Values Of Loss Coefficient Research Articles

Quaternary phase-field simulation of the effect of additives on the structure of polyvinylidene fluoride microporous membranes

This study builds upon the existing phase-field model of the non-solvent-induced phase separation (NIPS) method, simulating factors that influence membrane formation in a ternary system. A polyvinylidene fluoride (PVDF) membrane system is utilized, and a fourth substance, an additive, is introduced based on the original mathematical model of the ternary system. The interaction parameters of the additives within the system are calculated using the Krevelen method. The simulation is configured to set the values of additive mobility and loss coefficients of the concentration gradient, thereby simulating the effect of additives in the quaternary system on the evolution of the micropore membrane structure. Finally, simulated images of different concentrations of additives with various types are compared with experimental results of microporous structure and porosity formation. This comparison serves to validate the model.

Numerical Study of Fluid Flow in a Gyroid-Shaped Heat Transfer Element

This paper deals with the design of porous geometry of a heat transfer element. The proposed geometry combines a gyroid triply periodic minimal surface with the recursive principle of geometric body creation. The designed geometry is based on an attempt to increase the heat transfer surface while eliminating negative impacts on the fluid characteristics in the form of pressure loss or increase of the friction coefficient. The proposed geometry of the heat transfer element was compared with a pair of geometries based on the basic gyroid shape but with different channel size parameters. A numerical simulation was performed in Ansys Fluent 2020 R1 using the SST k-omega turbulence model for flow velocities in the range of 0.01 m.s−1 to 0.5 m.s−1, which covered a wide range of the Reynolds number and thus also flow forms in terms of the turbulence intensity. The presented results clearly show lower values of pressure loss and friction coefficient of the proposed geometry compared to the evaluated porous structures. Also, at the same time, they describe the factors positively influencing the mixing process of the liquid in the proposed element, which leads to an increase in the efficiency of the heat transfer process.

Mechanical Properties of Silica Fume Concrete in Marine Environment

Concrete is a common material used in marine structures. Cement, as a concrete-forming substance, contributes to global CO2 emissions. Reducing cement by adding Silica Fume transforms concrete into green concrete without reducing its quality. Concrete construction in the marine area is commonly affected by abrasive factors such as water penetration, waves, and sea currents. Concrete materials have good quality, as shown by their mechanical properties. This study examined how Silica Fume affected the mechanical characteristics of concrete. The specimens were made with variations of Silica Fume 5%, 7%, and 10% by weight of Cement, then cured with seawater. Tests are carried out for mechanical properties such as compressive strength, flexural strength, permeability, and abrasion mass loss. The test results showed that the compressive and flexural strength values achieved good results, and the weight loss and abrasion coefficient values were better than ordinary concrete.

Methods for modeling the dissipative characteristics of layered composites

The main methods for modeling dissipative characteristics of layered composites are considered: the principle of elastic-viscoelastic correspondence and energy method. Mathematical models of damped oscillations are given for layered anisotropic plates. A numerical procedure for solving the problem of damped oscillations of a three-layer monoclinic plate containing a two-stage method for solving a complex eigenvalue problem. It is noted that the energy method for modeling energy dissipation at vibrations of layered composite structures is a special case of the method, based on the principle of elasticviscoelastic correspondence. Shown, that in addition to the classical formulation of the energy method, in which the terms energy balance equations are approximately found by their own forms and vibration frequencies of a conservative mechanical system, there is one more an approximate method for calculating the dissipative characteristics of orthotropic composite structures. The advantages of this method are the possibility of using existing commercial software systems (Ansys et al.), which numerically implement the finite element method, and shortcomings - the need to be limited to the use of classical theories of thinwalled structures (Bernoulli-Euler, Kirchhoff-Love) for descriptions of deformation of composite structures. It has been found that the use the classical formulation of the energy method allows with a high accurately predict the values of mechanical loss coefficients up to ηmax = 0.02. Further increase in damping levels construction is accompanied by a decrease in the accuracy of the forecast.

