chemical engineering heat transfer chemical engineering MCQs – Page 9

Practise multiple-choice questions from chemical engineering heat transfer chemical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

chemical engineering heat transfer chemical engineering Mcqs
161. The non-dimensional temperature gradient in a liquid at the wall of a pipe is the ____________________?
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A. Heat flux

B. Prandtl number

C. Schmidt number

D. Nusselt number

162. Stefan-Boltzmann law applies to _____________ body?
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A. Black

B. Any colour

C. Grey

D. White

163. Stefans block body radiation law can also be derived from ______________ law?
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A. Fouriers

B. Plancks

C. None of these

D. Kirchoffs

164. Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?
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A. Grashoff

B. Reynolds

C. Both a & b

D. Prandtl & Grashoff
165. What is the unit of thermal conductivity ?
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A. Kcal/hr. C

B. Kcal/hr.m.C

C. Kcal/hr. m2 C

D. Kcal/hr.m

166. 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______________________?
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A. 2000

B. 5000

C. 4000

D. 6000

167. Heat transfer rate per unit area is called_________________?
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A. Thermal diffusivity

B. Thermal conductivity

C. Heat transfer co-efficient

D. Heat flux
168. Kg of liquid evaporated per hour in an evaporator is defined as its_________________?
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A. Capacity

B. Economy

C. None of these

D. Steam load

169. 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_______________?
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A. 0.4

B. 0.2

C. 0.6

D. 0.8

170. Terminal point temperature differences between fluids in case of a heat exchanger is termed as__________________?
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A. Approach

B. Log mean temperature difference

C. Arithmetic mean temperature difference

D. Geometric mean temperature difference

171. With increase in temperature, the thermal conductivity of fresh lubricating oil ___________________?
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A. May increase or decrease; depends on its composition

B. Decreases

C. Remains unchanged

D. Increases

172. The Stefan-Boltzmann constant depends on the_________________?
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A. Medium

B. Surface

C. None of these

D. Temperature

173. To reduce the tube side pressure drop for the same flow rate, the heat exchanger recommended is _______________?
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A. 1-1 heat exchanger

B. 3-2 heat exchanger

C. 1-2 heat exchanger

D. 2-4 heat exchanger

174. Fruit juice (a heat sensitive material) can be concentrated in a ____________ evaporator?
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A. Falling film

B. Long tube

C. None of these

D. High pressure

175. Evaporation by thermo compression results in the _________________________?
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A. Saving of steam

B. Realisation of multiple effect economy in a single effect

C. Both A. and B.

D. None of these

176. It is not preferable to use superheated steam in evaporators, because of its very_________________?
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A. High pressure

B. High temperature

C. None of these

D. Low film co-efficient
177. The left face of a one dimensional slab of thickness 0.2 m is maintained at 80C and the right face is exposed to air at 30C. The thermal conductivity of the slab is 1.2 W/m.K and the heat transfer co-efficient from the right face is 10 W/m2.K. At steady state, the temperature of the right face in C is____________________?
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A. 77.2

B. 71.2

C. 63.8

D. 48.7
178. Boiling point elevation for a strong and concentrated solution is found by Duhrings rule, which states that at the same pressure, the boiling point of a solution is a linear function of the _______________ of pure water?
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A. Kinematic viscosity

B. Boiling point

C. Dynamic viscosity

D. Density

179. The variation of thermal conductivity of a metal with temperature is often correlated using an expression of the form K = K0 + at, where, K is the thermal conductivity and T is the temperature (in K). The units of a in SI system will be________________?
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A. W/m

B. None, a is just a number

C. W/m.k

D. W/m.k2
180. A wall has two layers of materials A and B; each made of a different material. Both the layers have the same thickness. The thermal conductivity of material A is twice that of B. Under the equilibrium, the temperature difference across the wall is 36C. The temperature difference across the layer A is ______________ C?
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A. 24

B. 18

C. 6

D. 12