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.
| 551. |
Boiling point of a solution according to Duhring's rule is a linear function of the __________ of water. |
| A. | Boiling point (at the same pressure) |
| B. | Viscosity |
| C. | Density |
| D. | Thermal conductivity |
| Answer» B. Viscosity | |
| 552. |
Which is the most suitable for the concentration of foamy & frothy liquors? |
| A. | Agitated film evaporator |
| B. | Long tube vertical evaporator |
| C. | Open pan evaporator |
| D. | None of these |
| Answer» C. Open pan evaporator | |
| 553. |
Reynold's analogy states that (where, St = Stanton number f = friction factor) |
| A. | St = f/2 |
| B. | St = f/4 |
| C. | St = 4f |
| D. | St = f1/2 |
| Answer» B. St = f/4 | |
| 554. |
Crystallisation of solids from a homogeneous solution is a/an __________ process. |
| A. | Exothermic |
| B. | Mildly endothermic |
| C. | Highly endothermic |
| D. | None of these |
| Answer» B. Mildly endothermic | |
| 555. |
Dropwise condensation of steam on cooling surface is promoted |
| A. | An oily surface |
| B. | When both the steam and the tube are clean |
| C. | Only in presence of air |
| D. | None of these |
| Answer» B. When both the steam and the tube are clean | |
| 556. |
A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m².°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be |
| A. | Greater than that for uninsulated steam pipe |
| B. | Less than that of the uninsulated steam pipe |
| C. | Equal to that of the uninsulated steam pipe |
| D. | Less than the steam pipe with 5 cms insulation |
| Answer» C. Equal to that of the uninsulated steam pipe | |
| 557. |
Thermal conductivity of a conducting solid material depends upon its |
| A. | Temperature |
| B. | Porosity |
| C. | Both A & B |
| D. | Neither A nor B |
| Answer» D. Neither A nor B | |
| 558. |
In case of heat flow by conduction for a cylindrical body with an internal heat source, the nature of temperature distribution is |
| A. | Linear |
| B. | Hyperbolic |
| C. | Parabolic |
| D. | None of these |
| Answer» D. None of these | |
| 559. |
__________ equation relates the thermal conductivity of a solid to its temperature. |
| A. | Antonie |
| B. | Kopp's |
| C. | Lee's |
| D. | Kistyakowski |
| Answer» D. Kistyakowski | |
| 560. |
The absorptivity of a body is equal to its emissivity |
| A. | At a particular temperature |
| B. | For circular bodies |
| C. | Under thermal equilibrium |
| D. | None of these |
| Answer» D. None of these | |
| 561. |
Dropwise condensation occurs on __________ surfaces. |
| A. | Clean and dirt free |
| B. | Smooth clean |
| C. | Contaminated cooling |
| D. | Polished |
| Answer» D. Polished | |
| 562. |
Circulation pump is located below the evaporater to |
| A. | Avoid cavitation |
| B. | Avoid frequent priming |
| C. | Create more suction head |
| D. | None of these |
| Answer» D. None of these | |
| 563. |
The number of kg vaporised per kg of steam fed to the evaporator is defined as |
| A. | Capacity |
| B. | Rate of evaporation |
| C. | Economy |
| D. | Rate of vaporisation |
| Answer» D. Rate of vaporisation | |
| 564. |
A body cools down from 75°C to 70°C in 10 minutes. It will cool down from 70° C to 65° C in __________ minutes. |
| A. | 10 |
| B. | >10 |
| C. | <10 |
| D. | Either B or C, depends on the mass of the body |
| Answer» C. <10 | |
| 565. |
If the baffle spacing in a shell and tube heat exchanger increases, then the Reynolds number of the shell side fluid |
| A. | Remains unchanged |
| B. | Increases |
| C. | Increases or decreases depending on number of shell passes |
| D. | Decreases |
| Answer» E. | |
| 566. |
Black liquor generated during paper manufacture is concentrated in a |
| A. | Single effect evaporator |
| B. | Single effect evaporator followed by a crystalliser |
| C. | Multiple effect evaporator |
| D. | Multiple effect evaporators followed by a crystalliser |
| Answer» D. Multiple effect evaporators followed by a crystalliser | |
| 567. |
Nucleate boiling is promoted |
| A. | On polished surfaces |
| B. | On rough surfaces |
| C. | In the absence of agitation |
| D. | None of these |
| Answer» C. In the absence of agitation | |
| 568. |
