The document discusses tunnel ventilation for poultry housing. Tunnel ventilation involves pulling air down the length of the house through inlets on one side and exhaust fans on the other to provide wind chill cooling for birds. Key factors in tunnel ventilation design include air speed, temperature gradient from inlets to fans, and relative humidity levels. When wind chill is no longer sufficient, evaporative cooling pads can be added to further lower the air temperature. The operation of a tunnel ventilation system and cooling depends on both air temperature and relative humidity to avoid over-stressing the birds.

1. TUNNEL VENTILATION
3rd ROSS BREEDERS ANADOLU INFORMATION
SHARING MEETING
October 2010
Bernard Green

2. DISCUSSION TOPICS
• Closed Environment Houses
• Wind Chill
• Tunnel Ventilation Design
• Cooling Systems
• Relative Humidity
• Evaporative Cooling• Evaporative Cooling
• Operating a Cooling System
• Operating Tunnel Ventilated Houses
• Hot Weather Preparation

3. CLOSED ENVIRONMENT HOUSES
• Commonly known as Tunnel Ventilation (TV)
• For (effective) temperature control in hot weather
• Takes place down length of house
• Exhaust fans at one gable end
• Long inlets in each side wall at opposite end• Long inlets in each side wall at opposite end
• Air is pulled down length of house
• Cooling effect of air movement (wind chill)
• Fans vary air speed and effect

4. Tunnel Ventilation

7. WIND CHILL
• Probably the most important factor in TV
• Cooling effect from air movement on the birds
• Depends on: bird age, dry bulb temperature, air
speed, RH
• Remember - Controller probe, dry bulb
thermometer cannot measure wind chillthermometer cannot measure wind chill
• Various wind chill charts available
• How many fans should I use?
• Always base the final decision on bird comfort

9. Windchill Example
8.0
5.5
3.5
9.0
6.5
4.5
WindChill(°C)
0.5 1.0 1.5 2.0 2.5 3.0
Air Velocity (m/s)
1.0
2.0
WindChill(

10. TUNNEL VENTILATION DESIGN
Two factors to consider:
1. Air speed
• fan cap. [m³/hr] = speed [m/s] x CSA [m2] x 3600
• CSA = cross section area
• CSA = (W x H) + (½W x R)
• 3600 = convert m/s to m/hr
• Narrow house preferred for TV
• Select fan based on operating pressure
W
H
R

11. Fan Operating Pressure
∆P
∆P
∆P
∆P
∆P
∆P
Fan Operating Pressure = ∆P + ∆P + ∆P + ∆P
∆P

12. Fan Performance Example
12m House – 8 x 50” fans
40 500m³/hr → 2,65m/s
38 000m³/hr → 2,54m/s
34 500m³/hr → 2,30m/s
32 000m³/hr → 2,10m/s32 000m³/hr → 2,10m/s

13. Fan Performance Example
Pressure
Pa
0 12 25 31 37 50
Fan Cap
m³/hr
43 185 40 635 38 084 36 384 34 684 30 434
Pressure
In WC
0.00 0.05 0.10 0.12 0.15 0.2

14. 2. Temperature gradient from inlet to fans
• Very important in long, wide houses
• Consider bird generated heat
• Radiant heat gain from sun (through roof)
• Keep temperature rise < 2,5°C• Keep temperature rise < 2,5°C
• Total inlet area must match full fan operating capacity

15. Air Deflector

16. Air Deflectors
Can be used in houses with low air speed
Air Deflectors have 2 effects:
1. Increase air speed by reducing CSA
2. Makes air movement more uniform
• Evens out air speed from sidewall to sidewall• Evens out air speed from sidewall to sidewall
Installation
• Install no more than 10m apart
• Do not install too low!
• Minimum height ±2,4m
• Too low can increase pressure on fans and have
opposite effect

17. ROOF INSULATION
• Poor insulation ⇒ high radiant heat gain
• Poor insulation ⇒ high temperature gradient
• Poor insulation ⇒ high heat loss (winter)
• TV system can’t cope with poor insulation

18. COOLING SYSTEMS
• At some stage wind chill isn’t enough
• Air must then be cooled
Options:
1. Spray (foggers)
2. Cooling Pads

19. Cooling Pads
Calculating pad area:
• Must know total operating TV fan capacity
pad area [m²] = fan cap[m³/hr] ÷ 2,03[m/s] ÷ 3600
• 2,03m/s ⇒ design air speed thru 150mm pad
• 1,27m/s ⇒ design air speed thru 100mm pad• 1,27m/s ⇒ design air speed thru 100mm pad
• 3600 ⇒ conversion from m³/hr to m³/s
• Install equally on either side (at end of the house)
• Ensure pad is installed in correct orientation
• Preferable to install on cooling pad room
• Allows pressure control after pad
• Easier to seal in winter (very important!)

