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Trane EarthWise Air Systems 2014
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EarthWise Air Systems
An Introduction to
High Performance HVAC Air Systems
Simon Ho – IR CSe: [email protected]
www.trane.com
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AirsideEnergy Recovery
Trane EarthWise Air Systems 2014
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Airside Energy Recovery (ER)
• Why Recover Energy ?
– A method of improving system efficiency using the exhaust air stream
– Exhaust air is a major energy recovery heat sink
• BCA requires the use of ‘energy reclaim system’ when
– OA quantity is > 1.2x of code minimum per AS1668.2 (e.g. Code min OA for offices is 10 L/s/person)
– Crowded areas with less than 1m2/person (e.g. cafe, restaurants, auditoriums) with OA exceeding 1,000 L/s
� alternately use demand controlled ventilation (DCV)
5
Code and Trends
• Demand for increasing airflow rates for IAQ - increases
energy consumption, e.g. Green Star IEQ-1 awards
• 1 credit for 50% over code minimum
• 2 credits for 100% over code minimum
• 3 credits for 150% over code minimum
• Airside system design has evolved from floor by floor
AHUs to central plants serving facade zones
– Efficiency in zoning, minimizes reheat
– OA and EA path proximity makes ER more feasible
• Integrated Controls Makes it Easy
– Optimize using HVAC equipment with unit mounted controls
Trane EarthWise Air Systems 2014
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Air-to-Air EROA Pre-conditioning
EAEA
OAOA
Heat
Exch
an
ge
Recovered energy to pre-cool or preheat
Sensible ortotal energy
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drydry--bulb temperaturebulb temperature
hu
mid
ity ra
tioh
um
idity
ratioRARA
OAOA
sensibleenergy recovery
OA'OA'
RA’RA’
Trane EarthWise Air Systems 2014
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drydry--bulb temperaturebulb temperature
hu
mid
ity ra
tioh
um
idity
ratio
OA'OA'
RARA
OAOA
totalenergy recovery
9
ER Effectiveness
Sensible effectiveness
Total effectiveness
εεεε = ××(T1 – T2)
(T1 – T3)ρρρρmin ×× Vmin
ρρρρs ×× Vs
εεεε = ××(h1 – h2)
(h1 – h3)ρρρρmin ×× Vmin
ρρρρs ×× Vs
airair--toto--airairheat exchangerheat exchanger
XX44
supply side
XX33
XX22XX11
exhaust side
ρρρρs ×× Vs
ρρρρmin ×× Vmin
Trane EarthWise Air Systems 2014
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SASA
“series”energy transfer
coolingcoolingcoilcoil
RARA
SASA
“parallel” energy recovery
coolingcoolingcoilcoil
Air-to-Air ERSupply Air Tempering (reheat after Dehum)
Recovered heat used for reheat
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OA Treatment Comparison
• Dedicated OA System (DOAS)
• Compare ER types: cool-reheat, RAC, EW, CDQ for
OA treatment
• OA 5,000 L/s @ 32/26°C
• RA 4,500 L/s @ 25°C/50% RH
• Required SA @ 18°C, 7 g/kg (8.7°CDP)
– Dependent on internal air system type, design RH% and latent load requirements
– Cooler SA contributes to sensible cooling; warmer SA requires more reheat
– Consider part load
Trane EarthWise Air Systems 2014
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DOAS: Cool Reheat
EAEA
OAOA
RARA
SASA
5 5 mm33/s/s
4.5 4.5 mm33/s/s25°C/50%RH
32/26°C
18°C, 7g/kg
8.9°C, 7g/kg 5 5 mm33/s/s
RHT
SPACE
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Cool Reheat
OA
SACA
REHEAT56 kW
RA
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Run Around Coil
Run Run
around around
coilcoil
EAEA
OAOA
RARA
SASA
5 5 mm33/s/s
4.5 4.5 mm33/s/s25°C/50%RH
32/26°C
18°C, 7g/kg
8.9°C, 7g/kg
5 5 mm33/s/s
