Transient-state Model Research Articles

Acute aerobic exercise and creative thinking: comparison of transient hypofrontality state and strength model of self-controls’ theoretical predictions

Creativity is a high-level cognitive activity that can" be affected by acute aerobic exercise. This paper aims to determine how acute aerobic exercise intensities may influence aspects of divergent and convergent creative thinking. In this regard, to give an insight into the results, the predictions of the transient hypofrontality thesis and the strength model of self-control have been taken into consideration. Ninety-three healthy male college students (age = 21.18 ±1.73 years) were randomly assigned to anaerobic threshold intensity (%85 HRmax, n = 31), low intensity (%60 HRmax, n = 31), and control (n = 31) groups Participants performed divergent (Alternate Uses Task) and convergent (Raven's Advanced Progressive Matrices Test) creative thinking tasks before, during, and after cessation of two anaerobic thresholds and low intensities and control conditions. For the divergent creative thinking, flexibility and fluency performances during and after cessation of exercise in anaerobic threshold and low-intensity groups were improved in comparison to the control group.These results were consistent with the transient hypofrontality thesis and inconsistent with the strength model of self-control pre-dictions. In contrast, the performance of convergent creative thinking was relatively stable during and after cessation of exercise in anaerobic threshold and low-intensity groups which was inconsistent with both the transient hypofrontality thesis and the strength model of self-control predictions. The findings suggest that theoretical predictions of transient hypofrontality thesis are more adaptable with literature than the strength model of self-control to consider the exercise-creative processes relationship and further study of the issue would be of interest. Key words: Cognition, Convergent, Creativity, Divergent, Self-depletion, Physical Activity

NITIRSOIL: A model that balances complexity with prediction uncertainty for improving nitrogen fertilization in agriculture

Mismanagement of the nitrogen (N) fertilization in agriculture leads to low N use efficiency (NUE) and therefore pollution of waters and atmosphere due to NO3− leaching, and N2O and NH3 emissions. The use of N simulation models of the soil-plant system can help improve the N fertilizer management increasing NUE and decreasing N pollution issues. However, many N simulation models lack balance between complexity and uncertainty with the result that they are not applied in actual practice. The NITIRSOIL is a one-dimensional transient-state model with a monthly time step that aims at addressing this lack in the estimation of, mainly, dry matter yield (DMY), crop N uptake (Nupt), soil mineral N (Nmin), and NO3− leaching in agricultural fields. According to its global sensitivity analysis for horticulture, the NITIRSOIL simulations of the aforementioned outputs mostly depend on the critical N dilution curve, harvest index, dry matter fraction, potential fresh yield and nitrification coefficients. According to its validation for 35 nitrogen fertilization trials with 11 vegetables under semi-arid Mediterranean climate in Eastern Spain, the NITIRSOIL presents indices of agreement between 0.87 and 0.97 for the prediction of total dry matter, DMY, Nupt, NO3− leaching and soil Nmin at crop season end. Therefore, the NITIRSOIL model can be used in actual practice to improve the sustainability of the N management in, particularly horticulture, due to the balance it features between complexity and prediction uncertainty. For this aim, the NITRISOIL can be used either on its own, or in combination with “Nmin” on-site N fertilization recommendation methods, or even could be implemented as the calculation core of decision support systems.

Energy Bus-Based Matrix Modeling and Optimal Scheduling for Integrated Energy Systems

Integrated energy systems (IESs) can easily accommodate renewable energy resources (RESs) and improve the utilization efficiency of fossil energy by integrating various energy production, conversion, and storage technologies. However, the coupled multi-energy flows and the uncertainty of RESs bring challenges regarding optimal scheduling. Therefore, this study proposes an energy bus-based matrix-modeling method and a coordinated scheduling strategy for the IES. The matrix-modeling method can be used to formulate the steady- and transient-state balances of the multi-energy flows, and the transient model can clearly express the multi-time-scale characteristics of the different energy flows. The model parameters are fitted with data from experiments and the literature. To address the inherent randomness of the RESs and loads, a coordinated scheduling strategy is designed that contains two components: day-ahead optimization and rolling optimization. Day-ahead optimization uses the system steady-state model and multiple scenarios from the RES and load forecast data to minimize the operation cost while rolling optimization is based on the system’s transient-state model and aims to achieve the optimal real-time scheduling of the energy flows. Finally, a case study is conducted to verify the advantages and effectiveness of the proposed model and optimization method. The results show that stochastic optimization reduces the total daily cost by 1.48% compared to deterministic optimization when considering the prediction errors associated with the RESs and loads, highlighting the stronger adaptability of stochastic optimization to prediction errors. Moreover, rolling optimization based on the system’s transient-state model can reduce the errors between day-ahead scheduling and rolling correction.

