Tiêu đề MECHANICAL ENGINEERING PAPER-1 SUBJECT-CODE-04.pdf ✅

1. In reciprocating air compressor the method .of controlling the quantity of air delivered is done by (A) Throttle control a) Blow-off control (C)\ Clearance control a) All of`the above 2. Heat transfer takes place according to the following law of thermo'dynanics (A) Zeroth a3) First (C) Second a)) Third 3. Heat transfer in liquid and gases is essentially due to (A) Conduction a3) Convection (C) RadiatioL a)) Conduction and Radiation 4. Which mode(s) of heat transfer does (do) not need a mat6rial medium ? (A) Conduction a) Convection (C) Radiation (D) Convection and Radiation 5. As the temperature increases, the thermal conductivity of a gas (A) increases a) decreases (C) remains constant a) increase upto a certain temperature and then decrease 04 6. Heatconduction in gases is due to (A) motion ofelectrons a) elastic impact of molecules (C) mixing motion of the different layers of the gas a) electromagnetic waves 7. Indicate the metal with highest thermal conductivity Steel Silver copper A1uniniun 8. Identifytheverygood insulator (A) Sawdust a) Glasswool (C) Cork a) Asbestos sheet 9. Theunitofthemal diffusivityis (A) m2th|.oc @) kcal/m2-hr (C) mthr°C @) in?dr 10. Critical thickness of inenlation for spheres is given by (A)in a3) Kr47,h (C) hex @)2m Series-A
11. Fins are provided on heat transforming surface in order to increase (A) heat transfer area (8) heat transfer coefficient (C) temperature gradient a) mechanical strength equipment of 12. Firmed surfaces have improved rate of heat dissipation due to (A) decrease in ambient temperature. a) increase in the surface area exposed to the surrounding. (C) increase in the corrective film coefficient. a) Alloftheabove 13. An increase in fin effectiveness is c'ausedby highvalue of , (A) convective coefficient (8) themal conductivity (C) Oil.cumference a) a3)and(c) 14. Transient conduction means (A) very little heat transfer. a) heat transfer for a short time. (C) heat transfer with a very small temperature difference. (D) conduction when the temperature at a point varies with time. 15. In the lumped parameter model, the temperature variation with time is ` (A) Linear a) cubic (C) Exponential a) Sinusoidal Series-J@ I 16. Heat transfer by Radiation is encountered least in (A) Boiler furnace a) Insulated steam pipe (C) Electric bulb a) Nuclear reactor 17. Absorptivity of a body is equal to its emissivity (A) forapolishedbody a3) under thermal equilibrium condition (C) at one particular temperature a) at shorter wavelengths 18. The emissivity is likely t,o be higher in case of _ (A)` Rubber a) Paper (C) Carbon a) Ironoxide 19. The emissivity and the absorptivity ofa real surface are equal for radiation with identical temperature and wavelength. This law is referred as (A) Lambert's lil (8) ELchoffs law (C) Planck's law a) Wien's displacement law 20. Which parameter should be highest for a radiation shield ? (A) Absorptivity a) Reflectivity (C) Transmissivity ' a) Emissivity 04
21. The gray body shape factor for radiant heat exchange between a small body (emissivity 0.4) in a large enclosure (emissivity 0.5) is (A) o.1 @) 0.2 . (C) 0.4 @) 0.5 22. Free convection heat flow depends on all of the following, except : (A) 1 ,Density a) Coefficient ofviscosity (C) Gravitational force a) velocity 23. The ratio of kinematic viscosity to thermal diffusivity is known as (A) Prandtl number (8) Nu§selt number (C) Pedetnumber (D) Schmidtnumber 24. The prandtl number will be lowest for (A) Water (8) Liquidmetal (C) .Aqueous solution a) Lubeoil 25. ` Dropwise condensation usually occurs On (A) Glazed surface a) Smooth surface (C) Oily surface a) Coated surface 04 26. In Bell-Colemann refrigerator for the same temperature range (A) cop of dense air system is higher than COP of open air system. i (B) tch°anp63Se:;eo;=nsr:t:;st]:::Wer (C) cop of dense air system is equal to COP of open alr system. a) cop of dense air system may be higher or lower than COP of open air system depending upon pressure ratio. 27. Heat is rejected by the refrigerant, during vapour compression refrigeration cycle in I (A) Condenser i ,£) ia:p;:r:;?rve 28. A domestic refrigerator capacity may be approximately (A) lton i S)::;::: (D) 10ton 29. In a domestic vapour compression reffigerator the refrigerant used is (A) C02 I ` @) Freon-12 I (C) Ammonia I a) All of the above 30. In vapour compression refrigeration system, if expansion cylinder is used in place of throttle valve, the COP will i (A) increase a) decrease i S} ¥i::i:::Pa:¥iiscfabol: unless S`eries-A I- E.