1. Lecture Objectives: Finish with HVAC systems
Discuss airflow modeling in energy simulation tools

2. HVAC systems Detailed list of HVAC System Types is in eQUEST help file
Most common / most important:
- Packaged Single Zone DX with Furnace
Packaged Multizone with Furnace
Packaged VAV with Elec Reheat
Packaged Multizone with Elec Heat
Standard VAV with HW Reheat
4-Pipe Fan Coils with HW Heat
Dual Duct Air Handler with HW Heat
………

3. Basic purpose of HVAC control
Daily, weekly, and seasonal swings make HVAC control challenging
Highly unsteady-state environment
Provide balance of reasonable comfort at minimum cost and energy
Two distinct actions:
1) Switching/Enabling: Manage availability of plant according to schedule using timers.
2) Regulation: Match plant capacity to demand

4. Control models integrated in HVAC system simulation
Example:
Economizer (fresh air volume flow rate control)
Controlled device is damper
- Damper for the air
- Valve for the liquids
fresh
air
damper
mixing
recirc.
air
T & RH sensors

5. Difference between perfect and non perfect control and impact on energy consumption
Example: Heat exchanger control
Modulating (Analog) control
air
water
Cooling coil x
(set point temperature)

6. The control in HVAC system – only PI
Proportional
Integral
value
Set point
Proportional
affect the slope
Set point
Integral
affect the shape after
the first “bump”

7. Requirement for modeling of mass flow in ES programs

8. Combined 1) Air flow and ) Energy flow modeling Example: Night Cooling/Hybrid Ventilation: The IONICA Office Building, Cambridge, UK

9. Night Cooling/Hybrid Ventilation: The IONICA Office Building, Cambridge, UK

10. Night Cooling/Hybrid Ventilation: The IONICA Office Building, Cambridge, UK

11. Energy and Airflow simulation domain
Coupling
surfaces

12. Coupling Energy Air Flow Simulation Program Twall, CFM, Tsupply Data:
geometry
weather
materials
IAQ
V,T,…
Energy cons.
Tnear surface, h surface

13. Coupling

14. Coupled Airflow and Energy Simulation Software Components and Data flow