Question

For a specific volume of 0.2 m3/kg, find the quality of steam if the absolute pressure is (a) 40 kPa and ( b ) 630 kPa. What is the temperature of each case?

Answer 1

Explanation:For a specific volume of 0.2 m3/kg, find the quality of steam if the absolute pressure is (a) 40 kPa  

and ( b ) 630 kPa. What is the temperature of each case?  

Find: x – ? T – ?  

Given: v=0.2 m3/kg  

p1=40 kPa  

p2=630 kPa  

Solution:  

(a) Using information from Table (Properties of Saturated H2O-Pressure Table), we calculate the  

quality as follows: v = vf +x(vg −vf) (1), Of (1)  0.2 = 0.001+x(3.993−0.001) (2)  

Of (2)  x=0.04985  

The temperature is found in Table next to the pressure entry: T = 75.9°C.  

(b) We must interpolate to find the correct values in Table. Using the values at 0.6 and 0.8 MPa we  

have: vg = (0.03 0.2 )×(0.2404−0.3157) +0.3157 = 0.3044 (3)  

vf=0.0011 (4) (3) and (4) in (1): 0.2 = 0.0011+x(0.3044−0.0011) (5)  

Of (5)  x=0.6558  

The temperature is interpolated to be: T = (0.03 0.2 )×(170.4−158.9)+158.9 = 160.6°C  Answer:  

(a) x=0.04985, T = 75.9°C;  

(b) x=0.6558; T = 160.6°C