säteilylämpötilan

Säteilylämpötila is a Finnish term that translates to "radiant temperature" or "effective temperature" in English. It refers to the temperature that a surface would have if it were in thermal equilibrium with its surroundings, considering only radiative heat exchange. This concept is particularly relevant in understanding how objects exchange heat through electromagnetic radiation.

Unlike air temperature, which measures the kinetic energy of air molecules, radiant temperature accounts for the influence of surrounding surfaces' temperatures on an object's heat balance. For example, on a cold day, even if the air temperature is moderate, standing near a cold window will make you feel colder because the window is radiating heat away from you. Conversely, standing in direct sunlight on a cool day, you might feel warm because the sun is radiating heat towards you, even if the ambient air temperature is low.

Radiant temperature is calculated based on the temperature of surrounding surfaces, their emissivity, and the surface area and absorptivity of the object in question. It is a crucial factor in thermal comfort assessments, especially in environments where radiative heat transfer is significant, such as buildings with large windows, industrial settings, or even outdoor environments. Understanding radiant temperature helps in designing more comfortable and energy-efficient spaces by managing the sources and sinks of radiative heat. It plays a role in fields like building physics, HVAC (heating, ventilation, and air conditioning) design, and ergonomics.