adiabatic process

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Adiabatic process

A thermodynamic process in which the system undergoing the change exchanges no heat with its surroundings. An increase in entropy or degree of disorder occurs during an irreversible adiabatic process. However, reversible adiabatic processes are isentropic; that is, they take place with no change in entropy. In an adiabatic process, compression always results in warming, and expansion always results in cooling. See Entropy, Isentropic process

During an adiabatic process, temperature changes are due to internal system fluctuations. For example, the events inside an engine cylinder are nearly adiabatic because the wide fluctuations in temperature take place rapidly, compared to the speed with which the cylinder surfaces can conduct heat. Similarly, fluid flow through a nozzle may be so rapid that negligible exchange of heat between fluid and nozzle takes place. The compressions and rarefactions of a sound wave are rapid enough to be considered adiabatic. See Sound, Thermodynamic processes

adiabatic process

(ad-ee-ă-bat -ik) A process that takes place in a system with no heat transfer to or from the system. In general, a temperature change usually occurs in an adiabatic process.

Adiabatic Process

 

a process, occurring in a physical system, in which no heat is exchanged with the surroundings. An adiabatic process can occur in a system surrounded by a heat-insulating (adiabatic) enclosure. One such example is the power stroke of a heat engine, where the gas or vapor expands in a cylinder with heat-insulating walls and piston, in the absence of irreversible conversion of friction into heat.

An adiabatic process can also be achieved in the absence of an adiabatic enclosure. In that case, the process must occur so rapidly that there is no time for any exchange of heat between the system and its surroundings. That happens, for example, when a gas is compressed by a shock wave, where the gas, having no time to give off the heat released, heats up vigorously. When the wave moves at a speed of about 1 km/sec (a speed attained by modern supersonic airplanes) and compresses the air fourfold, the air temperature rises to 700°C. Adiabatic expansion of the gas with the carrying out of work against external forces and the forces of mutual molecular attraction causes the gas to cool. This method of cooling gases is the basis of the gas liquefaction process. The adiabatic process of demagnetization of paramagnetic salts makes it possible to attain temperatures close to absolute zero.

An adiabatic process can be either reversible or irreversible. In the case of the reversible adiabatic process, the entropy of the system remains constant. A reversible adiabatic process is therefore called isoentropic. On a phase diagram of the system it is represented by an adiabatic curve or by an isoentropic curve. In an irreversible adiabatic process the entropy increases.

adiabatic process

[¦ad·ē·ə¦bad·ik prä·səs]
(thermodynamics)
Any thermodynamic procedure which takes place in a system without the exchange of heat with the surroundings.
References in periodicals archive ?
We should note that the assumed implicit adiabatic heating through the use of the reference curve as input may not represent correctly the self-heating of all the tests presented above.
The proposed simple phenomenological model, which requires a small computational time, describes well the thermomechanical response of polymeric materials, under a wide range of strain rates and temperatures, and allows for the evaluation of the interfacial stress as well the [beta] factor for adiabatic heating.
Adiabatic heating is due to the nature of the deformation resulting in heat dissipation which depending on the temperature and strain rate may produce a temperature rise in the specimen during stretching.
13b) thus indicating adiabatic heating of the stretched specimen.
For a rigorous analysis of stress-strain data from biaxial test rigs at high strain rates this adiabatic heating effect needs to be accounted for.
The adiabatic heating failure of PVC was not anticipated from the failure mechanism diagrams or the impact grinding studies at apparently higher strain rates.
Taylor tests at room temperature show adiabatic heating for PVC and brittle fracture for PET.
Effects of light scattering and attenuation due to crystallization of polyethylene, the influence of packing pressure on crystallization kinetics and adiabatic heating, and viscoelastic volume relaxation of polystyrene as it approaches [T.
p] is specific heat, k is thermal conductivity and [Mathematical Expression Omitted] is the rate of heat generated by crystallization and by adiabatic heating and cooling, i.
The effects of the applied packing pressure will be seen in the thermal diffusion equation via the Avrami rate constant K and adiabatic heating [Mathematical Expression Omitted].
For the adiabatic heating experiments, the gasket was suspended in a beaker to minimize convective losses caused by the fan in the microwave.
Figure 2 shows typical temperature histories for adiabatic heating of the 50% PANI and 60% PANI gaskets.

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