MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 968 Mcqs, each offering curated multiple-choice questions to sharpen your GATE (Mechanical Engineering) knowledge and support exam preparation. Choose a topic below to get started.
| 751. |
Heat exchangers operating, when the asymptotic range is reached, |
| A. | Provide very large heat transfer co-efficient |
| B. | Results in making part of the heating surface inactive |
| C. | Results in abruptly increased velocity |
| D. | None of these |
| Answer» C. Results in abruptly increased velocity | |
| 752. |
'Duhring's plot' is of use in |
| A. | Extractive distillation |
| B. | Evaporation |
| C. | Leaching |
| D. | Absorption |
| Answer» C. Leaching | |
| 753. |
With increase in porosity, the thermal conductivity of a solid substance |
| A. | Increases |
| B. | Decreases |
| C. | Remains unchanged |
| D. | May increase or decrease; depends on the solid |
| Answer» C. Remains unchanged | |
| 754. |
The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is |
| A. | Nusselt number |
| B. | Sherwood number |
| C. | Schmidt number |
| D. | Stanton number |
| Answer» D. Stanton number | |
| 755. |
jH factor for heat transfer depends upon the __________ number. |
| A. | Biot |
| B. | Nusselt |
| C. | Reynolds |
| D. | Prandtl |
| Answer» D. Prandtl | |
| 756. |
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling? |
| A. | Square pitch |
| B. | Triangular pitch |
| C. | Diagonal square pitch |
| D. | None of these |
| Answer» C. Diagonal square pitch | |
| 757. |
A black body does not __________ radiation. |
| A. | Absorb or emit |
| B. | Refract |
| C. | Reflect |
| D. | Both B & C |
| Answer» E. | |
| 758. |
The range of electromagnetic spectrum important in heat transfer by radiation is __________ microns. |
| A. | 0.38-0.78 |
| B. | 0.5-50 |
| C. | 100-1000 |
| D. | 5-50 |
| Answer» C. 100-1000 | |
| 759. |
Correction is applied to LMTD for __________ flow. |
| A. | Parallel |
| B. | Counter |
| C. | Cross |
| D. | None of these |
| Answer» D. None of these | |
| 760. |
The non-dimensional temperature gradient in a liquid at the wall of a pipe is the |
| A. | Heat flux |
| B. | Nusselt number |
| C. | Prandtl number |
| D. | Schmidt number |
| Answer» B. Nusselt number | |
| 761. |
The most conducive surface for dropwise condensation to occur is the __________ surface. |
| A. | Coated |
| B. | Oily |
| C. | Glazed & polished |
| D. | Smooth |
| Answer» C. Glazed & polished | |
| 762. |
In case of heat transfer by conduction in a hollow cylinder, __________ mean area is used to calculate the heat transfer rate. |
| A. | Geometric |
| B. | Arithmetic |
| C. | Logarithmic |
| D. | Either A, B or C |
| Answer» D. Either A, B or C | |
| 763. |
Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is |
| A. | IR |
| B. | I²R |
| C. | IR² |
| D. | I²R² |
| Answer» C. IR² | |
| 764. |
In a forward feed multiple effect evaporator, the pressure is |
| A. | Highest in last effect |
| B. | Lowest in last effect |
| C. | Same in all effects |
| D. | Dependent on the number of effects |
| Answer» C. Same in all effects | |
| 765. |
Economy of a multiple effect evaporator depends upon the |
| A. | Heat balance consideration |
| B. | Rate of heat transfer |
| C. | Both A and B |
| D. | Neither A nor B |
| Answer» B. Rate of heat transfer | |
| 766. |
Absorptivity and refletivity of a perfect black body are respectively |
| A. | 1 and 0 |
| B. | 0 and 1 |
| C. | 1 and ? |
| D. | 0 and 0.5 |
| Answer» B. 0 and 1 | |
| 767. |
Natural convection is characterised by |
| A. | Grashhoff number |
| B. | Peclet number |
| C. | Reynolds number |
| D. | Prandtl number |
| Answer» B. Peclet number | |
| 768. |
Film boiling is usually not desired in commercial equipments, because |
| A. | The heat transfer rate is low in view of the large temperature drop |
| B. | It is difficult to maintain |
| C. | It is not economic |
| D. | None of these |
