thermohydraulics

Thermohydraulics is the study of heat transfer in moving fluids and the influence of fluid motion on temperature distributions. It combines principles from thermodynamics, heat transfer, and fluid mechanics to analyze energy transport in liquids and gases under convection, conduction, and, where applicable, radiation.

Mathematically, it involves solving the Navier-Stokes equations for momentum together with the energy equation, often with appropriate equations of state. In buoyancy-driven flows, the Boussinesq approximation is commonly used. Problems are characterized by dimensionless groups such as Reynolds, Prandtl, Nusselt, and Grashof numbers, which describe inertia, viscous effects, thermal diffusivity, and buoyancy influences. Solutions may be analytical for simple cases, but more typically rely on numerical methods, especially computational fluid dynamics (CFD). Experimental techniques and instrumentation validate models, using methods such as laser Doppler velocimetry or thermography.

Applications span cooling and heat management in nuclear reactors and power plants, design of heat exchangers, heating, ventilation, and air conditioning (HVAC), chemical processing, geothermal systems, solar thermal collectors, and other industrial processes where coupled heat and fluid flow occur. Thermohydraulics also informs safety analyses and performance optimization in engineering systems.

Key challenges include turbulence modeling, multiphase and phase-change phenomena, complex geometries, and transient behavior. Ongoing research addresses improved turbulence closures, porous media flow, and multi-physics coupling with chemical reactions or radiative heat transfer to enhance predictive capabilities and design efficiency.