Modelling of Convective Melt Flow and Interface Shape in Commercial Bridgman-Stockbarger Growth of CdZnTe

2000 ◽  
Author(s):  
Toby D. Rule ◽  
Ben Q. Li ◽  
Kelvin G. Lynn
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Solute Transport ◽  
Latent Heat ◽  
Thermal Stresses ◽  
Radiation Detector ◽  
Time History ◽  
High Quality ◽  
Melt Convection ◽  
The Impact

Abstract CdZnTe single crystals for radiation detector and IR substrate applications must be of high quality and controlled purity. The growth of such crystals from a melt is very difficult due to the low thermal conductivity and high latent heat of the material, and the ease with which dislocations, twins and precipitates are introduced during crystal growth. These defects may be related to solute transport phenomena and thermal stresses associated with the solidification process. As a result, production of high quality material requires excellent thermal control during the entire growth process. A comprehensive model is being developed to account for radiation and conduction within the furnace, thermal coupling between the furnace and growth crucible, and finally the thermal stress fields within the growing crystal which result from the thermal conditions imposed on the crucible. As part of this effort, the present work examines the heat transfer and fluid flow within the crucible, using thermal boundary conditions obtained from experimental measurements. The 2-D axisymetric numerical model uses the deforming finite element method, with allowance made for melt convection, solidification with latent heat release and conjugate heat transfer between the solid material and the melt. Results are presented for several stages of growth, including a time-history of the solid-liquid interface (1365 K isotherm). The impact of melt convection, thermal end conditions and furnace temperature gradient on the growth interface is evaluated. Future work will extend the present model to include radiation exchange within the furnace, and a transient analysis for studying solute transport and thermal stress.

Thermal Stress Analysis of Nonuniformly Heated Cylindrical Shell and Its Application to a Steam Generator Membrane Wall

1968 ◽  
Vol 90 (1) ◽  
pp. 73-81 ◽  
Author(s):  
P. P. Bijlaard ◽  
R. J. Dohrmann ◽  
J. M. Duke
Keyword(s):  
Heat Transfer ◽  
Cylindrical Shell ◽  
Heat Transfer Coefficient ◽  
Thermal Stress ◽  
Steam Generator ◽  
Thermal Stresses ◽  
Material Selection ◽  
Longitudinal Axis ◽  
Flow Rates ◽  
Circuit Configuration

A method has been developed which accurately predicts the thermal stresses and deformations in a nonuniformly heated cylindrical shell and has been applied to a steam generator membrane wall. The analysis is based on the theory of thermoelasticity and treats the membrane wall as a repetitive geometry. The tube and membrane are treated separately and are later joined, satisfying continuity. The analysis is also applicable to drums, nozzles, shells, and other cylindrical vessels as long as the temperture is steady and independent of the longitudinal axis of the geometry. Through the use of this method the thermal stresses can readily be calculated and thus assist in the establishment of flow rates, heat input or flux levels, circuit configuration, and material selection. In addition it provides the information to evaluate the effects of the inside heat transfer coefficient and variations in tube and web geometries on the thermal stresses.

Three-Dimensional Surface Heat Transfer Coefficient and Thermal Stress Analysis for Ceramics Tube Dipping into Molten Metal

2010 ◽  
Vol 452-453 ◽  
pp. 233-236 ◽  
Author(s):  
Yasushi Takase ◽  
Wen Bin Li ◽  
Hendra ◽  
Hiroki Ogura ◽  
Yusuke Higashi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Stress ◽  
Transfer Coefficient ◽  
Molten Metal ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient

The low pressure die casting machine has been used in industries because of its low-cost and high efficiency precision forming technique. In the low pressure die casting process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal, by means of a pressurized gas, to rise into a ceramic tube, which connects the die to the furnace. The ceramics tube, called stalk, has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the ceramics tube is dipped into the molten metal. It is important to reduce the risk of fracture that may happen due to the thermal stresses. To calculate the thermal stress, it is necessary to know the surface heat transfer coefficient when the ceramics tube dips into the molten metal. In this paper, therefore, the three-dimensional thermo-fluid analysis is performed to calculate surface heat transfer coefficient correctly. The finite element method is applied to calculate the thermal stresses when the tube is dipped into the crucible with varying dipping speeds and dipping directions. It is found that the thermal stress can be reduced by dipping slowly when the tube is dipped into the molten metal.

