Mono- and Multi-Objective CFD Optimization of Graded Foam-Filled Channels.

Gerardo Maria Mauro,Marcello Iasiello,Nicola Bianco,Wilson K. S. Chiu,Vincenzo Naso

doi:10.3390/ma15030968

Gerardo Maria Mauro, Marcello Iasiello + Show 3 more

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https://doi.org/10.3390/ma15030968

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Abstract

Graded foam-filled channels are a very promising solution for improving the thermal performance of heat sinks because of their customized structures that leave large amounts of room for heat transfer enhancement. Accordingly, this paper proposes a comprehensive optimization framework to address the design of such components, which are subjected to a uniform heat flux boundary condition. The graded foam is achieved by parameterizing the spatial distributions of porosity and/or Pores Per Inch (PPI). Mono- and multi-objective optimizations are implemented to find the best combination of the foam’s fluid-dynamic, geometrical and morphological design variables. The mono-objective approach addresses the Performance Evaluation Criterion (PEC) as an objective function to maximize the thermal efficiency of graded foams. The multi-objective approach addresses different objective functions by means of Pareto optimization to identify the optimal tradeoff solutions between heat transfer enhancement and pressure drop reduction. Optimizations are performed by assuming a local thermal non-equilibrium in the foam. They allowed us to achieve a 1.51 PEC value with H* = 0.50, ReH = 15000, iε = iPPI = 0.50, ε(0) = 0.85, ε(1) = 0.97, PPI(0) = 5, PPI(1) = 40, and ks→f = 104 as the design variables. For the three multi-objective functions investigated, one can extrapolate the optimum from the Pareto front via the utopia criterion, obtaining = 502 W/m2 K and Δp = 80 Pa, = 2790 and f = 42, = 0.011, and Δp* = 91. The optimal solutions provide original insights and guidelines for the thermal design of graded foam-filled channels.

Highlights

Open-cell foams are a very promising kind of material for enhancing heat transfer
The design of the graded foam-filled channel was optimized with different mono- and multi-objective approaches by implementing the procedure described in Figure 3, where a flowchart on its left side resumes the optimization procedure and the upward red and downward blue arrows refer to objective functions to be maximized and minimized, respectively
The genetic algorithm (GA) parameters for mono- and and multi-objective approaches by implementing the procedure described in Figure 3, where a flowchart on its left side resumes the optimization procedure and the upward red and downward blue arrows refer to objective functions to be maximized and minimized, respectively

Summary

Introduction

Open-cell foams are a very promising kind of material for enhancing heat transfer They are porous materials that are known as cellular materials because they consist of many communicating cells that are periodically repeated through the space. Because of their relatively high effective thermal conductivity and heat transfer area to volume ratio, as well as of their tortuosity characteristics that promote flow mixing, they are highly effective for applications where heat transfer plays a primary role, such as heat sinks [1,2], thermal energy storage systems [3], nanofluids-based heat exchangers [4], and so on. All of them can be labeled as functionally graded foams [9,10,11], where foam characteristics, such as porosity or Pores Per Inch (PPI), vary through the foam sample

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