Eventos Anais de eventos
COBEM 2019
25th International Congress of Mechanical Engineering
Thermodynamic Optimization of a Heat Exchanger used in Themal Cycles Applicable for Space Systems
Submission Author:
Guilherme Borges Ribeiro , SP , Brazil
Co-Authors:
Elvis Falcao, Guilherme Borges Ribeiro
Presenter: Guilherme Borges Ribeiro
doi://10.26678/ABCM.COBEM2019.COB2019-0540
Abstract
Nuclear power conversion in space has been approached in several different ways since the first space missions. Nowadays, thermal cycles are under greater focus for being capable of providing higher conversion efficiencies. In this context, one of the main concerns of designers and engineers is the trade-off between power and mass. Therefore, this work aims the optimization of a recuperator used in a regenerative Closed Brayton Cycle applied for power conversion in the project of a space nuclear reactor. It is a cross-flow, shell-and-tube heat exchanger with a matrix of tubes distributed in a staggered configuration. In this work, the number of tubes and the mass flow rate are varied. The number of tubes distributed axially is fixed in 4, while the quantity around the axis varies between 5, 7, 9, 12 and 16 tubes. The fluid and solid materials are respectively He-Xe (40 g/mol) and alloy 617. The optimization studies are supported by CFD and entropy generation minimization. Optimum mass flow rates are obtained for all the geometries at the points of minimum entropy generation number, around which lie the ranges of tested mass flow rates. Geometry selection is performed using the ratio of minimum entropy generation number to effectiveness at the optimum mass flow rate associated to a given geometry as performance evaluation criteria and assessing its behavior with exchanger mass. This analysis leads to the optimum design point at the geometry of 9 tubes around recuperator axis, with 0.1 kg/s mass flow rate, 0.059 entropy generation number and 0.2312 effectiveness.
Keywords
recuperator, CFD, Entropy, Heat transfer, pressure drop
