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.
| 351. |
Conductance is given by(where, x = thickness, A = heat flow area, K = thermal conductivity.) |
| A. | x/KA |
| B. | KA/x |
| C. | K/Ax |
| D. | A/Kx |
| Answer» C. K/Ax | |
| 352. |
A BTU/hr.ft.² °F is equal to |
| A. | 1 kcal/hr. m²°C. |
| B. | 4.88 kcal/hr. m².°C. |
| C. | 1 kcal/hr. m².°K. |
| D. | none of these. |
| Answer» C. 1 kcal/hr. m².°K. | |
| 353. |
What is the absorptivity of a black body ? |
| A. | 1 |
| B. | 0 |
| C. | 0.78 |
| D. | 0.95 |
| Answer» B. 0 | |
| 354. |
Heat transfer co-efficient (h₁) for liquids increases with |
| A. | increasing temperature. |
| B. | decreasing temperature. |
| C. | decreasing Reynolds number. |
| D. | none of these. |
| Answer» B. decreasing temperature. | |
| 355. |
Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer co-efficient is 3k/l. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ? |
| A. | 35.5 |
| B. | 43.75 |
| C. | 81.25 |
| D. | 48.25 |
| Answer» D. 48.25 | |
| 356. |
Which of the following is correct ? |
| A. | Rate = Driving force x Resistance |
| B. | Driving force = Rate x Resistance |
| C. | Resistance = Driving force x Rate |
| D. | Rate = Resistance/Driving force |
| Answer» C. Resistance = Driving force x Rate | |
| 357. |
Which of the following has the highest thermal conductivity ? |
| A. | Brick |
| B. | Air |
| C. | Water |
| D. | Silver |
| Answer» E. | |
| 358. |
Which of the following is directly concerned with the heat transfer ? |
| A. | Strouhal number |
| B. | Sherwood number |
| C. | Euler number |
| D. | Grashoff number |
| Answer» E. | |
| 359. |
In case of __________ boiling, the bubbles formed on a submerged hot surface get absorbed in the mass of the liquid. |
| A. | nucleate |
| B. | pool |
| C. | low pressure |
| D. | none of these |
| Answer» C. low pressure | |
| 360. |
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body) |
| A. | αT |
| B. | α 1/T |
| C. | α T⁴ |
| D. | independent of T |
| Answer» C. α T⁴ | |
| 361. |
The equation, Nst = f/2, is the __________ analogy. |
| A. | Colburn |
| B. | Reynolds |
| C. | Prandtl |
| D. | none of these |
| Answer» C. Prandtl | |
| 362. |
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 | |
| 363. |
(NGr x NPr) is called the __________ number. |
| A. | Graetz |
| B. | Reyleigh |
| C. | Nusselt |
| D. | Stanton |
| Answer» C. Nusselt | |
| 364. |
The thermal radiation emitted by a body is proportional to Tⁿ, where T is its absolute temperature. The value of 'n' is exactly 4 for |
| A. | black painted bodies only |
| B. | all bodies |
| C. | polished bodies only |
| D. | a black body |
| Answer» C. polished bodies only | |
| 365. |
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 | |
| 366. |
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 | |
| 367. |
Which of the following has the lowest overall heat transfer co-efficient ? |
| A. | Dowtherm |
| B. | Molten sodium |
| C. | Water |
| D. | Air |
| Answer» E. | |
| 368. |
The type of liquor circulation system to be employed in evaporators (viz. natural or forced circulation) is determined mainly by the __________ of the liquid. |
| A. | viscosity |
| B. | density |
| C. | thermal conductivity |
| D. | corrosive nature |
| Answer» B. density | |
| 369. |
Film boiling occurs at __________ pressure. |
| A. | atmospheric |
| B. | sub-atmospheric |
| C. | negative |
| D. | very high |
| Answer» E. | |
| 370. |
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 | |
| 371. |
Which of the following has the minimum thermal conductivity ? |
| A. | Nitrogen |
| B. | Steel |
| C. | Carbon black |
| D. | Tar |
| Answer» B. Steel | |
| 372. |
Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, may be around __________ BTU. |
| A. | 180 |
| B. | 970 |
| C. | 3.97 |
| D. | none of these |
| Answer» B. 970 | |
| 373. |
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. | |
| 374. |
At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ? |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | none of these |
| Answer» B. < 1 | |
| 375. |
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 | |
| 376. |
Mc Adam relation is given by |
| A. | Nu = 0.023 (Re)^0.8 (Pr)^0.4 |
| B. | Nu = 0.023 (Re)^0.8 (Pr)^0.3 |
| C. | Nu = 0.023 (Re)^0.8 (Pr)^0.2 |
| D. | Nu = 0.023 (Re)^0.8 (Pr)^0.1 |
| Answer» B. Nu = 0.023 (Re)^0.8 (Pr)^0.3 | |
| 377. |
A nuclear reactor with its core constructed of parallel vertical plates 2.25 m high and 1.5 m wide has been designed on free convection heating of liquid bismuth. Metallurgical considerations limit the maximum surface temperature of the plate to 975 degree Celsius and the lowest allowable temperature of bismuth is 325 degree Celsius. Estimate the maximum possible heat dissipation from both sides of each plate. The appropriate correlation for the convection coefficient isNu = 0.13 (Gr Pr)^1/3 |
| A. | 143 MW |
| B. | 153 MW |
| C. | 163 MW |
| D. | 173 MV |
| Answer» C. 163 MW | |
| 378. |
For laminar flow over a flat plate, the average value of Nusselt number is prescribed by the relationNu = 0.664 (Re)^0.5 (Pr)^0.33Which of the following is then a false statement? |
| A. | Density has to be increased four times |
| B. | Plate length has to be decreased four times |
| C. | Specific heat has to be increased four times |
