Air Loop Simulation[LINK]
A complete simulation of each primary air system – zone equipment air loop is done in the following manner.
If this is the first simulation this system time-step, just call ManageAirLoops (simulates the primary air systems) and ManageZoneEquipment (simulates the zone equipment sets) once and quit. This initial pass is simulated with full design air flow rates and allows the zone equipment to set the flow rates for each zone that will meet the zone loads.
Otherwise loop over primary air systems and zone equipment sets until the temperatures, flow rates, enthalpies, humidity ratios etc. agree to within tolerance at each primary air system – zone equipment gap.
DO WHILE ((SimAirLoops .OR. SimZoneEquipment) .AND. (IterAir.LE.MaxAir) ) IF (SimAirLoops) THEN CALL ManageAirLoops(FirstHVACIteration,SimAirLoops,SimZoneEquipment) SimPlantDemandLoops = .TRUE SimElecCircuits = .TRUE. END IF
IF (SimZoneEquipment) THEN CALL ResolveAirLoopFlowLimits(IterAir+1) CALL ManageZoneEquipment(FirstHVACIteration,SimZoneEquipment,SimAirLoops) SimPlantDemandLoops = .TRUE. SimElecCircuits = .TRUE. END IF
IterAir = IterAir + 1
|specific enthalpy [J/kg}||10.0|
|mass flow rate [kg/s]||0.01|
|humidity ratio [kg H2O / kg dry air]||0.0001|
|air pressure [Pa]||10.0|
ResolveAirLoopFlowLimits is invoked to deal with zone equipment – primary air system flow mismatches. For instance the zone air terminal units (ATUs) may be asking for more air than the central fan can supply. In this case ResolveAirLoopFlowLimits takes the air flow that the fan can supply and apportions it among the ATUs in proportion to their design maximum air flow rates (ResolveAirLoopFlowLimits sets the ˙mmaxavail,node at the entering node of each ATU in the system).
At the end of the air loop simulation ResolveLockoutFlags is called. This subroutine checks if any air system component has requested that the economizer be locked out. If such a request has been made and if the economizer is active, ResolveLockoutFlags sets SimAirLoops to true and the EconoLockout flag to true to ensure that the air loop will be resimulated with the economizer forced off.