A boiler feed pump delivers 0.05m^3/s of water at 240 C, 20 Mpa. What is the mas

Question

A boiler feed pump delivers 0.05m^3/s of water at 240 C, 20 Mpa. What is the mass flow rate (kg/s). Also what would the percent error be if the properties of saturated liquid at 240 C were used in the calc (From tables in book--> h20 @ 240 C=
pressure=3344.2kPa Sat. L(Vf)= 0.001229 Sat gas(Vg)=0.05976) now what if the properties of water at 20MPa were used ( From book H20 @ 20kPa= T=60.06 C Sat. L=0.001017 Sat.g= 7.64937) ------ those values from the book are to determine the percent error if they were used in the flowrate calc. Please help, thanks:)))

Explanation / Answer

So mass flow rate equals Volume flow rate/specific volume. My notation: M=V/v

1st Part: 0.05 m3/s / 0.001205 m3/kg = 41.5 kg/s   

(T, P) compressed liquid seen in B.1.4: v=0.001205 m3/kg <---At least that is in my book.Sonntag, Borgnakke and van Wylen

2nd Part: Use the specfic volume of the saturated liquid at 240 C.

0.05 m3/s / 0.001229 m3/kg = 40.68 kg/s

then do (41.5-40.68)/41.5 X 100% = 2% error

3rd Part: Use the specific volume of the saturated liquid at 20 MPa. You gave the value for 20 kPa. So the information you gave for that part I didn't use. I think the value you actually are suppose to use is v(f)=0.002036 m3/kg

SO 0.05 m3/s / 0.002036 m3/kg = 24.56 kg/s

then do (41.5-24.56)/41.5 X 100% = 40.8% error (round up to 41% if you so choose)

The End.

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