Experimental Assessment of Turbulence Convective Heat Transfer and Pressure Drop in Annuli using Nanoporous Graphene non-Newtonian Nanofluid

Abstract

In designing equipment such as heat exchangers, heating and cooling systems, it is of great importance to provide higher convective heat transfer coefficients. Techniques aimed at enhancing heat transfer can increase the thermal efficiency of such industrial devices while minimizing the cost and size. One of the solutions specified for this problem is the utilization of nanomaterials. To prepare nanofluids, nanoparticles are dispersed in an appropriate base solution which forms a suspension [1] to [3]. The initial works on the formation of nanofluids were concentrated on using metal and metal oxide nanomaterials [4]. In this respective, Heris et al. [5] researched the effect of using Al2O3/water nanofluid on convective heat transfer from which it was found that by adopting 2.5 vol.% to 3 vol.% nanoparticles, the maximum increment of heat transfer is acquired. In another research, Patel et al. [6] showed that when a mixture of 11 % Au and Ag nanoparticles are used, thermal conductivity is augmented by about 21 %. Moreover, as reported by Zarringhalam et al. [7], by using CuO/water nanofluid in forced turbulent convection in two uniaxial tubes, heat transfer is increased by up to 57 % for the sample containing 2 vol.% nanoparticles. In addition, in some relative reviews [8] to [10], thermophysical properties of different nanofluids were compared and discussed, and the effect of each nanofluid on heat transfer capability of the industrial equipment was studied. In different studies, convective heat transfer of various nanofluids has been investigated in laminar [11] and [12] and turbulent [13] flow regimes. After using the metal and metal oxides, researchers started to use carbonaceous nanomaterials, which possessed higher thermal conductivity [14] and [15]. Among these efforts, Amrollahi et al. assessed the effect of multiwall carbon nanotubes on the convective heat transfer coefficient in laminar and turbulent flows [16]. For 0.1 wt.% nanoporous graphene in a circular tube, 34 % increment of convective heat transfer was obtained by Naghash et al. [17] in which the laminar flow regime was considered. Moreover, Amiri et al. [18] studied the thermophysical properties of the nanofluid prepared with functionalized graphene. They showed that the ethylene glycol-functionalized graphene in the mixed solution of water and ethylene glycol, the thermal conductivity was enhanced by Experimental Assessment of Turbulence Convective Heat Transfer and Pressure Drop in Annuli using Nanoporous Graphene Non-Newtonian Nanofluid Ghanbari, S. – Javaherdeh, K. Shahin Ghanbari – Kourosh Javaherdeh* University of Guilan, Faculty of Mechanical Engineering, Iran