Elara EngineeringDon McLauchlan, P.E.
Dustin Langille
2
2013 Energy Efficiency ExpoSeptember 10th, 2013
Unlock Energy Savings with
Heat Recovery
Presentation Outline
•Introduction
•Principles of Heat Recovery
•Types of Heat Recovery
•Case Studies
•Questions
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Elara Team
Don McLauchlan, Principal, P.E., C.E.M., LEED AP
−BSME
−Mechanical design engineer
−Mechanical design/build contractor
−Over 35 years in the industry
−Principle engineer on 12 LEED certified projects (4 Gold)
Dustin Langille, Senior Engineer
−MSME
−Mechanical design engineer
−Over 5 years in the industry
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Principles of Heat Recovery
The US DOE estimates that between 5 and 12 quadrillion BTU/year
is lost to waste heat1
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
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Waste Heat
Hydroelectric
Power
Wood Biofuels Waste Geothermal Wind Solar PV
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1US DOE: Waste Heat Recovery: Technology and Opportunities in U.S. Industry, March 2008
Principles of Heat Recovery
•General HX Equation: Q= ΔT(lmt) x U x A
•Terms:
•Approach temperature (T (hot in) – T (cold out)
•Turbulent/Transition/Laminar Flow (Reynold’s Number)
•Fouling Factor
•Log mean Temperature difference = (Ta – Tb)/ln( Ta/Tb)
•Counter Flow vs Parallel Flow
•Effectiveness
•Energy Balance
•Energy Penalty
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Principles of Heat Recovery
•Sources of “waste” heat:
−Building exhaust
−Boiler exhaust
−Process heat
−Simultaneous heating and cooling
−Heat rejected from AC/refrigeration equipment
•Recovered energy reduces heating and cooling loads
−Significant ongoing energy and money savings
•Also can reduce initial system size and costs
−Boilers
−Chillers
−Piping
−Pumps
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Example Types of Building Exhaust Heat Recovery
•Energy Recovery Wheels
•Plate and Membrane Heat Exchangers
•Run-around Coils
•Heat Pipe
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Energy Recovery Wheels
•A heat absorbing wheel that slowly
rotates between supply and exhaust air
streams
•Recovers sensible and latent energy
•Effective in summer operation and
dehumidification strategies
Datacenterknowledge.com
Cold OA
Warm
Exhaust
Picture: Datacenterknowledge.com
Cold OA
Warm
Exhaust
Winter Conditions
To Building
To Outside
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Energy Recovery Wheels
Advantages•Sensible and latent heat recovery
•High effectiveness
Disadvantages•Cannot be used where total separation of
exhaust and supply is required
•Wheel is susceptible to damage and
degradation
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Lessons Learned
◊ Questions
Picture: Ecobuildingpulse.com
Plate and Membrane Heat Exchanger
•Series of parallel plates providing heat transfer between exhaust and
supply air
•Generally only provide sensible heat transfer
−Plastic and paper systems allow for latent energy recovery as well
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Lessons Learned
◊ Questions
Picture: Water-foods.com
Plate and Membrane Heat Exchanger
Advantages•Can be used with contaminated air
•Potential for latent heat transfer
•Lower air-side pressure drop than energy recovery wheels
•Passive system (no moving parts)
Disadvantages•Physically large
•Less effective than energy recovery wheels
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Run-around Coils
•Piping loop between exhaust and
supply
•Requires installation of coils in
both exhaust and supply
ducts/plenums
•Water/glycol mixture
•Recovers sensible energy only
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Run-around Coils
Advantages•More cost effective when exhaust and supply are separated
by large distances
•System design flexibility for multiple exhaust/supply streams
•Flexibility of seasonally changing modes of operation
•System life and maintainability
•Up to 50% effective with careful coil and pump selections
Disadvantages•Circulation pump uses energy
•Typically no latent heat transfer
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Run-around Coils
Design Comments
•Critical coil selections
•Variable speed pumping
•Controls
•Freeze protection
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
3 Coil Run-around
•Run-around coil providing
pre-cooling and reheating for
dehumidification
•Pre-cool coil can double as
heat recovery coil
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Reheat
Coil
Main
Cooling
Coil
Precool
Coil
Heat Pipe
•Piping loop between exhaust and supply similar to run-around coil using
refrigerant instead of water
•Refrigerant vaporizes in one coil, gathering heat energy, and releases
energy in the supply coil when it condenses
•Pressure within loop can be adjusted to properly facilitate phase change
•Recovers sensible heat only
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Case Study: Park Alexandria
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Desuperheater heat recovery for
domestic hot water heating
•Heat exchanger on chiller recovers
heat from hot refrigerant gas
•Preheat tanks store hot water
•Nearly entire summer DHW load met
•Improved chiller efficiency via lower
head pressure
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Implementation Cost: $90,000
Estimated Annual Savings: $26,000
Simple Payback: 3.5 Years
Pre
heat Tank T
em
pera
ture
•Exhaust air run-around recovering
approximately 40% of the exhaust heat
energy
•Significantly reduce the energy consumed
by the existing makeup air units
Implementation Cost: $183,200
Annual Savings: $127,010
Simple Payback: 1.44 Years
Case Study: Heritage at Millennium Park
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Heat recovery wheel with bypass and return air
path for additional humidity control
Case Study: Data Center Heat Recovery
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
•Campus data
center will provide
100% of building
heating needs
with use of water-
to-water heat
pump
Main Air Handlers -
Heating Mode
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Case Study: Loyola Information Commons
•Combined three coil
run-around and
exhaust heat
recovery
•Variable speed
pump for optimized
heat recovery
◊ Introduction
◊ Principles
◊ Types
◊ Case Studies
◊ Questions
Main Air Handlers -
Cooling Mode •Summer mode
provides
dehumidification for
radiant slabs