BetweenGlassShadeNaturalFlow Subroutine

private subroutine BetweenGlassShadeNaturalFlow(SurfNum, iter, VGap, TGapNew, hcv)

Arguments

Type	Intent		Name
integer,	intent(in)	::	SurfNum
integer,	intent(in)	::	iter
real(kind=r64),	intent(out)	::	VGap
real(kind=r64),	intent(inout)	::	TGapNew(2)
real(kind=r64),	intent(out)	::	hcv(2)
Source Code

SUBROUTINE BetweenGlassShadeNaturalFlow(SurfNum,iter,VGap,TGapNew,hcv)

          ! SUBROUTINE INFORMATION:
          !       AUTHOR         F. Winkelmann
          !       DATE WRITTEN   December 2002
          !       MODIFIED       na
          !       RE-ENGINEERED  na

          ! PURPOSE OF THIS SUBROUTINE:
          ! Called by SolveForWindowTemperatures for windows that have a
          ! between-glass shade or blind in place.
          ! Solves for gas flow in the two gaps on either side of shade/blind.
          ! Finds average temperature of gas in the two gaps, and the coefficient
          ! for convective heat transfer from glass to gap gas and shade/blind to gap gas
          ! for the two gaps. The two gaps are assumed to have the same depth so that the
          ! gas velocity due to natural convection is the same in the two gaps.
          !
          ! The Between-glass shade/blind is between the two glass layers of double glazing
          ! or between the two inner glass layers of triple glazing. The quadruple glazing
          ! case is not considered.

          ! METHODOLOGY EMPLOYED:
          ! Based on ISO/DIS 15099, "Thermal Performance of Windows, Doors and Shading Devices --
          ! Detailed Calculations," 1/12/2000, Chapter 7, "Shading Devices."

          ! REFERENCES:
          ! na

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

          ! SUBROUTINE ARGUMENT DEFINITIONS:
INTEGER, INTENT (IN) :: SurfNum             ! Surface number
INTEGER, INTENT (IN) :: iter                ! Iteration number for glass heat balance calculation
REAL(r64), INTENT (OUT)   :: VGap                ! Gas velocity in gaps (m/s)
REAL(r64), INTENT (INOUT) :: TGapNew(2)          ! Current-iteration average gas temp in gaps (K)
REAL(r64), INTENT (OUT)   :: hcv(2)              ! Convection coefficient from gap glass or shade to gap gas (W/m2-K)

          ! SUBROUTINE PARAMETER DEFINITIONS:
          ! na

          ! INTERFACE BLOCK SPECIFICATIONS:
          ! na

          ! DERIVED TYPE DEFINITIONS:
          ! na

          ! SUBROUTINE LOCAL VARIABLE DECLARATIONS:
INTEGER              :: ConstrNumSh         ! Shaded construction number
INTEGER              :: MatNumSh            ! Material number of shade/blind layer
INTEGER              :: nglassfaces         ! Number of glass faces in contruction
                                            ! In the following, "gaps" refer to the gaps on either side of the shade/blind
REAL(r64)     :: TGlassFace(2)       ! Temperature of glass surfaces facing gaps (K)
REAL(r64)     :: TShadeFace(2)       ! Temperature of shade surfaces facing gaps (K)
REAL(r64)            :: hGapStill(2)        ! Still-air conduction/convection coeffs for the gaps (W/m2-K)
REAL(r64)            :: TGapOld(2)          ! Previous-iteration average gas temp in gaps (K)
REAL(r64)            :: GapHeight           ! Vertical length of glass-shade/blind gap (m)
REAL(r64)            :: GapDepth            ! Distance from shade/blind to glass; assumed same for both gaps (m)
REAL(r64)            :: RhoGas(2)           ! Density of gap gas at a temperature of TGapOld (kg/m3)
REAL(r64)            :: RhoTRef             ! Density of gap gas at reference temp = KelvinConvK (kg/m3)
REAL(r64)            :: ViscGas(2)          ! Viscosity of gap gas at a temperature of TGapOld (kg/m3)
REAL(r64)            :: RhoGasZero          ! Gas density at KelvinConvK
REAL(r64)            :: ViscGasZero         ! Gas viscosity at KelvinConvK (not used)
REAL(r64)            :: AGap                ! Cross sectional area of gaps (m2); for vertical window, this
                                            !   is in horizontal plane normal to window.
REAL(r64)            :: ATopGap, ABotGap    ! Area of the top and bottom openings of shade/blind (m2)
REAL(r64)            :: ALeftGap, ARightGap ! Area of the left and right openings of shade/blind (m2)
REAL(r64)            :: AHolesGap           ! Area of the holes in the shade/blind (assumed homogeneously
                                            !   distributed) (m2)
REAL(r64)            :: ATopLRH,ABotLRH     ! Intermediate variables
REAL(r64)            :: AEqInlet, AEqOutlet ! Equivalent inlet and outlet opening areas (m2)
REAL(r64)            :: Zinlet, Zoutlet     ! Inlet and outlet pressure loss factors
REAL(r64)            :: AVGap               ! Coeff. of VGap**2 term in pressure balance equation
REAL(r64)            :: BVGap               ! Coeff. of VGap term in pressure balance equation
REAL(r64)            :: CVGap               ! VGap-independent term in pressure balance equation
REAL(r64)            :: GapHeightChar(2)    ! Characteristic height of the gap gas temperature profile (m)
REAL(r64)            :: EpsChar(2)          ! EXP(-GapHeight/GapHeightChar(IGap))
REAL(r64)            :: TAve(2)             ! Average of TGlass and TShade for the gaps (K)
REAL(r64)     :: con                 ! Gap gas conductivity and derivative
REAL(r64)     :: gr                  ! Gap gas Grashof number
REAL(r64)     :: pr                  ! Gap gas Prandtl number
REAL(r64)     :: nu                  ! Gap gas Nusselt number
INTEGER              :: ShadeFlag           ! Shading flag
INTEGER              :: BlNum               ! Blind number
INTEGER              :: IGap                ! Gap counter; 1 = gap on outer side of shade/blind, 2 = gap on inner side.
INTEGER              :: IGapInc             ! Gap increment (0 or 1)


