Comparison and Analysis of Heat Transfer in Aluminum Foam Using Local Thermal Equilibrium or Nonequilibrium Model

Abstract

Aluminum foams are favorable in modern thermal engineering applications because of the high thermal conductivity and the large specific surface area. The present study aims to investigate an application of porous aluminum foam by using the local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) heat transfer models. Three-dimensional simulations of laminar flow (porous foam zone), turbulent flow (open zone) and heat transfer are performed by a computational fluid dynamics approach. In addition, the Forchheimer extended Darcy's law is employed to evaluate the fluid characteristics. By comparing and analyzing the average and local Nusselt numbers, it is found that the LTNE and LTE models can reach the same Nusselt numbers inside the aluminum foam when the air velocity is high, meaning that the aluminum foam is in a thermal equilibrium state. Besides, a high interfacial heat transfer coefficient is required for the aluminum foam to reach a thermal equilibrium state as the height of the aluminum foam is reduced. This study suggests that the LTE model can be applied to predict the thermal performance at high fluid velocities or for the case with a large height.

Minimization of exergy destruction with discrete metal foam filling in a pipe under turbulent flow condition

“…It is clear from Figure 1 that the pipe is symmetrical along the centerline ( x -axis), henceforth only half of the conduit is taken as a numerical model. To accomplish a developed flow at the entrance and to avoid the exit effects, the numerical model is extended 2 times and 1.5 times the metal foam length at the upstream and downstream of the test section, respectively (Lin et al , 2015), and is shown in Figure 3.…”

Effect of thickness and thermal conductivity of metal foams filled in a vertical channel – a numerical study

“…The effects of inertia and viscous because of form drag coefficient and permeability of the porous metal foam are considered in the momentum equation. The following are the equations considered for solving the high porous metal foam region Lin et al (2016): …”

“…They identified flow and transition regimes such as Pre-Darcy, transition to Darcy and Darcy regime based on the Reynolds number. Lin et al (2016) numerically studied the forced convection through aluminum metal foams by considering both local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE) thermal models and found that both the LTE and LTNE provide same performance at higher velocities of air. Ly et al (2016) showed the use of numerical FFT model to compute the permeability from the digital images of the porous media.…”

بررسی اهمیت سازو کار مهاجرت گرمایی در مبدل ‌های حرارتی اسفنجی با استفاده از شبیه سازی

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