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PROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCEPROPERTIES OF PURE SUBSTANCE

FACULTY OF MECHANICAL ENGINEERINGUNIVERSITI TEKNOLOGI MALAYSIASKUDAI, JOHOR, MALAYSIA THERMODYNAMICS

CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER 22222222

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• Pure Substance - one that is homogeneous and with the same chemical composition.

• Water and steam

• Not liquid and gaseous air

• Simple Compressible Substance – a substance whose changes in properties is dominated by the



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whose changes in properties is dominated by the effect of a volume change as opposed to surface, magnetic, electrical changes.

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Liquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid Water

Liquid WaterLiquid WaterLiquid WaterLiquid Water

Water VaporWater VaporWater VaporWater Vapor




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• Saturation Temperature – temperature at which vaporization takes place at a given pressure.place at a given pressure.

• Saturation Pressure – pressure at which vaporization takes place at a given temperature.

• Pressure Vapor Curve – plot of saturation temperature and pressure

Pressure

Pressure

Pressure

Pressure

Pressure Vapor Curve



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TemperatureTemperatureTemperatureTemperature

Pressure

Pressure

Pressure

Pressure

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Saturated Liquid – a substance that exists as a liquid at the saturation temperature

Pressure

Pressure

Pressure

Pressure

Pressure Vapor Curveliquid at the saturation temperature and pressure.

Subcooled Liquid or Compressed Liquid - a substance that exists as a liquid below the saturation temperature or pressure.

Saturated Vapor - a substance that exists as a vapor at the saturation temperature and pressure.


Pressure

Pressure

Pressure

Pressure



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pressure.Superheated Vapor - a substance that exists

as a vapor above the saturation temperature or pressure (all gases are superheated vapors). Liquid

Water

Water Vapor Water

VaporLiquid Water


Quality

Water Vapor

Water Vapor

Pressure

Pressure

Pressure

Pressure

Pressure Vapor Curve

Quality

x = (mass of vapor)/(total mass)



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Liquid Water

Water Vapor

Liquid Water


Pressure

Pressure

Pressure

Pressure

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• Start at a PStart at a PStart at a PStart at a P----T stateT stateT stateT state

• Increase Temperature at constant Increase Temperature at constant Increase Temperature at constant Increase Temperature at constant

pressurepressurepressurepressure

Temperature

Temperature

Temperature

Temperature


Saturated liquidSaturated liquidSaturated liquidSaturated liquid

Liquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid WaterLiquid Water






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VolumeVolumeVolumeVolume

Saturated vaporSaturated vaporSaturated vaporSaturated vapor

HEATHEATHEAT




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Temperature

Temperature

Temperature

Temperature



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Temperature

Temperature

Temperature

Temperature

Saturated liquidSaturated liquidSaturated liquidSaturated liquidSaturated vaporSaturated vaporSaturated vaporSaturated vapor

x=0 x=1

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vapliq VVV ++++==== gvapfliqvapliq vmvmVVV ++++====++++==== vapliq VVV ++++====

mV

v ====

gf xvx)v(v ++++−−−−==== 1

fgfg vvv −−−−====xvvv ++++====

gvapfliqvapliq vmvmVVV ++++====++++====

gvap

fliq v

m

mv

m

m

mV

v ++++========



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fgf xvvv ++++====

fg

f

v

vvx

also−−−−

====


• Start at a PStart at a PStart at a PStart at a P----T state (solid)T state (solid)T state (solid)T state (solid)

• Increase Temperature at constant Increase Temperature at constant Increase Temperature at constant Increase Temperature at constant


IceIceIceIce

Temperature

Temperature

Temperature

Temperature


Saturated liquidSaturated liquidSaturated liquidSaturated liquid

Saturated vaporSaturated vaporSaturated vaporSaturated vapor

WaterWaterWaterWaterWater Water Water Water

VaporVaporVaporVapor



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IceIceIceIce


WaterWaterWaterWaterVaporVaporVaporVapor

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TT TT



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VVVV




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Allotropic Transformations



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The state of a simple compressible pure substance can be defined by two independent properties, i.e. temperature and pressure, temperature and specific volume, etc.

Properties: T,p,v,u,h,s

To determine state: 2 Properties needed



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Find the specific volume of saturated steam with a quality of 50% at 100 C ?

(((( ))))1 xvvxv ++++−−−−==== xvvv ++++====



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(((( ))))(((( ))))(((( )))) (((( ))))(((( ))))(((( )))) (((( ))))83697

83645000522672901500104451

1

.v..v

....v

xvvxv gf

====++++====

++++−−−−====++++−−−−====

(((( )))) (((( ))))(((( ))))(((( )))) (((( ))))83697

8359250010446718515001044

.v..v

...v

xvvv fgf

====++++====++++====

++++====or

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Water at 27°C can exist in different phases dependent upon the pressure. Give the approximate pressure range in kPa for water being in each one of the three phases vapor, liquid or solid.



