Reduced-order cfd-based multi-rating of aviation heat exchangers

The Computational Fluid Dynamics (CFD) approach can be used to calculate the j and f factors for new heat exchanger designs, such as additively-manufactured components, for which no correlations are available. The goal envisioned for Reduced-Order Computational Fluid Dynamics and Heat Transfer (ROM-CFD) is obtaining fast turnaround in simulation time so that CFD can form a component of a system-level synthesis/design tool. Toward this end, in the procedure proposed in this study, no more than two-dimensional Cartesian or axisymmetric models are solved for fluid flow and heat transfer. The fact that the analysis of the other components of a system involves errors significantly larger than the levels typically allowed in CFD practice also enhances the development of a ROM-CFD tool. Furthermore, the use of high-order finite element approximations for the governing equations enables us to obtain almost spectral-like resolution, allowing us to simulate with a coarse mesh, even for fairly complicated HEX components. Also, the use of an advanced time integration error-control scheme in the proposed ROM-CFD enables the selection of time step sizes that could vary by several orders of magnitude in a single simulation, leading to astronomically fast numerical solution the equations. Other numerical procedures, such as the use of the penalty method to handle the incompressibility constraint and the employment of the direct solution method, which is quite suitable for models with relatively few degrees of freedom, are leveraged in the development of the ROM-CFD tool. The precise purpose of the present work is to show that only a relatively few number of high-order elements may be needed to obtain the accuracy required in order to extract the heat exchanger j/f correlations from CFD simulations.