Answer All
questions
PART A – (10×2=20
marks)
1.
State
the first law for a closed system undergoing a process and a cycle?
2.
Why
does free expansion have zero work transfer?
3.
What
is thermal energy reservoir? Explain the term source and sink?
4.
What
is reserved heat engine?
5.
What
is meant by dryness fraction of steam?
6.
Draw
the standard Rankine cycle on p –v and T- s coordinates?
7.
What
is Joule – Thomson co efficient? Why it is zero for an ideal gas?
8.
What
is the law of corresponding states?
9.
What is Amagat’s Law?
10. What is sensible
heating?
PART- B –
(5×16=20 marks)
11. a) A gas under goes a thermodynamic cycle consisting of the following process:
i)
Process 1-2: Constant pressure p1 = 1.4
bar, V1 = 0.028 m3, W12 = 10.5 kJ.
ii)
Process 2-3: Compression with pV = constant, U3
= U2.
iii)
Process 3-1: Constant Volume, U1 – U3
= 26.4kJ.
There are no significant changes in K.E and P.E
1) Sketch the cycle on a pV diagram.
2) Calculate the network for the cycle in KJ.
3) Calculate the heat transfer for process 1-2.
4) Show that £Qcycle = £Wcycle
OR
b) A turbine operating under steady flow condition receives steam at the
flow state pressure 13.8 bar specific volume 0.143m3KJ internal
energy 250kJ/Kg velocity 30 m/s the state of the steam leaving the turbine is
pressure 0.35 bar specific volume 4.37 m3KJ internal energy
2360kJ/Kg Velocity 90 m/s heat is last to the surrounding at the rate 0.25kJ/s.
if the rate of steam flow is 0.38kJ/s. what is the power developed by the
turbine?
12. a) A reversible heat engine operates between two
reservoirs at temperature of 6000C and 400C. The engine
drives a reversible refrigerator which
operates between reservoirs at the temperature of 400C and - 200C. The
heat transfer to the heat engine is 2000kJ and the network output for the
combined engine refrigerator is 360kJ. Calculate the heat transfer to the
refrigerator and the net heat transfer to the reservoir at 400C.
OR
b) Two kg of air at
500kPa, 800C expands adiabatically in a closed system until its
volume is doubled and its temperature becomes equal to that of the surroundings
which is at 100 kPa, 50C. For this process determine
i) The maximum work
ii) The change in
availability and the irreversibility
13 a) A vessel of volume 0.04m3
contains a mixture of saturated water and saturated steam at a temperature of
2500C. The mass of the liquid present is 9kg. Find the pressure, the mass,
the specific volume, the enthalpy and entropy and the internal energy of the
mixture.
OR
b) A steam power plant operates in a simple ideal
Rankine cycle between the pressure limits of 3Mpa and 50Mpa. The temperature of
the steam at the turbine inlet is 3000C and the mass rate of steam
through the cycle is 35kg/s. Show the cycle on a Ts diagram with respect to
saturation lines and determine
i) The thermal efficiency of the cycle and
ii) The net power output of the power plant
14. a) Derive
any three of the Maxwell relations?
OR
b) Determine
the pressure of nitrogen gas at T = 175 K and v = 0.00375m3/kg on
the basis of
i) The ideal gas equation of state
ii) The van der Waals equation of state.
The van der Waals constants for nitrogen are a=
0.175m6.kPa/kg2 , b = 0.00138m3/kg
15. a) An
engine ideal air standard diesel cycle has the compression ratio 15 and heat
transfer 1400kJ/kg. Find the pressure and temperature at the end of the each
process if the inlet conditions are 280K and 1.1 bar. Find also the air
standard efficiency and mean effective pressure.
OR
b) Atmospheric air at 1.0132 bar has a DBT of 300C
and WBT of 250C.
compute
i)
The partial pressure of water vapour
ii)
Specific humidity
iii)
The dew point temperature
iv)
The relative humidity
v)
The degree of saturation
vi)
The density of air in the mixture
vii)
The density of vapour in the mixture and
viii)
The enthalpy of the mixture. Use the thermodynamic
tables only.
0 Comments