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
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.
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.