1578. Heat transfer occurs by natural convection because change in temperature causes difference in
Viscosity
Density
Thermal conductivity
Heat capacity
✅ The correct answer is option B.
1581. Pick out the correct equation.
JH = (St)(Pr)2/3 = f/2
JH = (St)(Pr)1/3 = f/2
JH = (St)2/3(Pr) = f/2
JH = (St)1/3(Pr) = f/2
✅ The correct answer is option A.
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.
1555. Which of the following has the lowest overall heat transfer co-efficient?
Dowtherm
Molten sodium
Water
Air
✅ The correct answer is option D.
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.
1526. 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.
1528. 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.
1530. 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.
1532. The rate of heat transfer is a product of overall heat transfer co-efficient, the difference in temperature and the
Heating volume
Heat transfer area
Nusselt number
None of these
✅ The correct answer is option B.