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.
| 501. |
A sphere of radius 'R₁' is enclosed in a sphere of radius 'R₂'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is |
| A. | 0 |
| B. | R₂/(R₁+R₂) |
| C. | 1 |
| D. | (R₁/R₂)2 |
| Answer» C. 1 | |
| 502. |
The units of resistance to heat transfer is |
| A. | J.m⁻².K⁻¹ |
| B. | J.m⁻¹.K⁻¹ |
| C. | W.m⁻².K⁻¹ |
| D. | W⁻¹m²K |
| Answer» E. | |
| 503. |
For a perfectly transparent surface (like gases), the |
| A. | Absorptivity = 0 |
| B. | Transmissivity = 1 |
| C. | Reflectivity = 0 |
| D. | All of the above |
| Answer» C. Reflectivity = 0 | |
| 504. |
In case of a vertical tube evaporator, with increase in the liquor level, the |
| A. | Capacity of the evaporator is decreased |
| B. | Capacity of the evaporator is increased |
| C. | True temperature drop increases |
| D. | Both B and C |
| Answer» B. Capacity of the evaporator is increased | |
| 505. |
For a liquid in laminar flow through a very long tube, when the exit fluid temperature approaches the wall temperature, the equation to be used is |
| A. | Nu = 0.023 Re0.8 . Pr0.4 |
| B. | Nu = Gz |
| C. | Nu = Gz |
| D. | Nu = 2Gz0.5 |
| Answer» D. Nu = 2Gz0.5 | |
| 506. |
With the increase of temperature, the Col-burn jH factor |
| A. | Increases |
| B. | Decreases |
| C. | Remains unchanged |
| D. | May increase or decrease ; depending on temperature |
| Answer» B. Decreases | |
| 507. |
Double pipe heat exchangers are preferably useful, when |
| A. | High viscosity liquid is to be cooled |
| B. | Requirement of heat transfer area is low |
| C. | Overall heat transfer co-efficient is very high |
| D. | A corrosive liquid is to be heated |
| Answer» C. Overall heat transfer co-efficient is very high | |
| 508. |
Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the |
| A. | Surrounding temperature |
| B. | Average temperature of the fin |
| C. | Temperature of the fin end |
| D. | Constant temperature equal to that of the base |
| Answer» E. | |
| 509. |
(Cp . μ)/K is termed as the __________ number. |
| A. | Grashoff |
| B. | Nusselt |
| C. | Prandtl |
| D. | Stanton |
| Answer» D. Stanton | |
| 510. |
Thermal diffusivity of a material |
| A. | Has the unit m² /sec |
| B. | Is defined as K/ρ . Cp |
| C. | Is the ratio of thermal conductivity to thermal capacity |
| D. | All of the above |
| Answer» E. | |
| 511. |
Nusselt number is the ratio of the temperature gradient at the wall to |
| A. | Temperature difference |
| B. | Heat flux |
| C. | That across the entire pipe |
| D. | None of these |
| Answer» D. None of these | |
| 512. |
If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ law. |
| A. | Hyperbolic |
| B. | Parabolic |
| C. | Linear |
| D. | Logarithmic |
| Answer» D. Logarithmic | |
| 513. |
A multiple effect evaporator as compared to a single effect evaporator of the same capacity has |
| A. | Lower heat transfer area |
| B. | Lower steam economy |
| C. | Higher steam economy |
| D. | Higher solute concentration in the product |
| Answer» D. Higher solute concentration in the product | |
| 514. |
Radiation heat transfer rates does not depend upon the |
| A. | Type of absorbing surface |
| B. | Distance between the heat source and the object receiving the heat |
| C. | Surface area and temperature of the heat source |
| D. | None of these |
| Answer» E. | |
| 515. |
Heat flux is the time rate of heat transfer per unit |
| A. | Length |
| B. | Area |
| C. | Volume |
| D. | None of these |
| Answer» C. Volume | |
| 516. |
In an interphase heat transfer process, the equilibrium state corresponds to equality of temperature in the two phases, while the condition for equilibrium in an interphase mass transfer process is equality of |
| A. | Concentrations |
| B. | Chemical potentials |
| C. | Activity co-efficients |
| D. | Mass transfer co-efficients |
| Answer» B. Chemical potentials | |
| 517. |
Heat transfer rate per unit area is called |
