Downcomer apron head loss

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

Downcomer backup. The factors that resist liquid flow from the downcomer onto the tray below are the froth height on the tray, the pressure drop on the tray, and the friction loss under the downcomer apron. These factors cause liquid to back up in the downcomer. Each of these factors can be expressed in terms of clear liquid heads. A tray pressure balance gives... 

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. 

The segments of the buildup are (a) the equivalent clear liquid bead on the tray h Ll (b) any hydraulic gradient A caused by resistance to liquid flow across the tray, which usually is not significant for sieve trays, (c) liquid head equivalent to pressure loss due to flow under the downcomer apron. A. and (d) total pressure loss across the tray above, necessarily included to maintain the dynamic pressure balance between point A (just above the floor of tray 3) and point B in the vapor space above tray 2. 

Head Loss Under Downcomer Apron hoa is calculated based on BoUes (1963) ... 

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