1 / 15

ES 202 Fluid and Thermal Systems Lecture 16: Property Tables (1/20/2003)

ES 202 Fluid and Thermal Systems Lecture 16: Property Tables (1/20/2003). Assignments. Homework: 3-56, 3-57, 5-72 in Cengel & Turner Reading assignment Tables A-4 to A-14 in Cengel & Turner. Announcements. Homework set #5 due by 5 pm today in my office Comments on Exam 1

uriah
Download Presentation

ES 202 Fluid and Thermal Systems Lecture 16: Property Tables (1/20/2003)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ES 202Fluid and Thermal SystemsLecture 16:Property Tables(1/20/2003)

  2. Assignments • Homework: • 3-56, 3-57, 5-72 in Cengel & Turner • Reading assignment • Tables A-4 to A-14 in Cengel & Turner ES 202 Fluid & Thermal Systems

  3. Announcements • Homework set #5 due by 5 pm today in my office • Comments on Exam 1 • Problem 1: difference between static and stagnation pressure, straws serve as frictional pipe • Problem 2: hydrostatic pressure distribution in vertical and horizontal directions, centroid, center of pressure, moment analysis • Problem 3: mechanical energy balance, major loss, minor loss • Session 5: max = 91, min = 31, average = 61 • Session 6: max = 90, min = 44, average = 67 • Mid-term grade based on Exam 1 score on an absolute scale • Keep your heads up, we still have much to learn and improve! ES 202 Fluid & Thermal Systems

  4. Road Map of Lecture 16 • Quiz on Lecture 15 • Phase determination in various regions • Data interpolation • linear • bi-linear • Compressed Liquid Approximation • Practice with property tables ES 202 Fluid & Thermal Systems

  5. Quiz on Lecture 15 • True/False Temperature and pressure are independent in the two-phase region. • False • However, they are independent of each other in the compressed liquid and superheated vapor regions. • Apart from temperature, name at least three other independent, intensive properties in the two-phase region. • u, h, s, v, x • Give the definition of quality • mass fraction of vapor in mixture ES 202 Fluid & Thermal Systems

  6. Quiz on Lecture 15 (Cont’d) • In the two-phase region, most intensive properties can be expressed as a mass-weighted/volume-weighted average of the saturated liquid and saturated vapor values. • mass-weighted average • in terms of equation: where q is the intensive counterpart of any extensive property like internal energy, enthalpy, entropy and volume. ES 202 Fluid & Thermal Systems

  7. T > Tsat(P) T = Tsat(P) T < Tsat(P) Phase Determination (Case 1) • Case 1: Given P and T • Look up saturation table • Compare given P and T against saturation values in the table • In pressure table, • Recall constant pressure line on T-v diagram • If T < Tsat(P), compressed liquid. • If T = Tsat(P), saturated liquid-vapor mixture. • If T > Tsat(P), superheated vapor. ES 202 Fluid & Thermal Systems

  8. P > Psat(T) P = Psat(T) P < Psat(T) Phase Determination (Case 1 Cont’d) • Case 1: Given P and T • Look up saturation table • Compare given P and T against saturation values in the table • In temperature table, • Recall constant temperature line on P-v diagram • If P > Psat(T), compressed liquid. • If P = Psat(T), saturated liquid-vapor mixture. • If P < Psat(T), superheated vapor. ES 202 Fluid & Thermal Systems

  9. (1) (2) (3) (4) Psat (5) vf(P) vg(P) Phase Determination (Case 2) • Case 2: Given P (or T) and v (or u, h, s) • Look up saturation table • Find saturated liquid and vapor values for v (or u, h, s) at Psat = P • If v < vf(Psat), compressed liquid. • If v = vf(Psat), saturated liquid. • If vf(Psat)< v < vg(Psat), saturated liquid-vapor mixture. • If v = vg(Psat), saturated vapor. • If v > vg(Psat), superheated vapor. ES 202 Fluid & Thermal Systems

  10. Summary • Compressed liquid (quality is undefined, any two intensive thermodynamic properties suffice) • Saturated liquid ( x = 0 ) • Saturated liquid-vapor mixture ( 0 < x < 1 ) • Saturated vapor ( x = 1 ) • Superheated vapor (quality is undefined, any two intensive thermodynamic properties suffice) ES 202 Fluid & Thermal Systems

  11. Determine phase of substance Compressed liquid Two-phase Superheated vapor Direct look up Determine quality Direct look up Interpolate other properties Flow Chart ES 202 Fluid & Thermal Systems

  12. Property Tables • Compressed liquid water (A-7) • Saturated water • temperature (A-4) • pressure (A-5) • Superheated water (A-6) ES 202 Fluid & Thermal Systems

  13. Data Interpolation • The property tables only tabulate discrete values for pressure or temperature as the independent property. • If you are interested in values which do not fall on the tabulated data points, interpolation within the “sandwich” interval will be necessary. • Since the property tables report data at small intervals, linearinterpolation should be adequate for most purposes. • Example: specify T (not tabulated) and x in two-phase region • If both independent, intensive thermodynamic properties do not fall on the tabulated data points, bi-linear interpolation is necessary to completely specify the thermodynamic states. • Example: specify P and T in superheated vapor region (both not tabulated) ES 202 Fluid & Thermal Systems

  14. (weak function of T) Compressed Liquid Approximation • If you find • the substance is a compressed (subcooled) liquid; • the compressed liquid table is unavailable or inadequate, you may invoke the compressed liquid approximation: ES 202 Fluid & Thermal Systems

  15. Exercise with property tables ES 202 Fluid & Thermal Systems

More Related