Reg. No. :

B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2010

Fifth Semester

Chemical Engineering

CH 2303 — CHEMICAL ENGINEERING THERMODYNAMICS — I

(Regulation 2008)

Time : Three hours Maximum : 100 Marks

Answer ALL questions

PART A — (10 × 2 = 20 Marks)

1. Distinguish between steady state and equilibrium state of a process.

2. Distinguish between state function and path function with examples.

3. What has led to the inclusion of the concept of internal energy in the

formulation of first law of thermodynamics?

4. What are the major limitations of the first law of thermodynamics?

5. State Clausius inequality.

6. How is the entropy and probability interrelated?

7. How is Joule-Thomson coefficient evaluated from P-V-T information?

8. What is the criterion of equilibrium in terms of work function and internal

energy?

9. How does the clearance affect the work of adiabatic compression?

10. What are the limiting conditions to be satisfied by any equation of state in

general?

PART B — (5 × 16 = 80 Marks)

11. (a) (i) During the suction stroke in a diesel engine, atmospheric air at

300K and 0.1 MPa is drawn into the engine cylinder and then it is

compressed reversibly and adiabatically till the volume of the air

reduces to 1/15th of the original volume. At the end of the

compression stroke, the temperature of the air is such that when

fuel is injected, it ignites immediately. Calculate the temperature

and pressure of the air at the end of the compression stroke. Also,

calculate the work done per mole of air. Assume 4.1=γ for air. (8)

(ii) Derive the first law of thermodynamics for a steady state flow

process. (8)

Or

Question Paper Code : 53092

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(b) (i) A system is taken through a series of processes as a result of which

the system is finally restored to its initial state. The work and heat

interactions for some processes are measured and they are given

below :

Process W (kJ) Q (kJ) U∆ (kJ)

1–2 100 200 –

2–3 – –150 200

3–4 –250 – –

4–1 300 – 50

Calculate the Unknown quantities in the above table and determine

the network done and net heat interactions. (10)

(ii) Define the following terminologies of thermodynamics.

(1) Reversible and irreversible processes

(2) State function and state variables

(3) Thermodynamic equilibrium. (3 × 2 = 6)

12. (a) (i) Atmospheric air is a mixture of nitrogen and oxygen in the mole

ratio 79 : 21. Calculate the minimum work to be done to separate

1 kmol air at 0.1 MPa and 300K into pure nitrogen and oxygen at

the same temperature and pressure. Treat air as an ideal gas. (8)

(ii) Prove the equivalence of the Kelvin-Planck and Clausius

statements of the second law of thermodynamics (8)

Or

(b) (i) A domestic refrigerator transfers energy in the form of heat from

the cold space to the ambient atmosphere at higher temperature.

Does it violate the Clausius statement of the second law of

thermodynamics? Explain in detail. (8)

(ii) An inventor claims to have developed a cyclically working device

which absorbs 500 kJ as heat from a reservoir at 800K and 300 kJ

from a reservoir at 400K and rejects 100 kJ as heat to a reservoir at

600K and 50kJ to a reservoir at 300K while it delivers 650kJ work.

Would you agree with his claim? Justify your answer on

thermodynamic grounds. (8)

13. (a) The equation of state of a certain substance is given by the expression

3T

C

P

RTV −= and the specific heat is given by the relation BTACp +=

where A, B and C are constants. Drive expressions for change in internal

energy, enthalpy and entropy for (i) an isothermal process (ii) an isobaric

process. (16)

Or

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(b) Show that

(i)

s

p

P

P

T

T

V

TC

∂∂

∂∂

=

(ii) ( )

dPCC

VdTCdHvp

p

−−+=

β

κ

(iii) TV

UP

T

PT

v

∂∂

=−

∂∂

(iv)

∂∂

+

∂∂

−=

∂∂

TPT P

VP

T

VT

P

U. (16)

14. (a) Calculate the compressibility factor and molar volume for methanol

vapor at 500K and 10 bar by using the following equations. Experimental

values of virial coefficients are /molm1019.2 34−×−=B ; 81073.1 −×−=C

26/molm . The critical temperature and pressure of methanol are 5 12.6K

and 81 bar.

(i) Truncated form of virial equation

(ii) Redlich-Kwong equation. (16)

Or

(b) Explain the PVT behaviour of fluids in detail. (16)

15. (a) Air at 600K and 2000 kPa enters a convergent-divergent nozzle whose

throat area is one half that of the discharge of the divergent section.

Assuming 4.1=γ for air, determine the following.

(i) The pressure, temperature, velocity and density at the throat when

the Mach number is 0.8 at the throat

(ii) The critical pressure corresponding to the reservoir condition. (16)

Or

(b) Write a detailed note on the following

(i) Working of ejectors

(ii) Multi-stage compression. (2 × 8 = 16)

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