MCQOPTIONS
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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.
| 801. |
Which has the lowest Prandtl number? |
| A. | Liquid metal |
| B. | Aqueous solution |
| C. | Water |
| D. | Lube oil |
| Answer» B. Aqueous solution | |
| 802. |
Which of the following has the lowest Prandtl number? |
| A. | Molten sodium (a coolant used in fast breeder reactor) |
| B. | Water |
| C. | Transformer oil |
| D. | Dilute H₂SO₄ |
| Answer» B. Water | |
| 803. |
Electro-magnetic spectrum range, which is important for radiation varies from __________ microns. |
| A. | 1 to 100 |
| B. | 0.5 to 50 |
| C. | 10 to 100 |
| D. | 100 to 1000 |
| Answer» C. 10 to 100 | |
| 804. |
Vent pipes are provided in a condenser to |
| A. | Remove non-condensable gases |
| B. | Purge the condenser |
| C. | Facilitate easy cleaning of tubes |
| D. | None of these |
| Answer» B. Purge the condenser | |
| 805. |
It is not preferable to use superheated steam in evaporators, because of its very |
| A. | High temperature |
| B. | High pressure |
| C. | Low film co-efficient |
| D. | None of these |
| Answer» D. None of these | |
| 806. |
__________ chart is known as transient heat conduction chart. |
| A. | Dirhing's |
| B. | Heisler's |
| C. | Mollier's |
| D. | Cox |
| Answer» B. Heisler's | |
| 807. |
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids? |
| A. | At high fluid velocity |
| B. | At low velocity |
| C. | When fluid flows past a smooth surface |
| D. | None of these |
| Answer» B. At low velocity | |
| 808. |
In a heat exchanger, one transfer unit means |
| A. | A section of the exchanger in which change in temperature of one stream equals the average driving force in the section |
| B. | The size of the exchanger in which heat transfer rate is 1 kcal/hr |
| C. | Both A and B |
| D. | None of these |
| Answer» B. The size of the exchanger in which heat transfer rate is 1 kcal/hr | |
| 809. |
For large heat transfer area requirement, shell and tube heat exchanger is preferred, because it |
| A. | Occupies smaller space |
| B. | Is more economical |
| C. | Is easy to operate and maintain |
| D. | All of the above |
| Answer» E. | |
| 810. |
Shell side pressure drop in a shell and tube heat exchanger does not depend upon the |
| A. | Baffle spacing & shell diameter |
| B. | Tube diameter & pitch |
| C. | Viscosity, density & mass velocity of shell side fluid |
| D. | None of these |
| Answer» E. | |
| 811. |
An insulator should have |
| A. | Low thermal conductivity |
| B. | High thermal conductivity |
| C. | Less resistance to heat flow |
| D. | A porous structure |
| Answer» B. High thermal conductivity | |
| 812. |
An ejector is used to |
| A. | Increase pressure |
| B. | Increase temperature |
| C. | Remove condensate |
| D. | None of these |
| Answer» E. | |
| 813. |
A hollow sphere and a solid sphere of the same material and equal radii are heated to the same temperature. In this case, |
| A. | The cooling rate will be the same for the two spheres and hence the two spheres will have equal temperatures at any instant |
| B. | Both the spheres will emit equal amount of radiation per unit time in the beginning |
| C. | Both will absorb equal amount of radiation from the surrounding in the beginning |
| D. | Both B & C |
| Answer» E. | |
| 814. |
Dietus-Boelter equation cannot be used for molten metals mainly due to its very low |
| A. | Prandtl number |
| B. | Grashoff number |
| C. | Thermal conductivity |
| D. | Viscosity |
| Answer» B. Grashoff number | |
| 815. |
In case of vertical tube evaporator, with increase in liquor level, the overall heat transfer co-efficient |
| A. | Increases |
| B. | Decreases |
| C. | Is not affected |
| D. | May increase or decrease; depends on the feed |
| Answer» C. Is not affected | |
| 816. |
