Heat Transfer: Volume 3最新文献_第2页

Analysis of Fin-Tube Evaporator Performance With Limited Experimental Data Using Artificial Neural Networks 有限实验数据下翅片管蒸发器性能的人工神经网络分析

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1466

A. Pacheco-Vega, M. Sen, R. McClain

{"title":"Analysis of Fin-Tube Evaporator Performance With Limited Experimental Data Using Artificial Neural Networks","authors":"A. Pacheco-Vega, M. Sen, R. McClain","doi":"10.1115/imece2000-1466","DOIUrl":"https://doi.org/10.1115/imece2000-1466","url":null,"abstract":"\u0000 In the current study we consider the problem of accuracy in heat rate estimations from artificial neural network models of heat exchangers used for refrigeration applications. The network configuration is of the feedforward type with a sigmoid activation function and a backpropagation algorithm. Limited experimental measurements from a manufacturer are used to show the capability of the neural network technique in modeling the heat transfer in these systems. Results from this exercise show that a well-trained network correlates the data with errors of the same order as the uncertainty of the measurements. It is also shown that the number and distribution of the training data are linked to the performance of the network when estimating the heat rates under different operating conditions, and that networks trained from few tests may give large errors. A methodology based on the cross-validation technique is presented to find regions where not enough data are available to construct a reliable neural network. The results from three tests show that the proposed methodology gives an upper bound of the estimated error in the heat rates.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122076848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

An Economical Method for Artificial Neural Network Process Modeling by the Model-Modifier Approach 基于模型修正器的人工神经网络过程经济建模方法

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1471

S. Bhatikar

引用次数: 0

Neural Network Modeling of Molecular Beam Epitaxy 分子束外延的神经网络建模

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1470

Kyeong K. Lee, T. Brown, G. Dagnall, R. Bicknell-Tassius, A. Brown, G. May

{"title":"Neural Network Modeling of Molecular Beam Epitaxy","authors":"Kyeong K. Lee, T. Brown, G. Dagnall, R. Bicknell-Tassius, A. Brown, G. May","doi":"10.1115/imece2000-1470","DOIUrl":"https://doi.org/10.1115/imece2000-1470","url":null,"abstract":"\u0000 This paper presents the systematic characterization of the molecular beam epitaxy (MBE) process to quantitatively model the effects of process conditions on film qualities. A five-layer, undoped AlGaAs and InGaAs single quantum well structure grown on a GaAs substrate is designed and fabricated. Six input factors (time and temperature for oxide removal, substrate temperatures for AlGaAs and InGaAs layer growth, beam equivalent pressure of the As source and quantum well interrupt time) are examined by means of a fractional factorial experiment. Defect density, x-ray diffraction, and photoluminescence are characterized by a static response model developed by training back-propagation neural networks. In addition, two novel approaches for characterizing reflection high-energy electron diffraction (RHEED) signals used in the real-time monitoring of MBE are developed. In the first technique, principal component analysis is used to reduce the dimensionality of the RHEED data set, and the reduced RHEED data set is used to train neural nets to model the process responses. A second technique uses neural nets to model RHEED intensity signals as time series, and matches specific RHEED patterns to ambient process conditions. In each case, the neural process models exhibit good agreement with experimental results.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117354831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Thermal Modeling for the Consolidation Process of Thermoplastic Composite Filament Winding 热塑性复合材料长丝缠绕固结过程的热建模

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1494

A. Loos, X. Song

{"title":"Thermal Modeling for the Consolidation Process of Thermoplastic Composite Filament Winding","authors":"A. Loos, X. Song","doi":"10.1115/imece2000-1494","DOIUrl":"https://doi.org/10.1115/imece2000-1494","url":null,"abstract":"\u0000 The quality of thermoplastic composites depends on the thermal history during processing. Therefore it is important to determine the temperature distribution in the composite during the fabrication process. The objective of this investigation was to develop a comprehensive thermal model of the thermoplastic filament winding process. The model was developed in two parts to calculate the temperature profiles in the towpreg and the composite substrate. A finite element heat transfer analysis for the composite-mandrel assembly was formulated in the polar coordinate system, which facilitates the description of the geometry and the boundary conditions. A four-node ‘sector element’ is used to describe the domain of interest. Sector elements were selected to give a better representation of the curved boundary shape which should improve accuracy with fewer elements compared to a finite element solution in the Cartesian-coordinate system. The second thermal analysis was a Cartesian coordinate, finite element model of the towpreg as it enters the nippoint. The results show that the calculated temperature distribution in the composite substrate compared well with temperature data measured during winding and consolidation. The analysis also agreed with the experimental observation that the melt region is formed on the surface of the incoming towpreg in the nippoint and not on the substrate.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115649320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Mass/Heat Transfer in Rotating Dimpled Turbine-Blade Coolant Passages 旋转凹痕涡轮-叶片冷却剂通道内的质量/传热

