Lecture 6 – Entropy Nick DiFilippo. Review of Last Class Entropy Ways to find Entropy Entropy...

Lecture 6 – Entropy Nick DiFilippo

Review of Last Class• Entropy• Ways to find Entropy• Entropy Change• Incompressible• Ideal Gas• Tables

• Reversible Process

Entropy Balance Closed System

Developing Entropy balance for a Closed System

Energy Balance Interpretation• Entropy Transfer• Entropy Production

Example 6.2

Closed System Entropy Rate Balance

Closed System Entropy Rate Balance

Gearbox Example

Increase of Entropy Principle• Entropy change of a system can be negative during a process, but entropy

generation cannot be. • Processes occur only in such a direction that the total entropy of the system

plus surroundings increases

Entropy Balance for Control Volumes

Rate Balances for Control Volumes at Steady State

(4.18)

(4.6)

(6.36)

Isentropic Process• Constant Entropy• Ideal Gas Model

Isentropic Process Constant Specific Heat

Isentropic Efficiencies of Industrial Devices• Turbines

Work per unit Mass

Nozzle

(neglect )

Compressors and Pumps

Internally Reversible, Steady State Flow Processes

Work in a Polytropic Process

Ideal Gas