Handbook of SiC properties for fuel performance modeling

Biopolymer aerogels were among the first aerogels produced, but only in the last decade has research on biopolymer and biopolymer-composite aerogels become popular, motivated by sustainability arguments, their unique and tunable properties, and ease of functionalization. Biopolymer aerogels and open-cell foams have great potential for classical aerogel applications such as thermal insulation, as well as emerging applications in filtration, oil-water separation, CO2 capture, catalysis, and medicine. The biopolymer aerogel field today is driven forward by empirical materials discovery at the laboratory scale, but requires a firmer theoretical basis and pilot studies to close the gap to market. This Review includes a database with over 3800 biopolymer aerogel properties, evaluates the state of the biopolymer aerogel field, and critically discusses the scientific, technological, and commercial barriers to the commercialization of these exciting materials.

Biopolymer Aerogels and Foams: Chemistry, Properties, and Applications.

Adsorbed layer and thin film growth modes monitored by Auger electron spectroscopy

Mini- and micro-channels: influence of axial conduction in the walls

The free-space Green’s function is used to evaluate electromagnetic wave scattering and radiation from currents in free space. This section investigates two examples using the free-space Green’s function, namely, radiation from a sheet current and radiation from a shell current.

Green’s Functions: Applications

The measurement of the thermal diffusivity of a thin layer in the direction of its plane is usually a difficult operation. The standard ‘‘flash technique’’ is very appropriate for diffusivity measurement in the direction of the thickness of the sample but adaptations of this method to in‐plane measurements remain very sensitive to the position and form of heat excitation and temperature sensors. The new procedure proposed here consists of applying any geometrically nonuniform heat impulse on the front face of the sample and recording the entire transient temperature image on the rear face thanks to an infrared camera. The influence of axial diffusion can be avoided for periods much longer than the axial diffusion characteristic time. Integral transforms on the radial space variables (Fourier transform) are very suitable for treating the temperature field and to estimate radial diffusivity. The main advantage of this method is to avoid any experimental precaution (no knowledge of the geometrical form of the excitation ‐ replacement of the sensor positioning by an image calibration). Furthermore, the considerable number of data produced by the camera is processed using a statistical approach. The validation of the method is made on a homogeneous sample by comparison between the in‐plane direction measurements (obtained with the present procedure) and the thickness direction measurements (obtained by the classical flash technique).

Measurement of thermal diffusivities through processing of infrared images

This paper presents a method dedicated to thermal conductivity measurement of thin (a few millimeters thickness) insulating and super-insulating materials. The method is based on the measurement of the temperature at the center of a heating element inserted between two samples, with the unheated surface of the samples maintained constant. A 3D model of the heat transfer in the system has been established and simulated to determine the validity conditions of a 1D model to represent the center temperature. This 1D model was then used to realize a sensitivity analysis of the center temperature to the different parameters. The conclusion is that the thermal conductivity may be estimated with a good precision for all insulating materials from a simple steady state measurement and that the thermal capacity may also be estimated from transient recording of the temperature with a precision increasing with the value of the thermal capacity of the samples. It has then been shown that a device with two samples of different thickness improves the precision of the estimation of the thermal capacity. These conclusions are validated by an experimental study on polyethylene foam and PVC samples leading to an estimation of their thermal properties very close to the values measured by other classical methods (deviation < 5%).

A centered hot plate method for measurement of thermal properties of thin insulating materials

A theoretical study of the transient coupled conduction and radiation heat transfer in glass: phonic diffusivity measurements by the flash technique

Thermal conductivity measurement of insulating materials with a three layers device

One-dimensional transient energy transfer by conduction and radiation is solved for a finite medium. The semitransparent layer emits, absorbs, and scatters radiation (participating medium). The coupled transfer is solved analytically by considering the well-known two-flux approximation, assuming linear transfer and using the Laplace transform. The semitransparent layer can then be modeled by a matrix transfer function. The accuracy of the solution is verified in the case of sharp thermal excitation by a heat pulse on the front face. It is shown that this general model is very accurate for simulating both the limiting cases of purely scattering and purely absorbing media. In the latter case, the same modeling is derived using the kernel substitution technique, and very good agreement is achieved compared with numerical simulations. The resulting computation times are very small, and suggest that such a model can be used in the inverse approach of thermal problems involving semitransparent materials.

Alain Degiovanni

Papers

Measurement of thermal diffusivities through processing of infrared images

A centered hot plate method for measurement of thermal properties of thin insulating materials

A theoretical study of the transient coupled conduction and radiation heat transfer in glass: phonic diffusivity measurements by the flash technique

Thermal conductivity measurement of insulating materials with a three layers device

A new way of solving transient radiative-conductive heat transfer problems