Both the tube sheets fixed
Both the tube sheets floating
The top tube sheet floating and bottom tube sheet fixed
The top tube sheet fixed and the bottom tube-sheet floating
✅ The correct answer is option A.
Heat Transfer MCQs
412. Critical value of the __________ number governs the transition from laminar to turbulent flow in free convection heat transfer.
Grashoff
Reynolds
Both A & B
Prandtl & Grashoff
✅ The correct answer is option D.
413. What is the absorptivity of a black body?
1
0
0.78
0.95
✅ The correct answer is option A.
414. Kg of liquid evaporated per hour in an evaporator is defined as its
Capacity
Economy
Steam load
None of these
✅ The correct answer is option A.
415. In a heat exchanger, the rate of heat transfer from the hot fluid to the cold fluid
Varies directly as the area and the LMTD
Directly proportional to LMTD and inversely proportional to the area
Varies as square of the area
None of these
✅ The correct answer is option A.
416. Nusselt number is a function of Prandtl number and __________ number of fluid in natural convection heat transfer.
Grashoff
Biot
Stantan
Reynolds
✅ The correct answer is option A.
417. The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by
Painting the surface black
Painting the surface white (with aluminium paint)
Giving the surface a mirror finish
Roughening the surface
✅ The correct answer is option B.
418. For a perfectly transparent surface (like gases), the
Absorptivity = 0
Transmissivity = 1
Reflectivity = 0
All of the above
✅ The correct answer is option B.
419. Graetz number is given by
mCp/kL
kL/mCp
mCp/kμ
kμ/mCp
✅ The correct answer is option A.
420. Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.
Laminar
Transition
Both A & B
Highly turbulent
✅ The correct answer is option D.