Projeto termohidráulico de um trocador de calor de bancada para avaliação do rendimento térmico de nanofluidos

Abstract

Nanofluids are produced by dispersing nanoscale particles in a base fluid, which can alter properties such as thermal conductivity, viscosity, density, and specific heat. Studies have indicated that the addition of nanofluids can improve the performance of heat exchangers, mainly by intensifying heat transfer through conduction and convection. In addition, depending on the composition, nanoparticle concentration, and operating conditions, nanofluids may offer advantages related to improved thermal efficiency and the possibility of developing more compact equipment. However, knowledge gaps still remain in this field, such as the proper selection of nanofluids, the stability of nanoparticles in the base fluid, the influence of volume fraction, the impact of viscosity on flow, the optimization of heat exchanger design, and the understanding of the mechanisms involved in the heat transfer. In this context, the main objective of this study was to design a flexible operating bench-scale heat exchanger for assessing the thermal performance of nanofluids. To achieve this objective, several steps were carried out, beginning with a comprehensive literature review on nanofluids and heat exchangers. In the sequence, the detailed thermohydraulic design of a bench-scale heat exchanger was developed, taking into account the selection of the equipment type, its dimensions, geometry, construction materials, and operating conditions. The project included the definition of a concentric tube heat exchanger, the development of the CAD model, and the selection of hydraulic components, reservoirs, pumps, the thermal control system, instrumentation, and structural elements required for assembling the bench. Aspects related to material compatibility with nanofluids, operational flexibility of the system, and the possibility of operation under different flow configurations were also considered. The thermohydraulic evaluation was conducted under several operating parameters such as the Reynolds number, Nusselt number, convective coefficient, overall heat transfer coefficient, number of transfer units, thermal effectiveness, and heat transfer rate. Additionally, numerical simulations were performed to evaluate the thermal behavior of the heat exchanger under defined operating conditions, making it possible to observe the temperature distribution, the evolution of the transient regime, and the thermal interaction between the hot and cold streams. Thus, this work developed a theoretical and methodological basis for the construction and future use of an experimental bench intended for the study of the thermal and hydraulic performance of nanofluids in heat exchangers.