Analytical Approach to Crack Arrest Tendency Under Cyclic Thermal Stress for an Inner-Surface Circumferential Crack in a Finite-Length Cylinder

2000 ◽  
Vol 123 (2) ◽  
pp. 220-225 ◽  
Author(s):  
Toshiyuki Meshii ◽  
Katsuhiko Watanabe
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Finite Length ◽  
Thermal Stresses ◽  
Structural Parameters ◽  
Crack Arrest ◽  
Coolant Temperature ◽  
Transfer Condition ◽  
Circumferential Crack ◽  
Inner Surface

This paper presents a study of the crack arrest tendency under cyclic thermal stress for an inner-surface circumferential crack in a finite-length cylinder with its edges rotation-restrained, when the inside of the cylinder is cooled from uniform temperature distribution. The effects of structural parameters and heat transfer condition on the maximum transient SIF for the problem were investigated with the formerly developed systematical evaluation methods. Then, a tentative value of threshold stress intensity range ΔKth being assumed as well as Paris law, the evaluation of crack length for crack arrest under cyclic thermal stresses was carried out. Finally, a map to find the crack arrest point for a cylinder with mean radius to wall thickness ratio Rm/W=1 and a specific length H under various heat transfer conditions could be originated. From the map, it was predicted that when the heat transfer coefficient and/or initial wall-coolant temperature differences become large enough, the nondimensional crack arrest length saturates to a specific value and is no longer affected by those conditions.

TRANS2A: An Unconditionally Stable Code for Thermal Transient Stress Analysis in Piping

1981 ◽  
Vol 103 (1) ◽  
pp. 50-58 ◽  
Author(s):  
B. R. Strong ◽  
G. C. Slagis
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Stress Analysis ◽  
Thermal Stresses ◽  
Benchmark Problems ◽  
Solution Stability ◽  
Matrix Formulation ◽  
Difference Matrix ◽  
Water Steam ◽  
Complete Set

A technique for numerical integration of the finite difference (matrix) formulation of the unsteady heat transfer equation has been applied to the thermal stress analysis requirements of ASME B&PV Section III, Article NB-3650. This technique, with its properties of unconditional solution stability, has been incorporated into a new computer program, TRANS2A, which has been designed totally around the needs of the stress analyst. To be of maximum aid to the analyst, in addition to the necessary output of thermal gradients (ΔT2 and ΔT2) and average temperatures (Ta and Tb), TRANS2A provides a complete set of thermal stress histories and tables of thermal stress extrema. Values of the thermal stresses are output at maxima of the thermal gradient terms (with or without adjacent sections), in addition to the extrema of the secondary and secondary plus peak stresses and time of occurrence. Each solution is performed for a set of seven general and three optional stress indices. The process allows a strict and simple data interface to the combined stress analaysis computation without excessive approximations. Data may also be stored so that sections need not require repeated analyses. All computational output, from the detailed heat transfer solution to the stress summaries, may be requested or deleted at the option of the analyst. For generality, TRANS2A includes a complete set of temperature-dependent material properties for all current piping materials and a complete set of fluid properties for water, steam, and sodium. Fluid transient data are input using phase and temperature, and a choice of four flow rate specifications. Accepted heat transfer correlations for laminar and turbulent flow in liquids and gases are included, with smoothing at two-phase excursions. Samples of the TRANS2A benchmark problems are included, with discussions on data interface and sensitivity for erratic fluid transients.