Determining mechanical and acoustical behaviors of all-recycled PP sandwich structures with bi-directional sinusoidal corrugated core

By recycling the waste polymer material and using it in weight reduction studies of electric vehicles, a double-sided gain is achieved against environmental pollution. Sandwich structures with prismatic cores obtained by recycling waste polymers can be used in structural applications of light and heavy commercial vehicles and public transportation vehicles that carry cargo and passengers. These sandwich vehicle parts could help to increase the max. range and load-carrying capacity of electric vehicles. In this study, sandwich plates with prismatic egg-box cores were produced with waste Polypropylene. Since the materials are collected from different waste sources, the physical properties (additive ratio, secondary substance determination, density) of the recycled material were measured. Thereafter, hardness, quasi-static flatwise and edgewise compression, and 3-point bending tests were done to determine the mechanical properties of the structure. After that, dynamic compression and 3-point bending tests were performed to determine the strength and impact energy absorption capacity of the structure in collision situations. Finally, impedance tube tests were carried out for the acoustic characterization, which is one of the important parameters affecting interior cabin comfort, and Sound Transmission Loss (STL) and Sound Absorption Coefficient (SAC) values of the structure were determined.

Model comparison and effect of flow and accessories on the pressure drop of the unit ff-df-270/el of Universidad de Cartagena

The effect of flow variation on the theoretical calculation of pressure drop in pipes with fittings in the unit FF-DF-270/EL of the Universidad de Cartagena was studied, determining the coefficient of minor losses (Kf) caused by 45° and 90° elbows, and three types of valves, using water as the process fluid. The flow rate (Q) was varied, using a valve, between 24, 20, 16, 12 L/min. Darcy's and Bernoulli's theorem methods were used to evaluate friction losses. Were found minimum error percentages of 0.04% and maximum 8.16%; loss coefficients adjusted by minimum squares were obtained with R2 of 0.999, comparing these Kf with the values reported in the plant manual and different authors. It was shown experimentally that the loss coefficient depends on each fitting, allowing the calculation of the theoretical pressure drop and comparing it with the experimental pressure drop, demonstrating that as the flow increases, an increase in pressure drop is generated. With the methodology applied in this research, the aim is to optimize pressure drop tests with fittings, and identify the characteristics of the pipe to obtain an optimum lower loss coefficient value.

Microstructure and Mechanical Performance of Tin-Based Babbitt Alloy Containing Iron Oxide and Silica Nanoparticles

Iron oxide and silica nanoparticles were individually incorporated in tin-based Babbitt alloy and combined to prepare a novel class of nanocomposites for bearing material applications. The route of liquid metallurgy in combination with the stirring technique was adopted to manufacture nanocomposites. Microstructural evolution and mechanical property evaluation were performed by optical and electron microscopy, EDS, hardness, compression, and wear tests. The morphology of the Cu6Sn5 phase was changed from elongated to spherical in the microstructures of nanocomposites. The solitary addition of 0.5 wt% iron oxide nanoparticles improved the hardness and compressive strength but adversely affected the wear properties by increasing the weight loss and friction coefficient value. In contrast, the addition of 0.5 wt% silica nanoparticles could not significantly increase the hardness and compressive strength but it could improve the tribological properties by reducing the weight loss and friction coefficient value. Tin-based Babbitt alloy showed a compressive strength of 89.22 ± 0.50 MPa after the addition of 0.5 wt% iron oxide showing a rise of ~11%. The combined effect of the addition of both types of nanoparticles showed considerable results, i.e., a rise of ~7.9% (86.75 ± 0.68 MPa). The balanced approach of incorporating dual reinforcements of 0.25 wt% iron oxide and 0.25 wt% silica nanoparticles intermediately improved the hardness, compressive strength, and decreased weight loss.

Generation of Defective Few-Layered Graphene Mesostructures by High-Energy Ball Milling and Their Combination with FeSiCuNbB Microwires for Reinforcing Microwave Absorbing Properties

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RLmin) = -21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe73.5Si13.5B9Cu1Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (-53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a fmin tunability is demonstrated, maintaining similar RLmin and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs.

Performance Comparison of Solar Air Heater with Extended Surfaces and Iron Filling

The thermal performance of a solar air heater (SAH) is enhanced by producing air turbulence. The air turbulence is created by using either extended surface or iron filing between the black colour absorber plate and glass of the SAH. In this article, the thermal performance of a SAH in the case of without fins and with fins at a different location is compared with the SAH using an iron filling. The value of the overall heat loss coefficient in the case of iron filling is 2.1 W/m2K. The average thermal efficiency of the iron filling condition is 65.14%. The additional arrangement to increase the heat transfer also increases the pressure drop which leads to higher power consumption. Results show the thermal efficiency of SAH using iron filling is found best followed by fin arrangement above, below the absorber plate, and without fin.

