25°C
30°C
35°C
40°C
✅ The correct answer is option C.
Heat Transfer MCQs
162. The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoffs law.
Wavelength of radiation
Nature of the body
Temperature of the body
None of these
✅ The correct answer is option C.
163. Grashhoff number is given by
gD³.β.Δtρ²/μ²
gD2βΔtρ/μ²
gD2βΔtP²μ
gD³βΔtP²/μ
✅ The correct answer is option A.
164. For what value of Prandtl number, the Col-burn analogy is valid?
0.06 to 120
0.6 to 120
1 to 103
L to 50
✅ The correct answer is option B.
165. While the total emissivity of a perfect black body is unity, the same for a real body is
0
1
> 1
Between 0 and 1
✅ The correct answer is option D.
166. In a shell and tube heat exchanger, floating head is used for
Large temperature differentials
High heat transfer co-efficient
Low pressure drop
Less corrosion of tubes
✅ The correct answer is option A.
167. Kirchoff s law applies to __________ radiation.
Total
Monochromatic
Both A & B
Neither A nor B
✅ The correct answer is option C.
168. Which is the most suitable for the concentration of foamy & frothy liquors?
Agitated film evaporator
Long tube vertical evaporator
Open pan evaporator
None of these
✅ The correct answer is option B.
169. Convective heat transfer, in which heat is transferred by movement of warmed matter is described by
Fourier’s law
Newton’s law of cooling
Fick’s law
None of these
✅ The correct answer is option B.
170. Value of Prandtl number for water ranges from
L to 2
5 to 10
100 to 500
1000 to 2000
✅ The correct answer is option B.