29.1/25.3 °C
EAT CA
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RAC
OA
SACA
REHEAT56 kW
RA EA
EAT
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Total Energy Recovery
totaltotal--
energyenergy
wheelwheel
EAEA
OAOA
RARA
SASA
5 5 mm33/s/s
4.5 4.5 mm33/s/s25°C/50%RH
32/26°C
18°C, 7g/kg
8.9°C, 7g/kg
5 5 mm33/s/s
27.3/21.0 °C
EAT CA
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EW
OA
SACA
REHEAT56 kW
RA
EAT
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Air-to-Air Energy Recovery Technologies (airside)
• Run Around Coil (Coil Loop)
• Plate Heat Exchanger
• Heat Pipe
• Heat (Energy) Wheel
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expansion tankexpansion tank
pumppump
threethree--waywaymixing valvemixing valve
EAEA
OAOA
sensible-energy recovery devices
Coil Loop
• 45% – 60% sensible
effectiveness
• Very flexible
• No cross-leakage
• Capacity modulation
using variable-speed
pump or mixing valve
• Compact
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sensible-energy recovery devices
Fixed-Plate Heat Exchanger
• 60% – 70% sensible
effectiveness
• Capacity modulation
using face-and-bypass
dampers
• Very low cross-leakage
EAEA
OAOA
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sensible-energy recovery devices
Heat Pipe
• 30% – 55% sensible
effectiveness
• Capacity modulation
using bypass dampers
or tilt control
• Little or no cross-
leakage
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total-energy recovery devices
Total-Energy Wheel
• 65% – 80% total
effectiveness
• Capacity modulation
using bypass dampers
or variable speed
• Some cross-leakage
• Self cleaning (dry
particles)
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EA
OA
OA
EA
Fixed Plate Heat Exchanger Total Energy Wheel
Packaged AHU Solutions
• Factory mounted and tested controls
–Reduces site installation and commissioning time
–Single source responsibility
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EfficientDehumidification
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HVAC Dehumidification
• Dehumidification is moisture removal from OA or SA
• Dehumidification is an energy intensive process
– Use conventional cold cooling coils or desiccants
– Can reduce some energy input with air-to-air HR, but may still not meet moisture content or dew point target (not dry enough)
• Applications
– High OA demand buildings
– Green buildings with increased OA rates for better indoor air quality
– Humidity controlled environments e.g. operating theatres, ICU, museums, art galleries, pharmaceutical, dry storage etc
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HVAC Dehumidification
• Commercial offices: trend in use of sensible only
equipment in conditioned space like chilled beams,
chilled ceilings, displacement ventilation, underfloor air
distribution
– Increased dehumidification requirements of dedicated outside air systems (DOAS) which now has to process both the OA load as well as the space latent load
– Leads to requirements for dry air (low moisture content, low dew point) supplied into the space to handle latent loads
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HVAC Dehumidification
• Green Star awards 1 credit in IEQ-15 for maintaining
space RH < 60% at part load conditions
– At part load conditions space RH increases due to lower SHR caused by lower sensible loads compared to design conditions
– High space RH increases risk of mould in high RH areas (IEQ-15)
• Many Green Star jobs do not claim this point due to
costs of installing an active desiccant wheel system;
