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.
| 651. |
The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m². The flux, when the element temperature is increased to 1000°C for the same furnace temperature is |
| A. | 11.2 kW/m² |
| B. | 12.0 kW/m² |
| C. | 14.6 kW/m² |
| D. | 16.5 kW/m² |
| Answer» E. | |
| 652. |
The rate of heat transfer from a vertical plate by natural convection depends upon the temperature differences (ΔT) between wall and outside bulk. The proportionality is given as |
| A. | (ΔT)1/4 |
| B. | (ΔT)1/2 |
| C. | (ΔT)5/4 |
| D. | (ΔT)3/4 |
| Answer» E. | |
| 653. |
The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K= 0.04 W/m.°K and thickness 0.16m is 10 W/m². The temperature of the inside wall is - 5°C. The outside wall temperature is |
| A. | 25°C |
| B. | 30°C |
| C. | 35°C |
| D. | 40°C |
| Answer» D. 40°C | |
| 654. |
In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid |
| A. | Varies directly as the area and the LMTD |
| B. | Directly proportional to LMTD and inversely proportional to the area |
| C. | Varies as square of the area |
| D. | None of these |
| Answer» B. Directly proportional to LMTD and inversely proportional to the area | |
| 655. |
In forced circulation, the heating element is injected |
| A. | Internally |
| B. | Externally |
| C. | Both A and B |
| D. | Neither A nor B |
| Answer» B. Externally | |
| 656. |
If air (a non-condensing gas) is present in a condensing vapor stream, it will __________ the condensation rate of vapor. |
| A. | Increase |
| B. | Decrease |
| C. | Not affect |
| D. | Increase the condensing film co-efficient as well as |
| Answer» C. Not affect | |
| 657. |
For what value of Prandtl number, the Col-burn analogy is valid? |
| A. | 0.06 to 120 |
| B. | 0.6 to 120 |
| C. | 1 to 103 |
| D. | L to 50 |
| Answer» C. 1 to 103 | |
| 658. |
The driving potential for the crystal growth during crystallisation is the __________ of the solution. |
| A. | Concentration |
| B. | Viscosity |
| C. | Super-saturation |
| D. | Density |
| Answer» D. Density | |
| 659. |
The heat transfer co-efficient in film type condensation is __________ that for dropwise condensation. |
| A. | Greater than |
| B. | Lower than |
| C. | Is same as |
| D. | Half |
| Answer» C. Is same as | |
| 660. |
Which of the following has the minimum absorptivity? |
| A. | Aluminium foil |
| B. | Coal dust |
| C. | Refractory bricks |
| D. | Iron plates |
| Answer» B. Coal dust | |
| 661. |
Heat exchanger tubes are never made of |
| A. | Plain carbon steel |
| B. | Stainless steel |
| C. | Lead |
| D. | Copper |
| Answer» D. Copper | |
| 662. |
Use of transverse baffles in a shell and tube heat exchanger is done to increase the |
| A. | Rate of heat transfer |
| B. | Flow velocity |
| C. | Turbulence of shell side fluid |
| D. | All of the above |
| Answer» E. | |
| 663. |
An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of water. The amount of solids handled by the system in kg is |
| A. | 4000 |
| B. | 9000 |
| C. | 4600 |
| D. | 3000 |
| Answer» B. 9000 | |
| 664. |
Air is best heated with steam in a heat exchanger of |
| A. | Plate type |
| B. | Double pipe type with fin on steam side |
| C. | Double pipe type with fin on air side |
| D. | Shell and tube type |
| Answer» D. Shell and tube type | |
| 665. |
In a shell and tube heat exchanger, square pitch compared to triangular pitch |
| A. | Gives a higher shell side pressure drop |
| B. | Gives a lower shell side pressure drop |
| C. | Can pack more surface area into a shell of given diameter |
| D. | None of these |
| Answer» B. Gives a lower shell side pressure drop | |
| 666. |
Grashhoff number is given by |
| A. | gD³.β.Δtρ²/μ² |
| B. | gD2βΔtρ/μ² |
| C. | gD2βΔtP²μ |
| D. | gD³βΔtP²/μ |
