Chemical Engineering Quiz 1




Chemical Engineering Quiz




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1. Fourier’s Law described heat transfer by
  • (a)conduction
  • (b)convection
  • (c)radiation
  • (d)all



2. The equation is known as
  • (a)Reynolds equation
  • (b) Prandtl equation
  • (c)Van’t Hoff’s general equation
  • (d)Fourier’s general equation


3. In SI system the unit of thermal conductivity is
  • (a)W/ m2. K
  • (b)W/m.K
  • (c)W/K
  • (d)W/m2


4. Flow is proportional to
  • (a) potential X resistance
  • (b)potential/conductance
  • (c)potential X conductance
  • (d)none of the above


5. Heat flows by conduction through a rod 1 m long and having a cross-sectional area of 10 cm2. The thermal
conductivity of the rod material is K W/m.K. The thermal resistance for the process is
  • (a)1000/K
  • (b)K/1000
  • (c) 1000 * K
  • (d)none of the above


6. Thermal conductivity of a material is defined as
  • (a)the resistance to heat transfer for a quantity of material 1 m thick with heat flow area 1 m2, time unit 1 hr and temperature difference 1K
  • (b) the conductance for a quantity of material 1 m thick with heat flow area 1 m2, time unit 1 sec and temperature difference 1 K
  • (c)the resistance to heat transfer for a quantity of material 1 m thick with heat flow area 100 m2, time unit 1 sec and temperature difference 100 K.
  • (d)none of the above


7. For heat transfer through a composite wall, overall resistance to heat transfer is
  • (a) sum of the resistance
  • (b)product of the resistance
  • (c) a ratio of (sum of the resistances)/(product of the resistances)
  • (d)(sum of the resistances) + (product of the resistances)


8. For a body with very high thermal conductivity,
  • (a)heat transfer will be very rapid
  • (b) heat transfer will be very slow
  • (c)there will be no heat transfer at all
  • (d)none of the above is true


9. An insulator should have
  • (a)very high thermal conductivity
  • (b)very high thermal diffusivity
  • (c)very low thermal conductivity
  • (d)none of the above


10. Air is
  • (a) an excellent heat conductor
  • (b) a poor heat conductor
  • (c) is a better heat conductor than steel
  • (d) none of these


11.Thermal diffusivity is defined as
  • (a)K Cp/ρ
  • (b) K ρ/Cp
  • (c)K /ρCp
  • (d)K ρCp


12. Grashof number is important in
  • (a)heat conduction
  • (b)forced convection
  • (c) natural convection
  • (d)radiative heat transfer


13. For free convection heat transfer, Nusselt number depends on
  • (a)Reynolds number and Prandtl number
  • (b)Reynolds number, Prandtl number and Grashof number
  • (c)Reynolds number and Grashof number
  • (d) Grashof number and Prandtl number


14. Brinkman number” is important in problems related to
  • (a)heat conduction with a nuclear heat source
  • (b) heat conduction with a viscous heat source
  • (c)heat conduction with a chemical heat source
  • (d)heat conduction with an electric heat source


15. Nusselt number for forced convection heat transfer in pipe of diameter D is defined as
  • (a)h D/K
  • (b)h K/D
  • (c) K D/h
  • (d)K D/h2


16. When the ratio of Grashof number to the square of the Reynolds number is unity, the dominant mechanism for heat transfer is
  • (a) Free convection
  • (b)Entry length problem in laminar forced convection ( developing thermal boundary layer)
  • (c)Mixed convection( both free and forced)
  • (d)Forced convection


17. A small metal ball at 30oC is placed in a hot liquid (taken in a vessel) at 150oC. The liquid is stirred slowly and liquid volume is much larger compared to the ball volume. Without any other numerical data what can you say about the Biot number ?
  • (a) Biot number will be large
  • (b)Biot number will be small
  • (c)Nothing can be said about the Biot number ; data required for even crude prediction
  • (d)Biot number will be constant


18. Colburn J. factor for heat transfer is given by
  • (a) St. Pr (µw/µ)0.14
  • (b)St 2/3. Pr
  • (c)St. Pr 2/3 w/µ)0.14
  • (d) (St. Pr)2/3


19. Greatz number is important in problem related to
  • (a)heat transfer in a well-agitated vessel
  • (b)heat transfer in laminar tube flow
  • (c)heat transfer in turbulent flow in pipes
  • (d)both (a) and (c)


20. For heat transfer in tube flow Graetz number and Fourier number are related by equation
  • (a) NGZ. NFO = JH
  • (b)NGZ . NFO = (π)1/2
  • (c)NGZ .NFO = NRe
  • (d)NGZ .NFO = ρ




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Correct answers:



Important Dimensionless Number in chemical engineering

1. Sherwood Number (Sh) =kcL/DAB equivalent to Nussett Number (Nu) in Heat transfer
Nu= hd/k = conductive resistance of fluid / convective resistance
In Unsteady heat transfer Biot number is used.
Bi= hd/k = conductive resistance of solid / convective resistance

2. Schmidt Number (Sc) = μ/ρDAB = ratio of momentum diffusivity and mass diffusivity
Similarly in H.T.
Pr = CP µ/k = ratio of momentum diffusivity and thermal diffusivity

3. Peclet Number = Re.Pr in heat transfer
= Re.Sc in mass transfer
It is related to degree of mixing and is inversely proportional to dispersion number

4. Lewis Number = Sc/Pr
It is important where both heat and mass transfer take place together like humidification

5. In natural convection
Grashoff number= gβθL3 ρ 2 / μ 2
Raleigh number Ra = Gr.Pr

6. Stanton number
St (M.T.) = Sh/(Sc.Re)
St (H.T.) = Nu/(Pr.Re)

7. Unsteady state heat transfer
Fourier number = αt/L2
Bi=hd/k

8. Graetz Number = Re.Pr.(d/L)

9. In agitation there are
Power number = P/ρN3D5
Froude number = N2D/g
Re=ρND2

10. In centrifugal pumps
Power constant
Capacity constant
Head constant

GATE 2010 Answer Key of Chemical Engineering

1 D 2 A 3 B 4 D 5 B 6 B 7 B 10 D 11 C 12 C
13 C 14 D 15 A 16 D 17 C 18 A 19 D 20 D 21 A 22 D
26 D 27 D 29 B 30 C 31 A 32 C 33 D 36 A 37 A 40 A
41 A 43 D 47 A 48 D 49 B 50 B 51 D 52 A 53 A 54 B
55 C 56 B 57 B 58 D 59 D 64 D