MCQOPTIONS
Saved Bookmarks
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.
| 151. |
In free con-vection heat transfer, Nusselt number is function of |
| A. | Grashoff no. and Reynold no. |
| B. | Grashoff no. and Prandtl no. |
| C. | Prandtl no. and Reynold no. |
| D. | Grashoff no., Prandtl no. and Reynold no. |
| E. | none of the above. |
| Answer» C. Prandtl no. and Reynold no. | |
| 152. |
If a single tube pass heat exchanger is converted to two pass, then for the same flow rate,the pressure drop per unit length in tube side will |
| A. | Increase by 1.8 times |
| B. | Decrease by 22 |
| C. | Increase by 216 |
| D. | Remain unchanged |
| Answer» D. Remain unchanged | |
| 153. |
Absorptivity and reflectivity of a perfect black body are respectively |
| A. | 1 and 0 |
| B. | 0 and 1 |
| C. | 1 and ∞ |
| D. | 0 and 0.5 |
| Answer» B. 0 and 1 | |
| 154. |
The Nusselt number for fully developed (both thermally and hydrodynamically) laminarflow through a circular pipe, where the wall heat flux is constant, is |
| A. | 2.36 |
| B. | 4.36 |
| C. | 120.36 |
| D. | Dependent on NRe only |
| Answer» C. 120.36 | |
| 155. |
The statement that "maximum wavelength of radiation is inversely proportional to thetemperature" is __________ law. |
| A. | Stefan-Boltzmann’s |
| B. | Planck's |
| C. | Wien's displacement |
| D. | None of these |
| Answer» D. None of these | |
| 156. |
A multiple effect evaporator as compared to a single effect evaporator of the same capacityhas |
| 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 | |
| 157. |
The driving potential for the crystal growth during crystallisation is the __________ of thesolution. |
| A. | Concentration |
| B. | Viscosity |
| C. | Super-saturation |
| D. | Density |
| Answer» D. Density | |
| 158. |
According to Stefan-Boltzmann law, ideal radiators emit radiant energy at a rateproportional to |
| A. | absolute temperature |
| B. | square of temperature |
| C. | fourth power of absolute temperature |
| D. | fourth power of temperature |
| E. | cube of absolute temperature. |
| Answer» D. fourth power of temperature | |
| 159. |
In a single evaporator system, the steam economy __________ by creating vacuum in theevaporator. |
| A. | Increases |
| B. | Decreases |
| C. | Remain constant |
| D. | May increase or decrease, depends on the vacuum |
| Answer» B. Decreases | |
| 160. |
Heat produced when a steady state current, I passes through an electrical conductor havingresistance, 'R' is |
| A. | IR |
| B. | I2R |
| C. | IR2 |
| D. | I2R2 |
| Answer» C. IR2 | |
| 161. |
Heat flux increases with temperature drop beyond the Leiden frost point in the plot of heatflux vs. temperature drop for a boiling liquid, because |
| A. | Convection becomes important |
| B. | Conduction becomes important |
| C. | Radiation becomes important |
| D. | Sub-cooled boiling occurs |
| Answer» D. Sub-cooled boiling occurs | |
| 162. |
Radiation heat losses from satisfactorily insulated high pressure boiler may be about __________ percent. |
| A. | 1 |
| B. | 7 |
| C. | 18 |
| D. | 26 |
| Answer» C. 18 | |
| 163. |
Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient ofdirty surface U2 = heat transfer co-efficient of clean surface). |
| A. | U1 - U2 |
| B. | 1/U1 - 1/U2 |
| C. | 1/U2 - 1/U1 |
| D. | U2 - U1 |
| Answer» C. 1/U2 - 1/U1 | |
| 164. |
Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids areclean and non-fouling? |
| A. | Square pitch |
| B. | Triangular pitch |
| C. | Diagonal square pitch |
| D. | None of these |
| Answer» C. Diagonal square pitch | |
| 165. |
For small temperature difference, the heat transfer rate as per Newton's law of cooling isproportional to (where, Δt = excess temperature) |
| A. | Δt |
| B. | Δt2 |
