Superheated R-at 0.5 MPa, 20°C is cooled in a piston-cylinder at constant temperature to a final two-phase state with quality of 50%. The refrigerant mass is 5 kg, and during the processkJ of heat is removed. Find the necessary work.
a) -67.9 kJ
b) -77.9 kJ
c) -87.9 kJ
d) -97.9 kJ
Q.2.
Air atK flows with 3 kg/s into a heat exchanger and out at 100°C. How much (kg/s) water coming in atkPa, 20°C can the air heat to the boiling point?
a) 0.37 kg/s
b) 0.17 kg/s
c) 0.27 kg/s
d) 0.57 kg/s
Q.3.
Nitrogen gas flows into a convergent nozzle atkPa,K and very low velocity. It flows out of the nozzle atkPa,K. If the nozzle is insulated find the exit velocity.
a) 681.94 m/s
b) 581.94 m/s
c) 481.94 m/s
d) none of the mentioned
Q.4.
A steam turbine has an inlet of 2 kg/s water atkPa, 350°C and velocity ofm/s. The exit is atkPa, x = 1 and very low velocity. Find the specific work.
a) 382.3 kJ/kg
b) 482.3 kJ/kg
c) 582.3 kJ/kg
d) 682.3 kJ/kg
Q.5.
A steam turbine has an inlet of 2 kg/s water atkPa, 350°C and velocity ofm/s. The exit is atkPa, x = 1 and very low velocity. Find the power produced.
a) 664.6 kW
b) 764.6 kW
c) 864.6 kW
d) 964.6 kW
Q.6.
10kg of water in a piston-cylinder exists as saturated liquid/vapour atkPa, with a quality of 50%. It is now heated till the volume triples. The mass of piston is such that a cylinder pressure ofkPa will float it. Find the heat transfer in the process.
a) 23961 kJ
b) 24961 kJ
c) 25961 kJ
d) 26961 kJ
Q.7.
A vertical cylinder fitted with a piston contains 5 kg of R-at 10°C. Heat is transferred causing the piston to rise until the volume has doubled. Additional heat is transferred until the temperature inside reaches 50°C, at which point the pressure inside the cylinder is 1.3 MPa. Find the work done.
a) 34.1 kJ
b) 44.1 kJ
c) 54.1 kJ
d) 64.1 kJ
Q.8.
Arigid tank contains methane atkPa,K. It is now cooled down to 300K. Find the heat transfer.
a) –402.4 kJ
b) –502.4 kJ
c) –602.4 kJ
d) –702.4 kJ
Q.9.
A rigid container has 2kg of carbon dioxide gas atK,kPa that is heated toK. Find the heat transfer using heat capacity.
a) 231.2 kJ
b) 241.2 kJ
c) 251.2 kJ
d) 261.2 kJ
Q.10.
A piston cylinder contains 3kg of air at 20°C andkPa. It is now heated up in a constant pressure process toK. Find the heat transfer.
a) 941 kJ
b) 951 kJ
c) 961 kJ
d) 971 kJ
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