Film boiling occurs at ________________ pressure?

Related Mcqs:

1. Boiling point elevation for a strong and concentrated solution is found by Duhring’s rule, which states that at the same pressure, the boiling point of a solution is a linear function of the _______________ of pure water?

   A. Boiling point
   B. Dynamic viscosity
   C. Kinematic viscosity
   D. Density

2. In case of _______________ boiling, the liquid temperature is below the saturation temperature and the boiling takes place in the vicinity of the heated surface?

   A. Nucleate
   B. Local
   C. Pool
   D. Saturated

3. Boiling of milk in an open vessel is an example of ______________ boiling?

   A. Film
   B. Sub-cooled
   C. Saturated nucleate
   D. None of these

4. When vaporisation takes place through a blanketting film of gas, the phenomenon is termed as ___________________ boiling?

   A. Pool
   B. Nucleate
   C. Transition
   D. Film

5. Film boiling is usually not desired in commercial equipments, because____________________?

   A. The heat transfer rate is low in view of the large temperature drop
   B. It is difficult to maintain
   C. It is not economic
   D. None of these

6. The film co-efficient is decreased due to the presence of non-condensing gases in the vapors. The film co-efficient of superheated vapor as compared to that of saturated vapor is___________________?

   A. More
   B. Less
   C. Some
   D. Either more or less; depends on the nature of vapor

7. If h1 = inner film co-efficient and /h2 = outer film co-efficient, then the overall heat transfer co-efficient is________________?

   A. Always less than h1
   B. Always between h1 and h2
   C. Always higher than h2
   D. Dependent on metal resistance

8. 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’

9. The film thickness for laminar film condensation on vertical surface _____________ from top to bottom?

   A. Cumulatively increases
   B. Cumulatively decreases
   C. Remain constant
   D. And the surface conductance increase

10. In sub-cooled boiling ?

    A. Temperature of the heating surface is less than the boiling point of the liquid
    B. Temperature of the heating surface is more than the boiling point of the liquid
    C. Bubbles from heating surface are absorbed by the mass of the liquid
    D. Very large vapour space is necessary