The effects of neutron radiation on nickel-based alloys

The effects of neutron radiation on nickel-based alloys in thermal reactors are defying predictions that were made based upon accelerated testing in fast reactors. As nickel-based alloy components face significant doses in aging thermal reactors and their role in Gen-IV reactor designs becomes prominent, the literature on the effects of radiation on such alloys must be reviewed to enable better structural integrity assessments for relevant components and optimise alloys with respect to irradiation embrittlement resistance. This paper reviews the available data on the effects of radiation, notably neutron radiation, on nickel-based alloys and discusses the possible mitigation strategies and design opportunities for radiation embrittlement-resistant alloys based on recent developments in alloy computational design.

This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.     

Survey on the P.V. Generator of Castellina in Chianti (Italy)

The aim of this study was the definition of low-cost solutions to optimise and maintain a satisfactory cost balance in the medium-long term between the different sub-systems and components of P.V. power generators.

In particular, the long-term objective is to keep the cost of support structures below about 20% of the total system cost.

A unit of about 200 modules was investigated in the Chianti Region of Castellina and in this paper results will be presented on the following topics

-the feasibility study of the most appropriate solution of a low-cost, simple, light-weight (0.3 kg/Wp), flexible and continuous array support structure (made of timber and steel wires).

-The study of the soil and of the site including site preparation by simple machines.

-The design of the solution retained valid after the imposed limitations for the plant approval.

-The construction and assembling of the entire P.V. plant.

-The measurements' campaigns carried out on the main structural components and the discussion of these results compared with design assumptions.

-The extrapolation of the real costs to larger P.V. units.

-The conclusive remarks on the experience acquired during the implementation of the project, its realization, its testing and operation over more than 18 months of life-time.     

Prediction of asphaltene deposition parameters in porous media using experimental data during miscible gas injection

The study of asphaltene deposition under actual field conditions is impossible. Therefore, many models have been derived based on experimental data. All models have some matching parameters, which are estimated along with numerical solving or simulation to match experimental and simulation data, so it is possible that these were estimated as required (tuning factor).

In this study, two miscible CO₂ injection dynamic tests in porous media were performed. In these tests, CO₂ and live oil were injected into the core simultaneously. The CO₂ concentration was more than the onset concentration for asphaltene precipitation.

The main objective of this work was to determine the deposition coefficients from the experimental data, so these were predicted by using basic equations using the material balance. Also, by mathematical methods, the relation between these parameters was determined.

Results from this work imply that the deposition parameters can be estimated from the experimental data and these parameters are not constant during modeling and simulation.     

Identification of UA in Thermal Storage Devices-Two Methods

Two methods are described for identifying the key overall fluid to storage material heat transfer product, UA, and the degree of stratification, NT, for use in the analysis of storage test data

The first method, called the generalised model approach, permits a wide range of non-linearities as well as arbitrary test initial and boundary conditions to be accommodated

The second method, called the simplified graphical method, demands high quality step response data but is very easy to use

Three examples taken from recent work in the SSTG programme are examined and these include a fully mixed response, a fully stratified response and a partially stratified response. The graphical method is shown to give a good estimate of the UA value for each case, even for the difficult case of partial stratification.     

The Adrano Project

The aim of the Adrano Photovoltaic Project is to permit direct on site testing and comparison of different P.V. generators.

The Project includes the design, fabrication, installation and testing of four 2.5-3 kW blocks, representing two different types of fixed flat-plate modules and one type of sun-tracking modules.

Each block consists of the array (P.V. modules, sun-tracker devices, support structures, wiring connectors, protection devices), the power conditioning system (MPPT-inverter) and the suitable instrumentation. Therefore each block is a fully independent P.V. system able to supply electric energy to a 380 V, 50 Hz three-phase line.

Furthermore, two experimental 200 W_p systems with GaAs cells and amorphous silicon cells are installed in the same area for the testing of these particular technologies.     

Residual Least-Squares Error Estimate for Unstructured h-Adaptive Meshes

An a posteriori error estimate suitable for finite-volume adaptive computations is presented. The error estimate combines the least-squares method regressions with the residual computation, which provides information from the grid quality and the governing equations for a better local adaptation of the unstructured grid.

The decision algorithm uses the information provided by the error estimate and does not require problem-dependent constants; it also uses a grid interface correction step to provide a smoother and a high-quality adaptive grid.

The proposed error estimate and the adaptive refinement algorithm are verified against analytic solution for different two-dimensional problems. In addition, calculations of three-dimensional laminar flows with different types of unstructured grids have demonstrated the applicability of the adaptive method.     

