Page 434 - Advanced thermodynamics for engineers

424 CHAPTER 18 LIQUEFACTION OF GASES

Table 18.1 Critical temperatures and pressures for common substances
Critical Temperature, Critical Pressure,

Substance T c C [K] p c (bar)
Water (H 2 O) 374 [647] 221.2
Methane (CH 4 ) 82 [191] 46.4
Ethane (C 2 H 6 ) 32 [305] 49.4
Propane (C 3 H 8 ) 96 [369] 43.6
Butane (C 4 H 10 ) 153 [426] 36.5
Carbon dioxide (CO 2 ) 31 [304] 89
Oxygen (O 2 ) 130 [143] 51
Hydrogen (H 2 ) 243 [30] 13
Nitrogen (N 2 ) 147 [126] 34

Temperature, T p c = 51 bar p = 1bar

Ambient
T a
conditions

o
Tc = -130 C

Entropy, S
FIGURE 18.1
State point of oxygen at ambient temperature and pressure.

(a) (b) 3
Q

Condenser Temperature, T
4 3 Compressor 4 Condensation Compressor
work
Work
Throttle
Throttling
2
Evaporator 1 ' 2
1 Evaporation
1 Q
Entropy, S
FIGURE 18.2
A simple refrigerator (a) schematic of plant; (b) temperature–entropy (T–S) diagram.