71. Forced circulation evaporators are normally used for concentrating liquids having
Scaling characteristics
High viscosity
Both A & B
Neither A nor B
✅ The correct answer is option C.
Heat Transfer MCQs
72. Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is
Finned tube heat exchanger with air inside and steam outside
Finned tube heat exchanger with air outside and steam inside
Shell and tube heat exchanger with air inside tubes and steam on shell side
Shell and tube heat exchanger with air on shell side and steam inside tubes
✅ The correct answer is option B.
73. Natural convection is characterised by
Grashhoff number
Peclet number
Reynolds number
Prandtl number
✅ The correct answer is option A.
74. Radiation heat transfer rates does not depend upon the
Type of absorbing surface
Distance between the heat source and the object receiving the heat
Surface area and temperature of the heat source
None of these
✅ The correct answer is option D.
75. A multiple effect evaporator as compared to a single effect evaporator of the same capacity has
Lower heat transfer area
Lower steam economy
Higher steam economy
Higher solute concentration in the product
✅ The correct answer is option C.
76. In a shell and tube heat exchanger, square pitch compared to triangular pitch
Gives a higher shell side pressure drop
Gives a lower shell side pressure drop
Can pack more surface area into a shell of given diameter
None of these
✅ The correct answer is option A.
77. For an ideal black body
Absorptivity = 1
Reflectivity = 1
Emissivity = 0
Transmissivity = 1
✅ The correct answer is option A.
78. The driving potential for the crystal growth during crystallisation is the __________ of the solution.
Concentration
Viscosity
Super-saturation
Density
✅ The correct answer is option C.
79. Calburn analogy is applicable for the value of Prandtl number from
0.001 to 1
0.6 to 120
0.5 to 5
120 to 400
✅ The correct answer is option B.
80. A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m².°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be
Greater than that for uninsulated steam pipe
Less than that of the uninsulated steam pipe
Equal to that of the uninsulated steam pipe
Less than the steam pipe with 5 cms insulation
✅ The correct answer is option B.