7.7 The Tds Relations

The T-ds equations...

The T-dS equations Note that the specific heats are generally a function of temperature.

Isentropic processes - ideal gases v

7.9 The Entropy Change of Ideal Gases

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-36 The isentropic relations of ideal gases are valid for the isentropic processes of ideal gases only.

7.10 Reversible Steady-Flow Work

FIGURE 7-43 Schematic and T-s diagram for Example 6–12. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-43 Schematic and T-s diagram for Example 6–12.

7.11 Minimizing the Compressor Work

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-45 P-v diagrams of isentropic, polytropic, and isothermal compression processes between the same pressure limits.

Multistage Compression with Intercooling

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-46 P-v and T-s diagrams for a two-stage steady-flow compression process.

7.12 Isentropic Efficiencies of Steady-Flow Devices

Isentropic efficiency Common open system components Nozzles Compressors Turbines Pumps The concept of isentropic efficiency comes from the combination of the 1st and 2nd Laws.

h-s diagram Isentropic process, s = constant, Maximum enthalpy change., p1 p2 1 2 h s s1 = s2 Al accessible states lie to the right of this line.

Isentropic efficiency h s p2 p1 h2,s h2 h1 Isentropic expansion, entropy production is zero. Actual expansion, h2 < h2,s

Turbines and compressors Irreversible h s p2 > p1 Compressor Turbine Reversible, adiabatic Reversible, adiabatic

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-49 The h-s diagram for the actual and isentropic processes of an adiabatic turbine.

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-51 The h-s diagram of the actual and isentropic processes of an adiabatic compressor.

FIGURE 7-53 Schematic and T-s diagram for Example 6–15. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-53 Schematic and T-s diagram for Example 6–15.

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. FIGURE 7-54 The h-s diagram of the actual and isentropic processes of an adiabatic nozzle.