Lämmöneritykseen

Lämmöneritykseen, also known as thermal conductivity, is a measure of a material's ability to conduct heat. It is defined as the amount of heat that flows through a material of given thickness and area exposed to a difference in temperature, divided by the area of the flow and the temperature difference.

The SI unit of thermal conductivity is watts per meter-kelvin (W/(m·K)). Other common units include BTU per hour-foot-degree Fahrenheit (BTU/(h·ft·°F)) and calories per second-centimeter-degree Celsius (cal/(s·cm·°C)).

The thermal conductivity of a material depends on its composition, structure, and temperature. In solids, thermal conductivity is primarily determined by the phonon transport, while in liquids and gases, it is influenced by molecular diffusion. In heterogeneous materials, thermal conductivity can be anisotropic, meaning it varies with direction.

Thermal conductivity is an important property in various fields, including engineering, materials science, and physics. It is crucial in the design of heat exchangers, insulation materials, and electronic devices. For example, the thermal conductivity of semiconductors affects the performance of electronic chips, while the thermal conductivity of building materials influences energy efficiency.

The thermal conductivity of materials can be measured using various techniques, such as the transient hot-wire method, the guarded hot-plate method, and the steady-state method. These methods involve applying a known heat flux to a material and measuring the resulting temperature difference.