| Answer» B. gD2βΔtρ/μ² | |
| 667. |
Graetz number is given by |
| A. | mCp/kL |
| B. | kL/mCp |
| C. | mCp/kμ |
| D. | kμ/mCp |
| Answer» B. kL/mCp | |
| 668. |
What is the steam economy in case of a single effect evaporator system? |
| A. | 1 |
| B. | >1 |
| C. | < 1 |
| D. | 0.1 |
| Answer» D. 0.1 | |
| 669. |
In a shell and tube heat exchanger, floating head is used for |
| A. | Large temperature differentials |
| B. | High heat transfer co-efficient |
| C. | Low pressure drop |
| D. | Less corrosion of tubes |
| Answer» B. High heat transfer co-efficient | |
| 670. |
LMTD for counterflow and prallel flow heat exchanger will be the same, when the |
| A. | Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid) |
| B. | Outlent temperature of both the hot and cold fluid are same |
| C. | Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid |
| D. | None of these |
| Answer» B. Outlent temperature of both the hot and cold fluid are same | |
| 671. |
Steam side heat transfer co-efficient in an evaporator is in the range of __________ kcal/hr.m²°C. |
| A. | 10-50 |
| B. | 100-500 |
| C. | 1000-1500 |
| D. | 5000-15000 |
| Answer» E. | |
| 672. |
In a cooling tower, water becomes cool by |
| A. | Loosing sensible heat |
| B. | Heat transfer to surroundings |
| C. | Vaporisation due to heat loss to air |
| D. | Loosing latent heat |
| Answer» B. Heat transfer to surroundings | |
| 673. |
Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by |
| A. | Eddies current |
| B. | Conduction |
| C. | Convection |
| D. | None of these |
| Answer» C. Convection | |
| 674. |
In pipe flow, heat is transferred from hot wall to the liquid by |
| A. | Conduction only |
| B. | Forced convection only |
| C. | Forced convection and conduction |
| D. | Free and forced convection |
| Answer» D. Free and forced convection | |
| 675. |
In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m².s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m²/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is |
| A. | 2000 |
| B. | 4000 |
| C. | 5000 |
| D. | 6000 |
| Answer» D. 6000 | |
| 676. |
Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer. |
| A. | Grashoff |
| B. | Reynolds |
| C. | Both A & B |
| D. | Prandtl & Grashoff |
| Answer» E. | |
| 677. |
In SI units, fouling factor is expressed in |
| A. | m²°K/W |
| B. | W/m²°K |
| C. | m²°K |
| D. | m°K/W |
| Answer» B. W/m²°K | |
| 678. |
Fouling factor |
| A. | Is a dimensionless quantity |
| B. | Does not provide a safety factor for design |
| C. | Accounts for additional resistances to heat flow |
| D. | None of these |
| Answer» D. None of these | |
| 679. |
Forced circulation evaporators are useful for the concentration of viscous, salting and scale forming liquors. Which of the following is a forced circulation evaporator? |
| A. | Long vertical evaporator |
| B. | Horizontal tube evaporator |
| C. | Agitated film evaporator |
| D. | Calenderia vertical tube evaporator |
| Answer» D. Calenderia vertical tube evaporator | |
| 680. |
Which of the following is the most widely used heat insulating material for pipelines carrying steam? |
| A. | Tar dolomite bricks followed by asbestos |
| B. | Fireclay refractory followed by aluminium sheet |
| C. | Cotton followed by aluminium foil |
| D. | 85% magnesia cement and glass wool |
| Answer» E. | |
| 681. |
Prandtl number for most of dry gases is about |
| A. | 0.001 |
| B. | 0.72 |
| C. | 70 |
| D. | 150 |
| Answer» C. 70 | |
| 682. |
Which of the following is not used as a medium for high temperature heating? |
| A. | Dowtherm |
| B. | Mercury |
| C. | Liquid metal (e.g. molten sodium) |
| D. | Fused salts (e.g., an eutectic mixture of 53% KNO₃, 40% NaNO₂and 7% NaNO₃) |
| Answer» C. Liquid metal (e.g. molten sodium) | |
| 683. |
