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Objectives • Cooling Cycles – Examples • Cooling system components • Refrigerants
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Objectives

Feb 24, 2016

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Objectives. Cooling Cycles Examples Cooling system components Refrigerants. Subcooling and Superheating. Refrigerant may be subcooled in condenser or in liquid line Temperature goes below saturation temperature Refrigerant may be superheated in evaporator or in vapor (suction) line - PowerPoint PPT Presentation
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Page 1: Objectives

Objectives

• Cooling Cycles – Examples

• Cooling system components

• Refrigerants

Page 2: Objectives

Subcooling and Superheating

• Refrigerant may be subcooled in condenser or in liquid line– Temperature goes below saturation

temperature • Refrigerant may be superheated in

evaporator or in vapor (suction) line– Temperature goes above saturation

temperature

Page 3: Objectives

Two stage systems

Page 4: Objectives

Multistage Compression Cycles

• Combine multiple cycles to improve efficiency– Prevents excessive compressor discharge

temperature– Allows low evaporating temperatures

(cryogenics)

Page 5: Objectives

Example 1

• R-22 condensing temp of 30 °C and evaporating temp of 0°C

• Determinea) qcarnot wcarnot

b) COPcarnot

c) ηR

Page 6: Objectives

Example 2

• R-22 condensing temp of 60 °C and evaporating temp of 0°C

• Determine the ηR

Page 7: Objectives

Example 3• Two stage compressor • R-22 condensing temp of 60 °C • Evaporating temp of compressor A

30°C and for compressor B 0°C.

• Determine the ηR

Assume that condenser temperature for compressor B is the same like evaporation temperature of compressor A

Page 8: Objectives

Systems: residential

Indoor Air

Outdoor Air

Page 9: Objectives

Large building cooling systems(chillers with cooling towers)

Cooling tower

25oC

P

Weather parameters

DBT=30oCWBT=20oC

35oC

11oC

Waterrefrigerant

6oC

Page 10: Objectives

System componentsLarge building system

Plate heat exchanger

Water formcooling tower

Water tocooling tower

6oC 11oC

Water to building

Water from building

25oC 35oC

Page 11: Objectives

Chiller

Page 12: Objectives

Compressors

Page 13: Objectives

Reciprocating compressor

Page 14: Objectives

Scroll compressor

http://www.youtube.com/watch?v=f_6xolDoqs0

Page 15: Objectives

Screw compressor

http://www.youtube.com/watch?v=xO7IhhzImMU&feature=related

Page 16: Objectives

Rotary Compressor

Page 17: Objectives

Refrigerants

Page 18: Objectives

What are desirable properties of refrigerants?

• Pressure and boiling point• Critical temperature• Latent heat of vaporization• Heat transfer properties• Viscosity• Stability

Page 19: Objectives

In Addition….

• Toxicity• Flammability• Ozone-depletion• Greenhouse potential• Cost• Leak detection• Oil solubility• Water solubility

Page 20: Objectives

Refrigerants

• What does R-12 mean?• ASHRAE classifications• From right to left ←

– # fluorine atoms– # hydrogen atoms +1– # C atoms – 1 (omit if zero)– # C=C double bonds (omit if zero)

• B at end means bromine instead of chlorine• a or b at end means different isomer