# Thermodynamics (21-30)

21.  Isentropic flow is
 A. Irreversible adiabatic flow B. Perfect gas flow C. Ideal fluid flow D. Reversible adiabatic flow E. Frictionaless reversible flow

Explanation:

22.  Triple point temperature and pressure for water are
 A. 100?C and 1 ata B. 0?C 1 ata C. 0?C and 0.1 ata D. 0.1?C and 0.006028 ata E. 0.01?C and 0.006028 ata

Explanation:

 A. 6.02486 x 1026 molecules/(k mol) B. 60.2486 x 1026 molecules/(k mol) C. 602.486 x 1026 molecules/(k mol) D. 6024.86 x 1026 molecules/(k mol) E. 60248.6 x 1026 molecules/(k mol)

Explanation:

24.  The unit of universal gas constant is
 A. erg/?K B. kcal/?K C. W/?K D. dynes/?K E. W/m?K

Explanation:

25.  In the regenerative cycle
 A. Steam is reheated after expansion and again used B. Power is generated in two stages C. Part of the steam is withdrawn from the turbine and is used in heating the steam being supplied to the turbine D. Part of the steam is withdrawn from the turbine and is used in heating the feed water E. Part of the steam is withdrawn from the turbine and is utilised in heating the exhaust steam

Explanation:

26.  If a heat engine gives an output of 3 kW and input is 10,000 J/s the thermal efficiency of the engine will be
 A. 30% B. 33.30% C. 66.60% D. 70% E. 100%

Explanation:

27.  A reversible process requires that
 A. There be no heat transfer B. Newton’s law of viscosity be satisfied C. Temperature of system and surroundings be equal D. There whould be no viscous or coulomb friction in the system E. Heat transfer occurs from surrounding to system only

Explanation:

28.  The critical pressure at which latent heat of vaporisation for water is zero is
 A. 100 kg/cm2 B. 215.1 kg/cm2 C. 228.6 kg/cm2 D. 235.6 kg/cm2 E. 250.6 kg/cm2

Explanation:

29.  1 kgf/cm2 is equal to
 A. 1 mm Hg B. 100 mm Hg C. 735.6 mm Hg D. 760 mm Hg E. 776 mm Hg

Explanation:

30.  The first law of thermodynamics, for steady flow
 A. Accounts for all energy entering and leaving a control volume B. Is an energy balance for the specified mass of fluid C. Is an expression of the conservation of linear momentum D. Is primarily concerned with heat transfer E. Is restricted in its application to perfect gases