The second law analysis is performed to study the entropy generation rate in a variable viscosity liquid flowing steadily through a cylindrical pipe with convective cooling at the pipe surface. The system is assumed to exchange heat with the ambient following Newton’s cooling law and the fluid viscosity model varies as an inverse linear function of temperature. The analytical expressions for fluid velocity and temperature that were derived essentially expedite the expressions for volumetric entropy generation of numbers, irreversibility distribution ratio and the Bejan number in the flow field.

Key words: Pipe flow, variable viscosity, convective cooling, irreversibility analysis.