The Prandtl number is a dimensionless number that is defined as the ratio of momentum diffusivity (kinematic viscocity) to thermal diffusivity.
It is defined as:
where:
- : kinematic viscocity, , (SI units : m2/s)
- : thermal diffusivity, , (SI units : m2/s)
- : dynamic viscocity, (SI units : Pa s = N s/m2
- : thermal conductivity, (SI units : W/(m K) )
- : specific heat capacity, (SI units : J/(kg K) )
- : density, (SI units : kg/m3 ).
Pr < 1 means thermal diffusivity dominates and Pr >1 means momentum diffusivity dominates.
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