In case of water (Prandtl number ≈ 6) flowing over a flat plate heated over the entire length, the thermal boundary layer thickness as compared to hydrodynamic boundary layer thickness is ?

Related Mcqs:

1. The laminar boundary layer thickness in zero pressure gradient flow over a flat plate along the x-direction varies as x0.5 while the thickness of turbulent boundary layer varies as (where, x = distance from the leading edge) ?

   A. x1.5
   B. x0.8
   C. x-1.5
   D. x-0.8

2. In a boundary layer developed along the flow, the pressure decreases in the downstream direction. The boundary layer thickness in this case will _______________?

   A. Decrease gradually
   B. Increase gradually
   C. Increase rapidly
   D. Remain constant

3. A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness ______________ metre?

   A. 0.01
   B. 0.1
   C. 0.25
   D. 0.5

4. A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is ________________ W/m2 °C ?

   A. 50
   B. 100
   C. 150
   D. 200

5. Temperature of hot gases flowing in a pipe is measured by a thermocouple inserted in the thermal well. The thermal well made of ______________ will facilitate the most accurate measurement of the temperature ?

   A. Copper
   B. Steel
   C. Aluminium
   D. Brass

6. Nusselt number is related to Grashoff number (Gr) in turbulent & laminar flow respectively, in respect of free convection over a vertical flat plate as_________________?

   A. Gr0.25, Gr
   B. Gr0.25, Gr0.33
   C. Gr, Gr0.25
   D. Gr0.33, Gr0.25

7. At the point of boundary layer separation in fluid flow, the _____________________?

   A. Shear stress is maximum
   B. Velocity gradient is flat
   C. Density variation is maximum
   D. Shear stress is zero

8. The expected efficiency of a single riveted lap joint is of the order of 50%. If the thickness of the plate is increased four times, then the rivet diameter will have to be increased ___________________ times ?

   A. Two
   B. Four
   C. Six
   D. Eight

9. During decarburising of a plain carbon steel, the thickness of ferrite layer growth is proportional to____________________?

   A. Time
   B. Square root of time
   C. Square of time
   D. Cube of time

10. One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is____________________?

    A. 100
    B. 900
    C. 9000
    D. 10000