Percorrer por autor "Souza, Reinaldo Rodrigues de"
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- Cooling performance of an acrylic serpentine with a rectangular cross sectionPublication . Nobrega, Glauco; Barbosa, F.M.; Soares, Filipe de Almeida da Silva; Ralha, R.; Souza, Reinaldo Rodrigues de; Ribeiro, J.E.; Moita, Ana S.; Lima, Rui A.In recent years, photovoltaic panels have been established as one of the main sources of electricity considered to be clean. Its efficiency and lifetime are greatly influenced by the operating temperature. Active cooling using cylindrical copper serpentines is one of the most common methods for many systems. However, due to the cylindrical geometry of the tubes, the contact with the plate is a point and its area tends to be zero. In this way, serpentines that provide a bigger contact area between the heat removal system and the solar panel board are desired. Serpentines manufactured by machining acrylic plates in CNC milling machines allow the construction of a channel with a rectangular cross-section with a considerable area of contact between the channel and the plate. The obtained results show that there was a significant improvement in the heat exchange between the plate and the thermofluid when the acrylic serpentine with a rectangular section was used.
- Experimental evaluation of green nanofluids in heat exchanger made oF PDMSPublication . Nobrega, Glauco; Souza, Reinaldo Rodrigues de; Cardoso, Beatriz D.; Afonso, Inês Santos; Pereira, José Eduardo; Cardoso, Elaine; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.Conventional methods for synthesizing metallic nanoparticles face challenges such as instability and environmental concerns. Therefore, new, simpler, and more eco-friendly methods are being explored. In this context, the study reports a green synthesis process to produce magnetic iron oxide nanoparticles using an aqueous extract of the alga Chlorella vulgaris. This process leverages natural resources to create a sustainable nanofluid known as green nanofluid. To evaluate the characteristics of this nanofluid, experimental measurements of wettability, viscosity, thermal conductivity, and qualitative stability analysis were conducted. An experimental setup consisting of a heat exchanger made of polydimethylsiloxane (PDMS) was used to assess the thermal performance and the results were compared to theoretical equations and numerical simulation. Additionally, thermographic imaging of temperature gradients as the fluids passed over the heated surface of the serpentine channel were made. The main findings confirmed that the nanofluid was more stable than that obtained by traditional methods and had a more uniform temperature distribution over the heat exchanger. The higher concentration exhibited superior thermal performance compared to DI-Water. Moreover, the green nanofluid was used at a weight concentration of 0.1 wt%, provided thermal performance results of nearly 4.5% superior to those estimated by the numerical model and 6.4% higher than those experimentally obtained with the base fluid, respectively. Finally, the results obtained for the nanofluid also showed an average increase of around 5% in the viscosity of the base fluid, with a more significant sedimentation at a concentration of 0.1 wt%.
- Experimental Investigation of Green Nanofluids: Assessment of Wettability, Viscosity and Thermal ConductivityPublication . Nobrega, Glauco; Cardoso, Beatriz D.; Barbosa, Filipe; Pinho, Diana; Abreu, Cristiano; Souza, Reinaldo Rodrigues de; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.Metallic nanoparticles are a type of nanomaterial synthesized from metallic precursors. Due to their unique physiochemical, electrical, and optical properties, metallic nanoparticles are widely studied and applied in various areas such as medicine, electronics, and heat transfer systems. However, conventional synthesis methods to produce metallic nanoparticles face challenges such as instability and environmental concerns, prompting the exploration of greener synthesis methods. Green synthesis uses natural resources like plants and algae as reducing agents, offering a more environmentally friendly approach for the synthesis of metallic nanoparticles. These green-synthesized metallic nanoparticles can enhance heat transfer by becoming part of nanofluids (NFs), which are colloidal mixtures of NPs in a fluid base. NFs, employed for heat transfer. As a result, it is essential to characterize the NFs regarding wettability, viscosity, and thermal conductivity. The results of the spectrophotometer confirmed the green synthesis of NPs, and it was observed that the increase in NP concentration impacted the contact angle, improving the ability to wet. The thermal conductivity is also modified, with an improvement of 11.3% compared to distilled water, without a significant increase in fluid viscosity.
