Chemical Sterilization Heat Transfer MCQ - Set 04 - ObjectiveBooks

# Practice Test: Question Set - 04

1. LMTD can't be used as such without a correction factor for the
(A) Multipass heat exchanger
(B) Baffled heat exchanger
(C) Condensation of mixed vapor in a condenser
(D) All (a) (b) and (c)

2. What is the logarithmic mean of r1 and r2?
(A) (r1 - r2)/ln(r1/r2)
(B) (r1 - r2)/ln(r2/r1)
(C) (r2 - r1)/ln(r1/r2)
(D) (r1 - r2)/-ln(r1/r2)

3. In a heat exchanger with steam outside the tubes, a liquid gets heated to 45°C, when its flow velocity in the tubes is 2 m/s. If the flow velocity is reduced to 1 m/s, other things remaining the same, the temperature of the exit liquid will be
(A) Less than 45°C
(B) More than 45°C
(C) Equal to 45°C
(D) Initially decreases and remains constant thereafter

4. The Nusselt number for fully developed (both thermally and hydrodynamically) laminar flow through a circular pipe, where the wall heat flux is constant, is
(A) 2.36
(B) 4.36
(C) 120.36
(D) Dependent on NRe only

5. Heat flux, as defined in heat flow is analogous to __________ in electricity flow.
(A) Current
(B) Voltage
(C) Resistance
(D) None of these

6. The overall resistance for heat transfer through a series of flat resistance, is the __________ of the resistances.
(A) Average
(B) Geometric mean
(C) Product
(D) Sum

7. The driving potential for the crystal growth during crystallization is the __________ of the solution.
(A) Concentration
(B) Viscosity
(C) Super-saturation
(D) Density

8. Heat transfer co-efficient equation for forced convection, Nu = 0.023 Re0.8Prn, is not valid, if the value of
(A) n = 0.4 is used for heating
(B) n = 0.3 is used for cooling
(C) Reynolds number for the flow involved is > 10000
(D) Reynolds number for the flow involved is < 2100

9. For flow over a flat plate, the ratio of thermal boundary layer thickness, 'xt' and hydrodynamic boundary layer thickness 'x' is equal to (where, NPr = Prandtl number)
(A) NPr
(B) NPr1/3
(C) NPr-1
(D) NPr-1/3

10. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass __________ through the heat exchanger.
(A) Once
(B) Twice
(C) Thrice
(D) Four times

11. An ejector is used to
(A) Increase pressure
(B) Increase temperature
(C) Remove condensate
(D) None of these

12. In a forward feed multiple effect evaporator, the pressure is
(A) Highest in last effect
(B) Lowest in last effect
(C) Same in all effects
(D) Dependent on the number of effects

13. In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is
(A) 2000
(B) 4000
(C) 5000
(D) 6000

14. With increase in temperature, the thermal conductivity of most liquids
(A) Increases
(B) Decreases
(C) Remain same
(D) First increases upto a certain temperature and then becomes constant

15. Peclet number (Pe) is given by
(A) Pe = Re.Pr
(B) Pe = Re/Pr
(C) Pe = Pr/Re
(D) Pe = Nu.Re

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