Effects of the addition of high‐temperature water on the bubble structure, rheological properties, and sensory characteristics of gluten‐free rice flour bread

This study investigated the effect of hot water on the rheological properties of the batter, bubble structure, and sensory properties of the bread. We focused on the thickening effect of starch gelatinization and developed a method to produce gluten-free rice flour bread without additives by increasing the temperature of the water used in the production of gluten-free rice flour bread. Hot water at 50–80°C was more effective than 5°C in improving bubble number and bubble size. In batters prepared using water at 68 and 70°C, which had excellent bubble structure, the frequency-dependent fluctuations of the storage and loss moduli were smaller, while the loss coefficient values were larger. The batters showed more favorable sensory qualities at higher temperatures than the cold-water batters. Appropriate temperature control of the water added during batter preparation can enable easier and cost-effective preparation of high-quality gluten-free rice flour bread. Novelty impact statement Appropriate temperature control of the water added during batter preparation improved the quality of gluten-free rice flour bread. Batter prepared with water at 68 and 70°C improved rheological properties, bubble structure, and sensory properties significantly.

NUMERICAL STUDY OF THE BALANCE OF KINETIC ENERGY LOSSES IN THE FLOW PART OF A LOW-CONSUMPTION INFLOW TURBINE

The development of marine power engineering and automation, due to qualitative and quantitative changes by a significant increase in the capacity of modern power plants is considered in the paper. The object of this study is the flow part of a low-consumption inflow turbine, the subject of the study is the loss of kinetic energy in the stage of a low-consumption inflow turbine. The method of investigation is numerical simulation of gas flow using computational gas dynamics; the purpose of the study is to compare the values of kinetic energy loss coefficients in the nozzle diaphragm, impeller and output velocity losses obtained during physical and numerical experiments. The main objective of the study is to compare the values of kinetic energy loss coefficients in the turbine stage obtained during a physical experiment with the results of a numerical experiment. It is noted that low-consumption turbines are characterized by small dimensions, which do not allow to fully carrying out a physical experiment. A balance of losses of a low-consumption inflow turbine is performed in the study. A good convergence of the loss coefficients values obtained by the numerical method with the results of the physical experiment has been established. Conclusions about the possibility of applying numerical modeling for identical types of turbine stages are made.

Computational Fluid Dynamics Modeling of a Pressurized Water Reactor Fuel Assembly to Estimate Loss Coefficients in Support of Subchannel Thermalhydraulics Modeling of Pressurized Water Reactor Small Modular Reactors With Advanced Fuels

Abstract Pressure loss coefficients are generally required by subchannel and system thermalhydraulics codes. These coefficients are not readily available for small modular reactors (SMRs) featuring nonconventional designs and novel coolants. In this study, the pressure loss coefficients were obtained using three-dimensional (3D) computational fluid dynamics (CFD) modeling for an advanced water-cooled reactor. A representative light water fuel assembly used in the Organization for Economic Co-operation and Development (OECD)/National Research Council Canada (NRC) pressurized water reactor subchannel and bundle tests (PSBT) benchmark was selected for CFD modeling and simulation under various working conditions. The fuel assembly includes three types of pressurized water reactor (PWR) spacer grids: simple grid (SG), nonmixing vane grid (NMVG), and mixing vane grid (MVG). Turbulent flow through subchannels of both nonheated and heated rod bundles was simulated to predict recoverable and nonrecoverable pressure distribution along the length of the bundle. It was observed that vortices were generated at the tips of spacer grids, affecting the cross-flow in subchannels significantly. The estimated pressure loss coefficients were found to be influenced by the flow conditions (Reynolds number or the upstream flow history) and spacer grid configuration. Pressure loss coefficient values ranged from 1.14 to 1.80, depending on the spacer grid type, design, and flow conditions. The CFD method used in this study was demonstrated to have the potential to generate input parameters required for the subchannel analysis and optimization of fuel assembly designs and serve as a surrogate for empirical correlations.

Effect of Nitriding Process on Wear Behavior of Dual Phase (Ferrite+Martensite) Ductile Cast Iron

