SimAirLoop Subroutine

private subroutine SimAirLoop(FirstHVACIteration, AirLoopNum, AirLoopPass, AirLoopIterMax, AirLoopIterTot, AirLoopNumCalls)

Arguments

Type	Intent		Name
logical,	intent(in)	::	FirstHVACIteration
integer,	intent(in)	::	AirLoopNum
integer,	intent(in)	::	AirLoopPass
integer,	intent(out)	::	AirLoopIterMax
integer,	intent(out)	::	AirLoopIterTot
integer,	intent(out)	::	AirLoopNumCalls
Source Code

SUBROUTINE SimAirLoop(FirstHVACIteration, AirLoopNum, AirLoopPass, &
                      AirLoopIterMax, AirLoopIterTot, AirLoopNumCalls )

          ! SUBROUTINE INFORMATION
          !             AUTHOR:  Dimitri Curtil (LBNL)
          !       DATE WRITTEN:  March 2006
          !                      - Fine-tuned outer loop over controllers.
          !                      - Added convergence tracing for air loop controllers.
          !                      - Added mechanism for speculative warm restart after first iteration.
          !      RE-ENGINEERED:  This is new code based on the code that used to be part
          !                      of SimAirLoops().

          ! PURPOSE OF THIS SUBROUTINE:
          ! This subroutine simulates the desired air loop by solving for all the
          ! controllers on the air loop in the order they are specified.

          ! METHODOLOGY EMPLOYED:
          ! To speed up the simulation, we introduced the possiblity to perform the controller
          ! simulation on each air loop using a warm restart from the solution obtained
          ! at the previous HVAC step iteration. This is only attempted if the air mass flow
          ! rate(s) for the air system have not changed since the last iteration.
          ! Of course if the warm restart fails, then we perform a normal simulation from
          ! a cold start. We refer to this scheme as speculative warm restart.
          !

          ! REFERENCES: None

          ! USE STATEMENTS:
  USE DataHVACControllers
  USE DataSystemVariables
  USE HVACControllers,        ONLY : TrackAirLoopControllers, TraceAirLoopControllers
  USE General,                ONLY : CreateSysTimeIntervalString

  IMPLICIT NONE

       ! SUBROUTINE ARGUMENT DEFINITIONS:
  ! TRUE if first full HVAC iteration in an HVAC timestep
  LOGICAL, INTENT(IN)          :: FirstHVACIteration
  ! Index of the air loop to simulate
  INTEGER, INTENT(IN)          :: AirLoopNum
  ! There are 2 passes - the 2nd is done only if mass balance fails
  INTEGER, INTENT(IN)          :: AirLoopPass
  ! Max number of iterations performed by controllers across this air loop
  INTEGER, INTENT(OUT)         :: AirLoopIterMax
  ! Aggregated number of iterations across all controllers on this air loop
  INTEGER, INTENT(OUT)         :: AirLoopIterTot
  ! Total number of times SimAirLoopComponents() has been invoked to simulate this air loop
  INTEGER, INTENT(OUT)         :: AirLoopNumCalls

       ! SUBROUTINE PARAMETER DEFINITIONS: None

       ! INTERFACE BLOCK DEFINITIONS: None

       ! DERIVED TYPE DEFINITIONS: None

       ! SUBROUTINE LOCAL VARIABLE DEFINITIONS
  ! Maximum number of iterations performed by each controller on this air loop
  INTEGER                :: IterMax = 0
  ! Aggregated number of iterations performed by each controller on this air loop
  INTEGER                :: IterTot = 0
  ! Number of times SimAirLoopComponents() has been invoked per air loop for either Solve or ReSolve operations
  INTEGER                :: NumCalls = 0
  ! TRUE when primary air system & controllers simulation has converged;
  LOGICAL                :: AirLoopConvergedFlag = .FALSE.
  ! TRUE when speculative warm restart is allowed; FALSE otherwise.
  LOGICAL                :: DoWarmRestartFlag = .FALSE.
  ! If Status<0, no speculative warm restart attempted.
  ! If Status==0, warm restart failed.
  ! If Status>0, warm restart succeeded.
  INTEGER                :: WarmRestartStatus = iControllerWarmRestartNone

          ! FLOW:

  ! Reset air loop trackers to zero
  AirLoopIterMax  = 0
  AirLoopIterTot  = 0
  AirLoopNumCalls = 0