| Answer» B. It is difficult to maintain | |
| 769. |
A backward feed multiple effect evaporator is better than forward feed for concentrating cold feed, because it provides |
| A. | Higher economy |
| B. | Lower capacity |
| C. | Both A & B |
| D. | Lower economy |
| Answer» B. Lower capacity | |
| 770. |
Fouling factor for a heat exchanger is given by (where, U₁ = heat transfer co-efficient of dirty surface U₂ = heat transfer co-efficient of clean surface) |
| A. | U₁ - U₂ |
| B. | 1/U₁ - 1/U₂ |
| C. | 1/U₂ - 1/U₁ |
| D. | U₂ - U₁ |
| Answer» C. 1/U₂ - 1/U₁ | |
| 771. |
Choose the correct equation. |
| A. | Nu = (Re) (Pr) (Gz) |
| B. | Nu = (Re) (Pr) (St) |
| C. | Nu = (Re)(Pr) |
| D. | Nu = (Pr)(St) |
| Answer» C. Nu = (Re)(Pr) | |
| 772. |
A cube, sphere & a thin circular plate (all having same mass and made of same material) are all heated to 300°C and allowed to cool in natural air. Which one will cool the slowest ? |
| A. | Cube |
| B. | Plate |
| C. | Sphere |
| D. | All of the above |
| Answer» D. All of the above | |
| 773. |
1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m² and the overall heat transfer co-efficient to the liquid is 1500 W/m².°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be |
| A. | 15 min |
| B. | 22 min |
| C. | 44 min |
| D. | 51 min |
| Answer» E. | |
| 774. |
Which of the following is not concerned with the heat transfer? |
| A. | Brinkman number |
| B. | Stanton number |
| C. | Schmidt number |
| D. | Peclet number |
| Answer» D. Peclet number | |
| 775. |
Agitated film evaporator is suitable for concentrating __________ liquids. |
| A. | Foaming |
| B. | Viscous |
| C. | Very thin |
| D. | Corrosive |
| Answer» C. Very thin | |
| 776. |
Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called |
| A. | Radiation |
| B. | Natural convection |
| C. | Forced convection |
| D. | Conduction |
| Answer» D. Conduction | |
| 777. |
Solid angle subtended by the finite surface at the radiating element is |
| A. | Called the view factor |
| B. | Called the angle of vision |
| C. | Proportional to the square of the distance between surfaces |
| D. | Expressed in terms of radians |
| Answer» C. Proportional to the square of the distance between surfaces | |
| 778. |
The ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium. This is __________ law. |
| A. | Kirchoffs |
| B. | Planck's |
| C. | Wien's displacement |
| D. | Stefan-Boltzman |
| Answer» B. Planck's | |
| 779. |
In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid. |
| A. | Nucleate |
| B. | Pool |
| C. | Low pressure |
| D. | None of these |
| Answer» C. Low pressure | |
| 780. |
Baffle spacing |
| A. | Is not the same as baffle pitch |
| B. | Should be less than one fifth the diameter of the shell |
| C. | Should be less than the inside diameter of the shell |
| D. | None of these |
| Answer» D. None of these | |
| 781. |
Heat transfer co-efficient (h1) for liquids increases with |
| A. | Increasing temperature |
| B. | Decreasing temperature |
| C. | Decreasing Reynolds number |
| D. | None of these |
| Answer» B. Decreasing temperature | |
| 782. |
The interchange factor for radiation heat transfer from surface 'x' to surface 'y' in case of an infinite parallel planes with emis-sivities εx & εy is given by |
| A. | Εx + εy |
| B. | Εx . εy |
| C. | 1/εx + 1/εy |
| D. | (εx + εy)/(εx + εy - εx . εy) |
| Answer» E. | |
| 783. |
A tank painted with which of the following coloured paints, would heat up maximum by radiation from sun? |
| A. | Yellow paint |
| B. | White paint |
| C. | Black paint |
| D. | Grey paint |
| Answer» D. Grey paint | |
| 784. |
__________ paint has the maximum absorption coefficient. |
| A. | Black |
| B. | Yellow |
| C. | White |
| D. | Grey |
| Answer» B. Yellow | |
| 785. |
Stefan-Boltzman law applies to __________ body. |
| A. | Black |
| B. | White |
| C. | Grey |
| D. | Any colour |
| Answer» B. White | |
| 786. |
