Nanofluids: Thermophysical analysis and heat transfer perfortmance

Abstract

Consulta en la Biblioteca ETSI Industriales (Riunet)

[EN] Nanofluids can be described as colloidal suspensions of solid particles smaller than 100 nm diluted in a base fluid. According to the literature nanofluids have better thermophysical properties and might achieve better cooling performance compared to conventional liquids. The current Master Thesis is divided into two main sections; the first part consists of the analysis of thermal conductivity and viscosity of nanofluids, while the second part is about the performance of forced convective heat transfer in laminar flow with nanofluids. For the evaluation of thermal conductivity and viscosity, which are the main two important thermo-physical properties, different nanoparticles were tested, such as Al2O3 (with 3-50 w%), TiO2 (with 3-40 w%), SiO2 (with 3-45 w%) and CeO2 (with 3-20 w%); all of them dispersed in distilled water. The results have been compared with the results provided by the Chemical Department of University of Birmingham for validation/comparison. Moreover, temperature effect on viscosity and thermal conductivity has been studied as well. Furthermore, some theoretical models have been used in order to understand the behavior of thermal conductivity and viscosity. For the second part, several nanofluids have been tested to evaluate heat transfer coefficient in a horizontal open micro-tube test section under laminar flow regime. The test section had an inner diameter of 0.50 mm and 30 cm length made of stainless steel. Along the pipe, seven thermocouples were unevenly attached on the outer surface in order to measure the local wall temperatures. Furthermore, two more thermocouples were used to measure inlet and outlet temperatures. A differential pressure transducer was used to measure pressure drop, and a DC power supply was used to apply constant heat flux along the test section; moreover, a double syringe pump were used to inject nanofluids inside the microtube.