Prandtl and Reynold's analogies are identical for Prandtl number value of |
| A. | 0 |
| B. | 0.5 |
| C. | 1 |
| D. | 5 |
| Answer» D. 5 | |
| 817. |
Vacuum is generally maintained in the vapour space of an evaporator mainly to |
| A. | Get economical temperature difference by using moderate pressure steam |
| B. | Facilitate forward feeding in multiple effect evaporation |
| C. | Concentrate heat sensitive materials |
| D. | Achieve very high concentration of the final product |
| Answer» B. Facilitate forward feeding in multiple effect evaporation | |
| 818. |
What is the absorptivity of a black body? |
| A. | 1 |
| B. | 0 |
| C. | 0.78 |
| D. | 0.95 |
| Answer» B. 0 | |
| 819. |
Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is |
| A. | 0.5 |
| B. | 2 |
| C. | 10 |
| D. | 100 |
| Answer» C. 10 | |
| 820. |
Nusselt number for full developed, laminar, constant property flow in a pipe at uniform heat flux is |
| A. | 0.72 |
| B. | 4.364 |
| C. | 18 |
| D. | 83 |
| Answer» C. 18 | |
| 821. |
A dephlegmator is a |
| A. | Total condenser |
| B. | Vacuum evaporator |
| C. | Partial condenser |
| D. | Double pipe heat exchanger |
| Answer» D. Double pipe heat exchanger | |
| 822. |
A BTU/hr.ft.2 °F is equal to |
| A. | 1 kcal/hr. m²°C |
| B. | 4.88 kcal/hr. m.2°C |
| C. | 1 kcal/hr. m².°K |
| D. | None of these |
| Answer» C. 1 kcal/hr. m².°K | |
| 823. |
A 2-4 heat exchanger involves |
| A. | Only counter-flow of fluids |
| B. | Only parallel-flow of fluids |
| C. | Both counter and parallel-flow of the fluids |
| D. | Smaller pressure drop compared to 1-2 exchanger |
| Answer» D. Smaller pressure drop compared to 1-2 exchanger | |
| 824. |
A metal wire of 0.01 m dia and thermal conductivity 200 W/m.K is exposed to a fluid stream with a convective heat transfer coefficient of 100 W/m².K. The Biot number is |
| A. | 5.6 |
| B. | 0.025 |
| C. | 3.5 |
| D. | 0.0035 |
| Answer» C. 3.5 | |
| 825. |
For condensation of pure vapors, if the heat transfer co-efficients in filmwise and drop-wise condensation are respectively hf and hd, then |
| A. | hf = hd |
| B. | hf > hd |
| C. | hf < hd |
| D. | hf could be greater or smaller than hd |
| Answer» D. hf could be greater or smaller than hd | |
| 826. |
The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances. |
| A. | Average |
| B. | Geometric mean |
| C. | Product |
| D. | Sum |
| Answer» E. | |
| 827. |
The film thickness for laminar film condensation on vertical surface __________ from top to bottom. |
| A. | Cummulatively increases |
| B. | Cummulatively decreases |
| C. | Remains constant |
| D. | And the surface conductance increase |
| Answer» B. Cummulatively decreases | |
| 828. |
Heat flux, as defined in heat flow is analogous to __________ in electricity flow. |
| A. | Current |
| B. | Voltage |
| C. | Resistance |
| D. | None of these |
| Answer» B. Voltage | |
| 829. |
The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoffs law. |
| A. | Wavelength of radiation |
| B. | Nature of the body |
| C. | Temperature of the body |
| D. | None of these |
| Answer» D. None of these | |
| 830. |
The separation of liquid droplets from the vapor is done by a/an __________ , in the evaporators. |
| A. | Steam ejector |
| B. | Entrainment separator |
| C. | Compressor |
| D. | Vacuum pump |
| Answer» C. Compressor | |
| 831. |
At constant temperature, the thermal conductivities of gases __________ with rise in pressure. |
| A. | Decrease |
| B. | Increase |
| C. | Remain unchanged |
| D. | May increase or decrease; depends on the pressure |
| Answer» B. Increase | |
| 832. |
A graph between __________ is called Wilson plot. |
| A. | 1/U Vs . 1/v0.8 |
| B. | 1/v0.8 Vs . U |
| C. | V0.8 Vs . U |
| D. | 1/U Vs . 1/V |
| Answer» B. 1/v0.8 Vs . U | |
| 833. |
Trap is used to remove __________ from steam pipe lines. |
| A. | Steam |
| B. | Condensate |
| C. | Non-condensables |