Study on the Frequency Response Characteristics of Thermal Stress Induced by Multidimensional Fluid Temperature Fluctuation

2012 ◽  
Author(s):  
Cristian Santiago Perez T. ◽  
Naoto Kasahara
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Frequency Response ◽  
Temperature Fluctuation ◽  
Hot Spot ◽  
Heat Diffusion ◽  
Fluid Temperature ◽  
Dimensional Approach ◽  
One Dimensional ◽  
The Impact

A simplified one dimensional approach for predicting the thermal stress in structures subject to near wall fluid temperature fluctuations has been previously developed and published by the author Kasahara. The method predicted the thermal stress by calculating the frequency response, formulated by the product of the effective heat transfer and the effective thermal stress related to one-dimensional temperature gradient developed through the wall thickness of the structure. Although, currently adopted by the Japanese Society of Mechanical Engineers (JSME) guideline for calculating the thermal fatigue damage in structures, recent studies have highlighted the limitations of the one dimensional approach by showing the presences of multidimensional fluid temperature fluctuation in plane direction, increasing the need to extend the current analysis to more detailed multidimensional guideline. The aim of this research is to advance the theoretical knowledge and understanding of complex multidimensional phenomenon related to local thermal fluctuations within small localized area at the surface of the structure, referred to as “Hot Spot” which is observed to have important effects on the thermal stress phenomenon. Furthermore, the understanding of heat transfer processes in the structure, especially heat diffusion that is known to produce a thermal gradient and, therefore, thermal stress. Understanding the behavior of each heat transfer process in the Hot Spot and the relationship to the response in frequency has formed the bases for extending the current one-dimensional model. This paper presents the analytical results of the study and proposes an extended multidimensional model to understand the thermal stress in tee-junction due to fluid temperature fluctuation and the close relation with the frequency. The model is derived from the understanding of the phenomenon which has leaded to quantify the effect by introducing certain multidimensional factors to explain the impact of the multidimensional fluid temperature fluctuation.

Study on Relevant Effects Concerning Heat Transfer of a Convection Cooled Gas Turbine Blade Under Realistic Engine Temperature Conditions

2013 ◽  
Author(s):  
Y. Mick ◽  
B. Wörz ◽  
E. Findeisen ◽  
P. Jeschke ◽  
V. Caspary
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Stresses ◽  
Cooling System ◽  
Gas Turbine Blade ◽  
Temperature Conditions ◽  
The Impact ◽  
Operating Points

This paper presents a study of the temperature distribution of a convection cooled gas turbine blade under realistic operating temperature conditions using experimental and numerical methods. The analysis is performed experimentally in a linear cascade with exhaust gas from a kerosene combustor. Detailed information at different operating points is taken from the experiments for which conjugate heat transfer (CHT) simulations with ANSYS CFX are carried out. By comparing the experimental and numerical results, the required complexity of the simulations is defined. The subject of this study is a gas turbine rotor blade equipped with a state-of-the-art internal convection cooling system. The test rig enables the examination of the blade at temperatures up to 1300K. The temperature distribution of the blade is measured using thermocouples. The calculations are carried out using the SST turbulence model, the Gamma Theta transition model and the discrete transfer radiation model. The influence of hot gas properties and radiation effects are analysed at three different operating points. This paper gives a quantitative overview of the impact of the mentioned parameters on temperature level and distribution as well as thermal stresses in a convection cooled blade under realistic engine temperature conditions.

Modeling of Carburization and Thermal Stress Analysis for Ethylene Cracking Furnace Tube

2011 ◽  
Vol 704-705 ◽  
pp. 1136-1140
Author(s):  
Lu Yang Geng ◽  
Jian Ming Gong ◽  
Xiao Yan Qin ◽  
Li Min Shen
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Carbon Concentration ◽  
Thermal Stresses ◽  
Longitudinal Direction ◽  
Heating Process ◽  
Finite Element Code ◽  
Furnace Tube ◽  
The Finite Difference Method ◽  
Ethylene Cracking Furnace

The ethylene cracking furnace tube is one of the most important components of an ethylene cracking furnace. Carburization of furnace tube is one of the most important causes which lead the tube to fail. In this paper, the model that describes diffusion of carbon and the precipitation of carbides was established based on Fick’ law and equilibrium constant method. The finite difference method was adopted to simulate the distribution of carbon concentration. By applying the model, the distribution of carbon concentration along thickness in HP-Nb tubes was predicted for the different service times. According to the temperature distribution of furnace tube, obtained by the analysis of heat transfer, the thermal stresses of the furnace tube with various carburization extents were analyzed by using the finite element code ABAQUS for the actual heating process of an ethylene cracking furnace. The analysis results show that the maximum circumferential thermal stress exists near the inner wall of the carburized tube, which usually causes cracking of the carburized tube along the longitudinal direction.

