## 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.

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