lämmönhäviön

Lämmönhäviö, or heat loss, refers to the transfer of thermal energy from a hotter body to a cooler one, resulting in a reduction of the hotter body's temperature. In heat transfer theory, it is a key concept that underlies the design and operation of heating, ventilation, and air conditioning systems, as well as refrigeration, thermoelectric devices, and energy-efficient building envelopes. Heat can be lost by conduction through solid materials, convection to surrounding air or fluids, and radiation across a vacuum or transparent medium.

The magnitude of heat loss depends on several factors. Thermal conductivity and thickness of the material determine conductive losses. In convective processes, the temperature difference, surface area, and heat transfer coefficient – which itself is influenced by fluid velocity and properties – dictate the rate of loss. Radiative heat loss follows the Stefan‑Boltzmann law, with emissivity, temperature, and area as controlling parameters. Combining these mechanisms yields the total heat loss, often expressed as a heat flux (W/m²) or a U‑value in building science.

Accurate assessment of lämmönhäviö enables engineers to optimize insulation, select appropriate materials, and implement controls that reduce energy consumption. Modern simulation tools model heat loss across complex assemblies, allowing performance predictions over time. Understanding and minimizing heat loss is central to sustainability initiatives targeting reduced greenhouse gas emissions and improved indoor comfort.