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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: Simon.Ho@irco.com

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)

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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

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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’

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drydry--bulb temperaturebulb temperature

hu

mid

ity ra

tioh

um

idity

ratio

OA'OA'

RARA

OAOA

totalenergy recovery

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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

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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