Search

An investigation of 2D laminar magnetohydrodynamics couple stress hybrid nanofluid is performed with inclined magnetic field over the stretching/-shrinking surface embedded in porous media. The quiescent water-based nanofluid is subjected to the external force by pulling the two ends of the sheet with equal magnitude and opposite forces. The governing nonlinear partial differential equations (PDEs) are converted into nonlinear ordinary differential equation (ODE) by adopting the suitable similarity transformation and obtains the analytical solution for velocity. The hydrodynamic characteristics are investigated in the presence of different physical parameters such as couple stress parameter, magnetic parameter, mass transpiration, stretching/shrinking parameter, porosity and magnetic parameter with the help of graphs. The thermal properties are enhanced by adding the copper and alumina nanoparticles to the base fluid. The result of this study has important applications in industrial and scientific are such as polymer extrusion process, liquid crystal solidification, cement artificial foams production, ceramics, metal spinning, and roofing shingles and also have possible technological applications in fluid-based systems involving stretchable/shrinkable materials.

In this study, the important role of radiating gas effect to obtain higher thermal performance in a planar double-pass solar gas heater (DP-SGH) is discussed. Two inclined passages are deployed in ...

According to the global consensus on mitigation of greenhouse gas and human footprint as well as improvement of industrial sustainability by the exploitation of renewable energy, the mission of this study dedicated to the performance enhancement of planar solar chimneys in converting much more solar radiation into air enthalpy by vortex generation technique. For this purpose, a passive vortex generator (VG) as an inexpensive but effective approach is employed for the enhancement of heat transfer. The well-developed commercial software of COMSOL Multiphysics was used for two-way modeling and simulation of sophisticated fluid-solid interaction in transient turbulent natural convection heat transfer phenomena. An extensive comparison has been made between two configurations of solar chimney namely with and without VG. According to the numerical results, the natural vibration of elastic VG induces moving vortices into the flow field which is also responsible for the enhancement of natural convection heat transfer by mixing and reducing the thermal boundary layer. Moreover, the VG significantly improves Δ T o u t l e t up to 300% and also decreases the temperature of the absorber surface more than 50% which is under constant heat flux. Both of these factors lead to higher performance for natural air heater.

In this study, a new application of a Tesla turbine (TT) is presented in which a TT is introduced as a promising solution to enhance the energy efficiency of refrigeration cycles. For this special purpose, a TT is represented as a regenerative system that minimizes the wasted energy without compromising the system output quality or sacrificing standards of design and move one step forward, towards more sustainable industries. To achieve this goal, a 3D thermohydrodynamic analysis of the Newtonian turbulent compressible flow of high-pressure methane through a Tesla turbine has been performed under different configurations and operational conditions. Methane was defined as a real gas through the Redlich–Kwong equation of state. The complex unstructured grid generation was employed to produce a low-skewness mesh for a CFD model on the commercial software of ANSYS Fluent for simulation of heat and mass transfer by FVM. As a result of the present study, practical design rules are proposed to support engineers defining optimized TTs for predetermined operating conditions, namely regarding power output, disc sizes and angular velocity. Keywords: Energy efficiency, Tesla turbine (TT), Compressible turbulent flow, High-pressure methane, Refrigeration cycles

This study addresses a new generation of adaptable intelligent control systems for energy management. The proposed approach consists of a high-level predictive control system based on advanced simulation and optimization algorithms which interact with conventional machine-level controllers of HVAC systems, e.g., PID, in order to define optimized set points considering current and forecasted operation conditions, minimizing a predefined objective cost function, e.g., energy consumption, subjected to maintain predefined levels of comfort. The flexibility of the proposed architecture and the development of reliable surrogate models based on robust machine learning techniques are key features to combine green building requirements while granting or even improving occupant comfort. A first version of the proposed system was developed, and preliminary results emphasize its role in the path of transition to intelligent green buildings as a part of new buildings or, more important, as a retrofit of current buildings, with almost no changes on infrastructures, but promoting them to a smart building level. Keywords: Energy efficiency, Green buildings, Intelligent supervision, Supervised predictive control

COVID19 pathogens are primarily transmitted via airborne respiratory droplets expelled from infected bio-sources. However, there is a lack of simplified accurate source models that can represent the airborne release to be utilized in the safe-social distancing measures and ventilation design of buildings. Although computational fluid dynamics (CFD) can provide accurate models of airborne disease transmissions, they are computationally expensive. Thus, this study proposes an innovative framework that benefits from a series of relatively accurate CFD simulations to first generate a dataset of respiratory events and then to develop a simplified source model. The dataset has been generated based on key clinical parameters (i.e., the velocity of droplet release) and environmental factors (i.e., room temperature and relative humidity) in the droplet release modes. An Eulerian CFD model is first validated against experimental data and then interlinked with a Lagrangian CFD model to simulate trajectory and evaporation of numerous droplets in various sizes (0.1 μm–700 μm). A risk assessment model previously developed by the authors is then applied to the simulation cases to identify the horizontal and vertical spread lengths (risk cloud) of viruses in each case within an exposure time. Eventually, an artificial neural network-based model is fitted to the spread lengths to develop the simplified predictive source model. The results identify three main regimes of risk clouds, which can be fairly predicted by the ANN model.

