Computational fluid dynamics (CFD) has become a widely used tool for predicting hazardous scenarios. The present study aimed to assess CFD prediction applied to LPG containers under heating. Thus, two cylinders, each filled with propane or butane, were experimentally exposed to fire, and the pressure increment was recorded. The results were compared with those provided by a CFD method (Ansys Fluent). The limitations of the method are discussed, and a trend in the error increment and its relation to the reduced temperature increment are presented. The results obtained show that the computational method had a good agreement, with a relative error of 19% at a reduced temperature equal to 2. Furthermore, the method had a better fit with heavier alkanes, as the butane was less influenced by temperature overestimation compared with propane.

The heritage of ancient buildings is an important part of the world’s history and culture, which has extremely rich historical−cultural value and artistic research value. Beijing has a large number of ancient palace buildings, and because of the age of their construction, many of them have problems with varying degrees of peeling and molding on the inner surfaces of the envelope. To solve the problems of damp interiors of palace buildings, a mathematical model of indoor heat and moisture transfer was established based on an ancient wooden palace building in Beijing. The model was validated by fitting the measured and simulated data. And the effects of outdoor relative humidity, soil moisture, wall moisture, and other factors on indoor heat and moisture transfer of ancient buildings were simulated and analyzed via the control variables method. The results showed that the measured and simulated data are within the error range, which verifies the accuracy of the model. And the simulation... [more]

Ship-to-shore connection is an important technological element that reduces air pollution in ports. Therefore, ports install facilities that allow mooring ships to connect to the port distribution network. By 2025, this will be mandatory for all ports in Europe. This can be a challenging task in most ports due to the different frequency of the network and ship frequency. This problem can be solved by the use of grid-forming static frequency converters. This solution also brings some other advantages: The ship is not threatened by high shore short-circuit currents, and the port distribution network is not affected by the character of the ship load. However, frequency converter software must include a droop control algorithm to ensure that voltage deviations do not exceed the allowed limits during transients. Typical frequency converters used for shore connection are those developed as static frequency converters (SFCs). However, those converters were not developed for large power output... [more]

Naturally fractured formations usually have strong heterogeneities. Drilling and production operations in such formations can involve unwanted formation failure risks such as wellbore collapse and wellbore fracturing. This study presents a coupled thermal-hydraulic-mechanical numerical model for near-well stress evolutions during drilling in naturally fractured formations. The evolution of pressure, temperature, and geo-mechanical responses on the wellbore wall and in the near-well region is simulated. The effects of wellbore pressure, internal friction angle, and natural fracture length on formation rock risks are discussed. A failure index is used to quantify the formation rock failure risks. The existence of natural fractures magnifies the heterogeneous system response induced by drilling. Increasing the wellbore pressure from a relatively low value can improve the support for the wellbore wall, which reduces the failure risks caused by shearing. In mechanically weak formations, the... [more]

The landfill barriers effectively prevented the migration of high-concentration pollutants, such as NH4+ and Na+, from the landfills to the surrounding environment. However, due to the high hydraulic head inside the landfill compared to the surrounding environment, NH4+ and Na+ can migrate towards the outside of the landfill barrier with the infiltrating solution, potentially causing harm to the surrounding environment. To address this, saturated mixed soil column samples made of bentonite and Shanghai clay, with bentonite contents of 3% and 10%, were used in this study. Permeability coefficients of the column samples in solutions are obtained by using permeation tests, and using NaCl and NH4Cl solutions with concentrations of 37.4 mmol/L and 74.8 mmol/L, respectively. The concentration-depth result of the column samples after permeation tests was determined using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Ion Chromatography (ICS-1100). Numerical simulations... [more]

The tremendous and fast green transition in Denmark has initiated the large-scale grid-integration of renewable energy sources, electrification of energy consumption, and establishment of PtX and Energy Islands, setting goals for transmission grid development—such as the establishment of new connections—and for grid reconstruction—such as the extensive substitution of overhead lines (OHLs) with underground cables (UGCs). The share of UGCs in the Danish transmission grid is increasing. Presence of UGC has resulted in that resonances of the harmonic impedance characteristics of the transmission grid are brought within the harmonic order range coinciding with the harmonic emission sources and causing systemwide increase of the harmonic voltage distortion in the 400 kV transmission grid. The transformation of the 400 kV transmission grid has given rise to the need to predict harmonic voltage distortion using simulation models to secure an adequate power quality and support investment decis... [more]

A successful guaranteed launch of a mainline diesel locomotive is one of the most important and urgent problems of the rolling stock operation. Improvement of the start-up system of the main diesel locomotive when using a supercapacitor allows multiple restarts of diesel locomotives, meaning that the operation of the diesel locomotive can be stopped several times without wasting fuel in idle operations. In this study, we simulated the electric starting circuit of a diesel locomotive with a block of supercapacitors using the Matlab Simulink program. The simulation results show that using only a supercapacitor in the start-up system is impossible. Even though the supercapacitor produces the required current and voltage, its operating time is extremely insufficient. Using a storage battery along with a supercapacitor in the diesel locomotive start-up system is most effective. This reduces the peak current load on the standard battery. The article suggests an effective principle for starti... [more]

