Experimental study on convective heat transfer, thermo-physical properties and pressure drop of low concentration COOH- Functionalized MWCNTs/water nanofluid flow

In this paper, an experimental study carried out to investigate the turbulent convective heat transfer performance of low concentration of COOH-functionalize MWCNT/water nanofluid flowing through a circular tube. The effect of solid concentration from 0.0005 to 0.01 on convective heat transfer studied at Reynolds number in the range between 5000 to 27000.Also Thermal conductivity and dynamic viscosity of nanofluid has been measured experimentally in various temperatures and solid volume fractions. It is observed that both thermal conductivity and dynamic viscosity of nanofluid strongly depend on temperature and solid concentration. Therefore two new correlations as a function of temperature and concentration were proposed for predict the thermal conductivity of functionalized MWCNTs/water nanofluid.
In addition,Heat transfer coefficient, Nusselt number, pressure drop and thermal performance factor of nanofluid were presented for different volume fractions. The experimental results clearly indicate that increase in both heat transfer coefficient and Thermal performance factor is obtained by increasing solid concentration. In average, 78% increase in heat transfer coefficient, 36.5% increase in average Nusselt number and 27.3% penalty in pressure drop was observed at the highest concentration of MWCNTs in water abstract.