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.Management Sciences
Category: Chemical Heat Transfer
Critical value of the _____________ number governs the transition from laminar to turbulent flow in free convection heat transfer?
A. Grashoff
B. Reynolds
C. Both ‘a’ & ‘b’
D. Prandtl & Grashoff
The rate of heat transfer through a pipe wall is given by, q = 2π k (Ti – T0)/ln (ri/r0). For cylinder of very thin wall, q can be approximated by__________________?
A. q = [2π k (Ti + T0)/2]/ln (ri/r0)
B. q = 2π ri k (Ti – T0)/(r0/ri)
C. q = 2π k (Ti – T0)/(r0/ri)
D. q = 2π k (Ti – T0)/[(r0 + ri)/2]
Economy of a multiple effect evaporator is not influenced much by the_______________________?
A. Boiling point elevations
B. Temperature of the feed
C. Rate of heat transfer
D. Ratio of the weight of the thin liquor to thick liquor
Circulation pump is located below the evaporator to___________________?
A. Avoid cavitation
B. Avoid frequent priming
C. Create more suction head
D. None of these
Which of the following is not used as a medium for high temperature heating ?
A. Dowtherm
B. Mercury
C. Liquid metal (e.g. molten sodium)
D. Fused salts (e.g., an eutectic mixture of 53% KNO3, 40% NaNO2and 7% NaNO3)
_____________ heat exchanger is the most suitable, when the temperature of shell side fluid is much higher than that of tube side?
A. Single pass, fixed tube sheet
B. U-tube
C. Three pass, fixed tube sheet
D. None of these
In a 1-1 concurrent heat exchanger, if the tube side fluid outlet temperature is equal to the shell side fluid outlet temperature, then the LMTD is_________________?
A. ∞
B. 0
C. Equal to the difference between hot and cold fluids inlet temperature
D. Equal to the difference between hot fluid inlet temperature and cold fluid outlet temperature
If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor?
A. Increase
B. Decrease
C. Not affect
D. Increase the condensing film co-efficient as well as
For a counter current heat exchanger with Ti h = 80°C, T°c = 60°C, T°h = 50°C and Ti c = 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___________________?
A. d2T/dZ2 > 0
B. d2T/dZ2 = 0
C. d2T/dZ2 < 0
D. dT/dZ = 0
Reynold’s analogy states that (where, St = Stanton number f = friction factor) ?
A. St = f/2
B. St = f/4
C. St = 4f
D. St = f1/2
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