Gas–Solid Interfacial Heat Transfer Characteristics of Uncoated and Coated Metal Foams for Both Laminar and Turbulent Flow Regimes

Metal foams have been widely used in many fields requiring excellent heat and mass transfer performance such as heat exchangers and catalytic reactors. However, the movements of gas–solid interfacial heat transfer characteristic curve with the structural parameters of foams for uncoated metal foams and the washcoat thickness for coated metal foams are not explained in depth. In this work, gas–solid interfacial heat transfer characteristics of metal foams without and with a washcoat were studied in detail in both laminar and turbulent flows using the body-centered-cubic (BCC) unit cell model by the method of computational fluid dynamics, considering that the structural parameters of uncoated/coated foams could be accurately controlled in the numerical method. The movements of gas–solid interfacial heat transfer characteristic curve with the structural parameters of foams and the washcoat thickness were successfully verified and explained using the numerical data in both laminar and turbulent flows. The results show that the porosity not the pore/cell diameter is the reason of the moving of gas–solid interfacial heat transfer characteristic curve for uncoated/coated foams. In laminar flow, the porosity influences interfacial heat transfer characteristic curve through the effective thermal conduction of fluid phase; and in turbulent flow, interfacial heat transfer characteristic curve is affected by porosity through the inertial effect of flow. A new correlation of gas–solid interfacial heat transfer coefficient for uncoated/coated metal foams suitable for both laminar and turbulent flows was proposed by taking into consideration this phenomenon.