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

11. Vapor Compression Cycle
Expansion Valve

13. Efficiency First Law Second law Coefficient of performance, COP
COP = useful refrigerating effect/net energy supplied
COP = qr/wnet
Second law
Refrigerating efficiency, ηR
ηR = 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