Energy Recovery Ventilators - · PDF file · 2011-08-26Energy Recovery Ventilators. Ryan Doering ... Passive Desiccant Wheels; ... Size ERVs for the Dehumidification Design ASHRAE

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Energy Recovery Ventilators

Ryan Doering – John Q. Bullard Assoc., Inc.

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Preconditioning of fresh outside air by using exhaust (return air) from a building

Typical types of ERV:

Enthalpy wheels

Heat pipes

Fixed plate heat exchangers

Terminology

HRV –

sensible heat transfer only

ERV –

sensible and latent; “total enthalpy”

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Energy Savings –

Lower Operating CostLower First Construction CostLower Maintenance Cost (Depending on Technology)Better Indoor Environment –

Fresher Employee Productivity IncreasesBetter Grades for Students (ASHRAE Research)Green Buildings are MarketableReduced Environmental Impact, Lower Water UsageReduced Green House EmissionsReduced Carbon Foot PrintReduced Ambient Sound LevelsLowest Cost to Treat Outside Air –

bar noneAssists with LEED™

Certification

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Enthalpy wheels: good moisture transfer, higher cost, maintenance

Heat pipes: metal pipes carrying refrigerant, no moisture transfer, sensible only

Fixed plate exchangers: sensible only until now, low cost and maintenance

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Heat Exchanger

•Pre-Cools air during the summer

•Pre-Heats air during the winter

Cool Dry Exhaust Air From the Space

Hot Wet Outside Air

Cooler Drier Outside Air Supply To the Space or AHU

Heat and Water are Exhausted from the Space

89° db/82° wb

81° db/79° wb

75° db 50% rh

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Indoor Models

Rooftop Models

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Latent Duty – Water RemovalPart Load Latent PerformanceCan we take credit for the capacity recovered –

Is it Failsafe? Maintenance Requirements –

Will it be done & at what costWhat is the application – how much recirculation

is acceptableHow long does it lastDoes it fit our available space

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EffectivenessEnthalpy Wheel

Heat Pipes

Cellulose ERV

Nano TechERV

Sensible (Summer Conditions) 75% 45% 75% 74%

Latent (Summer Conditions) 62% 0% 25% 67%

Sensible (Winter Conditions) 72% 50% 78% 71%

Latent (Winter Conditions) 64% 0% 28% 60%

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Passive Desiccant Wheels

High Latent Fixed Plate ERVS

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Review Full Load & Part Load and Dehumidification DesignSize ERVs for the Dehumidification Design ASHRAE 2005

Handbook

Ch 28. -

Monthly Design Wet Bulb with Mean Coincident Dry Bulb

Evaluate Part Load Latent Performance

Extreme Outside Air humidity loads (Outside Air 85° Sat)

80°f/80°f (db/wb)

Balance Sensible Temperatures ex. 75°/50% exhaust and 75° saturated Outside Air

For DX Systems -

70°f Saturated (70° and raining)

Winter Performance

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R R

ASHRAE PSYCHROMETRIC CHART NO.1NORMAL TEMPERATURE

BAROMETRIC PRESSURE: 28.821 INCHES OF MERCURYCopyright 1992

AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS, INC.

1033 FEET

Weather Hours81 to 7372 to 6463 to 5554 to 4645 to 3736 to 2827 to 1918 to 109 to 1

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20

25

30

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40

45

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SUMMERCOMFORT

ZONEWINTERCOMFORT

ZONE

55 60 65 70 75 80 85 90 95 100

DR

Y B

ULB

TE

MP

ER

ATU

RE

- °F

.002

.004

.006

.008

.010

.012

.014

.016

.018

.020

.022

.024

.026

.028

10% RELATIVE HUMIDITY

20%

30%

40%

50%

60%

70%

80%

90%

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55

55 60

6065

65

70

70

75

75

80

80

85 WET BULB TEMPERATURE - °F

85

14.0

14.5 VOLUME- CU.FT. PER LB. DRY AIR

15.0

HU

MID

ITY

RA

TIO

- PO

UN

DS

MO

ISTU

RE

PER

PO

UN

D D

RY

AIR

AC Design Day

Dehum Design Day

R R

ASHRAE PSYCHROMETRIC CHART NO.1NORMAL TEMPERATURE

BAROMETRIC PRESSURE: 28.821 INCHES OF MERCURYCopyright 1992

AMERICAN SOCIETY OF HEATING, REFRIGERATING AND AIR-CONDITIONING ENGINEERS, INC.

1033 FEET

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Augusta Bin Data Analysis

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Columbus Bin Data Analysis

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Macon Bin Data Analysis

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Savannah Bin Data Analysis

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26.5 Gal hr

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Part Load Analysis 75 F Saturated –

100% Latent Duty

14.7 Gal hr

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10 Gal hr

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