Page 356 - Fluid mechanics, heat transfer, and mass transfer

HEAT TRANSFER EQUIPMENT INVOLVING PHASE TRANSFER
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FIGURE 11.5 Horizontal reboilers.

FIGURE 11.6 (a) Vertical single pass, once-through with tube side boiling. (b) Vertical, recirculating with shell side boiling.

& All the liquid from the bottom tray passes to the once- before they are separated on admission into the
through reboiler where partial vaporization takes column.
place, establishing equilibrium between the two & With a circulating reboiler, because the liquid from
phases due to intimate contact between the phases the bottom tray of a column is of a composition
similar to that of the bottoms product, one can assume
that it does not act as a theoretical tray.
. What are the plus and minus points of (i) vertical natural
circulation reboiler, (ii) horizontal once-through/natu-
ral circulation type, and (iii) forced circulation reboiler?
(i) Vertical natural circulation type:
& Good controllability unlike once-through type.
& Easy fouling.
& Difficult to maintain.
(ii) Horizontal once-through/horizontal natural circu-
lation type:
& Not easily fouled.
& Less DP than for vertical type.
& Ease of maintenance.
Recirculating baffled bottoms reboiler system. (iii) Forced circulation type:
FIGURE 11.7