In this study, it was aimed to improve the surface hardness by applying gas nitriding treatment to dual-phase ductile cast iron and to produce ductile cast irons with a good strength-ductility combination. Thus, it has been tried to develop a ductile cast iron with high wear resistance, strength, and ductility. Ductile cast iron specimens with a dual-phase microstructure consisting of ferrite + martensite were produced by oil quenching at 70 °C after intercritical austenitizing at 800 ⁰C in the ferrite + austenite zone. Instead of the tempering process, nitriding treatment was applied to the dual-phase ductile cast iron specimens at 560 °C for 540 minutes. The tempering process required to be applied to the martensitic structure was also performed by the nitriding process and a hard 10 µm thick nitride layer was obtained on the surface. Optical microscope and XRD analysis were performed for microstructural characterization of nitrided dual-phase ductile cast iron specimens. The wear properties were tested with a tribometer. For comparison reasons, microstructural characterization and wear tests were also performed on non-nitrided dual-phase ductile cast iron. In ductile cast iron, microstructures consist of a hard nitride layer (10 µm white layer) on the surface and a ferrite + tempered martensite (43% martensite volume fraction) structure in the center can be produced by oil quenching from intercritical austenitizing and nitriding treatment. Surface hardness of 510 HV in nitrided dual-phase ductile cast iron, 193 HV in dual-phase ductile cast iron, and 353 HV in austempered KGDD were obtained. The lowest weight loss and coefficient of friction were obtained in nitrided dual-phase ductile cast iron. The highest weight loss and friction coefficient values with wear were obtained in dual-phase ductile cast iron. The wear resistance of nitrided dual-phase ductile cast iron is 2 times higher than that of dual-phase ductile cast iron and austempered ductile cast iron.

A spanwise loss model for axial compressor stator based on machine learning

In the early stage of aircraft engine design, the through-flow method is an important tool for designers. The accuracy of the through-flow method depends heavily on the accuracy of the loss model. However, most existing models cannot (or cannot well) provide the spanwise loss distribution. To construct an effective spanwise loss model, both turbomachinery knowledge and machine learning skills were used in this paper. A large number of numerical simulations were carried out to build a database containing more than 1000 compressor cascade numerical samples. Secondary flow intensity was introduced as the independent variable to carry out feature engineering. A model containing a selector based on support vector machine regression and estimators based on K-nearest neighbor regression was constructed. Numerical test set and design data of two former high-pressure core compressors were used for validation. Results suggest that the spanwise loss model show good consistency with both numerical test set and data of two former compressors. It can reflect the influence of secondary flow and can also predict both value and trend of total pressure loss coefficient well, with mean absolute error general around or less than 1% and R2 (coefficient of determination) more than 0.8 on the test set. Especially when dealing with loss coefficient at mid-span position, the model shows even better performance, with R2 over 0.97 on the test set. And the selector of the model can well classify the samples, predict the intensity of secondary flow and help estimators to capture the phenomenon that end-wall secondary flow extends to the mid-span.

Thermal Loss Analysis of a Flat Plate Solar Collector Using Numerical Simulation

In this paper, we studied theoretically and numerically heated losses of a flat solar collector to model the solar water heating system for the Kazakhstan climate condition. For different climatic zones with a growing cost for energy or lack of central heating systems, promising is to find ways to improve the energy efficiency of the solar system. The mathematical model (based on ordinary differential equation) simulated the solar system work process under different conditions. To bridge the modeling and real values results, we studied the important physical parameters such as loss coefficient, Nu, Ra, and Pr values. They impacted the efficiency of flat solar collectors and heat losses of the system. The developed mathematical models, the design and composition of the software and hardware complex, and automated control and monitoring systems allow solar hot water heating systems to increase the energy efficiency of life support systems and heat supply of buildings by reducing energy consumption for heat supply. The simulation result showed that during the daytime, the temperature of water in the collector is 70°C; the storage of heated water since heated water is cooled at night. We defined that a work period of the system can be extended with high efficiency (April–October) for Almaty region.

Thermal performance assessment of a cylindrical box solar cooker fitted with decahedron outer reflector

One of the important issues humankind globally faces in recent years is the scarcity of non-renewable energy resources. Solar energy is considered safe and renewable, which can fulfil the demand and supply chain requirements. Solar box cookers (SBCs) are popular in domestic cooking due to their ease of use and handling. The prime objective of the present work is to develop and test the performance of a cylindrical SBC fitted with decahedron-shaped reflector (CSBC-FDR). The CSBC is designed using minimum entropy generation (MEG) method. Through experiments, we observed that absorber plate attains peak temperature of about 138°C–150°C with the aid of decahedron reflector. The first figure of merit (F1) is found to be 0.13, indicating better optical efficiency and low heat loss coefficient for the SBC. The second figure of merit (F2) is obtained as 0.39, which indicates good heat exchange efficiency (F') and less heat capacity for cooker's interior. The average energy efficiency, exergy efficiency, and standardized cooking power values are 21.93%, 3.04%, and 25.28W, respectively. These results show that the present CSBC-FDR is able to cook food in a shorter period with better efficiency. The experimental and numerical values of overall heat loss coefficient of the developed SBC are in close agreement. The experimentally assessed performance parameters reveal superior performance of the present cylindrical SBC in comparison with many conventional rectangular and trapezoidal box solar cookers.

