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.
| 601. |
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe? |
| A. | 0.5 |
| B. | < 0.5 |
| C. | > 0.6 |
| D. | < 0.1 |
| Answer» D. < 0.1 | |
| 602. |
Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. |
| A. | Laminar |
| B. | Transition |
| C. | Both A & B |
| D. | Highly turbulent |
| Answer» E. | |
| 603. |
In counter flow compared to parallel flow, |
| A. | LMTD is greater |
| B. | Less surface area is required for a given heat transfer rate |
| C. | Both A and B |
| D. | More surface area is required for a given heat transfer rate |
| Answer» D. More surface area is required for a given heat transfer rate | |
| 604. |
In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always |
| A. | < 1 |
| B. | > 1 |
| C. | 1 |
| D. | ∞ |
| Answer» B. > 1 | |
| 605. |
Boiling point elevation of a solution of NaOH |
| A. | Increases rapidly with temperature rise |
| B. | Is almost independent of temperature |
| C. | Is almost independent of pressure |
| D. | Both B and C |
| Answer» E. | |
| 606. |
The Fourier number (defined as a.t/L²) is used in the analysis of problem involving heat transfer by |
| A. | Forced convection |
| B. | Natural convection |
| C. | Transient conduction |
| D. | Steady state conduction |
| Answer» D. Steady state conduction | |
| 607. |
Low thermal conductivity of heat insulating materials is due to its |
| A. | Dense structure |
| B. | High proportion of air space |
| C. | High specific heat |
| D. | None of these |
| Answer» C. High specific heat | |
| 608. |
A process stream of dilute aqueous solution flowing at the rate of10 Kg.s⁻¹ is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s⁻¹. A 1 - 1 shell and tube heat exchanger is available. The best arrangement is |
| A. | Counter flow with process stream on shell side |
| B. | Counter flow with process stream on tube side |
| C. | Parallel flow with process stream on shell side |
| D. | Parallel flow with process stream on tube side |
| Answer» B. Counter flow with process stream on tube side | |
| 609. |
1 BTU/hr.ft.°F is equal to __________ kcal/hr. m.°C. |
| A. | 1.49 |
| B. | 1 |
| C. | 4.88 |
| D. | None of these |
| Answer» B. 1 | |
| 610. |
Value of Prandtl number for water ranges from |
| A. | L to 2 |
| B. | 5 to 10 |
| C. | 100 to 500 |
| D. | 1000 to 2000 |
| Answer» C. 100 to 500 | |
| 611. |
Which of the following has the lowest overall heat transfer co-efficient? |
| A. | Dowtherm |
| B. | Molten sodium |
| C. | Water |
| D. | Air |
| Answer» E. | |
| 612. |
With increase in temperature, the thermal conductivity of most liquids |
| A. | Increases |
| B. | Decreases |
| C. | Remains same |
| D. | First increases upto a certain temperature and then becomes constant |
| Answer» C. Remains same | |
| 613. |
In SI units, thermal conductivity is expressed in |
| A. | Watt/m.°K |
| B. | Watt/m². °K |
| C. | Watt/m². °K |
| D. | Watt/m4. °K |
| Answer» B. Watt/m². °K | |
| 614. |
In a gas-liquid shell and tube heat exchanger, the |
| A. | Presence of a non-condensible gas decreases the condensing film co-efficient |
| B. | Gases under high pressure are routed through the tube side, because high pressure gases are corrosive in nature |
| C. | Gases to be heated/cooled is normally routed through the shell side, because the corrosion caused by the cooling water or steam condensate remain localised to the tubes |
| D. | All of the above |
| Answer» E. | |
| 615. |
'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a |
| A. | Non-dimensional factor |
| B. | Factor of safety |
| C. | Conversion factor for individual film heat transfer co-efficient to overall heat transfer co-efficient |
| D. | None of these |
| Answer» C. Conversion factor for individual film heat transfer co-efficient to overall heat transfer co-efficient | |
| 616. |
The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness) |
| A. | ∝ t |
| B. | ∝ 1/t |
| C. | ∝ √t |
| D. | Independent of 't' |
| Answer» C. ∝ √t | |
| 617. |
Kirchoff's law is applicable to |
| A. | Monochromatic radiation only |
| B. | Total radiation only |
