Question Bank Thermal Engineering1. Definethefirstlawofthermodynamics.Alsogivesupportingmathematicalexpressionforit.2.Howthefirstlawofthermodynamicsisappliedtoaclosedsystemundergoinganon-cyclicprocess?3.Showthatinternalenergyisaproperty.4.Explainthefollowing:(a)Freeexpansion(b)Polytropicprocess(c)Hyperbolicprocess.

Q3 kg of air at 1.5 bar pressure and 77C temperature at state 1 is compressed polytropically to state 2 at pressure 7.5 bar, index of compression being 1.2. It is then cooled at constant temperature to its original state 1. Find the net work done and heat transferred.

1. Using IInd law of thermodynamics show that the following are irreversible(i) Free expansion.(ii) Heat transfer through finite temperature difference.2. Determine the heat to be supplied to a Carnot engine operating between 400C and 15C and producing 200 kJ of work.

3. A refrigerator operates on reversed Carnot cycle. Determine the power required to drive refrigerator between temperatures of 42C and 4C if heat at the rate of 2 kJ/s is extracted from the low temperature region.

4. A reversible heat engine operates between two reservoirs at 827C and 27C. Engine drives a Carnot refrigerator maintaining 13C and rejecting heat to reservoir at 27C. Heat input to the engine is 2000 kJ and the net work available is 300 kJ. How much heat is transferred to refrigerant and total heat rejected to reservoir at 27C?

5. In a winter season when outside temperature is 1C, the inside of house is to be maintained at 25C. Estimate the minimum power required to run the heat pump of maintaining the temperature. Assume heating load as 125 MJ/h.

6. A cold storage plant of 40 tonnes of refrigeration capacity runs with its performance just 1/4th of its Carnot COP. Inside temperature is 15C and atmospheric temperature is 35C. Determine the power required to run the plant. [Take : One ton of refrigeration as 3.52 kW]

7. A domestic refrigerator maintains temperature of 8C when the atmospheric air temperature is 27C. Assuming the leakage of 7.5 kJ/min from outside to refrigerator determine power required to run this refrigerator. Consider refrigerator as Carnot refrigerator.

8. A cold body is to be maintained at low temperature T2 when the temperature of surrounding is T3. A source is available at high temperature T1. Obtain the expression for minimum theoretical ratio of heat supplied from source to heat absorbed from cold body.

9. Calculate the change in entropy of air, if it is throttled from 5 bar, 27C to 2 bar adiabatically.

10.