scholarly journals Development of Adaptive Mesh Refinement Scheme and Conjugate Heat Transfer Model for Engine Simulations

2009 ◽  
Author(s):  
Qingluan Xue
Author(s):  
Jianhu Nie ◽  
David A. Hopkins ◽  
Yitung Chen ◽  
Hsuan-Tsung Hsieh

A 2D/3D object-oriented program with h-type adaptive mesh refinement method is developed for finite element analysis of the multi-physics applications including heat transfer. A framework with some basic classes that enable the code to be built accordingly to the type of problem to be solved is proposed. The program consists of different modules and classes, which ease code development for large-scale complex systems, code extension and program maintenance. The developed program can be used as a “test-bed” program for testing new analysis techniques and algorithms with high extensibility and flexibility. The overall mesh refinement causes the CPU time cost to greatly increase as the mesh is refined. However, the CPU time cost does not increase very much with the increase of the level of h-adaptive mesh refinement. The CPU time cost can be saved by up to 90%, especially for the simulated system with a large number of elements and nodes.


Author(s):  
Jianhu Nie ◽  
Yitung Chen ◽  
David A. Hopkins ◽  
Lijian Sun ◽  
Hsuan-Tsung Hsieh

A finite element program with h-type mesh adaptation is developed and several test cases for heat transfer, fluid mechanics and structural mechanics are selected for code validations. The element division method is used because of its advantage of avoiding overly twisted elements during mesh refinement and recovery. The adaptive mesh is refined only in the localization region where the feature gradient is high. The overall mesh refinement and the h-adaptive mesh refinement are justified with respect to the computational accuracy and the CPU time cost. Both can improve the computational accuracy. The overall mesh refinement causes the CPU time to greatly increase. However, the CPU time does not increase very much with the increase of the level of h-adaptive mesh refinement. The CPU time cost can be saved using the developed program by orders of magnitude, especially for the system with a large number of elements and nodes.


Author(s):  
Hongmin Li ◽  
Edward A. Evans ◽  
G.-X. Wang

Numerical modeling becomes an important technique to study hydrothermal crystal growth since experimental measurements in hydrothermal autoclaves are extremely difficult due to the high pressure and high temperature growth conditions. In all existing models for hydrothermal growth, isothermal boundary conditions are assumed, although electric heaters are employed around the outside surface of the thick autoclave wall in practice. In this paper, a conjugate heat transfer model based on an industry size autoclave is developed to investigate the validity of such an assumption. The model includes not only turbulent fluid flow and heat transfer of the solution but also the heat conduction in the thick wall. The outside surfaces of the wall are under constant heat flux conditions, simulating electric resistance heating used in practice. Non-uniformity of the heat flux in the circumferential direction is also introduced in the model. The results indicate that the temperature at the solution/wall interface is far away from uniform. The isothermal wall boundary condition in previous efforts is questionable. Predictions of the isothermal wall model are analyzed. Parametric studies with the conjugate model show that total heat supply rate does not affect vertical uniformity dramatically. Heat loss can be lowered without affecting the flow and temperature fields if heaters are put half diameter or further away from the middle height (baffle) plane.


Author(s):  
Liang Peng ◽  
Zhenlei Chen ◽  
Yi Hu

Aiming at the issues of low accuracy and poor feasibility of the analytical results of the turbocharger turbine temperature field under operating conditions, a full-domain conjugate heat transfer numerical model was established by the conjugate heat transfer and finite volume method. The temperature field characteristics of each component of the turbocharger turbine were analyzed. The numerical and experimental test results were compared and analyzed. The global conjugate heat transfer model avoids the input of a large number of hypothetical data on the interface between fluid and solid in the traditional model, and makes the calculation process closer to the actual situation. Through the comparison with the experimental results, the accuracy of the turbine temperature field obtained by the global conjugate heat transfer model is more reasonable and more accurate than that of the traditional model, which verifies the reliability and accuracy of the global conjugate heat transfer model.


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