The sum of reflectivity and absorptivity for an opaque body is equal to |
| A. | 0.5 |
| B. | 1 |
| C. | 0 |
| D. | 2 |
| Answer» C. 0 | |
| 684. |
For an ideal black body |
| A. | Absorptivity = 1 |
| B. | Reflectivity = 1 |
| C. | Emissivity = 0 |
| D. | Transmissivity = 1 |
| Answer» B. Reflectivity = 1 | |
| 685. |
Finned tube heat exchangers |
| A. | Give larger area per tube |
| B. | Use metal fins of low thermal conductivity |
| C. | Facilitate very large temperature drop through tube wall |
| D. | Are used for smaller heat load |
| Answer» B. Use metal fins of low thermal conductivity | |
| 686. |
The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) |
| A. | K/h0 |
| B. | 2K/h0 |
| C. | h0/K |
| D. | h0/2K |
| Answer» C. h0/K | |
| 687. |
The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, ΔT = Temperature drop across condensate film ) |
| A. | (ΔT)2 |
| B. | √ΔT |
| C. | (ΔT)1/4 |
| D. | (ΔT)3/2 |
| Answer» D. (ΔT)3/2 | |
| 688. |
Tube pitch is the __________ of tube diameters and the clearances. |
| A. | Sum |
| B. | Difference |
| C. | Ratio |
| D. | None of these |
| Answer» B. Difference | |
| 689. |
In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell) |
| A. | 0.25 D |
| B. | 0.75 D |
| C. | 0.50 D |
| D. | None of these |
| Answer» C. 0.50 D | |
| 690. |
For heat flow through very thick walled cylinder, use____mean radius. |
| A. | Arithmetic |
| B. | Logarithmic |
| C. | Geometric |
| D. | Either A or C |
| Answer» C. Geometric | |
| 691. |
Crystal size in a continuous crystalliser depends upon the |
| A. | Rate of heat transfer |
| B. | Degree of turbulence |
| C. | Degree of supersaturation |
| D. | All of the above |
| Answer» E. | |
| 692. |
Multiple effect evaporation accounts for |
| A. | Steam economy |
| B. | Lower operating costs |
| C. | Investment economy |
| D. | None of these |
| Answer» B. Lower operating costs | |
| 693. |
The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the |
| A. | Heating volume |
| B. | Heat transfer area |
| C. | Nusselt number |
| D. | None of these |
| Answer» C. Nusselt number | |
| 694. |
Hot water (0.01 m³ /min) enters the tube side of a counter current shell and tube heat exchanger at 80°C and leaves at 50°C. Cold oil (0.05 m³/min) of density 800 kg/m³ and specific heat of 2 kJ/kg.K enters at 20°C. The log mean temperature difference in °C is approximately |
| A. | 32 |
| B. | 37 |
| C. | 45 |
| D. | 50 |
| Answer» B. 37 | |
| 695. |
The main purpose of providing fins on heat transfer surface is to increase the |
| A. | Temperature gradient |
| B. | Mechanical strength of the equipment |
| C. | Heat transfer area |
| D. | Heat transfer co-efficient |
| Answer» D. Heat transfer co-efficient | |
| 696. |
The unit of heat transfer co-efficient in SI unit is |
| A. | J/m²°K |
| B. | W/m²°K |
| C. | W/m°K |
| D. | J/m°K |
| Answer» C. W/m°K | |
| 697. |
All analogy equations connecting friction factor and heat transfer co-efficient apply only to |
| A. | Wall or skin friction |
| B. | Form friction |
| C. | Both A and B |
| D. | Turbulent flow |
| Answer» B. Form friction | |
| 698. |
Steam condensate is recovered by steam traps and recycled for use as boiler feed water, because of its low |
| A. | Hardness |
| B. | Dissolved soilds content |
| C. | Suspended solids content |
| D. | All of the above |
| Answer» E. | |
| 699. |
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively) |
| A. | C/E |
| B. | E/C |
| C. | CE |
| D. | 1/CE |
| Answer» B. E/C | |
| 700. |
In Biot number, the characteristic length used is the ratio of the __________ of the solid. |
| A. | Volume to surface area |
| B. | Perimeter to surface area |
| C. | Surface area to volume |
| D. | Surface area to perimeter |
| Answer» B. Perimeter to surface area | |