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ENTC 370: Announcements

ENTC 370: Announcements. Homework assignments No.3: Assigned Problems: 3.17, 3.26, 3.29, 3.30, 3.34, 3.44, 3.61, 3.75, 3.78, 3.81. Due Tuesday, September 30 th before 10:50 am For more information, go to: http://etidweb.tamu.edu/classes/entc370. ENTC 370: Announcements. Exam I:

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ENTC 370: Announcements

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  1. ENTC 370: Announcements • Homework assignments No.3: • Assigned Problems: • 3.17, 3.26, 3.29, 3.30, 3.34, 3.44, 3.61, 3.75, 3.78, 3.81. • Due Tuesday, September 30th before 10:50 am • For more information, go to: • http://etidweb.tamu.edu/classes/entc370

  2. ENTC 370: Announcements • Exam I: • Tuesday (Oct 21st) or Thursday (Oct 23rd ) • Chapters 1 – 5 • Homeworks1 – 5 • Closed book/closed notes • Students will be allowed to bring own equation sheet • Double-sided is ok • Size: 8½ x 11 • Bring calculator

  3. Heating Process of Water at Constant Pressure SHV CL T All vapor → ← all liquid SV SL MX States 2,3 & 4: Same T & P Sat liquid n ← vapor Sat vapor → ← liquid

  4. Water: Liquid-Vapor Saturation Temperature and Pressure Liquid Gas or Vapor

  5. Property Diagrams for Phase-Change Process Critical Point: Saturated Liquid and Vapor States are indistinguishable Tsat LHV decreases with Pressure

  6. Property Diagrams for Phase-Change Process (T-v Diagram)

  7. Example • A piston-cylinder device contains 2 ft3 of saturated water vapor at 50 psia. • Determine the temperature and the mass of the vapor inside the cylinder. Facts and Assumptions:

  8. What should I do if I do not find the exact values in the tables? • Example: → Psat= 115 kPa, what is Tsat? • Interpolation is required: Property 1Property 2 A X B Y←Unknown value C Z

  9. Interpolation A X B Y C Z Then, solve for Y: You will use interpolation many times in this course!

  10. Example • A mass of 200 g of saturated liquid water is completely vaporized at a constant pressure of 100 kPa. Determine (a) the volume change and (b) the amount of energy added to the water. hfgis called the enthalpy of vaporization (or latent heat of vaporization). Represent the amount of energy per unit of mass at constant pressure. Facts and Assumptions:

  11. The two-phase region for water MX http://www.aplusphysics.com/courses/honors/thermo/phase_changes.html

  12. Saturated Liquid-Vapor Mixture (MX) During vaporization: part liquid-part vapor Quality of Steam: x = 0.0 (saturated liquid) 0.0 < x < 1.0 (mixture) x = 1.0 (saturated vapor)

  13. Quality defined P and T remain constant during phase change process Quality, x, allows location of states inside the vapor-liquid region.

  14. Example • A container holds a 1 kg of SV-Water and 9 kg of SL-Water and the pressure inside is 200 kPa. Determine the enthalpy of the fluid.

  15. Example • A rigid tank contains 10 kg of water at 90° C. If 8 kg of the water is in liquid form and the rest in the vapor form, determine (a) the pressure in the tank and (b) the volume in the tank.

  16. Example • An 80 L vessel contains 4 kg of R 134-a at a pressure of 160 kPa. Determine the temperature, quality (x), enthalpy and volume occupied by vapor phase.

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