1671. Finned tube heat exchangers
Give larger area per tube
Use metal fins of low thermal conductivity
Facilitate very large temperature drop through tube wall
Are used for smaller heat load
✅ The correct answer is option A.
Chemical Engineering
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1672. Fluid motion in the natural convection heat transfer between a solid surface and a fluid in contact with it, results from the
Existence of thermal boundary layer
Temperature gradient produced due to density difference
Buoyancy of the bubbles produced at active nucleation site
None of these
✅ The correct answer is option D.
1673. Heat exchanger tubes are never made of
Plain carbon steel
Stainless steel
Lead
Copper
✅ The correct answer is option C.
1674. Heat transfer by natural convection is enhanced in system with
High viscosity
High co-efficient of thermal expansion
Low temperature gradients
Low density change with temperature
✅ The correct answer is option B.
1675. Prandtl and Reynold’s analogies are identical for Prandtl number value of
0
0.5
1
5
✅ The correct answer is option C.
1676. Boiling point elevation of a solution of NaOH
Increases rapidly with temperature rise
Is almost independent of temperature
Is almost independent of pressure
Both B and C
✅ The correct answer is option D.
1677. A __________ surface has the maximum thermal emissivity out of the following.
Black & smooth
Black & rough
White & smooth
White & rough
✅ The correct answer is option B.
1678. Economy of a multiple effect evaporator depends upon the
Heat balance consideration
Rate of heat transfer
Both A and B
Neither A nor B
✅ The correct answer is option A.
1679. Radiator of an automobile engine is a __________ type of heat exchanger.
Co-current
Cross-current
Counter-current
Direct contact
✅ The correct answer is option D.
1680. If heat transfer rate varies with the time, it is termed as
Forced convection
Steady state conduction
Monochromatic radiation
None of these
✅ The correct answer is option D.