| D. | Dynamic viscosity has to be decreased sixteen times |
| Answer» E. | |
| 379. |
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 | |
| 380. |
In a backward feed multiple effect evaporator |
| A. | feed is introduced in the first effect. |
| B. | feed flows from low pressure to high pressure. |
| C. | no pumps are required between successive effects. |
| D. | none of these. |
| Answer» C. no pumps are required between successive effects. | |
| 381. |
Heat transfer by radiation between two bodies at T1 & T2 and in an ambient temperature of Ta°C depends on |
| A. | T1 - T2 |
| B. | T1 - Ta |
| C. | T2 - Ta |
| D. | none of these |
| Answer» E. | |
| 382. |
Which of the following situations can be approximated to a steady state heat transfer system ? |
| A. | A red hot steel slab (having outside surface temperature as 1300°C) exposed to the atmosheric air at 35°C. |
| B. | 10 kg of dry saturated steam at 8 kgf/cm² flowing through a short length of stainless steel pipe exposed to atmospheric air at 35°C. |
| C. | Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C. |
| D. | A sub-cooled refrigerant liquid at 8°C flowing at the rate of 6 Kg/minute through a copper pipe exposed to atmospheric air at 35°C. |
| Answer» C. Boiling brine kept in open vessel when the bottom surface temperature of the vessel is maintained constant at 180°C. | |
| 383. |
Which one gives the monochromatic emissive power for black body radiation ? |
| A. | Planck's law |
| B. | Kirchhoffs law |
| C. | Wien's law |
| D. | Stefan-Boltzman law |
| Answer» B. Kirchhoffs law | |
| 384. |
Overall heat transfer co-efficient of a particular tube is U1. If the same tube with some dirt deposited on either side has coefficient U2, then |
| A. | U1 = U2 |
| B. | U2 > U1 |
| C. | U1 > U2 |
| D. | U1 = dirt factor - U2 |
| Answer» B. U2 > U1 | |
| 385. |
Multiple effect evaporators are commonly used in the manufacture ofP. PaperQ. Superphosphate R. Sugar S. Fats |
| A. | P and Q |
| B. | P and R |
| C. | P and S |
| D. | R and S |
| Answer» D. R and S | |
| 386. |
Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids ? |
| A. | Dittus-Boeltier equation |
| B. | Sieder-Tate equation |
| C. | Nusselt equation |
| D. | None of these |
| Answer» C. Nusselt equation | |
| 387. |
Resistance to heat flow by conduction is proportional to (where, t & ρ are thickness & density of the material respectively and A = area normal to the direction of heat flow. ) |
| A. | t |
| B. | 1/ρ |
| C. | 1/A |
| D. | all (a), (b) & (c) |
| Answer» E. | |
| 388. |
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 (a) (b) and (c). |
| Answer» E. | |
| 389. |
What is the thermal conductivity of a perfect heat insulator ? |
| A. | zero |
| B. | one |
| C. | ∞ |
| D. | between 0 and ∞ |
| Answer» B. one | |
| 390. |
When does the heat generated by fluid friction becomes appreciable compared to the heat transferred between the fluids ? |
| A. | At high fluid velocity |
| B. | At low velocity |
| C. | When fluid flows past a smooth surface |
| D. | None of these |
| Answer» B. At low velocity | |
| 391. |
The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation. |
| A. | increases |
| B. | decreases |
| C. | remains constant |
| D. | may increase or decrease ; depends on the material |
| Answer» E. | |
| 392. |
The rate of heat transfer through a pipe wall is given by following equation. For cylinder of very thin wall, q can be approximated by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» E. | |
| 393. |
The Dietus-Boelter equation for convective heat transfer given by following equation, cannot be used for |
| A. | low Reynold's number |
| B. | very low Grashoff number |
| C. | molten metals |
| D. | all (a), (b) and (c) |
| Answer» E. | |
| 394. |
What is Nusselt number ? |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» C. C | |
| 395. |
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 | |
| 396. |
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 | |
| 397. |
Which of the following is the most controlling factor for the rate of bubble detachment from the hot solid surface ? |
| A. | Liquid density |
| B. | Liquid viscosity |
| C. | Hot surface temperature |
| D. | Interfacial tension |
| Answer» E. | |
| 398. |
Pick out the correct statement. |
| A. | Higher is the temperature of the radiating body, higher is the wavelength of radiation. |
| B. | Logarithmic mean area is used for calculating the heat flow rate through a thick walled cylinder. |
| C. | The wavelength corresponding to maximum mono-chromatic emissive power increases with rise in temperature. |
| D. | Solid angle subtended by the finite surface at the radiating element is called the angle of incidence. |
| Answer» C. The wavelength corresponding to maximum mono-chromatic emissive power increases with rise in temperature. | |
| 399. |
At steady state the temperature variation in a plane wall, made of two different solids I & II is shown below. The thermal conductivity of material I |
| A. | is smaller than that of II. |
| B. | is greater than that of II. |
| C. | is equal to that of II. |
| D. | can be greater than or smaller than that of II. |
| Answer» B. is greater than that of II. | |
| 400. |
Thermal diffusivity is given by |
| A. | A |
| B. | B |
| C. | C |
| D. | D |
| Answer» B. B | |