LMTD for evaporators & condensers for a given terminal parameters & set of conditions for counter-flow is equal to that for parallel flow. In such heat exchangers, with one of the fluids condensing or evaporating, the surface area required is the least in the ______________ flow?

Related Mcqs:

1. In a liquid-liquid heat exchanger, for the same process temperature, the ratio of the LMTD in parallel flow to the LMTD in counter flow is always__________________?

   A. < 1
   B. > 1
   C. 1
   D. ∞

2. 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

3. LMTD for counter-flow and parallel flow heat exchanger will be the same, when the_________________?

   A. Cold fluid is heated to a certain temperature by condensing steam (isothermal fluid)
   B. Outlet temperature of both the hot and cold fluid are same
   C. Outlet temperature of hot fluid is less than the outlet temperature of the cold fluid
   D. None of these

4. In a parallel flow heat exchanger, if the outlet temperature of hot and cold fluids are the same, then the log mean temperature difference (LMTD) is_________________?

   A. Minimum
   B. Maximum
   C. Zero
   D. Infinity

5. Indirect contact heat exchangers are preferred over direct contact heat exchangers, because_________________?

   A. Heat transfer co-efficient are high
   B. There is no risk of contamination
   C. There is no mist formation
   D. Cost of equipment is lower

6. 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

7. LMTD correction factor which is to be applied for a cross-flow heat exchanger increases with increase in the number of shell passes. Its value for a single pass cross flow heat exchanger is __________________?

   A. 0
   B. 1
   C. > 1
   D. < 1

8. If air (a non-condensing gas) is present in a condensing vapor stream, it will ______________ the condensation rate of vapor?

   A. Increase
   B. Decrease
   C. Not affect
   D. Increase the condensing film co-efficient as well as

9. 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

10. Presence of a non-condensing gas in a condensing vapour___________________?

    A. Increases the rate of condensation
    B. Decreases thermal resistance
    C. Is desirable to increase the film co-efficient
    D. None of these