Indian Institute of Technology Madras (IIT-M) 2003 M.Tech Mechanical Engineering mechanical engg-gate - Question Paper

48. Consider a laminar boundary layer over a heated flat plate. The free stream velocity is U.
At a few distance x from the leading edge the velocity boundary layer thickness is Yand the
thermal boundary layer thickness is ‘5T If the Prandtl number is greater than 1, then
(a) 5v>5T
(b) 5T>5v
(c) T (Ux)112
(d) T X’
49. Considering the relationship TdS=dU+pdV ranging from the entropy (S), internal energy (U),
pressure (p), temperature (T) and quantity (V), which of the subsequent statements is correct?
(a) It is applicable only for a reversible process
(b) For an irreversible process, TdS > dU + pdV
(c) It is valid only for an ideal gas
(d) It is equivalent to one law, for a reversible process
50. In a gas turbine, hot combustion products with the specific heats C = 0.98 kJ/kgK,
C=0.7538 kJ/kg K enter the turbine at 20 bar, 1500 K and exit at one bar.
The isoentropic efficiency of the turbine is 0.94. The work developed by the
turbine per kg of gas flow is
(a) 689.64 kJ/kg
(b) 794.66 kJ/kg
(c) 1009.72 kJ/kg
(d) 1312.00 kJ/kg
51. An automobile engine operates at a fuel air ratio of 0.05, volumetric efficiency of
90% and indicated thermal efficiency of 30%. provided that the calorific value of the fuel is 45
MJ/kg and the density of air at intake is one kg/m3, the indicated mean effective pressure for
the engine is
(a) 6.075 bar
(b) 6.75 bar
(c) 67.5 bar
(d) 243 bar

52. For an engine operating on air standard Otto cycle, the clearance quantity is 10% of the
swept quantity. The specific heat ratio of air is 1.4. the air standard cycle
efficiency is
(a) 38.3°h
(b) 39.8°h
(c) 60.2°h
(d)61.7°h
53. A centrifugal pump running at 500 rpm and at its maximum efficiency is delivering a head
of 30m at a flow rate of 60 litres per minute. If the rpm is changed to 1000, then the head H
in metres and flow rate Q in litres per minute
at maximum efficiency are estimated to be
(a) H=60,Q= 120
(b) H= 120,Q= 120
(c) H = 60, Q = 480
(d) H = 120, Q = 30
54. Hardness of steel greatly improves with
(a) annealing

Earning:   Approval pending.