Combination of Flat-plate Solar Collectors of Different Performance

The collector most frequently used in solar plants is of the flat-plate single cover type; however its field of use is limited owing to the low temperatures reached with this type of installation. Collectors with a greater number of covers produce higher temperatures, thus broadening their field of use

The analytical model presented in this paper makes it possible to obtain the optimum combination of differently performing flat-plate collectors ( collectors with different numbers of glass covers), in order to maximize the economic benefit of liquid heating solar plants at different temperatures and under different operating conditions

The results obtained justify the assertion that combined flat-plate collector systems present better techno-economic performance at high temperatures than single systems with single cover collectors.     

The Vulcano Project

The chief aim of the Vulcano Project is to evaluate the technical and financial feasibility of supplying electric power to small, remote village out of reach of utility grids by using a photovoltaic solar energy system.

The experiment consists of the design, construction, and operation on the Island of Vulcano ( Sicily), of a plant for the production of electric power by means of a stand-alone photovoltaic system.

Alternatively, the plant can supply energy in parallel to the existing diesel power station, as a “ fuel-saver” in order to investigate the economics of this type of operation.     

Lessons from the Acceptance Tests on the CEC Photovoltaic Pilot Plants

Official acceptance tests, involving performance measurement, visual inspection and functioning checks, have been carried out on all fifteen of the photovoltaic pilot plants in the European Commission' second 4-year programme of solar energy R&D. Equipment and procedures developed for on-site performance measurement have been successfully applied throughout the year - even in an English November.

All installations were found to be aesthetically pleasing, in accordance with CEC guidelines, but there is scope for reducing the costs of site preparation, support structures and array installation.

Some of the modules were of high quality but others had low efficiency, poor process control and unsatisfactory arrangements for mounting and interconnection -faults which should be remedied in today's highly competitive market. Measurement discrepancies could be reduced if all manufacturers adhered strictly to the current European standard, CEC Specification 101, Issue 2. A single international standard for reference cell calibration should be an aim for the future.

Varistors used for lightning protection should be carefully chosen to withstand the highest operational voltages over many years without the type of progressive degradation, which, as has been seen, may lead to catastrophic failure.     

Case study: Comparison of enhanced heavy-oil recovery by CGI,WAG, and GAGD

Continuous gas injection (CGI) in the conventional horizontal flooding patterns leads to severe gravity segregation and poor reservoir contact (sweep) volumes. To improve the sweep efficiency, the Water-Alternating-Gas (WAG) process has been widely practiced in the industry. However, the WAG process has not measured up to expectations, as evidenced by the low recoveries observed in several field cases.

The Gas-Assisted Gravity Drainage (GAGD) process is designed and practiced based on gravity drainage idea and uses the advantage of density difference between injected gas and reservoir oil to overcome the drawbacks of the WAG process.

In this study, a comparison of enhanced heavy-oil recovery by three methods (CGI, WAG, and GAGD) is conducted by a commercial numerical simulator in a sector model of an Iranian offshore field. For this purpose, different production scenarios are designed. Moreover, the effect of several parameters such as injection fluid (CO₂, hydrocarbon gas), in situ oil viscosity (heavy or extremely heavy oil), rate and volume of injection, and also three different WAG ratios are studied.

The results show that the GAGD method is not suitable for this field as the thickness of pay zone is low for vertical sweep efficiency and causes early breakthrough of injected gas. Also, CGI leads to lower recoveries compared to the WAG process, due to its unfavorable mobility ratio. Injection of CO₂ instead of hydrocarbon gas results in higher sweep efficiency because of its viscosity reduction and swelling effects. In case of extremely heavy-oil recovery, with decreasing well spacing, the oil recovery factor increases as the drainage radius of wells reduces substantially due to high-viscosity oil.     

Combustion characteristics of solid waste biomass,oil shale,and coal

In this study, a developed two-dimensional mathematical model was used to represent the physical model of the combustion process of olive cake and date seed, and solve the governing equations using finite-volume method. The simulation was performed using ANSYS/Fluent software in order to estimate maximum temperature, heating values and pollutants concentrations. The obtained results were compared with experimental results, and corresponding values of oil shale and coal. The experimental work of direct burning of olive cake and date seeds was performed using an existing circulated fluidized bed (CFB) unit.

It was found that the adiabatic flame temperatures were 1380 K and 839 K for olive cake and date seed, and 2260 K and 1080 K for coal and oil shale, respectively. The experimental results showed that the maximum temperatures were 1126 K and 723 K for olive cake and date seed, respectively. The lower heating values were 19,500 kJ/kg and 16,400 kJ/kg for olive cake and date seed, and 29,000 kJ/kg and 7000 kJ/kg for coal and oil shale, respectively.

Thus, biomass such as date seed and olive cake may be used as an alternative fuel in electrical power plants in olive- or date-producing countries, which may save 40% of fuel cost.     

