4.21 Initially, an insulated rigid tank contains 2.31 kg of water at 278.5 celsi

ID: 1860199 • Letter: 4

Question

4.21 Initially, an insulated rigid tank contains 2.31 kg of water at 278.5 celsius and 1 MPa.

A heater in the wall of the tank maintains the wall temperature at 600 celsius.

After a period of time, the pressure in the tamk rises to 1.5 MPa.

Determine the total entropy generation (kJ/K) during this process.

Mass*(s2-s1)

HOW DO YOU GET THESE

PLEASE SHOW WORK PLEASE work It out

Answer : 0.33412

PLEASE SHOW ALL WORK INTERPOLATION AND

HOW TO GET ALL NUMBERS NEEDED thankyou so much

Please use these tables and state which ones used thanks much

State 1

at T = 278.5 the saturated pressure is 6378KPa but given pressure is 1000KPa so the state is superheated

At 1000KPa from properties tables

T = 250 s =6.9246 and

T = 300 s = 7.1228

Now we need to find

at T = 278.5 what is s

By interpolating(equating the slopes)

(s-7.1228)/(7.1228-6.9246 ) = (278.5-300 )/(300 -250)

s = 7.1228 + (7.1228-6.9246 ) (278.5-300 )/50

s = 7.0376

At T =600 and P =1500 KPa the state is superheated

At T = 600 from properties tables

P =1400 Kpa s = 7.8710

P =1600 KPa s = 7.8080

P = 1500Kpa s = ?

s = 7.8395

Total entropy generation

S = m*(s2 -s1)

S = 2.31*(7.8395-7.0376) = 1.8524 KJ/K

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