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Energy Recovery in Air Handlers

Energy Recovery in Air Handlers. Delivered by: Jason Richwine 16 April 2012 Columbus, OH. Energy Recovery in Air Handlers Intro. Standards and Definitions Three Popular Technologies Wheels Plates Pipes Summary. Energy Recovery in Air Handlers Standards & Definitions.

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Energy Recovery in Air Handlers

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

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

  3. Energy Recovery in Air Handlers Standards & Definitions

  4. Energy Recovery in Air Handlers Standards & Definitions ASHRAE 62.1-2010 • 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?

  5. Energy Recovery in Air Handlers Standards & Definitions ASHRAE 90.1-2010 • 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?

  6. Energy Recovery in Air Handlers Standards & Definitions ASHRAE 90.1-2010 • 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

  7. Energy Recovery in Air Handlers Standards & Definitions AHRI 1060 • 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 comply • Some manufacturers choose not to participate

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

  9. Energy Recovery in Air HandlersWheels

  10. Energy Recovery in Air HandlersWheels • 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. Energy Recovery in Air HandlersWheels

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

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

  15. Energy Recovery in Air HandlersWheels • 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. Energy Recovery in Air Handlers Plate Heat Exchangers

  17. Energy Recovery in Air HandlersPlate 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. Energy Recovery in Air HandlersPlate 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. Energy Recovery in Air HandlersPlate Heat Exchangers • Configurations • Vertical or horizontal orientation • Various blow-thru and draw-thru fan combinations • Bypass arrangements

  20. Energy Recovery in Air HandlersPlate Heat Exchangers • Configurations • Multiple Heat Exchangers • Counter-flow arrangements

  21. Energy Recovery in Air Handlers Heat Pipes

  22. Energy Recovery in Air HandlersHeat 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. Energy Recovery in Air HandlersHeat 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. Energy Recovery in Air HandlersHeat 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. Energy Recovery in Air HandlersHeat 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 orhighly obnoxious contaminants

  26. Energy Recovery in Air HandlersTechnology Comparison

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