The Hausen equation has been obtained from empirical considerations for fully developed laminar fl ow in tubes having a constant wall temperature. in which the heat-transfer coeffi cient h − L ( /)...

The Hausen equation has been obtained from empirical considerations for fully developed laminar fl ow in tubes having a constant wall temperature.

in which the heat-transfer coeffi cient h − L ( /) NuhD k L f is an average value over the entire length of tube, and fl uid properties are evaluated at the average bulk temperature. Consider the fl ow of glycerin in a 1/2 standard type M copper tube. Glycerin is to be heated from a temperature of 20 to 40°C by keeping the wall temperature at a constant value of 100°C. How long a tube is required to do this? Th e mass fl ow of glycerin is 2.2 kg/s.