Heat flow across a hollow sphere of inner radius ‘r1’ and outer radius ‘r2’ is directly proportional to__________________?

Related Mcqs:

1. Hollow shafts can be made as strong as solid shafts by making the twisting moments of both the shafts same. Shafts made by _____________ have residual stresses ?

   A. Forging
   B. Cold rolling
   C. Hot rolling
   D. Casting

2. Production of a hollow product by inflation of a tube or parison is called the _______________ process?

   A. Blow moulding
   B. Calendaring
   C. Extrusion
   D. Injection

3. Transition from laminar flow to turbulent flow in fluid flow through a pipe does not depend upon the___________________?

   A. Length of the pipe
   B. Diameter of the pipe
   C. Density of the fluid
   D. Velocity of the fluid

4. What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively ?

   A. 2
   B. 8
   C. 10
   D. 40

5. The pressure drop per unit length for laminar flow of fluid through a long pipe is proportional to (where, A = cross-sectional area of the pipe & D = Diameter of the pipe) ?

   A. A
   B. D
   C. 1/A
   D. 1/A2

6. Ferromagnetic materials owe their properties to __________________ inner sub-shells ?

   A. Completely filled
   B. Partially filled
   C. Equally filled
   D. Vacant

7. For the Stoke’s law to be valid in the case of a falling sphere in a fluid, the_____________________?

   A. Reynolds number (based on sphere diameter) should be < 1
   B. Flow around the sphere should be in turbulent region
   C. Sphere must be metallic
   D. Fluid density should be constant

8. The efficiency of a Carnot heat engine operating between absolute temperatures T1 and T2 (when, T1 > T2) is given by (T1 – T2)/T1. The co-efficient of performance (CO.P.) of a Carnot heat pump operating between T1 and T2 is given by_________________?

   A. T1/(T1-T2)
   B. T2/(T1-T2)
   C. T1/T2
   D. T2/T1

9. In a counter flow heat exchanger, hot fluid enters at 170°C & leaves at 150°C, while the cold fluid enters at 50°C & leaves at 70°C. The arithmetic mean temperature difference in this case is ______________ °C?

   A. 20
   B. 60
   C. 120
   D. ∞

10. Out of the following, maximum temperature drop for a given heat flow & for the same thickness will be in the case of________________?

    A. Steel
    B. Glass wood
    C. Copper
    D. Fireclay bricks