Download presentation

Presentation is loading. Please wait.

1
**Energy-Efficient Process Cooling**

2
**Process 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

3
**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

4
Chillers 4

5
**Water-Cooled Chiller E/Q = 0.8 kW/ton = 67 kWh/mmBtu**

Unit cost of cooling = $6.70 /mmBtu

6
**Air-Cooled Chiller E/Q = 1.0 kW/ton = 83 kWh/mmBtu**

Unit cost of cooling = $8.30 /mmBtu

7
**Absorption Chiller E/Q = 1 Btu-heat / Btu-cooling Eff-boiler = 80%**

Unit cost of cooling = $12.50 /mmBtu

8
**Open-Loop Water Cooling**

DT = 10 F V = 12,000 gallons / 1 mmBtu Unit cost of cooling = $72 /mmBtu

9
**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

10
**Relative Process Cooling Costs**

Near order of magnitude difference in costs!

11
**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

12
**End Use: Add Insulation**

Reduces heat transfer into cooled tanks & piping Decreases exterior condensation Even at small temperature differences insulating cold surfaces is generally cost effective

13
**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!

14
**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

15
**End Use: Batch Processes with Discrete Heating and Cooling**

Add Heat Exchangers T = 145 F Requires Cooling T = 120 F Requires Heating

16
**End Use: Optimize Heat Exchanger Network (Pinch Analysis)**

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

17
**End Use: Improve Heat Transfer**

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

18
**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

19
**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) = (300 – 50) Q = 14,352 Btu/min Counter Flow: e = 0.78 Q = e mcpmin (Tp – Tw1) = 14,352 Btu/min = (300 – Tw1) Tw1 = 79 F

20
**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!

21
**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

22
**Primary Cooling: Match Cooling Source to End Use**

23
**Primary Cooling: Use Cooling Tower When Possible**

Cooling towers can deliver water at about outside air temperature

24
**Primary Cooling: Use Cooling Tower When Possible**

CoolSim reports number hours CT delivers target temperature. Model cooling tower performance

25
**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

26
**Primary Cooling: Stage Multiple Constant Speed Chillers**

27
**Primary Cooling: Use Variable-Speed Chiller**

28
**Ammonia Refrigeration Systems**

Multiple compressors, stages, evaporative condensers

29
**Ammonia Refrigeration Savings Opportunities**

Reclaim heat Variable head-pressure control

Similar presentations

OK

1 Medical Office Building. 2 Occupancy – 400 persons 8 a.m. – 5 p.m. Monday - Friday Building Characteristics Three stories 40,000 square feet (200’ x.

1 Medical Office Building. 2 Occupancy – 400 persons 8 a.m. – 5 p.m. Monday - Friday Building Characteristics Three stories 40,000 square feet (200’ x.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on accounting standard 12 Ppt on history of mathematics Ppt on effect of western culture on indian youth Presentation ppt on motivation and emotion Ppt on conference call etiquette you need to know Ppt on review of related literature in research Ppt on how google search engine works Slide show view ppt on mac Ppt on crash fire tender fire Ppt on history of badminton sports