Numerical investigation to examine two methods of passive control in urban street canyon using CFD: Comparison between crossing under building and solid barriers lbw

Different passive control methods are discussed in this paper with the purpose of improved the quality of the air and dispersed the pollution outside the urban canyon road. Numerical investigation model is used in this paper, to examine two methods of passive control within a crossing under building and Low Boundary Wall in center of road for reducing air pollution concentration using Reynolds-averaged Navier–Stokes  equations and the k-Epsilon turbulence model as close of the equation system. The results of this investigation show that a low boundary wall located at the central median of the street canyon creates a significant reduction in pedestrian exposure, relative to the same canyon with no wall. The magnitude of the exposure reduction was also found to vary according to the numbers of the crossing under building in the street canyon geometry. The values of the concentration normalized is  decreased in the critical region were located in the centerline of the street canyon.Keywords: Passive Methods, Barriers, Street Canyon, Pollutant  Dispersion, Numerical Simulation

Pretreatment techniques used in biogas production from grass

Grass is being considered as a potential feedstock for biogas production, due to its low water consumption compared to other crops, and the fact that it can be cultivated in non-arable lands, avoiding the direct competition with food crops. However, biogas production is limited by the characteristics of the feedstock; in particular its complex lignocellulosic structure. Hence, different pretreatment methods are being investigated for grass structure disruption before undergoing the anaerobic digestion process. The aim of this paper is to review current knowledge on pretreatment techniques used for grassland biomass. Pretreatment techniques were categorized into mechanical, microwave, thermal, chemical and biological groups. The effect of the application of each studied methods on the biogas yield and on the energy balance is discussed. A further comparison between the covered techniques was revealed

Advances in stationary and portable fuel cell applications

The reliance on fossil fuels is one of the most challenging problems that need to be dealt with vigorously in recent times. This is because using them is not sustainable and leads to serious environmental issues, such as: air pollution and global warming. This condition affects economic security and development. An alternative to fossil fuel is highly possible which will be more environmentally friendly, sustainable and efficient as well. Among all the different technologies associated with renewable energy, fuel cell technologies represent one of the most promising technological advancement to curb the situation. In this paper, an overview of the technology and its advantages and disadvantages compared with competitive technologies was revealed. The application of different fuel cell types in the stationary and portable sectors was covered. Furthermore, recent challenges and promising developments of current fuel cell technologies in different studied applications were reviewed. Some possible solutions to the challenges were named in this paper for both the portable and stationary fuel cell applications. The paper further seeks to expose the world to the current progress made in the fuel cell industry up to date and possible areas that needs intensified research and modifications to make the fuel cell industry more vibrant and buoyant

Prediction of the gas emission from porous media with the concern of energy and environment

Measuring soil carbon dioxide efflux is a challenging task even when it is performed using respiration chambers. While gas samples are taken, measurement deviations become more evident according to the used chamber design especially when external disturbances occur. This paper studies the carbon dioxide concentration profiles within the top soil layers, and investigates the controlling factors affecting the process. The considered factors are diffusion, temperature and viscosity. The efflux equation is discussed and then it is linked with the soils geotechnical parameters, while a relationship between the Reynolds number within the soil and efflux is found. Emphasis on the importance of the external geometrical design considerations is shown through studying external boundary layer effects due to the chamber outer shell shape and how it interacts with blowing winds. Chamber stability on site of deployment is also of a significant importance considering external blowing winds. Internal geometrical considerations are linked with the flow turbulence within the dynamic chambers. It is highly recommended that respiration chamber designers need to work in parallel with a multidisciplinary team in order to make a chamber design that ensures the least disturbance to occur at the location of study

Renewable energy scenario and environmental aspects of soil emission measurements

