The arrangement to insure proper draining of a single condenser depends on the type of receiver. If the receiver is top inlet, good drainage of the condensate results if the vapor in the receiver can flow freely counterflow to the condensate, as appears in Fig. 7.28. The provisions15 for achieving open channel flow in the drain line are:
– avoid a horizontal drain line, if possible, sloping the line with a pitch of at least 1 in 50
– choose a large-size pipe based on liquid velocities no higher than about 0.5 m/s (100 fpm)
– do not place a valve in the sloping drain line with its stem upward. Instead use angle valves which introduce much less pressure drop than straight through globe valves. If a straight-through valve is used, place it in the vertical portion of the drain line
If the receiver is bottom inlet, as in Fig. 7.29, the liquid is inherently trapped and the vapor in the receiver has no access to the vapor space in the condenser. For this reason an equalizer line should be connected from the top of the receiver to the outlet of the condenser.