Effect of non-uniform asymmetric heating on the thermal and entropy generation characteristics for flow of Al₂O₃-water nanofluid in a micro-channel

Abstract

Purpose The purpose of this study is to numerically analyze the thermal and entropy generation characteristics on two-dimensional, incompressible, laminar single-phase flow of Al2O3-water nanofluid in a micro-channel subjected to asymmetric sinusoidal wall heating with varying amplitude, length of fluctuation period and phase difference of applied heat flux for Reynolds number in the range of 25-1000. Design/methodology/approach The numerical computation is based on the Finite Element Method and the Lagrange finite element technique is used for approximating the flow variables within the computational domain. Findings The average Nusselt number increases with increasing Reynolds number (Re) for all the volume fractions of nanofluid. However, the total entropy generation decreases up to a critical value of Re and increases thereafter. Increase in volume fraction shifts the critical Re towards the lower Re regime. The average Nusselt number and total entropy generation increase with amplitude and length of fluctuation period of heat flux. The optimal choice of volume fraction for lesser entropy generation and higher heat transfer is found to be 3 per cent independent of the value of amplitude, length of fluctuation period and phase difference of the heat flux. Originality/value To the best of authors’ knowledge, the interplay of various parameters concerning non-uniform heating in achieving the maximum heat transfer with minimum irreversibility has not been investigated. Focusing on this agenda, the results of this study would benefit the industrial sector in achieving the maximum heat transfer at the cost of minimum irreversibilities with an optimal choice of inlet Reynolds number, volume fraction of nanofluid, amplitude, length of the period of fluctuation of heat flux and phase difference of applied heat flux.

Three-dimensional modelling of natural convection and entropy generation in a vertical cylinder under heterogeneous heat flux using nanofluids

“…The normalized average Nusselt number ( normalNuavg*true) and the normalized total entropy generation ( NS,t*true) versus NPs concentration for the different studied heat flux profile cases and different Ra are presented in Figure 6. This result is interesting, as it allows choosing the conditions giving a higher rate of heat transfer with minimum energy loss (Sheikholeslami et al , 2018b, 2018a, 2019; Boruah et al , 2019; Armaghani et al , 2018; Rashidi et al , 2017). Similar trends have been observed by Abu-Nada et al (2010).…”

Fluid Flow and Entropy Generation Analysis of Al2O3–Water Nanofluid in Microchannel Plate Fin Heat Sinks

“…Taking advantage of the symmetry, a quarter of the rectangular channel as shown in Figure 1 b is chosen as the numerical model to reduce computation cost. The nanofluid can be treated as incompressible Newtonian fluid and the thermophysical properties are assumed to be constant in this study [ 70 , 71 ]. The dimensions of the computational domain in this work are presented in Table 1 .…”

Effect of magnetic field and nanoparticle shape on jet impingement over stationary and vibrating plates

“…Selimefendigil and Oztop (2018a, 2018b, 2018c, 2018d) concluded that adding nanoparticles to the base fluid results in higher heat transfer enhancements for flow over a backward facing step having an elastic bottom wall. Hayat et al (2015), Heydari and Shokouhmand (2017) and Boruah et al (2019) observed the advantageous behavior of nanofluids in attaining higher rates of heat transfer. A detailed review mentioning the recent advancements in modeling and simulation of nanofluid flows was presented by Mahian et al (2018a, 2018b) in two parts.…”