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

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 ………

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

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

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)

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”

Requirement for modeling of mass flow in ES programs

Combined 1) Air flow and 2) Energy flow modeling Example: Night Cooling/Hybrid Ventilation: The IONICA Office Building, Cambridge, UK

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

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

Energy and Airflow simulation domain Coupling surfaces

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

Coupling

Coupled Airflow and Energy Simulation Software Components and Data flow