Casson Nanofluid Flow in Vertical Channel under Variable Viscosity and Thermal Conductivity with Viscous Dissipation Effects

Abstract

This study investigates the combined effects of variable thermal conductivity and temperature dependent viscosity on the flow and heat energy transfer behaviour of a Casson nanofluid, specifically involving copper nanoparticles suspended in a water-based medium. These nanofluids are highly applicable to practical systems such as electronic cooling devices, polymer extrusion processes, and biomedical applications like targeted drug delivery, where enhanced thermal performance of non-Newtonian fluids is crucial.

The governing momentum and energy equations are expressed as a coupled set of nonlinear, second-order ordinary differential equations, which are then solved. These equations have been resolved using both numerical techniques (BVP5C solver in MATLAB) and analytical method. The results from both methods show strong agreement, validating the reliability of the analytical approach.

Key findings reveal that incorporating copper nanofluid particles increases in the effective thermal conductivity of the water base fluid by up to 16%, resulting in a 15–20% enhancement in heat transfer rate. Additionally, temperature-dependent viscosity improves the velocity distribution by approximately 12.24% contributing to more efficient thermal transport.

The novelty of this work lies in its comprehensive treatment of temperature-sensitive thermal conductivity and viscosity effects in Casson nanofluids, which are often overlooked or treated in isolation in previous studies. By integrating these parameters, the study provides a more realistic and insightful model for optimizing thermal systems that utilize non-Newtonian nanofluids.