| C. | Δt3 |
| D. | √(Δt) |
| Answer» B. Δt2 | |
| 166. |
With increase in the distance between the heat source and the object receiving the heat, theradiation heat transfer |
| A. | Decreases |
| B. | Increases |
| C. | Increases exponentially |
| D. | Remain unaffected |
| Answer» B. Increases | |
| 167. |
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. | |
| 168. |
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 | |
| 169. |
A diathermanous substance __________ the thermal radiation completely. |
| A. | Absorbs |
| B. | Reflects |
| C. | Transmits |
| D. | None of these |
| Answer» D. None of these | |
| 170. |
Reason for operating an evaporator in multiple effects is to secure |
| A. | Increased steam economy |
| B. | Decreased steam consumption |
| C. | Both (A) and (B) |
| D. | Increased capacity |
| Answer» D. Increased capacity | |
| 171. |
Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, maybe around __________ BTU. |
| A. | 180 |
| B. | 970 |
| C. | 3.97 |
| D. | None of these |
| Answer» B. 970 | |
| 172. |
Heat transfer occurs by natural convection because change in temperature causesdifference in |
| A. | Viscosity |
| B. | Density |
| C. | Thermal conductivity |
| D. | Heat capacity |
| Answer» C. Thermal conductivity | |
| 173. |
Critical value of the __________ number governs the transition from laminar to turbulentflow in free convection heat transfer. |
| A. | Grashoff |
| B. | Reynolds |
| C. | Both 'a' & 'b' |
| D. | Prandtl & Grashoff |
| Answer» E. | |
| 174. |
Steady state one dimensional heat flow by conduction as given by Fourier's low does notassume that |
| A. | There is no internal heat generation |
| B. | Boundary surfaces are isothermal |
| C. | Material is anisotropic |
| D. | Constant temperature gradient exists |
| Answer» D. Constant temperature gradient exists | |
| 175. |
In case of __________ boiling, the bubbles formed on a submerged hot surface getabsorbed in the mass of the liquid. |
| A. | Nucleate |
| B. | Pool |
| C. | Low pressure |
| D. | None of these |
| Answer» C. Low pressure | |
| 176. |
The value of Stefan-Boltzmann constant in SI unit is |
| A. | 5.6697 × 10-8W/m2.°K4 |
| B. | 0.1714 × 10-8W/m2.°K4 |
| C. | 5.6697 × 10-8kcal/m2. °K4 |
| D. | 0.1714 × 10-8kcal/m2. °K4 |
| Answer» B. 0.1714 × 10-8W/m2.°K4 | |
| 177. |
Circulation pump is located below the evaporator to |
| A. | Avoid cavitation |
| B. | Avoid frequent priming |
| C. | Create more suction head |
| D. | None of these |
| Answer» D. None of these | |
| 178. |
Asymptotic conditions is reached, when for a fluid flowing in laminar flow through a longtube |
| 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 | |
| 179. |
LMTD for counter-flow and parallel flow heat exchanger will be the same, when the |
| A. | Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid) |
| B. | Outlet 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. Outlet temperature of both the hot and cold fluid are same | |
| 180. |
Cpµ/K is termed as the __________ number. |
| A. | Grashoff |
| B. | Nusselt |
| C. | Prandtl |
| D. | Stanton |
| Answer» D. Stanton | |
| 181. |
The rate of energy emission from unit surface area through unit solid angle,along a normal to the surface, is known as |
| A. | emissivity |
| B. | transmissivity |
| C. | reflectivity |
| D. | intensity of radiation |
| E. | absorptivity. |
| Answer» E. absorptivity. | |
| 182. |
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. | |
| 183. |
At what value of Prandtl number, the hydrodynamic and thermal boundary layers of afluid flowing over a heated plate will be identical? |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | None of these |
| Answer» B. < 1 | |
| 184. |
