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MCQOPTIONS
This section includes 341 Mcqs, each offering curated multiple-choice questions to sharpen your Chemical Process Calculation knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
A person is found dead at 5 pm in a room whose temperature is 20 degree Celsius. The temperature of body is measured to be 25 degree Celsius, when found and heat transfer coefficient is estimated to be 8 W/m² K. Modeling the body as a 30 cm diameter, 1.7 cm long cylinder. Estimate the time of death of person. |
| A. | 13.55 seconds |
| B. | 12.55 seconds |
| C. | 11.55 seconds |
| D. | 10.55 seconds |
| Answer» E. | |
| 152. |
Let there is some conduction resistance, then temperature becomes a function of(i) Biot number(ii)Fourier number(iii) Dimensionless parameterIdentify the correct statement |
| A. | 1 and 2 |
| B. | 2 and 3 |
| C. | 1 and 3 |
| D. | 1, 2 and 3 |
| Answer» E. | |
| 153. |
A thermocouple junction in the form of 4 mm radius sphere is to be used to measure the temperature of a gas stream. The junction is initially at 35 degree Celsius and is placed in a gas stream which is at 300 degree Celsius. The thermocouple is removed from the hot gas stream after 10 seconds and kept in still air at 25 degree Celsius with convective coefficient 10 W/m² K. Find out the time constant of the thermocouple. Assume the thermos-physical properties as given below:h = 37.5 W/m² Kp = 7500 kg/m³c = 400 J/kg K |
| A. | 6.67 seconds |
| B. | 106.67 seconds |
| C. | 206.67 seconds |
| D. | 306.67 seconds |
| Answer» C. 206.67 seconds | |
| 154. |
An iron billet (k = 65 W/m K) measuring 20 * 15 * 80 cm is exposed to a convective flow resulting in convection coefficient of 11.5 W/m² K. Determine the Biot number |
| A. | 0.02376 |
| B. | 0.008974 |
| C. | 0.004563 |
| D. | 0.006846 |
| Answer» E. | |
| 155. |
When the surface temperature variation inside a solid are periodic in nature, the profile of temperature variation with time may assume |
| A. | Triangular |
| B. | Linear |
| C. | Parabolic |
| D. | Hyperbolic |
| Answer» B. Linear | |
| 156. |
Which of the following has units of time constant?(Where, P is density, A is area, c is specific heat and V is volume) |
| A. | p V/h A |
| B. | p c/h A |
| C. | p V c/h A |
| D. | V c/h A |
| Answer» D. V c/h A | |
| 157. |
The temperature variation of a thick brick wall during periodic heating or cooling follows a sinusoidal waveform. During a period of 24 hours, the surface temperature ranges from 25 degree Celsius to 75 degree Celsius. Workout the time lag of the temperature wave corresponding to a point located at 25 cm from the wall surface. Thermo-physical properties of the wall material are; thermal conductivity = 0.62 W/m K; specific heat = 450 J/kg K and density = 1620 kg/m³ |
| A. | 3.980 hour |
| B. | 6.245 hour |
| C. | 2.648 hour |
| D. | 3.850 hour |
| Answer» C. 2.648 hour | |
| 158. |
Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing them to an air stream at 25 degree Celsius. Find maximum value of convective coefficient that is permissible. Assume the following property valuesDensity = 2250 kg/m³Specific heat = 850 J/kg KConductivity = 1.5 W/m K |
| A. | 245 W/m²K |
| B. | 235 W/m²K |
| C. | 225 W/m²K |
| D. | 215 W/m²K |
| Answer» D. 215 W/m²K | |
| 159. |
The temperature distribution at a certain time instant through a 50 cm thick wall is prescribed by the relationT = 300 – 500 x – 100 x² + 140x³Where temperature t is in degree Celsius and the distance x in meters has been measured from the hot surface. If thermal conductivity of the wall material is 20 k J/m hr degree, calculate the heat energy stored per unit area of the wall |
