3-K (Darby) Method

The 3-K method described in Darby, 2001Darby, R., Chemical Engineering Fluid Mechanics, 2nd edition, Marcel Dekker, New York, NY, 2001., pp. 209-211, is used for high accuracy of predicted loss factors at low Reynolds numbers. The 3-K loss model is available in the valve and bend junctions where there is a dropdown menu to select from standard types of elbows and valves. After selecting an option in this menu, the 3 K's will be displayed at the bottom of the properties window. These values come from the chart in Darby on pages 210-211. The user can also select User Specified in the 3-K (Darby) dropdown menu to input their own values for K1, Ki, and Kd.

Where:

  • Kf = Resistance coefficient

  • K1 = 3-K method constant

  • Ki = 3-K method constant

  • Kd = 3-K method constant

  • Re = Reynolds Number

  • Dn,in = Inner diameter

The Bend Properties Window with 3-K (Darby) selected as the Type.

Figure 1: Bend Properties window when the 3-K (Darby) method is turned on

Related Topics

Laminar and Non-Newtonian Corrections Panel

Adjusted Turbulent K Factor Method (ATKF)

Improved ATKF Method

Note about Laminar Corrections for Fittings

Junction Loss Models

K Factor Loss Model

Kv and Cv Loss Model

Resistance Curve Loss Model

Equivalent Length