1551. Which of the following has the lowest Prandtl number?
Molten sodium (a coolant used in fast breeder reactor)
Water
Transformer oil
Dilute H₂SO₄
✅ The correct answer is option A.
Chemical Engineering
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1552. Reynold’s analogy states that (where, St = Stanton number f = friction factor)
St = f/2
St = f/4
St = 4f
St = f1/2
✅ The correct answer is option A.
1553. 1000 Kg of liquid at 30°C in a well stirred vessel has to be heated to 120°C, using immersed coils carrying condensing steam at 150°C. The area of the steam coils is 1.2 m² and the overall heat transfer co-efficient to the liquid is 1500 W/m².°C. Assuming negligible heat loss to the surrounding and specific heat capacity of the liquid to be 4 kJ/kg.°C, the time taken for the liquid to reach desired temperature will be
15 min
22 min
44 min
51 min
✅ The correct answer is option D.
1554. Heat transfer in the laminar sublayer in case of a liquid flowing through a pipe, is mostly by
Eddies current
Conduction
Convection
None of these
✅ The correct answer is option B.
1555. Which of the following has the lowest overall heat transfer co-efficient?
Dowtherm
Molten sodium
Water
Air
✅ The correct answer is option D.
1556. Which of the following forced convection heat transfer equation accounts for the liquid viscosity effect for viscous liquids?
Dittus-Boeltier equation
Sieder-Tate equation
Nusselt equation
None of these
✅ The correct answer is option B.
1557. 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.
1558. 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.
1559. 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.
1560. Correction is applied to LMTD for __________ flow.
Parallel
Counter
Cross
None of these
✅ The correct answer is option C.