Thermally and acoustically driven transport in supercritical fluids

Supercritical fluids are fluids at temperature and pressure above their respective critical values. Such fluids are increasingly being used in power generation, refrigeration and chemical process industry. The objectives of the current research were to develop a fundamental understanding of the transport phenomena in near-critical supercritical fluids via high-resolution numerical simulations and careful experiments for improved design of industrial processes and applications that employ supercritical fluids. A set of synergistic experimental and numerical studies were proposed in this research. Four main focus areas under the broad spectrum of supercritical fluid transport were chosen - (a) characterization of thermoacoustic transport, (b) interaction of thermoacoustic transport with natural convection, (c) characterization of acoustically augmented transport and (d) enhancement of mass transport using acoustic waves. A numerical model to simulate thermoacoustic convection in near-critical fluids was developed. In the computational model, the conservation equations were solved along with a real-fluid equation of state for supercritical fluid and variable thermo-physical properties. Thermoacoustic waves in near-critical carbon dioxide were also investigated experimentally on acoustic time scales using a fast response measurement system. The predicted results from the calculation and the measurements provide interesting details regarding the thermal transport mechanisms at near-critical states. The numerical model was applied to investigate the interaction of buoyancy driven flows with thermoacoustic convection in near-critical supercritical fluids. This model can be extensively used for studying the steady-state thermal transport and stability behavior of near-critical fluids. Mechanically driven acoustic waves in supercritical fluid generated by a vibrating wall in a cylindrical resonator were studied both numerically and experimentally. The simulations revealed interesting steady-periodic flow patterns in the resonator filled with near-critical fluid due to the fluctuations caused by the vibrating wall. High-fidelity computational fluid dynamics models of mass transport processes in supercritical fluid extraction systems were also developed. A novel application of acoustically driven transport in supercritical fluid was demonstrated numerically for the supercritical fluid extraction process. The numerical predictions indicated major improvements in the extraction yield due to the application of acoustic waves and can be utilized in the design and optimization of supercritical fluid extraction systems.Ph.D., Mechanical engineering -- Drexel University, 201

CO2 capture using membrane contactors: a systematic literature review

With fossil fuel being the major source of energy, CO2 emission levels need to be reduced to a minimal amount namely from anthropogenic sources. Energy consumption is expected to rise by 48% in the next 30 years, and global warming is becoming an alarming issue which needs to be addressed on a thorough technical basis. Nonetheless, exploring CO2 capture using membrane contactor technology has shown great potential to be applied and utilised by industry to deal with post- and pre-combustion of CO2. A systematic review has been conducted to analyse and assess CO2 removal using membrane contactors for capturing techniques in industrial processes. The review began with a total of 2650 papers, which were obtained from three major databases, and then were excluded down to a final number of 525 papers following a defined set of criteria. The results showed that hollow fibre membranes have demonstrated popularity, as well as the use of amine solvents for CO2 removal. This current systematic review in CO2 removal and capture is an important milestone in the acknowledgment of up to date research with the potential to serve as a benchmark databank for further research in similar areas of work. This study provides the first systematic enquiry in the evidence to research further sustainable methods to capture and separate CO2

Analysis of heat and mass transfer in membrane-based absorbers with new working fluid mixtures for absorption cooling systems

Absorption refrigeration technology, which has the ability to utilize heat directly for cooling purposes, has been one of the most widely used technologies for refrigeration and cooling applications since the early stages of refrigeration technology. Working fluid mixtures employed in the absorption cooling systems are environmental friendly and do not contribute in green house gas emission when compared to vapour compression systems which also use costly mechanical energy input. However, high initial costs and bigger size are some of the main obstacles that impede their wide use in small scale residential buildings and transport sector. In order to overcome these obstacles, design and configuration of the system and its components need to be reinvestigated in order to achieve compact components and reduce the size of the system. Use of membrane contactors in the form of hollow fiber membrane module or plate-and-frame membrane module is one of the alternatives to achieve compact components. Absorber is an important component of the absorption refrigeration system and plays a critical role in the overall performance, size, and capital cost of the system. In this study, numerical analyses are performed to evaluate the performance of a plate-and-frame membrane contactor based absorber employing water/(LiBr + LiI + LiNO3 + LiCl) and water/(LiNO3+KNO3+NaNO3) working fluid mixtures for air cooled absorption cooling systems and multi-stage high temperature heat sources applications, respectively. CFD tool ANSYS/FLUENT 14.0 is used to perform the simulation and investigate in detail the heat and mass transfer mechanisms and the fluid dynamics behaviour at local levels in the channels. Moreover, a MATLAB code is developed to investigate the effect of membrane material characteristics and operating conditions on the absorption performance of the absorber. This study recommends optimum operating and design parameters to effectively utilize the membrane based absorber

Preparation, Proximate Composition and Culinary Properties of Yellow Alkaline Noodles from Wheat and Raw/Pregelatinized Gadung (Dioscorea Hispida Dennst) Composite Flours