Greenhouses with efficient controlled environment offer a promising solution for food security against the impacts of increasing global temperatures and growing water scarcity. However, current technologies used to achieve this controlled environment consume a significant amount of energy, which impacts on operational costs and CO2 emissions. Using advanced metal organic framework materials (MOFs) with superior water adsorption characteristics, this work investigates the development of a new technology for a greenhouse-controlled environment. The system consists of MOF coated heat exchanger, air to air heat exchanger, and evaporative cooler. A three-dimensional computational fluid dynamics (CFD) model was developed using COMSOL software and experimentally validated for the MOF-801/Graphene coated heat exchanger (DCHE) to determine the best cycle time and power input. It was found that using desorption time of 16 min and power input of 1.26 W, the maximum water removal rate was obtained... [more]

Improving mass transfer in gas diffusion layers is critical to achieving high-performance proton-exchange membrane fuel cells (PEMFCs). Leaks through the interface between the gas and the membrane electrode assembly frame have been widely investigated, and the controllability of the cathode gas diffusion has not been achieved in most studies. In this study, we develop a structural parameter to investigate the controllability of the gas diffusion mechanism in the cathode in order to improve upon the design and performance of PEMFCs. This parameter accounts for the cathode gas diffusion layer porosity and carbon loading inside the catalyst layer. It is comprehensively calculated to relax the two segments’ distribution along three directions of the coordinate axis. The experimental and simulation results show that the obtained values of the parameter vary and change during voltage stabilization. According to the results, regardless of the materials in the cathode gas diffusion layer, the... [more]

The examination and choice of an alternate composite material for the high-voltage circuit of Otto cycle internal combustion engines—more commonly known as gasoline engines—are presented in the research that follows. To do this, multicriteria selection procedures are employed, and the outcomes are validated through the use of thermal character simulation software and standard laboratory tests. Nylon is the recommended material for Coils on Plug (COP) high-voltage insulators. Four of the six multicriteria selection techniques utilized in this study were found to be effective. It was discovered through the virtual simulation process that, even in the same environment with the same edge circumstances, the thermal behavior of the materials differs dramatically because the quadrants exhibit different behavior depending on the material. Given that nylon has a lower elasticity modulus than silicone, it was determined that the dimensions are crucial for the nylon Spark Plug Boot (SPB) to compl... [more]

The aim of using electromechanical air conditioning in buildings is to maintain thermal comfort for its occupants; however, this type of air conditioning represents 40% of the total energy consumption of a building, generating economic and environmental impacts, because fossil fuels are the main source of energy. To reduce the use of electromechanical conditioning, it is possible to take advantage of the climatic conditions of the region to improve its performance. Due to the small number of works that quantitatively support measures aimed at improving the thermal behavior of houses in an integral way and the growth of mass construction in Mexico, in the present work, a solar chimney is incorporated in a typical type of social interest housing in Guanajuato. The incorporation of the solar chimney was simulated by using computational fluid dynamics (CFD) using ANSYS and evaluated by ASHRAE Standard 55-2017. The selected arrangement induces air flow inside without the need for external f... [more]

Hydraulic fracturing is an effective method for stimulating reservoirs, making the economic development of ultra-tight shale gas and coalbed methane reservoirs possible. These formations are rich in nanopores, in which the fracturing fluid, such as fresh water, the flow, and the behavior of this flow differ significantly from those described in the classic Navier-Stokes formula. In bulk space, the interaction force exerted by the solid phase can be ignored, but the solid−fluid interaction plays a dominant role in nanoconfinement spaces in which the pore size is comparable to the molecular diameter. Nanoconfined water molecules tend to approach the water-wet pore surface, enhancing the water viscosity, which is a key parameter affecting the water flow capacity. Conversely, water molecules tend to stay in the middle of nanopores when subjected to a hydrophobic surface, leading to a decrease in viscosity. Thus, nanoconfined water viscosity is a function of the strength of the surface−flui... [more]

The purpose of this paper is to study the actual dynamic load characteristics of a full-scale Accelerated Pavement Test (APT) device called Natural Environment-Automatically Loaded Track (NE-ALT) during its operation. The NEALT uses hydraulic and support reaction forces to apply axle loads, which are somewhat different from real trucks. Therefore, in order to ensure the accuracy of the loading parameters of the device, it is necessary to analyze the dynamic load characteristics of the device during operation. In this paper, a virtual prototype model of the device was established, and the important parameters, including vehicle speed and axle load, were set. The dynamic axle load, dynamic load coefficient, and influential factors of the NE-ALT were analyzed using the model at different speeds, hydraulic pressures, and road roughness. The results have shown that the dynamic axle load accuracy was most affected by speed, followed by road roughness, and then hydraulic cylinder pressure. Co... [more]