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1460

S. Acharya, Fuguo Zhou

引用次数: 0

Modeling of Moving Breakdown by Femtosecond Laser Pulses in Dielectrics 飞秒激光脉冲在介质中运动击穿的建模

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1476

C. Fan, J. Longtin

{"title":"Modeling of Moving Breakdown by Femtosecond Laser Pulses in Dielectrics","authors":"C. Fan, J. Longtin","doi":"10.1115/imece2000-1476","DOIUrl":"https://doi.org/10.1115/imece2000-1476","url":null,"abstract":"\u0000 Laser ablation is becoming increasingly important in the fields of micromaching, thin film formation, and bioengineering applications. In laser ablation, the ablation rates and feature quality strongly depend on the size of the breakdown region in the material. This region is characterized by a high density of free electrons, which absorb a large fraction of energy from the laser pulse that results in material vaporization in solids or liquids. For nanosecond- and picosecond pulses, the breakdown region tends to form near the beam focus and then expand back along the beam path toward the laser; this phenomenon is called moving breakdown. For femtosecond pulses, however, breakdown begins up the beam path and then propagates toward the focal point. A moving breakdown model presented by Docchio et al. (1988a) successfully explains and predicts the time-dependent breakdown region in the nanosecond regime, however it does not adequately describe propagation of the breakdown region at pico- and femtosecond time scales. In the present work, a modified moving breakdown model is proposed that includes the pulse propagation and small spatial extent of ultrafast laser pulses. This revised model shows that pulse propagation becomes significant for pulsewidths less than 10 picoseconds. The new model characterizes the pulse behavior as it interacts with a material within the focal volume in both solids and liquids. The model may also be useful in estimating the time- and space-resolved electron density in the interaction volume, the breakdown threshold of a material, shielding effectiveness, energy deposition, and the temperature increase in the material.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126986415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Implementation Issues in Artificial Neural Network Based Thermal Analysis 基于人工神经网络的热分析实现问题

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1465

K. T. Yang

{"title":"Implementation Issues in Artificial Neural Network Based Thermal Analysis","authors":"K. T. Yang","doi":"10.1115/imece2000-1465","DOIUrl":"https://doi.org/10.1115/imece2000-1465","url":null,"abstract":"\u0000 It is now known the generally it can be demonstrated that artificial neural network (ANN), particularly the fully-connected feedforward configuration with backward propagation error-correction routine, can be a rather effective and accurate tool to correlate performance data of thermal devices such as heat exchangers (Sen and Yang, 2000; Kalogirou, 1999). Good examples are the recent demonstrations for the compact fin-tube heat exchangers (Diaz et al., 1999a; Yang et al., 2000; Pacheco-Vega et al., 1999) including those with complex geometries and also two-phase evaporators (Pacheco-Vega et al., 2000) as well as the dynamic modeling of such heat exchangers and their adaptive control (Diaz et al., 1999b; Diaz et al., 2000). Unfortunately, despite such successes, there are still implementation issues of the ANN analysis which lead to uncertainties in its applications and the achieved results. The present paper discusses such issues and the current practices in dealing with them. Those that will be discussed include the number of hidden layers, the number of nodes in each hidden layer, the range within which the input-output data are normalized, the initial assignment of weights and biases, the selection of training data sets, and the training rate. As will be shown, the specific choices are by no means trivial, and yet are rather important in achieving good ANN results in any given application. Since there are no general sound theoretical basis for such choices at the present time, past experience and numerical experimentation are often the best guides. However, many of these choices and issues relating to them involve optimization. As a result. Some of the existing optimization algorithms may prove to be useful and highly desirable in this regard. The current on-going research to provide some rational basis in these issues will also be discussed. Finally, it will also be mentioned that successfully implemented ANNs have many additional uses in practice. Examples include parameter sensitivity analysis, training, design of new experiments, and clustering of data sets.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125152651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Heat Transfer on a Film Cooled Inlet Guide Vane 薄膜冷却进口导叶的传热

