ES 202 Fluid and Thermal Systems Lecture 15: Properties in Two-Phase Region (1/16/2003)

1. ES 202Fluid and Thermal SystemsLecture 15:Properties in Two-Phase Region(1/16/2003)

2. Assignments • Homework: • 3-28, 3-29 in Cengel & Turner • Reading assignment • Tables A-4 to A-14 in Cengel & Turner ES 202 Fluid & Thermal Systems

3. Announcements • More on Lab 2 write-up • due tomorrow • no length limit • Contents: water wall, Torricelli experiment, pipe friction • data interpretation • Problem session today at 7 pm in O167 • show outline • Bring your text book to class next Monday ES 202 Fluid & Thermal Systems

4. Road Map of Lecture 15 • Review of Lecture 14 • Phase diagram • familiarity with terminology • familiarity with various regions • Focus on two-phase dome • dependency between temperature and pressure • new property: quality • Exercise on properties table ES 202 Fluid & Thermal Systems

5. Review of Lecture 14 • What is the State Principle? • Identify the regions on the P-v, T-v planes ES 202 Fluid & Thermal Systems

6. Working with P-v, T-v Diagrams • Compressed liquid • Superheated vapor • The two-phase (vapor) dome • Saturated liquid line • Saturated vapor line • Critical point • Trace a constant pressure curve on the T-v diagram • how it relates to the ideal gas model • in what direction is pressure increasing? • Trace a constant temperature curve on the P-v diagram • how it relates to the ideal gas model • in what direction is temperature increasing? ES 202 Fluid & Thermal Systems

7. increasing direction of pressure constant pressure line T-v Diagram Critical Point Compressed liquid Superheated vapor Two-phase dome Saturated vapor line Saturated liquid line ES 202 Fluid & Thermal Systems

8. increasing direction of temperature constant temperature line P-v Diagram Critical Point Superheated vapor Compressed liquid Two-phase dome Saturated liquid line Saturated vapor line ES 202 Fluid & Thermal Systems

9. vapor liquid Illustration of Two-Phase Mixture • Imagine a heating process in a cylinder with a constant weight as a lid (closed system; control mass) } mixture of liquid and vapor heating ES 202 Fluid & Thermal Systems

10. The Two-Phase Dome • A mixture of liquid and vapor • Temperature and pressure are NOT independent in the two-phase dome • one specifies the other (reference to P-v diagram, table) • example: boiling point of water at different altitudes • need another independent property to completely specify the state: • concept of quality ES 202 Fluid & Thermal Systems

11. g f d D Introducing Quality • Definition: mass fraction of vapor in the mixture • Geometric interpretation: • Serves as another independent thermodynamic variable in the “Two-phase dome” ES 202 Fluid & Thermal Systems

12. Significance of Quality • Define properties in the “Two-Phase dome” • For example: • extensive property: internal energy • using quality, its intensive counterpart can be expressed as a mass-weighted average of the saturated liquid and saturated vapor values • internal energy in the above example can be replaced by any other extensive property, e.g. enthalpy, volume, entropy, etc. ES 202 Fluid & Thermal Systems

13. Saturated Temperature, Pressure Tables • Show saturated water – temperature table (Table A-4) • indicate dependency between temperature and saturation pressure • indicate saturated liquid and saturated vapor values for various intensive properties • Show saturated water – pressure table (Table A-5) • indicate dependency between pressure and saturation temperature • indicate saturated liquid and saturated vapor values for various intensive properties ES 202 Fluid & Thermal Systems