| C. | Both A and B |
| D. | Only volumes and not to surfaces |
| Answer» D. Only volumes and not to surfaces | |
| 618. |
Steam economy in case of a triple effect evaporator will be |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | Between 0 and 1 |
| Answer» D. Between 0 and 1 | |
| 619. |
Multipass heat exchangers are used |
| A. | Because of simplicity of fabrication |
| B. | For low heat load |
| C. | To obtain higher heat transfer co-efficient and shorter tube |
| D. | To reduce the pressure drop |
| Answer» D. To reduce the pressure drop | |
| 620. |
With increase in temperature, the thermal conductivity of fresh lubricating oil |
| A. | Increases |
| B. | Decreases |
| C. | Remains unchanged |
| D. | May increase or decrease; depends on its composition |
| Answer» C. Remains unchanged | |
| 621. |
As per Kirchoffs law, the ratio of the total radiating power to the absorptivity of a body depends on the |
| A. | Temperature of the body only |
| B. | Wavelength of monochromatic radiation |
| C. | Both A and B |
| D. | Nature of material of body |
| Answer» B. Wavelength of monochromatic radiation | |
| 622. |
Which of the following has maximum thermal conductivity at the same temperature? |
| A. | Steel |
| B. | Petrol |
| C. | Air |
| D. | All of the above |
| Answer» B. Petrol | |
| 623. |
A __________ surface has the maximum thermal emissivity out of the following. |
| A. | Black & smooth |
| B. | Black & rough |
| C. | White & smooth |
| D. | White & rough |
| Answer» C. White & smooth | |
| 624. |
The Grashoff number is defined as the ratio of the |
| A. | Buoyancy to inertial forces |
| B. | Buoyancy to viscous forces |
| C. | Inertial to viscous forces |
| D. | Buoyancy to surface tension forces |
| Answer» C. Inertial to viscous forces | |
| 625. |
A black body when hot, emits heat radiation of __________ wavelengths. |
| A. | Small |
| B. | Large |
| C. | All |
| D. | One fixed |
| Answer» D. One fixed | |
| 626. |
Heat transfer by natural convection is enhanced in system with |
| A. | High viscosity |
| B. | High co-efficient of thermal expansion |
| C. | Low temperature gradients |
| D. | Low density change with temperature |
| Answer» C. Low temperature gradients | |
| 627. |
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient |
| A. | Continues to increase |
| B. | Continues to decrease |
| C. | Goes through a minimum |
| D. | Goes through a maximum |
| Answer» D. Goes through a maximum | |
| 628. |
Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity? |
| A. | Aluminium foil |
| B. | Refractory bricks |
| C. | Iron plate |
| D. | Coke breeze |
| Answer» E. | |
| 629. |
Presence of a non-condensing gas in a condensing vapour |
| A. | Increases the rate of condensation |
| B. | Decreases thermal resistance |
| C. | Is desirable to increase the film co-efficient |
| D. | None of these |
| Answer» E. | |
| 630. |
If h₁ = inner film co-efficient and /h₂ = outer film co-efficient, then the overall heat transfer co-efficient is |
| A. | Always less than h₁ |
| B. | Always between h₁ and h₂ |
| C. | Always higher than h₂ |
| D. | Dependent on metal resistance |
| Answer» C. Always higher than h₂ | |
| 631. |
For a laminar flow of fluid in a circular tube, 'h₁' is the convective heat transfer co-efficient at velocity 'V₁'. If the velocity is reduced by half and assuming the fluid properties are constant, the new convective heat transfer co-efficient is |
| A. | 1.26 h₁ |
| B. | 0.794 h₁ |
| C. | 0.574 h₁ |
| D. | 1.741 h₁ |
| Answer» C. 0.574 h₁ | |
| 632. |
Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heat flux vs. temperature drop for a boiling liquid, because |
| A. | Convection becomes important |
| B. | Conduction becomes important |
| C. | Radiation becomes important |
| D. | Sub-cooled boiling occurs |
| Answer» D. Sub-cooled boiling occurs | |
| 633. |
Multiple effect evaporators ar used to |
| A. | Increase the steam economy & decrease the capacity |
| B. | Increase the steam economy & the capacity |
| C. | Decrease the steam economy & the capacity |
| D. | Decrease the steam economy & increase the capacity |
