Avaliação do desempenho de um nanofluido de ouro em trocador de calor de casco e tubo helicoidal

Abstract

Nanofluids, which are suspensions of nanoparticles in base-fluid, have been considered potential cooling liquids, due to their thermal conductivity in some cases superior to that of conventional liquids. The goal of this work was to assess the performance of gold nanofluid as a cooling liquid in a shell and helically coiled tube heat exchanger (TCCTH) using water as hot fluid. Heat transfer tests were carried out using water and gold nanofluid under different conditions of the system, aiming to know, from a multilevel factorial experimental design, the effects of the volumetric fraction of the nanoparticles, the flow of the fluids involved and the temperature of the hot fluid, on the effectiveness of TCCTH. The gold nanofluid was produced by the modified Turkevich method, and the results of the characterization were spherical nanoparticles with mean diameter of (14±2) nm. Two dilutions of the concentrated nanofluid were made, whose volumetric fractions of gold nanoparticles in the diluted nanofluid were 1.63x10-5% (Nanofluid A) and 6.53x10-5% (Nanofluid B). Heat transfer tests were performed at 20, 30 and 40 L/h for both fluids (hot and cold), and hot fluid inlet temperatures of 40, 50 and 60 ° C. The maximum effectiveness was observed for Nanofluid A, at the lower flow rate and at the higher hot fluid inlet temperature. With regard to the comparison of the results obtained from the hydraulic diameters (Dhid) referring to the propositions of models from literature with the experimental results, it was verified that the Dhid proposed by Salimpour (2009) presented results that more approached the experimental values, followed by Incropera et al. (2011), and finally by Jamshidi et al. (2013).