This paper studies convective heat transfer in an unsteady vertical porous channel with suction/injection in the presence of heat generation. A semi-implicit finite difference method was employed to solve the Cartesian coordinate forms of the governing equations. Subsequently, the entropy generation number for varying values of intrinsic parameters, as well as the temperature and velocity profile, Bejan number and irreversibility of the system were successfully calculated. We observed that the convective cooling by suction is more effective on thermal properties than injection convective cooling. Hence, the process of entropy can be enhanced by convective heat transfer and viscous dissipation. © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.