311. Nusselt number is the ratio of the temperature gradient at the wall to
Temperature difference
Heat flux
That across the entire pipe
None of these
✅ The correct answer is option C.
Heat Transfer MCQs
312. Overall heat transfer co-efficient for cooling of hydrocarbons by water is about
50 -100 Kcal/hr.m².°C
50 -100 W/m² . °K
50 -100 BTU/hr. ft.2°F
1000 – 1500 BTU/hr. ft.2°F
✅ The correct answer is option C.
313. Film boiling is usually not desired in commercial equipments, because
The heat transfer rate is low in view of the large temperature drop
It is difficult to maintain
It is not economic
None of these
✅ The correct answer is option A.
314. Correction is applied to LMTD for __________ flow.
Parallel
Counter
Cross
None of these
✅ The correct answer is option C.
315. In case of a vertical tube evaporator, with increase in the liquor level, the __________ is increased.
Velocity of circulation
Liquor-film co-efficient
Both A and B
Neither A and B
✅ The correct answer is option D.
316. A process stream of dilute aqueous solution flowing at the rate of10 Kg.s⁻¹ is to be heated. Steam condensate at 95°C is available for heating purpose, also at a rate of 10 Kg.s⁻¹. A 1 – 1 shell and tube heat exchanger is available. The best arrangement is
Counter flow with process stream on shell side
Counter flow with process stream on tube side
Parallel flow with process stream on shell side
Parallel flow with process stream on tube side
✅ The correct answer is option A.
317. For a counter current heat exchanger with Tih = 80°C, T°c = 60°C, T°h = 50°C and Tic = 30°C, and the temperature difference between the two streams being the same everywhere along Z, the direction of flow of hot fluid. The temperature profile should satisfy
d²T/dZ² > 0
d²T/dZ² = 0
d²T/dZ² < 0
dT/dZ = 0
✅ The correct answer is option B.
318. A black body does not __________ radiation.
Absorb or emit
Refract
Reflect
Both B & C
✅ The correct answer is option D.
319. Stefen’s block body radiation law can also be derived from __________ law.
Kirchoffs
Planck’s
Fourier’s
None of these
✅ The correct answer is option B.
320. What is the geometric mean of two heat transfer areas A₁ and A₂ ?
√(A₁ . A₂)
√(A₁ + A₂)
1/2 √(A₁ . A₂)
2 √(A₁ . A₂)
✅ The correct answer is option A.