Effect of magnetic field on thermo-physical and hydrodynamic properties of different metals-decorated multi-walled carbon nanotubes-based water coolants in a closed conduit Mehdi Shanbedi 1 • Ahmad Amiri 2 • Saeed Zeinali Heris 1 • Hossein Eshghi 3 • Hooman Yarmand 2 Received: 1 January 2017 / Accepted: 9 August 2017 Ó Akade ´miai Kiado ´, Budapest, Hungary 2017 Abstract In this paper, the thermo-physical and hydrody- namic properties of heat transfer nanofluids containing metal nanoparticles-decorated multi-wall carbon nanotube (MWCNT) are reported. To this end, Cu-decorated MWCNT, Fe-decorated MWCNT, and Ni-decorated MWCNT (covalently functionalized samples) were syn- thesized with pre-functionalization with the aspartic acid as the hydrophilic chain. To have a comprehensive compar- ison, water-based non-covalently functionalized MWCNT nanofluids were also synthesized. A significant increase in the thermal and electrical conductivities of heat transfer nanofluids containing metal nanoparticles-based MWCNT as compared to the non-covalently functionalized sample as well as water has been determined at the same opera- tional conditions. All the prepared nanofluids are stable and the viscosity and density remained approximately the same after loading additives. The present paper also focused on the study of the role of weight concentrations of additives, flow rate and thermo-physical properties of the prepared nanofluids on the convective heat transfer rate and hydro- dynamic performances in the laminar flow. Further, the convective heat transfer coefficient, pressure drop, friction factor, performance index and pumping power variation were also investigated under applied magnetic field, which improves the overall thermal performance of the closed conduit insignificantly. Keywords Carbon nanotubes  Functionalization  Thermo-physical properties  Heat transfer  Hydrodynamic  Magnetic field List of symbols C p Specific heat (J kg -1 K -1 ) D Diameter (m) E Error h Heat transfer coefficient (W m -2 K -1 ) L Tube length (m) _ m Mass flow rate (kg s -1 ) q 00 Heat flux (W m -2 ) Q Heat transfer rate (W) T Temperature (°C) U Velocity (m s -1 ) A Cross section of the tube (m 2 ) f Friction factor W Pumping power V Voltage (V) I Current (A) Greek symbols q Density (kg m -3 ) l Viscosity (Pa s) e Performance index Dp Pressure drop (Pa) Subscripts b Bulk fluid bf Base fluid & Mehdi Shanbedi mehdi.shanbedi@stu-mail.um.ac.ir & Ahmad Amiri ahm.amiri@gmail.com 1 Department of Chemical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran 2 Department of Mechanical Engineering, University of Malaya, Kuala Lumpur, Malaysia 3 Department of Chemistry, Faculty of Science, Ferdowsi University of Mashhad, Mashhad, Iran 123 J Therm Anal Calorim DOI 10.1007/s10973-017-6628-2