ConstrNumSh = Surface(SurfNum)%ShadedConstruction
ShadeFlag = SurfaceWindow(SurfNum)%ShadingFlag
nglassfaces = 2*Construct(ConstrNumSh)%TotGlassLayers

IF(Construct(ConstrNumSh)%TotGlassLayers == 2) THEN  ! Double glazing
  MatNumSh = Construct(ConstrNumSh)%LayerPoint(3)
  IGapInc = 0
  DO IGap = 1,2
    TGlassFace(IGap) = thetas(IGap+1)
    TShadeFace(IGap) = thetas(IGap+4)
  END DO
ELSE                                                 ! Triple glazing
  MatNumSh = Construct(ConstrNumSh)%LayerPoint(5)
  IGapInc = 1
  DO IGap = 1,2
    TGlassFace(IGap) = thetas(IGap+3)
    TShadeFace(IGap) = thetas(IGap+6)
  END DO
END IF

DO IGap = 1,2
  TAve(IGap) = 0.5d0*(TGlassFace(IGap) + TShadeFace(IGap))
  IF(iter == 0) THEN
    TGapOld(IGap) = TAve(IGap)
  ELSE
    TGapOld(IGap) = TGapNew(IGap)
  END IF
          ! Conductance of gaps on either side of shade/blind assuming gaps are sealed
  CALL WindowGasConductance(TGlassFace(IGap),TShadeFace(IGap),IGap+IGapInc,con,pr,gr)
  CALL NusseltNumber(SurfNum,TGlassFace(IGap),TShadeFace(IGap),IGap+IGapInc,gr,pr,nu)
  hGapStill(IGap) = con/gap(IGap+IGapInc)*nu
END DO

! For near-horizontal windows (i.e., no more than 5 deg from horizontal) assume
! there is no air flow thru gap

IF(ABS(Surface(SurfNum)%SinTilt) < 0.0872d0) THEN
  VGap = 0.0d0
  DO IGap = 1,2
    hcv(IGap) = 2.d0*hGapStill(IGap)
    TGapNew(IGap) = TAve(IGap)
  END DO
  RETURN
END IF

GapHeight = Surface(SurfNum)%Height
GapDepth = gap(1+IGapInc)
AGap = GapDepth * Surface(SurfNum)%Width

