- 1. Subject: Engineering Thermodynamics Topic: Entropy Name: Nilrajsinh Vasandia Branch: Mechanical En No.:- 130990119060
- 2. Entropy • Entropy is a function of quantity of heat which shows the possibility of conversion of that heat into work. • The increase in the entropy is lower when heat is added at a high temperature and the increase in entropy is higher when heat is added at a low temperature • The maximum entropy means , there is minimum availability for conversion into work and the minimum entropy means , there is maximum availability for conversion into work.
- 3. • Consider the heating of working substance by reversible process. • Let heat supplied to the working substance in process which will increase the entropy by dS. • Heat supplied to reversible process Q TdsQ Where, T = absolute temperature, dS = Increse in entropy
- 4. Total heat supplied or absorbed Also, change in entropy dsTQ 2 1 2 1 T Q ds 2 1 2 1 T Q ds 2 1 12 T Q SS
- 5. Entropy & Disorder • Entropy can be considered to be a measure of microscopic disorder. • Work interaction can be considered ordered molecular energy. While heat interaction can be considered disordered molecular energy. • All irreversible processes are associated with a transition from ordered molecular energy to disordered molecular energy.
- 6. • Let us consider a box with a partition dividing it into two sections contains only O2 molecules in one section and only N2 molecules in the other section. • Now partition be withdrawn, allowing the two gases to mix. This process is irreversible ( since system can not be returned to its original state without taking work from surroundings ).This process is accompanied by an increase in entropy.
- 7. • The mixing process has resulted in a more random arrangement of the system, hence an increase in entropy can be associated with a change from a more ordered to less ordered, or more random state. The more a system approaches equilibrium, the greater is the disorder and irreversibility and when equilibrium is reached, it has the maximum disorder. • In other word, “entropy is a measure of the disorder of the system.” • A measure of molecular disorder can be found in a molecular mean free path. Thus, whenever there is an increase in the volume in the microscopic motion of the individual particles of matter, the entropy increases.
- 9. Characteristics of entropy • Entropy is property of system. • For reversible process change in entropy is • Entropy is point function, independent on path of the process. for reversible process for irreversible process T Q SS rev 2 1 12 0 gsurroundinsystem SS 0 gsurroundinsystem SS
- 10. • Entropy is extensive property. • It is expressed as energy units per unit degree temperature KJ/K.