This paper introduces and studies a new discrete distribution with one parameter that expands the Poisson model, discrete weighted Poisson Lerch transcendental (DWPLT) distribution. Its mathematical and statistical structure showed that some of the basic characteristics and features of the DWPLT model include probability mass function, the hazard rate function for single and double components, moments with auxiliary statistical measures (expectation, variance, index of dispersion, skewness, kurtosis, negative moments), conditional expectation, Lorenz function, and order statistics, which were derived as closed forms. DWPLT distribution can be used as a flexible statistical approach to analyze and discuss real asymmetric leptokurtic data. Moreover, it could be applied to a hyperdispersive data model. Two different estimation methods were derived, i.e., maximal likelihood and the moments technique for the DWPLT parameter, and some advanced numerical methods were utilized for the estimati... [more]

In many process engineering fields, gas-particle fluidized beds are widely used. In fluidized bed research, the discrete element method, or DEM, has been a powerful tool for design and operation purposes. However, with the use of Type-A powders, fluid catalytic cracking or FCC particles being classical cases, they have hardly been reported in DEM simulations of fast fluidization. This study paid close attention to the suitable selection of a stiffness constant and a DEM time step. To reflect their respective effects and complicated interactions, a so-called relative DEM time step was defined. The drag coefficient was correlated using the energy-minimization multi-scale (EMMS) approach to reasonably calculate the gas−solid interaction. Six representative cases with different relative time step values were chosen to simulate a micro-fluidized bed of Type-A FCC powders. The results showed that DEM employing EMMS-based drag force was able to greatly enlarge the suitable range of relative t... [more]

A plate-type Al/Fe−Cr alloy/Al-clad substrate was used to prepare a sandwich-structured plate-type anodic alumina catalyst by anodization, post-modification treatment, and metal loading. The as-prepared plate-type catalyst was utilized in the design of a catalytic plate reactor for a methane steam reforming reaction, and a 3D model was developed to simulate the performance of tube-type and box-type reformers. The experimental results of the preparation of the clad materials showed that the hydrothermal treatment and subsequent high-temperature calcination transformed the amorphous skeletal alumina in the conventional anodic alumina layer into γ-alumina, and significantly increased its specific surface area. Simulation results showed that the temperature difference between the channel wall and the center of the gas phase of the thin-walled catalyst was only 30% of that of the particulate catalyst, indicating the potential advantages of the catalytic plate reactor in terms of heat transf... [more]

The huge influence of the sampling rate on the performance of the digital PID control of a voltage source inverter (VSI) is revealed. It is shown that an appropriately chosen continuous-time model of a digital controller with the PWM power converter behaves like the actual discrete-time system, which allows for a simple controller analysis and design. The variable structure nature of the inverter with both the RC rectifier and an abruptly changing resistive load with two modes of operation within the sampling period is directly taken into account. Two simulation models, a discrete-time PWM and a continuous-time, of an inverter are presented, which are used to tune the PID controller and to evaluate the control performance. The behavior of the system in both modes is explained on the basis of the root loci and frequency characteristics. The results obtained for three sampling rates: 12.8, 25.6, and 51.2 kHz, are presented and compared with an actual VSI experiment. A comparison with oth... [more]

The present paper proposes a new methodology to aid the electrification process of local public transport (LPT). In more detail, real drive cycles of traditional buses currently in use are evaluated together with other data to simulate the consumption of equivalent e-buses (electric buses) with similar characteristics. The results are then used in order to design the best charging infrastructure. The proposed methodology is applied to the case study of Algeciras Bay, where a specific line of LPT is considered. Real measurements are used as data for the simulation model, and the average consumption of an equivalent e-bus is obtained for different operating conditions. Based on these results, different sizes and locations for fast-charging infrastructure are proposed, and the size of the depot charging system is defined trying to maintain the current buses timetable. Finally, some future developments of the present work are presented by considering other bus lines that may benefit from t... [more]

The testing of the standard and modified SST models of the transfer of shear stresses was carried out on an example of calculating the heat transfer with an intense detached flow around a conical dimple with a slope angle of 45° on the heated wall of a narrow channel. It was shown that the standard turbulence model by Menter SST (MSST) of 2003, widely used in the packages Fluent, CFX, StarCCM+, etc., significantly underestimated the intensity of the return flow. A correction of this model was presented that took into account the influence of the curvature of streamlines within the framework of the Rodi-Leshziner-Isaev (RLI) approach for spatial separated flows. It was found that the predictions for the RLI MSST 2003 were close to the predictions for the original standard MSST 1993, in which the eddy viscosity was calculated using the vorticity modulus. At the same time, the predictions based on the modified one, following Smirnov-Menter (SM) MSST 2003, included in the ANSYS model catal... [more]