Hydrophilic and hydrophobic materials and their applications

Wettability of a material’s surface plays a significant role in how fluids interact with such surfaces. Wetting behavior is universal but can vary depending on the chemical nature of the solid and liquid phases. Plants and animals adapt to their environment by having evolved special properties. These properties are such as hydrophilic and hydrophobic. Hydrophilic surface has a strong affinity to water and spreading of water on such surface is preferred. The degree of hydrophilicity of the substance can be measured by measuring the contact angle between the liquid and solid phases. Hydrophobic materials are known as non-polar materials with a low affinity to water, which makes them water repelling. A contact angle of less than 90° indicates hydrophilic interaction where as an angle greater than 90° indicates a hydrophobic interaction. More recently, superwetting such as superhydrophilicity has been receiving an increased focus in the literature due to its potential significance. Superhydrophilic surface has a contact angle of less than 5°.

The fabrication of hydrophilic materials can be carried out in two main ways: depositing molecules on surfaces or modification of surface chemistry. Both methods have been successful historically in achieving their intended purposes. Hydrophobic and superhydrophobic materials can be produced with many fabrication methods such as layer-by-layer assembly, laser process, the solution-immersion method, sol-gen techniques, chemical etching, and Hummer’s method.

The applications of such an important property are significant. For example, hydrophilic surfaces can be used in anti-fogging applications, biomedical, filtration, heat pipes, and many others. Hydrophobic and superhydrophobic materials have been successfully applied in many sectors, such as: (I) the removal of petroleum from aqueous solutions, (II) applied to plastic, ceramics, and mesh to contribute to the oil removal from aqueous solutions, (III) hydrophobic layers have a strong self-cleaning effect on plastics, heat pipes, metals, textiles, glass, paints, and electronics, (IV) hydrophobic layers improve the anti-freezing behavior of heat pipes which prevents unwanted build-up and (V) they function as a water and dust protecting coat on electronics.

The presence of this property is historic but there is still a huge potential for development for its applications in many sectors such as water treatment, heat transfer applications, biomedical devices, and many more.     

Parabolic trough collector with rhombus tube absorber for higher concentration ratio

In the present study, the concentration ratio of the parabolic trough collector using rhombus tube absorber has been estimated. An analytical technique has been developed to determine the optimum size of the rhombus tube absorber for given trough dimensions. The optimum size of the rhombus tube absorber is 13.8% smaller than the circular tube absorber for the LS3 trough with no change in intercept factor. The maximum improvement in the concentration ratio is found to be 31.5% for the troughs with rim angle 90° in comparison to circular tube absorber. Results also indicate that rhombus tube absorber can be employed for a range of rim angle 75 to 90 degree.

Abbreviations: CR: concentration ratio; CSP: concentrated solar power; MCRT: Monte Carlo ray tracing; PTC: parabolic trough collector     

Estimating Solar Irradiance on Inclined Surfaces: A Review and Assessment of Methodologies

A variety of numerical models for calculating the solar irradiance for an inclined surface are described and evaluated using data for Vancouver, B.C., Canada. While all the hourly models have a common approach for calculating the direct component of the solar irradiance there is a variety of methods for calculating the diffuse irradiance based on the portion of the sky hemisphere within the field of view of the surface. A less significant distinction between the models is in the methods used to calculate the amount of radiation received as a result of reflection from adjacent surfaces.

The paper demonstrates that the principal features of the anisotropic distribution of sky radiance must be included in the numerical computations since the use of the unrealistic isotropic model leads to significant short and long term errors. Inclusion of directional reflectance in the slope irradiance calculations will lead to increased accuracy for the estimated values, with greatest improvement being achieved in the winter months due to a zenith angle dependency on the significance of the directional reflectance.

Errors in estimating the slope irradiance with an anisotropic model are shown to compare favourably with the errors associated with a direct measurement of the solar irradiance.     

Two-dimensional numerical modeling of combustion of Jordanian oil shale

A two-dimensional (2-D) modeling of the burning process of Jordanian oil shale in a circulating fluidized bed (CFB) burner was done in this study. The governing equations of continuity, momentum, energy, mass diffusion, and chemical combustion reactions kinetics were solved numerically using the finite volume method. The numerical solution was carried out using a high-resolution 2-D mesh to account for the solid and gaseous phases, k-ε turbulence, non-premixed combustion, and reacting CFD model with the same dimensions and materials of the experimental combustion burner used in this work. The temperature distribution and evolution of species were also computed.

Proximate and ultimate analyses were also performed to evaluate the air–fuel ratio and ash content. The required thermophysical properties, such as heating value, density, and porosity were obtained experimentally, while the activation energy was obtained from published literature.

It was found that the temperature contours of the combustion process showed that the adiabatic flame temperature was 1080 K in a vertical burner, while the obtained experimental results of maximum temperature at various locations of the burner in actual, non-adiabatic, non-stoichiometric combustion reached 950 K, showing good agreement with the model.     

