Downcomer head loss

Loss under Downcomer The head loss under the downcomer apron, as millimeters of hquid, may be estimated from... 

GPM = Column liquid loading, gal/min Hj,. = Downcomer backup, inches of liquid hi = Condensing side film coefficient, Btu/hrft °F H,(j = Head loss under downcomer, inches of liquid H v = Weir height, ins. 

The head loss in liquid flowing down the downcomer, under its underflow edge (and up over an inlet weir, if used) and onto the tray is important in determining the back up of liquid in the downcomer. There are many suggested relations representing this head loss. 

The main resistance to flow will be caused by the constriction at the downcomer outlet, and the head loss in the downcomer can be estimated using the equation given by Cicalese et al. (1947)... 

The heights of head losses in Eq. (14-92) should be in consistent units, e.g., millimeters or inches of liquid under operating conditions on the tray As noted, hdc is calculated in terms of equivalent clear liquid. Actually the liquid in the downcomer is aerated and actual backup is... 

This head loss, required for downcomer backup calculation (Sec. 6.2.7 , is calculated for segmental downcomers from (2-5,18,31,32)... 

Although there is no need to change the downcomer clearance in the top section, it is a good idea. The froth in the downcomer bottlenecks the top section, the head loss in the downcomer apron is quite high (1.26 in) and the tray spacing relatively low. The clearance in idle top section will therefore also be increased to 2 in. 

Head loss under downcomer apron, in clear liquid 0.70 1,02 0,55... 

Head loss due to liquid (low under the downcomer apron, in of liquid. 

A = downcomer area, cross-sectional area for total liquid down-flow, ft2 At - total tower cross-sections, area, ft2 Co vapor discharge coefficient for dry tray g = acceleration of grarity, 32.2 ft/sec2 hh = head loss due to vapor flow through perforations, in. liquid... 

The backup of the liquid in the downcomer is the liquid depth on the tray plus the equivalent tray pressure drop and the head loss under the downcomer skirt. The latter can be somewhat decreased by using a shaped downcomer skirt edge, but this measure is often found to be inconvenient. 

The polymer s loop circulation is set up and defined by the pressure balance between the two polymerization zones. As it flows dovm under gravity, the downcomer polymer bed pumps the gas downwards and recovers the head losses developed in the riser, the gas/polymer separator and all other sections of the... 

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