Kokonaislämpösiirron

Kokonaislämpösiirron, often translated as overall heat transfer or U-value in English, quantifies the rate of heat transfer through a material or a composite structure. It represents the amount of heat energy that passes through a unit area of a material when there is a unit temperature difference across it. The unit of kokonaislämpösiirron is typically watts per square meter per Kelvin (W/(m²·K)).

A lower kokonaislämpösiirron value indicates better insulation, meaning less heat is transferred. Conversely, a higher value signifies poorer insulation and greater heat loss or gain. This concept is crucial in various fields, particularly in building construction and engineering, where it is used to assess the thermal performance of walls, windows, roofs, and other building components. By understanding and minimizing kokonaislämpösiirron, energy efficiency can be improved, leading to reduced heating and cooling costs and a more comfortable indoor environment.

In practical applications, kokonaislämpösiirron is determined by considering the thermal resistance of all layers within a structure, including the materials themselves, air gaps, and surface resistances. The reciprocal of the total thermal resistance gives the kokonaislämpösiirron. For example, in a building, heat transfer occurs through convection and radiation at the surfaces and conduction through the materials. These resistances are summed to find the total resistance, and its inverse is the kokonaislämpösiirron of that particular building element.