| D. | None of these |
| Answer» C. Non-condensables | |
| 834. |
Radiator of an automobile engine is a __________ type of heat exchanger. |
| A. | Co-current |
| B. | Cross-current |
| C. | Counter-current |
| D. | Direct contact |
| Answer» E. | |
| 835. |
In case of a multipass shell and tube heat exchanger, providing a baffle on the shell side __________ the heat transfer rate. |
| A. | Increases |
| B. | Decreases |
| C. | Does not affect |
| D. | May increase or decrease, depends on the type of baffle |
| Answer» B. Decreases | |
| 836. |
The equivalent diameter for pressure drop is __________ that for heat transfer. |
| A. | Smaller than |
| B. | Greater than |
| C. | Equal to |
| D. | Not related with |
| Answer» B. Greater than | |
| 837. |
The film co-efficient between condensing vapour and metal wall increases with |
| A. | Increasing temperature of the vapour |
| B. | Decreasing temperature of the vapour |
| C. | Increasing viscosity of the film of condensate |
| D. | Increasing temperature drop |
| Answer» B. Decreasing temperature of the vapour | |
| 838. |
A single pass air heater is connected to a two pass unit. For the air flow rate and other conditions remaining the same, the film heat transfer co-efficient for air will vary in the ratio of |
| A. | 2 |
| B. | 20.8 |
| C. | 20.2 |
| D. | 20.5 |
| Answer» C. 20.2 | |
| 839. |
Stefan-Boltzman law which describes the radiation heat transfer states that, it is proportional to (where, t = temperature in °C T = absolute temperature in ° K ) |
| A. | t⁴ |
| B. | T⁴ |
| C. | 1/t⁴ |
| D. | 1/T⁴ |
| Answer» C. 1/t⁴ | |
| 840. |
Evaporation of 1kg of water from a solution in a single effect evaporator requires about __________ kg of steam. |
| A. | 0.4 - 0.6 |
| B. | 1-1.3 |
| C. | 1.8-2 |
| D. | 2 - 2.4 |
| Answer» C. 1.8-2 | |
| 841. |
For the same heat transfer area and the terminal conditions, the ratio of the capacities of a single effect evaporator to a triple effect evaporator is |
| A. | 3 |
| B. | 0.33 |
| C. | 1 |
| D. | 1.33 |
| Answer» D. 1.33 | |
| 842. |
Thermal conductivities of most of the liquids __________ with rise in temperature. |
| A. | Increases |
| B. | Decreases |
| C. | Remains unchanged |
| D. | May increase or decrease; depends on the liquid |
| Answer» C. Remains unchanged | |
| 843. |
In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger. |
| A. | Once |
| B. | Twice |
| C. | Thrice |
| D. | Four times |
| Answer» C. Thrice | |
| 844. |
Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer. |
| A. | No |
| B. | The least |
| C. | The largest |
| D. | Lower |
| Answer» D. Lower | |
| 845. |
The equation, (NSt x N2/3Pr) = f/2, is the __________ analogy. |
| A. | Colburn |
| B. | Reynolds |
| C. | Prandtl |
| D. | None of these |
| Answer» B. Reynolds | |
| 846. |
The equation, Nst = f/2, is the __________ analogy. |
| A. | Colburn |
| B. | Reynolds |
| C. | Prandtl |
| D. | None of these |
| Answer» C. Prandtl | |
| 847. |
The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by |
| A. | Painting the surface black |
| B. | Painting the surface white (with aluminium paint) |
| C. | Giving the surface a mirror finish |
| D. | Roughening the surface |
| Answer» C. Giving the surface a mirror finish | |
| 848. |
In forced convection, the heat transfer depends on |
| A. | Re, Pr |
| B. | Re, Gr |
| C. | Mainly Gr |
| D. | Re only |
| Answer» B. Re, Gr | |
| 849. |
In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased. |
| A. | Velocity of circulation |
| B. | Liquor-film co-efficient |
| C. | Both A and B |
| D. | Neither A and B |
| Answer» E. | |
| 850. |
Heat transfer rate described by Fourier's law will decrease, if the __________ increases. |
| A. | Thermal conductivity |
| B. | Thickness |
| C. | Temperature difference |
| D. | Heat transfer area |
| Answer» C. Temperature difference | |