TODAY S PARADIGM FOR HEAT RECOVERY PART 2

Transcription

1 TODAY S PARADIGM FOR HEAT RECOVERY PART 2 Engineered Systems Webinar Thursday, July 12, 2012 at 2 pm EST/11 am PST Tom Brooke PE, CEM, MBA, ASHRAE Member tombrooke@cox.net

2 Both Part 1 and Part 2 webinars are archived at: r&presentations.html Both Part 1 and Part 2 supporting white papers are archived at: Papers.html 2 Today's Paradigm for Heat Recovery - Part 2

3 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 3 Today's Paradigm for Heat Recovery - Part 2

4 Part 1 - Four New Models 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) AIR FLOW AIR FLOW 4 Today's Paradigm for Heat Recovery - Part 2

5 Part 1 - Four New Models 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! 5 Today's Paradigm for Heat Recovery - Part 2

6 Part 1 - Four New Models 4 of 4 - Heat Pipes are Technically and Economically Preferred to Glycol Pumped Systems, up to 100 separation % Effectiveness RER 20 Yr LCC (Savings) Capital Cost $ Today's Paradigm for Heat Recovery - Part 2

7 3. Heat Pipes Can Selectively Replace Enthalpic AAHX a. Why - Product Benefits vs. Trade-offs b. Standards and Codes c. Engineering Judgment 7 Today's Paradigm for Heat Recovery - Part 2

8 WHY - PRODUCT BENEFITS VS. TRADE-OFFS 8 Today's Paradigm for Heat Recovery - Part 2

9 Benefits vs. Trade-offs 1. No moving parts, so inherently: More reliable Less maintenance Longer service life 9 Today's Paradigm for Heat Recovery - Part 2

10 Benefits vs. Trade-offs 2. Designed for high pressure differential, so Fan locations can be disregarded No cross contamination 10 Today's Paradigm for Heat Recovery - Part 2

11 Benefits vs. Trade-offs 3. Rectangular cross section more efficiently matches AHU, so reduced mechanical footprint H W L 11 Today's Paradigm for Heat Recovery - Part 2

12 Benefits vs. Trade-offs 4. No electrical connections, so installation and maintenance savings 12 Today's Paradigm for Heat Recovery - Part 2

13 Benefits vs. Trade-offs 5. Heat pipes available for adjacent parallel and separated airflows, so more opportunities for designer to use and less mechanical footprint AIR FLOW AIR FLOW 13 Today's Paradigm for Heat Recovery - Part 2

14 Benefits vs. Trade-offs 6. Coatings for corrosive, toxic and other specialized applications can be applied to heat pipes 14 Today's Paradigm for Heat Recovery - Part 2

15 Benefits vs. Trade-offs 7. Higher efficiency, as defined by AHRI s Recovery Efficiency Ratio, so raises entire HVAC efficiency more 15 Today's Paradigm for Heat Recovery - Part 2

16 Benefits vs. Trade-offs 8. Comparable or lower capital cost 16 Today's Paradigm for Heat Recovery - Part 2

17 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 Benefits Trade-Offs 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 17 Today's Paradigm for Heat Recovery - Part 2

18 STANDARDS AND CODES 18 Today's Paradigm for Heat Recovery - Part 2

19 Two Basic Code Requirements Requirement determined by: 1. Climate Zone 2. Combination of SA CFM and OA% of SA Requirement for.50 Total Effectiveness Change in enthalpy can be latent, sensible or a combination 19 Today's Paradigm for Heat Recovery - Part 2

20 ENGINEERING JUDGMENT 20 Today's Paradigm for Heat Recovery - Part 2

21 First Subject for Engineering Judgment Facts: 1. Enthalpic AAHX have same total effectiveness for summer and winter 2. Sensible AAHX s summer effectiveness is percentage points lower than winter effectiveness 3. Nationally, most savings are in winter by far 21 Today's Paradigm for Heat Recovery - Part 2

22 Engineering Judgment 1. ASHRAE does not mean to favor one type of device over another 2. 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? 22 Today's Paradigm for Heat Recovery - Part 2

23 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 Today's Paradigm for Heat Recovery - Part 2

24 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. 24 Today's Paradigm for Heat Recovery - Part 2

25 Procedure How to Answer that Question 1. Recognize that ASHRAE Std does establish the maximum dew point for comfort conditioning to be ºFDP. 25 Today's Paradigm for Heat Recovery - Part 2

26 Procedure (Cont d) 2. Use the hourly recorded OA temperatures and humidities throughout the climate zones established by ASHRAE Std as the full map of weather data to be compared against Std 55 s comfort zone. 26 Today's Paradigm for Heat Recovery - Part 2

27 Procedure (Cont d) 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 City 1A Miami 2A Houston 2B Phoenix 3A Atlanta 3B Los Angeles 3C San Francisco 4A Baltimore 4B Albuquerque 4C Seattle 5A Chicago 5B Denver 6A Minneapolis 6B Helena 7 Duluth 8 Fairbanks 27 Today's Paradigm for Heat Recovery - Part 2

28 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 reference d. 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 28 Today's Paradigm for Heat Recovery - Part 2

29 Procedure (Cont d) 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. 29 Today's Paradigm for Heat Recovery - Part 2

30 Results Higher Priority All Hours Within ASHRAE Std 55 s Comfort Humidity 2B K, 3B FR, 3C FROK, 4B FROK, 4C FROK, 5B FROK, 6B FROK, 8 FROK Climate Zones Lower Priority Significant Hours Above ASHRAE Std 55 s Comfort Humidity 1A FROK, 2A FROK, 2B FRO, 3A FROK, 3B OK, 4A FROK, 5A FROK, 6A FROK, 7 FROK 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. 30 Today's Paradigm for Heat Recovery - Part 2

31 Further Examples: Climate Zone 3C (SanFrancisco, 8760) 31 Today's Paradigm for Heat Recovery - Part 2

32 Climate Zone 4C (Seattle, Office) 32 Today's Paradigm for Heat Recovery - Part 2

33 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. 33 Today's Paradigm for Heat Recovery - Part 2

34 Benefits 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 Trade-Offs 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 34 Today's Paradigm for Heat Recovery - Part 2

35 Conclusions and Recommendations 1. Understand heat pipe s many benefits compared to enthalpic AAHX and how they apply to a particular project. 35 Today's Paradigm for Heat Recovery - Part 2

36 Conclusions and Recommendations 1. 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. 36 Today's Paradigm for Heat Recovery - Part 2

37 Conclusions and Recommendations 1. 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. 37 Today's Paradigm for Heat Recovery - Part 2

38 Conclusions and Recommendations 1. 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. 38 Today's Paradigm for Heat Recovery - Part 2

39 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 tombrooke@cox.net 39 Today's Paradigm for Heat Recovery - Part 2