Topology Optimization of Discontinuous Fin-Based Microchannel Heat Exchangers

Abstract This paper addresses the development of an in-house solver for a multi-objective optimization function aimed at designing the individual fins to improve the performance of discontinuous plate-fin microchannel heat exchangers (PFMCHEs). The objective functions used in this study are stagnation pressure energy, thermal energy gain, and entropy generation. A penalization factor is used to impose the distribution of solid and fluid domains that handle the variability of shape changes in the design domain resulting in tradeoffs between competing goals of the objective functions. This factor is bundled into the governing equations to capture the relative solid and fluid grids in the solver domain, which vary in successive iterations for optimization. A generalized computational fluid dynamics solver coupled with an optimization algorithm is used to evaluate the efficacy of heat exchanger designs. The numerical framework based on finite volume formulation incorporating suitable interpolation schemes ensures convergence of the governing equations, while the optimization framework provides a trade-off in the performance parameters. The analysis is performed on a single plate of a PFMCHE, wherein the variability in the results is examined based on the tuning parameters of the objective function. The solver develops variable fin designs/shapes featuring efficient thermal energy transfer with minimal pressure drop and entropy generation characteristics. A test case for rectangular fin-shaped PFMCHE is considered to validate the optimization algorithm in achieving optimal solutions. The result indicates that the length of individual fins is more pronounced at the center of PFMCHE, leading to a 30–35 % reduction in pressure drop and entropy generation relative to the initial design. It is noted that the pressure drops, and entropy generation are more prominent criteria accepted for objective function for sound design of heat exchangers than thermal energy gain.