Graetz number is given by__________________?

Related Mcqs:

1. The Graetz number is concerned with the___________________

   A. Mass transfer between a gas and a liquid
   B. Absorption with chemical reaction
   C. Heat transfer in turbulent flow
   D. Heat transfer in laminar flow

2. Prandtl number is given by__________________?

   A. CP μ/a
   B. hD/k
   C. CP μ/k
   D. μ/h CP

3. Thermal diffusivity is given by__________________?

   A. k/ρCp
   B. ρCp/k
   C. μCp/a
   D. μ/hCp

4. 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]

5. In pipe flow, heat is transferred from hot wall to the liquid by__________________?

   A. Conduction only
   B. Forced convection only
   C. Forced convection and conduction
   D. Free and forced convection

6. Natural convection is characterised by__________________?

   A. Grashoff number
   B. Peclet number
   C. Reynolds number
   D. Prandtl number

7. Fourier’s law applies to the heat transfer by__________________?

   A. Convection
   B. Radiation
   C. Conduction
   D. All A., B. & C.

8. 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

9. Heat transfer in the laminar sub-layer in case of a liquid flowing through a pipe, is mostly by__________________?

   A. Eddies current
   B. Conduction
   C. Convection
   D. None of these

10. Thermal diffusivity is the most important in heat transfer by__________________?

    A. Conduction
    B. Radiation
    C. Condensation
    D. Natural convection