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Development of design optimization methodology using CFD as the design tool applied to printed circuit heat exchanger
Citation
Ridluan, Artit.. (2009). Development of design optimization methodology using CFD as the design tool applied to printed circuit heat exchanger. Theses and Dissertations Collection, University of Idaho Library Digital Collections. https://www.lib.uidaho.edu/digital/etd/items/etd_32.html
- Title:
- Development of design optimization methodology using CFD as the design tool applied to printed circuit heat exchanger
- Author:
- Ridluan, Artit.
- Date:
- 2009
- Keywords:
- Heat exchangers--Design and construction--Case studies Heat exchangers--Fluid dynamics Computational Fluid Dynamics
- Program:
- Mechanical Engineering
- Abstract:
- In engineering design, optimization methods are typically based on trial-and-error design and local search approaches. In nuclear reactor design, conservative approaches are directly linked to safety margin in operation under anticipated and unanticipated off-normal scenarios. These approaches require iterative experimentation and analyses (time) to locate the optimum. Moreover, the actual response surface (design solution within design space) may have multiple, regional maxima and minima. The search process may only yield a local optimum, not an absolute optimum. Thus, these practices in reactor engineering need to be changed when applied to advanced nuclear systems. Design conservatism must be reduced in search of efficiency with respect to performance, while meeting regulatory (licensing) requirements.;This dissertation proposes, develops, and demonstrates a new systematic design optimization methodology. Three key elements (tools), Computational Fluid Dynamics (CFD), Artificial Neural Network (ANN), and Response Surface Methodology (RSM) are integrated into the design engineering process to limit, reduce, and eliminate past conservative methodologies and to improve the optimization process. To test this methodology, the Printed Circuit Heat Exchanger (PCHE) was selected as a Case Study since the PCHE is being considered as the Next Generation Nuclear Plant's (NGNP) Intermediate Heat Exchanger (IHX). Further, a thermally efficient IHX is key to an optimal NGNP balance-of-plant.;Foremost, modeling and simulation results for each key design tool were collected, to determine the capability and accuracy of each tool. The first result showed that CFD simulation can capture unsteady phenomena; vortex shedding, using unsteady RANS-based CFI) simulation The second CFD simulation predicted key thermohydraulic parameters, friction coefficient and Nusselt number. Thus via benchmarking, CFD can be used as a design tool and integrated into the proposed design optimization process. The third result showed that ANN, EBaLM [Error-Back (Propagation) and Levenberg-Marquardt] algorithm, adapts well to thermophysical property nonlinearities and to system fluctuations (in thermal-hydraulics) under relevant conditions. Most importantly, EBaLM provided a means to consistently enhance the dataset within the design space so as to reduce CFD simulations. It became clear that ANN can be used as a design tool and integrated into the proposed design optimization process.;In NGNP PCHE design optimization Case Study, the design parameters considered were the vertical (t) and horizontal (p) distances between channels, channel diameter (d), and streamwise (l) and spanwise (h) zigzagged lengths of the channels. With five levels of each design parameter, the total combination of parametric variations requires as many as 3.125 (5{esc}p5{esc}s) CFD runs. Under the proposed design optimization methodology, this number of simulations is systematically and effectively reduced to 52 runs.;Benchmarked CFD simulation was used to generate PCHE thermal effectiveness (E), hot-sided and cold-sided pressure drops (DPh and DPc). The design space of pressure drops was first globally explored using Uniform Design theory. A candidate subregion that can satisfy functional requirements was then identified. Based on CFD simulations, RSM was then used to develop surface equations to represent the PCHE response in terms of E, DPh, and DPc. These surface equations were then used to determine the optimal design parameters using a Generalized Reduced-Gradient (GRG) algorithm.;The unique contribution is the development and demonstration of a design optimization methodology. Specifically, the results showed that the optimization method is systematic and effective for following reasons: (1) exploration of a large design space facilitates the search of a subregion that can meet the defined constraint, (2) only 52 CFD simulations were performed, (3) for given input and output conditions, the effectiveness was improved ~19% relative to simplified PCHE configurations (straight channel); ~6.5% and 15% reduction in DPh, and DPc were observed relative to a simplified configuration, and (4) the design optimization process was completed in two steps, thus eliminating the iterative search process.
- Description:
- Thesis (Ph. D., Mechanical Engineering)--University of Idaho, June 2009.
- Major Professor:
- Akira Tokuhiro.
- Defense Date:
- June 2009.
- Type:
- Text
- Format Original:
- xxii, 328 leaves :col. ill. ;29 cm.
- Format:
- record
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