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1459

Marie-Louise Holmer, L. Eriksson, B. Sundén

{"title":"Heat Transfer on a Film Cooled Inlet Guide Vane","authors":"Marie-Louise Holmer, L. Eriksson, B. Sundén","doi":"10.1115/imece2000-1459","DOIUrl":"https://doi.org/10.1115/imece2000-1459","url":null,"abstract":"\u0000 The steady flow and temperature fields around a film cooled inlet guide vane are determined numerically by a CFD method. In particular the outer surface temperatures and heat transfer coefficient distributions are calculated. Static pressure distributions are also presented. The film cooling is achieved by 10 rows of film cooling holes. The computed results are compared with experimental data.\u0000 The governing equations are solved by a 3D finite-volume Navier-Stokes solver. The low Reynolds number version of the k-ω turbulence model by Wilcox is implemented to enable calculations of turbulent flow cases. A realizability constraint is applied to reduce the generation of unphysical turbulent kinetic energy, particularly close to the leading edge.\u0000 To handle the film cooling process a special procedure is used. An injection model was implemented in the computer code. This injection model adds the mass flow rate passing through the film cooling holes to the main flow as source terms in the equations for mass, momentum, energy and turbulent kinetic energy.\u0000 The grid used in the calculations is block-structured, and the total number of grid points is around 250,000.\u0000 In a related investigation for the same vane geometry but considering pure convective heat transfer, the authors have investigated the importance of the wall thermal boundary condition. Based on this a conjugate heat transfer approach was applied in this paper. The conjugate heat transfer condition means that the heat transfer coefficient distribution is prescribed on the inner surface of the vane and also the wall thickness and thermal conductivity of the vane material are prescribed. The vane outer surface temperature is then found as part of the numerical solution.\u0000 Some essential parameters in the injection model were varied and the calculated results for the vane outer surface temperature were found to compare favourably with measurements. The static pressure distribution on the vane surface agrees well with experiments. The Mach number distribution provides information of the flow field.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130044501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Simulation of Thermal Plasma Spraying of Partially Molten Ceramics: Effect of Carrier Gas on Particle Deposition and Phase Change Phenomena 部分熔融陶瓷热等离子喷涂的模拟:载气对颗粒沉积和相变现象的影响

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/1.1338117

I. Ahmed, T. Bergman

引用次数: 30

Numerical Simulation of Dendritic Solidification 枝晶凝固的数值模拟

Heat Transfer: Volume 3 Pub Date : 2000-11-05 DOI: 10.1115/imece2000-1481

J. Jung, M. M. Chen

{"title":"Numerical Simulation of Dendritic Solidification","authors":"J. Jung, M. M. Chen","doi":"10.1115/imece2000-1481","DOIUrl":"https://doi.org/10.1115/imece2000-1481","url":null,"abstract":"\u0000 It is well known that the dendritic microstructure of alloys is a consequence of morphological instability of the solidification process, which is a result of the coupling of heat and mass transfer with the composition-dependent phase equilibrium condition mediated by the surface energy. There have been many numerical simulations of dendritic solidification. However, many successful simulations of dendritic growth have used non-discrete front tracking method such as artificial source method or phase field method, with demonstrably first order accuracy. Many also found it necessary to continuously inject random noise during simulation. The continuous injection of random noise raises the suspicion that the numerical schemes used may be overly dissipative. The noise is apparently capable of creating nonuniform solidification, but not sufficient to ensure growth with a clear dendritic pattern. In the present study, to rule out the numerical diffusivity as a cause of the damping of dendritic perturbations, artificial perturbations are either not used, or injected only as initial conditions. Under the unstable solidification mode, the initial perturbation triggers the onset of interface instability. Computations were performed for both sub-cooled pure material as well as directional solidification of alloys. The successful simulation of dendritic solidification without the intentional injection of random noise provided evidence that the present method has less numerical diffusion than many existing front tracking methods.","PeriodicalId":306962,"journal":{"name":"Heat Transfer: Volume 3","volume":"216 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122369749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0