Thermohydraulische

Thermohydraulics, often referred to as thermohydraulik in German, is the discipline that studies the coupled transport of heat and momentum in fluids. It addresses how temperature fields interact with fluid flow, influencing heat transfer, pressure drops, and flow stability in liquids and gases. The core problem is governed by the Navier–Stokes equations for momentum, the continuity equation, and the energy equation, with material properties such as density, viscosity, and thermal conductivity potentially varying with temperature. Dimensionless groups such as Reynolds, Prandtl, Nusselt, and Grashof numbers help characterize the relative effects of inertia, viscous forces, heat conduction, and buoyancy.

Phenomena in thermohydraulics include naturally occurring buoyancy-driven flows (natural convection) and forced flows, two-phase phenomena including boiling and condensation, and the behavior of liquid metals or cryogens. Many problems involve heat exchangers, cooling circuits, reactor cores, or electronic equipment where efficient removal of heat is essential.

Modeling and methods in thermohydraulics combine analytical approaches for simple geometries with numerical techniques such as computational fluid dynamics (CFD) for complex systems. The Boussinesq approximation is commonly used to simplify buoyancy effects, and turbulence models are applied where flows are chaotic. Experimental studies validate models and provide correlations for heat transfer coefficients and pressure drops.

Applications of thermohydraulics span power generation and nuclear engineering, where reactor cooling and safety margins are critical, as well as industry and electronics for cooling systems in machinery and HVAC. The field also supports solar thermal plants and chemical processing, where precise heat management is essential.