Flow and heat transfer of couple stress fluid in a vertical channel in the presence of heat source/sink

Purpose -The purpose of this paper is to consider the problem of fully developed laminar mixed convection flow of a couple stress fluid in a vertical channel with the third-kind boundary conditions in the presence or absence of heat source/sink effect. Design/methodology/approach -Through proper choice of dimensionless variables, the governing equations are developed. These governing equations are solved analytically by the differential transform method and numerically by the Runge-Kutta shooting method. Analytical solutions for the velocity and temperature profiles for heat generation and absorption of the problem are reported. Findings -The mass flow rate and Nusselt numbers at both the left and right channel walls on mixed convection parameter, Brinkman number, couple stress parameter and heat generation/absorption parameter for equal and unequal Biot numbers are presented. Favorable comparisons of special cases with previously published work are obtained. It is found that velocity, temperature, mass flow rate and Nusselt number decrease with couple stress parameter and increase with mixed convection parameter and Brinkman number. Originality/value -The work done in this paper is not done earlier to the authors' knowledge. This is the first paper in which the sixth-order differential equation is solved using the semi-numerical method, which is a differential method.