P. Dousti, A.A. Ranjbar, M. Famouri and A. Ghaderi
The purpose of this paper is to estimate interfacial heat transfer coefficient (IHTC) in a two‐dimensional solidification based on the particle swarm optimization (PSO) method.
Abstract
Purpose
The purpose of this paper is to estimate interfacial heat transfer coefficient (IHTC) in a two‐dimensional solidification based on the particle swarm optimization (PSO) method.
Design/methodology/approach
The proposed numerical technique is based on the PSO combined with finite different method (FDM) to simultaneously estimate heat transfer coefficient in the metal‐mold interface. In this paper, simulated (noisy and filtered) temperatures are used instead of experimental data. The estimated temperatures are obtained from the direct numerical solution (FDM) of the two‐dimensional solidification model and PSO is applied to minimize a least squares objective function containing estimated and simulated (noisy and filtered) temperatures.
Findings
The accuracy and capability of the PSO are assessed by comparing the estimated and the pre‐selected heat transfer coefficients. The results show that the measurement errors do not considerably affect the accuracy of the estimates. In other words, the proposed method provides a practical and confident prediction in simultaneously estimating the IHTCs.
Research limitations/implications
Future approaches should find the optimal design of case study and then apply the proposed method to achieve the best results.
Practical implications
Applications of the results and the presented method in this paper can be of value in practical applications in parameter estimation for estimating the IHTCS.
Originality/value
An inverse estimation of IHTC in a two‐dimensional solidification has been made based on PSO algorithm for a practical case of Al 5% Wt‐Si.
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Qiang Li, Qinglei Liu, Yujun Wang, Shuo Zhang, Yujing Du, Bin Li and Wei-Wei Xu
The stringent requirements for environmental protection have induced the extensive applications of water-lubricated journal bearings in marine propulsion. The nonlinear dynamic…
Abstract
Purpose
The stringent requirements for environmental protection have induced the extensive applications of water-lubricated journal bearings in marine propulsion. The nonlinear dynamic analysis of multiple grooved water-lubricated bearings (MGWJBs) has not been fully covered so far in the literature. This study aims to conduct the nonlinear dynamic analysis of the instability for MGWJBs.
Design/methodology/approach
An attenuation rate interpolation method is proposed for the determination of the critical instability speed. Based on a structured mesh movement algorithm, the transient hydrodynamic force model of MGWJBs is set up. Furthermore, the parameters’ analysis of nonlinear instability for MGWJBs is conducted. The minimum water film thickness, side leakage, friction torque and power loss of friction are fully analyzed.
Findings
With the increase of speed, the journal orbits come across the steady state equilibrium motion, sub-harmonic motion and limit circle motion successively. At the limit circle motion stage, the orbits are much larger than that of steady state equilibrium and sub-harmonic motion. The critical instability speed increases when the spiral angle decreases or the groove angle increases. The minimum water film thickness peak is at the rotor speed of 4,000 r/min for the MGWJB with Sa = 0°. As rotor speed increases, the side leakage decreases slightly while the friction torque and the power loss of friction increase gradually.
Originality/value
Present research provides a beneficial reference for the dynamic mechanism analysis and design of MGWJBs.
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Qiang Li, Shuo Zhang, Yujun Wang, Wei-Wei Xu, Zengli Wang and Zhenbo Wang
Shear stresses have a considerable influence on the characteristics of lubricants and become significant at high rotating speeds. This study aims to investigate the influences of…
Abstract
Purpose
Shear stresses have a considerable influence on the characteristics of lubricants and become significant at high rotating speeds. This study aims to investigate the influences of shear cavitation (SC) on loading capacity of journal bearings.
Design/methodology/approach
A principal normal stress cavitation criterion based on the stress applied to flowing lubricant in journal bearings is developed and used to investigate SC in journal bearings. A computational fluid dynamic (CFD) model for calculating the loading capacity is established using this criterion. After validation with experimental results, the loading capacity is calculated under different conditions.
Findings
The calculation results indicate that SC intensifies when viscosity, speed and eccentricity increase. Angle of loading capacity with SC is larger than that without SC. The magnitude of loading capacity with SC is smaller than that without SC due to the decrease in the ultimate pressure. In addition, the magnitude difference between the loading capacity with and without SC increases when viscosity, speed and eccentricity increases.
