Heat Transfer Conduction Chemical Engineering MCQ - Set 27 - ObjectiveBooks

# Practice Test: Question Set - 27

1. The heat transfer by radiation from a mild steel surface is to be reduced by reducing the emissivity of the surface. This can be best achieved by
(A) Painting the surface black
(B) Painting the surface white (with aluminium paint)
(C) Giving the surface a mirror finish
(D) Roughening the surface

2. In a heat exchanger, one transfer unit means
(A) A section of the exchanger in which change in temperature of one stream equals the average driving force in the section
(B) The size of the exchanger in which heat transfer rate is 1 kcal/hr
(C) Both (a) and (b)
(D) None of these

3. Heat produced when a steady state current, I passes through an electrical conductor having resistance, 'R' is
(A) IR
(B) I2R
(C) IR2
(D) I2R2

4. A 2-4 heat exchanger involves
(A) Only counter-flow of fluids
(B) Only parallel-flow of fluids
(C) Both counter and parallel-flow of the fluids
(D) Smaller pressure drop compared to 1-2 exchanger

5. In a multipass shell and tube heat exchanger, tube side return pressure loss is equal to __________ the velocity head.
(A) Twice
(B) Four times
(C) Square root of
(D) Square of

6. In a shell and tube heat exchanger, the height of 25 percent cut baffles is equal to (where, D = inside diameter of shell).
(A) 0.25 D
(B) 0.50 D
(C) 0.75 D
(D) None of these

7. The heat flux (from outside to inside) across an insulating wall with thermal conductivity, K = 0.04 W/m.°K and thickness 0.16m is 10 W/m2. The temperature of the inside wall is - 5°C. The outside wall temperature is
(A) 25°C
(B) 30°C
(C) 35°C
(D) 40°C

8. Latent heat absorbed by 1 lb of water at 212°F, when it is changed to steam at 212°F, may be around __________ BTU.
(A) 180
(B) 970
(C) 3.97
(D) None of these

9. Dittus-Boelter equation cannot be used for molten metals mainly due to its very low
(A) Prandtl number
(B) Grashoff number
(C) Thermal conductivity
(D) Viscosity

10. Baffle spacing
(A) Is not the same as baffle pitch
(B) Should be less than one fifth the diameter of the shell
(C) Should be less than the inside diameter of the shell
(D) None of these

11. Steam consumption in kg/hr in case of an evaporator is given by (where, C & E are capacity the economy of the evaporator respectively).
(A) C/E
(B) E/C
(C) CE
(D) 1/CE

12. The local surface conductance for laminar film condensation on vertical surface is (where, t = film thickness)
(A)  t
(B)  1/t
(C)  √t
(D) Independent of 't'

13. Which of the following is unimportant in forced convection?
(A) Reynolds number
(B) Prandtl number
(C) Grashoff number
(D) None of these

14. The purpose of floating head in a heat exchanger is to
(A) Avoid buckling of tubes
(B) Provide support for tubes
(C) Decrease the pressure drop
(D) Facilitate its lengthening, if needed

15. Convective heat transfer co-efficient in case of fluid flowing in tubes is not affected by the tube length/diameter ratio, if the flow is in the __________ zone.
(A) Laminar
(B) Transition
(C) Both 'a' & 'b'
(D) Highly turbulent

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