1. Energy Recovery in Air Handlers Delivered by:Jason Richwine 16 April 2012Columbus, OH

2. Energy Recovery in Air Handlers Intro Standards and Definitions Three Popular Technologies Wheels Plates Pipes Summary 2

3. 3 Energy Recovery in Air Handlers Standards & Definitions

4. 4 Requires outdoor air (OA) be used for ventilation when it is not polluted Defines amounts of OA needed for various applications What’s the problem with ventilating? ASHRAE 62.1-2010

5. 5 Energy Recovery in Air Handlers Standards & Definitions 90.1 defines limits for building energy consumption ASHRAE plans to develop tools to design net-zero energy buildings (NZEB) by 2020, so NZEBs will be standard by 2030 How can we have good ventilation and limit energy use? ASHRAE 90.1-2010

6. 6 Energy Recovery in Air Handlers Standards & Definitions Exhaust air (EA) energy recovery is required when: Many commercial comfort applications don’t require energy recovery (<30% OA) Energy recovery may still make economic sense *See Exceptions 6.5.6.1.a – 6.5.6.1.j ASHRAE 90.1-2010

7. 7 Energy Recovery in Air Handlers Standards & Definitions Voluntary Standard Defines test, rating, and minimum data requirements for published ratings, marking and nameplate data Helps you compare performance among manufacturers AHRI Directory provides list of manufacturers that complyAHRI Directory Some manufacturers choose not to participate AHRI 1060

8. Solution YC - YORK Custom Air Handlers8 Energy Recovery in Air Handlers Three Popular Technologies

9. 9 FeatureWheelPlate HXHeat Pipe PerformanceBestVery goodGood Base Price (media only)Middle rangeLowestHighest Price (packaged in AHU)Moderate across all unit sizesLowest on smaller units, moderate-high on larger units Highest in smaller units, moderate on larger units Performance/PriceBestVery goodGood Heat Transfer Effectiveness Sensible: 50-80% Total: 55-85% Sensible: 50-80% Total: 55-85% Sensible: 45-65% Total: N/A Exchanger SizeMost compactLargestCompact, flexible shape Cross-contamination Levels Highest cross-contamination Minimized with purge No cross-contamination up to 3” w.g. No cross-contamination Application TemperatureUp to 150 deg FUp to 392 deg. FUp to 450 deg. F Corrosion ResistanceHigh - polymers Medium - aluminum High - polymers Medium - aluminum High Cleaning RequirementsDry: Vacuum or compressed air Wet: Low pressure rinse Dry: Vacuum Wet: High pressure rinse Wet: High pressure rinse MaintenanceBearings, belts, motors, cleaning Cleaning Airflow Limitation~ 35,000 CFMNo limit Energy Recovery in Air Handlers Wheels

10. 10 Energy Recovery in Air Handlers Wheels What Are They? Rotating heat exchangers that transfer sensible and latent heat to precondition ventilation air Material types Composite (polymer, fiber) Aluminum Benefits High effectiveness Low pressure drops Applications Many commercial applications where isolation of airstreams is not required

11. 11 AluminumPolymer or Fiber Heat transferHigh thermal conductionLow thermal conduction Why it mattersRequires thermal mass More material means thick (typ. 4”-12”), heavier wheel Less material means thin (typ. 3”-6”), lighter wheel Desiccant typeMolecular sieve or polymer coating Impregnated Silica gel Why it mattersSprayed or dipped coatings may separate from substrate Molecular sieve recovers latent heat well at low %RH Desiccant is integral with substrate Latent heat transfer increases as %RH increases Energy Recovery in Air Handlers Wheels

12. 12 Energy Recovery in Air Handlers Wheels 30%-35% RH is typical for winter-time non-humidified indoor air Desiccant Effectiveness

13. 13 Energy Recovery in Air Handlers Wheels Cross-contamination and Purge Cross-contamination occurs when air leaks past separators and seals, or is carried in the wheel as it rotates from the EA to the OA We want to limit leakage from EA to OA A mechanical purge directs OA to the EA section to flush air out the exhaust, limiting cross-contamination RA that entered wheel prior to the purge section has time to exit wheel on the exhaust side

14. 14 Energy Recovery in Air Handlers Wheels Blow-thru Supply Blow-thru Exhaust Advantage Minimal leakage when supply and exhaust pressures are similar Precaution Design for appropriate pressure differences to manage leakage Blow-thru Supply Draw-thru Exhaust Advantage Minimal leakage from exhaust to supply Precaution OA can short-circuit to EA wasting fan energy Draw-thru Supply Draw-thru Exhaust Advantage Minimal leakage when supply and exhaust pressures are similar Precaution Design for appropriate pressure differences to manage leakage Draw-thru Supply Blow-thru Exhaust Advantage None Precaution Don’t do it. Too much EA will leak into OA.

15. 15 Energy Recovery in Air Handlers Wheels Frost Control Frost can form on wheels in the winter when warm moist return air contacts very cold wheel media Four types of control On/Off – least expensive and least complicated, but turns the wheel off when you most want to recover heat Bypass – some OA bypasses wheel. This reduces wheel capacity preventing EA from reaching saturation. Requires good mixing to prevent temperature stratification. Preheat – install heating coil in RA or OA. Heating RA decreases RA %RH to reduce frost risk, and increases temperature differences to improve wheel performance. Variable speed control – slowing the wheel reduces heat transfer rate, requires sophisticated controls, and may not work well on certain wheels *See ASHRAE Journal March 2012 page 46 for good article on energy wheel control

