Write the general expression for First Law of Thermodynamics. Hence prove that total energy of the system is a property.

A frictionsless piston-cylinder device contains 0·4m^3 of air at 100kPaand 80°C. The air is now compressed to 0·1 m^3 in such a way that the temperature inside the cylinder remains constant. Determine the work done during the process.

Explain the Kelvin-Planck and Clausius statements of Second law of Thermodynamics.

Heat is transferred to a heat engine from a furnace at a rate of 80 MW. If the rate of waste heat rejection to a nearby river is 50 MW, determine the net power output and the thermal efficiency for this heat engine.

What are the causes of irreversibilities With the help of suitable examples, explain the internally and externally reversible processes.

A reversible heat engine is operating between -13°C and 37°C. Find its COP as

heat pump

refrigerator.

A refrigerator with a COP of 4·0 transfers heat at a rate of 0·5 kJ/s at the condenser. Find the rate of heat transfer at the evaporator and the power input to the compressor. Also calculate the COP, if the refrigerator were to operate as a heat pump with same heat and work interactions.

Prove that

(COP)hp COP)ref'

5. What do you understand by reversible and irreversible processes With the help of suitable examples, discuss the various factors responsible for irreversibility in a process.

Show that the entropy change in a process when a perfect gas changes from State 1 to State 2 is given by

s2- s1=Cv ln T2/T1+R ln V2/V1

A heat source at 800 K loses 2000 kJ of heat to a sink at

500 K and

750 K. Determine which heat transfer process is more irreversible.

7. A steam power plant has steam at a pressure of 40 bar and temperature 400°C and exhausted into a condenser where a pressure of 0·05 bar is maintained. The mass flow rate of steam is 160 kg/so Determine:

Rankine cycle efficiency

Rankine engine efficiency

Power developed

Specific steam consumption

Heat rejection in the condenser

Derive an expression for minimum work in two-stage compression with intercooling.

A gas is to be compressed from 30 kPa to 500 kPa. It is known that cooling corresponding to a polytropic exponent of 1·25 is practical and the clearance of the available compressor is 3%. Compare the volumetric efficiencies to be anticipated for

single-stage compressor

two-stage compression with equal pressure ratios in the stages.

Show on T-s and P-h diagrams the effect of irreversibilities on compressor work. Express adiabatic efficiency of the compressor in terms of enthalpies.

Explain the working of a Reverse Brayton cycle. Derive the expression of COP for Reverse Brayton cycle.

10. Write short notes on the following:

WHF

Principles of Energy Conservation