- Exploring heat exchange in space: Recent advances in two-phase fluid experiments in microgravityPublication . Nobrega, Glauco; Afonso, Inês Santos; Cardoso, Beatriz D.; Souza, Reinaldo Rodrigues de; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.Thermal regulation has assumed a central role in space expeditions ever since the inception of Sputnik-1 in 1957. Throughout the years, numerous techniques have been developed to regulate temperatures in spacecraft and space habitats. Initially, passive systems like heat shields and thermal linings were employed, while newer missions embrace active cooling using fluids like ammonia and water. With significant advancements in lunar exploration, thermal management systems have been integrated to ensure effective heat protection and dissipation. Experiments carried out in drop towers, parabolic flights, sounding rockets, and aboard the International Space Station (ISS) have yielded valuable insights into the physics of fluids, pool boiling, boiling in two-phase flow, and cooling phenomena. However, conducting tests in microgravity conditions can lead to lower performances, and accurate numerical simulations remain a challenge. At present, various organizations are conducting research to drive progress in thermal management and enhance the technology of space devices. This review describes the most recent advances in two-phase fluid experiments in microgravity. Furthermore, the major challenges that persist in this field are presented and discussed, along with observations on trends and possibilities for the future of thermal control in space. This review attempts to be a relevant guide for future research and developments on thermal control in space.
- Recent developments on the thermal properties, stability and applications of nanofluids in machining, solar energy and biomedicinePublication . Nobrega, Glauco; Souza, Reinaldo Rodrigues de; Gonçalves, Inês M.; Moita, Ana S.; Ribeiro, J.E.; Lima, Rui A.In this review work, the recent progress made in the use of nanofluids (NFs) applied in three specific areas will be presented: machining, solar energy, and biomedical engineering. Within this context, the discussions will be guided by emphasizing the thermal and stability properties of these fluids. In machining, NFs play a prominent role in the processes of turning, milling, drilling, and grinding, being responsible for their optimization as well as improving the useful life of the tools and reducing costs. In the solar energy field, NFs have been used in the thermal management of the panels, controlling and homogenizing the operating temperature of these systems. In the biomedical area, the advantages of using NFs come from the treatment of cancer cells, the development of vaccines before the improvement of diagnostic imaging, and many others. In all lines of research mentioned in this study, the main parameters that have limited or encouraged the use of these fluids are also identified and debated. Finally, the discussions presented in this review will inspire and guide researchers in developing new techniques to improve the applications of NFs in several fields.
- A Review of Novel Heat Transfer Materials and Fluids for Aerospace ApplicationsPublication . Nobrega, Glauco; Cardoso, Beatriz D.; Souza, Reinaldo Rodrigues de; Pereira, José Eduardo; Pontes, Pedro; Catarino, Susana O.; Pinho, Diana M.D; Lima, Rui A.; Moita, Ana S.The issue of thermal control for space missions has been critical since the early space missions in the late 1950s. The demands in such environments are heightened, characterized by significant temperature variations and the need to manage substantial densities of heat. The current work offers a comprehensive survey of the innovative materials and thermal fluids employed in the aerospace technological area. In this scope, the materials should exhibit enhanced reliability for facing maintenance and raw materials scarcity. The improved thermophysical properties of the nanofluids increase the efficiency of the systems, allowing the mass/volume reduction in satellites, rovers, and spacecraft. Herein are summarized the main findings from a literature review of more than one hundred works on aerospace thermal management. In this sense, relevant issues in aerospace convection cooling were reported and discussed, using heat pipes and heat exchangers, and with heat transfer ability at high velocity, low pressure, and microgravity. Among the main findings, it could be highlighted the fact that these novel materials and fluids provide enhanced thermal conductivity, stability, and insulation, enhancing the heat transfer capability and preventing the malfunctioning, overheating, and degradation over time of the systems. The resulting indicators will contribute to strategic mapping knowledge and further competence. Also, this work will identify the main scientific and technological gaps and possible challenges for integrating the materials and fluids into existing systems and for maturation and large-scale feasibility for aerospace valorization and technology transfer enhancement.