also energy penalty using active heat
– Solution in efficient dehumidification equipment
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Performance of Desiccant WheelsDesiccant Isotherms
ability tohold water
vapor
high
relative humidity, %
low
0 60 1004020 80
Type III(CDQ) regenerates below 80% RH
Type I
Type II
typicalmixed-air
conditions
typicalleaving-coilconditions
Active heat to ‘dry out’
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Type II Series DesiccantTrane CDQ (Cool Dry Quiet)
Trane CDQ Type III Desiccant
Condensate
CoilCA
OA
RA
SASA
MAMA'
WA
TE
R V
AP
OR
Cooling CoilCHW or DX
PR
EH
EA
T
CDQ WHEEL in CLCPMoisture laden air
Co
ol d
eh
um
idif
ied
air
AHU with integrated passive desiccant wheel to produce supply air with lower dew point than conventional cooling coils
RE
HE
AT
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Trane CDQ - DOAS
Trane CDQ Type III Wheel
CONDENSATE
Coil
PR
EH
EA
T
CA
OA
RA
SA
LR
WA
TE
R V
AP
OR
11.6/11.5C 99% 8.4g/kg
18.0/12.7C 55% 7.0g/kg 8.7C DP
30.0/26.3C 75% 20.2g/kg
Cooling Coil
5,000 L/s 32/26C, 62.5% 18.8g/kg
0 L/s
RE
HE
AT
13.6/10.9C 72% 7.0g/kg
EAT
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CDQ
OA
SA
CA
LR
REHEAT
27 kWREHEATAVOIDED
30 kW
CA’
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Trane CDQ with AC HR Chiller
Coil
PR
EH
EA
T
CA
OA
RA
SA
WA
TE
R V
AP
OR
11.6/11.5C 99% 8.4g/kg
18.0/12.7C 55% 7.0g/kg 8.7C DP
5,000 L/s 32/26C, 62.5% 18.8g/kg
0 L/s
RE
HE
AT
CO
OL
ING
CO
IL
• Preheat for dehumidification during humid times
• Reheat to achieve target SADB
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Dehumidification with Energy Recovery vsType III Desiccant
Reduces Cooling energy by reducing air-on
Reheat required to achieve desired SADB
Potential for contamination
Exhaust air stream required
Energy Recovery CDQ
Reduces Cooling energy by dehumidification, raising air-off conditions
Minimize Reheat required to achieve desired SADB
No contamination
Exhaust airstream not required
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CDQ + EW Dual Path Dual Wheel
TRANE CDQ WHEEL
Coil
CA
OA
LR
11.7/11.6C 98% 8.4g/kg
25.8/21.2C 67% 13.6g/kg
29.7/24.1C 63.6% 16.7g/kg
RE
HE
AT
18/12.7C 55% 7.0g/kg
EN
ER
GY
WH
EE
L
OA
CO
OL
ING
CO
IL
23.0/18.4C, 65.1% 11.4g/kg
SA
RA`4,500 L/s 25.0C 50% 9.9g/kg
EA
LW1
WA
TE
R V
AP
OR
CD
Q W
HE
EL
5,000 L/s 32/26C, 62.5% 18.8g/kg
13.5/10.8C 73% 7.0g/kg
LW1
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CDQ + EW Dual Path
OA
SA
CA
LR
REHEAT
28 kW
RA
LW1EA
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Series CDQ + EW Dual Wheel
TRANE CDQ WHEEL
Coil
PR
EH
EA
T
CA
OA
LR
WA
TE
R V
AP
OR
11.8/11.7C 98% 8.5g/kg
18.0/12.7C 55% 7.0g/kg 8.7C DP
25.3/21.4C 71% 14.4g/kg
5,000 L/s 32/26C, 62.5% 18.8g/kg
RE
HE
AT
13.8/11.0C 72% 7.0g/kg
EN
ER
GY
WH
EE
L
OAC
OO
LIN
G C
OIL
5,000 L/s 27.3/21.0C, 57.3% 13.0g/kg
SA RA
EA
LW1
4,500 L/s 25.0C 50% 9.9g/kg
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Series CDQ + EW
OA
SA
CA
LR
REHEAT
26 kW
RA
LW1
EA
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Type III Series Desiccant AHU Trane CDQ
• Enhanced dehumidification device
– Not an Energy Recovery Device as it does not require an exhaust air stream
– No contamination
• Extends the dehumidification range of conventional
CHW systems (3 to 8K lower dew point)
– No need for high temperature regeneration
– Nil or minimized reheat
• Energy efficient way to control humidity with factory
packaged controls
• Further improvement in efficiency used in conjunction
with Energy Wheel in Dual Wheel application