adiabattisessa

Adiabattisessa is a Finnish term used to describe something occurring in or relating to an adiabatic process. It is the inessive form of the adjective adiabattinen and is commonly found in phrases such as adiabattisessa prosessissa (in the adiabatic process) or adiabattisessa tilassa (in the adiabatic state).

In thermodynamics, an adiabatic process is one in which no heat is exchanged with the surroundings (Q = 0). According to the first law, the change in internal energy satisfies dU = -PdV for a closed system. For an ideal gas, a reversible adiabatic process leads to PV^γ = constant, where γ = Cp/Cv. Other characteristic relations include TV^(γ−1) = constant and TP^(1−γ) = constant. It is important to note that the PV^γ = constant relation strictly applies to reversible adiabatic (isentropic) processes; in irreversible adiabatic processes, Q = 0 still holds but entropy can increase, and the simple PV^γ = constant relation may not apply.

Applications of the concept include the analysis of engines, compressors, turbines, and insulating systems where heat transfer is minimized. The idea also appears in meteorology and atmospheric science, where adiabatic expansion and compression of air are used to describe vertical motion and related temperature changes, such as the adiabatic lapse rate.

Etymology stems from the Greek roots meaning “not passing through,” reflecting the notion of no heat transfer. In Finnish scientific writing, adiabattinen and its inflected forms such as adiabattisessa prosessissa are used to convey the adiabatic constraint within a system.