21. Two crossed helical gears are used for speed reduction. Gear A has pitch circle diameter in the plane of rotation 80mm and helix angle 30 deg; Gear B has pitch circle diameter in the plane of rotation 120mm and helix angle 22.5 deg. If the input speed is 1440 RPM, thenoutput speed in RPM is
(a) 1200 (b) 875
(c) 900 (d) 700
22. The moisture in a refrigerant is removed by:
(a) dehumidifiers (b) safety relief vale
(c) driers (d) expansion valve
23. In an arc welding process, the voltage and current are 25 V and 300 A respectively. The arc heat transfer efficiency is 0.85 and welding speed is 8 mm/sec the net heat input (in J/mm)
(a) 64 (b) 797
(c) 1103 (d) 79700
24. Hardness of steel greatly improves with
(a) annealing (b) cyaniding
(c) normalizing (d) tempering
25. Work Material Type of Joining
P Aluminium 1. Submerged Arc Welding
Q Die Steel 2. Soldering
R Copper Wire 3. Thermit Welding
S Titanium Shet 4. Aromic Hydrogen Welding
5. Gas Tungsten Arc Welding
6. Laser Beam Welding
(a) P-2, Q-5, R-1, S-3 (b) P-6, Q-3, R-4, S-4
(c) P-4, Q-1, R-6, S-2 (d) P-5, Q-4, R-2, S-6
26. List A List B
P Isobaric thermal expansion coefficient 1. 0
Q Isothermal compressibility 2. ∞
R Isentropic compressibility 3. 1/v
S Joule Thomson Coefficient 4. 1/T
5. 1/P
6. 1/γp
(a) P-4, Q-2, R-3, S-6 (b) P-3, Q-5, R-4, S-1
(c) P-2, Q-4, R-1, S-5 (d) P-4, Q-5, R-6, S-1
27. If the mass of moist air in an airtight vessel is heated to a higher temperature, then
(a) Specific humidity of air increases (b) Specific humidity of air decreases
(c) Relative humidity of air increases (d) Relative humidity of air decreases
28. Threaded bolts of A and B of same material and length are subjected to identical tensile load. If the elastic strain energy stored in bolt A is 4 times that of bolt B and the mean diameter of bolt A is 12 mm, then mean diameter of bolt B is
(a) 16 (b) 24
(c) 36 (d) 48
29. In a condenser of a power plant, the steam condenses at a temperature at a 333 K. The cooling water enters at 303 K and leaves at 318 K. The logarithmic mean temperature difference (LMTD) of the condenser is
(a) 16.2 C (b) 21.6 C
(c) 30 C (d) 37.5 C
30. The shear strength of a sheet metal is 300 Mpa. The blanking force required to produce a blank of 100 mm diameter from a 1.5 mm thick sheet is
(a) 45 kN (b) 70 kN
(c) 141 kN (d) 350 kN
31. A heat engine is supplied heat at the rate of 1700 kJ/min and gives an output of 9 kW. Thermal efficiency and heat rejection in kW of heat engine is
(a) 34.0%, 11.0 (b) 28.3%, 10.0
(c) 31.76%, 19.33 (d) 32.3%, 9.83
32. When we have combined free and forced convection, Gr/Re^2 is
(a) greater than 1 (b) less than 1
(c) almost equal to 1 (d) equal to Peclet Number
33. A refrigerator and heat pump operate between the same temperature limits. COP of refrigerator is 4, COP of heat pump would be
(a) 3 (b) 5 (c) 4 (d) data not adequate
34. A carnot refrigerator requires 1.25 kW per ton of refrigeration to maintain a temperatue of 233 K. Its higher operating temperature of the cycle
(a) 318 K (b) 313 K (c) 315 K (d) 316 K
35. The work input to air compressor is minimum if the compression law followed is
(a) isentropic (b) PV =C (c) $PV^1.2 =C$ (d) $VP^1.35 =C$
36. Operating pressure of the refrigerants at the evaporator in the ascending order for any application are
(a) R11, R12, R717, R22 (b) R22, R717, R12, R11
(c) R11, R12, R22, R717 (d) R717, R22, R11, R12
37. For vapour compression system using R717 the material of pipe is
(a) Steel (b) Copper (c) Brass (d) Aluminium
38. Air at DBT of 308K and DPT of 293 K passes through a cooling coil which is maintained at 298 K. The process would be
(a) cooling and de-humidification (b) sensible cooling
(c) cooling and humidification (d) can not predict
39. Room sensible heat loss is 30000 kJ/min and room latent heat loss is 20000 kJ/min. Sensible heat factor is
(a) -0.6 (b) 0.6 (c) 0.3 (d) 3
40. Domestic refrigerator working on vapour compression cycle uses the following of expansion device
(a) Manually operated valve
(b) thermostatic valve
(c) expansion valve
(d) capillary tube
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