| A. | Thermal conductivity |
| B. | Heat flux |
| C. | Heat transfer co-efficient |
| D. | Thermal diffusivity |
| Answer» C. Heat transfer co-efficient | |
| 518. |
Analogy between mass and heat transfer is not applicable in case of |
| A. | Same velocity profile or equal eddy diffusivities |
| B. | Thermal or pressure mass diffusion |
| C. | Viscous heating or chemical reaction |
| D. | Both B and C |
| Answer» E. | |
| 519. |
During crystallisation, formation of crystal can occur in __________ solution only. |
| A. | Saturated |
| B. | Supersaturated |
| C. | Undersaturated |
| D. | All of the above |
| Answer» C. Undersaturated | |
| 520. |
A __________ evaporator employs an annular downtake. |
| A. | Basket type |
| B. | Horizontal |
| C. | Long tube vertical |
| D. | None of these |
| Answer» B. Horizontal | |
| 521. |
Forced circulation evaporators are normally used for concentrating liquids having |
| A. | Scaling characteristics |
| B. | High viscosity |
| C. | Both A & B |
| D. | Neither A nor B |
| Answer» D. Neither A nor B | |
| 522. |
The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m².K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m².K. The overall heat transfer co-efficient at this time is |
| A. | 1200W/m².K |
| B. | 894W/m².K |
| C. | 333W/m².K |
| D. | 287 W/m².K |
| Answer» D. 287 W/m².K | |
| 523. |
Water is normally used as a coolant in the heat exchange equipments mainly because ofits |
| A. | Abundance & high heat capacity |
| B. | Low density |
| C. | Low viscosity |
| D. | High fluidity |
| Answer» B. Low density | |
| 524. |
Prandtl number is the ratio of |
| A. | Momentum diffusivity to mass diffusivity |
| B. | Momentum diffusivity to thermal diffusivity |
| C. | Thermal diffusivity to mass diffusivity |
| D. | Thermal diffusivity to momentum diffusivity |
| Answer» C. Thermal diffusivity to mass diffusivity | |
| 525. |
Mode of heat transfer involved in the cooling of air cooled internal combustion engine is |
| A. | Conduction |
| B. | Natural convection |
| C. | Forced convection |
| D. | None of these |
| Answer» C. Forced convection | |
| 526. |
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) |
| A. | D/5 and D |
| B. | D/2 and 2 D |
| C. | D/4 and 2 D |
| D. | D and 2 D |
| Answer» B. D/2 and 2 D | |
| 527. |
Tube expansion allowances exist in __________ heat exchanger. |
| A. | Multipass fixed tube sheet |
| B. | U-tube |
| C. | Single pass fixed tube sheet |
| D. | None of these |
| Answer» C. Single pass fixed tube sheet | |
| 528. |
Thermal diffusivity is the most important in heat transfer by |
| A. | Conduction |
| B. | Radiation |
| C. | Condensation |
| D. | Natural convection |
| Answer» B. Radiation | |
| 529. |
View factor is important in heat transfer by |
| A. | Steady state conduction |
| B. | Natural convection |
| C. | Forced convection |
| D. | Radiation |
| Answer» E. | |
| 530. |
Kirchoff s law applies to __________ radiation. |
| A. | Total |
| B. | Monochromatic |
| C. | Both A & B |
| D. | Neither A nor B |
| Answer» D. Neither A nor B | |
| 531. |
Pick out the correct equation. |
| A. | JH = (St)(Pr)2/3 = f/2 |
| B. | JH = (St)(Pr)1/3 = f/2 |
| C. | JH = (St)2/3(Pr) = f/2 |
| D. | JH = (St)1/3(Pr) = f/2 |
| Answer» B. JH = (St)(Pr)1/3 = f/2 | |
| 532. |
Peclet number (Pe) is given by |
| A. | Pe = Re.Pr |
| B. | Pe = Re/Pr |
| C. | Pe = Pr/Re |
| D. | Pe = Nu.Re |
| Answer» B. Pe = Re/Pr | |
| 533. |
At what value of Prandtl number, the hydrodynamic and thermal boundary layers are identical? |
| A. | 0.5 |
| B. | 1 |
| C. | 1.5 |
| D. | 80 |
| Answer» C. 1.5 | |
| 534. |
Maximum water velocity in tubes of a 1-2 shell and tube heat exchanger may be around __________ metres/second. |
| A. | 1 |
| B. | 10 |
| C. | 20 |
| D. | 30 |
| Answer» B. 10 | |
| 535. |
Fourier's law applies to the heat transfer by |
| A. | Convection |
| B. | Radiation |
| C. | Conduction |
| D. | All of the above |
| Answer» D. All of the above | |