Originality/value
Present research can provide some guidance for calculating the loading capacity when a journal bearing is operating at high speed or with a high viscosity lubricant.
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Dongfang Sun, Jingchun Tang, Xiuping Zhang, Xudong Yuan, Yue Qian, Fangping Ye, Bin Ye and Bin Jiang
The leakage problem caused by machining error, assembly error, wearing and thermal deformation has been the main factor hindering the development of scroll compressor. This paper…
Abstract
Purpose
The leakage problem caused by machining error, assembly error, wearing and thermal deformation has been the main factor hindering the development of scroll compressor. This paper aims to investigate the lubrication characteristics of radial clearance and further optimize the radial clearance, which can reduce the leakage in the tangential direction of the working chamber.
Design/methodology/approach
This paper establishes a model of radial clearance oil film lubrication in scroll compressor. And, the method to solve the Reynolds and energy equations is presented, as well as the dimensionless and discretization by finite element difference method. To verify the established model, performance experiment of scroll compressor for electric vehicle air conditioning system is also carried out.
Findings
Based on the presented model, the temperature field and distribution of the oil film in the radial clearance are analyzed. And the influence of the structural parameter on the radial clearance is further discussed. The optimum radial clearance could be achieved at β = 40°–42°, where the orbiting scroll is in the state of rotary balance. And, the simulation results coincide well with the experimental results.
Originality/value
This work provides an effective model to evaluate the lubrication characteristics of radial clearance in scroll compressor, which can provide guidance for the design of scroll compressor.
Details
Keywords
Xiuwei Li, XingYang Li, Guokun Zhang, Yu Wang, Qinglei Liu and Qiang Li
The purpose of this paper is to investigate the effects of different surface structures, dimensional parameters and cavitation models on the lubrication characteristics of…
Abstract
Purpose
The purpose of this paper is to investigate the effects of different surface structures, dimensional parameters and cavitation models on the lubrication characteristics of water-lubricated journal bearings.
Design/methodology/approach
In this paper, the coupling iteration method of ANSYS and MATLAB is established to calculate the journal orbits of water-lubricated bearing, and the differences between the journal orbits of the smoothed and the textured water-lubricated bearings are compared and analyzed, and the effects of different bearing materials, L/D ratios and clearance ratios on the lubrication performance of water-lubricated bearings are investigated. The effects of different cavitation models on the static equilibrium position and whirling trajectory of water-lubricated bearings are compared.
Findings
The results show that when the surface texture is distributed in the upper bearing or the bearing elastic modulus decreases, the bearing stability increases. Considering shear cavitation and noncondensing gas, the rotor journal orbits amplitude decreases at high speed with low clearance ratio. A water film test rig for water-lubricated bearings is built to measure the full-circle water film pressure of water-lubricated journal bearings, and the experimental results are compared with the simulation results, which are in good agreement.
Originality/value
The findings provide a theoretical basis for optimizing the structure of water-lubricated bearings.
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Keywords
Vishweshwara P.S., Harsha Kumar M.K., N. Gnanasekaran and Arun M.
Many a times, the information about the boundary heat flux is obtained only through inverse approach by locating the thermocouple or temperature sensor in accessible boundary…
Abstract
Purpose
Many a times, the information about the boundary heat flux is obtained only through inverse approach by locating the thermocouple or temperature sensor in accessible boundary. Most of the work reported in literature for the estimation of unknown parameters is based on heat conduction model. Inverse approach using conjugate heat transfer is found inadequate in literature. Therefore, the purpose of the paper is to develop a 3D conjugate heat transfer model without model reduction for the estimation of heat flux and heat transfer coefficient from the measured temperatures.
Design/methodology/approach
A 3 D conjugate fin heat transfer model is solved using commercial software for the known boundary conditions. Navier–Stokes equation is solved to obtain the necessary temperature distribution of the fin. Later, the complete model is replaced with neural network to expedite the computations of the forward problem. For the inverse approach, genetic algorithm (GA) and particle swarm optimization (PSO) are applied to estimate the unknown parameters. Eventually, a hybrid algorithm is proposed by combining PSO with Broyden–Fletcher–Goldfarb–Shanno (BFGS) method that outperforms GA and PSO.
Findings
The authors demonstrate that the evolutionary algorithms can be used to obtain accurate results from simulated measurements. Efficacy of the hybrid algorithm is established using real time measurements. The hybrid algorithm (PSO-BFGS) is more efficient in the estimation of unknown parameters for experimentally measured temperature data compared to GA and PSO algorithms.