| A. | 4100 k J/hr |
| B. | 4200 k J/hr |
| C. | 4300 k J/hr |
| D. | 4400 k J/hr |
| Answer» B. 4200 k J/hr | |
| 160. |
What is the value of characteristics length for cylinder? |
| A. | R/5 |
| B. | R/4 |
| C. | R/3 |
| D. | R/2 |
| Answer» E. | |
| 161. |
A 12 cm diameter cylindrical bar, initially at a uniform temperature of 40 degree Celsius, is placed in a medium at 650 degree Celsius with convective coefficient of 22 W/m² K. Determine the time required for the center to reach 255 degree Celsius. For the material of the bar:Thermal conductivity = 20 W/m KDensity = 580 kg/m³Specific heat = 1050 J/kg K |
| A. | 1234.5 seconds |
| B. | 1973.16 seconds |
| C. | 3487.3 seconds |
| D. | 2896.4 seconds |
| Answer» C. 3487.3 seconds | |
| 162. |
The time constant of a thermocouple is the time taken to |
| A. | Minimum time taken to record a temperature reading |
| B. | Attain 50% of initial temperature difference |
| C. | Attain the final value to be measured |
| D. | Attain 63.2% of the value of initial temperature difference |
| Answer» E. | |
| 163. |
The transient response of a solid can be determined by the equation. (Where, P is density, V is volume, c is specific heat and A is area) |
| A. | – 4 p V c = h A (t – t0) |
| B. | – 3 p V c = h A (t – t0) |
| C. | – 2 p V c = h A (t – t0) |
| D. | – p V c = h A (t – t0) |
| Answer» E. | |
| 164. |
“When Biot number exceeds 0.1 but is less than 100, use is made of Heislers charts for the solution of transient heat conduction”. Choose the correct answer |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» B. False | |
| 165. |
“Thermal radiation suffers no attenuation in a vacuum”. Choose the correct answer |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» B. False | |
| 166. |
The perturbation time varies as |
| A. | d²/α |
| B. | 2d²/α |
| C. | 3d²/α |
| D. | 4d²/α |
| Answer» B. 2d²/α | |
| 167. |
How does the body temperature falls or rises with time? |
| A. | Logarithmic |
| B. | Parabolic |
| C. | Linear |
| D. | Exponentially |
| Answer» E. | |
| 168. |
For a plat plate (thickness δ, breadth b and height h) the heat exchange occurs from both the sides. The characteristics length is equal to |
| A. | δ/4 |
| B. | δ/3 |
| C. | δ/2 |
| D. | δ |
| Answer» D. δ | |
| 169. |
A large steel plate 50 mm thick is initially at a uniform temperature of 425 degree Celsius. It is suddenly exposed on both sides to an environment with convective coefficient 285 W/m² K and temperature 65 degree Celsius. Determine the center line temperature.For steel, thermal conductivity = 42.5 W/m K and thermal diffusivity = 0.043 m²/hr |
| A. | 261 degree Celsius |
| B. | 271 degree Celsius |
| C. | 281 degree Celsius |
| D. | 291 degree Celsius |
| Answer» D. 291 degree Celsius | |
| 170. |
“A solid which extend itself infinitely in all directions of space is termed as finite solid”. Choose the correct answer |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» C. May be | |
| 171. |
Time lag is given by the formula |
| A. | x/2 [1/ (α π n)^½]. |
| B. | x/3 [1/ (α π n)^½]. |
| C. | x/4 [1/ (α π n)^½]. |
| D. | x/5 [1/ (α π n)^½]. |
| Answer» B. x/3 [1/ (α π n)^½]. | |
| 172. |
Fourier number is given by |
| A. | α T/LC² |
| B. | 2 α T/LC² |
| C. | 3 α T/LC² |
| D. | 4 α T/LC² |
| Answer» B. 2 α T/LC² | |
| 173. |
The surface temperature oscillates about the mean temperature level in accordance with the relation |
