MCQOPTIONS
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MCQOPTIONS
This section includes 640 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 501. |
In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)$ |
| A. | α = 1; ε ≠ 1 |
| B. | α ≠ 1, ε = 1 |
| C. | α ≠ 1, ε ≠ 1 |
| D. | α = 1; ε = 1 |
| Answer» E. | |
| 502. |
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. | |
| 503. |
In natural convection heat transfer, the correlating parameter is the |
| A. | Graetz number |
| B. | Eckert number |
| C. | Grashoff number |
| D. | Bond number |
| Answer» D. Bond number | |
| 504. |
In which mode of heat transfer, the Biot number is important ? |
| A. | Transient heat conduction |
| B. | Natural convection |
| C. | Forced convection |
| D. | Radiation |
| Answer» B. Natural convection | |
| 505. |
With increase in porosity, the thermal conductivity of a solid substance |
| A. | increases |
| B. | decreases |
| C. | remains unchanged |
| D. | may increase or decrease; depends on the solid |
| Answer» C. remains unchanged | |
| 506. |
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 | |
| 507. |
In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be$ |
| A. | less than 45°C |
| B. | more than 45°C |
| C. | equal to 45°C |
| D. | initially decreases and remains constant thereafter. |
| Answer» C. equal to 45¬∞C | |
| 508. |
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. | |
| 509. |
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. | |
| 510. |
Fruit juice (a heat sensitive material) can be concentrated in a __________ evaporator. |
| A. | long tube |
| B. | falling film |
| C. | high pressure |
| D. | none of these |
| Answer» C. high pressure | |
| 511. |
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 | |
| 512. |
Economy of a multiple effect evaporator is not influenced much by the |
| A. | boiling point elevations |
| B. | temperature of the feed |
| C. | rate of heat transfer |
| D. | ratio of the weight of the thin liquor to thick liquor |
| Answer» B. temperature of the feed | |
| 513. |
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place |
| A. | between two bodies in physical contact with each other. |
| B. | between two bodies not in physical contact with each other. |
| C. | from one part of a body to the another part of the same body. |
| D. | both 'b' & 'c' |
| Answer» C. from one part of a body to the another part of the same body. | |
| 514. |
h.D/K is called the __________ number. |
| A. | Nusselt |
| B. | Peclet |
| C. | Rayleigh |
| D. | Grashoff |
| Answer» B. Peclet | |
| 515. |
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 | |
| 516. |
The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is __________ compared to the same size pipes without fins. |
| A. | more |
| B. | less |
| C. | same |
| D. | unpredictable |
| Answer» C. same | |
| 517. |
Radiation heat losses from satisfactorily insulated high pressure boilar may be about __________ percent. |
| A. | 1 |
| B. | 7 |
| C. | 18 |
| D. | 26 |
| Answer» C. 18 | |
| 518. |
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. | |
| 519. |
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 | |
| 520. |
For the same heat load and mass flow rate in the tube side of a shell and tube heat exchanger, one may use multipass on the tube side, because it |
| A. | decreases the pressure drop. |
| B. | decreases the outlet temperature of cooling medium. |
| C. | increases the overall heat transfer coefficient. |
| D. | none of these. |
| Answer» D. none of these. | |
| 521. |
Rate of crystallisation does not depend upon the |
| A. | extent of supersaturation. |
| B. | turbulence within the solution. |
| C. | number and active surface area of the crystals. |
| D. | none of these. |
| Answer» E. | |
| 522. |
The ratio of velocity head to tube side return loss in case of a multipass shell and tube heat exchanger is |
| A. | 2 |
| B. | 43497 |
| C. | 4 |
| D. | 43556 |
| Answer» E. | |
| 523. |
Viscous & heat sensitive liquids are concentrated in __________ evaporators. |
| A. | open pan |
| B. | long tube |
| C. | agitated film |
| D. | none of these |
| Answer» D. none of these | |
| 524. |
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 | |
| 525. |
Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is |
| A. | finned tube heat exchanger with air inside and steam outside. |
| B. | finned tube heat exchanger with air outside and steam inside. |
| C. | shell and tube heat exchanger with air inside tubes and steam on shell side. |
| D. | shell and tube heat exchanger with air on shell side and steam inside tubes. |
| Answer» C. shell and tube heat exchanger with air inside tubes and steam on shell side. | |
| 526. |
In case of surface condensers, a straight line is obtained on plotting __________ on an ordinary graph paper. |
| A. | 1/-0.8 |
| B. | -0.8 |
| C. | -2 |
| D. | 1/-2 |
| Answer» B. -0.8 | |
| 527. |
The energy radiated from a surface Q at absolute temperature T is related as |
| A. | Q ‚àù T2 |
| B. | Q ‚àù T4 |
| C. | Q ‚àù T3 |
| D. | none of these |
| Answer» C. Q ‚àù T3 | |
| 528. |
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 | |
| 529. |
Heat transfer by __________ may not necessarily require the presence of a medium. |
| A. | conduction |
| B. | natural convection |
| C. | forced convection |
| D. | radiation |
| Answer» E. | |
| 530. |
In a single effect evaporator, the economy is |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | none of these |
| Answer» C. > 1 | |
| 531. |
The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are |
| A. | Re.Gz |
| B. | Nu, Pr |
| C. | Nu, Pr, Re |
| D. | Nu, Gz |
| Answer» E. | |
| 532. |
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 | |
| 533. |
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 | |
| 534. |
What is Nusselt number ? |
| A. | |
| B. | |
| C. | |
| D. | |
| Answer» C. | |
| 535. |
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. | |
| 536. |
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) | |
| 537. |
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 | |
| 538. |
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 | |
| 539. |
Viscosity of gases __________ with increase in temperature. |
| A. | increase very rapidly |
| B. | increase slowly |
| C. | decrease slowly |
| D. | remain unaffected |
| Answer» C. decrease slowly | |
| 540. |
Duhring rule is important in solving problems on |
| A. | distillation |
| B. | crystallisation |
| C. | evaporation |
| D. | humidification |
| Answer» D. humidification | |
| 541. |
Increasing the liquor level in the evaporator results in the |
| A. | decreased capacity. |
| B. | increase in liquor film co-efficient. |
| C. | decreased effect of hydrostatic head. |
| D. | increased true temperature drop. |
| Answer» B. increase in liquor film co-efficient. | |
| 542. |
'Duhring's plot' is of use in |
| A. | extractive distillation |
| B. | evaporation |
| C. | leaching |
| D. | absorption |
| Answer» C. leaching | |
| 543. |
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 | |
| 544. |
The steam ejector is used to |
| A. | remove condensate from the steam pipelines. |
| B. | create vacuum. |
| C. | superheat the steam. |
| D. | none of these. |
| Answer» C. superheat the steam. | |
| 545. |
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. | |
| 546. |
A dephlegmator is a |
| A. | total condenser |
| B. | vacuum evaporator |
| C. | partial condenser |
| D. | double pipe heat exchanger |
| Answer» D. double pipe heat exchanger | |
| 547. |
Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the |
| A. | existence of thermal boundary layer. |
| B. | temperature gradient produced due to density difference |
| C. | buoyancy of the bubbles produced at active nucleation site. |
| D. | none of these. |
| Answer» E. | |
| 548. |
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. | |
| 549. |
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. | |
| 550. |
Heat transfer efficiency leading of energy conservation in a heat exchanger can be achieved by |
| A. | keeping the heat transfer surface clean. |
| B. | enhancing the fluid pumping rate. |
| C. | increasing the tube length. |
| D. | none of these. |
| Answer» B. enhancing the fluid pumping rate. | |