7/25/2019 E2SEM1MT2TD06102012

1/3

E2 SEM1 ME TD MT2 QP

1) A paddle wheel provides 200 kJ of work to the air contained in a 0.2-m3rigid volume,initially at 400 kPa and 40C. Determine the entropy change if the volume is insulated.

A)

0.504 kJ/KB) 0.443 kJ/K

C) 0.312 kJ/KD) 0.231 kJ/K

2) Five kilograms of ice at 20C are mixed with 10 kg of water initially at 20C. If there is nosignificant heat transfer from the container, determine the net entropy change. It takes 330 kJ to

melt a kg of ice.(A) 0.064 kJ/K

(B) 0.084 kJ/K(C) 1.04 kJ/K

(D) 1.24 kJ/K

3) The p,v,T relation of a real gas is represented with reasonable accuracy by the relation

V=RT/p + B- A/RT

Where A and B are constants. for this gas find the change in enthalphy and entropy along the

isothermal path between pressures p1 and p2

A) (b-2A/RT)(P2 P1) and( R ln (P2/ P1) - A( P2 P1)/RT2)

B) (b-2A/RT)(P2 P1) and( R ln (P2/ P1) + A( P2 P1)/RT2)

C)

(b-2A/RT)(P1 P2) and( R ln (P2/ P1) - A( P2 P1)/RT2)D) (b-2A/RT)(P2 P1) and( R ln (P1/ P2) - A( P2 P1)/RT)

E)NONE

4) A refrigerator storage is supplied with 3600 kg of fish at a temperature of 27C. The fish has

to be cooled to 23C for preserving it for a long period without deterioration. The coolingtakes place in 10 hours. The specific heat of fish is 2.0 kJ/kg K above freezing point of fish and

0.5 kJ/kg-K below freezing point of fish, which is -3C. The latent heat of freezing is 230 kJ/kg.What is the power to drive the plant if the actual COP is half that of

the ideal COP?A) 30 kW

B) 15 kWC) 12 kW

D) 6 kW

5) In the T-S diagram shown in the figure, which one of the following is representedby the area under the curve?

7/25/2019 E2SEM1MT2TD06102012

2/3

E2 SEM1 ME TD MT2 QP

A) . Total work done during the process

B) Total heat absorbed during the processC). Total heat rejected during the process

D). Degree of irreversibility

6) A 100 resistor carrying a constant current of 0.5 A is kept at a constant temperature of 300K by a stream of cooling water. In a time interval of 30 minutes, what are the changes in entropy

for the resistor and that of the universe, respectively?A) 0 and 150 J/KB) 150 J/K and 0

C) 300 J/K and 0D)0 and 300 J/K

7) According to the Maxwell relation, which of the following is/are correct?

A) (v/T)P=- (s/P)T

B) (s/v)T = -(p/T)V

c) (p/T)V = (s/v)T

D) all the above

8) Calculate the entropy change of a 10-kg block of copper if the pressure changes from 100 kPato 50 MPa while the temperature remains constant. Use = 5 X 10

-5K

-1and = 8770 kg/m

3

A) -0.285 J/kg KB)

-0.385 J/kg K

C) -0.485 J/kg KD) -0.585 J/kg K

9) Find an expression for Cp- Cv. if P = RT/v - a / v2

A) TR2P/(Pv

2- a )

B) TR2v/(Pv

2- a )

C) TRv/(Pv2- a )

D) TR2v/(Pv

-2- a )

E)none

10) What is (s/P)Tfor an ideal gas?

A) - 1 / PB) - R / P

C) - 1 / TD) -R/ T

7/25/2019 E2SEM1MT2TD06102012

3/3

E2 SEM1 ME TD MT2 QP

Descriptive

Answer any one from the following question1) Air at 101.35Kpa, 27

0C is cooled to a lower temperature, by exchanging heat nitrogen at

103.42kpa,166K,in a steady state heat exchanger as shown in the below fig. asuming air

and nitrogen to behave ideally with constant specific heats of CP=1.006KJ/kg K and 1.08KJ/kg K respectively, calculate the mass flow rate of nitrogen, and the temperature of the

air at the exit.

2) In a process industry hot gases are delivered by different units.one unit delivers a gas at 1

bar and 1000K at a rate of 1kmol/s while a second unit delivers a gas at 1bar and 800 K ata rate of 2 kmol/s.These hot gases are usually cooled to 300K in heat exchangers.The

ambient atmosphere is at 300K An engineer plans to use the hot gases as source andambient atmosphere as sink to operate a heat engine and thus obtain some power.

Calculate the maximum power that can be obtained ifa) Gases A and B are used as separate sources, and

b) Gases A and B are mixed and the mixture is used as a source

Assume both the gases A and B are ideal with =1.4

KEY1) A

2) ADD 1 MARK TO ALL3) A

4) C5) B

6) A7) A OR C

8) A9)

B

10)B