  ! Perform air loop simulation to satisfy convergence for all controllers
  ! If first HVAC iteration or new air flow we force a cold restart.
  ! Otherwise we attempt a speculative warm restart.
  !
  ! TODO: Improve detection of when air flow rate has changed since last air loop simulation
  ! TODO: Detect whether warm restart is supported on air loop on very first air loop
  !       simulation only instead of at each HVAC iteration as done now.
  DoWarmRestartFlag = &
      ! Only enabled if there are controllers on the air loop
      PrimaryAirSystem(AirLoopNum)%NumControllers > 0 .AND.      &
      ! Check that the speculative warm restart feature is allowed
      AirLoopControlInfo(AirLoopNum)%AllowWarmRestartFlag .AND.  &
      ! Never done at first HVAC iteration
      .NOT. FirstHVACIteration .AND.                             &
      ! Never done during sizing
      .NOT. SysSizingCalc .AND.                                  &
      ! Next condition is true whenever the final check for the air loop was converged
      ! at the previous SimAirLoop call
      AirLoopControlInfo(AirLoopNum)%ConvergedFlag .AND.         &
      ! Next conditions should detect when air mass flow rates have changed
      .NOT. AirLoopControlInfo(AirLoopNum)%LoopFlowRateSet .AND. &
      .NOT. AirLoopControlInfo(AirLoopNum)%NewFlowRateFlag

  IF ( .NOT.DoWarmRestartFlag ) THEN
    ! Solve controllers with cold start using default initial values
    CALL SolveAirLoopControllers( &
      FirstHVACIteration, AirLoopPass, AirLoopNum, AirLoopConvergedFlag, &
      IterMax, IterTot, NumCalls )

    ! Update air loop trackers
    WarmRestartStatus = iControllerWarmRestartNone
    AirLoopNumCalls = AirLoopNumCalls + NumCalls
    AirLoopIterMax  = MAX(AirLoopIterMax, IterMax)
    AirLoopIterTot  = AirLoopIterTot + IterTot
  ELSE
    ! First try with speculative warm restart using previous solution
    CALL ReSolveAirLoopControllers( &
      FirstHVACIteration, AirLoopPass, AirLoopNum, AirLoopConvergedFlag, &
      IterMax, IterTot, NumCalls )

    ! Update air loop trackers
    WarmRestartStatus = iControllerWarmRestartSuccess
    AirLoopNumCalls = AirLoopNumCalls + NumCalls
    AirLoopIterMax  = MAX(AirLoopIterMax, IterMax)
    AirLoopIterTot  = AirLoopIterTot + IterTot

    ! Retry with cold start using default initial values if speculative warm restart did not work
    IF ( .NOT.AirLoopConvergedFlag ) THEN
      CALL SolveAirLoopControllers( &
        FirstHVACIteration, AirLoopPass, AirLoopNum, AirLoopConvergedFlag, &
        IterMax, IterTot, NumCalls )

      ! Update air loop trackers
      WarmRestartStatus = iControllerWarmRestartFail
      AirLoopNumCalls = AirLoopNumCalls + NumCalls
      AirLoopIterMax  = MAX(AirLoopIterMax, IterMax)
      AirLoopIterTot  = AirLoopIterTot + IterTot
    END IF
  END IF

  ! Updates air loop statistics
  !
  ! To enable runtime statistics tracking for each air loop, define the environment variable
  ! TRACK_AIRLOOP=YES or TRACK_AIRLOOP=Y
  IF ( TrackAirLoopEnvFlag ) THEN
    CALL TrackAirLoopControllers( &
      AirLoopNum, &
      WarmRestartStatus, &
      AirLoopIterMax, &
      AirLoopIterTot, &
      AirLoopNumCalls &
    )
  END IF

  ! Generate trace for all controllers on this air loop
  !
  ! To enable generating a trace file with the converged solution for all controllers on each air loop,
  ! define the environment variable TRACE_AIRLOOP=YES or TRACE_AIRLOOP=Y.
  IF ( TraceAirLoopEnvFlag ) THEN
    CALL TraceAirLoopControllers( &
      FirstHVACIteration, &
      AirLoopNum, AirLoopPass, AirLoopConvergedFlag, &
      AirLoopNumCalls &
    )
  END IF

  ! When there is more than 1 controller on an air loop, each controller sensing
  ! different nodes with potentially different setpoints, it is likely that
  ! AirLoopConvergedFlag will be false as the individual setpoints will not
  ! be satisfied once all the controllers have been simulated. Typically, this could
  ! happen if
  ! If this is the case then we do not want to try a warm restart as it is very
  ! unlikely to succeed.
  AirLoopControlInfo(AirLoopNum)%ConvergedFlag = AirLoopConvergedFlag

  RETURN
END SUBROUTINE SimAirLoop
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SimAirLoop Subroutine

Source Code

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private subroutine SimAirLoop(FirstHVACIteration, AirLoopNum, AirLoopPass, AirLoopIterMax, AirLoopIterTot, AirLoopNumCalls)

Uses:

Arguments

Calls

Called By

Source Code

Source Code

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