TODAY’S PARADIGM FOR AIR- TO-AIR HEAT RECOVERY Engineered Systems Webinar Wednesday April 11, 2012 at 2 pm EST / 11 am PST Tom Brooke, PE, MBA, CEM

TODAY’S PARADIGM FOR AIR-TO-AIR HEAT RECOVERY

Engineered Systems WebinarWednesday April 11, 2012 at 2 pm EST / 11 am PST

Tom Brooke, PE, MBA, [email protected]

Framework, perspective or example in a particular discipline at a given time

These four new models are:New and additional, or Updated

Today's Paradigm for Air-to-Air Heat Recovery

PARADIGM

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1. Standards and Codes2. The Paradigm’s First New Model3. The Paradigm’s Second New Model

- The Three Es of Effectiveness, Efficiency, Economics4. The Paradigm’s Third New Model5. The Paradigm’s Fourth New Model

- The Three Es of Effectiveness, Efficiency, Economics6. Summary7. Questions and Answers


CONTENT - OVERVIEW

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1. STANDARDS AND CODES

Today’s Paradigm for Air-to-Air Heat Recovery 4


AAHX* PRODUCT STANDARDS

1. Product Scope (Wheels, Pipes, Plates, Runaround)

2. Uniform Test Protocol

1. Product Scope (Wheels, Plates, Pipes)2. Performance Ratings at Std Conditions3. Certification Program

*AHRI uses ‘AAHX’ to refer to these Air-to-Air Heat (and Energy) Exchangers

5


BUILDING CODE ADMINISTRATION

Dept of

EnergyInternational Code Council

1992 Energy Policy Act

ANSI/ASHRAE Std 90.1

6


STATUS BY STATE (3/6/12)

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1. Std’s climatic zones determine requirements

2. At least 50% enthalpic Effectiveness

3. Ten general exceptions


ANSI/ASHRAE STANDARD 90.1 (AAHX)

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2. THE PARADIGM’S FIRST NEW MODEL


EFFICIENCY!-Not Just Effectiveness-A New, Additional Model


1. Effectiveness is the actual heat transfer’s % of the maximum heat transfer

2. S, L and T Effectiveness3. Because of condensation, sensible AAHX can

have both sensible and enthalpic Effectiveness

4. Does not consider energy consumed


EFFECTIVENESS

11

1. AHRI Guideline V 2. Recovery Efficiency Ratio (RER)3. Energy Saved/Energy Required to obtain that

Savings4. Similar to Unitary (EER) and Applied equipment

(kW/ton)5. Applies to all AAHX6. S, L and T Efficiency


EFFICIENCY

12

1. Includes all peripheral energy lossesa. Both airside pressure lossesb. Wheel drive motor wattsc. Circulating pump wattsd. Purge losses (uses lower CFM)

2. RER inexorably links effectiveness and pressure drop

3. Two selections can have same effectiveness but one has superior RER

4. Dimensionless unless combined with associated equipment


RECOVERY EFFICIENCY RATIO (RER)

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3. THE PARADIGM’S SECOND NEW MODEL



MORE AIRFLOW OPTIONS!

- Not Just Adjacent Counterflow- An Updated Model

15


ADJACENT, COUNTERFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

1. Traditionally the only layout2. Lowest cost3. Highest heat transfer

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ADJACENT, PARALLEL

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

1. Slight Additional Cost2. Lower Heat Transfer than Standard Arrangement in Counterflow Application3. Higher Heat Transfer Than Standard Arrangement in Parallel Flow Application

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SEPARATED, PASSIVE

1. Separation provides airflow design flexibility2. Up to 100’ horizontal if 50’ vertical; 40’ horizontal if equal heights3. When vertical difference, higher coil can only be condenser4. When equal heights, full year operation5. Valve For economizer control and freeze protection

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SEPARATED, PUMPED

1. Horizontal separation up to 100 ft2. Vertical separation up to 30 ft3. Magnetically coupled fractional HP pumps4. Pump control for economizer operation and freeze protection

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MORE OPTIONSHeat Pipe

Configuration

Airstreams Airflows Applicability

Adjacent Counter Flow

Winter/ Summer

Adjacent Parallel Flow

Winter/Summer

Separated (up to 100’ H, 50’ V

Counter/Parallel

Flow

Winter

Summer

Separated (up to 40’ H)

Counter/Parallel

FlowWinter/Summer

Separated (up to 100’H, 30’V)

Counter/Parallel

FlowWinter/Summer

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WHAT ABOUT EFFECTIVENESS AND EFFICIENCY?

