Thermodynamics: Quick recap(questions)


1. The definition of 1 K as per the internationally accepted temperature scale is
(a) 1/100th the difference between normal boiling point and normal freezing point of water
(b) 1/273.15th the normal freezing point of water
(c) 100 times the difference between the triple point of water and the normal freezing point ‘ of water
(d) 1/273.16‘“ of the triple point of water

2.The volume and temperature of air (assumed to be an ideal gas) in a closed vessel is 2.87 m3 and 300 K. respectively. The gauge pressure indicated by a manometer fitted to the wall of the vessel is 0.5 bar. If the gas constant of air is R = 287 J/kgK and the atmospheric pressure is 1 bar, the mass of air (in kg) in the vessel is
(a) 1.67
(b) 3.33
(C) 5-00
(d) 6.66

3.Air expands steadily through a turbine from 6 bar, 800 to 1 bar, 520 K. During the expansion, heat transfer from air to the surroundings at 300 K is 10 kj/kg air. Neglect the changes in kinetic and potential energies and evaluate the irreversibiiity per kg air. Assume air to behave as an ideai gas with Cp=1.0 kj/kgk and R=0.3/KgK




Ans:
1.(d)
2.(c)
3. 42.03 kj/kg