chapter 2 properties of pure substances. pure substances fixed chemical composition –n2–n2...
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CHAPTER
2
Properties of Pure Substances
Pure Substances• Fixed chemical composition
– N2
– Air
• If mixed phases,– N2
– Not Air
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2-1
FIGURE 2-11T-v diagram for the heating process of water at constant pressure.
Saturated liquid
Saturated Vapor
Saturation Temperature, Tsat,at 1 atm pressure.
Fixed at a fixed pressure fora pure substance
Saturation pressure,Psat,
for 100°C
Latent heats and Phase Changes
• Latent heat of fusion (melting)
• Latent heat of vaporization (boiling)
• Magnitudes depend on temp. or press.
• Temp control by a boiling substance– Refrigerant-134a -- -26°C – Liquid nitrogen -- -196°C
• Vacuum cooling of vegetables– Quick but more expensive
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2-2
FIGURE 2-16T-v diagram of constant-pressurephase-change processes of a puresubstance at various pressures(numerical values are for water).
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2-3
FIGURE 2-18T-v diagram of a pure substance.
FIGURE 2-19P-v diagram of a pure substance.
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2-4
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2-5
FIGURE 2-21P-v diagram of a substance thatcontracts on freezing.
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2-6
FIGURE 2-22P-v diagram of a substance that expands on freezing (such as water).
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2-7
FIGURE 2-25P-T diagram of pure substances.
FIGURE 2-26P-v-T surface of a substance that contracts on freezing.
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2-8
FIGURE 2-27P-v-T surface of a substance that expands on freezing (like water).
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2-9
Instructor’s Visual AidsHeat Work and Energy. A First Course in Thermodynamics© 2002, F. A. Kulacki
Chapter 2 Module 2 Slide 13Additional Aspects for the P-V-T Surface for Water
Enthalpy...Enthalpy...
Instructor’s Visual AidsHeat Work and Energy. A First Course in Thermodynamics© 2002, F. A. Kulacki
Chapter 2 Module 2 Slide 14Additional Aspects for the P-V-T Surface for Water
Enthalpy definedEnthalpy defined
pvuh
pVUH