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Magnetocaloric effect of LaFe_(11.35)Co_(0.6)Si_(1.05) alloy

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Rare Metals 2022年第5期41卷 1563-1569页

作者： piotr Gebara Institute of Physics Czestochowa University of Technology42-200 CzestochowaPoland

The aim of the present paper was to study the large magnetocaloric effect observed in LaFe_(11.35)Co_(0.6)Si_(1.05)alloy. X-ray diffraction(XRD) result reveals a coexistence of two crystalline phases: a dominant La(Fe,Si)_(13)-type and a minor a-Fe(Co,Si). It is confirmed by the Mössbauer spectroscopy and microstructural observations accompanied by an energy-dispersive spectroscopy(EDS) analysis. The value of the magnetic entropy changes(|S_(M)|) in the vicinity of the Curie temperature(TC= 268 K) was calculated using thermomagnetic Maxwell relation, and it equals to 21.4 J·kg^(-1)·K^(-1) under the change in an external magnetic field of μ_(0)ΔH = 3T. The investigation of magnetic phase transition was carried out using the Landau theory, an analysis of the field dependences of the magnetic entropy change and universal scaling curve, revealing the second order of phase transition in the studied material.

关键词： X-ray diffraction M?ssbauer spectroscopy Magnetocaloric effect

Solution of Inverse Heat Conduction Problem using the Tikhonov Regulariza-tion Method

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Journal of Thermal Science 2017年第1期26卷 60-65页

作者： piotr Duda Institute of Thermal Power Engineering Cracow University of Technology al. Jana Pawla Ⅱ 37 31-864 Krak6w Poland

It is hard to solve ill-posed problems, as calculated temperatures are very sensitive to errors made while calculating "measured" temperatures or performing real-time measurements. The errors can create temperature oscillation, which can be the cause of an unstable solution. In order to overcome such difficulties, a variety of techniques have been proposed in literature, including regularization, future time steps and smoothing digital filters. In this paper, the Tikhonov regularization is applied to stabilize the solution of the inverse heat conduction problem. The impact on the inverse solution stability and accuracy is demonstrated.

关键词： inverse problems, heat conduction, identification

Effect of TiB_2 Particles on the Tribological Properties of Stainless Steel Matrix Composites

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 12-18页

作者： Iwona Sulima piotr Klimczyk piotr Malczewski Institute of Technology Pedagogical Universityul.Podchorazych 230-084 KrakwPoland Institute of Advanced Manufacturing Technology ul.Wroclawska 37A30-011 KrakwPoland

The AISI316L stainless steel composites reinforced with 2, 4, 6, and 8 vol% titanium diboride （TiB2） particles were sintered by the high pressure-high temperature method. Ball-on-disk method was carried out to study wear behavior of the composites. Tests were carried out at room temperature. The TiB2 particles improved the hardness and tribological properties of the composites. The friction coefficient of the composites decreased with the increasing content of TiB2. The reduction of the wear rate with the increasing of the content of TiB2 particles in the steel matrix was also observed. It is demonstrated that the friction coefficient of composites with the same content of TiB2 particles depend on the sintering conditions.

关键词： Metal matrix composites Titanium diboride Friction coefficient Bail-on-disk method

Finite Element Method Formulation in Polar Coordinates for Transient Heat Conduction Problems

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Journal of Thermal Science 2016年第2期25卷 188-194页

作者： piotr Duda Institute of Thermal Power Engineering Faculty of Mechanical Engineering Cracow University of Technology Al.

The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.

关键词： FEM polar coordinate system numerical methods transient heat conduction power boilers

New View of Ping-Pong Protocol Security

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Chinese Physics Letters 2012年第1期29卷 11-13页

作者： piotr Zawadzki Institute of Electronics Silesian University of TechnologyGliwicePoland

The ping-pong protocol offers confidential transmission of classic information without a prior key *** is believed that it is quasi secure in lossless quantum *** doubts related to the analysis paradigm which has been... 详细信息

关键词： ping Ping doubt

Flow Structure and Heat Exchange Analysis in Internal Cooling Channel of Gas Turbine Blade

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Journal of Thermal Science 2016年第4期25卷 336-341页

作者： Ryszard Szwaba piotr Kaczynski piotr Doerffer Janusz Telega Institute of Fluid-Flow Machinery Polish Academy of Sciences(IMP PAN)

This paper presents the study of the flow structure and heat transfer,and also their correlations on the four walls of a radial cooling passage model of a gas turbine *** investigations focus on heat transfer and aerodynamic measurements in the channel,which is an accurate representation of the configuration used in *** for the heat transfer coefficient and the pressure drop used in the design of radial cooling passages are often developed from simplified *** is important to note that real engine passages do not have perfect rectangular cross sections,but include coiner fillet,ribs with fillet radii and special ***,this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which possesses very realistic features.

