Thermodynamic lecture slide chapter 7_Entropy

Thermodynamic lecture slide chapter 7_Entropy

1. DeliveredBy:
Engr.Saba Sadiq
[email protected]
CompletedinWeek 1
st
and2
nd

19. ProblemSheet
An insulated piston–cylinder device contains 5 L of saturated liquid
water at a constant pressure of 150 kPa. An electric resistance
heater inside the cylinder is now turned on, and 2200 kJ of energy
is transferred to the steam. Determine the entropychange ofthe
water duringthis process.

20. ProblemSheet
A 0.5-m3 rigid tank contains refrigerant-134a initially at 200 kPa
and 40 percent quality. Heat is transferred now to the refrigerant
fromasourceat35°Cuntilthepressurerisesto 400kPa.
Determine(a)theentropychangeoftherefrigerant,
(b) the entropy change of the heat source, and (c) the total
entropychange for thisprocess.

21. ProblemSheet
Apiston–cylinderdevicecontains5kgofsteamat100°Cwithaqualityof50percent.
Thissteam undergoes two processesas follows
1-2 Heat is transferred to the steam in a reversible manner while the temperature is held
constant until the steamexists
asasaturatedvapor.
•2-3Thesteamexpandsinan adiabatic,reversibleprocessuntilthepressure is15kPa.
(a)Sketchtheseprocesseswithrespect tothesaturationlines onasingleT-sdiagram.
(b)Determinetheheataddedtothesteaminprocess1-2,inkJ.
(c)Determinetheworkdonebythesteaminprocess2-3,inkJ.

22. ProblemSheet
4. An adiabatic pump is to be used to compress saturated liquid water at 10 kPa to a
pressure to 15 MPa in a reversible manner. Determine the work input using (a) entropy
data from the compressed liquid table, (b) inlet specific volume and pressure values, (c)
averagespecificvolumeandpressurevalues.Also,determinetheerrorsinvolvedin
parts(b)and(c).

23. ProblemSheet
A 20-kg aluminum block initially at 200°C is brought into contact with a 20-kg block
of iron at 100°C in an insulated enclosure. Determine the final equilibrium
temperatureandthe total entropychange for this process.
.5An insulated piston–cylinder device initially contains 300 L of air at 120 kPa
and 17°C. Air is now heated for 15 min by a 200-W resistance heater placed
insidethecylinder.Thepressureofairismaintainedconstantduringthis
process. Determine the entropy change of air, assuming (a) constant specific
heats(1.02kJ/kg.K)and(b)variable specificheats.

24. ProblemSheet
Airiscompressedfromaninitialstateof100kPaand17°Ctoafinalstateof
600kPaand57°C.Determinetheentropychangeofairduringthis
compressionprocessbyusing(a)propertyvaluesfromtheairtableand(b)
averagespecificheats.
Practice Sheet
All Examples and relevant problems from exercise
31,32,37,38,50,58,67,68,160,161