Numerical study of swirling flow in a steam generating element model with double-sided heating

The paper is devoted to numerical modelling of the swirling flow in an annular channel with an inner twisted pipe. The computational model is designed. The technique of swirling flow calculation is tested for CFD packages LOGOS and ANSYS CFX. The velocity and pressure calculated fields are obtained. Experimental and calculated velocity profiles over the channel cross section are presented. The loss coefficient values is obtained. Experimental and calculated comparison of results is made.

Numerical and Experimental Approaches to Estimate Discharge Coefficients and Energy Loss Coefficients in Pressurized Grated Inlets

Numerical models concerning inlet systems are run to assess the hydraulic performance of existing or new systems and estimate the flow interchanges between the surface overland and sewer flows. In most programs, these interactions are modelled using the orifice equation, with estimated discharge coefficients around 0.6. In this paper, discharge values and energy loss coefficients for several pressurized grated inlets were obtained by experimental and numerical approaches and compared. To achieve these goals, a numerical model replicating several experimental tests carried out at the hydraulic laboratory of Universitat Politècnica de Catalunya (UPC) was produced using a CFD model (Flow 3D). This numerical model was found to be highly sensitive to the mesh size used; however, it was able to accurately simulate the experimental processes. The comparison considered different combinations of pressurized flow though the grate, between 10 to 50 l/s, and different longitudinal gradients. The experimental discharge coefficient was found to increase with surcharging flowrate (ranging from 0.14 and 0.41), whereas the longitudinal gradient was found to have no effect. The discharge coefficients obtained in this study show that the standard 0.6 value commonly used by practitioners should be revised to a range between 0.14 to 0.41, depending on circulating flow and inlet type. In addition, the loss coefficient values range from 0.25 to 3.41.

Pressure Drop Analysis in a Pin Type Mini Channel

The mini channel is used widely in industrial applications. The application includes a heat exchanger device, as a part of a cooling system or as a reactant transport channel. However, unlike the pressure drop determination of a piping network, where the loss coefficient values for the bends and fittings are available, similar cannot be done for the mini channel. The loss coefficient values for the channel are rarely determined and reported. The aim of this study is to propose a correlation for the prediction of total pressure drop in a mini channel resulting from the loss coefficient. The results were compared against a numerical simulation. A 42 mm x 50 mm pin type mini channel was used as the sample of the study. The fluid was hydrogen. The flow regime was kept as laminar. The numerical simulation was performed on the whole active area. The correlation was calculated using the loss coefficient values of bends that were determined beforehand. Three correlations were proposed. Statistical values were used as the comparison parameters. Based on the results, an almost similar pressure drop was predicted by correlation III (diff. mean ± SD = 0.005 ± 0.006 kPa). The correlation I and correlation II were not able to predict the expected results at all. The results were from a low Reynolds (range of Re < 200) number. In general, the correlation proposed successfully predicted the pressure drop in a pin-type mini channel using the loss coefficient value of the individual bends.

Iterative calculation of local head loss coefficient of emitters in lateral lines

ABSTRACT This study aimed to iteratively set the local head loss coefficient of the Naan® micro-sprinkler, model 7110 Hadar, installed in a lateral irrigation line. To evaluate the total head loss along the lateral line, tests were performed using a rigid PVC pipe with an inner diameter of 15.8 mm, 12 m in length, and 24 micro-sprinklers inserted along the pipe, regularly spaced 0.5 m. In the tests carried out for four micro-sprinkler nozzle diameters (0.9, 1.0, 1.1, and 1.2 mm) and six inlet pressure head values (5, 10, 15, 20, 25, and 30 m) in the line, the pressure head difference between inlet and outlet in the pipe and the discharge of each emitter along the pipe were measured. The head loss computation was performed by the step-by-step procedure, starting from the downstream end to the upstream end of the line; since varying the local head loss coefficient values iteratively, the total head loss measured in the tests was equal to the calculated. For the different working conditions of the inlet pressure head and the micro-sprinkler nozzle diameter, the local head loss coefficient had values from 0.051 to 0.169. Relating the discharge values measured and estimated along the lateral line, the confidence coefficient of 0.9991 was verified, and the calculation procedure was considered optimal.