| A. | α S,T – α S,A = 2 sin (2 π n T) |
| B. | α S,T – α S,A = 5 sin (2 π n T) |
| C. | α S,T – α S,A = sin (2 π n T) |
| D. | α S,T – α S,A = 3 sin (2 π n T) |
| Answer» D. α S,T – α S,A = 3 sin (2 π n T) | |
| 174. |
At a certain time instant, the temperature distribution in a long cylindrical fire tube can be represented approximately by the relationT = 650 + 800 r – 4250 r²Where temperature t is in degree Celsius and radius r is in meter. Find the rate of heat flow such that the tube measures: inside radius 25 cm, outside radius 40 cm and length 1.5 m.For the tube materialK = 5.5 W/m Kα = 0.004 m²/hr |
| A. | 3.672 * 10 8 W |
| B. | 3.672 * 10 2 W |
| C. | 3.672 * 10 5 W |
| D. | – 3.672 * 10 5 W |
| Answer» E. | |
| 175. |
Lumped parameter analysis for transient heat conduction is essentially valid for |
| A. | B I < 0.1 |
| B. | 1 < B I < 10 |
| C. | 0.1 < B I < 0.5 |
| D. | It tends to infinity |
| Answer» B. 1 < B I < 10 | |
| 176. |
Diagram shows transient heat conduction in an infinite plane wall. Identify the correct boundary condition in transient heat conduction in solids with finite conduction. |
| A. | t = t i at T = 0 |
| B. | d t /d x = 1 at x = 0 |
| C. | d t /d x = infinity at x = 1 |
| D. | d t / d x = infinity at x = 0 |
| Answer» B. d t /d x = 1 at x = 0 | |
| 177. |
A large plane wall, 40 cm thick and 8 m² area, is heated from one side and temperature distribution at a certain time instant is approximately prescribed by the relation:T = 80 – 60 x +12 x² + 25 x³ – 20 x⁴Where temperature t is in degree Celsius and the distance x in meters. Make calculations for heat energy stored in the wall in unit time.For wall material:Thermal conductivity = 6 W/m K and thermal diffusivity = 0.02 m²/hr |
| A. | 870.4 W |
| B. | 345.6 W |
| C. | 791.04 W |
| D. | 238.5 W |
| Answer» D. 238.5 W | |
| 178. |
The curve for unsteady state cooling or heating of bodies is |
| A. | Hyperbolic curve asymptotic both to time and temperature axis |
| B. | Exponential curve asymptotic both to time and temperature axis |
| C. | Parabolic curve asymptotic to time axis |
| D. | Exponential curve asymptotic to time axis |
| Answer» E. | |
| 179. |
Which is true regarding lumped system analysis?(i) Conductive resistance = 0(ii) Convective resistance = 0(iii) Thermal conductivity = 0(iv) Thermal conductivity = infinityIdentify the correct statements |
| A. | 1 and 2 |
| B. | 1, 2 and 4 |
| C. | 1 and 4 |
| D. | 2 and 4 |
| Answer» D. 2 and 4 | |
| 180. |
The temperature and rate of heat conduction are undoubtedly dependent on |
| A. | Time coordinates |
| B. | Space coordinates |
| C. | Mass coordinates |
| D. | Both time and space coordinates |
| Answer» E. | |
| 181. |
A mild steel plate 5 cm thick and initially at 40 degree Celsius temperature is suddenly exposed on one side to a fluid which causes the surface temperature to increase to and remain at 90 degree Celsius. Calculate maximum time that the slab be treated as a semi-infinitely bodyFor steel, thermal diffusivity = 1.25 * 10¯⁵ m²/s |
| A. | 100 seconds |
| B. | 200 seconds |
| C. | 300 seconds |
| D. | 400 seconds |
| Answer» C. 300 seconds | |
| 182. |
Which of the following is an example of lump system analysis? |
| A. | Heating or cooling of fine thermocouple wire due to change in ambient temperature |
| B. | Heating of an ingot in an furnace |
| C. | Cooling of bars |
| D. | Cooling of metal billets in steel works |
| Answer» B. Heating of an ingot in an furnace | |
| 183. |
Transient condition means |