Understanding the impact of climate-induced sea level rise on groundwater inundation in a low-lying coastal area: A numerical simulation in Southeast India

Global warming has led to rising sea levels, severely threatening coastal areas, particularly in low-elevation coastal zones. The groundwater in coastal aquifers of lower elevation is susceptible to groundwater inundation (GWI), an emerging hidden long-term hazard earlier to marine inundation. The inundation is mainly due to the hydraulic connection between sea level and shallow unconfined aquifers, resulting in groundwater upsurging towards the ground surface. To understand the potential impact of sea level rise (SLR) induced GWI on low-lying coasts, a transient state model was simulated and predicted in the Cuddalore regions of South India under 0.3 m, 0.6 m, and 1 m SLR scenarios. The simulation reveals that the aerial extent of groundwater rise (GWR) was 331.9 km2, 566.2 km2, and 650.8 km2 for 0.3 m, 0.6 m, and 1 m SLR scenarios, respectively. About 50% of the response was observed in the northern and central parts of the study area within a 5 km buffer, which is attributed to the deeper groundwater table. In contrast, the southern region exhibited a 10% decline in response due to shallow groundwater discharge to drainage, which dampened the shoaling effect. The present-day shallow groundwater tables in the southern region are more vulnerable to GWI from rising sea levels. Specifically, a 0.3 m SLR could inundate 14.9 km2. In comparison, a 1 m SLR could inundate 40.5 km2 of the area, including the Pichavaram mangrove forest, agricultural land, municipal structures, and the other regions that flooding could threaten. These inundations could have potential impacts, such as wetland loss, agricultural flooding, deteriorating water quality, and infrastructural damage. The present study provides valuable insights into the subsurface hydrodynamic and exposure impacts of sea rise-induced inundations. This can aid coastal engineers, policymakers, and decision-makers to plan appropriate mitigation measures.

Control strategies and performance analysis for a novel nuclear heating system with heat storage

A nuclear heating system integrated with a heat storage tank (HST-NHS) is a promising technical solution for countries with large-scale heating demand. HST-NHS can greatly curtail carbon dioxide emissions and contribute to sustainable development. Appropriate control strategies are not only crucial to realize the real-time matching between HST-NHS heat supply and heat demand, but also ensure the stable and safe operation of HST-NHS. Until now, control strategies for HST-NHS have received limited attention. A refined dynamic simulation model for HST-NHS is established based on APROS software. The verification of the built model in steady state and transient state is completed. Two basic control strategies for the primary heating network (PHN) of HST-NHS, constant supply water temperature and variable flow rate (CT-VF) and variable supply water temperature and constant flow rate (VT-CF) are presented in detail. Based on various typical working conditions of a central heating region in Liaoyuan City, the control effects of two control strategies are investigated. Additionally, a comprehensive performance comparison between the two strategies is explored. Simulation results indicated that under the two control strategies, the indoor temperature can be effectively controlled at a high comfort level. During the same typical day, the total energy consumption cost under the VT-CF control strategy is 0.5 × 105 yuan lower than that under the CT-VF control strategy.

