avg o.85,but ranges from 0.7 to 0.9 depending on the prandtl number

The Nusselt number is proportional to the Prandtl number to the nth power, where n is a positive number less than one.

Prandtl number is dimensionless number, denoted by Npr.Npr = Cp (viscosity)/(thermal conductivity)

Cp - specific heat, J per ( Kg Kelvin)

viscosity in poise (gm per( cm sec))

thermal conductivity in Watt per (meter kelvin)

Prandtl number is important in heat transfer.

Ludwig Prandtl was born on February 4, 1875.

Ludwig Prandtl was born on February 4, 1875.