Home Assignment Sheet (Iii & Iv Unit)

HOME ASSIGNMENT SHEET
1. 5 kg of steam is at a pressure of 10 bar and temperature 240 oC. The

steam has a steady flow without friction through an exposed pipe.
Now 4187 kJ of heat is extracted from it, the pressure remaining
constant. Determine the final condition of steam.
2. A pressure cooker contains 1.5 kg of saturated steam at 5 bar. Find the
quantity of heat which must be rejected so as to reduce the quality to
60% dryness. Determine the pressure and temperature of the steam at
the new state.
3. Steam initially at 1.5 MPa and 300oC expands reversibly and
adiabatically in a steam turbine to 40oC. Determine the work output of
the turbine per kg of steam.
4. A vessel contains one kg of steam which contains one-third liquid and
two-third vapor of volume. The pressure of the steam is 5 bar. Find the
dryness fraction, specific volume and specific enthalpy of the mixture.
5. One kg of steam at 8.5 bar and 0.95 dryness expands adiabatically to a
pressure of 1.5 bar. The law of expansion is pv1.2 = C. Determine (a)
the final dryness fraction of the steam and (b) the change in internal
energy.
6. A combined separating and throttling calorimeter is used to determine
the dryness fraction of steam. Pressure in the steam main is 8 bar and
the pressure and temperature after throttling are 1 bar and 120oC
respectively. The mass of water collected in the separator is 0.5 kg.
The mass of steam condensed after throttling is 4.0 kg. Determine the
dryness fraction of steam in the steam main.
7. In a combined separating and throttling calorimeter, the following
observations were made. Total quantity of steam passed through the
calorimeter = 23.4 kg, water drained from separator = 1.2 kg, steam
pressure before throttling = 8.25 bar, temperature of steam after
throttling = 111.4oC, steam pressure after throttling = 1 bar. Find the
dryness fraction of steam.
8. A reversible engine is supplied with heat from two constant
temperature reservoirs at 900 K and 600 K and rejects heat to a
constant temperature sink at 300 K. The engine develops 100 kW and
rejects 3600m kJ of heat per minute. Determine the heat supplied by
each source per minute and the engine efficiency.
9. A Carnot heat engine takes in heat from an infinite reservoir A and
rejects heat to another infinite reservoir B. Half of the work delivered
by this engine is used to drive a generator and another half drives a
reversed Carnot engine that receives heat from the reservoir B and
rejects heat to an infinite reservoir C. Express the heat rejected to C by
the reversed engine as a percentage of the heat supplied from A to the
Carnot engine and calculate the heat rejected per hour to C if 500 kW
of power is generated. Assume the efficiency of the generator to be
100%.
10. A Carnot engine draws heat from a reservoir at a temperature TA and
rejects heat to another reservoir at a temperature TB. The engine drives
a refrigerator which absorbs heat from a reservoir at a temperature T C
and rejects het to the reservoir at TB. For TA=500 K and TC = 250 K,
estimate TB such that the heat taken in by the engine from the
reservoir at TA, equals the heat absorbed by the refrigerator from the
reservoir at TC. Estimate also the efficiency of the engine and the COP
of the refrigerator.
11. Two Carnot engines A and B are connected in series between two
thermal reservoirs maintained at 1000 K and 100 K respectively. The
engine A receives 1680 kJ of heat from the high temperature reservoir
and rejects heat to the Carnot engine B. The engine B takes in the heat
rejected by the engine A and rejects heat to the low temperature
reservoir at 100 K. If the engines A and B have equal thermal
efficiencies, determine:
a. The heat rejected by the engine B
b. The temperature at which the heat is rejected by the engine
c. The work done by the engines A and B respectively
If the engine A and B deliver equal work, determine the amount of
heat taken in by the engine B and the efficiencies of the engines A and
B respectively.
12. An ice plant working on a reversed Carnot cycle heat pump produces
20 tons of ice per day. The ice is formed from water at 0 oC and is
maintained at 0oC. The heat is rejected to the atmosphere at 27oC. The
heat pump is coupled to a Carnot engine which absorbs heat from a
source maintained at 227oC by burning liquid fuel of calorific value
45000 kJ/kg and rejects heat to the atmosphere. Determine the
consumption of fuel per hour and the power developed by the engine.
Take the enthalpy of fusion of ice = 334.5 kJ/kg.

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HOME ASSIGNMENT SHEET

1. 5 kg of steam is at a pressure of 10 bar and temperature 240 oC. The

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