Avaliação experimental da transferência de calor e perda de pressão de nanofluidos em escoamento monofásico em dutos

Abstract

The present work deals on experimental study of thermal-hydraulic performance of nanofluids in single-phase flow inside tubes. Two different base fluids were used, water and ethylene glycol (50:50% wt) as well as OT-100 thermal oil. Silver, alumina, carbon nanotubes and diamond nanoparticles were dispersed into the base fluid using the two-step method. The tests were performed in single-phase flow, fully developed turbulent regime, inside smooth and horizontal tubes with uniform heat flux applied on the surface. An experimental bench was built and instrumented to guarantee the imposed conditions for the tests. The uniform heat flux was varied from 10 and 18 kW/m2, mass flow rate between 10 and 80 g/s. The inlet temperature was maintained constant in 15 °C, 25 °C e 45 °C. The thermophysical properties, thermal conductivity, viscosity and density were obtained experimentally and its values used to evaluate the heat transfer and pressure drop. In general, the heat transfer coefficient for nanofluids showed significant increments in comparison to the base fluids. The pressure drop for nanofluids was slightly higher or even the same order to those ones obtained by the base fluid. Models were proposed to evaluate the heat transfer coefficient and pressure drop as well as the thermal conductivity and viscosity showing good agreement with the experimental results.