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 _____________________?

Related Mcqs:

1. 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

2. Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is_____________?

   A. Vertical heat exchanger with steam on tube side
   B. Vertical heat exchanger with steam on shell side
   C. Horizontal heat exchanger with steam on tube side
   D. Horizontal heat exchanger with steam on shell side

3. 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

4. Which is the best tube arrangement (in a shell and tube heat exchanger) if the fluids are clean and non-fouling ?

   A. Square pitch
   B. Triangular pitch
   C. Diagonal square pitch
   D. None of these

5. The inside heat transfer co-efficient in case of turbulent flow of liquid in the tube side in a 1-2 shell and tube heat exchanger is increased by ______________ times, when the number of tube passes is increased to 8?

   A. 20.8
   B. 40.8
   C. 40.4
   D. 20.4

6. In a shell and tube heat exchanger, the tube side heat transfer co-efficient just at the entrance of the tube is_________________?

   A. Infinity
   B. Zero
   C. Same as average heat transfer co-efficient for tube side
   D. None of these

7. In a shell and tube heat exchanger, putting a longitudinal baffle across the shell, forces the shell side fluid to pass _____________ through the heat exchanger ?

   A. Once
   B. Twice
   C. Thrice
   D. Four times

8. The advantage of using a 1 – 2 shell and tube heat exchanger over a 1 – 1 shell and tube heat exchanger is_________________?

   A. Lower tube side pressure drop
   B. Lower shell side pressure drop
   C. Higher tube side heat transfer co-efficient
   D. Higher shell side heat transfer co-efficient

9. For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus- Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of________________?

   A. 1
   B. 1.74
   C. 6.1
   D. 37

10. 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