Estudo experimental do desempenho térmico de trocadores de calor tipo multi microcanais operando com nanofluidos de grafeno

Abstract

The present work deals with the experimental evaluation of the thermal performance of a multi-microchannel heat exchanger operating with graphene nanofluids, with rectangular geometry in the microchannels. Thus, graphene nanofluids were experimentally analyzed in order to influence the main thermodynamic variables to have better heat transfer flowing inside the multi-microchannel heat exchangers. For this purpose, three mass concentrations of graphene nanoparticles dispersed in distilled water were produced with values Φ: 0,00025%; 0,00075% and 0,00125% wt, respectively. The microchannel heat exchanger was tested with the imposed heat flux varying between 7,29 – 51,09 kW/m2, mass flow between 29 – 116 kg/s.m2, inlet temperature in the microchannels between 25 and 45°C. The heat transfer values for the base fluid in a fully developed laminar regime were compared with classical models for microchannel heat exchangers, with the Shah and London correlation showing the best agreement when compared with the experimental data. In order to evaluate the thermophysical properties of graphene nanofluid samples, dynamic viscosity, specific mass and thermal conductivity were experimentally measured. The results showed that the highest average increment of the registered heat transfer coefficient has a value of 25,74% in relation to distilled water for the H2O+Graf_3 concentration. In terms of thermo-hydraulic performance, the most significant decrease in average thermal resistance was obtained by the H2O+Graf_3 concentration, which had a value of 0,1748W/°C. In relation to the head loss, it was found to increase according to the increase in the concentration of the nanofluid.