In this experimental-numerical study, effects of transverse magnetic field of parallel magnet bars perpendicular to the fluid flow direction and partially filled porous media are investigated. Moreover, constant heat flux is applied on the outer surface of a circular straight horizontal pipe and concentric porous media is embedded inside it. Magnet bars are located right at the entrance of pipe and a thick layer of insulation is wrapped the pipe to prevent heat loss. In addition, a 3D numerical simulation is performed using CFD techniques to capture the influence of these two factors on the thermohydrodynamic behavior of ferrofluid flow. Hybrid scheme of finite volume method and SIMPLE algorithm are employed to discretize and solve governing equations as well as TDMA for solving the linear algebraic matrix equation. Mineral oil is used as a base fluid and ferrofluid with three different volume fractions 0.5, 1 and 2% are prepared for the experiment. Finally prepared experimental setup configuration in this investigation leads to this conclusion that in comparison with magnetic field, although porous media induce more unfavorable pressure loss, it will bring more heat transfer enhancement as well.

Urban and rural areas are the cradles of human development and civilization as all practical progress and feasible products have emerged from these places. Having a clear understanding of the sustainability of these areas, especially the progress of research in this field, is highly important. This study undertakes a comprehensive scientometric analysis to visualize and quantitatively measure the outcome of the scientific enterprise to construct sustainable urban and rural areas. The scientific productivity of recorded publications, their impacts, and their importance were systematically measured in diverse aspects by virtue of ten distinctive techniques. A critical assessment of the respected criteria for sustainable urban and rural areas is presented in order to further clarify its boundaries with other related topics, as well as providing a clear benchmark for future studies. After screening the search results between 1900 and 2018 on the Web of Science database, 7397 publications explicitly related to sustainable urban and rural areas were extracted and analyzed by the CiteSpace software via the relevant bibliometric indicators. The results of this study shed light on the trends and patterns, consisting of kernel research areas, countries, journals, institutions, and how these entities have been concatenated, inside the bibliographic records around sustainable urban and rural areas. The findings facilitate in identifying the barriers and weakness in the current sustainable urban and rural areas research, and consequently help in identifying auspicious directions for prospective investigations.

Limited reserves of fossil fuels, rising environmental concerns, and a remarkable increase in electricity demand have led to the necessity of harnessing solar energy on a large scale. For this purpose, there has been a noticeable stimulation into photovoltaic power plants (PVPPs) over the last three decades, but the land requirement for PVPPs is still a handicap in many countries since valuable lands are considered for other purposes such as agriculture and livestock. For effective conservation of valuable lands and water resources, PVPPs are preferred to be installed on various water bodies such as oceans, seas, lagoons, lakes, rivers, dams, canals, wastewater treatment plants, irrigation ponds, fish farms, wineries, reservoirs, etc. PV systems on water bodies are called floating PVPPs, and they have outstanding advantages compared with land-based PVPPs including better energy generation owing to passive cooling effects, higher system efficiency and reliability, and lower dirt and dust accumulation on PV modules thus lower operating costs. There are also some significant environmental features provided by floating PVs. Shading effects due to PV coverage reduce water losses arising from evaporation. Moreover, algae growth is limited because of mitigated solar radiation, which yields better water quality. This review presents more insight on floating PVPPs in terms of several aspects such as electricity generation, system efficiency, reliability and sustainability, experimental applications and facilities in operation, water and carbon saving as well as challenges.

