On inherent irreversibility in Sakiadis flow of nanofluids

Abstract

The problem of entropy generation and inherent irreversibility in the steady boundary layer shear flow of nanofluids over a moving flat plate is studied numerically. The governing partial differential equations are transformed into ordinary differential equations using a similarity transformation and then solved numerically by a Runge–Kutta–Fehlberg method with the shooting technique. Two types of nanofluids, namely, Cu–water and TiO2–water, are used. The effects of nanoparticle volume fraction, the type of nanoparticles, group parameter, and the local Reynolds number on the entropy generation rate, irreversibility ratio and the Bejan number are discussed. It is found that the entropy generation rate at the plate surface decreases with increasing nanoparticle volume fraction and the group parameter. Moreover, the heat transfer irreversibility at the plate surface with TiO2–water nanofluid is slightly higher than that at the plate surface with Cu–water nanofluid.