Impact of load variation on power system stability and performance of power system stabilizers: A case study of Peerdawd gas power station, Iraq

<span lang="EN-US">Variable load on the station refers to the fluctuating load on a power plant due to erratic consumer demands. It is known to have an effect on the performance of power system stabilizers, particularly in damping inter-area oscillation. This paper examines how two power system stabilizer (PSS) models and various load conditions affect a power system's voltage and power stability. A dynamic model of the power system station, based on the real case study of the Peerdawd gas power station in north Iraq (PPGS), is utilized to investigate the response of both steady-state and transient-state models: the aggregated excitation control system (Ex2100) and the power system stabilizer (PSS2B). The impact of load variation on voltage stability under normal situations and during disturbances is discussed. Furthermore, the effect of reactive power support from the power plant on the input of the two PSS models is analyzed and discussed. The paper employs a MATLABTM/Simulink-based simulation program, and the results contribute to understanding how load variation influences system damping based on PSS.</span>

Transient-state modeling and thermodynamic analysis of self-pressurization liquid hydrogen tank considering effect of vacuum multi-layer insulation coupled with vapor-cooled shield

The transient-state model of self-pressurization of liquid hydrogen tank is constructed. It consists a heat and mass transfer model of fluid domain and a heat conduction model of VMLI (vacuum multi-layer insulation) coupled with VCS (vapor-cooled shield). The vapor consumption factor λv, the dormancy extension factor λd and the unit factor λ are defined. λv is the ratio of vapor consumption with the initial hydrogen mass in tank, and λd is the extension of the dormancy with VCS opened relative to that with VCS closed, and λ is the efficiency of VCS shielding heat leakage. The effects of the mass flowrate in VCS, λv, dimensionless position of VCS, opening moment of VCS on λd and λ are investigated. The results show that, when λv and the operating time of VCS are fixed, the best dimensionless position of SVCS (single vapor-cooled shield) and DVCS (double vapor-cooled shield) that maximizes λd is 0.622 and (0.333,0.644) respectively. Under condition that the duration time of VCS and λv are fixed, for SVCS and DVCS, the best opening moment that maximizes λd is observed to be day 23.26 and day 34.84 respectively, and the maximum of λd with DVCS is 29.5 % larger than that with SVCS.

Probabilistic Analysis of Highly Nonlinear Models by Adaptive Sparse Polynomial Chaos: Transient Infiltration in Unsaturated Soil

Polynomial chaos expansion (PCE) is widely adopted in geotechnical engineering as a surrogate model for probabilistic analysis. However, the traditional low-order PCE may be unfeasible for unsaturated transient-state models due to the high nonlinearity. In this study, a temporal-spatial surrogate model of adaptive sparse polynomial chaos expansions (AS-PCE) is established based on hyperbolic truncation with stepwise regression as surrogate models to improve computational efficiency. The uncertainty of pore water pressure of an unsaturated slope under transient-state rainfall infiltration considering hydraulic spatial variability is studied. The saturated coefficient of permeability [Formula: see text] is chosen to be spatial variability to account for the soil hydraulic uncertainty. The effects of location and time and the performances of AS-PCE are investigated. As rainfall goes on, the range of the pore pressure head becomes larger and the spatial variability of [Formula: see text] has little influence in the unsaturated zone with high matric suction. The pore pressure head under the water table suffers more uncertainty than it in the unsaturated zone. The [Formula: see text] in the high matric suction zone has a trend of rising first and then falling. Except for the high matric suction zone, the [Formula: see text] rise over time and they are almost 1 at the end of the time. It can be concluded that the AS-PCE performs better for low matric suction and positive pore pressure head and the fitting effect gradually increases as the rainfall progresses. The quartiles and at least up to second statistical moments can be characterized by the AS-PCE for transient infiltration in unsaturated soil slopes under rainfall.

Towards the construction of representative regional hydro(geo)logical numerical models: Modelling the upper Danube basin as a starting point

Introduction: Pressure on groundwater resources is increasing rapidly by population growth and climate change effects. Thus, it is urgent to quantify their availability and determine their dynamics at a global scale to assess the impacts of climate change or anthropogenically induced pressure, and to support water management strategies. In this context, regional hydrogeological numerical models become essential to simulate the behavior of groundwater resources. However, the construction of global hydrogeological models faces a lot of challenges that affect their accuracy.Methods: In this work, using the German portion of the Upper Danube Basin (∼43,000 km2) we outline common challenges encountered in parameterizing a regional-scale groundwater model, and provide an innovative approach to efficiently tackle such challenges. The hydrogeological model of the Danube consists of the groundwater finite element code OpenGeoSys forced by the groundwater recharge of the surface hydrological model mHM.Results: The main novelties of the suggested approach are 1) the use of spectral analyses of the river baseflow and a steady state calibration taking as reference the topography to constraint the hydraulic parameters and facilitate the calibration process, and 2) the calibration of the hydraulic parameters for a transient state model by considering parameters derived from the piezometric head evolution.Discussion/conclusion: The results show that the proposed methodology is useful to build a reliable large-scale groundwater model. Finally, the suggested approach is compared with the standard one used by other authors for the construction of global models. The comparison shows that the proposed approach allows for obtaining more reliable results, especially in mountainous areas.