| 536. |
Fourier's law of heat conduction applies to __________ surfaces. |
| A. | Isothermal |
| B. | Non-isothermal |
| C. | Both A and B |
| D. | Neither A and B |
| Answer» D. Neither A and B | |
| 537. |
Duhring rule is important in solving problems on |
| A. | Distillation |
| B. | Crystallisation |
| C. | Evaporation |
| D. | Humidification |
| Answer» D. Humidification | |
| 538. |
Which of the following is unimportant in forced convection? |
| A. | Reynolds number |
| B. | Prandtl number |
| C. | Grashhoff number |
| D. | None of these |
| Answer» D. None of these | |
| 539. |
The purpose of providing bleed points in the evaporator is to |
| A. | Admit the feed |
| B. | Remove the product |
| C. | Facilitate removal of non-condensable gases |
| D. | Create vacuum |
| Answer» D. Create vacuum | |
| 540. |
A hot body will radiate heat most rapidly, if its surface is |
| A. | White & rough |
| B. | Black & rough |
| C. | White & polished |
| D. | Black & polished |
| Answer» C. White & polished | |
| 541. |
Removal of __________ heat is involved in the condensation of a vapor under saturated conditions. |
| A. | Super |
| B. | Sensible |
| C. | Latent |
| D. | Both B & C |
| Answer» C. Latent | |
| 542. |
A concentric double pipe heat exchanger as compared to the shell and tube heat exchanger for the same heat load requires |
| A. | Less heating surface |
| B. | More space |
| C. | Lower maintenance cost |
| D. | None of these |
| Answer» C. Lower maintenance cost | |
| 543. |
A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m³ and 0.4 kJ/kg.K respectively. The heat transfer co-efficient is 50 W/m².K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is |
| A. | 555 |
| B. | 55.5 |
| C. | 0.55 |
| D. | 0.15 |
| Answer» E. | |
| 544. |
A dilute aqueous solution is to be concentrated in an evaporator system. High pressure steam is available. Multiple effect evaporator system is employed, because |
| A. | Total heat transfer area of all the effects is -less than that in a single effect evaporator system |
| B. | Total amount of vapor produced per Kg of feed steam in a multiple effect system is much higher than in a single effect |
| C. | Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system |
| D. | Heat transfer co-efficient in a single effect is much lower than that in any effect in a multieffect system |
| Answer» C. Boiling point elevation in a single effect system is much higher than that in any effect in a multieffect system | |
| 545. |
The purpose of providing a 'catchall' in the vapor line of an evaporator is to |
| A. | Create vacuum |
| B. | Regulate the vapor flow |
| C. | Vent the non-condensible gases |
| D. | Arrest the entrained liquid |
| Answer» E. | |
| 546. |
For concentrating an aqueous solution of a material like anhydrous Na₂SO₄, whose solubility decreases with rise in temperature, the most suitable evaporator is a __________ evaporator. |
| A. | High pressure |
| B. | Vacuum |
| C. | Backward feed |
| D. | None of these |
| Answer» C. Backward feed | |
| 547. |
__________ heat exchanger is used for chilling oil to be dewaxed. |
| A. | U-tube |
| B. | Double pipe |
| C. | Fixed tube |
| D. | Floating head |
| Answer» C. Fixed tube | |
| 548. |
Which area is used in case of heat flow by conduction through a cylinder? |
| A. | Logarithmic mean area |
| B. | Arithmetic mean area |
| C. | Geometric mean area |
| D. | None of these |
| Answer» B. Arithmetic mean area | |
| 549. |
In Fourier's law, the proportionality constant is called the |
| A. | Heat transfer co-efficient |
| B. | Thermal diffusivity |
| C. | Thermal conductivity |
| D. | Stefan-Boltzman constant |
| Answer» D. Stefan-Boltzman constant | |
| 550. |
Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is |
| A. | Thin walled having the value of Ao Ai/< 2 |
| B. | Thick walled |
| C. | Having the value of Ao/Ai > 2 |
| D. | Both B and C |
| Answer» B. Thick walled | |