Avaliação experimental do desempenho termohidráulico de nanofluidos de grafeno em um sistema de arrefecimento automotivo

Abstract

This work presents an experimental investigation of the thermal-hydraulic performance of water-based ethylene glycol nanofluids with a volumetric concentration (50% vol.) in automotive radiators. The tests were performed on a modified experimental workbench and adapted to simulate the working conditions of a real automotive cooling system. Nanofluids were prepared at three different volumetric concentrations (0.01, 0.05 and 0.1%). Thermophysical properties such as thermal conductivity, viscosity and density were measured experimentally and compared to models found in the literature. The test section was divided into two working circuits, hot circuit (cooling fluid) and air circuit. In the hot circuit, the mass flow rate varied between 0.08 and 0.11 kg/s, presenting a laminar flow regime and the inlet temperature ranged from 55 to 85 °C. For the air circuit, the temperature of the incident air on the radiator remained constant at 25 °C for all tests. The air velocity was maintained constant at 2.1, 2.4 and 2.8 m/s. From the calculated parameters such as heat transfer rate, global heat transfer coefficient and pumping power, an analysis was conducted of the thermal-hydraulic performance of nanofluids for their possible use as cooling fluid with improved thermophysical properties. The results for thermophysical properties showed an increase of 9.2% in the thermal conductivity for nanofluids with higher concentration as well as the viscosity and density increased 13.5 and 0.55%, respectively. In terms of thermal-hydraulic performance, the results showed a reduction of 2% in average for the highest concentration tested. The heat transfer rate of the nanofluids was 9.6% lower than the base fluid for ^=0.05% vol, and 3.37% lower for ^=0.10% vol. Finally, the pumping power for the nanofluids increased 2%, in average, compared to the base fluid.