Part A

1. State Kelvin Planck’s and Clausius statement of second law of thermodynamics.

2. Differentiate heat Engine and heat pump with a diagrammatic representation

3. State Carnot’s principles. Give its mathematical statement.

4. Draw the PV diagram of the Carnot’s Cycle.

5. What are the steps involved in Carnot’s cycle?

6. Define Entropy and give its expression. State what type of function is that?

7. Give the mathematical statement of Second Law.

8. List the causes of irreversibility.

Friction, presence of driving force, time factor.

9. State Third law of thermodynamics.

10. A Carnot’s engine receives 500 kJ of heat per cycle from a high temperature source

at 652 oC and rejects heat to a low temperature sink at 30 oC. Determine heat rejected to sink per

cycle.

= 652 oC + 273 = 925 K, = 30 oC + 273 = 303 K,

= 500 kCal

and

To substitute,

By given temperatures, η = 0.6724 and = 163.78 kCal

11. A heat engine operates between a heat source at 700 K and a heat sink at 300 K. What is the

maximum efficiency of engine?

To substitute the temperatures, η = 0.5714.

Part B

1. Explain any Heat engine and obtain the Efficiency of the Engine.

2. State and Prove the Carnot’s principles.

3. Derive the Carnot’s Equation for an Ideal Gas.

4. Develop an expression to calculate the entropy change (occurring in a Reversible process /

irreversible involving an) of an ideal gas.

5. Explain the mathematical statement of second law.

6. (a) A central power plant, rated at 8x105 kw, generates steam at 585 K and discards heat to river at

295 K. If the thermal efficiency of the plant is 70% of the maximum possible value, how much heat

is discarded to the river at rated power?

(b) A steel casting weighing 40 kg and at a temperature of 450 oC is quenched in 150 kg of oil at

25 oC. If there are no heat losses, what is the change in entropy of (i) the steel casting (ii) the oil (iii)

both considered together? Data: Cp of steel casting = 0.5 kJ/kg.K and Cp of oil=2.5 kJ/kg.K

7. (a) A Heat Engine receives 500 kcal of heat per cycle from a reservoir at 1300 C and rejects heat to

a sink at 200 C in hypothetical amounts of (a) 300 kcal (b) 150 kcal (c) 100 kcal .Which of these

respective cases represents a reversible cycle, an irreversible cycle and

an impossible cycle?

Solution:

Formula:

and

TH = 1300 C + 273 = 1573 K and TC = 200 C + 273 = 473 K

Then to substitute the temperature,

ηmax = 0.6993 = 0.7

For the given hypothetical amounts of heat rejects to sink,

= 500 kcal

a) = = 0.4 (ηa< ηmax, so irreversible cycle)

b) = = 0.7 (ηa = ηmax, so reversible cycle)

c) = = 0.8 (ηa> ηmax, so iimpossible cycle)