Experimental assessment of turbulence convective heat transfer and pressure drop in annuli using nanoporous graphene non-newtonian nanofluid

english

2019

volume 65, issue 9

annular tubes   nanofluids   nanoporous graphenes   pressure drops   thermal performance factors

Univerza v Ljubljani, Fakulteta za strojništvo
(Obvezni izvod spletne publikacije)

In the current research work, turbulence convective heat transfer coefficient enhancement and pressure drop of nanoporous graphene non-Newtonian nanofluid were investigated in an annular tube in the developing region. The nanofluid was prepared by using nanoporous graphene in different concentrations of 0.05 wt.%, 0.1 wt.%, and 0.2 wt.% in an aqueous solution of carboxyl methyl cellulose (CMC). All thermophysical and rheological characteristics were evaluated, and pseudo-plastic (shear-thinning) rheological behaviour was observed for all samples. The results revealed that adding 0.2 wt.% nanoporous graphene to the base fluid leads to 12.4 % and 39.4 % enhancement of thermal conductivity and heat transfer coefficient, respectively. This enhancement trend was almost linear for the concentrations lower than 0.1 wt.% after which the enhancement rate was reduced significantly. Moreover, the results showed that when 0.05 and 0.1 wt.% nanoporous graphene was adopted, the thermal performance factor (TPF) was increased by 8.7 % and 16.7 %, respectively, and doubling the nanoparticle concentration from 0.1 wt.% to 0.2 wt.% could not augment the TPF; however, considering the assessed pressure drop, it also decreased it by 2.5 %. The increase of the Reynolds number led to an increase in heat transfer coefficient of all samples.

04.10.2019