Publisher Copyright: © 2022 Elsevier Ltd Pathogen droplets released from respiratory events are the primary means of dispersion and transmission of the recent pandemic of COVID-19. Computational fluid dynamics (CFD) has been widely employed as a fast, reliable, and inexpensive technique to support decision-making and to envisage mitigatory protocols. Nonetheless, the airborne pathogen droplet CFD modeling encounters limitations due to the oversimplification of involved physics and the intensive computational demand. Moreover, uncertainties in the collected clinical data required to simulate airborne and aerosol transport such as droplets’ initial velocities, tempo-spatial profiles, release angle, and size distributions are broadly reported in the literature. There is a noticeable inconsistency around these collected data amongst many reported studies. This study aims to review the capabilities and limitations associated with CFD modeling. Setting the CFD models needs experimental data of respiratory flows such as velocity, particle size, and number distribution. Therefore, this paper briefly reviews the experimental techniques used to measure the characteristics of airborne pathogen droplet transmissions together with their limitations and reported uncertainties. The relevant clinical data related to pathogen transmission needed for postprocessing of CFD data and translating them to safety measures are also reviewed. Eventually, the uncertainty and inconsistency of the existing clinical data available for airborne pathogen CFD analysis are scurtinized to pave a pathway toward future studies ensuing these identified gaps and limitations.

We present a characterization of power penalty using p-i-n (PIN) and avalanche photodiode (APD) receivers for different extinction ratios (ER) of the transmitted signal. A simple approach based on experimental fitting is presented to describe the power penalty. The model is in a good agreement with the experiment, predicting both PIN and APD results accurately, even considering that the characterized devices may vary considerably in their intrinsic parameters. The fitting parameter from the proposed model was extracted using a mean squared error (MSE) based fitting function. Theoretical curves were obtained by fitting the numerical results to the experimental data for MSE=10−3.

In this study, steady state laminar ferroconvection through circular horizontal tube partially filled with porous media under constant heat flux is experimentally investigated. Transverse magnetic fields were applied on ferrofluid flow by two fixed parallel magnet bar positioned on a certain distance from beginning of the test section. The results show promising notable enhancement in heat transfer as a consequence of partially filled porous media and magnetic field, up to 2.2 and 1.4 fold enhancement were observed in heat transfer coefficient respectively. It was found that presence of both porous media and magnetic field simultaneously can highly improve heat transfer up to 2.4 fold. Porous media of course plays a major role in this configuration. Virtually, application of Magnetic field and porous media also insert higher pressure loss along the pipe which again porous media contribution is higher that magnetic field.

In this study, a scientometric comprehensive analysis has been executed in order to explore the scientific situation of research efforts performed previously with regard underground CO2 sequestration and encapsulation. To this end, a total of 1280 bibliographic records from the Web of Science (WoS) database were extracted and analysed to report the analysis of scientific state of the authors, journals, countries, and categories. Eventually, geospatial maps of the progress in this field are created and presented. As per the results obtained, efforts on this subject have been initiated significantly since 1990s. Scientific articles and proceeding papers share nearly 63% and 31% of the documents published. The results indicate that USA and China are the most contributing countries. Among the active journals, international journal of greenhouse gas control impact is the most active journal. It may be concluded that no highly active research group has yet been emerged. Hence, more supports and scientific efforts are needed to promote carbon dioxide capture and storage technologies.

In the current global situation, the release of large amounts of potential effluents into the environment is considered as one of the most important and challenging issues. Innovations in the treatment methods to deal with this problem are among the research priorities within the scientific communities. Even though innumerable methods including physicochemical and biological have been used, yet no proper sustainability of the methods have been introduced. Membrane bioreactors (MBRs) have gained world-wide attention in recent years, but still there is no report in the literature to map the global research on this subject. The present manuscript describes a scientometric study on the global trend on the application of MBRs during the period 1991–2018 by employing variables such as: (1) distribution of documents over the adopted duration, (2) type of documents in this area, (3) rate of contribution among the different countries, (4) rate of cooperation among the authors, (5) frequency of the keywords co-occurring, (6) cited authors, (7) cited journals, (8) the frequency of categories appeared and (9) the cited documents. A total of 2452 bibliographic records from the Web of Science database were retrieved and analysed to generate results, thereby to create geospatial maps for a better understanding. The findings reveal an increase in the number of papers published in the world, especially China and USA being the top. The existing studies in MBRs research focus mainly on subject categories of the performance and fouling as the main criteria of the sustainable application of MBRs. This study therefore, provides an extensive understanding about the trends and research patterns of MBRs efforts worldwide.

This study is dedicated to the thermal analysis and thermo-hydrodynamic simulation of an air-to-air plate heat exchanger in order to solve its routine problem in industry. The compact type of cross-flow plate heat exchanger, in which corrugated plates pile up tightly and delicately brazed to each other, has been used in many situations and has many applications from food industries to petroleum and military. Routinely, after a certain lifespan, the brazed joints are detached and cause a mixture of hot and cold fluids as well as highly reduction of heat exchanger performance. This problem leads to increase the system maintenance significantly. Apart from the imposed cost and time for its maintenance, which is indeed a crucial problem? Finally, to have a better understanding, a threedimensional numerical investigation on thermo-hydrodynamic analysis of conjugate heat transfer was performed using computational fluid dynamics techniques. Forced convection heat transfer for fluid flow and conduction through solid material were considered as well. For simulation of steady state flow of Newtonian fluid, the governing equation was discredited by finite volume method and solved by the semi-implicit method for the pressure-linked equation. It was also found that both temperature and temperature gradient play an important role in this problem.

