chemical engineering MCQs – Page 205

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 Review each marked answer and report any item that may be outdated or unclear.

chemical engineering Mcqs

4081. While the total emissivity of a perfect black body is unity, the same for a real body is__________________?
0

A. 0

B. > 1

C. Between 0 and 1

D. 1

4082. Three materials A, B and C of equal thickness and of thermal conductivity of 20, 40 & 60 kcal/hr. m. C respectively are joined together. The temperature outside of A and C are 30C and 100C respectively. The interface between B and C will be at a temperature of ____________ C?
0

A. 50

B. 40

C. 95

D. 70

4083. For specified tube outside diameter, higher BWG means higher___________________?
0

A. Cross-sectional area

B. Tube thickness

C. Weight per unit length

D. None of these

4084. Prandtl number is the ratio of________________?
0

A. Thermal diffusivity to mass diffusivity

B. Thermal diffusivity to momentum diffusivity

C. Momentum diffusivity to thermal diffusivity

D. Momentum diffusivity to mass diffusivity

4085. Multiple effect evaporators ar used to___________________?
0

A. Increase the steam economy & the capacity

B. Decrease the steam economy & increase the capacity

C. Increase the steam economy & decrease the capacity

D. Decrease the steam economy & the capacity

4086. Prandtl and Reynolds analogies are identical for Prandtl number value of__________________?
0

A. 0

B. 0.5

C. 5

D. 1

4087. Prandtl number is the reciprocal of____________________?
0

A. Thermal diffusivity/Momentum diffusivity

B. Mass diffusivity Momentum diffusivity

C. Thermal diffusivity Momentum

D. Thermal diffusivity Mass diffusivity

4088. The radiation heat flux from a heating element at a temperature of 800C, in a furnace maintained at 300C is 8 kW/m2. The flux, when the element temperature is increased to 1000C for the same furnace temperature is_____________________?
0

A. 12.0 kW/m2

B. 14.6 kW/m2

C. 11.2 kW/m2

D. 16.5 kW/m2

4089. In the free convection regime of pool boiling, the heat flux is proportional to__________________?
0

A. ?t2

B. ?t5/4

C. ?t

D. ?t1/2

4090. A steel sphere of radius 0.1 m at 400K is immersed in an oil at 300K. If the centre of the sphere reaches 350K in 20 minutes, how long will it take for a 0.05 m radius steel sphere to reach the same temperature (at the centre) under identical conditions? Assume that the conductive heat transfer co-efficient is infinitely large ?
0

A. 20 minutes

B. 5 minutes

C. 10 minutes

D. 40 minutes

4091. Double pipe heat exchangers are used__________________?
0

A. When heat transfer area required is very low, i.e. (100-200 ft2).

B. Because it is less costly

C. Because it occupies less floor area

D. When heat transfer area required is very high

4092. Film boiling is usually not desired in commercial equipments, because____________________?
0

A. None of these

B. It is difficult to maintain

C. The heat transfer rate is low in view of the large temperature drop

D. It is not economic

4093. In case of a shell and tube heat exchanger, the minimum and maximum baffle spacing is respectively (where, D = inside diameter of the shell) ?
0

A. D/4 and 2 D

B. D/5 and D

C. D/2 and 2 D

D. D and 2 D

4094. Heat exchanger tubes are never made of_________________?
0

A. Copper

B. Plain carbon steel

C. Lead

D. Stainless steel

4095. Shell side pressure drop in a shell and tube heat exchanger does not depend upon the_________________?
0

A. None of these

B. Baffle spacing & shell diameter

C. Viscosity, density & mass velocity of shell side fluid

D. Tube diameter & pitch

4096. The purpose of providing bleed points in the evaporator is to__________________?
0

A. Remove the product

B. Admit the feed

C. Facilitate removal of non-condensable gases

D. Create vacuum

4097. The main purpose of providing fins on heat transfer surface is to increase the_________________?
0

A. Heat transfer co-efficient

B. Mechanical strength of the equipment

C. Temperature gradient

D. Heat transfer area

4098. The unit of heat transfer co-efficient is_________________?
0

A. BTU/hr. F. ft

B. BTU/hr. F

C. BTU/hr. ft

D. BTU/hr. ft2F

4099. What is the absorptivity of a black body?
0

A. 0.95

B. 1

C. 0

D. 0.78

4100. In a multiple effect evaporator, the effect of boiling point elevation is to______________________?
0

A. Reduce the economy

B. Reduce the capacity

C. Increase the economy

D. None of these

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