Development and validation of Nusselt number correlations for a helical coil based energy storage integrated with solar water heating system

Storage tanks based on helical coil heat exchangers are an integral part of solar water heating systems and require optimal design configuration to achieve maximum heat transfer and a longer storage period. This study is focused on thermal analysis of a vertical helical coil-based water storage tank and derivation of inner and outer Nusselt number correlations by considering the storage tank as well as helical coil and catering to both forced and natural convection effects. A fluid-fluid conjugate heat transfer transient state model is validated with experiments performed with 50/50 % water-glycol mixture as heat transfer fluid at flow rates of 2 and 3 L/min in a solar water heating system, while water remains at static flow condition inside the tank. To reduce the computational cost, a symmetrical downsized (50 % of the real storage tank size) model is also designed and validated, which showed a mean absolute percentage error of 3.25 %. In order to derive the mathematical correlations, alterations were made to the validated model by using coils with curvature ratios ranging from 0.09 to 0.184 with HTF flow rates in laminar flow regimes, ranging from 30 to 100 L h−1 at temperatures from 40 °C to 80 °C. Furthermore, inner Nusselt number mathematical correlations based on M number, curvature ratio, and Prandtl number showed good agreement with correlations derived by past investigators. Similarly, the outer Nusselt number of the coil was related to Rayleigh's number and the derived relations showed good agreement with the past studies, while Nuo = 0.1996 (Rado0.326) showed the least error of 2.06 %. Finally, thermal stratification analysis helped to understand that coil position and aspect ratio determine the thermocline developed inside the storage tank. Results show that extension of coil inside the tank up to 83.7 % of the tank height, ensured greater thermocline range, and tank with aspect ratio 3 turned to be better for thermal energy storage for longer period.

