At Pr > 1, conduction in an ordinary fluid flowing through a heated pipe is limited to the___________________?

Related Mcqs:

1. At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ?

   A. 0.5
   B. < 0.5
   C. > 0.6
   D. < 0.1

2. Heat transfer by conduction in the turbulent core of a fluid flowing through a heated pipe is negligible, if the value of Prandtl number is_______________?

   A. 0.2
   B. 0.4
   C. 0.6
   D. 0.8

3. Conduction occurs in the buffer zone for a fluid flowing through a heated pipe, only when Prandtl number is________________?

   A. 0.1
   B. > 1
   C. < 1
   D. 1

4. If average heat transfer co-efficient is ha and the local coefficient at the end of the plate is hl then in case of heat transfer to a fluid flowing over a flat plate, heated over its entire length________________?

   A. ha = hl
   B. ha = 2hl
   C. ha = 0.5 hl
   D. ha = 0.75 hl

5. At what value of Prandtl number, the hydrodynamic and thermal boundary layers of a fluid flowing over a heated plate will be identical ?

   A. 1
   B. 1
   D. None of these

6. Heat transfer by conduction results due to the transfer of free electrons, kinetic energy & vibrational energy from one molecule to another. Conduction heat transfer cannot take place____________________?

   A. Between two bodies in physical contact with each other
   B. Between two bodies not in physical contact with each other
   C. From one part of a body to the another part of the same body
   D. Both B & C

7. The characteristic dimensionless groups for heat transfer to a fluid flowing through a pipe in laminar flow are_______________?

   A. Re.Gz
   B. Nu, Pr
   C. Nu, Pr, Re
   D. Nu, Gz

8. Heat transfer co-efficient (h) for a fluid flowing inside a clean pipe is given by h = 0.023 (K/D) (DVρ/μ)0.8 (CP.μ/k)0.4. This is valid for the value of NRe equal to_______________?

   A. 4000
   D. > 10000

9. A fluid is flowing inside the inner tube of a double pipe heat exchanger with diameter ‘d’. For a fixed mass flow rate, the tube side heat transfer co-efficient for turbulent flow conditions is proportional to_____________________?

   A. d0.8
   B. d-0.2
   C. d-1
   D. d-1.8

10. A 10 cm dia steam pipe, carrying steam at 180°C, is covered with an insulation (conductivity = 0.6 W/m.°C). It losses heat to the surroundings at 30°C. Assume a heat transfer co-efficient of 0.8 W/m2.°C for heat transfer from surface to the surroundings. Neglect wall resistance of the pipe and film resistance of steam. If the insulation thickness is 2 cms, the rate of heat loss from this insulated pipe will be__________________?

    A. Greater than that for un-insulated steam pipe
    B. Less than that of the un-insulated steam pipe
    C. Equal to that of the un-insulated steam pipe
    D. Less than the steam pipe with 5 cms insulation