A measure of the extent to which viscous heating is important relative to the heat flow resulting from the impressed temperature difference is represented by the __________ number. |
| A. | Condensation |
| B. | Grashoff |
| C. | Stantan |
| D. | Brinkman |
| Answer» E. | |
| 569. |
Which is the most suitable for the con-certration of highly concentrated solution? |
| A. | Open pan evaporation |
| B. | Long tube vertical evaporator |
| C. | Agitated film evaporator |
| D. | None of these |
| Answer» B. Long tube vertical evaporator | |
| 570. |
When vaporisation takes place directly at the heating surface, it is called |
| A. | Film boiling |
| B. | Nucleate boiling |
| C. | Vapour binding |
| D. | None of these |
| Answer» C. Vapour binding | |
| 571. |
At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the |
| A. | Buffer zone |
| B. | Turbulent core |
| C. | Both A and B |
| D. | Viscous sub-layer |
| Answer» E. | |
| 572. |
If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length |
| A. | Ha = hl |
| B. | Ha = 2hl |
| C. | Ha = 0.5 hl |
| D. | Ha = 0.75 hl |
| Answer» C. Ha = 0.5 hl | |
| 573. |
The unit of heat transfer co-efficient is |
| A. | BTU/hr. ft²°F |
| B. | BTU/hr. °F. ft |
| C. | BTU/hr. °F |
| D. | BTU/hr. ft |
| Answer» B. BTU/hr. °F. ft | |
| 574. |
Indirect contact heat exchangers are preferred over direct contact heat exchangers, because |
| A. | Heat transfer co-efficient are high |
| B. | There is no risk of contamination |
| C. | There is no mist formation |
| D. | Cost of equipment is lower |
| Answer» C. There is no mist formation | |
| 575. |
In a shell and tube heat exchanger, the shell side fluid velocity can not be changed by changing the |
| A. | Tube layout |
| B. | Tube diameter |
| C. | Tube pitch |
| D. | No. of baffles |
| Answer» C. Tube pitch | |
| 576. |
In case of evaporators, liquid entrainment results primarily due to |
| A. | High vacuum in the evaporator |
| B. | High evaporation rate |
| C. | Foaming of the solution |
| D. | High heat transfer rate |
| Answer» D. High heat transfer rate | |
| 577. |
__________ paint has the minimum absorption co-efficient. |
| A. | Black |
| B. | White lead |
| C. | Grey |
| D. | Light cream |
| Answer» C. Grey | |
| 578. |
For __________ Prandtl number values, the heat conduction will be negligible in the buffer zone. |
| A. | Extremely low |
| B. | Low |
| C. | High |
| D. | No |
| Answer» D. No | |
| 579. |
Grashoff number, which is defined as g . β(Ts - T∞) ρ². L³/μ², is proportional to the ratio of buoyancy force to __________ force. |
| A. | Viscous |
| B. | Elastic |
| C. | Inertial |
| D. | None of these |
| Answer» B. Elastic | |
| 580. |
If Prandtl number is greater than the Schmidt number, then the |
| A. | Thermal boundary layer lies inside the concentration boundary layer |
| B. | Concentration boundary layer lies inside the thermal boundary layer |
| C. | Thermal & concentration boundary layers are of equal thickness |
| D. | Hydrodynamic(i.e., momentum)boundary layer is thicker than the other two |
| Answer» B. Concentration boundary layer lies inside the thermal boundary layer | |
| 581. |
In the equation Q = UAΔt; Δt is |
| A. | Geometric mean temperature difference |
| B. | Arithmetic mean temperature difference |
| C. | Logarithmic mean temperature difference |
| D. | The difference of average bulk temperatures of hot and cold fluids |
| Answer» D. The difference of average bulk temperatures of hot and cold fluids | |
| 582. |
Reason for operating an evaporator in multiple effect is to secure |
| A. | Increased steam economy |
| B. | Decreased steam consumption |
| C. | Both A and B |
| D. | Increased capacity |
| Answer» D. Increased capacity | |
| 583. |
Mechanical recompression evaporation is used in the production of |
| A. | Alcohol |
| B. | Distilled water |
| C. | Salt |
| D. | Fruits jam |
| Answer» C. Salt | |
| 584. |
Kg of liquid evaporated per hour in an evaporator is defined as its |
| A. | Capacity |
| B. | Economy |
| C. | Steam load |
| D. | None of these |
| Answer» B. Economy | |
| 585. |
The actual temperature drop across the heating surface in an evaporator depends on the |
| A. | Feed |
