Related Mcqs:

1. Extended heat transfer surface like fins are used to increase the heat transfer rate. Fin efficiency is defined as the ratio of heat transferred across the fin surface to the theoretical heat transfer across an equal area held at the________________?

   A. Surrounding temperature
   B. Average temperature of the fin
   C. Temperature of the fin end
   D. Constant temperature equal to that of the base

2. In case of heat transfer by conduction in a hollow cylinder, ______________ mean area is used to calculate the heat transfer rate?

   A. Geometric
   B. Arithmetic
   C. Logarithmic
   D. Either A., B. or C.

3. 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

4. Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is ____________________?

   A. Thin walled having the value of Ao Ai/< 2
   B. Thick walled
   C. Having the value of Ao/Ai > 2
   D. Both B. and C.

5. Fouling factor for a heat exchanger is given by (where, U1 = heat transfer co-efficient of dirty surface U2 = heat transfer co-efficient of clean surface) ?

   A. U1 – U2
   B. 1/U1 – 1/U2
   C. 1/U2 – 1/U1
   D. U2 – U1

6. The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m2.K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m2.K. The overall heat transfer co-efficient at this time is _____________________?

   A. 1200 W/m2.K
   B. 894 W/m2.K
   C. 333 W/m2.K
   D. 287 W/m2.K

7. For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area___________________?

   A. Increases
   B. Decreases
   C. Remain constant
   D. Passes through a maxima

8. Air is to be heated by condensing steam. Two heat exchangers are available (i) a shell and tube heat exchanger and (ii) a finned tube heat exchanger. Tube side heat transfer area are equal in both the cases. The recommended arrangement is________________?

   A. Finned tube heat exchanger with air inside and steam outside
   B. Finned tube heat exchanger with air outside and steam inside
   C. Shell and tube heat exchanger with air inside tubes and steam on shell side
   D. Shell and tube heat exchanger with air on shell side and steam inside tubes

9. 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

10. Value of Nusselt number [Nu = (hD/k)] for the heat transfer by conduction from a droplet or a spherical particle to a surrounding stagnant film is__________________?

    A. 0.5
    B. 2
    C. 10
    D. 100