IF(ShadeFlag == BGShadeOn) THEN
     ! Shade on
  ATopGap   = Material(MatNumSh)%WinShadeTopOpeningMult * AGap
  ABotGap   = Material(MatNumSh)%WinShadeBottomOpeningMult * AGap
  ALeftGap  = Material(MatNumSh)%WinShadeLeftOpeningMult * GapHeight * GapDepth
  ARightGap = Material(MatNumSh)%WinShadeRightOpeningMult * GapHeight * GapDepth
  AHolesGap = Material(MatNumSh)%WinShadeAirFlowPermeability * GapHeight * Surface(SurfNum)%Width
ELSE
     ! Blind on
  BlNum = SurfaceWindow(SurfNum)%BlindNumber
  ATopGap = Blind(BlNum)%BlindTopOpeningMult * AGap
  ABotGap = Blind(BlNum)%BlindBottomOpeningMult * AGap
  ALeftGap = Blind(BlNum)%BlindLeftOpeningMult * GapHeight * GapDepth
  ARightGap = Blind(BlNum)%BlindRightOpeningMult * GapHeight * GapDepth
  AHolesGap = SurfaceWindow(SurfNum)%BlindAirFlowPermeability * GapHeight * Surface(SurfNum)%Width
END IF

DO IGap = 1,2
  CALL WindowGasPropertiesAtTemp(TGapOld(IGap),IGap+IGapInc,RhoGas(IGap),ViscGas(IGap))
END DO

BVGap = 12.d0*(ViscGas(1)+ViscGas(2))*GapHeight/(GapDepth**2)
! Adding 0.000001 and 0.000002 in the following gives ATopLRH = ABotLRH =
! 0.25*(ALeftGap + ARightGap + AHolesGap) when ABotGap = ATopGap = 0.0 (shade/blind sealed at
! bottom and top but possibly open at left side, right side and/or in shade/blind)
ATopLRH = 0.5d0*((ATopGap+0.000001d0)/(ABotGap+ATopGap+0.000002d0))*(ALeftGap + ARightGap + AHolesGap)
ABotLRH = 0.5d0*((ABotGap+0.000001d0)/(ABotGap+ATopGap+0.000002d0))*(ALeftGap + ARightGap + AHolesGap)
AEqInlet  = ABotGap + ATopLRH
AEqOutlet = ATopGap + ABotLRH

! Adding 0.000001 in the following gives very large value of Zinlet for AEqInlet = 0 and
! very large value of Zoutlet for AEqInlet = 0; this gives VGap close to zero, as required
! when there is no inlet and/or outlet for air. This then reduces to the
! case of a completely sealed shade, in which hcv = 2*hGapStill and QConvGap = 0.
Zinlet  = (AGap/(0.6d0*AEqInlet+0.000001d0)-1.d0)**2
Zoutlet = (AGap/(0.6d0*AEqOutlet+0.000001d0)-1.d0)**2
AVGap = 0.5d0*(RhoGas(1)+RhoGas(2))*(1.d0+Zinlet+Zoutlet)
CALL WindowGasPropertiesAtTemp(TKelvin,1+IGapInc,RhoGasZero,ViscGasZero)
RhoTRef = RhoGasZero*TKelvin
CVGap = RhoTRef*9.81d0*GapHeight*Surface(SurfNum)%SinTilt* &
  (TGapOld(1)-TGapOld(2))/(TGapOld(1)*TGapOld(2))

! Solution of quadratic equation in VGap

VGap = (SQRT(BVGap**2 + ABS(4*AVGap*CVGap)) - BVGap)/(2*AVGap)

DO IGap = 1,2
  hcv(IGap) = 2.d0*hGapStill(IGap) + 4.d0*VGap
  GapHeightChar(IGap) = RhoGas(IGap) * 1008.d0 * GapDepth * VGap/(2.d0*hcv(IGap))
     ! The following avoids divide by zero and exponential underflow
  IF(GapHeightChar(IGap) == 0.0d0) THEN
    EpsChar(IGap) = 0.0d0
  ELSE IF((GapHeight/GapHeightChar(IGap)) > 15.d0) THEN
    EpsChar(IGap) = 0.0d0
  ELSE
    EpsChar(IGap) = EXP(-GapHeight/GapHeightChar(IGap))
  END IF
END DO

TGapNew(1) = TAve(1) - (TAve(1)-TAve(2))*(GapHeightChar(1)/GapHeight) * &
             (1-EpsChar(1))*(1-EpsChar(2))/(1-EpsChar(1)*EpsChar(2))

TGapNew(2) = TAve(2) - (TAve(2)-TAve(1))*(GapHeightChar(2)/GapHeight) * &
             (1-EpsChar(1))*(1-EpsChar(2))/(1-EpsChar(1)*EpsChar(2))

RETURN
END SUBROUTINE BetweenGlassShadeNaturalFlow
All Procedures

BetweenGlassShadeNaturalFlow Subroutine

Source Code

All Procedures

private subroutine BetweenGlassShadeNaturalFlow(SurfNum, iter, VGap, TGapNew, hcv)

Arguments

Calls

Called By

Source Code

Source Code

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