Cr Poisoning in SOC Stacks

Solid oxide cell stacks (SOCs) usually use a Cr-containing alloy as the interconnect, which requires the air electrode not only to exhibit satisfying electrochemical performance, but also a high resistance to Cr poisoning. This is because during operation volatile Cr species will diffuse from the oxide scales on the interconnect to the air electrode, leading to a fast degradation. Currently, Forschungszentrum Jülich (FZJ) applies an MCF (MnCo1.9 Fe0.1O3–δ) coating by means of atmospheric plasma-spraying (APS) on the interconnect. This coating reduces the degradation rate from 0.9 % / kh to ~ 0.3 % / kh. However, according to distribution of relaxation time (DRT) figures, Cr poisoning is still a major contribution to overall degradation in the beginning of the operation.In order to further alleviate issues of Cr poisoning, an LSC (La0.6Sr0.4CoO3 –δ) air electrode was investigated. Based on previous studies, the LSC electrode was expected to be more resistant to Cr poisoning compared to LSCF (La0.58Sr0.4Co0.2Fe0.8O3 –δ). Long-term tests demonstrated a lower degradation rate for LSC air electrodes compared to LSCF air electrodes and LSC adsorbed less Cr than LSCF even if the operation time of the SOC stack with LSC air electrode was twice longer [1]. For improving the understanding of the degradation mechanisms of Cr poisoning on LSC and LSCF, an accelerated test was carried out. The test was done with a rainbow stack that used LSC (RU A) and LSCF (RU B) air electrodes in different repetitive units (RU) of the stack. To quickly degrade the air electrodes, no protective coatings were added on the interconnects and 1.4509 stainless steel was used instead of Crofer 22 APU. Besides, the operation condition (775 ºC, 0.75 A/cm2) was harsher than that of previous tests (730 ºC, 0.5 A/cm2). Due to fast degradation, the stack was shut down after only 1,700 h operation. Latest analysis of this stack showed the peak attributed to air electrode polarization in the DRT deconvolution for EIS spectra of RU A cells increased evidently while that of RU B cells barely changed. This was a contradictory finding to previous understanding as it indicated it was LSCF instead of LSC that was more resistant to Cr poisoning. A possible reason might be a lower chemical stability of LSC to volatile Cr species at high temperature and current density. To clearly reveal the reason, Cr distribution and deposited Cr amount in the air electrode needs to be determined. Post-test characterization, such as SEM, EDX and ICP-OES, is undergoing.In addition, a steady-state multiphysical three-dimensional model of an SOC was developed with the open-source software OpenFOAM. Momentum transfer, mass transfer and electrochemical reactions were successfully included in the model. A coupled solver was applied to solve the ionic and electronic potential across different regions. The model was verified by the comparison of the simulation results of the OpenFOAM model with the simulation results of an equal model developed with the commercial software COMSOL, whereas the same mesh, geometry, and parameters were used. Also, the OpenFOAM model was validated by a comparison of the simulation results with experimental results under different operation modes (e.g., fuel cell and electrolysis modes) and temperatures. Assisted by the model, the spatial distribution of the local mole fraction of oxygen and local overpotential in the air electrode could be revealed, which was helpful in analyzing Cr poisoning. As expected, it was found that the overpotential mainly became non-zero at the interface between the air electrode and the electrolyte. Since Cr is mainly observed near the interconnect interface of the LSCF air electrode in post-test examinations, the Cr deposition is expected to primarily arise from chemical reactions. Plus, owing to higher current density on the rib, the mole fraction of oxygen was also lower under rib, where more Cr deposition can be triggered owing to lower oxygen partial pressure. Micro-kinetic modelling of the reduction of adsorption sites owing to Cr poisoning is under development.After the governing equations related to degradation will be included, the model will become a transient-state model which is capable of predicting the voltage with evolution of time.

Preliminary study on FROBA-SCO2 with transient models and its application for Reactivity Initiated Accident and loss of flow accident

As a coolant enabling the reactor with a high efficiency and low volume, the supercritical CO2 has becoming a hot topic nowadays. However, the fuel rod behaviors under accidents are not studied thoroughly, especially the interaction between the coolant and the cladding. With the previous study of fuel rod behaviors analysis of supercritical CO2 cooled nuclear reactor under steady state operation, transient state models are implemented and the upgraded code can be used to predict the fuel rod behaviors under RIA and LOFA. After the comparation of the calculation results with SACOS-SCO2, the tendency and numerical value are close, so the accuracy is warranted. The upgraded FROBA-SCO2 is used to predict the fuel rod behaviors under RIA and LOFA conditions and the results indicate that the maximum temperature of cladding and fuel is within safety limits.

T4F3: temperature for fused filament fabrication

Temperature fields and their variations in printed parts are the basis for understanding the physical process of fused filament fabrication (FFF). However, reliable temperature data are still rather limited to date. This article presents a three-dimensional transient-state model to simulate the temporal and spatial temperature variations in FFF printed parts. Model variables range from geometry dimensions and (dynamic) material properties to process parameters, covering all important physical phenomena, including conduction anisotropy and radiant heat transfer. The validation of the model is performed against six sets of experimental temperature data obtained with different geometries, machines, materials, processes, temperature measuring methods, etc. Insights in the thermal process are also reported. For example, the heat penetration depth in printing with poly(lactic acid) is limited to 3 mm, and the Biot number intimately characterises the reheating peaks in temporal profiles. This model shows the potential to become a standardised tool to study the thermal characteristics of FFF printed parts. It is made openly available on website https://iiw.kuleuven.be/onderzoek/aml/technologyoffer.Graphic abstract

Transient Dean flow in a composite annular duct with porous walls partially filled with porous material