Originality/value
Surrogate model using ANN based on computational fluid dynamics simulations and in-house steady state fin experiments to estimate the heat flux and heat transfer coefficient separately using GA, PSO and PSO-BFGS.
Ajit Kumar Parwani, Prabal Talukdar and P.M.V. Subbarao
The purpose of this paper is to develop a numerical model for estimating the unknown boundary heat flux in a parallel plate channel for the case of a hydrodynamically and…
Abstract
Purpose
The purpose of this paper is to develop a numerical model for estimating the unknown boundary heat flux in a parallel plate channel for the case of a hydrodynamically and thermally developing laminar flow.
Design/methodology/approach
The conjugate gradient method (CGM) is used to solve the inverse problem. The momentum equations are solved using an in-house computational fluid dynamics (CFD) source code. The energy equations along with the adjoint and sensitivity equations are solved using the finite volume method.
Findings
The effects of number of measurements, distribution of measurements and functional form of unknown flux on the accuracy of estimations are investigated in this work. The prediction of boundary flux by the present algorithm is found to be quite reasonable.
Originality/value
It is noticed from the literature review that study of inverse problem with hydrodynamically developing flow has not received sufficient attention despite its practical importance. In the present work, a hydrodynamically and thermally developing flow between two parallel plates is considered and unknown transient boundary heat flux at the upper plate of a parallel plate channel is estimated using CGM.
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Nadia Catenazzi and Lorenzo Sommaruga
Over the last few decades, technological development has had a major impact on libraries. Nowadays many libraries use electronic support for operations such as acquiring and…
Abstract
Over the last few decades, technological development has had a major impact on libraries. Nowadays many libraries use electronic support for operations such as acquiring and cataloguing material, searching, and retrieval. Information technology is an aid for both the librarian, in order to organise the material, and for the user in order to gain access to the broad storehouse. Information is still physically stored in the library. This represents an intermediate step in the process of library automation which leads to a completely electronic library, where a timely provision of selected materials to individuals, when and where they need them, is guaranteed. An electronic library houses different kinds of electronic information: in addition to text, there is an extensive use of multimedia collections, such as sound archives, video material, slide collections and so on. The electronic library is the result of complex changes which have affected and which still affect the publishing world (Barker 1994; Clement 1994; Raitt 1993).
Electronic document delivery is a concept which promises to solve end‐user problems in retrieving the primary information referenced to in bibliographical databases. This article…
Abstract
Electronic document delivery is a concept which promises to solve end‐user problems in retrieving the primary information referenced to in bibliographical databases. This article describes an approach to electronic document delivery which gradually evolved at Tilburg University over the past two years, leading to the development of a system called Ariadne. First of all, a pragmatic description of electronic document delivery is developed as a basis for a generation model of electronic document delivery systems. This model is illustrated with short references to existing systems and leads to the identification of global requirements for an Ariadne‐like system. Special attention will be paid to existing and developing standards in this field, notably the work of the Group on Electronic Document Interchange (GEDI). The remainder of the article addresses the general model of Ariadne, currently under development at Tilburg University. The article concludes with some strategic issues for libraries and publishers in this field, and a short look into the future.
Davood Rostamy and Kobra Karimi
The purpose of this paper is to introduce a novel approach based on the high-order matrix derivative of the Bernstein basis and collocation method and its employment to solve an…
Abstract
Purpose
The purpose of this paper is to introduce a novel approach based on the high-order matrix derivative of the Bernstein basis and collocation method and its employment to solve an interesting and ill-posed model in the heat conduction problems, homogeneous backward heat conduction problem (BHCP).
Design/methodology/approach
By using the properties of the Bernstein polynomials the problems are reduced to an ill-conditioned linear system of equations. To overcome the unstability of the standard methods for solving the system of equations an efficient technique based on the Tikhonov regularization technique with GCV function method is used for solving the ill-condition system.
Findings
The presented numerical results through table and figures demonstrate the validity and applicability and accuracy of the technique.
Originality/value
A novel method based on the high-order matrix derivative of the Bernstein basis and collocation method is developed and well-used to obtain the numerical solutions of an interesting and ill-posed model in heat conduction problems, homogeneous BHCP with high accuracy.