Flooding vapor rates, reduction

In practice, the vapor velocity used is less than that at the flooding velocity t raljood by a factor (<1) chosen based on best practice. In addition, one has to account for a reduction in the actual vapor flow cross-sectional area from the column diameter dj based area (fn/4)df) due to the area of the downcomer, area j. All such considerations are included in the following expression for the given total vapor flow rate in a column ... 

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