Engineered Systems Webinar Thursday, July 12, 2012 at 2 pm EST/11 am PST Tom Brooke PE, CEM, MBA, ASHRAE Member [email protected] TODAY’S PARADIGM FOR

Engineered Systems Webinar

Thursday, July 12, 2012 at 2 pm EST/11 am PST

Tom Brooke PE, CEM, MBA, ASHRAE Member

[email protected]

TODAY’S PARADIGM FOR HEAT RECOVERY – PART 2

2 Today's Paradigm for Heat Recovery - Part 2

Both Part 1 and Part 2 webinars are archived at: http://heatpipe.com/HomePage/Webinar/Webniar&Presentations.html

Both Part 1 and Part 2 supporting white papers are archived at: http://heatpipe.com/HomePage/mktg_materials/Papers.html

http://heatpipe.com/HomePage/Webinar/Webniar&Presentations.html




Part 1 - Four New Models

1 of 4 - Recovery Efficiency Ratio (RER)

1. AHRI Guideline V – 2003: applies to all Air-to-Air Heat Exchangers (AAHX)

2. Energy Saved/Energy Required to obtain that Savings

a. Includes all peripheral energy losses (Both airside pressure losses, wheel drive motor watts, circulating pump watts, purge losses because uses lower CFM)

b. RER forcedly links Effectiveness and pressure drop

3. Similar to Unitary EER and Applied kW/ton

4. S, L and T RER

5. Two selections can have same Effectiveness but one has superior RER

6. Dimensionless unless combined with associated equipment

Today's Paradigm for Heat Recovery - Part 2

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2 of 4 – Three Additional Designs Available are:

a. Adjacent, parallel airflows (design optimized for parallel instead of counter)

b. Separate airflows (condenser above in winter)

c. Separate airflows, pump assisted (condenser below in winter)

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW



3 of 4 – 1. Heat pipes have been preferred for years

in the more critical applications (labs, medical, clean rooms, etc.) because of their benefits compared to the trade-offs

2. Heat pipes are now also selectively replacing enthalpic AAHX in less critical applications

Item 2 is the Subject of Today’s Webinar!



4 of 4 - Heat Pipes are Technically and Economically Preferred to Glycol Pumped Systems, up to 100’ separation

Separ

ated

Hea

t P...

Pumpe

d Runar

...

Separ

ated

Hea

t P...

Pumpe

d Runar

...0

10

20

30

40

50

60

Separ

ated

Hea

t P...

Pumpe

d Runar

...

Separ

ated

Hea

t P...

Pumpe

d Runar

...0

50

100

150

200

$000

% Effectiveness RER 20 Yr LCC (Savings) Capital Cost


3. Heat Pipes Can Selectively Replace Enthalpic AAHX

a. Why - Product Benefits vs. Trade-offsb. Standards and Codesc. Engineering Judgment


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WHY - PRODUCT BENEFITS VS. TRADE-OFFS


Benefits vs. Trade-offs1. No moving parts, so inherently:

More reliable Less maintenance Longer service life


Benefits vs. Trade-offs

2. Designed for high pressure differential, so Fan locations can be disregarded No cross contamination



3. Rectangular cross section more efficiently

matches AHU, so reduced mechanical footprint

L

W

H



4. No electrical connections, so

installation and maintenance savings



5. Heat pipes available for adjacent parallel

and separated airflows, so more opportunities

for designer to use and less mechanical footprint

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW

AIRFLOW



6. Coatings for corrosive, toxic and

other specialized applications can be

applied to heat pipes



7. Higher efficiency, as defined by AHRI’s Recovery

Efficiency Ratio, so raises entire HVAC efficiency more


Benefits vs. Trade-offs8. Comparable or lower capital cost


1. No moving parts, so inherently: More reliable Less maintenance Longer service life

2. Designed for high pressure differential, so: Fan locations can be disregarded No cross contamination

3. Rectangular cross section more efficiently matches AHU, so reduced mechanical footprint

4. No electrical connections, so installation and maintenance savings

5. Heat pipes available for adjacent parallel and separated airflows, so more opportunities for designer to use and less mechanical footprint

6. Coatings for corrosive, toxic and other specialized applications can be applied to heat pipes

7. Similar or higher efficiency, as defined by AHRI’s Recovery Efficiency Ratio, so raises entire HVAC efficiency more

8. Lower capital cost

1. Only sensible energy is exchanged by heat pipes, rather than sensible plus latent for enthalpic devices

2. Effectiveness is sometimes less for heat pipes compared to energy wheels

Benefits Trade-Offs


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STANDARDS AND CODES


Requirement determined by: 1. Climate Zone2. Combination of SA CFM and OA% of SA

Change in enthalpy – can be latent, sensible or a combination

Two Basic Code Requirements

Requirement for .50 Total Effectiveness


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ENGINEERING JUDGMENT


First Subject for Engineering Judgment

Facts:1. Enthalpic AAHX have same total

effectiveness for summer and winter2. Sensible AAHX’s summer effectiveness is

10-20 percentage points lower than winter effectiveness

3. Nationally, most savings are in winter by far


Engineering Judgment1. ASHRAE does not mean to favor one type

of device over another2. It’s not fair to require one effectiveness

for one type of AAHX and a higher effectiveness for another type of AAHX

Question: What Effectiveness should be used for design?


My May, 2012 notification of the situation and request for an informal interpretation have been acknowledged by the ASHRAE Manager of Standards.

I believe a reasonable answer would be to design to the winter or summer Effectiveness based on which provides the higher total BTU savings at the facility’s location.

I also would point out that if a heat pipe is selected for winter total .50 Effectiveness, using Indirect Evaporative Cooling raises the summer total Effectiveness to higher than .50.


