Equal Friction Method

The Equal Friction method is utilized to compute the velocity through each section based on the constant friction loss and the divided flow rates through the system. Dimensions for linear duct for the section are computed from flow and velocity. Total pressure loss for the length of each duct is computed.

The Velocity Pressure at nodes exiting change-in-flow or change-in-size components is computed and listed in the table. Change-In-Flow components are listed in the FLC Summary table multiple times for each "flow-out" end, as they fall common to more than one section. The table also lists sizing parameters of flow and area for each fitting.

The Duct sizing section summary serves as a main interface to the Duct Sizing utility. The duct sizing data is manipulated to equalize pressure loss in a given route. When a route in a design is loaded the paths of the route are traced to analyse pressure loss. The critical paths are identified and are corrected by Equal Friction method. In this method the pressure loss across the path links are minimized and brought to a near constant value that is acceptable in the design. The resulted duct sizing parameters are then taken into system and the single line route is promoted to actual model. In the Duct sizing dialog, after setting desired Air Flow values for end terminal equipments, the system can be analyzed to tap critical paths. The openings in paths constitute either diffusers, grilles, or plenum boxes having specific air flow capacity. The Calculate function does the computing internally by taking the input velocity at the source. The summary table populates data of computed values against all duct elements. The critical path report lists the path and corresponding duct sections having maximum resistance. Such paths are set right by tuning in valid values and sizes to overcome the pressure loss. This resizing walkthrough is done in conjunction with FLC (Fitting Loss Coefficient) Summary table. After the desired duct sizing is through, the design can be rebuild using the computed values and promoted to 3D model.