ELEMENTS OF
MECHANICAL ENGINEERING
IMPORTANT QUE FOR GTU EXAM
CH-3(PROPERTIES OF GASES)
Q.1 Explain
combined law pv=RT.
Q.2 Prove
that Cp – CV =R.
Q.3 Explain
isothermal process in details.
Q.4 Prove
that pvϒ=c for adiabatic process.
Q.5 Explain
Adiabatic process in details.
Q.6 Prove
heat transfer for polytropic process.
EXAMPLES
1.) 5kg of air is heated from 25·C
to 150·C. Determine 1. Specific heats 2.
I.E. 3.change in enthalpy 4. heat supplied. Assume
R=0.287 kj/kg.k and ϒ=1.4 for Air and work
done 500KJ.
2.) A gas whose pressure,volume and
temperature are 2.75 bar, 0.09m3 and 185°C respectively has the
state changed at constant pressure and until it’s temperature becomes 15°C. Calculate 1.Heat transferred 2.Work done. Take
R=0.29 kj/kg.k And Cp =1.005 kj/kg.k.
3.) 3kg of ethane gas is compressed
according to law pv1.3=constant from 1.013 bar,27°C to 8bar
pressure. Determine 1. Heat transferred, 2.work done, 3. I.E. Molecular weight
of ethane is 30 kg/kg.mol and Cp=1.75kj/kg.k
for ethane.assume ethane as a perfect gas.Take R0=8314.4 j/kg.mol.k
.
4.) One cubic meter of air at pressure of
1 bar and 60°C is compressed to final pressure 6 bar and volume .25m3.determine 1.mass air 2.index ‘n’ for compression 3.change in internal energy 4.heat transferred during compression.take ϒ=1.4 and R=287 j/kg.k
5.) In air compressor, air enters at 1.013
bar and 27°C having v=5
m3/kg and it is compressed to 12 bar isothermally.determine 1.work done 2.heat transfer and
3.change in internal energy.
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