1. Objective Revie the Cooling Cycle Learn about air distribution systems
Define Building Zones
Solve part of HW3

2. 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

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

4. 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

5. 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

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

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

8. 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

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

10. 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

11. VAV terminal

12. Multizone VAV
55°F
Vary the flow

13. Reading Assignment
Tao and Janis
Chapter 3
Chapter 6 (from 6.1 to 6.7)

14. 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)

15. Homework Assignment 3 Supply air 55°F Recirculation air 76°F
Fresh air (Dallas, TX) DBT=102°F