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Solution: Solution: The phases can be seen in Fig. 3.7, a sketch of which is shown to the right.

T = 27°C = 300 K From Fig. 3.7: PVL ~ 4 × 10-3 MPa = 4 kPa, PLS = 103 MPa

0 < P < 4 kPa VAPOR 0.004 MPa < P < 1000 MPa LIQUID P > 1000 MPa SOLID(ICE)



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P > 1000 MPa SOLID(ICE)

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You want a pot of water to boil at 105 oC. How heavy a lid should you put on the 15 cm diameter pot when Patm = 101 kPa?



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Two tanks are connected as shown in Fig. P3.49, both containing water. Tank A is at 200 kPa, v = 0.5 m3/kg, VA = 1 m3 and tank B contains 3.5 kg at 0.5 MPa, 400°C. The valve is now opened and the two come to a uniform state. Find the final specific volume. state. Find the final specific volume.



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A steel tank contains 6 kg of propane (liquid + vapor) at 20°C with a volume of 0.015 m3. The tank is now slowly heated. Will the liquid level inside eventually rise to the top or drop to the bottom of the tank? What if the initial mass is 1 kg instead of 6 kg? if the initial mass is 1 kg instead of 6 kg?



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A pressure cooker has the lid screwed on tight. A small opening with A = 5 mm2 is covered with a petcock that can be lifted to let steam escape. How much mass should the petcock have to allow boiling at 120 oC with an outside atmosphere at 101.3 kPa? outside atmosphere at 101.3 kPa?



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Substance that Expands on FreezingSubstance that Expands on Freezing



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Substance that Expands on Freezing



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Substance that Contracts on FreezingSubstance that Contracts on Freezing



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Substance that Contracts on Freezing



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Ideal Gas– gas molecules act as if they are independent of their where

T RnPV ====

are independent of their intermolecular forces.

TRMm

TRnPV

lb mol Rft lbf

R

kmol KkJ

.kmol KkN m

.R

kg/kmolkg

Mm

n

where

========

====

========

========

1545

3145831458



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RR

RTPv

PvMMmV

PmM

PV

TRM

TRnPV

====

====

====

====

========




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gas ideal an for 1====

========

Z

ZRT Pv or RTPv

Z

gas ideal an for 1====Z



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essurePrCritical PPP

P cc

r ========

emperatureCritical T TTT

T cc

r ========

Reduced Pressure

Reduced Temperature



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essurePrCritical PPP

P cc

r ========

emperatureCritical T TTT

T cc

r ========



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A spherical helium balloon of 10 m in diameter is at ambient T and P, 15oC and 100 kPa. How much helium does it contain? It can lift a total mass that equals the mass of displaced atmospheric air. How much mass mass that equals the mass of displaced atmospheric air. How much mass of the balloon fabric and cage can then be lifted?



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A 1 m3 rigid tank has propane at 100 kPa, 300 K and connected by a valve to another tank of 0.5 m3 with propane at 250 kPa, 400 K. The valve is opened and the two tanks come to a uniform state at 325 K. What is the final pressure? final pressure?



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Air in an automobile tire is initially at -10°C and 190 kPa. After the automobile is driven awhile, the temperature gets up to 10°C. Find the new pressure. You must make one assumption on your own.



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Carbon dioxide at 330 K is pumped at a very high pressure, 10 MPa, into an oil-well. As it penetrates the rock/oil the oil viscosity is lowered so it flows out easily. For this process we need to know the density of the carbon dioxide being pumped. carbon dioxide being pumped.



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Find the phase, quality x if applicable and the missing property P or T. a. H2O T = 120°C v = 0.5 m3/kg b. H2O P = 100 kPa v = 1.8 m3/kg c. H O T = 263 K v = 0.2 m3/kgc. H2O T = 263 K v = 0.2 m3/kg



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A piston/cylinder arrangement is loaded with a linear spring and the outside atmosphere. It contains water at 5 MPa, 400°C with the volume being 0.1 m3. If the piston is at the bottom, the spring exerts a force such that P = 200 kPa. The system now cools until the pressure reaches that Plift = 200 kPa. The system now cools until the pressure reaches 1200 kPa. Find the mass of water, the final state (T2, v2) and plot theP–v diagram for the process.



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A cylinder has a thick piston initially held by a pin as shown in the figure. The cylinder contains carbon dioxide at200 kPa and ambient temperature of 290 K. The metal piston has a density of8000 kg/m3 and the atmospheric pressure is101 kPa. The pin is now removed, allowing the atmospheric pressure is101 kPa. The pin is now removed, allowing the piston to move and after a while the gas returns to ambient temperature. Is the piston against the stops?



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thermo chapter 2 - properties of pure substancemazlan/?download=thermo chapter 2 - properties of...

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