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Second Subject for Engineering Judgment

“Does it make fundamental good sense to use a sensible heat pipe instead of an enthalpic energy wheel?”

• Many OA hours are outside of ASHRAE 55 comfort zone

• Sensible AAHX address those to left and right

• What about those above (and perhaps in winter) needing latent exchange ?

• As will be explained shortly, the example shows Climate zone 5A, as represented by Chicago with retail operating hours.


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Procedure How to Answer that Question

1. Recognize that ASHRAE Std 55-2010 does establish the maximum dew point for comfort conditioning to be 61.52 ºFDP.


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Procedure (Cont’d)

2. Use the hourly recorded OA temperatures and humidities throughout the climate zones established by ASHRAE Std 90.1-2010 as the full map of weather data to be compared against Std 55’s comfort zone.


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3. To simplify the data management, a 2009 Pacific Northwest National Laboratory /DOE report established particular cities as the best representative of their climate zone.

Climate Zone City1A Miami2A Houston2B Phoenix3A Atlanta3B Los Angeles3C San Francisco4A Baltimore4B Albuquerque4C Seattle5A Chicago5B Denver6A Minneapolis6B Helena7 Duluth8 Fairbanks


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Procedure (Cont’d)4. Establish rules for data management:

a. Use TMY3 data b. Annual hours above established max dew point must be < 1%c. Winter data points also shown for referenced. Incorporate the fact that different types of facilities have

different operating hours

Profile Specific Hours Annual Hours

Code

Full Time All Hours 8,760 F Retail Hours Sun-Sat, 9am-10pm 4,745 R Office Hours Mon-Fri, 8am-6pm 2,610 O

K-12 School Hours Mon-Fri, Sep-Jun, 7am-5pm 2,170 K


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5. Each data point is one hour at its average temperature and humidity. Plot each of the 15 x 4 = 60 locations’ data points on a psychrometric chart preloaded with Std 55’s comfort range.

The example is for school hours in zone 2B as represented by Phoenix.


Results

31 of 60 total zone/hour combinations already have all the OA below Std 55’s maximum comfort humidity , so those are a higher priority to gain the benefits of heat pipes.

The plotted results for all locations is available in the accompanying explanatory white paper.

Climate Zones

Higher Priority

Lower Priority

All Hours Within ASHRAE

Std 55’s Comfort Humidity

Significant Hours Above ASHRAE Std

55’s Comfort Humidity

2BK, 3BFR, 3CFROK, 4BFROK, 4CFROK, 5BFROK, 6BFROK, 8FROK

1AFROK, 2AFROK, 2BFRO, 3AFROK, 3BOK, 4AFROK, 5AFROK, 6AFROK, 7FROK


Further Examples: Climate Zone 3C (SanFrancisco, 8760)


Climate Zone 4C (Seattle, Office)


What about Winter Humidification?

1. Enthalpic AAHX also humidify in the winter.2. For backup capability, all central HVAC systems

(cooling, heating, dehumidification, humidification) are generally sized as if the AAHX system were not installed. Therefore, there is no additional capital cost for winter humidification.

3. When a heat pipe is used for energy recovery, there is a slight increase in overall HVAC system operating cost to provide the humidification that the enthalpic device would otherwise provide. Neither type of AAHX provides all the humidification needed.


1. No moving parts, so inherently: More reliable Less maintenance Longer service life

2. Designed for high pressure differential, so: Fan locations can be disregarded No cross contamination

3. Rectangular cross section more efficiently matches AHU, so reduced mechanical footprint

4. No electrical connections, so installation and maintenance savings

5. Heat pipes available for adjacent parallel and separated airflows, so more opportunities for designer to use and less mechanical footprint

6. Coatings for corrosive, toxic and other specialized applications can be applied to heat pipes

7. Similar or higher efficiency, as defined by AHRI’s Recovery Efficiency Ratio, so raises entire HVAC efficiency more

8. Comparable or lower capital cost

1. Only sensible energy is exchanged by heat pipes, rather than sensible plus latent for enthalpic devices

2. Effectiveness is often less for heat pipes compared to energy wheels

Benefits Trade-Offs


Conclusions and Recommendations1. Understand heat pipe’s many benefits compared to

enthalpic AAHX and how they apply to a particular project.




2. As best can be done, quantify them. Note that many (reliability, no catastrophic failure, no cross contamination, longer service life, less maintenance) could have values an order of magnitude greater than energy savings.




2. As best can be done, quantify them. Note that many (reliability, no catastrophic failure, no cross contamination, longer service life, less maintenance) could have values an order of magnitude greater than energy savings.

3. Determine the additional energy saved by an enthalpic AAHX. Note that while the Effectiveness is often lower with heat pipes, their Efficiency (RER) is always higher.


Conclusions and Recommendations1. Understand heat pipe’s many benefits compared to enthalpic AAHX

and how they apply to a particular project. 2. As best can be done, quantify them. Note that many (reliability, no

catastrophic failure, no cross contamination, longer service life, less maintenance) could have values an order of magnitude greater than energy savings.

3. Determine the additional energy saved by an enthalpic AAHX. Note that while the Effectiveness is often lower with heat pipes, their Efficiency (RER) is always higher.

4. Understand and use the location priorities established earlier. Include the facility’s operating schedule in the analysis.

USING THE PRINCIPLES OUTLINED IN THIS WEBINAR

WILL IMPROVE YOUR HVAC SYSTEM.


Today’s Paradigm for Heat Recovery – Part 2

Thank You! Please give us feedback on the exit

survey.

Tom Brooke PE, CEM, MBA, ASHRAE Member

[email protected]

Documents

Engineered Systems Webinar Thursday, July 12, 2012 at 2 pm EST/11 am PST Tom Brooke PE, CEM, MBA, ASHRAE Member [email protected] TODAY’S PARADIGM FOR