Objectives

1
Objectives

• AHU processes
• - HW2
• Cooling cycles

2
Air conditioning
3
Single-Zone Systems

• Zone any space with a thermostat

4
Recirculation
5
Reheat
6
Evaporative Cooler
7
Air-to-air heat exchanger
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9
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10
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Vapor Compression Cycle
Expansion Valve
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Efficiency

• First Law
• Coefficient of performance, COP
• COP useful refrigerating effect/net energy
  supplied
• COP qr/wnet
• Second law
• Refrigerating efficiency, ?R
• ?R COP/COPrev
• Comparison to ideal reversible cycle

14
Carnot Cycle

• No cycle can have a higher COP
• All reversible cycles operating at the same
  temperatures (T0, TR) will have the same COP
• For constant temp processes
• dq Tds
• COP TR/(T0 TR)

15
Get Real

• Assume no heat transfer or potential or kinetic
  energy transfer in expansion valve
• COP (h3-h2)/(h4-h3)
• Compressor displacement mv3