For a fluid flowing in an annulus space, the wetted perimeter for heat transfer andpressure drop are |
| A. | Same |
| B. | Different |
| C. | Never different |
| D. | Linearly related |
| Answer» C. Never different | |
| 185. |
For a given ambient air temperature with increase in the thickness of insulation of a hotcylindrical pipe, the rate of heat loss from the surface would |
| A. | Decrease |
| B. | Increase |
| C. | First decrease and then increase |
| D. | First increase and then decrease |
| Answer» E. | |
| 186. |
Colburn analogy is applicable for the value of Prandtl number from |
| A. | 0.001 to 1 |
| B. | 0.6 to 120 |
| C. | 0.5 to 5 |
| D. | 120 to 400 |
| Answer» C. 0.5 to 5 | |
| 187. |
The value of the wavelength for maximum emissive power is given by — |
| A. | Wien’s law |
| B. | Planck’s law |
| C. | Stefan’s law |
| D. | Fourier’s law |
| E. | Kirchhoff’s law. |
| Answer» B. Planck’s law | |
| 188. |
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the DittusBoelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heattransfer co-efficient will change by a factor of |
| A. | 1 |
| B. | 1.74 |
| C. | 6.1 |
| D. | 37 |
| Answer» D. 37 | |
| 189. |
Steam consumption in kg/hr in case of an evaporator is given by (where, C & E arecapacity the economy of the evaporator respectively). |
| A. | C/E |
| B. | E/C |
| C. | CE |
| D. | 1/CE |
| Answer» B. E/C | |
| 190. |
Which of the following accessories is provided in the vapor line of an evaporator forremoving the entrained liquid? |
| A. | Bleed point |
| B. | Vent |
| C. | Catchall |
| D. | Baffle |
| Answer» D. Baffle | |
| 191. |
In case of a super-cooled 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 | |
| 192. |
Sensible heat of hot industrial flue gases cannot be recovered by a/an |
| A. | Economiser |
| B. | Regenerator |
| C. | Ceramic recuperator |
| D. | None of these |
| Answer» E. | |
| 193. |
Sensible heat absorbed by 1 lb of water when it is heated from 32 to 212°F may be around__________ BTU. |
| A. | 180 |
| B. | 970 |
| C. | 3.97 |
| D. | Data insufficient, can't be predicted |
| Answer» B. 970 | |
| 194. |
For a liquid in laminar flow through a very long tube, when the exit fluid temperatureapproaches the wall temperature, the equation to be used is |
| A. | Nu = 0.023 Re0.8. Pr0.4 |
| B. | Nu = (π/2) Gz |
| C. | Nu = (2/π) Gz |
| D. | Nu = 2Gz0.5 |
| Answer» D. Nu = 2Gz0.5 | |
| 195. |
Electromagnetic radiations propagate in vacuum with a velocity of __________metre/second. |
| A. | 3 × 105 |
| B. | 3 × 108 |
| C. | 3 × 1010 |
| D. | 3 × 1012 |
| Answer» C. 3 × 1010 | |
| 196. |
Which is the most suitable for the concert-ration 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 | |
| 197. |
Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/µ) 0.8 (CP.µ/k) 0.4. This is valid for the value of NRe equal to |
| A. | < 2100 |
| B. | 2100-4000 |
| C. | > 4000 |
| D. | > 10000 |
| Answer» E. | |
| 198. |
'Fouling factor' used in the design of a multipass shell and tube heat exchanger is awww.objectivebooks.com |
| A. | Non-dimensional factor |
| B. | Factor of safety |
| C. | Conversion factor for individual film heat transfer co-efficient to overall heat transfer coefficient |
| D. | None of these |
| Answer» C. Conversion factor for individual film heat transfer co-efficient to overall heat transfer coefficient | |
| 199. |
Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by thetube length/diameter ratio, if the flow is in the __________ zone. |
| A. | Laminar |
| B. | Transition |
| C. | Both 'a' & 'b' |
| D. | Highly turbulent |
| Answer» E. | |
| 200. |
Which of the following is the most widely used heat insulating material for pipelinescarrying 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. | |