This paper proposes a computational process development capable of filling the electric power sector shortage regarding voltage non-conformities identification in electric distribution power grid accounting for loads dynamic behavior at medium and low voltages. Actual distribution power grid data are used, with georeferencing to signal voltage transgressions locations, generate a report with voltage transgression indices and financial reimbursement values provided by legislation. The methodology compares regulatory requirements and makes available in software some possible actions in an attempt to adjust voltage levels, avoiding inconvenience and penalties for energy utilities providers. The method involves a data extractor construction for electricity provider company’s databases, computer simulations and comparison of obtained results with values established in electricity quality control standards. Thus, finding non-conformity locations and determining network adjustments to correct... [more]

This work aims to study the drying of clay ceramic materials with arbitrary shapes theoretically. Advanced phenomenological mathematical models based on lumped analysis and their exact solutions are presented to predict the heat and mass transfers in the porous material and estimate the transport coefficients. Application has been made in hollow ceramic bricks. Different simulations were carried out to evaluate the effect of drying air conditions (relative humidity and speed) under conditions of forced and natural convection. The transient results of the moisture content and temperature of the brick, and the convective heat and mass transfer coefficients are presented, discussed and compared with experimental data, obtaining a good agreement. It was found that the lower the relative humidity is and the higher the speed of the drying air is, the higher the convective heat and mass transfer coefficients are at the surface of the brick and in the holes, and the faster the moisture removal... [more]

Battery electric vehicles offer many advantages in terms of performance and zero-emission pollutants, but their limited range for long-distance trips compromises their large-scale market penetration. The problem of range can be solved with a dense network of fast-charging stations and an increase in embedded battery capacity. Simultaneously, improvements in high-power charging point units offer range gains of hundreds of kilometers in a mere 20 min. One risk remains: The travel time depends on the availability of charging stations, which can drop during rush hours, due to long queues, or power grid constraints. These situations could significantly affect the user experience. In this paper, we presented an approach to coordinate EV charging station choices in the case of long-distance trips. This system relies on vehicle-to-infrastructure communications (V2X). The objective is to enhance the use of the infrastructure by improving the distribution of vehicles between the different chargi... [more]

This article discusses the optimization of railway transition curves, through the application of polynomials of 9th and 11th degrees. In this work, the authors use a 2-axle rail vehicle model combined with mathematically understood optimization methods. This model is used to simulate rail vehicle movement negotiating both a transition curve and circular arc. Passenger comfort is applied as the criterion to assess which transition is actually is the best one. The 4-axle vehicle was also used to verify the results obtained using the 2-axle vehicle. Our results show that the traditionally used in a railway engineering transition—3rd degree parabola—which is not always the optimum curve. This fact is especially valid for the longest curves, with lengths greater than 150 m. For such cases, the transition curves similar to standard curves of 9th and 11th degrees is the optimum ones. This result is confirmed by the use of the 4-axle vehicle.

The objective of this research was to design a neural network (ANN) to predict the methanol flux at the outlet of a carbon dioxide dehydrogenation plant. For the development of the ANN, a database was generated, in the open-source simulation software “DWSIM”, from the validation of a process described in the literature. The sample consists of 133 data pairs with four inputs: reactor pressure and temperature, mass flow of carbon dioxide and hydrogen, and one output: flow of methanol. The ANN was designed using 12 neurons in the hidden layer and it was trained with the Levenberg−Marquardt algorithm. In the training, validation and testing phase, a global mean square (RMSE) value of 0.0085 and a global regression coefficient R of 0.9442 were obtained. The network was validated through an analysis of variance (ANOVA), where the p-value for all cases was greater than 0.05, which indicates that there are no significant differences between the observations and those predicted by the ANN. Ther... [more]

Pumped Thermal Energy Storages (PTES) are suitable for bridging temporary energy shortages, which may occur due to the utilization of renewable energy sources. A combined heat pump (HP)-Organic Rankine Cycle (ORC) system with suitable thermal storage offers a favorable way to store energy for small to medium sized applications. To address the aspect of flexibility, the part load behavior of a combined HP-ORC system, both having R1233zd(E) (Trans-1-chloro-3,3,3-trifluoropropene) as working fluid and being connected through a water filled sensible thermal energy storage, is investigated using a MATLAB code with integration of the fluid database REFPROP. The influence on the isentropic efficiency of the working machines and therefore the power to power efficiency (P2P) of the complete system is shown by variation of the mass flow and a temperature drop in the thermal storage. Further machine-specific parameters such as volumetric efficiency and internal leakage efficiency are also conside... [more]