energy efficient process cooling n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Energy-Efficient Process Cooling PowerPoint Presentation
Download Presentation
Energy-Efficient Process Cooling

Loading in 2 Seconds...

play fullscreen
1 / 29

Energy-Efficient Process Cooling - PowerPoint PPT Presentation


  • 162 Views
  • Uploaded on

Energy-Efficient Process Cooling. Process Cooling Systems . Cooling systems Cooling tower Water-cooled chiller Air-cooled chiller Absorption chiller Compressed air cooling Cooling costs assume: Electricity: $0.10 /kWh Natural gas: $10 /mmBtu Water: $6 /thousand gallons.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Energy-Efficient Process Cooling' - harsha


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
process cooling systems
Process Cooling Systems
  • Cooling systems
    • Cooling tower
    • Water-cooled chiller
    • Air-cooled chiller
    • Absorption chiller
    • Compressed air cooling
  • Cooling costs assume:
    • Electricity: $0.10 /kWh
    • Natural gas: $10 /mmBtu
    • Water: $6 /thousand gallons
cooling tower
Cooling Tower
  • 500-ton tower delivers 7.5 mmBtu/hr
  • Ppump = 18 kW Pfan = 20 kW Water = 120 gal/mmBtu
  • Unit cost of cooling = $1.22 /mmBtu
water cooled chiller
Water-Cooled Chiller
  • E/Q = 0.8 kW/ton = 67 kWh/mmBtu
  • Unit cost of cooling = $6.70 /mmBtu
air cooled chiller
Air-Cooled Chiller
  • E/Q = 1.0 kW/ton = 83 kWh/mmBtu
  • Unit cost of cooling = $8.30 /mmBtu
absorption chiller
Absorption Chiller
  • E/Q = 1 Btu-heat / Btu-cooling Eff-boiler = 80%
  • Unit cost of cooling = $12.50 /mmBtu
open loop water cooling
Open-Loop Water Cooling
  • DT = 10 F V = 12,000 gallons / 1 mmBtu
  • Unit cost of cooling = $72 /mmBtu
compressed air cooling
Compressed Air Cooling
  • 150 scfm at 100 psig to produce 10,200 Btu/hr cooling
  • 4.5 scfm per hp
  • Unit cost of cooling = $272 /mmBtu
relative process cooling costs
Relative Process Cooling Costs

Near order of magnitude difference in costs!

cooling energy saving opportunities
Cooling Energy Saving Opportunities
  • Reducing end use cooling loads and temperatures
    • Add insulation
    • Add heat exchangers
    • Improve heat transfer
  • Improving efficiency of distribution system
    • Reducing friction using large smooth pipes
    • Avoiding mixing
    • Employing variable-speed pumping
  • Improving efficiency of primary cooling units
    • Use cooling tower when possible
    • Use water-cooled rather than air-cooled chiller
    • Use variable speed chillers
end use add insulation
End Use: Add Insulation
  • Insulation:
    • Reduces heat transfer into cooled tanks & piping
    • Decreases exterior condensation
  • Even at small temperature differences insulating cold surfaces is generally cost effective
end use continuous process with sequential heating and cooling
End Use: Continuous Process with Sequential Heating and Cooling

Current:

Qh1 = 100

Qc1 = 100

With HX:

If Qhx = 30,

Qh2 = 70

Qc2 = 30

HX reduces both heating and cooling loads!

end use batch processes with discrete heating and cooling
End Use: Batch Processes with Discrete Heating and Cooling

Cost effective to transfer heat between processes, whenever the processes that need cooling are 10 F higher than the process that need heating

end use batch processes with discrete heating and cooling1
End Use: Batch Processes with Discrete Heating and Cooling

Add Heat Exchangers

T = 145 F

Requires Cooling

T = 120 F

Requires Heating

end use optimize heat exchanger network pinch analysis
End Use: Optimize Heat Exchanger Network (Pinch Analysis)

For multiple heating and cooling opportunities, optimize heat exchanger network using Pinch Analysis.

end use improve heat transfer
End Use: Improve Heat Transfer

Cross flow cooling of extruded plastic with 50 F chilled water from chiller

end use improve heat transfer1
End Use: Improve Heat Transfer

Counter flow

Cross flow

Parallel flow

e = 0.78

e = 0.62

e = 0.50

NTU = 3 and Cmin/Cmax = 1

cooling product cross vs counter flow
Cooling Product: Cross vs Counter Flow

Cross Flow: e = 0.69

  • Tw1 = 50 F
  • Tp = 300 F
  • Mcpmin = 83.2 Btu/min-F
  • Q = e mcpmin (Tp – Tw1) = 0.69 83.2 (300 – 50)
  • Q = 14,352 Btu/min

Counter Flow: e = 0.78

  • Q = 14,352 Btu/min
  • Tp = 300 F
  • Mcpmin = 83.2 Btu/min-F
  • Q = e mcpmin (Tp – Tw1) = 14,352 Btu/min = 0.78 83.2 (300 – Tw1)
  • Tw1 = 79 F
cooling product cross vs counter flow1
Cooling Product: Cross vs Counter Flow

Cooling towers can deliver 79 F

water much of the year using 1/10

as much energy as chillers!

distribution system avoid mixing
Distribution System: Avoid Mixing

Separate hot and cold water tanks

Lower temperature, less pumping energy to process

Higher temperature, less fan energy to cooling tower

primary cooling use cooling tower when possible
Primary Cooling: Use Cooling Tower When Possible

Cooling towers can deliver water at about outside air temperature

primary cooling use cooling tower when possible1
Primary Cooling: Use Cooling Tower When Possible

CoolSim reports number hours CT delivers target temperature.

Model cooling

tower performance

primary cooling use water cooled chillers for year round loads
Primary Cooling: Use Water Cooled Chillers for Year Round Loads

E/Q (Air-cooled) = 1.0 kW/ton E/Q (Water-cooled) = 0.8 kW/ton

ammonia refrigeration systems
Ammonia Refrigeration Systems

Multiple compressors, stages, evaporative condensers

ammonia refrigeration savings opportunities
Ammonia Refrigeration Savings Opportunities
  • Reclaim heat
  • Variable head-pressure control