Experimental studies on pressure drop/friction factor of CNT nanofluids flowing through helical coils and development of a new empirical correlation

Abstract

This paper reports the hydrodynamic characteristics of CNT nanofluids prepared using mixed surfactant system flowing through helically coiled tubes under laminar conditions. The curvature ratio was varied from 0.036 to 0.067 and CNT concentration from 0 to 0.051 vol%. Results showed that friction factor of CNT nanofluid was higher than water for all range of parameters studied. Friction factor was found to be dependent on the volumetric concentration of CNT as well as on curvature ratio of helical coil. A maximum of 69% enhancement in friction factor was calculated with respect to water when CNT nanofluid of 0.051 vol% flowing through helical coil of curvature ratio;$\mathrm{ }{d}_t/D_c$ 0.067. On increasing the curvature ratio;$\mathrm{ }{d}_t/D_c$ from 0.036 to 0.067, friction factor increased by 46% at CNT concentration 0.051 vol%. Based on the experimental data, an empirical correlation has been proposed to evaluate friction factor of CNT nanofluids flowing through helical coils. The proposed correlation explains the present experimental data within ±11%.

GRAPHICAL ABSTRACT

Keywords:

• Mixed surfactant
• CNT nanofluid
• helical coils
• empirical correlation
• friction factor