Excel in ME

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Excel in ME

• Nusselt numbers

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Functions

• Functions return the local (Nu) or average
  (NuBar) Nusselt number
• The functions are reliable only over certain
  ranges. An answer will be returned, but it is up
  to the user to decide if it is adequate.
• A warning will appear for values outside the
  reliable range for the function.
• Quiet - Each function has an optional Quiet
  input. True or 1 will turn off the warnings.
  False if omitted.

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Functions

• Optional Inputs in italics
• NuxPlate(Re, Pr, Rexc, Quiet)
• NuBarPlate(Re, Pr, Rexc, Quiet)
• NuDBarCyl(Re, Pr, Quiet)
• NuDBarSphere(Re, Pr, mu_mus, Quiet)
• NuDBarTubes(Re, Pr, St_D, Sl_D, Aligned, Nl,
  Quiet)
• NuDBarZTubes(Re, Pr, Prs, St_Sl, Aligned, Nl,
  Quiet)
• NuDBarLamTube(Re, Pr, D_L, Thermal, mu_mus,
  Quiet)
• NuDTurbTube(Re, Pr, Quiet)
• NuDLiqMetals (Re, Pr, UniformT, Quiet)

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Flat Plate, Local Nusselt Number

• NuxPlate(Re, Pr, Rexc, Quiet)
• Returns the local Nusselt number at x
• Inputs based on the film temperature, Tf
  (TsT8)/2
• Re - Reynolds number, Rex V x / n
• Pr - Parndtl number, Pr cp m / k n / a
• Rexc - Critical reynolds number. Reynolds number
  at transition point from laminar to turbulent.
  If Re lt Rexc, then laminar calculation.
  Otherwise, the calculation is for turbulent flow.
  If omitted, Recx 5 X 105
• Ranges
• For laminar, Pr 0.6
• For turbulent, Rex 108, 0.6 Pr 60

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Flat Plate, Mean Nusselt Number

• NuBarPlate(Re, Pr, Rexc, Quiet)
• Returns the average Nusselt number from 0 to x
• Inputs based on the film temperature, Tf
  (TsT8)/2
• Re - Reynolds number, Rex V x / n
• Pr - Parndtl number, Pr cp m / k n / a
• Rexc - Critical reynolds number. Reynolds number
  at transition point from laminar to turbulent.
  If Re lt Rexc, then laminar calculation.
  Otherwise, the calculation is for a mix of
  laminar and turbulent. If omitted, Recx 5 X
  105
• Ranges
• For laminar, Pr 0.6
• For mixed, ReL 108, 0.6 Pr 60

Rex, c
V, T8
Turbulent
Laminar
x
Ts
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Cylinder in crossflow

• NuDBarCyl(Re, Pr, Quiet)
• Returns the average Nusselt number for crossflow
  over a cylinder
• Inputs based on the film temperature, Tf
  (TsT8)/2
• Re - Reynolds number, ReD V D / n
• Pr - Parndtl number, Pr cp m / k n / a
• Range
• ReD Pr 0.2

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Sphere

• NuDBarSphere(Re, Pr, mu_mus, Quiet)
• Returns the average Nusselt number for flow over
  a sphere
• Inputs based on the ambient fluid temperature,
  T8, except ms
• Re - Reynolds number, ReD V D / n
• Pr - Parndtl number, Pr cp m / k n / a
• mu_mus - m / ms viscosity ratio calculated from
  T8 and Ts at the surface
• Range
• 0.71 Pr 380
• 3.5 ReD 7.6 X 104

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Bank of Tubes

• NuDBarTubes(Re, Pr, St_D, Sl_D, Aligned, Nl,
  Quiet)
• Returns the average Nusselt number for crossflow
  over a bank of tubes
• Inputs based on the film temperature, Tf
  (TsT8)/2
• Re - Reynolds number, ReD, max Vmax D / n
• Pr - Parndtl number, Pr cp m / k n / a
• St_D - Transverse spacing / Diameter, St / D
• Sl_D - Longitudianl spacing / Diameter, Sl / D
• Aligned - True or 1 for Aligned tubes, False or 0
  for Staggered tubes. Aligned if omitted.
• Nl - Number of rows, if less than 10. Allows for
  correction factor if there are less than 10 rows.
  If omitted, Nl 10
• Vmax
• Aligned - Vmax St V / (St-D)
• Staggered
• if 2 SD gt St D, same as aligned
• else Vmax ½ V St / (SD-D)
• Ranges
• Pr 0.7
• 2000 ReD, max 40,000

