Alternative evaporative cooling and naturally ventilated double roof system for environmental...
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Transcript of Alternative evaporative cooling and naturally ventilated double roof system for environmental...
Alternative Alternative evaporative coolingevaporative cooling
and and naturally naturally ventilated double roof ventilated double roof
systemsystem for for environmental environmental
controlled controlled dairy barndairy barn located in tropical located in tropical
and subtropical and subtropical regionsregionsWei Fang, Ph.D., Professor
Dept. of Bio-Industrial Mechatronics EngineeringNational Taiwan University
Part I. Alternative evaporative cooling
Evaporative coolingEvaporative cooling
Pad and FanPad and Fan
Pad and Fan system is Pad and Fan system is PowerfulPowerful
But it require But it require proper design, proper design, proper installatioproper installatio
nnandandproper maintenaproper maintena
nce.nce.
Poor Poor design/install/maintenandesign/install/maintenan
cece
Poor Poor design/install/maintenandesign/install/maintenan
cece
ElectrolysisElectrolysis
Coated PadCoated Pad
Pad substitutes - Palm tree Pad substitutes - Palm tree fibersfibers
Pad substitutes – Rolling Nets
Dry bulb Temperature, oC
Rela
tive
mil
kin
g
perf
orm
an
ce
1998, ASAE fundamentals
Effect of wind speed Effect of wind speed on milking performance on milking performance
of Holstein cowof Holstein cow
Wind SpeedWind Speed 10 10 ooCC 26.7 26.7 ooCC 35 35 ooCC
0.18 m/s0.18 m/s 100 %100 % 85 %85 % 63 %63 %
2.44 m/s2.44 m/s 100 %100 % 95 %95 % 79 %79 %
4.02 m/s4.02 m/s 100 %100 % 95 %95 % 79 %79 %
1998, ASAE fundamentals
25~70 Pa pressure dropη =70 % for 15 cm pad
2.5 m/s
Multi-layer nets with Multi-layer nets with sprayingspraying
View from insideView from outside
Fogging is better than spraying
Multi-layer nets with Multi-layer nets with foggingfogging
Multi-layer nets with Multi-layer nets with foggingfogging
ComparisonComparison
OutdoorOutdoor
TTdbdb 32 32 ooCC
RH 55%RH 55%
TTdb db
After Pad After Pad Wind speedWind speed
m/sm/s
EfficiencyEfficiency
10 cm Pad10 cm Pad 26.37 26.37 ooCC 1.5-2.51.5-2.5 75 %75 %
28.25 28.25 ooCC 4.04.0 50 %50 %
Multi-Net with Multi-Net with foggingfogging
25.0 25.0 ooCC 8.08.0(3 AC/min)(3 AC/min)
92.5%92.5%
Part II. Naturally ventilated double
roof system
Materials for Roofs Materials for Roofs
Porous galvanized Porous galvanized steel platesteel plate
Traditional galvanized steel Traditional galvanized steel plate with PU attachedplate with PU attached
Learn from the mother Learn from the mother naturenature
Tiny holes on roof mimicking stomata of leaf
Porous double roofPorous double roof
Air gap between two layers provides driving force when heated by solar radiation.Such driving is self adjusted according to the intensity of outdoor solar radiation
Roof materialsRoof materials
Traditional single Traditional single layer galvanized layer galvanized steel plate + PUsteel plate + PU
DisadvantageDisadvantage Non-recycleNon-recycle PU burnablePU burnable Hot air trap insideHot air trap inside
Porous double layer Porous double layer galvanized steel plategalvanized steel plate
AdvantagesAdvantages Can be recycledCan be recycled Fire proofFire proof Provide roof opening allow Provide roof opening allow
hot air escape from roofhot air escape from roof Heated air layer enhance Heated air layer enhance
natural convectionnatural convection
Galvanized steel plate (GSP)
GSP + PU
Double Porous GSP
Code 11 is house 1 & sensor at location 1: 0.5 m from ceiling height (with no ceiling installed) , code 36 is
house 3 & sensor location is 3 m from roof
Comparison on peak Comparison on peak temperaturestemperatures
Single roofSingle roofPorous Double roofPorous Double roof
45.5 oC
38.3 oC 38.3 oC
41.1 oC
Galvanized steel plate (GSP) GSP + PU
34.9 oC
37.6 oCDouble Porous GSP
No ceiling installed
Another experimentAnother experiment
Single layer galvanize Single layer galvanize steel platesteel plate
Single layer galvanize Single layer galvanize steel plate +PUsteel plate +PU
Porous double layer Porous double layer galvanize steel plategalvanize steel plate
Single layer galvanize Single layer galvanize steel plate + white paintsteel plate + white paint
Reflective white paint Reflective white paint increase reflectivityincrease reflectivity
Wavelength, nm
Refl
ecti
vity
Galvanize steel plate painted with Reflective
white pain
Galvanize steel plate (light
green color)
Positions of T sensorsPositions of T sensorsDL porous
SL & PU SL + paint
SLOutside surface
Inside surface
Center air
Outside surface
Inside surface
Center air
Avg. T during Avg. T during 10:00-10:00-14:0014:00
T ofT of center center airair
T ofT of outside outside surfacesurface
T ofT of inside inside surfacesurface
SLSL 37.0037.00 53.9153.91 48.9748.97
SL + PUSL + PU 37.1337.13 64.2564.25 46.3646.36
DL porousDL porous 32.4232.42 52.2352.23 36.7136.71
SL + paintSL + paint 33.3233.32 49.6649.66 35.2535.25
△T = 5 oC △T = 15 oC △T = 13 oC
ConclusionsConclusions Multi-layer nets fogging system provides good evaporative
cooling efficiency even under high air velocity. Double layer porous roof provide naturally ventilated roof
vent. It also has the capability of self adjusting according to outdoor solar radiation.
Roof materials painted with Reflective white paint absorbed 30% of solar radiation, yet other roof absorbed 70% of solar radiation.
An experimental daily barn was build based on above findings.
50 m x 15 m x 2.5 m, 50 cows
Wind speed 2.5 m/s
Air exchange 2 times/min
Porous double layer galvanized steel plate
Thank you for your attention