EstimateHEXSurfaceArea Function

private function EstimateHEXSurfaceArea(CoilNum) result(SurfaceArea)

Arguments

Type	Intent	Optional	Attributes		Name
integer,	intent(in)			::	CoilNum
Return Value real(kind=r64)

Called By

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Source Code

EstimateHEXSurfaceArea
Source Code

FUNCTION EstimateHEXSurfaceArea(CoilNum) RESULT(SurfaceArea)

          ! FUNCTION INFORMATION:
          !       AUTHOR         Bereket A Nigusse, FSEC
          !       DATE WRITTEN   July 2010
          !       MODIFIED
          !       RE-ENGINEERED

          ! PURPOSE OF THIS FUNCTION:
          ! Splits the UA value of a simple coil:cooling:water heat exchanger model into
          ! "A" and U" values.

          ! METHODOLOGY EMPLOYED:
          ! A typical design U overall heat transfer coefficient is used to split the "UA" into "A"
          ! and "U" values. Currently a constant U value calculated for a typical cooling coil is
          ! used. The assumptions used to calculate a typical U value are:
          !     (1) tube side water velocity of 2.0 [m/s]
          !     (2) inside to outside total surface area ratio (Ai/Ao) =  0.07 [-]
          !     (3) fins overall efficiency = 0.92 based on aluminum fin, 12 fins per inch, and
          !         fins area to total outside surafce area ratio of about 90%.
          !     (4) air side convection coefficient of 140.0 [W/m2C].  Assumes sensible convection
          !         of 58.0 [W/m2C] and 82.0 [W/m2C] sensible convection equivalent of the mass
          !         transfer coefficient converted using the approximate relation:
          !         hequivalent = hmasstransfer/Cpair.

          ! REFERENCES:

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

          ! SUBROUTINE ARGUMENT DEFINITIONS:
  INTEGER, INTENT(IN)    :: CoilNum         ! coil number, [-]
  REAL(r64)              :: SurfaceArea     ! Heat exchanger surface area, [m2]

          ! FUNCTION PARAMETER DEFINITIONS:
  REAL(r64), PARAMETER :: OverallFinEfficiency = 0.92d0  ! Assumes aluminum fins, 12 fins per inch, fins
                                                         ! area of about 90% of external surface area Ao.
  REAL(r64), PARAMETER :: AreaRatio = 0.07d0       ! Heat exchanger Inside to Outside surface area ratio
                                                   ! design values range from (Ai/Ao) = 0.06 to 0.08

          ! INTERFACE BLOCK SPECIFICATIONS
          ! na

          ! DERIVED TYPE DEFINITIONS
          ! na

          ! FUNCTION LOCAL VARIABLE DECLARATIONS:
  REAL(r64) :: UOverallHeatTransferCoef      ! over all heat transfer coefficient for coil [W/m2C]
  REAL(r64) :: hAirTubeOutside               ! Air side heat transfer coefficient [W/m2C]
  REAL(r64) :: hWaterTubeInside              ! water (tube) side heat transfer coefficient [W/m2C]

  WaterCoil(CoilNum)%UACoilTotal = 1.d0/(1.d0/WaterCoil(CoilNum)%UACoilExternal &
                                 + 1.d0/WaterCoil(CoilNum)%UACoilInternal)

      ! Tube side water convection heat transfer coefficient of the cooling coil is calculated for
      ! inside tube diameter of 0.0122m (~0.5 inch nominal diameter) and water velocity 2.0 m/s:
  hWaterTubeInside = 1429.d0*(2.d0**0.8d0)*(0.0122d0**(-0.2d0))

      ! Constant value air side heat transfer coefficient is assumed. This coefficient has sensible
      ! (58.d0 [W/m2C]) and latent (82.d0 [W/m2C]) heat transfer coefficient components.
  hAirTubeOutside = 58.d0 + 82.d0

      ! Estimate the overall heat transfer coefficient, UOverallHeatTransferCoef in [W/(m2C)].
      ! Neglecting tube wall and fouling resistance, the overall U value can be estimated as:
      ! 1/UOverallHeatTransferCoef = 1/(hi*AreaRatio) + 1/(ho*OverallFinEfficiency)

  UOverallHeatTransferCoef = 1.d0/(1.d0/(hWaterTubeInside*AreaRatio) &
                           + 1.d0/(hAirTubeOutside*OverallFinEfficiency))

      ! the heat exchanger surface area is calculated as follows:
  SurfaceArea=WaterCoil(CoilNum)%UACoilTotal/UOverallHeatTransferCoef

  RETURN
  END Function EstimateHEXSurfaceArea
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