Avaliação experimental do desempenho termo-hidráulico de nanofluidos de nanotubos de carbono de parede simples em escoamento monofásico em regime turbulento

Abstract

The present work deals on experimental study of thermal-hydraulic performance of single walled carbon nanotubes nanofluids dispersed in distilled water. 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 modified to guarantee the nominal conditions imposed for the tests. The mass flow rate varied between 30 and 80 kg/s, related to Reynolds numbers between 4000 and 22000. The heat flux varied from 14 up to 22 kW/m2 and the inlet temperature was maintained constant in 25, 30 and 35°C. The physical properties of nanofluids such as thermal conductivity and viscosity were measured experimentally and its values used to evaluate the heat transfer coefficient. Pressure drop, friction factor and pumping power were also analyze. Effects such as nanoparticle shape, defined by the aspect ratio, and mass concentration of nanoparticles were evaluate as well. The heat transfer coefficient of SWCNT/water nanofluids increased, in average, 11.3%, in function of Reynolds number. In relation to the mass velocity, the heat transfer coefficient decreased 6.9%, in average, in comparison with the base fluid. Finally, the experimental results for pressure drop of nanofluids were, in average, 7.3%, greater than the base fluid.