The present work, the entropy generation due to radiation and variable viscosity magnetohydrodynamic effects with a porous medium in a
circular pipe, has been obtained and studied numerically.
The governing continuity, momentum, and energy equations in cylindrical coordination are converted into a system of nonlinear ordinary
differential equations by means of similarity transformation. The resulting system of coupled nonlinear ordinary differential equations is solved numerically by a Runge‐Kutta method and shooting technique. Numerical results are presented for velocity, temperature profiles, pressure profile, entropy generation rates, and Bejan number for
different physical parameters of the problem. Also, the effects of the pertinent parameters on the skin friction and the rate of heat transfer are obtained and discussed numerically and illustrated graphically.