This work presents a semi-analytical solution of transient Dean flow in a composite annular duct with porous walls partially filled with porous materials. The flow is set up as a result of the imposed pressure gradient in the azimuthal (θ) direction while both the outer and the inner cylinders are fixed. The appropriate governing equations for the flow are rendered dimensionless and transformed using suitable techniques, the Laplace transform technique is further used to transform the partial differential equations into the total differential equation. The solution of the ODE is later transformed to the time domain using the well-known Riemann-sum approximation approach. To validate the accuracy of the numerical scheme deployed in this research, numerical comparison of the steady-state solution, and the values generated using the implicit finite difference on the transient state model is presented. Generally, higher dominance of clear fluid and fluid injection at the inner cylinder is found to enhance the fluid velocity at the fluid interface. It is also good to note that injection of fluid at the inner cylinder pose a decreasing influence on the flow with minimum or no effect near the point R = 1.7.

Assessment and simulation of a solid waste dumpsite impact on the surrounding water resources: A case study in Abu Zaabal, Egypt

Indiscriminate dumping of solid wastes and the resulting groundwater contamination is a major issue, especially for developing countries. The main objective of this paper is to develop a groundwater mass transport model in order to study the effect of an open solid waste dumpsite on the water quality of water resources within the region around it. The harmful effects of indiscriminate solid wastes disposal by open dumping, which is still followed in many developing countries around the world, is highlighted. Abu Zaabal dumpsite; which is located in Qalyubiyah Governorate, Egypt; receives huge amounts of wastes daily causing leachate generation that percolates deep into the soil and polluting the shallow aquifer. The Groundwater Modeling System (GMS) software was used to model the groundwater flow and mass transport, using data collected from the site investigation and literature historical data available. Of the several contaminants measured in the site, six critical contaminants; namely Total Dissolved Solids (TDS), Lead, Boron, Nitrate, Manganese and Chemical Oxygen Demand (COD); were chosen to be modeled. The developed model was used to simulate the six contaminants using a transient-state model and concentration values for two different scenarios. Scenario-1 assumes that the dumpsite will be active until 2080, whereas Scenario-2 represents imminent closure of the dumpsite. The model results of each contaminant were calculated over 100-year interval, from 1980 until 2080, and the results of 2080 were presented. The results showed that the dumpsite had a major impact on the nearby water bodies, Abu Zaabal ponds and Belbais Drain. Moreover, the closure of the dumpsite showed that the maximum concentration of the majority of the considered contaminants was decreased by approximately 60–65%.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

PurposeVolumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress.Design/methodology/approachThe design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events.FindingsThe steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions.Originality/valueThermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

SALEACH: A new web-based soil salinity leaching model for improved irrigation management

Leaching is essential in irrigated croplands where natural precipitation is insufficient to control salinity buildup. Several useful models exist for salinity management; however, leaching requirement (LR) calculations are based on steady-state approaches that only consider salinity tolerance of crops and irrigation water salinity to estimate the LR. In this study, a web-based soil salinity leaching management model (SALEACH) was developed as an online tool to assist growers for better and easier management of soil salinity to sustain agricultural production in irrigated croplands. SALEACH employs the traditional steady-state approach to estimate LRs but improves outputs by not only considering irrigation water salinity (ECiw) and salinity tolerance of specific crops (ECt), but also root water uptake patterns to account for irrigation system differences, and soil types for differences in hydraulic characteristics, as well as water stress and rainfall input. The SALEACH model can calculate the required irrigation water depth by using the estimated LR or any user-specified leaching fraction (LF) values; it can predict the drainage water salinity and soil salinity in the rootzone based on the applied leaching; and it can estimate relative crop yield for a given LF. SALEACH-estimated LRs were assessed in different soil types and irrigation systems by comparing them with LRs, soil water and drainage water salinity values obtained from an existing steady-state model (WATSUIT) and a transient-state model (HYDRUS-1D). Statistical analyses showed that SALEACH-estimated LRs, soil salinity, and drainage water salinity were all in the acceptable ranges of the corresponding values derived from other models. Thus, we conclude SALEACH is reliable and can be employed by practitioners to produce satisfactory estimations of LRs and soil salinity by considering the soil, crop, water quality, and irrigation system. Adoption of the model can improve water use efficiency and reduce groundwater pollution.

