Free convection and radiation effects in nanofluid (Silicon dioxide and Molybdenum disulfide) with second order velocity slip, entropy generation, Darcy-Forchheimer porous medium

In this research, communication, mathematical modeling and numerical simulation are presented for the steady, incompressible two-dimensional Darcy-Forchheimer nanofluid flow of viscous material towards a stretched surface. The flow is generated due to stretching surface and saturated through Darcy-Forchheimer relation. The radiative heat flux and viscous dissipation effects are utilized in the modeling of energy expression. Second order slip and convective condition are imposed at the stretchable boundary for velocity and temperature respectively. A total entropy rate, which depends three different types of irreversibilities i.e., heat transfer, fluid friction and Darcy-Forchheimer relation or porosity are calculated via the second law of thermodynamics. Here Silicon dioxide and Molybdenum disulfide are considered as nanomaterials and water as base fluid. The boundary layer approximation concept is used to model the governing equations of momentum and temperature. Appropriate similarity transformations are used to alter the governing equations into ordinary ones and numerical results are obtained via Built-in-Shooting method. The obtained results are compared with existing work and noticed to be in excellent agreement. Behavior of pertinent flow parameters is discussed graphically on the velocity, temperature, Bejan number and entropy generation for both nanoparticles (Silicon dioxide, Molybdenum). Furthermore, the skin friction coefficient (surface drag force) and heat transfer rate (Nusselt number) are discussed in the presence of slip parameters and stratification parameter. It is noted from the obtained results that entropy generation rate enhances for higher Brinkman number and temperature decreases against higher values of stratification parameter. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.