The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is ______________ compared to the same size pipes without fins?

Related Mcqs:

1. 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

2. 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

3. In a co-current double pipe heat exchanger used for condensing saturated steam over the inner tube, if the entrance and exit conditions of the coolant are interchanged, then the rate of condensation will___________________?

   A. Increase
   B. Decrease
   C. Remain unchanged
   D. Either increase or decrease; depends on the coolant flow rate

4. 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

5. 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

6. If all the conditions and dimensions are same, then the ratio of velocity through the tubes of a double pass heat exchanger to that through the single pass heat exchanger is_________________?

   A. 1
   B. 2
   C. 1/2
   D. 4

7. The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter D. as _________________?

   A. D-1.8
   B. D-0.2
   C. D0.2
   D. D1.8

8. 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

9. 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

10. 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