EXERCISE SHEET
MODULE- 4
PROPERTIES OF PURE SUBTANCES AND VAPOUR POWER CYCLES
PROPERTIES OF PURE SUBSTANCES
Q1 (dec_2011). 2 kg of steam is at 10 bar and 0.8 dry. Determine its enthalpy, entropy and volume.
Q2.(dec_2010) Steam is supplied to a turbine at a pressure of 32 bar and a temperature of 395 0 C. It
expands isentrpocally to a pressure of 0.08 bar. What is the dryness fraction at the end of expansion?
Q3. (May_2009) One kg of steam at a pressure of 17 bar and dryness 0.95 is heated at a constant pressure,
until it is completely dry. Determine (i) Increase in volume (ii) Quantity of heat added.
Q4. Calculate the internal energy per kg of superheated steam at a pressure of 10 bar absolute and a
temperature of 573 K. also find the change of internal energy if this steam is expanded to 1.4 bar absolute
and dryness fraction 0.8.
Q5. A vacuum pump is used to evacuate a chamber where some specimens are dried at 500C. the pump
rate of volume displacement is 0.5 m3/s with an inlet pressure of 0.1 kPa and temperature 323K. How
much water vapor has been removed over 30 minutes period?
VAPOR POWER CYCLES
Q6.( Dec_2011) Steam at 20 bar, 3500 C is expanded in a steam turbine to 0.1 bar. It then enters a
condenser where it is condensed to saturated liquid water. The pump feeds back the water into the boiler.
Determine the Rankine efficiency and specific steam consumption of the power plant. Also find the
Rankine efficiency when turbine and pump have efficiencies 0.8 and 0.75 respectively.
Q7.(dec_2011) (a) Sketch the Rankine cycle on P-V and T-S diagrams. (b) Draw schematic
representation of thermal power plant with one reheater. Also represent this on T-S diagram.
Q8. (dec_2009) A steam turbine working on Rankine cycle is supplied with dry saturated steam at 25 bar
and the exhaust takes place at 0.2 bar. For a steam flow rate 10 kg/s, determine (i) Quality steam at end of
expansion (ii) turbine shaft work (iii) power required to drive the pump (iv) work ratio (v) Rankine
efficiency.
Q9.(May_2010) A rankine cycle operated between the pressure 15 bar and 0.01 bar. The initial degree of
superheat is 1000 C. Assuming isentropic efficiency of expansion 85%, calculate: (i) pump work (ii)
actual turbine work (iii) thermal efficiency.
EXERCISE SHEET
MODULE- 5
GAS POWER CYCLES
Q1. In an air standard Diesel Cycle, the compression ratio is 15 and the fluid properties at the
beginning of compression are 100 kPa and 300 K. For a peak temperature of 1600 K, calculate
(a) the percentage of stroke at which cut-off occurs (b) the cycle efficiency and (c) the work out
per kg of air.
Q2. A diesel engine has 20 cm bore and 30 cm stroke. The clearance volume is 420 cm 3. The
fuel is injected at constant pressure for 5% of the stroke. Calculate the air standard efficiency. If
the cut-off ratio is delayed from 5% to 8% what will be the percentage loss in efficiency. In both
cases, the compression ratio is the same.
Q3. Show that for the maximum work to be done per kg of air in Otto cycle between given upper
and lower limits of absolute temperature T3 and T1 respectively, the ratio of compression should
have the value r= (T3/T1)1.25 , when Ɣ=1.4.
Q4. An air standard dual cycle has a compression ratio of 16 and compression begins at 1bar and
500 C. the maximum pressure is 70 bar. The heat transferred to air at constant pressure is equal to
that a constant volume. Estimate (i) Cycle efficiency (ii) mean effective pressure of cycle.
Q5. The pressure ratio of an open cycle gas turbine power plant is 5.6. Air is taken at 300 C and 1
bar. The compression is carried out in two stages with perfect inter cooling in between. The
maximum temperature of the cycle is limited to 7000 C. Assuming that the isentropic efficiency
of each compressor stage as 85% and that of turbine as 90%, determine the power developed and
efficiency of the power plant, if the air flow is 1.2 Kg/s. The mass of fuel may be neglected and
it may be assumed as Cp= 1.02 kJ/kgK and Ɣ=1.4.
Q6. The gas turbine has an overall pressure ratio of 5:1 and a maximum cycle temperature of
5500 C. The turbine drives the compressor and an electric generator, the mechanical efficiency of
the drive being 97%. The ambient temperature is 200 C and the isentropic efficiencies for the
compressor and turbine are 0.8 and 0.83 respectively. Calculate the power output in kilowatts for
an air flow of 15 kg/s. calculate also the thermal efficiency and the work ratio. Neglect changes
in K.E, and the loss of pressure in combustion chamber.
Home Assignments: solve Q No. 4, 5, 7, 8 from Module 4 and Q No 1, 4, 5 from Module 5.