16. 16 FeatureWheelPlate HXHeat Pipe PerformanceBestVery goodGood Base Price (media only)Middle rangeLowestHighest Price (packaged in AHU)Moderate across all unit sizesLowest on smaller units, moderate-high on larger units Highest in smaller units, moderate on larger units Performance/PriceBestVery goodGood Heat Transfer Effectiveness Sensible: 50-80% Total: 55-85% Sensible: 50-80% Total: 55-85% Sensible: 45-65% Total: N/A Exchanger SizeMost compactLargestCompact, flexible shape Cross-contamination Levels Highest cross-contamination Minimized with purge No cross-contamination up to 3” w.g. No cross-contamination Application TemperatureUp to 150 deg FUp to 392 deg. FUp to 450 deg. F Corrosion ResistanceHigh - polymers Medium - aluminum High - polymers Medium - aluminum High Cleaning RequirementsDry: Vacuum or compressed air Wet: Low pressure rinse Dry: Vacuum Wet: High pressure rinse Wet: High pressure rinse MaintenanceBearings, belts, motors, cleaning Cleaning Airflow Limitation~ 35,000 CFMNo limit Energy Recovery in Air Handlers Plate Heat Exchangers

17. 17 Energy Recovery in Air Handlers Plate Heat Exchangers What is a plate heat exchanger? Fixed plate heat exchangers transfer sensible and sometimes latent heat Cross-flow design with airstreams passing at right angles Keeps air streams segregated under normal conditions Construction Types Composite (polymer) Aluminum

18. 18 Energy Recovery in Air Handlers Plate Heat Exchangers Benefits High transfer efficiencies Segregated airstreams No moving parts No electrical connections Applications Commercial and industrial applications where segregation of airstreams is desired – pools, labs, processes, etc. Do not use when EA contains dangerous contaminants

19. 19 Energy Recovery in Air Handlers Plate Heat Exchangers Configurations Vertical or horizontal orientation Various blow-thru and draw-thru fan combinations Bypass arrangements

20. 20 Energy Recovery in Air Handlers Plate Heat Exchangers Configurations Multiple Heat Exchangers Counter-flow arrangements

21. 21 FeatureWheelPlate HXHeat Pipe PerformanceBestVery goodGood Base Price (media only)Middle rangeLowestHighest Price (packaged in AHU)Moderate across all unit sizesLowest on smaller units, moderate-high on larger units Highest in smaller units, moderate on larger units Performance/PriceBestVery goodGood Heat Transfer Effectiveness Sensible: 50-80% Total: 55-85% Sensible: 50-80% Total: 55-85% Sensible: 45-65% Total: N/A Exchanger SizeMost compactLargestCompact, flexible shape Cross-contamination Levels Highest cross-contamination Minimized with purge No cross-contamination up to 3” w.g. No cross-contamination Application TemperatureUp to 150 deg FUp to 392 deg. FUp to 450 deg. F Corrosion ResistanceHigh - polymers Medium - aluminum High - polymers Medium - aluminum High Cleaning RequirementsDry: Vacuum or compressed air Wet: Low pressure rinse Dry: Vacuum Wet: High pressure rinse Wet: High pressure rinse MaintenanceBearings, belts, motors, cleaning Cleaning Airflow Limitation~ 35,000 CFMNo limit Energy Recovery in Air Handlers Heat Pipes

22. 22 Energy Recovery in Air Handlers Heat Pipes What is a heat pipe? Refrigerant filled heat exchangers that transfer sensible heat Hollow cylinders/tubes filled with a refrigerant How heat pipes work Heat is absorbed in the evaporating section and boils the liquid refrigerant Vapor moves to the condensing portion via convection Heat is released from the condensing part of the pipe and vapor condenses Liquid returns – by gravity, wick, or pump – to the evaporating section

23. 23 Energy Recovery in Air Handlers Heat Pipes Heat Pipes for Dehumidification Two sections: pre-cooling and reheat Warm air passes through first section and evaporates refrigerant Refrigerant vapor moves to the condenser Pre-cooled air passes through cooling coil which cools it and removes moisture Over-cooled air passes through condenser and is reheated to comfortable temperature Refrigerant condenses and flows back to evaporator Entire process accomplished using minimal additional energy Result is ability to remove 50% - 100% more moisture than a cooling coil alone

24. 24 Energy Recovery in Air Handlers Heat Pipes Energy Recovery of EA to SA Side by side heat pipes Fluid moves in a continuous one directional flow through individual three dimension circuits

25. 25 Energy Recovery in Air Handlers Heat Pipes Benefits Phase change provides increased efficiency compared to glycol runaround No cross-contamination of airstreams Accommodates air streams located further apart Applications Commercial and industrial applications where plates are impractical When exhaust air contains dangerous or highly obnoxious contaminants

26. 26 FeatureWheelPlate HXHeat Pipe PerformanceBestVery goodGood Base Price (media only)Middle rangeLowestHighest Price (packaged in AHU)Moderate across all unit sizesLowest on smaller units, moderate to high on larger units Highest in smaller units, moderate on larger units Performance/PriceBestVery goodGood Heat Transfer Effectiveness Sensible: 50-80% Total: 55-85% Sensible: 50-80% Total: 55-85% Sensible: 45-65% Total: N/A Exchanger SizeMost compactLargestVery compact Very flexible shape Cross Contamination Levels Highest contamination Minimized with purge No contamination up to 3 in. wg.No contamination Application TemperatureUp to 150 deg FUp to 392 deg. FUp to 450 deg. F Corrosion ResistanceHigh - polymers Medium - aluminum MediumHigh Cleaning RequirementsDry: Vacuum or compressed air Wet: Low pressure rinse Wet: High pressure rinse MaintenanceBearings, belts, motorsNone Airflow Limitation~ 35,000 CFMNo limit Energy Recovery in Air Handlers Technology Comparison