Partner Sites
IOCL Mechanical Technical Paper
1. In an ideal vapour compression refrigeration cycle, the specific enthalpy of refrigerant (in kJ/kg) at the following states is given as:
Inlet of condenser: 283
Exit of condenser: 116
Exit of evaporator: 232
The COP of this cycle is
(A) 2.27
(B) 2.75
(C) 3.27
(D) 3.75
2. The rotor shaft of a large electric motor supported between short bearings at both deflection of 1.8mm in the middle of the rotor. Assuming the rotor to be perfectly balanced and supported at knife edges at both the ends, the likely critical speed (in rpm) of the shaft is
(A) 350
(B) 705
(C) 2810
(D) 4430
3. The effective number of lattice points in the unit cell of simple cubic, body centered cubic, and face centered cubic space lattices, respectively, are
(A) 1,2,2
(B) 1,2,4
(C) 2,3,4
(D) 2,4,4
4. Friction at the tool-chip interface can be reduced by
(A) decreasing the rake angle
(B) increasing the depth of cut
(C) decreasing the cutting speed
(D) increasing the cutting speed
5. Two streams of liquid metal, which are not hot enough to fuse properly, result into a casting defect known as
(A) cold shut
(B) swell
(C) sand wash
(D) scab
6. Which of the following is the correct data structure for solid models?
(A) solid part --> faces --> edges --> vertices
(B) solid part--> edges--> faces--> vertices
(C) vertices --> edges--> faces --> solid parts
(D) vertices-->faces-->edges-->solid parts
7. Which of the following forecasting methods takes a fraction of forecast error into account for the next period forecast?
(A) simple average method
(B) moving average method
(C) weighted moving average method
(D) exponential smoothening method
8. In an air-standard Otto cycle, the compression ratio is 10. The condition at the beginning of the compression process is 100kPa and 27°C. Heat added at constant volume is 1500kJ/kg, while 700kJ/kg of heat is rejected during the other constant volume process in the cycle. Specific gas constant for air=0.287 kJ/kgK.The mean effective pressure (in kPa) of the cycle is
(A) 103
(B) 310
(C) 515
(D) 1032
9. An irreversible heat engine extracts heat from a high temperature source at a rate of 100kW and rejects heat to a sink at a rate of 50kW. The entire work output of the heat engine is used to drive a reversible heat pump operating between a set of independent isothermal heat reservoirs at 17°C and 75°C. The rate (in kW) at which the heat pump delivers heat to its high temperature sink is
(A) 50
(B) 250
(C) 300
(D) 360
10. In a parallel flow heat exchanger operating under steady state, the heat capacity rates (product of specific heat at constant pressure and mass flow rate) of thehot and cold fluid are equal. The hot fluid, flowing at 1kg/s with Cp = 4kJ/kgK,enters the heat exchanger at 102°C while the cold fluid has an inlet temperature of 15°C. The overall heat transfer coefficient for the heat exchanger is estimated to be 1kW/m2K and the corresponding heat transfer surface area is 5m2. Neglect heat transfer between the heat exchanger and the ambient. The heat exchanger is characterized by the following relation: 2e = 1 â exp (â2NTU) .The exit temperature (in °C) for the cold fluid is
(A) 45
(B)55
(C) 65
(D) 75
11. Water at 25°C is flowing through a 1.0km long G.I pipe of 200mm diameter at the rate of 0.07m3/s. If value of Darcy friction factor for this pipe is 0.02 and density of water is 1000kg/m3, the pumping power (in kW) required to maintain the flow is
(A) 1.8
(B) 17.4
(C) 20.5
(D) 41.0
12. A forged steel link with uniform diameter of 30mm at the centre is subjected to an axial force that varies from 40kN in compression to 160kN in tension. The tensile (Su),yield (Sy) and corrected endurance (Se) strengths of the steel material are 600MPa, 420MPa and 240MPa respectively. The factor of safety against fatigue endurance as per Soderbergâs criterion is
(A) 1.26
(B) 1.37
(C) 1.45
(D) 2.00
13. An automotive engine weighing 240kg is supported on four springs with linear characteristics. Each of the front two springs have a stiffness of 16MN/m while the stiffness of each rear spring is 32MN/m. The engine speed (in rpm),at which resonance is likely to occur, is
(A) 6040
(B) 3020
(C) 1424
(D) 955
14. A vehicle suspension system consists of a spring and a damper. The stiffness of the spring is 3.6kN/m and the damping constant of the damper is 400Ns/m. If the mass is 50kg, then the damping factor (d) and damped natural frequency (fn),respectively, are
(A) 0.471 and 1.19Hz
(B) 0.471 and 7.48Hz
(C) 0.666 and 1.35Hz
(D) 0.666 and 8.50Hz
15. A company uses 2555 units of an item annually. Delivery lead time is 8 days. The recorder point (in number of units) to achieve optimum inventory is
(A) 7
(B) 8
(C) 56
(D) 60
16. Minimum shear strain in orthogonal turning with a cutting tool of zero rake angle is
(A) 0.0
(B) 0.5
(C) 1.0
(D) 2.0
Statement for Questions: 17 & 18
A 20º full depth involute spur pinion of 4mm module and 21 teeth is to transmit 15kW at 960rpm. Its face width is 25mm.
17. The tangential force transmitted (in N) is
(A) 3552
(B) 2611
(C) 1776
(D) 1305
18. Given that the tooth geometry factor is 0.32 and the combined effect of dynamic load and allied factors intensifying the stress is 1.5; the minimum allowable stress (in MPa) for the gear material is
(A) 242.0
(B) 166.5
(C) 121.0
(D) 74.0
Common Data Questions: 19 & 20
Radiative heat transfer is intended between the inner surfaces of two very large isothermal parallel metal plates. While the upper plate (designated as plate 1) is a black surface and is the warmer one being maintained at 727ºC, the lower plate (plate 2) is a diffuse and gray surface with an emissivity of 0.7 and is kept at 227ºC. Assume that the surfaces are sufficiently large to form a two-surface enclosure and steady state conditions to exist. Stefan Boltzmann constant is given as 5.67Ã10-8W/m2K4
19. The irradiation (in kW/m2) for the upper plate (plate 1) is
(A) 2.5
(B) 3.6
(C) 17.0
(D) 19.5
20. If plate 1 is also a diffuse and gray surface with an emissivity value of 0.8, the net radiation heat exchange (in kW/m2) between plate 1 and plate 2 is
(A) 17.0
(B) 19.0
(C) 23.0
(D) 31.7