20. 74%
24
66%
74%

21. Cooling Pad Orientation

22. Cooling Pad Room
Cooling Pad
(150mm)(150mm)
Weighted Curtain

24. Rack and Pinion Inlet

26. RELATIVE HUMIDITY
• Comparison of amount of water in the air at a
certain temperature, relative to maximum potential
amount at same temperature
• Cold air ⇒ can hold little moisture
• Hot air ⇒ can hold more moisture
• As temperature increases, RH decreases• As temperature increases, RH decreases
• As temperature decreases, RH increases
Temperature
RH

27. EVAPORATIVE COOLING
What is it?? How does it work??
• Nothing to do with warm air against cold water
• Nothing to do with cold water on the birds
• Little (nothing) to do with water temperature
• Achieved by a transfer of energy (heat) from the
hot air to the waterhot air to the water
• Air gives energy to water ⇒ cooler air
• Water absorbs energy ⇒ evaporates
• Amount of cooling possible depends on outside
wet bulb temp (RH)
• Dry environment (low RH) ⇒ very effective

28. Cooling Potential
∆T = Maximum cooling possible
Cooling pad is ±75% efficient, soCooling pad is ±75% efficient, so
Actual cooling = 0,75 x ∆T
This will be the temperature right at the pad
Dry Bulb Wet Bulb

29. ∆T
∆T
∆T small
High RH (humid)
Small cooling potential
Humid climate
Early morning
Late afternoon, evening
∆T big
Low RH (dry)
Bigger cooling potential
Dry climate
During peak temperature

30. Birds and Evaporative Cooling
When a bird is heat stressed, it loses heat in two
ways:
1. Convection, conduction, radiation (air movement)
Occurs during initial stages of heat stress
2. Evaporative cooling
• When air movement is no longer adequate• When air movement is no longer adequate
• Evaporative cooling takes place in the bird
• As the bird breathes, air passes over the wet
surfaces of its respiratory system
• Like a cooling pad, moisture is evaporated
• Effect is increased by panting (up to 250/min.)
• Low RH ⇒ easier to lose heat

31. OPERATING A COOLING SYSTEM
• Effectiveness of birds cooling system depends
on RH of air around it
• If RH low ⇒ effective
• If RH high ⇒ ineffective (can lead to mortality)
Rule of Thumb (guideline):Rule of Thumb (guideline):
• If house RH > 70%, switch cooling OFF
• Temperature will increase, RH will decrease
CANNOT operate cooling on temperature alone!
MUST operate on combination of Temp and RH

32. OPERATING TV HOUSES
• Use fans to regulate air speed, windchill, bird comfort
– If the birds are all sitting flat, there may be too much air
movement
– Be extremely careful with young chicks
• Tunnel inlet must be pressure controlled
• NEVER operate fans only on dry bulb temperature
• Thermometers, sensors can’t feel windchill• Thermometers, sensors can’t feel windchill
• Watch bird comfort (don’t ventilate for human comfort)
• The birds will tell you if they are hot, cold, comfortable
• When all fans are on, only then introduce cooling
• House RH > 70% ⇒ switch cooling OFF
• If RH drops below 70%, can switch back ON
• Modern controls do this automatically

33. OPERATING TV HOUSES
• The purpose of a cooling system is NOT to reduce
temperature to the set point
• It is to hold the temperature where the birds were last
comfortable
• When RH is high, air volume/exchange is critical
• Move gently through the house and get birds to stand,• Move gently through the house and get birds to stand,
releasing heat load
• Release entire heat load before switching to Cross
Ventilation (minimum ventilation)

34. Poorly Designed Tunnel Ventilation System
NoAirMovement
0,4m/s 0,8m/s 1,3m/s
NoAirMovement
Air Exchange Rate = 1,5minutes
Can expect heat stress mortality
Minimal mortality,
if any at all

35. Preferred Tunnel Ventilation Layout
2,5 m/s2,5 m/s
Air Exchange < 1 minute
Air exchange rate is good
All the birds are exposed to good air movement

36. TRANSITIONAL VENTILATION
• Can be seen as a 3rd ventilation system
• Involves extra sidewall inlets
• Uses CV and some TV fans together
• Air introduced through sidewall inlets
• Allows high air volume without TV effect
• Provides transition from CV to TV
• Used when more than CV is required, but too
“early” to go to TV
• DO NOT switch to TV too early!
• You can stress the birds with too much air
movement even if the temperature is over 30˚C

37. Minimum Ventilation
Transitional Ventilation
Tunnel Ventilation

38. Thank You