Page 12 - BASIC CONCEPTUAL OF THERMOFLUID

CHAPTER 1: CONCEPTUAL PRINCIPLE IN THERMOFLUIDS

1.6.2 State and Equilibrium

Since there are normally relations among the properties of a system, the state often can be specified by
providing the values of a subset of the properties. Refers to the condition of system as described by its
properties. As seen in the Fig. 8 below showing the properties of two difference state for thermodynamics
systems.

Fig. 8: A set of properties that describe the condition

Thermodynamic system will be considered in thermodynamic equilibrium, if system is meeting the
condition of the three important types of equilibrium which is mechanical equilibrium, thermal equilibrium
and chemical equilibrium.

1.6.2.1 Mechanical Equilibrium

A system will be considered in the state of mechanical equilibrium if there is no unbalanced force
within the system or between system and its surrounding. Pressure must be same at each point
within the system and should not vary with respect to time.

If there is presence of unbalanced force within the system or between system and its
surrounding, then system will not be considered in the state of mechanical equilibrium and in this
situation only system or system and its surrounding will go through state change for securing the
state of mechanical equilibrium.

1.6.2.2 Thermal Equilibrium
In order to consider a system in the state of thermal equilibrium, temperature must be same at
each point within the system and should not vary with respect to time. If system is not meeting
this criterion, in that situation system will go through state change for securing the state of thermal
equilibrium.

1.6.2.3 Chemical Equilibrium

In order to consider a system in the state of chemical equilibrium, if there is no chemical reaction
taking place within the system and chemical composition of the system is not changing with
respect to time.

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