关键词： cooling internal blade channels heat exchange transient liquid crystal method

Selection of the Relevant Turbulence Model in a CFD Simulation of a Flow Disturbed by Hydraulic Elbow--Comparative Analysis of the Simulation with Measurements Results Obtained by the Ultrasonic Flowmeter

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Journal of Thermal Science 2018年第5期27卷 413-420页

作者： PIECHOTA piotr SYNOWIEC piotr ANDRUSZKIEWICZ Artur WEDRYCHOWICZ Wieslaw Faculty of Mechanical and Power Engineering Wroclaw University of Science and Technology Wybrzeze Wyspiafiskiego 27 50-370 Wroclaw

The article is an attempt to compile the results of CFD liquid flow simulation through pipeline section containing hydraulic elbow with the results of ultrasonic flow measurements. To carry out the measurements behind the flow disturbing element(hydraulic elbow), an ultrasonic flowmeter with applied head set in accordance with the Z-type system was used. For comparative purposes, a flow simulation for 3 different turbulence models(k-epsilon, SST and SSG) was performed. It was found that with a proper ultrasonic flowmeter heads configurations, it is possible to measure the flow rate disturbed by the hydraulic elbow at any distance from the source of the disturbance. It has to use appropriate correction factor that can be determined by knowing the flow velocity profile equation. Based on comparison of CFD simulation results with experimental data, the accuracy/purposefulness of using individual turbulence models in the case of discussed hydraulic installation was evaluated.

关键词： ultrasonic flowmeter turbulent flow turbulence models CFD simulation measurement error

Control Valve with a Constant Inner Authority Value

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Journal of Thermal Science 2018年第5期27卷 487-495页

作者： MUNIAK Damian piotr Department of Thermal Power Engineering Cracow University of Technology

The aim of the article is to propose the method of designing double regulation control valves used in heating installations, allowing to obtain a constant value of the so-called inner authority and thus the constancy of the valve control characteristic, regardless of the pre-setting value set on the valve. The shape of the valve's regulation characteristics is one of the main factors determining the quality of the quantitative regulation, and thus the stability of the system's operation and overall operating costs. For this reason, the issue discussed in the article is important and can be applied in practical implementations of the valve sizing and the valve selection. The analysis was based on the relations binding the hydraulic resistances occurring inside the control valve, and the corresponding flow factors, using original author's proposal. The experimental verification was performed on a special measuring stand prepared for this purpose, measuring the values of the medium volume flow at a constant differential pressure, and then the results were converted into values of the flow factor, used in the proposed mathematical model. The results confirm the thesis put forward and the proposed mathematical model. High convergence of the results of experimental verification with the proposed mathematical model was obtained.

关键词： control valve valve authority pre-setting heating installation hydraulic balancing

Influence of Internal Channel Geometry of Gas Turbine Blade on Flow Structure and Heat Transfer

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Journal of Thermal Science 2017年第6期26卷 514-522页

作者： Ryszard Szwaba piotr Kaczynski Janusz Telega piotr Doerffer Institute of Fluid-Flow Machinery Polish Academy of Sciences (IMP PAN) Fiszera 14 80-952 Gdansk POLAND

This paper presents the study of the influence of channel geometry on the flow structure and heat transfer, and also their correlations on all the walls of a radial cooling passage model of a gas turbine blade. The investigations focus on the heat transfer and aerodynamic measurements in the channel, which is an accurate representation of the configuration used in aeroengines. Correlations foi： the heat transfer coefficient and the pressure drop used in the design of internal cooling passages are often developed from simplified models. It is important to note that real engine passages do not have perfect rectangular cross sections, but include a comer fillets, ribs with fillet radii and a special orientation. Therefore, this work provides detailed fluid flow and heat transfer data for a model of radial cooling geometry which has very realistic features.

关键词： cooling internal blade channels aerodynamics with heat transfer