CalcApproximateViewFactors Subroutine

private subroutine CalcApproximateViewFactors(N, A, Azimuth, Tilt, F, SPtr)

Arguments

Type	Intent	Attributes		Name
integer,	intent(in)		::	N
real(kind=r64),	intent(in),	DIMENSION(N)	::	A
real(kind=r64),	intent(in),	DIMENSION(N)	::	Azimuth
real(kind=r64),	intent(in),	DIMENSION(N)	::	Tilt
real(kind=r64),	intent(out),	DIMENSION(N,N)	::	F
integer,	intent(in),	DIMENSION(N)	::	SPtr
Source Code

SUBROUTINE CalcApproximateViewFactors(N,A,Azimuth,Tilt,F,SPtr)

          ! SUBROUTINE INFORMATION:
          !       AUTHOR         Curt Pedersen
          !       DATE WRITTEN   July 2000
          !       MODIFIED       March 2001 (RKS) to disallow surfaces facing the same direction to interact radiatively
          !                      May 2002 (COP) to include INTMASS, FLOOR, ROOF and CEILING.
          !       RE-ENGINEERED  September 2000 (RKS for EnergyPlus)

          ! PURPOSE OF THIS SUBROUTINE:
          ! This subroutine approximates view factors using an area weighting.
          ! This is improved by one degree by not allowing surfaces facing the same
          ! direction to "see" each other.

          ! METHODOLOGY EMPLOYED:
          ! Each surface sees some area of other surfaces within the zone.  The view
          ! factors from the surface to the other seen surfaces are defined by their
          ! area over the summed area of seen surfaces.  Surfaces facing the same angle
          ! are assumed to not be able to see each other.
          !  Modified May 2002 to cover poorly defined surface orientation.  Now all thermal masses, roofs and
          !  ceilings are "seen" by other surfaces. Floors are seen by all other surfaces, but
          !  not by other floors.

          ! REFERENCES:
          ! na

          ! USE STATEMENTS:
          ! na

  IMPLICIT NONE    ! Enforce explicit typing of all variables in this routine

          ! SUBROUTINE ARGUMENTS:
  INTEGER, INTENT (IN)                  :: N    ! NUMBER OF SURFACES
  REAL(r64), INTENT (IN),  DIMENSION(N)   :: A    ! AREA VECTOR- ASSUMED,BE N ELEMENTS LONG
  REAL(r64), INTENT (IN),  DIMENSION(N)   :: Azimuth ! Facing angle of the surface (in degrees)
  REAL(r64), INTENT (IN),  DIMENSION(N)   :: Tilt ! Tilt angle of the surface (in degrees)
  REAL(r64), INTENT (OUT), DIMENSION(N,N) :: F    ! APPROXIMATE DIRECT VIEW FACTOR MATRIX (N X N)
  INTEGER, INTENT (IN),  DIMENSION(N)   :: SPtr ! pointer to REAL(r64) surface number (for error message)

          ! SUBROUTINE PARAMETER DEFINITIONS:
  REAL(r64), PARAMETER :: SameAngleLimit = 10.0d0 ! If the difference in the azimuth angles are above this value (degrees),
                                          ! then the surfaces are assumed to be facing different directions.

          ! INTERFACE BLOCK SPECIFICATIONS
          ! na

          ! DERIVED TYPE DEFINITIONS
          ! na

          ! SUBROUTINE LOCAL VARIABLE DECLARATIONS:

  INTEGER :: I, J       ! DO loop counters for surfaces in the zone
  REAL(r64), ALLOCATABLE, DIMENSION(:) :: ZoneArea   ! Sum of the area of all zone surfaces seen

          ! FLOW:
          ! Calculate the sum of the areas seen by all zone surfaces
  ALLOCATE(ZoneArea(N))
  ZoneArea = 0.0d0
  DO I = 1, N
    DO J = 1, N
          ! Assumption is that a surface cannot see itself or any other surface
          ! that is facing the same direction (has the same azimuth)
          !  Modified to use Class of surface to permit INTMASS to be seen by all surfaces,
          !  FLOOR to be seen by all except other floors, and ROOF and CEILING by all.
          !
          !  Skip same surface
          !
      IF (I== J) cycle
         !
         !  Include INTMASS, FLOOR(for others), CEILING, ROOF  and different facing surfaces.
         !
      IF ( (Surface(SPtr(J))%Class == SurfaceClass_IntMass) .OR.     &  ! Everything sees internal mass surfaces
           (Surface(SPtr(J))%Class == SurfaceClass_Floor)  .OR.        &  ! Everything except other floors sees floors
           (Surface(SPtr(J))%Class == SurfaceClass_Roof .AND. Surface(SPtr(I))%Class == SurfaceClass_Floor)  .OR.  &
                       !  Roofs/ceilings always see floors
           ((ABS(Azimuth(I)-Azimuth(J)) > SameAngleLimit).OR. (ABS(Tilt(I)-Tilt(J)) > SameAngleLimit)  ) ) THEN

         ZoneArea(I) = ZoneArea(I) + A(J)

      END IF
    END DO
    IF (ZoneArea(I) <= 0.0d0) THEN
      CALL ShowWarningError('CalcApproximateViewFactors: Zero area for all other zone surfaces.')
      CALL ShowContinueError('Happens for Surface="'//TRIM(Surface(SPtr(I))%Name)//'" in Zone='//  &
                             TRIM(Zone(Surface(SPtr(I))%Zone)%Name))
    ENDIF
  END DO


          ! Set up the approximate view factors.  First these are initialized to all zero.
          ! This will clear out any junk leftover from whenever.  Then, for each zone
          ! surface, set the view factor from that surface to other surfaces as the
          ! area of the other surface divided by the sum of the area of all zone surfaces
          ! that the original surface can actually see (calculated above).  This will
          ! allow that the sum of all view factors from the original surface to all other
          ! surfaces will equal unity.  F(I,J)=0 if I=J or if the surfaces face the same
          ! direction.
          !
          !  Modified to use Class of surface to permit INTMASS to be seen by all surfaces,
          !  FLOOR to be seen by all except other floors, and ROOF and CEILING by all.
          !
          ! The second IF statement is intended to avoid a divide by zero if
          ! there are no other surfaces in the zone that can be seen.
  F = 0.0d0
  DO I = 1, N
    DO J = 1, N

         !  Skip same surface

       IF (I== J) cycle
         !
         !  Include INTMASS, FLOOR(for others), CEILING/ROOF  and different facing surfaces.
         !
       IF ( (Surface(SPtr(J))%Class == SurfaceClass_IntMass) .OR.   &
            (Surface(SPtr(J))%Class == SurfaceClass_Floor)  .OR.        &
            (Surface(SPtr(J))%Class == SurfaceClass_Roof)  .OR.        &
            ((ABS(Azimuth(I)-Azimuth(J)) > SameAngleLimit).OR. &
            (ABS(Tilt(I)-Tilt(J)) > SameAngleLimit)          ) ) THEN
         IF (ZoneArea(I) > 0.0d0) F(I,J) = A(J)/(ZoneArea(I))
       END IF


    END DO
  END DO

  DEALLOCATE(ZoneArea)

  RETURN

END SUBROUTINE CalcApproximateViewFactors
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CalcApproximateViewFactors Subroutine

Source Code

All Procedures

private subroutine CalcApproximateViewFactors(N, A, Azimuth, Tilt, F, SPtr)

Arguments

Calls

Called By

Source Code

Source Code

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