The effect of renewable energy and urbanization on CO2 emissions: A panel data

Europe has experienced fast-paced urbanization development over the past three decades. This paper empirically investigates the long-run equilibrium relationships and causal relationships among urbanization, renewable energy consumption, and CO₂ emissions, and this is important for EU countries’ future sustainable development. DOLS and FMOLS approaches are used for the period 1992–2014 .

Granger causality results show that there is a unidirectional relationship from CO₂ emissions to urbanization, and there is no causality between renewable energy consumption and CO₂ emissions. The results have important implications for EU policymakers on the path toward a sustainable society. Urbanization can have negative impacts on the natural environment with the net effect being hard in EU countries.     

Inhomogeneous flow model of natural convection,entropy generation,and heatlines visualization in wavy I-shaped enclosure with rectangular heater

The present investigation is on examination of the natural convection and entropy generation considering the heatlines visualization of nanofluid I-shaped enclosure with two corrugated walls considering inner rectangular heater of three different heights. The influence of Brownian motion along with thermophoresis had been implemented using Inhomogeneous two-phase model of nanofluid. The governing equations were solved numerically using COMSOL software. Influence of Rayleigh number $$, Buoyancy ratio number $$, Lewis number $$, heater length $$. The results indicate that the influence of Lewis number on heat transfer bettering is stronger at high Rayleigh number $$ while its impact is negligible at a lower value of Rayleigh number (conduction mode). In addition, the total entropy generation gets its highest value at Lewis number $$. Bejan number, fluid flow strength and heat rate increase as the rectangular heater height increases. Also, higher heat transfer augmentation is taken when the heater height is $$ while increasing the heater height to $$ leads to more total entropy generation. The impact of heater height on total entropy generation is highly affected by Rayleigh number as increasing the heater height from $$ into $$, total entropy generation increases by $$ at $$ while it increases by $$ at $$.     

An experimental investigation on the application potential of heterogeneous catalyzed Nahar biodiesel and its diesel blends as diesel engine fuels

From the inception of commercialization of biodiesel, feedstock scarcity is a major issue to be pondered upon in developing countries. In this study, an attempt has been made to use an abundantly available underutilized high oil content (67% of Nahar seed kernel) feedstock derived biodiesel in a compression ignition engine. The experimental investigation on diesel engine reveals slightly reduced brake thermal efficiency and excellent exhaust emissions up to 40% blending of Nahar biodiesel with conventional diesel fuel. At full load, compared to diesel fuel, the BTE dropped by 1.64% and 1.83%, whereas the BSFC increased by 5.07% and 6.76% for B30 and B40 blends, respectively. The tested emission parameters such as CO, HC, NOx, and smoke were decreased by 12.66%, 17.99%, 8.31%, and 10.61% for B30 and 4.87%, 12.76%, 7.98%, and 11.78% for B40, respectively, compared to diesel fuel.

Abbreviation: BD: Biodiesel; DF: Diesel fuel     

Modeling​ some of the operational parameters of MGS for lignite cleaning by full factorial design methodology

In this study, the effects of shake amplitude, frequency, drum speed, and solid ratio of multi-gravity separator on ash content (AC) and combustible recovery (CR) of clean lignite were investigated and modeled. Experiments were planned by full factorial design and analysis of variance analysis is used to determine whether there are any significant parameters.

As a result, mathematical models of AC and CR were derived as functions of studied parameters. At optimum conditions, the AC of clean lignite was reduced from about 75 to 50.81% with 58.71% CR. Additionally, the effect of drum speed was found to be higher than other parameters.     

Development of Integrated Capacitance Resistive Model for predicting waterflood performance: a study on formation damage

The Integrated Capacitance Resistive Model (ICRM), a linearized form of Capacitance Resistive Models (CRM), has been commonly used to match liquid production history and estimate interwell connectivity (IWC) in waterflooded reservoirs. Although this model fits cumulative production data accurately, it usually fails to estimate correct values of total production, where backward subtraction of cumulative production delivers highly overestimated or underestimated total production rates. To address this issue, a modified optimization approach is presented to minimize the error between both cumulative and total production data through two consecutive constrained objective functions. This paper validates the modified ICRM in homogeneous synthetic examples with vertical wells to show how the new approach can successfully characterize the waterflooded reservoirs. The model was also tested in damaged formations to detect its impact on the communication between wells. Finally, a correlation is proposed to explain the mathematical and physical relationship between formation damage (skin factor) and IWC of the damaged well.

Abbreviations BHP: bottom-hole pressure; CMG: computer modeling group Ltd.; COF: Consecutive objective function; CRM: capacitance-resistive model or capacitance-resistance model; CWI: cumulative water injection; ICRM: integrated capacitance-resistance model; IMEX: Implicit-explicit black oil simulator