Browsing by Author "Huang, Chih-Hung"

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A modified hydrodynamic model for pool boiling CHF considering the effects of heater size and nucleation site density
(2015-05-01)
Lu, Ming-Chang
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Huang, Chih-Hung
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Huang, Chung-Te
;
Chen, Yu-Chi
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機械工程學系
Boiling is commonly used in daily life and is an efficient heat removal method. During pool boiling, the critical heat flux (CHF) establishes the upper limit of efficient heat removal. Although, numerous studies have explored CHF, its exact mechanisms remain ambiguous. The hydrodynamic instability model is the most prominent CHF model, but it fails to explain the evident dependence of CHF on surface properties. The authors proposed modifying the hydrodynamic model to account for how nucleation site density and finite heater size affect the CHF. The experimental CHF values obtained from evaluating various types of surfaces qualitatively agreed with the predictions of the modified hydrodynamic model. This suggests that the CHFs on these surfaces were due to the hydrodynamic limit. (C) 2015 Elsevier Masson SAS. All rights reserved.
A two-phase computational scheme for solving bang-bang control problems
(2006-12-01)
Huang, Chih-Hung
;
Tseng, Ching-Huan
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機械工程學系
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Department of Mechanical Engineering
This paper focuses on numerical methods for solving time-optimal control problems using discrete-valued controls. A numerical Two-Phase Scheme, which combines admissible optimal control problem formulation with enhanced branch-and-bound algorithms, is introduced to efficiently solve bang-bang control problems in the field of engineering. In Phase 1, the discrete restrictions are relaxed, and the resulting continuous problem is solved by an existing optimal control solver. The information on switching times obtained in Phase I is then used in Phase 11 wherein the discrete-valued control problem is solved using, the proposed algorithm. Two numerical examples, including, a third-order system and the F-8 fighter aircraft control problem, are presented to demonstrate the use of this proposed scheme. Comparing to STC and CPET methods proposed in the literature, the proposed scheme provides a novel method to find a different switching structure with a better minimum time for the F-8 fighter jet control problem.