Design and Optimization of the Internal Cooling Channels of a High Pressure Turbine Blade—Part I: Methodology

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Sergio Amaral ◽  
Tom Verstraete ◽  
René Van den Braembussche ◽  
Tony Arts
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Thermal Stress ◽  
Turbine Blade ◽  
Inlet Temperature ◽  
Analysis Tool ◽  
Internal Cooling ◽  
High Pressure Turbine ◽  
Cooling Channels ◽  
The Impact

This first paper describes the conjugate heat transfer (CHT) method and its application to the performance and lifetime prediction of a high pressure turbine blade operating at a very high inlet temperature. It is the analysis tool for the aerothermal optimization described in a second paper. The CHT method uses three separate solvers: a Navier–Stokes solver to predict the nonadiabatic external flow and heat flux, a finite element analysis (FEA) to compute the heat conduction and stress within the solid, and a 1D aerothermal model based on friction and heat transfer correlations for smooth and rib-roughened cooling channels. Special attention is given to the boundary conditions linking these solvers and to the stability of the complete CHT calculation procedure. The Larson–Miller parameter model is used to determine the creep-to-rupture failure lifetime of the blade. This model requires both the temperature and thermal stress inside the blade, calculated by the CHT and FEA. The CHT method is validated on two test cases: a gas turbine rotor blade without cooling and one with five cooling channels evenly distributed along the camber line. The metal temperature and thermal stress distribution in both blades are presented and the impact of the cooling channel geometry on lifetime is discussed.

Experimental and Numerical Investigation of Optimized Blade Tip Shapes—Part II: Tip Flow Analysis and Loss Mechanisms

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Marek Pátý ◽  
Bogdan C. Cernat ◽  
Cis De Maesschalck ◽  
Sergio Lavagnoli
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Thermal Stresses ◽  
Flow Analysis ◽  
Vortical Flow ◽  
Turbine Stage ◽  
Tip Leakage Flow ◽  
Blade Tip ◽  
The Impact ◽  
Blade Tip Geometry

The leakage flows within the gap between the tips of unshrouded rotor blades and the stationary casing of high-speed turbines are the source of significant aerodynamic losses and thermal stresses. In the pursuit for higher component performance and reliability, shaping the tip geometry offers a considerable potential to modulate the rotor tip flows and to weaken the heat transfer onto the blade and casing. Nevertheless, a critical shortage of combined experimental and numerical studies addressing the flow and loss generation mechanisms of advanced tip profiles persists in the open literature. A comprehensive study is presented in this two-part paper that investigates the influence of blade tip geometry on the aerothermodynamics of a high-speed turbine. An experimental and numerical campaign has been performed on a high-pressure turbine stage adopting three different blade tip profiles. The aerothermal performance of two optimized tip geometries (one with a full three-dimensional contoured shape and the other featuring a multicavity squealer-like tip) is compared against that of a regular squealer geometry. In the second part of this paper, we report a detailed analysis on the aerodynamics of the turbine as a function of the blade tip geometry. Reynolds-averaged Navier-Stokes (RANS) simulations, adopting the Spalart–Allmaras turbulence model and experimental boundary conditions, were run on high-density unstructured meshes using the numecafine/open solver. The simulations were validated against time-averaged and time-resolved experimental data collected in an instrumented turbine stage specifically setup for the simultaneous testing of multiple blade tips at scaled engine-representative conditions. The tip flow physics is explored to explain variations in turbine performance as a function of the tip geometry. Denton's mixing loss model is applied to the predicted tip gap aerodynamic field to identify and quantify the loss reduction mechanisms of the alternative tip designs. An advanced method based on the local triple decomposition of relative motion is used to track the location, size and intensity of the vortical flow structures arising from the interaction between the tip leakage flow and the main gas path. Ultimately, the comparison between the unconventional tip profiles and the baseline squealer tip highlights distinct aerodynamic features in the associated gap flow field. The flow analysis provides guidelines for the designer to assess the impact of specific tip design strategies on the turbine aerodynamics and rotor heat transfer.

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