European Commission has set clear targets for 2020 regarding energy and environment policy; these targets include 20% cut in greenhouse gas emissions against the 1990 levels. It is believed that adopted strategy has encouraged the renewable energy applications during the last two decades. Moreover, measurement deviations of carbon dioxide flux occurring in respiration chambers has been seen of a great importance to explain the biochemical parameters affecting the climate change issue. This is attributed on many occasions to chamber design constraints and the way they are coupled with the studied site location. This is illustrated by external disturbances whereby when they happen while gas measurements are taken measurement deviations become more evident. This paper surveys the different soil physical, biological and geotechnical parameters and links them to meteorological ones. Consequently it explores their direct and indirect effects to the produced soil efflux. Furthermore this paper proposes several soil temperature models according to the studied case constraints to see what affects soil efflux production. Moreover a clear understanding of what affects the measurement process was achieved through surveying all the internal and external pressure parameters and how they influence the chamber in relation to time. The conclusion is that respiration chamber designers need to preserve chamber internal temperature and pressure to be equal to the outer atmosphere for the case of stabile external conditions. For the case of unstable external conditions design counter measures are incorporated. Furthermore the appropriate gas sensor needs to be selected professionally with emphasis on the importance of installation location inside the chamber. Likewise soil bacterial type and soil temperature also has an influence on efflux production

Developments in fuel cell technologies in the transport sector

The demand for clean power source which can be used to run the various types of vehicles on the road is increasing on a daily basis due to the fact that high emissions released from internal combustion engine play a significant role in air pollution and climate change. Fuel cell devices, particularly Proton Exchange Membrane (PEM) type, are strong candidates to replace the internal combustion engines in the transport industry. The PEMFC technology still has many challenges including high cost, low durability and hydrogen storage problems which limit the wide-world commercialization of this technology. In this paper, the fuel cell cost, durability and performances challenges which are associated with using of fuel cell technology for transport applications are detailed and reviewed. Recent developments that deal with the proposed challenges are reported. Furthermore, problems of hydrogen infrastructure and hydrogen storage in the fuel cell vehicle are discussed

A numerical and experimental study of a new design of closed dynamic respiration chamber

Carbon dioxide soil efflux modelling in closed dynamic respiration chambers is a challenging task. This is attributed on many occasions to the very small concentrations of carbon dioxide being transported between soil and the atmosphere. This paper describes a portable device which was made exclusively to accurately measure carbon dioxide efflux from soil locations. The blowing fan creates a forced convective flow to occur in the chamber making the K-Epsilon turbulence model a necessity to model the occurring flow in the respiration chamber gas domain. Furthermore the Darcy model is applied on the porous domain to model the flow pattern within the soil. The measurement process was achieved through measuring carbon dioxide concentration, temperature and relative humidity inside the chamber in relation to time. Simulation and experimental data is obtained using ANSYS and MATLAB. A significant agreement between the experimental and numerical results was achieved

A new pH phenomenon to predict polarity reversal in lead-acid cells

This paper discusses new experimental work investigating the change in pH of the electrolyte of individual cells in Lead-Acid batteries during discharge with a view to predicting cell polarity reversal and thereby pre-empting potentially catastrophic failure in batteries. The discharge tests were carried out on batteries which were classified as ‘new’ and ‘aged’ as a means of indicating their state of health. A new pH phenomenon has been recorded for the first time in this paper as evidenced by experimental results including measurement of half-cell potentials. The trends observed during the discharge tests could be used as additional means of indicating impending cell reversal in series connected lead-acid cells

The Immersive Placement Experience: Sink Or Swim?

To excel in their respective engineering fields, engineering students need to be equipped with a combination of technical and interpersonal skills. Central to excellent interpersonal skills is good communication. The aim of the study is to evaluate how well-prepared mechanical and design engineering students felt entering into their industrial placements, using a UK university as a pilot case study. For the study interviews were carried out with final year students who had previously completed an industrial placement year, focussing on communication, workplace diversity, technical working methods and university teaching styles. Reponses were anonymised, coded and analysed using quantitative and qualitative methods. Nine engineering students were interviewed regarding their placement experience and were asked to rate how well they thought their engineering programmes helped in developing these skills. Two key findings were: 1) students on average spent 60 % or more of their placement work using their communication skills and 2) students felt more could be done to prepare them for individual presentations and individual projects before placement. On average the students felt marginally more prepared with the interpersonal skills element compared to the technical skills element. The survey also highlighted that the students' understanding of what falls under the umbrella of workplace diversity was narrow, and they did not classify skill differences as a component of diversity. The student's honest feedback allowed a collation of proposed recommendations for both the mechanical and design engineering courses