Comparative Design Considerations and other notions specific to Industrial Refrigeration ASHRAE TriC

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Comparative Design Considerations and other
notions specific to Industrial Refrigeration
ASHRAE - Tri-County Chapter February 20, 2007
chapter meeting

• Refrigeration DID come first, and other
  declarations from the Cold side!

Ted Kohlenberger, Sales Engineer Refrigeration
Equipment Specialist Company (RESCO) Previously
Engineering Manager for Kohlenberger Associates
Consulting Engineers (KACE)
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Presentation Overview...

• Review of the industrial refrigeration
  environment
• General system design considerations.
• The Cheap Cold Phenomena
• Can IC gas engine drives (GEDs) play a role?
• Economic recap for cold storage warehouse model
  with comparative refrigeration systems
• Some conclusions...

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Industrial Refrigeration - A Different Animal...

• Process and product critical systems including
  cold storage, food processing chemical
  manufacture.
• Generally requires highest system reliability and
  performance.
• Systems generally larger, frequently 100 HP or
  greater. Some local systems exceed 4,000 HP
• Refrigeration utility generally represents
  largest overhead or recurring cost, next to labor
  cost.
• Field-Erected systems most common, although
  pre-fabricated multiple compressor rack- type
  systems have been gaining popularity,
  particularly when ammonia considered to be
  prohibitive.

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Industrial Refrigeration Design Criteria Basics

• Generous use of ammonia (R-717/Group B) primarily
  in larger systems.
• Use of R-22 (Group A) losing steam due to MP/EPA
  phaseout of HCFCs
• Open driven screw compressors are the mainstay.
• Evaporators normally flooded or circulated, not
  DX
• Condensing is generally water-based, frequently
  using evaporative condensers.
• System piping made of generally ferrous
  materials.
• Systems require rated machine room, with generous
  ventilation, S or H occupancy vapor detection.
• Ammonia requires additional safety devices, means
  of mechanical diffusion, liquid zone isolation,
  alarms, etc.

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System Design - Fighting Off Mediocrity...

• Seems like we reduce First Cost at all Cost!
• Design it cheap cold - most anybody can do
  this
• Operating Costs? We ALL claim importance
• Rising electrical rates squeeze everyone - whew?
• Relatively little use of pressure staging for low
  temp. systems - Mature design techniques for
  operating economy and happy shareholders. See
  ASHRAE Refrigeration Handbook.
• Not enough emphasis on lowering condensing
  pressures/raising suction pressures for enhanced
  energy savings.
• Should make better use of industrial controls
  technology supervision/management/control.

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Thermodynamic Cycle Diagram for Refrigeration
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SCHEME A - Single Stage/Electric Motor
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SCHEMES B C - Two Stage, motor or IC engine
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What about IC Engine Drives This is no ordinary
motor...

• IC engines have enjoyed selective popularity as
  industrial prime mover
• AQMD permitting in Southern California is OK.
• IC engine utilizes alternative less costly
  fuel
• Waste heat recovery opportunities include
• pre-heating of boiler feed water
• pre-heat clean up water (food processing)
• process heating/drying.
• Gas Company incentives available!
• engines in conjunction with electric motors
  (Hybrid) promote enhanced utility utilization and
  allow legal exploitation of utility rate
  structures.

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Basic IC engine application criteria...

• Size of existing or proposed refrigeration
  system?
• Consider for system sizes exceeding 150 bHP
• Consider when size requires multiple compressors.
• Evaluate prime mover mix select hybrid design
  which maximizes prime mover economy for given
  rate schedule.
• IC engines for peak electrical load shedding
• Electric motors for low load, weekend off-peak
  times
• Consider waste heat streams for added economy and
  utilization.
• Jacket water/oil cooling loop is low grade
  energy - below 250 F
• Exhaust is high grade energy - above 350 F
  for steam produc.

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Sample Economics for a Model Cold Storage
Facility...

• Typical cold storage facility - 80,000 100,000
  S.F. _at_ -15 F with 10,000 S.F. dock _at_ 40 F
• Highlights conventional/mature techniques for
  utility savings in cold storage design.
• Scheme A (Base) - single stage compression using
  motors drives, liquid injection oil cooling, 15 F
  TD coil split and 96 F condensing temperature.
• Scheme B/C (Enhanced) - two stage compression
  using motors and/or IC engines, water cooled or
  thermo-siphon oil cooling, 7.5 - 10 F TD coil
  split and 85 F condensing temperature.

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Typical Freezer Warehouse
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Recap Spreadsheet - Owning Operating Cost
Analysis
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Some Conclusions...

• You CAN SHOULD design better than Cheap and
  Cold
• First cost at All costs cant sustain industrial
  refrigeration system construction forever.
• Applying several mature technologies to new and
  existing systems could save 10 - 30 in annual
  energy!
• Creative and efficient refrigeration system
  design saves valuable resources, returns value
  and makes sense!
• It is our responsibility as technical
  professionals to argue on behalf of the good
  system design moreover, educating our clients on
  the alternatives while practicing and encouraging
  design excellence.