TEMPERATURE ENTROPY AND PRESSURE ENTHALPY CHARTS

 TEMPERATURE ENTROPY AND PRESSURE ENTHALPY CHARTS

TEMPERATURE ENTROPY CHART

As entropy is a thermodynamic parameter (property) like other thermodynamic parameters namely internal energy/enthalpy, it is used as abscissa (x –co-ordinate) and ABSOLUTE temperature as the ordinate. This chart is very useful in comparing the performance of various heat engine and refrigeration cycles.Although entropy is an extensive (depends on mass) thermodynamic property and its concept comes from the second law of thermodynamics (Clausius inequality). Conventionally it is in maximum use as an intensive property in k J/kg K.

 

Constant Pressure Line is ABCD

Another Constant Pressure Line is EFGH

Constant temperature Line is Horizontal.

Constant Entropy Line is Vertical.

Area on this diagram heat quantity.

 

  1. PRESSURE ENTHALPY CHART

This chart is useful for the analysis of refrigeration and steam cycles.

p-h chart contains

(i) Iso-thermal lines

vertical in sub-cooled region

horizontal in two phase region

curve like in super-heated region

FGHI is Constant Temperature line.

JKLM is another Constant Temperature Line.

(ii) Constant pressure lines—————Horizontal Lines

(iii) Constant  specific entropy lines——– more Inclined to horizontal and are

plotted in the super-heated region

NO and PQ are Constant Entropy Lines.

(iv) Constant specific volume lines————-less inclined to horizontal and are

in the super-heated region.

RS and TU are Constant Specific Volume Lines.

(v) Vertical Lines are Constant Enthalpy Lines.

(vi) Critical Point—–Point ‘C’ is the critical point.

(vii) Saturated Liquid Line—–Curve ABC is saturated liquid line.

(viii) Saturated vapor Line—–Curve CDE is the saturated vapor line.

(ix) SUB-COOLED REGION—Towards left of Saturated Liquid Line.

(x) TWO-PHASE REGION—In between Saturated Liquid Line and Saturated Vapor Line.

(xi) SUPER-HEATED REGION——–Towards Right of Saturated Vapor Line.

(xii) GASES REGION———Towards Right of Saturated Vapor Region where Degree of Super-heat is >500C

REFERENCES

  1. Chemical Thermodynamics, D.J.G. Ives, University Chemistry, MacDonald Technical and Scientific, 1971
  2. Elements of Statistical Thermodynamics (2nd Edition), L.K. Nash, Addison-Wesley, 1974
  3. Thermal Physics (2nd Edition), Kittel, Charles & Kroemer, Herbert (1980).
  4. Encyclopedia of Physics (2nd Edition, W. H. Freeman Company. McGraw Hill,”), C.B. Parker, 1994
  5. Thermodynamics – an Engineering Approach , Cengel, Yunus A., & Boles, Michael A, McGraw Hill, 2002
  6. Statistical Physics (2nd Edition), F. Mandl, Manchester Physics, John Wiley & Sons, 2008
  7. Thermodynamics, From Concepts to Applications (2nd Edition), A. Shavit, C. Gutfinger, CRC Press (Taylor and Francis Group, USA), 2009