MCQOPTIONS
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MCQOPTIONS
This section includes 153 Mcqs, each offering curated multiple-choice questions to sharpen your Mechanical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 101. |
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. | |
| 102. |
A multiple effect evaporator has a capacity to process 4000 kg of solid caustic soda per day, when it is concentrating from 10% to 25% solids. The water evaporated in kg per day is |
| A. | 6000 |
| B. | 24000 |
| C. | 60000 |
| D. | 48000 |
| Answer» C. 60000 | |
| 103. |
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. | |
| 104. |
Two plates spaced 150 mm apart are maintained at 1000 C and 70 C. The heat transfer will take place mainly by |
| A. | convection |
| B. | free convection |
| C. | forced convection |
| D. | radiation |
| E. | radiation and convection. |
| Answer» E. radiation and convection. | |
| 105. |
The heat flux in the nucleate boiling regimes is proportional to (where, T = excess temperature) |
| A. | ( T)2 |
| B. | ( T)4 |
| C. | ( T)3 |
| D. | ( T) |
| Answer» D. ( T) | |
| 106. |
In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased. |
| A. | Velocity of circulation |
| B. | Liquor-film co-efficient |
| C. | Both (A) and (B) |
| D. | Neither (A) and (B) |
| Answer» E. | |
| 107. |
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 | |
| 108. |
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. | |
| 109. |
Radiant energy received by a body is proportional to (where, d = the distance between the object emitting radiation and that receiving it.) |
| A. | d |
| B. | d |
| C. | d2 |
| D. | d1.5 |
| Answer» D. d1.5 | |
| 110. |
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. | 0.50 D |
| C. | 0.75 D |
| D. | None of these |
| Answer» D. None of these | |
| 111. |
According to Stefan-Boltzmann law, ideal radiators emit radiant energy at a rate proportional 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 | |
| 112. |
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. | |
| 113. |
With increase in the distance between the heat source and the object receiving the heat, the radiation heat transfer |
| A. | Decreases |
| B. | Increases |
| C. | Increases exponentially |
| D. | Remain unaffected |
| Answer» B. Increases | |
| 114. |
A sphere of radius 'R1' is enclosed in a sphere of radius 'R2'. The view (or shape) factor for radiative heat transfer of the outer sphere with respect to the inner sphere is |
| A. | 0 |
| B. | R2/(R1+R2) |
| C. | 1 |
| D. | (R1/R2) 2 |
| Answer» C. 1 | |
| 115. |
In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) |
| A. | D/5 and D |
| B. | D/2 and 2 D |
| C. | D/4 and 2 D |
| D. | D and 2 D |
| Answer» B. D/2 and 2 D | |
| 116. |
Minimum recommended baffle spacing in a shell and tube heat exchanger is about (where, D = shell diameter). |
| A. | 0.2 D |
| B. | 0.5 D |
| C. | 0.66 D |
| D. | 0.80 D |
| Answer» B. 0.5 D | |
| 117. |
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 | |
| 118. |
As the difference between the wall temperature and bulk temperature increases, the boiling heat transfer co-efficient |
| A. | Continues to increase |
| B. | Continues to decrease |
| C. | Goes through a minimum |
| D. | Goes through a maximum |
| Answer» D. Goes through a maximum | |
| 119. |
The maximum heat transfer co-efficient from steam heating will be attained when the steam is: |
| A. | Supersaturated |
| B. | Saturated |
| C. | Wet |
| D. | None of these |
| Answer» C. Wet | |
| 120. |
In case of __________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface. |
| A. | Nucleate |
| B. | Local |
| C. | Pool |
| D. | Saturated |
| Answer» C. Pool | |
| 121. |
Steady state one dimensional heat flow by conduction as given by Fourier's low does not assume 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 | |
| 122. |
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 | |
| 123. |
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. | |
| 124. |
In heat transfer, conductance equals conductivity (kcal/hr/sqm/ C/cm) divided by |
| A. | hr (time) |
| B. | sqm (area) |
| C. | C (temperature) |
| D. | cm (thickness) |
| E. | kcal (heat). |
| Answer» E. kcal (heat). | |
| 125. |
One kilogram of water at 0 C is changed to superheated steam of one atm pressure and 300 C. The major heat consumption in the process will be to |