This study steps into the roadmap of agenda 2030 to mitigate the human footprint on an environment with the aim of management of energy consumption in residential/commercial buildings. In order to materialize this concept, a new generation of adaptable systems of intelligent supervisory predictive control (ISPC) is introduced and implemented in which energy consumption tends to be minimized without sacrificing occupants thermal comfort. The methodology of ISPC includes building thermal simulation and multi-objective optimization algorithm that interact with conventional machine-level controllers of HVAC systems, to define optimized setpoints considering current and forecasted operation conditions. The development of a reliable surrogate model, based on robust machine learning techniques, is a key feature to confer greenness to a building in order to promote sustainability in the built environment and finally to have a smart green building. It is showed that the proposed ISPC is capable of delivering a robust, energy- and cost-effective decision while being independent of the HVAC system. The implemented energy management, as a non-destructive retrofitting procedure, can be applied to both new and existing buildings and with any level of HVAC technology.

A countless amount of energy has been wasted in all kinds of expansion valves (EV) in industries. In fact, EVs, including regulators, throttling valves, capillary tubes, etc., have been used to intentionally reduce the potential of carrier fluid. City gate stations (CGS) have been recognized as one of the important points with high potential for energy harvesting due to its function for regulating natural gas (NG) pressure by EV. In this study, Tesla turbine (TT) is introduced as a new candidate for substitution of EV, particularly those that have been employed in CGS on high-pressure NG pipelines, as well as those applications in which high-potential fluid must be reduced to a low-potential state to form a complete thermodynamic cycle or to be used at end-user equipment. Although harvesting energy is one of the hottest fields of science and engineering, there are few traces of research on using a TT as an alternative for EVs, even for the industries possessing high-pressure lines. This numerical experiment intends to show the capability of TT as a robust candidate for substituting regulation valves through investigating thermohydrodynamic characteristics of the turbulent high-pressure compressible NG flow through a TT under different operation conditions. This study, with the objective of managing the exploitation of resources, can be considered as one step forward toward reinforcing economic and environmental pillars of sustainable development. It is also found that the generated power by TT can support the 285 7W LED simultaneously, or it is equivalent to 84.4 m2 area of the solar panel (150 W, 15.42% efficiency) for the climate condition of Toronto, Canada.

The forced convection heat transfer of ferrofluid steady state laminar flow through a circular axisymmetric horizontal pipe under different magnetic field is the focus of this study. The pipe is under constant heat flux while different linear axial magnetic fields were applied on the ferrofluid with equal magnetic energy. In this scenario, viscosity of ferrofluid is temperature dependent, to capture ferrofluid real behavior a nonlinear Langevin equation was considered for equilibrium magnetization. For this purpose, the set of nonlinear governing PDEs was solved using proper CFD techniques: the finite volume method and SIMPLE algorithm were used to discretize and numerically solve the governing equation in order to obtain thermohydrodynamic flow characteristics. The numerical results show a promising enhancement of up to 135.7% in heat transfer as a consequence of the application of magnetic field. The magnetic field also increases pressure loss of up to 77% along the pipe; but effectiveness (favorable to unfavorable effect ratio) of the magnetic field as a performance index economically justifies its application such that higher magnetic field intensity causes higher effectiveness of up to 1.364.

This study includes experimental and three-dimensional numerical analysis of conjugate steady-state laminar forced ferroconvection of Newtonian incompressible ferrofluid through a horizontal circular pipe under constant heat flux and in presence of transverse magnetic field. The magnetic field was applied by two fixed parallel magnet bars at the beginning of the tube. To validate the thermohydrodynamic characteristics obtained by numerical results, appropriate experimental setup with accurate instrumentations was conducted. Based on presence and absence of porous media and solid rod inside of pipe, six conditions were compared for quantifying the heat transfer enhancement and effectiveness. Governing equations were discretized by finite volume method (FVM) and solved using the semi-implicit method for pressure linked equations (SIMPLE) algorithm and computational fluid dynamic (CFD) techniques. It was found that magnetic field, porous media, and solid rod increase heat transfer and pressure loss in the pipe such that solid rod has the best effect on heat transfer and worst effect on effectiveness.