| B. | Depth of liquid over heating surface |
| C. | Pressure difference between steam chest and vapour space |
| D. | All of the above |
| Answer» E. | |
| 586. |
Choose the most important factor on which the heat conducted through a wall in a unit time will depend on? |
| A. | Thickness of the wall |
| B. | Area of the wall perpendicular to heat flow |
| C. | Material of the wall |
| D. | Temperature difference between the two surfaces of the wall |
| Answer» E. | |
| 587. |
The capacity of double-effect evaporator is less than half of the capacity of two single effects, each of which is operating over same terminal temperature difference, when the |
| A. | Solution has an elevation of boiling point |
| B. | Evaporators operate under vacuum |
| C. | Evaporators opreate at atmospheric pressure |
| D. | None of these |
| Answer» B. Evaporators operate under vacuum | |
| 588. |
Which of the following has the minimum thermal conductivity? |
| A. | Nitrogen |
| B. | Steel |
| C. | Carbon black |
| D. | Tar |
| Answer» B. Steel | |
| 589. |
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a long tube |
| A. | Exit-fluid temperature > wall temperature |
| B. | Exit fluid temperature < wall temperature |
| C. | Exit fluid temperature = wall temperature |
| D. | Graetz number > 100 |
| Answer» D. Graetz number > 100 | |
| 590. |
For specified tube outside diameter, higher BWG means higher |
| A. | Tube thickness |
| B. | Cross-sectional area |
| C. | Weight per unit length |
| D. | None of these |
| Answer» C. Weight per unit length | |
| 591. |
Which of the following has maximum thermal conductivity? |
| A. | Iron |
| B. | Coal |
| C. | Nitrogen |
| D. | Tar |
| Answer» B. Coal | |
| 592. |
In an extended surface heat exchanger, fluid having lower co-efficient |
| A. | Flows through the tube |
| B. | Flows outside the tubes |
| C. | Can flow either inside or outside the tubes |
| D. | Should not be used as it gives very high pressure drop |
| Answer» C. Can flow either inside or outside the tubes | |
| 593. |
In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is |
| A. | Minimum |
| B. | Maximum |
| C. | Zero |
| D. | Infinity |
| Answer» D. Infinity | |
| 594. |
Heat transfer occurs by natural convection because change in temperature causes difference in |
| A. | Viscosity |
| B. | Density |
| C. | Thermal conductivity |
| D. | Heat capacity |
| Answer» C. Thermal conductivity | |
| 595. |
In case of a supercooled solution, which is on the verge of crystallisation, the free energy of the solution as compared to that of the solid is |
| A. | More |
| B. | Less |
| C. | Same |
| D. | More or less; depends on the nature of solution |
| Answer» B. Less | |
| 596. |
Fresh orange juice contains 12% (by weight) solids and the rest water 90% of the fresh juice is sent to an evaporator to remove water and subsequently mixed with the remaining 10% of fresh juice. The resultant product contains 40% solids. The kg of water removed from 1 kg fresh juice is |
| A. | 0.4 |
| B. | 0.5 |
| C. | 0.6 |
| D. | 0.7 |
| Answer» E. | |
| 597. |
A long iron rod initially at a temperature of 20°C has one end dipped in boiling water (100°C) at time, t = 0. The curved surface of the rod is insulated so that heat conduction is one dimensional in the axial direction. The temperature at a distance 100 mm from the dipped end becomes 40°C at time, t = 200 s. The same temperature is achieved at a distance of 200 mm from the dipped end at time |
| A. | t = 283 s |
| B. | t = 356 s |
| C. | t = 400 s |
| D. | t = 800 s |
| Answer» E. | |
| 598. |
The Stefan-Boltzman constant depends on the |
| A. | Medium |
| B. | Temperature |
| C. | Surface |
| D. | None of these |
| Answer» E. | |
| 599. |
The value of Stefan-Boltazman constant in SI unit is |
| A. | 5.6697 x 10-8W/m².°K4 |
| B. | 0.1714 x 10-8W/m².°K4 |
| C. | 5.6697 x 10-8kcal/m² . °K4 |
| D. | 0.1714 x 10-8kcal/m². °K4 |
| Answer» B. 0.1714 x 10-8W/m².°K4 | |
| 600. |
Rate of heat transfer by vaporisation from pools of water is affected by the |
| A. | Nature of heating surface and distribution of bubbles |
| B. | Surface tension of water |
| C. | Viscosity of water |
| D. | All of the above |
| Answer» E. | |