ME 150 – Heat and Mass Transfer
Chap. 12.3: Dimensionless Parameters
Dimensionless Parameters for Convection Transport phenomena can be described qualitatively and quantitatively by using dimensionless parameters. Convective heat transfer is described by the Nusselt Number (Nu): Nu L =
Reynolds Number Re
Prandtl Number Pr
h ⋅L = f (Re, Pr ) kf
Re L =
Pr =
U ⋅L U ⋅L⋅ρ =
ν
ν µ = α α ⋅ρ
Prof. Nico Hotz
⎛ Convection ⎞ ⎜ ⎟ ⎝ Conduction ⎠
µ
⎛ Inertial Forces ⎞ ⎜⎜ ⎟⎟ ⎝ Viscous Forces ⎠
⎛ Momentum Diffusivity ⎞ ⎜⎜ ⎟⎟ ⎝ Thermal Diffusivity ⎠ 1
ME 150 – Heat and Mass Transfer
Chap. 12.3: Dimensionless Parameters
Example: For turbulent flows inside of a channel / pipe, the following emperical correlation can be used:
Nu D = 0.023 ⋅ Re 4D/ 5 ⋅ Pr n
n = 0.4 for heating of fluid, n = 0.3 for cooling of fluid
High Re Numbers: turbulent flow Low Re Numbers: laminar flow
Prof. Nico Hotz
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ME 150 – Heat and Mass Transfer
Prof. Nico Hotz
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