Browsing by Author "Cardoso, Beatriz D."
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- 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.
- Green synthesis of nanoparticles from olive oil waste for environmental and health applications: A reviewPublication . Afonso, Inês Santos; Cardoso, Beatriz D.; Nobrega, Glauco; Minas, Graça; Ribeiro, J.E.; Lima, Rui A.Environmental degradation is a growing concern, driving researchers to explore eco-friendly nanoparticle (NP) synthesis, for diverse applications. Within this context, the employment of olive oil waste (OOW) as a green source for the synthesis of NPs has emerged as a viable alternative to conventional techniques. The olive industry has a significant impact in the Mediterranean region, and alongside it, comes the OOW, where most of it cannot be left untreated. In the present review, a comprehensive overview of the NPs’ green synthesis derived from OOW and its potential applications in both environmental and health areas have been assessed, outlining its major challenges and potential outcomes for future research. Both principles and methods of green NPs synthesis were also explored, focusing on the unique properties of OOW as an effective agent for reduction and stabilization, as well as the characterization techniques used for characterizing the synthesized NPs. The OOW-derived NPs can have a wide variety of environmental applications including water purification, pollutant degradation, and remediation of contaminated environments. In the health field, the OOW applications include drug delivery systems, antimicrobial activity and cancer therapy. These OOW NPs have been successfully used as efficient drug delivery vehicles to cancer cells, enhancing treatment outcomes and potentially minimizing side effects. However, it is imperative to point out the importance of performing in-depth toxicity assessments, particularly at higher concentrations of NPs.
- Magnetoliposomes containing calcium ferrite nanoparticles for applications in breast cancer therapyPublication . Pereira, Daniela S.M.; Cardoso, Beatriz D.; Rodrigues, Ana Rita O.; Amorim, Carlos O.; Amaral, Vítor S.; Almeida, Bernardo G.; Queiroz, Maria João R.P.; Martinho, Olga; Baltazar, Fátima; Calhelha, Ricardo C.; Ferreira, Isabel C.F.R.; Coutinho, Paulo J.G.; Castanheira, Elisabete M.S.Magnetoliposomes containing calcium ferrite (CaFe2O4) nanoparticles were developed and characterized for the first time. CaFe2O4 nanoparticles were covered by a lipid bilayer or entrapped in liposomes forming, respectively, solid or aqueous magnetoliposomes as nanocarriers for new antitumor drugs. The magnetic nanoparticles were characterized by UV/Visible absorption, XRD, HR-TEM, and SQUID, exhibiting sizes of 5.2 +/- 1.2 nm (from TEM) and a superparamagnetic behavior. The magnetoliposomes were characterized by DLS and TEM. The incorporation of two new potential antitumor drugs (thienopyridine derivatives) specifically active against breast cancer in these nanosystems was investigated by fluorescence emission and anisotropy. Aqueous magnetoliposomes, with hydrodynamic diameters around 130 nm, and solid magnetoliposomes with sizes of ca. 170 nm, interact with biomembranes by fusion and are able to transport the antitumor drugs with generally high encapsulation effciencies (>=70%). These fully biocompatible drug-loaded magnetoliposomes can be promising as therapeutic agents in future applications of combined breast cancer therapy.
- Progress in Nanofluid Technology: From Conventional to Green Nanofluids for Biomedical, Heat Transfer, and Machining ApplicationsPublication . Cardoso, Beatriz D.; Souza, Andrews; Nobrega, Glauco; Afonso, Inês Santos ; Neves, Lucas Boniatti; Faria, Carlos; Ribeiro, J.E.; Lima, Rui A.Nanofluids (NFs), consisting of nanoparticles (NPs) suspended in base fluids, have attracted growing interest due to their superior physicochemical properties and multifunctional potential. In this review, conventional and green NF technology aspects, including synthesis routes, formulation, and applications, are discussed. Conventional NFs, involving NPs synthesized using physical and chemical approaches, have improved NP morphology control but are likely to cause environmental and safety concerns. In contrast, green NFs that are plant extract, microorganism, and biogenic waste-based represent a sustainable and biocompatible alternative. The effect of key parameters (e.g., NP size, shape, concentration, dispersion stability, and base fluid properties) on the performance of NFs is critically examined. The review also covers potential applications: in biomedical engineering (e.g., drug delivery, imaging, theranostics, and antimicrobial therapies), in heat transfer (e.g., solar collectors, cooling electronics, nuclear reactors), and precision machining (e.g., lubricants and coolants). Comparative insights regarding green versus conventionally prepared NFs are provided concerning their toxicity, environmental impact, scalability, and functional performance across various applications. Overall, this review highlights the new promise of both green and conventional NFs and provides key opportunities and challenges to guide future developments in this field.
- 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.