1. Important variables Water: Air: Conversion:
- Use ASHRAE tables I gave you:
- You can fine them online
(be careful, not all online converters are correct)

2. Objective Finish cooling & energy storage systems
Define Building Zones
Learn about air handling and water distribution systems

3. Absorption Cycle Water is typical refrigerant
Strong vacuum - ~0.116 psi or MPa
Boiling point of water?
Differences from vapor compression
No compressor
Chemical (e.g. LiBr - hygroscopic)
Absorbs water vapor turns it into a liquid
Regenerated by removing water
Requires heat

4. Absorption Cycle
Strong vacuum Refrigerant: water Absorber: lithium bromide
Replace compressor

6. Evaporative Cooling Wet media/water spray – direct
Raise absolute humidity, lowers temperature of conditioned air
Cooling tower – indirect
Cools through a heat exchanger
Lowers temperature, does not affect absolute humidity
Can directly cool air in cold weather

7. Evaporative Cooling

8. Convert Cooling machine (DX machine) to heat pumps
Compressor Cooling
Sorption cooling
Evaporative cooling
DX machine
Chiller
Evaporative Chiller
Air Cooled Condenser
Water Cooled Condenser
Convert Cooling machine (DX machine) to heat pumps

9. Daily distribution of cooling load

10. Thermal Storage
Make ice/chilled water at times of low demand or low energy prices
Store water in insulated container
Can be used to reduce overall demand
Water can be used as secondary water source for fire protection
Ice/snow

11. Thermal Storage

12. Thermal storage

13. Ventilation Air-flow in Buildings

14. Zones In building How to define the zone in building
Based on cooling/heating load requirement
Based on ventilation requirement
Based on use of buildings
– different apartments deferent zones

15. Air Handling Units (AHU) Control of air Systems
Provide conditioned air
Heating, cooling, humidification, dehumidification
Ventilation
Provide fresh air, remove contaminated air

16. Air Handling Unit (AHU)
Roof top AHU
Gas/Electric Heater
to building
Fan
air from building
fresh air
Evaporator
filter
mixing
AHU schematic
Exhaust
From room
Return fan
flow control dampers
Supply fan
Compressor and Condenser
Fresh air
To room
Outdoor air
hot water
cool water

17. Air Handling Units (AHS)
Equipment For AHU:
Fans
Cooling and heating coils
Combustion heat exchangers
Filtration
Dampers, controls, mixing valves
Humidification: steam/spray
Dehumidification: cooling coil/desiccant
Noise control

18. Control of air Systems Vary temperature, constant flow
Constant temperature, vary flow
Vary temperature, vary flow

19. How does a residential thermostat work?
Calculates difference between actual temperature and required temperature and adjusts furnace/AC output accordingly
Measures temperature continuously and turns equipment on and off when temperature is different from set point temperature
Measures temperature continuously and turns equipment on and off when temperature is outside of specified bounds
Calculates difference between actual temperature and required temperature and adjusts the velocity of the fan (flow-rate) accordingly

20. Constant Temperature, Variable Volume
On-off systems
Residential and small commercial
Vary volume by turning system on and off

21. Constant Air Volume Single zone constant air volume
Fan always runs
Vary temperature of air in response to space thermostat
Single zone constant air volume with reheat
Often used for precise humidity control
Multizone constant air volume with reheat
Good humidity control, flexible
Not very efficient

22. Constant Volume – temperature control
Proportional control or Proportional Integral control
Thermostat measure: ΔT = T set point – T zone air
Send the signal to the valve of cooling/heating coil

23. Multizone constant air volume with reheat
55°F
62°F
Require less
cooling

24. Variable Air Volume Single zone VAV Multizone VAV Can also use reheat
Varies air flow based on room thermostat
Multizone VAV
Central chilled air supply
Zone thermostats control flow to each zone
Can also use reheat
Still need to provide adequate air flow for ventilation and for comfort
Smaller energy penalty than CAV

25. VAV terminal

26. Multizone VAV
55°F
Vary the flow

27. Dual-Duct Systems Can be VAV or CAV
Two plenums with chilled air and heated air
Zone thermostats control ratio
Separate duct
for each zone

28. Reading Assignment Tao and Janis Chapter 3 Chapter 6 (from 6.1 to 6.7)
Sections: (including )
Chapter 6 (from 6.1 to 6.7)

29. Homework Assignment 4
Table 1 Results of cooling load calculation and required amount of fresh air for ventilation
Zone 1
Zone 2
Zone 3
Whole building
Sensible cooling load for zone
Time when the max cooling load appear
41000 Btu/h
at 4 PM
45000 Btu/h
at 6 PM
27000 Btu/h
at 8 AM
92000 Btu/h
Sensible cooling load for critical hour for whole building (6 PM)
37000 Btu/h
9000 Btu/h
Latent cooling load (internal sources + infiltration)
5400 Btu/h
5200 Btu/h
16000 Btu/h
Required amount of fresh air based on number of occupants
240 CFM
(12 occupants)
520 CFM
(26 occupants)
1000 CFM
(50 occupants)

30. Homework Assignment 4 Supply air 55°F Recirculation air 76°F
Fresh air (Dallas, TX) DBT=102°F