1
< 1
> 1
None of these
✅ The correct answer is option A.
Heat Transfer MCQs
Three solid objects of the same material and of equal mass-a sphere, a cylinder (length = diameter) and a cube are at 500°C initially. These are dropped in a quenching bath containing a large volume of cooling oil each attaining the bath temperature eventually. The time required for 90% change in temperature is the smallest for
Cube
Cylinder
Sphere
Equal for all the three
✅ The correct answer is option A.
Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer can not take place
Between two bodies in physical contact with each other
Between two bodies not in physical contact with each other
From one part of a body to the another part of the same body
Both B & C
✅ The correct answer is option B.
The heat flux in the nucleate boiling regimes is proportional to (where, ΔT = excess temperature)
(ΔT)²
(ΔT)⁴
(ΔT)³
√(ΔT)
✅ The correct answer is option C.
Thermal diffusivity of a material
Has the unit m² /sec
Is defined as K/ρ . Cp
Is the ratio of thermal conductivity to thermal capacity
All of the above
✅ The correct answer is option D.
What is the unit of thermal conductivity ?
Kcal/hr. m² °C
Kcal/hr.m.°C
Kcal/hr.m
Kcal/hr. °C
✅ The correct answer is option B.
In a forward feed multiple effect evaporator unit
Viscosity of liquid is highest in first effect
Transfer from effect to effect is done by pumps
No pump is required to withdraw the product from the last effect
None of these
✅ The correct answer is option D.
Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the
Surrounding temperature
Average temperature of the fin
Temperature of the fin end
Constant temperature equal to that of the base
✅ The correct answer is option D.
In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is
Infinity
Zero
Same as average heat transfer co-efficient for tube side
None of these
✅ The correct answer is option A.
In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to __________ the velocity head.
Twice
Four times
Square root of
Square of
✅ The correct answer is option B.