Numerical simulation and sensitivity analysis of effective parameters on heat transfer and homogeneity of Al2O3 nanofluid in a channel using DPM and RSM

Abstract

In this paper, a 2-D numerical study and a sensitivity analysis of convective heat transfer in a channel are investigated using the Discrete Phase Model along with determination of the nanoparticles concentration distribution. Numerical simulations are carried out to investigate the effects of the three parameters, the Reynolds number (250 ⩽ Re ⩽ 650), nanoparticles volume fraction (0.01 ⩽ Ф ⩽ 0.05) and nanoparticles diameter (40 nm ⩽ dp ⩽ 100 nm) on the heat transfer performance and nanoparticles distribution. In addition, the effective parameters analysis is performed utilizing the Response Surface Methodology. The results indicated that increasing the Re number and Ф and decreasing of dp, enhances the mean total Nusselt number. Also, an enhancement in dp and Ф and reduction of Re number increases the homogeneity of the nano-fluid. In addition, it is found that the sensitivity of the mean total Nusselt number to Re number, Ф and dp parameters is more than the sensitivity of the nanoparticles concentration ratio to these parameters.

1. Introduction

Several applications of thermal engineering in solar heat exchangers, cooling of electronic equipment, compact heat exchangers, thermal-energy conversion devices and solar collectors are some examples of various important practical applications and usage of forced convection heat transfer in channels. Therefore, during the process of the heat transfer in channels investigation, the predicting of the heat transfer is one of the basic essentials. Enhancing of the heat transfer in above mentioned engineering applications has been a subject of interest in several research studies in last years. Also, due to the low thermal conductivity of the common fluids which are used in commercial applications of channels (including water, ethylene glycol and oil), to improve the heat transfer rate, adding of nanoparticles such as Cu, Al2O3 and TiO2 to the fluid which creates a mixture called nanofluid and enhances the heat transfer coefficient, has been investigated in several papers [1–5].

Nanofluids have various applications in fluids and heat transfer studies. As mentioned above, some researchers have considered the effects of the adding nanoparticles to enhance the heat transfer rate. These researches were mostly done by considering a single phase and some of them by two phases; such as the study which was done by Bianco et al. [2] on the turbulent convection heat transfer of Al2O3-water nanofluid in a circular tube subjected to constant wall temperature. In their study, the numerical investigation was done using the mixture model that is an appropriate method to simulate nanofluids behavior. The results showed that increasing of the nanofluid concentration increases the Nusselt number. Another numerical study on flow characteristics, heat transfer and entropy generation of nano-fluid flow inside an annular pipe partially or completely filled with porous media using twophase mixture model has been carried out by Siavashi et al. [3]. They found that the Reynolds number, nanoparticles concentration and configurations parameters, have significant effects on the entropy generation and the performance. Bianco et al. [4]