Heat transfer and entropy generation optimization for flow of a non-Newtonian hybrid nanofluid containing coated CNT/Fe3O4 nanoparticles in a concentric annulus

Abstract This research attempts to investigate the effects of concentration and radius ratio on convective heat transfer and entropy generation of a non-Newtonian hybrid nanofluid flowing through a concentric annulus. The nanofluid is prepared by suspending tetramethylammonium hydroxide (TMAH) coated Fe3O4 (magnetite) nanoparticles and gum arabic (GA) coated carbon nanotubes (CNTs) in water. Variable thermal conductivity and viscosity are used in simulations. The convective heat transfer coefficient of inner and outer walls, and total entropy generation augment with increasing Fe3O4 and CNT concentrations. Increasing radius ratio from 0.2 to 0.8, at CNT concentration of 1.1% and Fe3O4 concentration of 0.7%, decreases the heat transfer coefficient of inner wall by 85.05%, while increases that of outer wall by 35.49%. Models of convective heat transfer coefficient of both walls and total entropy generation are developed using neural network. Genetic algorithm is used with compromise programming to achieve optimal cases with maximum heat transfer and minimum entropy generation. In this method, the objective functions are mixed and the problem transforms into a single-objective optimization. Finally, applying the nanofluid with high concentrations is recommended for all conditions except the cases in which importance of entropy generation is considered much greater than that of heat transfer.

[1]  A. Sousa,et al.  Enhanced heat transfer and friction factor of MWCNT–Fe3O4/water hybrid nanofluids , 2014 .

[2]  Mohammad Reza Salimpour,et al.  Effect of temperature and concentration on thermal conductivity and viscosity of ferrofluid loaded with carbon nanotubes , 2016 .

[3]  J. Whitelaw,et al.  Convective heat and mass transfer , 1966 .

[4]  T. Wetzel,et al.  Numerical investigation of turbulent aided mixed convection of liquid metal flow through a concentric annulus , 2017 .

[5]  D. Nagesh Kumar,et al.  Multicriterion Analysis in Engineering and Management , 2010 .

[6]  V. Bianco,et al.  Numerical analysis of the Al2O3-water nanofluid forced laminar convection in an asymmetric heated channel for application in flat plate PV/T collector , 2018 .

[7]  Tülay A. Özbelge,et al.  Direct contact heat transfer between two immiscible liquids flowing in a horizontal concentric annulus , 1995 .

[8]  A. Bejan.  A Study of Entropy Generation in Fundamental Convective Heat Transfer , 1979 .

[9]  Rainer Laur,et al.  Two phase mixed convection Al2O3–water nanofluid flow in an annulus , 2011 .

[10]  W. Morris.  The development of laminar flow in the entrance region of a concentric annulus with a porous inner wall , 1971 .

[11]  Josua P. Meyer,et al.  The influence of multi-walled carbon nanotubes on single-phase heat transfer and pressure drop characteristics in the transitional flow regime of smooth tubes , 2013 .

[12]  D. Ganji,et al.  Nanofluid convective heat transfer using semi analytical and numerical approaches: A review , 2016 .

[13]  Wenhua Yu,et al.  Nanofluids: Science and Technology , 2007 .

[14]  Nanoparticles migration effects on magnetohydrodynamic (MHD) laminar mixed convection of alumina/water nanofluid inside microchannels , 2015 .

[15]  Vincenzo Bianco,et al.  Second Law Analysis of Al2O3-Water Nanofluid Turbulent Forced Convection in a Circular Cross Section Tube with Constant Wall Temperature , 2013 .

[16]  Seyed Mostafa Hosseinalipour,et al.  Numerical Study and Optimization of Hydrothermal Characteristics of Mn–Zn Ferrite Nanofluid Within Annulus in the Presence of Magnetic Field , 2014 .

[17]  Chia-Jung Hsu,et al.  Heat or mass transfer in laminar flow through a concentric annulus with convective flux at walls , 1966 .

[18]  Majid Siavashi,et al.  Numerical investigation of flow characteristics, heat transfer and entropy generation of nanofluid flow inside an annular pipe partially or completely filled with porous media using two-phase mixture model , 2015 .

[19]  H. K. Dawood,et al.  Heat transfer augmentation using nanofluids in an elliptic annulus with constant heat flux boundary condition , 2014 .

[20]  H Asan.  Natural convection in an annulus between two isothermal concentric square ducts , 2000 .

[21]  Geoffrey Ingram Taylor,et al.  Distribution of velocity and temperature between concentric rotating cylinders , 1935 .

[22]  Stephen U. S. Choi.  Enhancing thermal conductivity of fluids with nano-particles , 1995 .

[23]  Mohammad Reza Salimpour,et al.  Experimental investigation on laminar forced convective heat transfer of ferrofluid loaded with carbon nanotubes under constant and alternating magnetic fields , 2016 .

[24]  A. Behzadmehr,et al.  Numerical study of developing laminar forced convection of a nanofluid in an annulus , 2009 .

[25]  A. S. Shirani,et al.  Experimental investigation of TiO2/Water nanofluid effects on heat transfer characteristics of a vertical annulus with non-uniform heat flux in non-radiation environment , 2014 .

[26]  I. Pop,et al.  Irreversibility analysis of a vertical annulus using TiO2/water nanofluid with MHD flow effects , 2013 .

[27]  George C. Lisensky,et al.  PREPARATION AND PROPERTIES OF AN AQUEOUS FERROFLUID , 1999 .

[28]  S. A. Moshizi,et al.  Magnetic field effects on nanoparticle migration at mixed convection of MHD nanofluids flow in microchannels with temperature-dependent thermophysical properties , 2016 .

[29]  A. D'Orazio,et al.  An experimental study on thermal conductivity of F-MWCNTs–Fe3O4/EG hybrid nanofluid: Effects of temperature and concentration , 2016 .

[30]  Mehdi Bahiraei,et al.  Particle migration in nanofluids: A critical review , 2016 .

[31]  R. Sundara,et al.  Surfactant free magnetic nanofluids based on core-shell type nanoparticle decorated multiwalled carbon nanotubes , 2011 .

[32]  D. Kessler,et al.  An experimental study on the effect of ultrasonication on viscosity and heat transfer performance of multi-wall carbon nanotube-based aqueous nanofluids , 2009 .

[33]  Majid Siavashi,et al.  Heat transfer and entropy generation analysis of turbulent flow of TiO2-water nanofluid inside annuli with different radius ratios using two-phase mixture model , 2016 .