| Answer» C. Decrease the steam economy & the capacity | |
| 634. |
In sub-cooled boiling, |
| A. | Temperature of the heating surface is less than the boiling point of the liquid |
| B. | Temperature of the heating surface is more than the boiling point of the liquid |
| C. | Bubbles from heating surface are absorbed by the mass of the liquid |
| D. | Very large vapour space is necessary |
| Answer» C. Bubbles from heating surface are absorbed by the mass of the liquid | |
| 635. |
Steam traps are provided in steam carrying pipelines to |
| A. | Condense steam |
| B. | Release excess steam pressure by bleeding steam |
| C. | Remove condensate and inert gases |
| D. | None of these |
| Answer» D. None of these | |
| 636. |
Steady state one dimensional heat flow by conduction as given by Fourier's low does not assume that |
| A. | There is no internal heat generation |
| B. | Boundary surfaces are isothermal |
| C. | Material is anisotropic |
| D. | Constant temperature gradient exists |
| Answer» D. Constant temperature gradient exists | |
| 637. |
In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface. |
| A. | Nucleate |
| B. | Local |
| C. | Pool |
| D. | Saturated |
| Answer» C. Pool | |
| 638. |
The critical radius of insulation for cylindrical pipe is (where, hi = heat transfer coefficient at inside of the pipe ) |
| A. | K/h0 |
| B. | 2K/h0 |
| C. | hi/K |
| D. | 2hi/K |
| Answer» B. 2K/h0 | |
| 639. |
Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.) |
| A. | √d |
| B. | d |
| C. | d2 |
| D. | d1.5 |
| Answer» D. d1.5 | |
| 640. |
Overall heat transfer co-efficient for cooling of hydrocarbons by water is about |
| A. | 50 -100 Kcal/hr.m².°C |
| B. | 50 -100 W/m² . °K |
| C. | 50 -100 BTU/hr. ft.2°F |
| D. | 1000 - 1500 BTU/hr. ft.2°F |
| Answer» D. 1000 - 1500 BTU/hr. ft.2°F | |
| 641. |
Which of the following has the highest thermal conductivity? |
| A. | Brick |
| B. | Air |
| C. | Water |
| D. | Silver |
| Answer» E. | |
| 642. |
__________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side. |
| A. | Single pass, fixed tube sheet |
| B. | U-tube |
| C. | Three pass, fixed tube sheet |
| D. | None of these |
| Answer» C. Three pass, fixed tube sheet | |
| 643. |
For small temperature difference, the heat transfer rate as per Newton's law of cooling is proportional to (where, Δt = excess temperature) |
| A. | Δt |
| B. | Δt² |
| C. | Δt³ |
| D. | √Δt |
| Answer» B. Δt² | |
| 644. |
The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature) |
| A. | (ΔT)² |
| B. | (ΔT)⁴ |
| C. | (ΔT)³ |
| D. | √(ΔT) |
| Answer» D. √(ΔT) | |
| 645. |
Which characteristic of a fluid is not important in deciding its route in a shell and tube heat exchanger? |
| A. | Corrosiveness |
| B. | Fouling characteristic |
| C. | Viscosity |
| D. | None of these |
| Answer» E. | |
| 646. |
Which of the following parameters is increased by use of finned tube in a multipass shell and tube heat exchanger? |
| A. | Tube side pressure drop and the heat transfer rate |
| B. | Convective heat transfer co-efficient |
| C. | Effective tube surface area for convective heat transfer |
| D. | All of the above |
| Answer» E. | |
| 647. |
Heat waves |
| A. | Can not pass through vacuum |
| B. | Travel in straight line |
| C. | Can be reflected by a mirror |
| D. | Both B and C |
| Answer» E. | |
| 648. |
Extremely large or small volumes of fluids are generally best routed through the shell side of a shell and tube heat exchanger, because of the |
| A. | Less corrosion problems |
| B. | Flexibility possible in the baffle arrangement |
| C. | Low pressure drop |
| D. | High heat transfer co-efficient |
| Answer» C. Low pressure drop | |
| 649. |
The purpose of floating head in a heat exchanger is to |
| A. | Avoid buckling of tubes |
| B. | Provide support for tubes |
| C. | Decrease the pressure drop |
| D. | Facilitate its lengthening, if needed |
| Answer» B. Provide support for tubes | |
| 650. |
Radiation energy is emitted by all the substances, which are above |
| A. | 0°K |
| B. | 0°C |
| C. | 100°C |
| D. | Room temperature |
| Answer» B. 0°C | |