| A. | Conduction when temperature at a point varies with time |
| B. | Very little heat transfer |
| C. | Heat transfer with a very little temperature difference |
| D. | Heat transfer for a short time |
| Answer» B. Very little heat transfer | |
| 184. |
A thermocouple junction of spherical form is to be used to measure the temperature of the gas stream. The junction is at 20 degree Celsius and is placed in a gas stream which is at 200 degree Celsius. Make calculations for junction diameter needed for the thermocouple to have thermal time constant of one second. Assume the thermos-physical properties as given belowk = 20 W/ m Kh = 350 W/m² Kc = 0.4 k J/kg Kp = 8000 kg/m³ |
| A. | 0.556 mm |
| B. | 0.656 mm |
| C. | 0.756 mm |
| D. | 0.856 mm |
| Answer» C. 0.756 mm | |
| 185. |
A water line is buried underground in dry soil that has an assumed initial temperature of 4.5 degree Celsius. The pipe may have no flow through it for long period of time, yet it will not be drained in order that no freezing occurs, the pipe must be kept at a temperature not lower than 0 degree Celsius. The pipe is to be designed for a 30 hour period at the beginning of which the soil surface temperature suddenly drops to – 17 degree Celsius. Workout the minimum earth covering needed above the water pipe so as to prevent the possibility of freezing during 36 hour cold spell. The soil in which the pipe is buried has the following propertiesDensity = 640 kg/m³Specific heat = 1843J/kg degreeThermal conductivity = 0.345 W/m degree |
| A. | 0.25 m |
| B. | 0.35 m |
| C. | 0.45 m |
| D. | 0.55 m |
| Answer» C. 0.45 m | |
| 186. |
A single cylinder 2-stroke engine operates at 1500 rpm. Calculate the depth where the temperature wave due to variation in cylinder is damped to 1% of its surface value. For the cylinder material, thermal diffusivity = 0.042 m²/hr |
| A. | 0.1996 cm |
| B. | 0.3887 cm |
| C. | 0.2774 cm |
| D. | 0.1775 cm |
| Answer» E. | |
| 187. |
“An infinite solid is one which extends itself infinitely in all directions of space”. Identify the correct option |
| A. | True |
| B. | False |
| C. | May be |
| D. | Can't say |
| Answer» B. False | |
| 188. |
In the lumped system parameter model, the variation of temperature with time is |
| A. | Linear |
| B. | Exponential |
| C. | Sinusoidal |
| D. | Cube |
| Answer» C. Sinusoidal | |
| 189. |
During heat treatment, cylindrical pieces of 25 mm diameter, 30 mm height and at 30 degree Celsius are placed in a furnace at 750 degree Celsius with convective coefficient 80 W/m² degree. Calculate the time required to heat the pieces to 600 degree Celsius. Assume the following property valuesDensity = 7850 kg /m³Specific heat = 480 J/kg KConductivity = 40 W/m degree |
| A. | 226 sec |
| B. | 326 sec |
| C. | 426 sec |
| D. | 526 sec |
| Answer» C. 426 sec | |
| 190. |
In the non-dimensional Biot number, the characteristics length is the ratio of |
| A. | Perimeter to surface area of solid |
| B. | Surface area to perimeter of solid |
| C. | Surface area to volume of solid |
| D. | Volume of solid to its surface area |
| Answer» E. | |
| 191. |
Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing them to an air stream at 25 degree Celsius. Find the minimum time required for cooling to a temperature of 60 degree Celsius. Assume the following property valuesDensity = 2250 kg/m³Specific heat = 850 J/kg KConductivity = 1.5 W/m K |
| A. | 13.78 seconds |
| B. | 14.78 seconds |
| C. | 15.78 seconds |
| D. | 16.78 seconds |
| Answer» C. 15.78 seconds | |
| 192. |
