilation F F 14

15 Heating not being utilized on the far side of the house. Birds becoming chilled directly under inlet. Fan side of house birds are significantly warmer. In order for a minimum ventilation inlet system to work proper All the air should enter through the inlets If the houses are loose Air entering through cracks will not mix. Drafts Poor fresh air distribution Reduced litter drying Loose door Loose door 37.8 C 37.8 C F C 21.1 C 37.8 C F C 15

16 Loose door Loose door C C C C Loose door Loose fan shutters 38.0 C 38.0 F C F Loose fan covers Loose side walls 72.1 F F F F 16

17 Side wall leakage Crack in side wall F 60.0 F Houses must be tight to maximize air quality Static pressure vs Opening We want all the air to enter through the inlets. House tightness test should be conducted from time to time. Turn on a two 36 fans (four 24 fans) Measure the resulting static pressure Then use the following chart to determine if the house is tight enough e Area (ft2) Leakage Static Pressure Optimally tight house (0.65 square feet of leakage per 1,000 square feet of floor space) Air inlet systems 1) Cold weather - minimum ventilation 2) Moderate weather temperature control 17

18 Moderate weather inlets Inlets on both sides of the house maximum temperature and air quality uniformity More needed than minimum ventilation inlets 4-5 cfm per square foot of floor space Around three times as much as minimum ventilation inlets If not tunnel ventilated (7+ cfm/ft2) Located along both side walls pulling air from directly outside tid the house Attic inlets during for use for moderate ventilation? Attic inlets during hot weather What makes a good temperature control inlet? Air flow directed toward ceiling at an angle Directs the air where you want it to go. 18

19 Air flowing out of recessed inlet in 50 wide house What makes a good temperature control inlet Directs the air when you want it to go. Recessed inlet Surface mounted inlet sits on the wall a recessed inlet sits in the wall. Cold air exiting sides of air inlet Air flowing out side of inlet Warm air flowing the side of recessed inlet.0 F F 19

20 Air focused at top of the inlet which improves throw Examples of recessed side wall inlets 85.0 F F Moderate weather inlets More needed than minimum ventilation inlets 4-5 cfm per square foot of floor space Around three times as much as minimum ventilation inlets If not tunnel ventilated (7+ cfm/ft2) Located along both side walls pulling air from directly outside tid the house Ideally can direct the air up toward the ceiling during cooler weather and down toward the floor during warmer weather Air flow along the floor during warmer weather Side wall inlet capable of directing incoming air downward Deflector board for hot weather bird cooling 20

21 Deflector board for hot weather bird cooling Air inlets Cold weather minimum ventilation Moderate weather temperature control Hot weather bird heat removal system Hot weather is whenever it is warmer outside than you want it inside. Importance of air movement when it comes to cooling birds In order to cool a bird we have to get air to move over its body....0 F More air speed more cooling 75.0 F Still Air - 25 o C 300 ft/min - 25 o C 21

22 Turkeys (26 o C 150 ft/min) 0.75 m/sec - 26 o C 39.0 C C 2 m/sec - 26 o C 2 m/sec - 26 o C 39.0 C C Air movement in traditional crossventilation during hot weather Designed to conserve heat and not to produce air movement over the birds 5 C 10 C 15 C 20 C 22

23 Designed to produce little air movement at bird level Very little air movement at floor level during cold weather 5 m/sec 3.5 m/sec 2.5 m/sec 1.5 m/sec less than 0.25 m/sec During the summer they will tend to conserve heat also Very little air movement during hot weather as well 2.5 m/sec 1 m/sec 26 o C 26.5 o C 27 o C 28 o C 5 m/sec 0.75 m/sec to 0.5 m/sec over limited areas Things are improved if you have inlets on both sides of the house Attic inlets during hot weather 2.5 m/sec 1 m/sec 5 m/sec 0.75 m/sec to.025 m/sec 23

24 Inlets in the center of the house Side wall of house Attic inlets during hot weather Center of house Inlets directed to the floor Downward facing hot weather inlet improves the situation even more 5 m/sec 2.5 m/sec 0. 5 m/sec <0.25 m/sec 24

25 Downward inlet on one side of a house Downward facing inlets on both sides of th house even better 35.0 C C C C 5 m/sec F F m/sec 1 m/sec 75.0 F 75.0 F Even with inlets that direct air downward cooling fans may be required. Using circulation fans for bird cooling 5 m/sec 1.5 m/sec 1 m/sec 36 circulation fan coverage area Poor air movement distribution wide house 25

26 36 circulation fans blowing across the house Limited coverage area 39.0 C C Birds directly in front of fan Most houses don t have enough circulation fans to provide the necessary air movement C C Air inlets Cold weather minimum ventilation Moderate weather temperature control Hot weather heat removal system tunnel ventilation is just another inlet system Best heat removal system is tunnel ventilation 26

27 Air exchange and air velocity Cross ventilation vs. Tunnel ventilation.0 F 95 Air velocity of between 2 and 3 m/sec 85 Air exchange typically less than every 60 seconds 75.0 F.0 F F Tunnel ventilation is just an additional stage of ventilation For most of the year the house is no different from what you may already be doing. Fewer side wall/chimney fans Fewer side wall inlets Minimum ventilation +0.5 C Moderate ventilation Moderate ventilation +1.5 C +2 C 27

28 Low level tunnel ventilation Medium level tunnel ventilation +3 C +4 C High level tunnel ventilation mczarick@uga.edu (6) C 28