Tray Area Definitions

Tray Area Definitions Some of these are illustrated in Fig. 14-17. 

Definitions of tray area, vapor load, and liquid load... 

Area definitions. Areas used for defining tray velocity are ... 

Equations (3.89) and (3.90) equate the tray active area vapor loading VN to the maximum VM for determining the gas in liquid entrainment flooding of the tray. The early work of Souders and Brown [12], based on a force balance on an average suspended droplet of liquid, led to the definition of a capacity parameter VM- Both VN and Where refer to the active area of the tray. This active area is simply the net tower cross-section internal area less the downcomer areas. The downcomer areas include both the downcomer inlets and outlets. 

The apparent residence time is the ratio of the downcomer volume to the clear liquid flow in the downcomer, The downcomer volume is the tray spacing times the average downcomer cross-section area. The true residence time is the ratio of froth volume in the downcomer to the frothy liquid flow in the downcomer. The true residence time can alternatively be expressed as the ratio of the clear liquid volume in the downcomer to the clear liquid flow. The definition adopted here is that of the apparent downcomer residence time. The author found this definition to be better and to be consistent with riublished criteria for downcomer residence times (1]. 

For the calculation of the dry pressure loss of bubble cap and valve trays a shghtly different approach is recommended. The orifice coefficients are not related to the velocity in the smallest geometrical open area but to the whole active area of the tray since the quality of tray design depends not only on the pressme loss of a single element but also on the number of elements arranged on the tray. The following definition implies both quantities ... 

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