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Major Items1. 10,000 CFM OA; 10,000 CFM EA; 500 FPM2. Clg plant eff is .75 kw/ton; htg eff is .703. Utility costs per Northwestern Energy4. LCC factors per NIST/DOE5. BIN annual energy costs include:

a. Full economizerb. Modulated economizerc. Frost control

Complete description of all items is in the companion article at www.heatpipe.com


TECHNICAL BACKGROUND

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Heat Pipe Configurati

on

MBH Transferre

d

% Sensible Effectivene

ssAirside PD”

(Each)Recovery Efficiency

Ratio

314 56 .56/.60 42.6

228 41 .56/.60 30.9

255 45 .56/.60 34.6

287 51 .56/.60 28.9


EFFECTIVENESS, EFFICIENCY

OA: 20.0ºF DB/18.3ºF WB; EA: 72.0ºF DB/55.8ºF WB

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WHAT ABOUT ECONOMICS?

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1. ASHRAE 90.1 Climatic Zones2. Chicago is Roughly Center of Winter Zones


WHERE?

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Heat Pipe Configurati

onCapital

Cost $000

Annual Maintenan

ce Cost $000

Annual Energy Saved $000

Twenty Yr LCC $000(Savings)

21 1.3 17 +210

24 1.3 13 +148

46 1.3 14 +143

87 1.6 15 +118


ECONOMICS

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1. Fan costs: Since damper space is not always available, this analysis uses valve and pump control for economizer and frost control. If space is available for dampers, some pressure drop may be eliminated for a lower annual fan operating cost.

2. Without a pump in the heat pipe system: a. There will only be winter savings (incorporated), and b. Item one above may also apply (not incorporated).


ECONOMIC NOTES

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4. THE PARADIGM’S THIRD NEW MODEL


HEAT PIPES MAY SELECTIVELY REPLACE

ENTHALPIC AAHX!-A Replacement Model

Today's Paradigm for Air-to-Air Heat Recovery 29

Question: How To Meet ASHRAE 90.1 for 50% Total (enthalpic) Effectiveness

Answer: Use an 8 row heat pipe at 350 FPM instead of 6 row at 500 FPM

ROWS FPMSENSIBLE

EFFECTIVENESS

TOTAL EFFECTIVENE

SSTOTAL RER

6 500 .56 .41 42.68 350 .68 .50 68.3


BUT ….

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Winter

Summer

Conclusion – Latent Recovery Not

NeededToday's Paradigm for Air-to-Air Heat Recovery

SAN FRANCISCO BIN AND 1% DESIGN DATA WITH ASHRAE 55

COMFORT ZONE

DB ºF

DP ºF/MCDB ºF

40.0 27.8/50.6

DB ºF/MCWB ºF

DP ºF/MCDB ºF

78.0/62.0 59.1/66.3

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1. *No Moving Partsa. Reliable - No emergency breakdownsb. Less maintenance $

2. *Fan Location Not Criticala. No possibility of cross contamination

3. *Allowable Pressure Differential up to 55”4. More Compatible with AHU Geometry

a. Standard Rectangular coil constructionb. Complete cross sectional area is functional

5. No Electrical Connections


ADVANTAGES OF HEAT PIPES* ASHRAE Fundamentals Handbook

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1. There are certain geographical regions within North America that have the right weather, and

2. Heat Pipes can easily meet building codes, and

3. The benefits of heat pipes are very valuable to all building owners

HEAT PIPES MAY SELECTIVELY REPLACE ENTHALPIC AAHX


IT IS CLEAR THAT:

