Papers by Author: J.A. Simões

Abstract: Polymethylmethacrylate has been used in orthopaedic surgery for the fixation of prosthetic implants for forty years. Cement characteristics, namely rheological and flow properties, greatly affect implant success. Moreover, knowing predictable and reproducible cement flow characteristics allows the surgeon to establish more rigorous handling conditions and prosthesis precise positioning. In contrast to the relatively large amount of work on mechanical properties of bone cements, few data have been published oh their rheological properties. Computational fluid dynamics (CFD) codes using VOF (volume-of-fluid) method has proven to be a useful and robust tool method to simulate multi-material flows with immiscible interfaces. This work explores and describes the possibility of to use a commercial available CFD package (ANSYS CFX®) in the study of PMMA flow on a small dimension multy-channel system.

Abstract: Heat transfer fluids play an important role in many industrial sectors. However, the low heat transfer characteristics of conventional fluids obstruct the performance enhancement and the high compactness of heat exchangers. In order to improve thermal characteristics of the conventional fluids, nanofluids are prepared by adding multi walled carbon nanotubes (CNTs) with base fluids. Though different experimental studies on nanofluids are available, theoretical models are also needed to predict its thermal behaviour. This work intends to address dimensional analysis using the Buckingham Pi theorem to develop an empirical model for predicting thermal characteristics of nanofluids. The latter will be achieved through the use of operational variables and physical properties for the identification of detrimental factors which eventually lead to the thermal enhancement of nanofluids. It can be observed from this analysis that volume fraction and temperature of the nanofluids are the most influencing parameters on the nanofluids thermal conductivity. In what concerns heat transfer coefficient, it is the velocity of the nanofluid that plays a critical role apart from the afore mentioned two parameters. Therefore it is believed that by controlling these parameters, the thermal effectiveness of the nanofluids can be established.