Question

Determine the missing property among P, T, *, x for the following states:

a. Ammonia 25°C, v = 0.10 m3/kg

b. Ammonia 1000 kPa, * = 5.2 kJ/kg K

c. R-134a 5°C, * = 1.7 kJ/kg K

d. R-134a 50°C, * = 1.9 kJ/kg K

e. R-22 100 kPa, v = 0.3 m3/kg

Answer 1

(a) x = (0.1 – 0.001658)/0.12647 = 0.7776

• = sf + x sfg = 1.121 + x × 3.9083

= 4.1601 kJ/kg K

(b) T = 40 + 10 × (5.2 – 5.1778)/(5.2654 – 5.1778)

= 42.53°C

superheated vapor so x is undefined

(c) x = (1.7 – 1.0243)/0.6995 = 0.96598

P = Psat = 350.9 kPa

(d) superheated vapor between 200 and 300 kPa

P = 200 + 100 × (1.9 – 1.9117)/(1.8755 – 1.9117)

= 232.3 kPa

(e) T = 40 + 10 × (0.3 – 0.29739)/(0.30729 – 0.29739) = 42.636°C

• = 1.1919 + 0.2636 × (1.2132 – 1.1919)

=1.1975 kJ/kg K