Heat Transfer problems
- 1. Bulk of the convective heat transfer resistance from a hot tube surface to the fluid flowing in it, is
Options- A. in the central core of the fluid.
- B. uniformly distributed throughout the fluid.
- C. mainly confined to a thin film of fluid near the surface.
- D. none of these. Discuss
Correct Answer: mainly confined to a thin film of fluid near the surface.
- 2. Baffles in the shell side of a shell and tube heat exchanger
Options- A. increase the cross-section of the shell side liquid.
- B. force the liquid to flow parallel to the bank.
- C. increase the shell side heat transfer co-efficient.
- D. decrease the shell side heat transfer co-efficient. Discuss
Correct Answer: increase the shell side heat transfer co-efficient.
- 3. The actual temperature drop across the heating surface in an evaporator depends on the
Options- A. feed.
- B. depth of liquid over heating surface.
- C. pressure difference between steam chest and vapour space.
- D. all (a), (b) and (c). Discuss
Correct Answer: all (a), (b) and (c).
- 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
Options- 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. Discuss
Correct Answer: finned tube heat exchanger with air outside and steam inside.
- 5. The unit of heat transfer co-efficient in SI unit is
Options- A. J/M2°K
- B. W/m2°K
- C. W/m°K
- D. J/m°K Discuss
Correct Answer: W/m2°K
- 6. Controlling heat transfer film co-efficient is the one, which offers __________ resistance to heat transfer.
Options- A. no
- B. the least
- C. the largest
- D. lower Discuss
Correct Answer: the largest
- 7. Black liquor generated during paper manufacture is concentrated in a
Options- A. single effect evaporator.
- B. single effect evaporator followed by a crystalliser.
- C. multiple effect evaporator.
- D. multiple effect evaporators followed by a crystalliser. Discuss
Correct Answer: multiple effect evaporator.
- 8. Leidenfrost point is a term concerned with the
Options- A. condensation of the saturated vapor on a cold surface.
- B. concentration of a corrosive solution by evaporation.
- C. heat transfer between two highly viscous liquids.
- D. boiling of a liquid on a hot surface. Discuss
Correct Answer: boiling of a liquid on a hot surface.
- 9. Reynold's analogy states that
Options- A. Nst ? f
- B. Nst ? NRe
- C. NNu ? f
- D. NRe ? f Discuss
Correct Answer: Nst ? f
- 10. Pick out the wrong statement.
Options- A. The controlling resistance in case of heating of air by condensing steam is in the air film.
- B. The log mean temperature difference (LMTD) for counter flow and parallel flow can be theoretically same when any one of the fluids (hot or cold fluid) passes through the heat exchanger at constant temperature.
- C. In case of a 1 - 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs.
- D. Phase change in case of a pure fluid at a given pressure from liquid to vapor or vice-versa occurs at saturation temperature. Discuss
Correct Answer: In case of a 1 - 2 shell and tube heat exchanger, the LMTD correction factor value increases sharply, when a temperature cross occurs.
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