Tuesday, 5 March 2019

ISRO RAC 2017 Question paper with Answers

SOLUTION OF THE WRITTEN TEST BY ISRO FOR SCIENTIST/ENGINEER 'SC' (REFRIGERATION & AIRCONDITIONING) [BE006 & BE010] -2017


41. A long glass cylinder of inner diameter 0.03 m and outer diameter 0.05 m carries hot fluid inside. If the thermal conductivity of glass is 1.05 W/mK, the thermal resistance per unit length of the cylinder is   
(a) 0.031                             (b) 0.077                             (c) 0.017                          (d) 0.77




42. In heat exchangers, degree of approach is defined as the difference between temperatures of
(a) cold water inlet and outlet
(b) hot medium inlet and outlet
(c) hot medium outlet and cold water inlet
(d) hot medium outlet and cold water outlet

Excluded for evaluation


43. In counter flow heat exchangers between two fluids,
(a) Both the fluids at inlet are in their hottest state
(b) Both the fluids at exit are in their hottest state
(c) One fluid in hottest state and the other in coldest state
(d) Any combination possible depending heat exchanger design

Excluded for evaluation

44. Log mean temperature difference in case of counter flow heat exchanger compared to
parallel flow heat exchanger will be :
(a) same                                                                        (b) more
(c) less                                                                          (d) depends on other factors




45. The emissive power of a body depends on:
(a) temperature                                                                            (b) wave length
(c) physical nature                                                                       (d) all of these




46.The outside diameter of hollow shaft is twice that of its inside diameter. The ratio of
its torque carrying capacity to that of solid shaft of the same material and same
outside diameter is :
(a) 15/16                    (b) 1/8                       (c) 3/4                    (d) 1/16



47. The designation M 33 × 2 of a bolt means
(a) Metric thread of 33 nos in 2 cm
(b) Metric thread with cross section area of 33 mm2
(c) Metric threads of 33 mm outside diameter and 2 mm pitch
(d) Bolt of 33 mm nominal diameter having 2 threads per cm.




48. The power transmitted by means of belt drives depends upon :
(a) Velocity of the belt
(b) Tension under which the belt is placed on the pulleys
(c) Arc of contact between the belt and the smaller pulley
(d) All of the above




49. The usual proportion for the width of the key used between shaft (of diameter d) and
hub of pulley for transmitting power is
(a) d/8                             (b) d/6                             (c) d/2                          (d) d/4



50. The helix angle for single helical gears ranges from
(a) 10° to 15°                     (b) 15° to 20°                    (c) 20° to 35°                      (d) 35° to 45°




51. The air standard efficiency of a standard otto cycle for compression ratio of 5.5 is
(a) 25%                        (b) 50%                           (c) 70%                          (d) 90%



52. The power actually developed by the engine cylinder of an I.C engine is known as
(a) Theoretical pressure                                                                       (b) Actual power
(c) Indicated power                                                                              (d) Break horse power



53. In a boiler, feed water is supplied per hour is 205 kg while coal fired per hour is 23 kg. Net enthalpy rise per kg of water is 145 kJ for conversion to steam. If the calorific value of coal is 2050 kJ/kg, boiler efficiency will be
(a) 78%                              (b) 74%                                      (c) 63%                                 (d) 58%



54. Which of the following power plant is least polluting and causing least environmental concern?
(a) Hydro electric plant                                                                       (b) solar power plant
(c) Nuclear plant                                                                                 (d) gas power plant



55. A diesel power station has fuel consumption of 0.2 kg per kWh. If the calorific value of
diesel is 11000 kcal per kg, overall efficiency of power station is
(a) 43.3%                            (b) 65.5%                              (c) 39.2%                             (d) 25.6%



56. In aircraft, air refrigeration is used because of
(a) low weight per ton of refrigeration                                                (b) high heat transfer rate
(c) low temperature at high altitudes                                                   (d) higher coefficient of performance




57. A reversible engine has ideal thermal efficiency of 30%. When it is used as refrigerating machine with all other conditions unchanged, the coefficient of performance will be
(a) 1.33                                (b) 2.33                                 (c) 3.33                                  (d) 4.33



58. In Vapour compression system, the condition of refrigerant before passing through the condenser is
(a) Saturated liquid                                                                               (b) wet vapour
(c) Dry saturated vapour                                                                       (d) superheated vapour



59. Lithium bromide in vapour absorption refrigeration system is used as
(a) refrigerant                                                                                (b) lubricant
(c) cooling medium                                                                       (d) absorbent




60. In refrigeration cycle, sub cooling occurs when
(a) Latent heat from refrigerant is removed
(b) Sensible heat from refrigerant is removed
(c) Refrigerant has low latent heat removed
(d) Refrigerant has high thermal conductivity





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