Tunnel ventilation havaland - Ross

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