The steady increase of wheat flour price and noodle consumptions has driven researchers to find substitutes for wheat flour in the noodle making process. In this work, yellow alkaline noodles were prepared from composite flours comprising wheat and raw/pregelatinized gadung (Dioscorea hispida Dennst) flours. The purpose of this work was to investigate the effect of composite flour compositions on the cooking properties (cooking yield, cooking loss and swelling index) of yellow alkaline noodle. In addition, the sensory test and nutrition content of the yellow alkaline noodle were also evaluated for further recommendation. The experimental results showed that a good quality yellow alkaline noodle can be prepared from composite flour containing 20% w/w raw gadung flour. The cooking yield, cooking loss and swelling index of this noodle were 10.32 g, 1.20 and 2.30, respectively. Another good quality yellow alkaline noodle can be made from composite flour containing 40% w/w pregelatinized gadung flour. This noodle had cooking yield 8.93 g, cooking loss 1.20, and swelling index of 1.88. The sensory evaluation suggested that although the color, aroma and firmness of the noodles were significantly different (p ≤ 0.05) from wheat flour noodle, but their flavor remained closely similar. The nutrition content of the noodles also satisfied the Indonesian National Standard for noodle. Therefore, it can be concluded that wheat and raw/pregelatinized gadung composite flours can be used to manufacture yellow alkaline noodle with good quality and suitable for functional food

Gas Capture Processes

This book introduces the recent technologies introduced for gases capture including CO2, CO, SO2, H2S, NOx, and H2. Various processes and theories for gas capture and removal are presented. The book provides a useful source of information for engineers and specialists, as well as for undergraduate and postgraduate students in the fields of environmental and chemical science and engineering

Overview of Membrane Science and Technology in Portugal

Funding Information: Acknowledgments: The authors acknowledge Tiago Araújo for his valuable contribution in writing—original draft preparation—the carbon molecular sieve membranes content. LCT is grateful to Fundação para a Ciência e a Tecnologia (FCT/MCTES) for her assistant researcher contract under Scientific Employment Stimulus (2020.01555.CEECIND). DMFS thanks FCT/MCTES for a research contract in the scope of programmatic funding UIDP/04540/2020. Funding Information: Funding: This work was supported by Associate Laboratory for Green Chemistry—LAQV, which is financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/50006/2020), Research project PTDC/EQU-EPQ/29579/2017 funded by FCT/MCTES “Programa Operacional Regional de Lisboa, FEDER”, project Nanoart PTDC/CTM-BIO/6178/2014 and CeFEMA with grant number 325UID/CTM/04540/2013 funded by FCT/MCTES. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Membrane research in Portugal is aligned with global concerns and expectations for sustainable social development, thus progressively focusing on the use of natural resources and renewable energy. This review begins by addressing the pioneer work on membrane science and technology in Portugal by the research groups of Instituto Superior Técnico—Universidade de Lisboa (IST), NOVA School of Science and Technology—Universidade Nova de Lisboa (FCT NOVA) and Faculdade de Engenharia—Universidade do Porto (FEUP) aiming to provide an historical perspective on the topic. Then, an overview of the trends and challenges in membrane processes and materials, mostly in the last five years, involving Portuguese researchers, is presented as a contribution to a more sustainable water–energy–material–food nexus.publishersversionpublishe

Membrane Distillation Development for Concentrated Solar Thermal Systems

At present, both energy and water are predominantly supplied through the burning of fossil fuels. Going forward, new demand (and the replacement of retiring assets) is increasingly being met by sustainable technologies—largely driven by solar energy. This PhD thesis aimed to address two pressing Sustainable Development Goals, set out by the United Nations, ‘affordable and clean energy’ and ‘clean water’, by developing solar-driven desalination (D) technologies using two different approaches: ‘direct solar-desalination’ and ‘indirect solar-desalination’. The first approach used feedwater heated directly by a solar thermal collector for vacuum membrane distillation (VMD) for a small residential scale. In contrast, the second approach targeted the indirect use of energy from a concentrated solar power (CSP) plant via more well-established desalination processes for large-scale applications. In the first approach, this thesis successfully designed and manufactured the first hollow fiber-based multi-effect VMD that can internally recover the latent heat of the permeate vapor between effects using metallic hollow helical baffles, reducing the energy consumption by more than 60% and producing up to 20 L/h at less than 2 USD per cubic meter of freshwater. In the second approach, detailed numerical simulations found that replacing the power block’s condenser with a multi-effect distillation (MED) system can significantly improve the CSP plant’s payback period by 5% – 13% but at the expense of reducing the thermal efficiency by 7% – 11.5%. Another solution is to utilize some of the generated electricity from the CSP plant to operate reverse osmosis (either on-site or at a facility near the coast); however, this was found to hurt the plant’s revenue since some of the valuable electricity generated is consumed by the RO plant, instead of being sold to the grid. Another CSP-D solution is to replace the conventional steam Rankine cycle with a supercritical CO2 cycle, which can provide the necessary high-temperature waste heat to a MED process without any thermal efficiency reduction. Overall, this thesis examines the potential of utilizing the endless supply of solar energy to produce sustainable clean energy and freshwater that can ‘green-terraform’ arid lands and help water-stressed communities

Membrane and Membrane Reactors Operations in Chemical Engineering

This Special Issue is aimed at highlighting the potentialities of membrane and membrane reactor operations in various sectors of chemical engineering, based on application of the process intensification strategy. In all of the contributions, the principles of process intensification were pursued during the adoption of membrane technology, demonstrating how it may lead to the development of redesigned processes that are more compact and efficient while also being more environmental friendly, energy saving, and amenable to integration with other green processes. This Special Issue comprises a number of experimental and theoretical studies dealing with the application of membrane and membrane reactor technology in various scientific fields of chemical engineering, such as membrane distillation for wastewater treatment, hydrogen production from reforming reactions via inorganic membrane and membrane photoassisted reactors, membrane desalination, gas/liquid phase membrane separation of CO2, and membrane filtration for the recovery of antioxidants from agricultural byproducts, contributing to valorization of the potentialities of membrane operations