Wavelength corresponding to the maximum energy is inversely proportional to the absolute temperature. This is __________ law. |
| A. | Stefan's |
| B. | Dalton's |
| C. | Wien's |
| D. | Kirchoffs |
| Answer» D. Kirchoffs | |
| 787. |
Rate of crystallisation does not depend upon the |
| A. | Extent of supersaturation |
| B. | Turbulence within the solution |
| C. | Number and active surface area of the crystals |
| D. | None of these |
| Answer» E. | |
| 788. |
A body is called grey if the monochromatic emissivity of the body is |
| A. | Zero |
| B. | Unity |
| C. | Same for all wavelengths |
| D. | Different for all wavelengths |
| Answer» D. Different for all wavelengths | |
| 789. |
Which of the following is concerned with both heat and mass transfer? |
| A. | Lewis relationship |
| B. | Nusselt number |
| C. | Kutateladze number |
| D. | Froude number |
| Answer» B. Nusselt number | |
| 790. |
In a multiple effect evaporator, the effect of boiling point elevation is to |
| A. | Reduce the capacity |
| B. | Reduce the economy |
| C. | Increase the economy |
| D. | None of these |
| Answer» B. Reduce the economy | |
| 791. |
The rate of emission of radiation by a body does not depend upon the |
| A. | Wavelength of radiation |
| B. | Surface temperature of the body |
| C. | Nature of the surface |
| D. | Shape and porosity of the body |
| Answer» E. | |
| 792. |
The maximum heat transfer co-efficient from steam heating will be attained when the steam is |
| A. | Supersaturated |
| B. | Saturated |
| C. | Wet |
| D. | None of these |
| Answer» C. Wet | |
| 793. |
The main function of baffles provided in a shell and tube heat exchanger is to |
| A. | Facilitate the cleaning of outer tube surface |
| B. | Enhance turbulence |
| C. | Hold the tubes in position |
| D. | All of the above |
| Answer» C. Hold the tubes in position | |
| 794. |
At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical? |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | None of these |
| Answer» B. < 1 | |
| 795. |
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place |
| A. | Between two bodies in physical contact with each other |
| B. | Between two bodies not in physical contact with each other |
| C. | From one part of a body to the another part of the same body |
| D. | Both B & C |
| Answer» C. From one part of a body to the another part of the same body | |
| 796. |
In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is |
| A. | Infinity |
| B. | Zero |
| C. | Same as average heat transfer co-efficient for tube side |
| D. | None of these |
| Answer» B. Zero | |
| 797. |
Overall thermal resistance for conductive heat transfer through a series of flat resistances is equal to the |
| A. | Maximum resistance in the series |
| B. | Sum of all resistances |
| C. | Average of all resistances |
| D. | Minimum resistance presents in the series |
| Answer» C. Average of all resistances | |
| 798. |
The thermal efficiency of a reversible heat engine operating between two given thermal reservoirs is 0.4. The device is used either as a refrigerator or as a heat pump between the same reservoirs. Then the coefficient of performance as a refrigerator (COP)R and the co-efficient of performance as a heat pump (COP)HP are |
| A. | (COP)R = (COP)HP = 0.6 |
| B. | (COP)R = 2.5; (COP)HP = 1.5 |
| C. | (COP)R = 1.5; (COP)HP = 2.5 |
| D. | (COP)R = (COP)HP = 2.5 |
| Answer» D. (COP)R = (COP)HP = 2.5 | |
| 799. |
For a given ambient air temperature with increase in the thickness of insulation of a hot cylinderical pipe, the rate of heat loss from the surface would |
| A. | Decrease |
| B. | Increase |
| C. | First decrease and then increase |
| D. | First increase and then decrease |
| Answer» E. | |
| 800. |
The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation. |
| A. | Increases |
| B. | Decreases |
| C. | Remains constant |
| D. | May increase or decrease ; depends on the material |
| Answer» E. | |