Ventilation Mistakes, Management & Controls

R.S. GATES, PhD, P.E.

Outline of Today’s Talk

  Ventilation Systems Basics

  Fan Selection Using BESS Lab Performance Test Results

  Ventilation Requirements for Pigs

◦  Cold, Mild, Hot Weather

◦  Different Production Stages

  Air Distribution in the Building

  …Using Homework Examples

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Why Ventilate?

  Pig well-being ◦  Pig comfort

  Delivery of major inputs ◦  Air

◦  Water

◦  Feed

  Removal of products of metabolism ◦  Gases

◦  Particulates

◦  Manure

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Ventilation Design   What do we do to consistently maintain an optimum environment? ◦  Engineering design

  How do we know if our design is successful? ◦  Facility commissioning

  Will a properly designed and commissioned system always work? ◦  Facility instrumentation, observation, and maintenance

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Fan Performance

Ventilation rate (cfm) depends on air pressure (inch water) against which the fan works

Variation in airflow rates among 0.9-m (36 inch) and 1.2-m (48 inch) fans, as measured with the FANS

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18Static Pressure, inch WC

Fan

airf

low

rate

, cfm

48" fans

36" fans

1 cfm = 1.7 m3/hr

1 inch WC = 248.9 pa

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Ventilation Rate

  How much air are these fans actually moving?

  All fans are different – even “certified” fan models

  But let’s look at performance measurement

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University of Illinois BESS Lab Fan Performance website

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Handout 1: Fan Selection Method from BESS Lab Database

Given: A desired ventilation rate for a specific task. For example, 2,000 cubic feet per minute (cfm) at 0.10 inch static pressure (SP) is needed for 1,000 newly weaned pigs (12 lb body weight).

  Required: Find a 14” diameter propeller fan from the BESS database (bess.illinois.edu), which delivers no less than the desired airflow at the specified building static pressure. The fan must not have any sort of steel blades or housing because of concern for corrosion.

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Solution Method

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1.  Go to the BESS lab website bess.illinois.edu 2.  Select “Performance Tests” from the tabs at the top of the page 3.  Select “Current Performance Tests” from the tab to get recent data 4.  Select “60 Hz (North America)” for a U.S. application 5.  Use the drop-down tabs to select: All Manufacturers, and choose a 14”

diameter, then press Submit 6.  Review the fans. For example, look at the Exacon 07479e (Model

AF14LP) and note its Air Flow at 0.10 in SP is 2480 cfm. Click on the Test # for that model fan to open a fan test summary sheet. (see next page for the fan test summary format from BESS).

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Note that it has a plastic housing and plastic shutters (not metal). It has a wire guard and a discharge cone. It has a 6-blade plastic propeller. It is providing 2,480 cfm at 0.10 in. H2O (static pressure), running 1554 rpm, using 230.4 volts, 1.35 Amps, and 306 Watts. The fan efficiency (VER, ventilation efficiency ratio) is 8.1 cfm/Watt.

Fan Performance Curves: 48” fans in one poultry barn*

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8,000

10,000

12,000

14,000

16,000

18,000

20,000

22,000

0.00 0.05 0.10 0.15 0.20 0.25

Air

flow

(CFM

)

Static Pressure (inches of water)

Source: D.G. Overhults University of Kentucky

On-site Determination of Fan Performance Curve

Upstream (inside)

Downstream (outside)

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Comparison to BESS Lab Test Data*

bess.Illinois.edu – free fan performance data

EMILI  2015  

13

0  

20  

40  

60  

80  

100  

120  

Brand  A  DD  Brand  C  BD  Brand  B  DD  Brand  D  BD  

%  of  L

ab  Tes

t  Airflow

    36” fans DD = direct drive BD = belt drive

Source: D.G. Overhults University of Kentucky

University of Illinois

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Dirty Fans and Shutters

  1/8 inch of dirt/dust can cause up to a 40% reduction in fan and shutter air flow.

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Handout 2: Ventilation Rate Requirements for Swine

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Given: We need to determine the proper amount of ventilation for different size and type of pigs. We will use this information to determine building minimum and maximum ventilation rates for each type of production facility.

For example, how many cubic feet per minute (cfm) for 1,200 newly weaned pigs (12 lb body weight)?

Or how many cfm are required for 1,200 finishing pigs?

Required: Use the recommended rates (next slide) as a basis. Note, these are in cfm/pig.

Air Flow Requirement For Each Pig, cubic feet of air per minute (cfm)

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  Cold  Weather  Rates                (for  moisture  control)      

Fully  slo)ed

Partly  slo)ed Solid  floor Rate  for  odor  

control Mild  

Weather Hot  

Weather Sow  and  Li9er 10 17 20 35 80 325 Pre-­‐nursery  pig  

(12-­‐30lb) 1.0 1.6 2 3.5 10 25

Nursery  pig  (30-­‐75lb) 1.5 2.5 3 5 15 35

Growing  pig  (75-­‐150  lb) 3.5 5.5 7 10 24 75

Finishing  pig  (150-­‐220+  lb) 5 8 10 18 35 120

GestaJng  sow  (325  lb) 6 10 12 20 40 150

Boar  (400  lb) 7 12 14 24 50 180

Examples:

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1.  How many cfm are needed for 1,200 newly weaned pigs at the cold weather rate? Answer: depends on floor type. For fully slotted floor we need 1 cfm/pig thus 1,200 cfm; for a solid floor we need 2 cfm/pig, or 2,400 cfm total.

