No abstract

The increase in the temperature difference between the spadix and ambient air appears to be physically constrained and corresponds to the value of a thermal model of heat conduction in an insulated cylinder with an internal heat source. In the models, a heat metabolic rate of 29.5 mW g(-1) was used, which was an acceptable value for an overall metabolic heat rate in aroid inflorescences.

A thin-film-heater method is setup to measure the thermal conductivity of super insulating materials such as silica aerogels. The experimental setup is purposely designed for insulating materials and allows direct measurement of the thermal conductivity. Few experimental data are available in the literature concerning thermal conductivity of aerogels even though these materials are of major interest in thermal insulation. More data are necessary in order to understand thermal transport and to validate existing models. Monolithic and granular silica aerogels are investigated. Our experimental technique enables to quantify the influence of important parameters, such as air pressure and distribution of grain sizes, on the insulating performance of this material.

Periodic patterns built with elementary Von Koch snowflakes have been found to be a good structural representation of nanoporous media (like monolithic silica aerogels) concerning the characterization of heat conduction. These geometries allow the modeling of different pore sizes, fractality and isotropy of the complex structure. A numerical model has been used to determine the effective thermal conductivity as a function of two parameters: density and tortuosity. The results -which match with an analytical model presented in the literature-are compared to simple periodic and random fractal geometries.