Calculate the reduced temperature of the ammonia at the curr

Calculate the reduced temperature of the ammonia at the current state, T_R; Calculate the reduced pressure of the ammonia at the current state, p_R; Read Figure A-1 to find the compressibility factor at the current state, Z; Determine the specific volume using the compressibility factor, v_a, in m^3.kg; Determine the specific volume using the Ideal Gas Model, v_b, in m^3/kg; Compare v_a and v_b, and comment their difference.

Solution

a)

Reduced temperature Tr = T / Tc

= (100+273) / 406

= 0.9187

b)

Reduced pressure Pr = P / Pc

= 18 / 112.8

= 0.1596

c)

From Compressibility chart, for given Pr and Tr, we get Z = 0.87

d)

Pv = ZRT

v = 0.87*0.4882*10^3*(100+273) / 18*10^5

v = 0.088 m^3/kg

e)

Using ideal gas model, Pv = RT

v = RT/P

= 0.4882*10^3*(100+273) / 18*10^5

= 0.1011 m^3/kg

f)

Ratio of two voulmes = 0.088 / 0.1011 = 0.87

This ratio is same as Z. Using Z makes the results more realistic.