According to lumped system analysis, solid possesses thermal conductivity that is |
| A. | Infinitely large |
| B. | Infinitely small |
| C. | Moderate |
| D. | 50% small |
| Answer» B. Infinitely small | |
| 193. |
A mercury thermometer with bulb idealized as a sphere of 1 mm radius is used for measuring the temperature of fluid whose temperature is varying at a fast rate. For mercuryk = 10 W/m Kα = 0.00005 m²/sh = 10 W/m² KIf the time for the temperature change of the fluid is 3 second, what should be the radius of thermocouple to read the temperature of the fluid?For the thermocouple materialk = 100 W/m Kα = 0.0012 m²/sh = 18 W/m² K |
| A. | .864 mm |
| B. | .764 mm |
| C. | .664 mm |
| D. | .564 mm |
| Answer» B. .764 mm | |
| 194. |
A large steel ingot, which has been uniformly heated to 750 degree Celsius, is hardened by quenching it in an oil bath that is maintained at 25 degree Celsius. What length of time is required for the temperature to reach 600 degree Celsius at a depth of 1 cm? Thermal diffusivity for the steel ingot is 1.21 * 10¯⁵ m²/s. The ingot may be approximated as a flat plate |
| A. | 4.55 seconds |
| B. | 3.55 seconds |
| C. | 2.55 seconds |
| D. | 1.55 seconds |
| Answer» D. 1.55 seconds | |
| 195. |
Water pipes are to be buried underground in a wet soil (thermal diffusivity = 2.78 * 10¯³ m²/s) which is initially at 4.5 degree Celsius. The soil surface temperature suddenly drops to -5 degree Celsius and remains at this value for₁0 hours. Calculate the minimum depth at which the pipe be laid if the surrounding soil temperature is to remain above 0 degree Celsius. The soil may be considered as semi-infinite solid |
| A. | 0.467 m |
| B. | 0.367 m |
| C. | 0.267 m |
| D. | 0.167 m |
| Answer» E. | |
| 196. |
A flat wall of fire clay, 50 cm thick and initially at 25 degree Celsius, has one of its faces suddenly exposed to a hot gas at 950 degree Celsius. If the heat transfer coefficient on the hot side is 7.5 W/m² K and the other face of the wall is insulated so that no heat passes out of that face, determine the time necessary to raise the center of the wall to 350 degree Celsius. For fire clay brickThermal conductivity = 1.12 W/m KThermal diffusivity = 5.16 * 10¯⁷ m²/s |
| A. | 43.07 hours |
| B. | 53.07 hours |
| C. | 63.07 hours |
| D. | 73.07 hours |
| Answer» B. 53.07 hours | |
| 197. |
A 2 cm thick steel slab heated to 525 degree Celsius is held in air stream having a mean temperature of 25 degree Celsius. Estimate the time interval when the slab temperature would not depart from the mean value of 25 degree Celsius by more than 0.5 degree Celsius at any point in the slab. The steel plate has the following thermal physical propertiesDensity = 7950 kg/m³C P = 455 J/kg KK = 46 W/m K |
| A. | 6548 s |
| B. | 6941 s |
| C. | 4876 s |
| D. | 8760 s |
| Answer» C. 4876 s | |
| 198. |
A low value of time constant can be achieved for a thermocouple by(i) Increasing the wire diameter(ii) Increasing the value heat transfer coefficient(iii) Use light metals of low density and low specific heatIdentify the correct statements |
| A. | 2 and 3 |
| B. | 1 and 3 |
| C. | 1 and 2 |
| D. | 1, 2 and 3 |
| Answer» B. 1 and 3 | |
| 199. |
A gold ring (k = 65 W/m K) measuring 15 * 10 * 60 cm is exposed to a surface where h = 11.5 W/m² K. Find the value of biot number |
| A. | 0.68 |
| B. | 0.58 |
| C. | 0.48 |
| D. | 0.38 |
| Answer» D. 0.38 | |
| 200. |
What percentage of water an average human body can have? |
| A. | 52% |
| B. | 62% |
| C. | 72% |
| D. | 82% |
| Answer» D. 82% | |