Upgrading waste material flow analysis with process models: The case of anaerobic digestion

Material flow analysis (MFA) has been shown to be a valuable tool for goal-oriented decision making of waste management systems. When used to evaluate or compare waste management scenarios, it relies on applying transfer coefficients to model how the flows of goods and substances are transformed through waste treatment processes. Although transfer coefficients provide a useful simplification, their applicability to represent complex processes such as anaerobic digestion (AD) is limited. In this study, three levels of model complexity were compared to upgrade an MFA: a material-specific empirical transfer coefficient method using the biochemical methane potential, a kinetic method using a first-order model, and a process-based method using the Anaerobic Digestion Model No. 1 (ADM1). The three models were integrated in an MFA and compared based on their prediction of methane production and nitrogen recovery for different waste compositions, reactor operating conditions and simulation time steps. The results showed that the simpler models were sufficient to predict the methane production, but that only complex models such as ADM1 could predict behaviour regarding the loss of nitrogen in the liquid digestate. The results also showed the advantages of integrating the model in transient state for nitrogen modelling. An MFA upgraded with a process model such as ADM1 allows to better implement the analysis on both the levels of goods and substances and can be useful for the case of waste treatment processes other than AD.

Assessment and Simulation of a Solid Waste Dumpsite Impact on the Surrounding Water Resources: A Case Study in Abu Zaabal, Egypt

Indiscriminate dumping of solid wastes and the resulting groundwater contamination is a major issue especially for developing countries. The main objective of this paper is to develop a groundwater mass transport model in order to study the effect of a solid waste open dumpsite on the water quality of the water resources within the region around it which highlights the harmful effects of indiscriminate solid wastes disposal by open dumping which is still followed in many developing countries around the world. Abu Zaabal dumpsite which is located in Qalyubiyah Governorate, Egypt receives huge amounts of wastes daily which is considered a source of pollution due to leachate generation that percolates deep into the soil reaching the shallow aquifer. The Groundwater Modeling System (GMS) software was used to model the groundwater flow and mass transport, using data collected from the site (site investigation) and literature historical data available. Of the several contaminants measured in the site, six were chosen to be modelled as they were the most critical. These contaminants are Total Dissolved Solids (TDS), Lead (Pb), Boron (B), Nitrate (NO - 3 ), Manganese (Mn) and Chemical Oxygen Demand (COD). The model developed was used to simulate the aforementioned contaminants using a transient-state model and the concentration values for two different scenarios. Scenario-1 assumes that the dumpsite is still active till the year 2080 and Scenario-2 represents the closure of the dumpsite right now. The model results of each contaminant were calculated between 1980 and 2080 (i.e. 100 years) and in this study, 2080 results were presented. The results showed that the dumpsite had a major impact on the nearby water bodies, Abu Zaabal ponds and Belbais drain. Moreover, the closure of the dumpsite showed that the maximum concentration of the contaminants decreased by approximately 60-65% for the majority of them.

Sub-channel thermal-hydraulic analysis for VVER- 1000 generation III PWR

The sub-channel thermal-hydraulic analysis of a nuclear reactor is essential for assessing of its safety aspects. In this paper, the VVER-1000 has been selected as an example of the third generation reactors since it meets most of the international safety standards and because it has been taken as a base for designing the VVER-1200 which is belonging to the III+ generation. A steady state mathematical model has been proposed and solved to validate and assure that the hottest channel temperature limits are satisfied. The various temperature distributions, the critical heat flux and the departure from nucleate boiling ratio (DNBR) for the hottest channel were evaluated. Also, a transient state model has also been presented and solved using the finite difference method with the aid of MATLAB algorithm. An exponential loss of flow rate of the reactor core coolant was triggered from the steady state conditions. We assumed that the neutron flux and the generated power were unchanged during the postulated event. The average core coolant flow time constant was treated as a single parameter expressing the rapidity of the event. A value of 250 seconds time constant was assumed for slow transient, whereas 10 seconds was assumed for fast one. The reactor core was assumed to be protected through the reactor control system and mitigated according to the regular emergency operating procedures. The time dependent temperature distributions were calculated for the cladding of the hottest coolant channel. For each value of the temperature, the response time required for reaching unsafe conditions was evaluated, discussed and presented.