Single phase flow of nanofluid including graphite and water in a microchannel

Abstract

In this study, convective heat transfer performance of a nanofluids containing graphite is studied in an industrial microchannel. In the experiments, initially, to prepare nanofluids at the volume fraction values of 0.5, 1, 1.5, 2%, distilled water has been employed as the base liquid. To provide sedimentation and stabilization of nanofluids in distilled water, Cetyltrimethylammonium bromide (CTAB) is utilized as surfactant. Thermophysical properties of nanofluids such as thermal conductivity, dynamic viscosity, and specific heat are determined experimentally. Furthermore, by building an experimental setup, in the temperature range of 20-30 degrees C and with temperature intervals of 2 degrees C, performance experiments are carried out in a microchannel of which hydraulic diameter is 1.6 x 10(-3) m. Additionally, experiments have been conducted using nanofluids at different volumetric rates from 1 to 7 l min(-1), heat fluxes from 100 to 1100 W, and volume fractions from 0.5 to 2%. Measuring heat flux, temperature, and flow rate, outcomes such as convective heat transfer coefficient, Reynolds number, and Nusselt number are calculated. The validation process of the experimental results has been performed by plotting the figures of Nusselt numbers vs Reynolds ones, and heat transfer coefficient vs supplied heat considering distilled water and nanofluids having various volumetric proportions. Regarding with the performance of nanofluids against distilled water under similar operating conditions, some proportional positive increase are acquired. Using outcomes attained from experiments, new correlations for Nusselt number have been derived with the R-2 values around 0.96, and afterward by means of those correlations experimental data have been compared with those in the literature. A large number of measured and calculated data are given in the paper for other researchers to validate their theoretical models.