2.  How many cfm are needed for 1,200 finishing pigs at the cold weather rate? Answer: also depends on floor type. For a fully slotted floor: 5 cfm/pig or 6,000 cfm. For a solid floor: 10 cfm/pig or 12,000 cfm.

3.  How many cfm are needed for 1,200 finishing pigs at the hot weather rate? Answer: 120 cfm/pig, or 144,000 cfm

Conclusion: Ventilation rate requirements vary tremendously with the size of the animal and to a lesser extent with the type of housing. We need to determine these values in order to properly design a ventilation system, whether it is natural ventilation, mechanical ventilation, or a hybrid combination of both methods.

We calculate the fresh air requirement by season:

  In winter, just enough air to remove the moisture produced by the pigs

 In summer, enough air to remove the heat produced by the pigs

  Between times, a smooth transition of air exchange

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Bring in the Fresh Air Fresh air must mix

Inlets need to be properly sized

Inlet air velocity is the key

The role of static pressure is critical

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Air speeds at the pig level are very important

  Small pigs – less than 0.15 m/s (30 feet/minute)

 Larger pigs – less than 0.25 m/s in winter (50 feet/minute)

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Fan and Inlet Systems

Right amount of fresh air Right place Right speed

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Fan Performance and Building Static Pressure

  Ventilation rate depends on the pressure against which the fan works

  Fan creates static pressure (if building is tight

Static pressure determines air velocity through inlets

We want 800-1000 feet/min inlet velocity

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Measuring Static Pressure Outside the building

Inside the building

Very Important! Measuring Static Pressure: An Inclined Manometer, or Digital Manometer. Scale: mm H2O or Pa

Pd

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The Air Inlets Determine:

  Fresh air placement in the room

  Proper mixing of fresh air with stale air

  Air speeds at pig level

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For good air mixing, fresh air should enter the room in a “jet” – 800 to 1,000 feet per minute

Outside the building

Inside the building

LOW SP: more air from fan, lower inlet air velocity

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High SP difference: less air from fan, higher inlet air velocity

Outside the building

Inside the building

HIGH SP

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Air leaving the room through an exhaust fan doesn’t cause a draft

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Manage the numer of inlets based on size of pigs (i.e. ventilation rate needed

Not all openings needed when pigs are small

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Handout 3: Fresh Air Inlets Area Determination

Given: Determine how much inlet area is needed for a required ventilation rate.

  The formula (in English units) is:

  A = 144*Flow/Velocity, where A is square inches, Flow is in cfm, and Velocity is in feet/min. Design values for Velocity are about 800-1,000 fpm so this simplifies to

  A=0.144*Flow, or 1 ft2 /1000 cfm

  (The 144 converts square feet to square inches). You can also remember it is 1 square foot of opening needed per 1000 cfm.

   Required: You must figure the area based on the ventilation rate provided. Calculate the total opening area needed. Then, you should be able to figure out how big an opening is needed for different inlet lengths.

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Simple four-sided air inlet for ceiling installation

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Examples of Calculations   1. Given a 1,200 head finisher building with a winter time ventilation rate of 2,400 cfm, how many square inches of opening do we need?   Answer: Area = 0.144 x 2,400 = 345.6 in2 (2.4 ft2)

  2. Given 12 ceiling inlets, each with 4 ft (48 inches) of opening, approximately how wide should be the opening in this example?   Answer:   Width of Opening = Area/Length = 345.6 in2 /(48 in./inlet x 12 inlets) = 0.6 in. Very small! (Shut down some openings!)

  3. For the same facility at summer conditions the required ventilation is 144,000 cfm. How much opening do we need now?   Answer: Area = 0.144 x 144,000 = 144 ft2 = 20,736 in2

  4. Will the 12 ceiling inlets have enough opening area, if they have 8 ft per inlet?   Answer: Width = 20,736 in2 /(96 in./inlet x 12 inlets) = 18 inches….Very large! We need more inlets or different design.

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Conclusion

  Since the building’s ventilation rate requirements vary tremendously with the size of the animal, so will the required inlet area.

  This is a key problem in mechanically ventilated systems – to provide the proper inlet area to promote good air exchange and good mixing of fresh air with indoor air, without drafts and without dead spots.

  Understanding the role of static pressure difference is helpful for proper inlet design and operation

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Airflow in a farrowing room

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Cold weather inlets

Mild weather inlets

Hot weather inlets

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Summary

R.S. GATES, PhD, P.E.

Match fans to needs Design and maintain necessary ventilation rates Design and maintain correct air inlets Building Ventilation – it’s a system…