Tomography-Based Determination of the Effective Thermal Conductivity of Fluid-Saturated Reticulate Porous Ceramics

Photograph of Specimen A: a low-porosity (average porosity of 81%) cylindrical 10pores∕in. Rh-catalyst coated SiC-made RPC sample

CT reconstruction of a cross section of the RPC’s Specimen A. Some central channels are indicated by 1.

3D digital reconstruction of a slice of the RPC’s Specimen A, based on the macroscale CT data set and the isosurface at the segmentation gray value

Photograph of Specimen C: a single strut sample of the Rh-catalyst coated SiC-made RPC sample, showing the triangular cross-sectional geometry of the central channel

CT cross-sectional reconstruction of the strut Specimen C

3D digital reconstruction of the strut Specimen C, based on the microscale CT data set and the isosurface at the segmentation gray value

Schematic of steady-state conduction heat transfer through a two-phase cubic sample of RPC, with temperature boundary conditions T1 and T2 on two of the opposing faces of the cube and adiabatic conditions on the remaining four faces of the cube

Isothermal contour lines of the normalized temperature distribution (T−T2)∕(T1−T2) in a cross-sectional plane obtained from pore-level direct numerical simulation of conduction heat transfer on a subset of Specimen A. Boundary conditions: T=T1 at the bottom (z=0mm) and T=T2 at the top (z=9mm). The solid areas are depicted in black.

Ratio of the macroscale and microscale effective thermal conductivities (ke,macro∕ke,micro) as a function of the ratio of the fluid and strut thermal conductivities (kf,macro∕ke,micro), obtained by the macroscale direct numerical simulation of 12 nonoverlapping subsamples of Specimens A and B with varying porosity. Indicated by a dashed line are the regions where the GCI is below and above 10%.

Ratio of the macroscale and microscale effective thermal conductivities (ke,macro∕ke,micro) as a function of the ratio of the fluid and strut thermal conductivities (kf,macro∕ke,micro), obtained by the macroscale direct numerical simulation and by the ke models: (a) parallel and serial bounds, Dul’nev’s model, and three-resistor model; (b) Calmidi’s and Mahajan’s model (analytical), model of Bhattacharya , and Boomsma and Poulikakos’s model for reticulate structures; (c) Calmidi and Mahajan’s (empirical) and Miller’s models

Ratio of the microscale effective thermal conductivity to the pure solid thermal conductivity (ke,micro∕ks) as a function of the ratio of the fluid-to-solid thermal conductivities (kf,micro∕ks), obtained by the microscale direct numerical simulation and by the ke models

Contour map of the ratio of the overall effective thermal conductivity to the pure solid thermal conductivity (ke,macro∕ks) as a function of microscale fluid-to-solid thermal conductivity ratio (kf,micro∕ks) and macroscale fluid-to-solid thermal conductivity ratio (kf,macro∕ks). εmacro=0.90, εmicro=0.12.