Microsoft Word - Cengel and Boles TOC _2-03-05_.doc

Property tables are also available for saturated solid–vapor mixtures.

Properties of saturated ice–water vapor mixtures, for example, are listed in

Table A–8. Saturated solid–vapor mixtures can be handled just as saturated

liquid–vapor mixtures.

2 Superheated Vapor

In the region to the right of the saturated vapor line and at temperatures

above the critical point temperature, a substance exists as superheated vapor.

Since the superheated region is a single-phase region (vapor phase only),

temperature and pressure are no longer dependent properties and they can

conveniently be used as the two independent properties in the tables. The

format of the superheated vapor tables is illustrated in Fig. 3–40.

In these tables, the properties are listed against temperature for selected

pressures starting with the saturated vapor data. The saturation temperature

is given in parentheses following the pressure value.

132 | Thermodynamics

be determined by comparing a suitable property to the saturated liquid and

saturated vapor values. From the information given, we can determine the

specific volume:

At 160 kPa, we read

(Table A–12)

Obviously, vf
 v
 vg, and, the refrigerant is in the saturated mixture

region. Thus, the temperature must be the saturation temperature at the

specified pressure:

(b) Quality can be determined from

(c) At 160 kPa, we also read from Table A–12 that hf31.21 kJ/kg and hfg

209.90 kJ/kg. Then,

(d) The mass of the vapor is

and the volume occupied by the vapor phase is

The rest of the volume (2.5 L) is occupied by the liquid.

Vgmgvg 1 0.628 kg 21 0.12348 m^3 >kg 2 0.0775 m^3 1 or 77.5 L 2

mgxmt 1 0.157 21 4 kg 2 0.628 kg

64.2 kJ>kg

31.21 kJ>kg 1 0.157 21 209.90 kJ>kg 2

hhfxhfg

x

vvf

vfg



0.020.0007437

0.123480.0007437

0.157

TTsat @ 160 kPa
15.60°C

vg0.12348 m^3 >kg

vf0.0007437 m^3 >kg

v

V

m



0.080 m^3

4 kg

0.02 m^3 >kg

P, kPa

vf = 0.0007437

P = 160 kPa

T = 15.60C

m = 4 kg

160

vg = 0.12348

hf = 31.21 hg = 241.11 h, kJ/kg

R-134a

v, m^3 /kg

FIGURE 3–39

Schematic and P-vdiagram for

Example 3–5.

m^3 /kg

P = 0.5 MPa (151.83°C)

P = 0.1 MPa (99.61°C)

T,°C kJ/kg kJ/kg

u h

Sat.

100

150

1300

Sat.

200

250

...

1.6941

1.6959

1.9367

7.2605

0.37483

0.42503

0.47443

...

2505.6

2506.2

2582.9

4687.2

2560.7

2643.3

2723.8

...

2675.0

2675.8

2776.6

5413.3

2748.1

2855.8

2961.0

...

v

FIGURE 3–40

A partial listing of Table A–6.