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1. Mr. Brooke solicits all opinions ([email protected])

2. A broader and more substantive explanation will be published soon at www.heatpipe.com


HEAT PIPES SELECTIVELY REPLACING ENTHALPIC AAHX …

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5. THE PARADIGM’S FOURTH NEW MODEL


HEAT PIPES ARE ECONOMICALLY BETTER THAN A RUNAROUND

COIL LOOP <100’-An Updated Model

Today's Paradigm for Air-to-Air Heat Recovery 36

1. Three way valve maintains:a. Fluid temp ~ 40ºF to EA Coilb. Max SA temp

2. Pump control for economizer


COIL RUNAROUND LOOP

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Comparison Logic - All heat pipes selected at common 6R/12 fpi, but runaround fin/tube characteristics different …

a. Maximize effectiveness 10R/12fpi, 1.8 pump BHPb. Minimize airside PD for min RER 6R/9fpi, 2.4 pump BHP

MBH Transferre

d (1% Design)

% Effectiveness

Airside PD “

(each)

Tubeside PD’

(each)/ GPM

RERAnnual Energy Saved $000

Capital Cost $000

Annual Maintenanc

e Cost $000

20 Yr LCC$000

(Savings)

a. 252 45 1.40/1.44 32.3/42.8 11.0 4 45 1.6 -4b. 191 34 .56/.58 17.6/72.9 14.3 7 44 1.6 +35


RUNAROUND 3 ‘E’s

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COMPARISON

Note: Frost and economizer control reduces the heat transfer of the more effective AAHX

RUNA

ROUN

D

39

Adjace

nt C

ount

er Fl

ow

Adjace

nt P

arall

el Flo

w

Separ

ated

Passiv

e

Separ

ated

Pumpe

d

Pumpe

d Run

arou

nd

Adjace

nt C

ount

er Fl

ow

Adjace

nt P

arall

el Flo

w

Separ

ated

Passiv

e

Separ

ated

Pumpe

d

Pumpe

d Run

arou

nd0

10

20

30

40

50

60 % Effectiveness RER

HEAT

PIP

E

HEAT

PIP

E

HEAT

PIP

E

HEAT

PIP

E

HEAT

PIP

E

HEAT

PIP

E

RUNA

ROUN

DD

RUNA

ROUN

DD

HEAT

PIP

E

HEAT

PIP

E

COMPARISON (CONT’D)

Comparing separated systems, a lower capital cost for glycol will cost the owner dearly!


0

50

100

150

200

250 20 YR LCC (SAVINGS)

$0000

20

40

60

80

100 CAPITAL COST

$000

40

1. Recovery Efficiency Ratio should be a standard criteria in all AAHX evaluations.


6. SUMMARY

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2. In addition to the traditional adjacent counter flow airflow design, HVAC system designers now also have access to economically justified adjacent parallel and separated (to 100’) heat pipe systems.


6. SUMMARY

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3. Recognize that some geographical locations do not need the complexities of latent exchange and heat pipes meet code. Without the latent exchange and moving parts, heat pipes are more reliable, have lower maintenance costs, longer life and zero cross contamination.


6. SUMMARY

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3. Recognize that some geographical locations do not need the complexities of latent exchange and heat pipes meet code. Without the latent exchange and moving parts, heat pipes are more reliable, have lower maintenance costs, longer life and zero cross contamination.

4. With the economics and their compelling advantages, heat pipes are preferred to 100’ separation. Runaround coil loops are preferred beyond that, and/or if multiple OA/EA coils.


6. SUMMARY

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TODAY’S PARADIGM FOR AIR-TO-AIR HEAT RECOVERY

Thank You! Please give us feedback on the exit survey.

Tom Brooke, PE, MBA, [email protected]

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Documents

TODAY’S PARADIGM FOR AIR- TO-AIR HEAT RECOVERY Engineered Systems Webinar Wednesday April 11, 2012 at 2 pm EST / 11 am PST Tom Brooke, PE, MBA, CEM