8/10/2019 Puresub 2_1

1/24

Thermodynamics Lecture Series

email: drjjlanita@hotmail.comhttp://www5.uitm.edu.my/faculties/fsg/drjj1.html

Applied Sciences Education Research Group

(ASERG)

Faculty of Applied Sciences

Universiti Teknologi MARA

Pure substances

Propertytables and Property

Diagrams

8/10/2019 Puresub 2_1

2/24

Quotes

You do not really understand somethingunless you can explain it to yourgrandmother.

(Albert Einstein)

8/10/2019 Puresub 2_1

3/24

Introduction

Objectives:1. State the meaning of pure substances

2. Provide examples of pure and non-pure

substances.3. Read the appropriate property table to

determine phase and other properties.

4. Sketch property diagrams with respect to thesaturation lines, representing phase and

properties of pure substances.

8/10/2019 Puresub 2_1

4/24

FIGURE 15

Some application areas of

thermodynamics.

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

1-1

Application

8/10/2019 Puresub 2_1

5/24

Example: A steam power cycle.

Steam

TurbineMechanical Energy

to Generator

Heat

Exchanger

Cooling Water

Pump

Fuel

Air

Combustion

Products

System Boundary

for Thermodynamic

Analysis

Steam Power Plant

8/10/2019 Puresub 2_1

6/24

Steam Power Plant

8/10/2019 Puresub 2_1

7/24

FIGURE 117

A control volume may involve fixed,

moving, real, and imaginary

boundaries.

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

1-5

Open system devices

8/10/2019 Puresub 2_1

8/24

Open system devices

Heat ExchangerThrottle

8/10/2019 Puresub 2_1

9/24

CHAPTER

2

Properties of Pure

Substances

Title:

8/10/2019 Puresub 2_1

10/24

Pure Substances

Pure substances Substance with fixed chemical composition

Can be single element: Such as, N2, H2, O2

Compound: Such as Water, H2O, C4H10,

Mixture such as Air,

2-phase system such as H2O.

Responsible for the receiving and removing dynamic

energy (working fluid)

8/10/2019 Puresub 2_1

11/24

Phase Change of Water

H2O

Sat.

liquid

Qin

P = 100 kPa

T = 99.6 C

Water interacts with thermal energy

99.6

2=f@100

kPa

T, C

30, m3/kg

1

H2O:C. liquid

P = 100 kPa

T = 30 C

Qin

8/10/2019 Puresub 2_1

12/24

Phase Change of Water

H2O

Sat.

liquid

Qin

P = 100 kPaT = 99.6 C

Water interacts with thermal energy

H2O:Sat. Liq.

Sat. Vapor

Qin

99.6

2=f@100

kPa

T, C

30

, m3/kg1

3

8/10/2019 Puresub 2_1

13/24

Phase Change of Water

Water interacts with thermal energy

4=g@100kPa

99.6

2=f@100

kPa

T, C

30

, m3/kg

1

3

P = 100 kPa

T = 99.6 C

H2O:

Sat. Vapor

Qin

H2O:Sat. Liq.

Sat. Vapor

Qin

8/10/2019 Puresub 2_1

14/24

Phase Change of Water

Water interacts with thermal energy

150

5

99.6

2=f@100kPa

T, C

30

, m3/kg

1

4=g@100kPa

3

5 = @100 kPa, 150C

3 = [f+ x fg]@100kPa1 = f@T1

H2O:

Super

Vapor

P = 100 kPa

T = 150 C

Qin

P = 100 kPa

T = 99.6 C

H2O:

Sat. Vapor

Qin

8/10/2019 Puresub 2_1

15/24

Phase Change of Water

Water interacts with thermal energy

H2O:Sat. Liq.

Sat. Vapor

P = 100 kPa

T = 99.6 C

Qin

P = 100 kPa

T = 99.6 C

H2O:

Sat. Vapor

Qin

P = 100 kPa

T = 150 C

H2O:

Super

Vapor

Qin

P = 100 kPa

T = 30 C

H2O:C. liquid

Qin

P = 100 kPa

T = 99.6 C

H2O

Sat.

liquid

Qin

8/10/2019 Puresub 2_1

16/24

Phase Change of Water

99.6

2=f@100kPa

T, C

30, m3/kg

1 4=g@100kPa

3

5 = @100 kPa, 150C

3

= [f

+ x f

g

]@100kPa

1 = f@T1

150

5 Compressed liquid: Good

estimation for properties

by taking y = yf@T where

y can be either , u, h or

s.

8/10/2019 Puresub 2_1

17/24

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2-1

FIGURE 2-11

T-v diagram for the

heating process of

water at constant

pressure.

8/10/2019 Puresub 2_1

18/24

Phase Change of Water

T, C

, m3

/kg

99.6

f@100kPa

g@100kPa

179.9

45.8

8/10/2019 Puresub 2_1

19/24

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2-2

FIGURE 2-16

T-v diagram of

constant-

pressure

phase-changeprocesses of a

pure

substance at

various

pressures

(numerical valuesare for water).

99.6

45.8

179.9

Tv diagram: Multiple P

8/10/2019 Puresub 2_1

20/24

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2-3

FIGURE 2-18

T-v diagram of a

pure substance.

Tv diagram: Multiple P

8/10/2019 Puresub 2_1

21/24

T, C

, m3/kg

Tv diagram - Example

70

=f@70 C= 0.001023

81.3

3.240

50 kPa

P, kPa T,C

50 70

Psat

, kPa Tsat

, C

81.33

Phase, Y?

Compressed Liquid,

T < Tsat

, m3/kg

f@70 C

8/10/2019 Puresub 2_1

22/24

Tv diagram - Example

T, C

, m3/kg

f@200 kPa

= 0.001061

P, kPa , m3/kg

200 1.5493

T- diagram

with respect to

the saturation

lines

Phase, Why?

Sup. V., >g

Psat

, kPa Tsat

, C

120.2

374.1

400

= 1.5493

120.23

g@200 kPa

= 0.8857

T, C

400

8/10/2019 Puresub 2_1

23/24

Tv diagram - Example

T, C

, m3/kg

P, kPa u, kJ/kg

1,000 2,000

T- diagram

with respect to

the saturation

lines

Phase, Why?

Wet Mix., uf < u < ug

Psat

, kPa Tsat

, C

179.9

374.1

f@1,000 kPa

= 0.001127

179.9

g@1,000 kPa

= 0.19444

T, C

179.9

= [f+ x fg]@1,000 kPa

8/10/2019 Puresub 2_1

24/24

Property Table

Saturated waterPressure table

Pressure

P, kPa

10

50

P, MPa

0.100

1.00

10

22.09

Specific internal energy,

kJ/kg

uf, kJ/kg ufg, kJ/kg ug, kJ/kg

191.82 2246.1 2437.9

340.44 2143.4 2483.9

417.36 2088.7 2506.1

761.68 1822.0 2583.6

1393.04 1151.4 2544.4

2029.6 0 2029.6

Specific volume,

m3/kg

f, m3/kg g, m

3/kg

0.001010 14.67

0.001030 3.240

0.001043 1.6940

0.001127 0.19444

0.001452 0.018026

0.003155 0.003155

Sat.

temp.

Tsat, C

45.81

81.33

99.63

179.91

311.06

374.14