TITLE.PM5

58 ENGINEERING THERMODYNAMICS

dharm
M-therm/th2-2.pm5

= 10^5 × 20 × 0.0025

1

0.05

1

0.1

FHG − IKJ = 50000 Nm

Work done on fluid from 2 to 3

= Area 32ML3 = p 2 (V 2 – V 3 ) = 10^5 × 5 × (0.1 – 0.05) = 25000 Nm

Work done during the process 3-1

= 0, because piston is locked in position (i.e., Volume remains constant)

∴ Net work done by the fluid

= Enclosed area 1231 = 50000 – 25000

= 25000 Nm. (Ans.)

Highlights

1. Thermodynamics is an axiomatic science which deals with the relations among heat, work and properties
   of systems which are in equilibrium. It basically entails four laws or axioms known as Zeroth, First, Second
   and Third law of thermodynamics.


2. A system is a finite quantity of matter or a prescribed region of space.
   A system may be a closed, open or isolated system.


3. A phase is a quantity of matter which is homogeneous throughout in chemical composition and physical
   structure.


4. A homogeneous system is one which consists of a single phase.


5. A heterogeneous system is one which consists of two or more phases.


6. A pure substance is one that has a homogeneous and invariable chemical composition even though there
   is a change of phase.


7. A system is in thermodynamic equilibrium if temperature and pressure at all points are same ; there should
   be no velocity gradient.


8. A property of a system is a characteristic of the system which depends upon its state, but not upon how the
   state is reached.
   Intensive properties do not depend on the mass of the system.
   Extensive properties depend on the mass of the system.


9. State is the condition of the system at an instant of time as described or measured by its properties. Or each
   unique condition of a system is called a state.


10. A process occurs when the system undergoes a change in state or an energy transfer takes place at a steady
    state.


11. Any process or series of processes whose end states are identical is termed a cycle.


12. The pressure of a system is the force exerted by the system on unit area of boundaries. Vacuum is defined
    as the absence of pressure.


13. A reversible process is one which can be stopped at any stage and reversed so that the system and
    surroundings are exactly restored to their initial states.
    An irreversible process is one in which heat is transferred through a finite temperature.


14. Zeroth law of termodynamics states that if two systems are each equal in temperature to a third, they are
    equal in temperature to each other.


15. Infinite slowness is the characteristic feature of a quasi-static process. A quasi-static process is a succession
    of equilibrium states. It is also called a reversible process.