Natural convection in metal foams with open cells

被引:133
作者
Zhao, CY [1 ]
Lu, TJ
Hodson, HP
机构
[1] Xian Jiaotong Univ, Sch Energy & Power Engn, State Key Lab Multiphase Flow, Xian 710049, Peoples R China
[2] Brunel Univ, Sch Engn & Design, Dept Mech Engn, Uxbridge UB8 3PH, Middx, England
[3] Univ Cambridge, Dept Engn, Cambridge CB2 1PZ, England
[4] Xian Jiaotong Univ, Sch Aeronaut & Astronaut, Xian 710049, Peoples R China
基金
英国工程与自然科学研究理事会;
关键词
cellular metal foams; natural convection; thermal conductivity; modeling; measurements;
D O I
10.1016/j.ijheatmasstransfer.2005.01.002
中图分类号
O414.1 [热力学];
学科分类号
摘要
This paper presents a combined experimental and numerical study on natural convection in open-celled metal foams. The effective thermal conductivities of steel alloy (FeCrAlY) samples with different relative densities and cell sizes are measured with the guarded-hot-plate method. To examine the natural convection effect, the measurements are conducted under both vacuum and ambient conditions for a range of temperatures. The experimental results show that natural convection is very significant, accounting for up to 50% of the effective foam conductivity obtained at ambient pressure. This has been attributed to the high porosity (epsilon > 0.9) and inter-connected open cells of the metal foams studied. Morphological parameters characterizing open-celled FeCrAlY foams are subsequently identified and their cross-relationships are built. The non-equilibrium two-equation energy transfer model is employed, and selected calculations show that the non-equilibrium effect between the solid foam skeleton and air is significant. The study indicates that the combined parameter, i.e., the porous medium Rayleigh number, is no longer appropriate to correlate natural convection by itself when the Darcy number is sufficiently large as in the case of natural convection in open-celled metal foams. Good agreement between model predictions and experimental measurements is obtained. (c) 2005 Elsevier Ltd. All rights reserved.
引用
收藏
页码:2452 / 2463
页数:12
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