abkühlen

Abkühlen is a German verb meaning to become cooler or to cause something to cool down. It is commonly used for heated foods and liquids, but also for air, metal, or even emotions in a figurative sense. The word combines the prefix ab- with kühlen and is a separable verb in many tenses: ich kühle das Wasser ab; du kühlst ab; er kühlt ab; the past participle is abgekühlt. The noun Abkühlung refers to the process or the result of cooling.

In physics and engineering, Abkühlung describes the transfer of heat from a body to its surroundings, leading to a lower temperature. Heat can conduct through solids, convect in fluids, or radiate as electromagnetic energy. The rate of cooling depends on the temperature difference, surface area, material properties, and the surrounding medium. Newton's law of cooling models the rate of temperature change as dT/dt = -k (T - T_env).

In daily life, Abkühlen is encountered when cooking, food storage, metalworking, and electronics. After heating, foods are often cooled before refrigeration to reduce microbial growth; modern guidelines aim to reach refrigeration temperatures quickly and to minimize time in the temperature danger zone of roughly 4–60°C.

Atmospheric Abkühlung occurs when the air loses heat, through radiation to space, contact with cooler surfaces, or adiabatic expansion, which can cause fog, dew, or nightly cooling of air layers.