Eventos Anais de eventos
ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
Second Law Based Closed Brayton Cycle Regenerator Optimization
Submission Author:
Elvis Falcao , SC , Brazil
Co-Authors:
Elvis Falcao, Guilherme Borges Ribeiro, Lamartine Guimarães
Presenter: Elvis Falcao
doi://10.26678/ABCM.ENCIT2018.CIT18-0115
Abstract
This work is a compilation of the research steps that were conducted in an optimization of a cross-flow heat exchanger, which is the regenerator of a Closed Brayton Cycle (CBC) to be used in space missions. The importance of the regenerator on thermal machine design relies on the fact that it provides heat transfer between the hot and cold entities, pre-heating fluid in the heat source inlet and increasing overall system efficiency. Besides, it usually occupies the major part of system size because its effectivity depends on heat transfer area, and system volume is a critical parameter to be minimized in space applications. The second law of thermodynamics states that every process, from a thermal standpoint, produces entropy. In the Entropy Generation Minimization (EGM) method, the rate of this generation, which is proportional to the Lost Available Work (LAW), is used as a Performance Evaluation Criteria (PEC) for system analysis and optimization. As fluid flows through both sides of the heat exchanger, entropy is produced mainly by heat transfer and pressure drop, producing LAW. This study aims to find an optimum mass flow rate for the regenerator by evaluating a non-dimensional used to measure the entropy generation rate, the Entropy Generation Number (Ns), for multiples mass flow rate values, using 3D Computational Fluid Dynamics (CFD) as a support tool. The flow is resolved in the heat exchanger's interior using the Finite Volume Method (VFM). Relevant fluid state properties are used for a second-law based optimization.
Keywords
Closed Brayton Cycle, Regenerator, CFD, Entropy
