soojusjaotumine

Soojusjaotumine (heat distribution) refers to the spatial and temporal distribution of thermal energy within a material or system caused by temperature differences. It arises from three fundamental modes of heat transfer: conduction, convection, and radiation, and is influenced by material properties such as thermal conductivity, density, and specific heat capacity.

Conduction occurs in solids and stationary fluids when atoms or molecules transfer energy through collisions and lattice vibrations, driven by temperature gradients. Fourier's law describes the heat flux q = -k ∇T, where k is thermal conductivity. The resulting heat equation describes how temperature changes in time and space.

Convection involves heat transfer by bulk motion of a fluid. Natural convection occurs due to buoyancy forces from density variations; forced convection uses external means such as fans or pumps. Convection is characterized by an average heat transfer coefficient h and a temperature difference between surface and fluid.

Radiation transfers energy by electromagnetic waves and can occur between bodies at a distance. It depends on emissivity ε, area A, and the fourth power of absolute temperature (Stefan–Boltzmann law): P = εσA(T^4 - T_env^4).

In engineering, the problem is often to determine the temperature field T(x,t) given boundary and initial conditions. In steady state, the heat equation reduces to ∇·(k ∇T) + Q = 0. In transient problems, ρ c ∂T/∂t = ∇·(k ∇T) + Q. Numerical methods, such as finite difference and finite element methods, are commonly used.

Applications include designing thermal insulation for buildings, cooling of electronic devices, heat exchangers in chemical processes, and many other systems where temperature control is important.