Transkritische

Transkritische refers to a state or process that occurs beyond the critical point of a substance. The critical point is a specific temperature and pressure at which the liquid and gas phases of a substance become indistinguishable. Above this point, a substance exists as a supercritical fluid, which possesses properties of both liquids and gases.

In a transkritische state, a substance is no longer classified as distinctly liquid or gas. Instead, it behaves as a supercritical fluid, characterized by a high density similar to liquids and a low viscosity and high diffusivity similar to gases. This unique combination of properties makes supercritical fluids highly effective solvents for various applications.

Transkritische processes are often employed in industrial applications such as supercritical fluid extraction (SFE), where supercritical carbon dioxide is used to extract compounds from natural products, food, and pharmaceuticals. The ability to tune the solvent properties of a supercritical fluid by adjusting temperature and pressure allows for selective extraction and purification. Another application is in transkritische Rankine cycles for power generation, which can achieve higher efficiencies than traditional steam cycles by operating above the critical point of the working fluid. The term transkritische emphasizes the state of being beyond the critical point, where distinct phase boundaries cease to exist and unique fluid properties emerge.