An atomistic model for the thermal resistance of a liquid–solid interface

The thermal resistance associated with the interface between a solid and a liquid is analysed from an atomistic point of view. Partial evaluation of the associated Green–Kubo integral elucidates the various factors governing heat transport across the interface and leads to a quantitative model for the thermal resistance in terms of atomistic-level system parameters. The model is validated using molecular dynamics simulations.

RETALT_TPS design and manufacturing

The present document discusses the development of a new trowelable Thermal Protection System (TPS), able of being mixed, applied and cured directly onto the vehicle structure, with the aim to fulfill the requirements of the thermal properties for the re-usable launch vehicle studied in the Retro Propulsion Landing Technology (RETALT) project. During the development of this TPS, several formula optimizations were made to improve or eliminate cracks in the char surface, increase char stiffness, rheological adjustments, and adhesion improvement to different substrates. The most promising material developed is composed by cork and epoxy resin, together with a set of rheological and thermal resistance additives, that makes it possible to be applied with a spatula, while at the same time it is able to withstand the demanding environmental conditions during atmospheric reentry. In terms of thermal properties, the developed material has a higher thermal conductivity than the current P50 TPS commercialized by Amorim Cork Composites (ACC), but it has a better behavior when exposed to flame conditions. It is expected that the absence of cracks improves its structure and resistance to demanding conditions. The development work included a detailed study of the composition and processes required for the development of a TPS material, which were evaluated by several types of flame characterization tests and thermal properties analysis.

Температурный режим и механические напряжения в корпусированных фотоэлектрических преобразователях концентрированного солнечного излучения

In photovoltaic converters of concentrated sunlight, the thermal flow is directed from the photoactive region (p-n junction) to a heat-spreading basement through the substrate. The heat sink transfers the excess thermal to the environment by convection or cooled by a liquid carrier. Reducing the thickness of the substrate makes it possible to reduce the thermal resistance of the crystal and lower the operating temperature of the photoactive region. However, in this case, the mechanical stresses in it increase. This work discusses the balance between the mechanical strength of the sample and the decrease in its operating temperature.