| A. | Heat the water from 0 C to 100 C |
| B. | Evaporate the water |
| C. | To superheat the steam |
| D. | Data insufficient, can't be predicted |
| Answer» C. To superheat the steam | |
| 126. |
Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is |
| A. | 0.5 |
| B. | 2 |
| C. | 10 |
| D. | 100 |
| Answer» C. 10 | |
| 127. |
Thickness of thermal boundary layer is more compared to that of hydrodynamic boundary layer, when the value of Prandtl number is |
| A. | 1 |
| B. | < 1 |
| C. | > 1 |
| D. | > 5 |
| Answer» C. > 1 | |
| 128. |
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 | |
| 129. |
The dimensionless group in mass transfer that is equivalent to Prandtl number in heat transfer is |
| A. | Nusselt number |
| B. | Sherwood number |
| C. | Schmidt number |
| D. | Stanton number |
| Answer» D. Stanton number | |
| 130. |
At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe? |
| A. | 0.5 |
| B. | < 0.5 |
| C. | > 0.6 |
| D. | < 0.1 |
| Answer» D. < 0.1 | |
| 131. |
Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is |
| A. | 0.2 |
| B. | 0.4 |
| C. | 0.6 |
| D. | 0.8 |
| Answer» D. 0.8 | |
| 132. |
Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is |
| A. | 0.1 |
| B. | > 1 |
| C. | < 1 |
| D. | 1 |
| Answer» B. > 1 | |
| 133. |
Mode of heat transfer in which the fluid moves under the influence of changes in fluid pressure produced by external work is called |
| A. | Radiation |
| B. | Natural convection |
| C. | Forced convection |
| D. | Conduction |
| Answer» D. Conduction | |
| 134. |
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. | |
| 135. |
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 | |
| 136. |
In case of parallel flow heat exchanger, the lowest temperature theoretically attainable by the hot fluid is __________ the outlet temperature of the cold fluid. |
| A. | Equal to |
| B. | More than |
| C. | Less than |
| D. | Either more or less than (depending upon the fluid) |
| Answer» B. More than | |
| 137. |
'Fouling factor' used in the design of a multipass shell and tube heat exchanger is a www.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 | |
| 138. |
Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is |
| A. | In the central core of the fluid |
| B. | Uniformly distributed throughout the fluid |
| C. | Mainly confined to a thin film of fluid near the surface |
| D. | None of these |
| Answer» D. None of these | |
| 139. |
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 | |
| 140. |
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 | |
| 141. |
Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer. |
| A. | Grashoff |
| B. | Biot |
| C. | Stanton |
| D. | Reynolds |
| Answer» B. Biot | |
| 142. |
In case of heat transfer by conduction in a hollow cylinder, __________ mean area is used to calculate the heat transfer rate. |
| A. | Geometric |
| B. | Arithmetic |
| C. | Logarithmic |
| D. | Either (A), (B) or (C) |
| Answer» D. Either (A), (B) or (C) | |
| 143. |
Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty 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 | |
| 144. |
Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone. |
| A. | Laminar |
| B. | Transition |
| C. | Both 'a' & 'b' |
| D. | Highly turbulent |
| Answer» E. | |
| 145. |
The average heat transfer co-efficient for laminar film condensation on vertical surface is inversely proportional to (where, T = Temperature drop across condensate film) |
| A. | ( T)2 |
| B. | ( T) |
| C. | ( T)1/4 |
| D. | ( T)3/2 |
| Answer» D. ( T)3/2 | |
| 146. |
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. | |
| 147. |
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 | |
| 148. |
The average heat transfer co-efficient over the entire length of the plate (ha) and the local heat transfer co-efficient (hL), in case of heat transfer over a flat plate in laminar zone is related as |
| A. | ha = 0.8hL |
| B. | ha = 2hL |
| C. | ha = hL |
| D. | ha = 5hL |
| Answer» C. ha = hL | |
| 149. |
If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is |
| A. | 1 |
| B. | 2 |
| C. | 1/2 |
| D. | 4 |
| Answer» C. 1/2 | |
| 150. |
LMTD in case of counter flow heat exchanger as compared-to parallel flow heat exchanger is |
| A. | higher |
| B. | lower |
| C. | same |
| D. | depends on the area of heat exchanger |
| E. | depends on temperature conditions. |
| Answer» B. lower | |