Thermodynamics

Thermodynamic Process

Thermodynamic process is a way of changing one or more of the properties in a system resulting in a change of the state of the system. The following summarizes some of the more common processes (Figure 06a) :

Adiabatic Process - This is a process that takes place in such a manner that no heat enters or leaves a system. Such change may be accomplished either by surrounding the system with a thick layer of heat insulating material or by performing the process quickly. The flow of heat is a fairly slow process; so that any process performed quickly enough will be practically adiabatic. The compression and expansion phases of a gasoline engine is an example of an approximately adiabatic process.

Isochoric Process - If a system undergoes a change in which the volume remains constant, the process is called isochoric. The explosion of gasoline vapor and air in a gasoline engine may be treated as though it were an isochorie addition of heat

Figure 06a Thermodynamic Processes [view large image]

Isobaric Process - A process taking place at constant pressure is call an isobaric process. When water enters the boiler of a steam engine and is heated to its boiling point, vaporized, and then the steam is superheated, all these processes take place isobarically.

Isothermal Process - Isothermal process changes the system slowly so that there is enough time for heat flow to maintain a constant temperature. Slow change is a reversible process, because at any instant the system is in its most probable configuration. In general, a process will be reversible if:
1. it is performed quasistatically (slowly);
2. it is not accompanied by dissipative effects, such as turbulence, friction, or electrical resistance.

Isentropic Process - If the slow change is accomplished in an insulated container, there is no heat flow. According to
Eq.(4) there is also no change in entropy. Thus, a reversible adiabatic process is isentropic.

Irreversible Process - The process is irreversible because of dissipative effects (such as turbulence, friction, or electrical resistance), for then extra work must be provided to overcome the dissipation.

Thermodynamics

Thermodynamic Process

Figure 06a Thermodynamic Processes [view large image]

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