Download ET 11-08-14 SET 2

LOYOLA – ICAM
COLLEGE OF ENGINEERING AND TECHNOLOGY (LICET)
Loyola College Campus, Nungambakkam , Chennai – 34
Branch: MECHANICAL
Date: 11.08.2014
Semester: V
Time: 8.00 – 10.00 am (2 Hrs)
CAT – 1
ENGINEERING THERMODYNAMICS (ME 6301)
Part-A (Answer all the questions)
1.
2.
3.
4.
5.
6.
(6x2=12)
Define Intensive and Extensive properties.
State Zeroth law of thermodynamics.
What is meant by thermodynamic work?
State Kelvin-Plank statement of second law of thermodynamics
What are the processes involved in Carnot cycle?
What is available and unavailable energy?
Part-B (Answer all the questions)
(3x16=48)
3
3
7. One kg of gas expands at constant pressure from 0.085 m to 0.13 m . If the fluid temperature of the
gas is 225°C, find the final temperature, net heat transfer, change in internal energy and the pressure
of gas. Assume Cp = 1.005 kJ/kgK and Cv = 0.71 kJ/kgK
Or
8. a) Apply steady flow energy equation to Nozzle and derive the formula for exit velocity.
(6)
b) At the inlet to certain nozzle, the enthalpy of the fluid passing is 3000 kJ/kg and the velocity is
60 m/s. At the discharge end, the enthalpy is 2762 kJ/kg. The nozzle is horizontal and there is
negligible heat loss from it. Find (i) Find the velocity at the exit of the nozzle. (ii) If the inlet area is
0.6 m2 and the specific volume at inlet is 0.187 m3/kg find the mass flow rate (iii) If the specific
volume at the nozzle exit is 0.498 m3/kg, find the exit area of the nozzle.
(10)
9. Two carnot engines A & B are operated in series. The first one receives heat at 870 K and rejects to
a reservoir at T. B receives heat rejected by the first engine and in turn rejects to a sink at 300 K.
Find the temperature T for (i) Equal work outputs of both engine (ii) Same efficiencies.
Or
10. 1 kg of air is compressed polytropically from 1 bar pressure and temperature of 300 K to a pressure
of 6.8 bar and temperature of 370 K. Determine the irreversibility if the sink temperature is 293 K.
Assume R = 0.287 kJ/kgK, Cp = 1.004 kJ/kgK and Cv = 0.716 kJ/kgK
11. a) Apply steady flow energy equation to turbine and derive the formula for work.
(6)
b) In the turbine installation, the gas enters the turbine at the rate of 5 kg/sec with the velocity of 50
m/sec and the enthalpy of 900kJ/kg and leaves the turbine with 150 m/sec and the enthalpy of
400kJ/kg. The loss of heat from the gases to the surrounding is 25kJ/kg. Assume R = 0.285 kJ/kgK
and the inlet conditions to be at 100 kPa and 27°C. Determine the work done and diameter of inlet
pipe.
(10)
Or
12. Prove that increase in entropy in a polytropic process is (i) ∆𝑆 = 𝑚𝐶𝑣
(ii) ∆𝑆 = 𝑚𝐶𝑣
𝑛−𝛾
𝑛−1
𝑇2
ln⁡( )
𝑇1
𝛾−𝑛
𝑛
𝑃
ln⁡( 1)
𝑃2
LOYOLA – ICAM
COLLEGE OF ENGINEERING AND TECHNOLOGY (LICET)
Loyola College Campus, Nungambakkam , Chennai – 34
Branch: MECHANICAL
Date: 11.08.2014
Semester: III
Time: 8.00 – 10.00 am (2 Hrs)
CAT – 1
ENGINEERING THERMODYNAMICS (ME 6301)
Part-A (Answer all the questions)
1.
2.
3.
4.
5.
6.
(6x2=12)
Define open, closed and isolated system.
State first law of thermodynamics.
Define thermodynamic equilibrium.
State Clausius statement of second law of thermodynamics.
List the limitations of first law of thermodynamics.
Write the expression for COP of heat pump and refrigerator.
Part-B (Answer all the questions)
(3x16=48)
7. A system contains 0.2 m3 of a gas at a pressure of 4 bar and 150°C. It is expanded adiabatically till
the pressure falls to 1 bar. The gas is then heated at a constant pressure till its enthalpy increases by
100 kJ. Determine the total work done. Take Cp =1 kJ/kgK and Cv = 0.714 kJ/kgK.
Or
8. 12 kg of air per minute is delivered by a centrifugal air compressor. The inlet and outlet conditions
of air are C1 = 12 m/s, P1 = 1 bar, v1 = 0.5 m3/kg and C2 = 90 m/s, P2 = 8 bar, v2 = 0.14 m3/kg. The
increase in enthalpy of air passing through the compressor is 150kJ/kg and heat loss to the
surroundings is 700kJ/min. Find (i) Motor power required to drive the compressor (ii) Ratio of inlet
to outlet pipe diameter.
9. In a Carnot cycle the maximum pressure and temperature are limited to 18 bar and 410°C. The
volume ratio of isentropic compression is 6 and isothermal expansion is 1.5. Assume the volume of
the air at the beginning of isothermal expansion as 0.18m3. Show the cycle on pV and Ts diagram
and determine (i) the pressure and temperature at main points (ii) Thermal efficiency of the cycle.
Or
10. A single stage air turbine is to operate with air inlet pressure and temperature of 1 bar and 600 K.
During the expansion the turbine losses are 20 kJ/kg to the surroundings which is at 1 bar and 300
K. For 1 kg of mass flow rate determine (i) decrease in availability (ii) Maximum work (iii) the
irreversibility.
11. 0.1 m3 of an ideal gas at 300 K and 1 bar is compressed adiabatically to 8bar. It is then cooled at
constant volume and further expanded isothermally so as to reach the condition from where it
started. Calculate (i) Pressure at the end of constant volume cooling (ii) Change in internal energy
during constant volume process (iii) Network done and heat transferred during the cycle. Assume
Cp = 14.3 kJ/kgK and Cv = 10.2 kJ/kgK
Or
12. Prove that increase in entropy in a polytropic process is (i) ∆𝑆 = 𝑚𝐶𝑣
(ii) ∆𝑆 = 𝑚𝐶𝑣
𝑛−𝛾
𝑛−1
𝑇2
ln⁡( )
𝑇1
𝛾−𝑛
𝑛
𝑃
ln⁡( 1)
𝑃2