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Bank of Tubes, Zukauskas

• NuDBarZTubes(Re, Pr, Prs, St_Sl, Aligned, Nl,
  Quiet)
• Returns the average Nusselt number for crossflow
  over a bank of tubes based on a new correlation
  by Zukauskas
• Inputs based on the film temperature, Tf
  (TsT8)/2
• Re - Reynolds number, ReD, max Vmax D / n
• Pr - Parndtl number, Pr cp m / k n / a
• Prs - Parndtl number calculated for the average
  of the inlet and outlet temperatures
• St_Sl - Transverse spacing / Longitudianl
  spacing, St / Sl
• Aligned - True or 1 for Aligned tubes, False or 0
  for Staggered tubes. Aligned if omitted.
• Nl - Number of rows, if less than 20. Allows for
  correction factor if there are less than 20 rows.
  If omitted, Nl 20
• Vmax
• Aligned - Vmax St V / (St-D)
• Staggered
• if 2 SD gt St D, same as aligned
• else Vmax ½ V St / (SD-D)
• Ranges
• 0.7 Pr 500
• 1000 ReD, max 2 X 106

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Laminar Flow in a Tube

• NuBarLamTube(Re, Pr, D_L, Thermal, mu_mus, Quiet)
• Returns the average Nusselt number for laminar
  flow through a circular tube
• Function based on uniform surface temperature
• Inputs based on the mean of the inlet and outlet
  temperatures, Tm (TiTo)/2, except ms
• Re - Reynolds number, ReD V D / n
• Pr - Parndtl number, Pr cp m / k n / a
• D_L - Diameter / Length, D / L
• Thermal - True or 1 for Thermal entry length,
  False or 0 for combined entry length. True if
  omitted.
• Thermal entry assumes a fully developed velocity
  profile. For instance, if the tube is preceded
  by a section where there is no heat transfer.
  Also gives a good approximation for large Prandtl
  number fluids, like oil.
• Combined entry has both the velocity and thermal
  profiles developing simultaneously.
• mu_mus - m / ms viscosity ratio calculated from
  Tm and Ts at the surface only needed for
  combined entry with Pr 5. 0 if omitted
• Ranges for combined entry
• Pr 0.6 For Pr 5, the answer is calculated
  with the thermal entry formula
• 0.0044 (m/ms) 9.75

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Turbulent Flow in a Tube

• NuDTurbTube(Re, Pr, Quiet)
• Returns the Nusselt number for turbulent flow
  through a circular tube
• Inputs based on the mean of the inlet and outlet
  temperatures, Tm (TiTo)/2
• Re - Reynolds number, ReD V D / n
• Pr - Parndtl number, Pr cp m / k n / a
• Range
• 0.5 Pr 2000
• 3000 ReD 5 X 106
• L/D 10

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Liquid metal flow through a tube

• NuDLiqMetals (Re, Pr, UniformT, Quiet)
• Returns the Nusselt number for liquid metal flow
  through a circular tube
• Other correlations do not apply to liquid metals
• (3 X 10-3 Pr 5 X 10-2)
• Inputs based on the mean of the inlet and outlet
  temperatures, Tm (TiTo)/2
• Re - Reynolds number, ReD V D / n
• Pr - Parndtl number, Pr cp m / k n / a
• UniformT - True or 1 for uniform surface
  temperature, False or 0 for uniform heat flux at
  surface. True if omitted.
• Ranges
• For uniform surface temperature
• Peclet number, PeD ReD X Pr 100
• For uniform surface heat flux
• 3.6 X 103 ReD 9.05 X 105
• 102 PeD 104