• Duct sizing methods • Equal-friction method with maximum velocity • Duct friction loss per unit length remains constant • Most widely used in normal HVAC applications • Constant-velocity method • Often for exhaust ventilation system • Minimum velocity to carry dust is important • Limit velocity to reduce noise Friction loss per 100' Coefficient of retardation based on pipe material Flow volume (GPM) Inside diameter of pipe V Q d = = = ((= P = P = = Ff = P software, the Irrigation System Design Calculator (information. The Chart. Once the TEL and ASP are calculated, you simply use the chart to intersect the two to calculate the design friction rate for the duct design. For example, if we calculated a 300′ equivalent length with an available static pressure of 0.2″WC (which is a very typical situation), that could be interpolated to a design friction rate C A friction loss per unit length is selected for all duct; this v alue is usually in the range of 0.05 to 0.2 inches wg per 100 feet of duct length. C All duct is sized using the known air volume flow rates and the selected friction loss. C Fitting losses can be calculated, but more often are estimated. View Duct Design Round-Friction-Loss-Chart.pdf from INGENIERIA 001 at Universidad de Monterrey. Table 1 - Circular Equivalent Diameter*, Equivalent Area of Rectangular Ducts for Equal DUCT ELBOWS, SQUARE THROAT No. 16 Up to 11" 40' EL 12" to 15" 55' EL 16" to 21" 75' EL 22" to 27" 100' EL 28" to 33" 125' EL RETURN AIR SYSTEM No. 810 Cold air boot, collar, duct 45- 65' EL AIR FLOW DYNAMICS & DUCT SIZING REFERENCE GUIDE SUPPLY OR RETURN DUCT SIZE/CAPACITY (.09 to .10 pressure drop per 100' EL the total pressure loss to the dynamic pressure in terms of velocity pressure. Friction Loss (Straight) The static pressure loss in a straight run of flexible duct, expressed in inches of water gauge (in. w.g.) per 100 feet [Pa/m]. Inner Core/Liner That portion of insulated flexible duct which determines the internal dimensions and inner Multiplying by 100 gets rid of two of those offending zeroes. Now are result for friction rate looks like this: In this case, our friction rate is 0.073 iwc/100′. That's the number we use to size the ducts. How to think about friction rate. The big problem a lot of people have with friction rate is they don't actually calculate it. They cranepumps.com Engineering Data SECTION PAGE DATE A Crane Co. Company USA: (937) 778-8947 • Canada: (905) 457-6223 • International: (937) 615-3598 12 90 Friction Loss For Water At 60° F Per 100 Feet Of Pipe New Schedule 40 Steel Pipe - The friction values are from the Hydraulic Institute Pipe Friction Manual. given you the quick reference chart approach to simplify and speed up the process. Total Duct Loss (˝wg) 70° † Galvanized metal roughness (ft) .0005 † Flow region Turbulent, 4000fpm † friction factor 0.02 † velocity pressure .999 Static Pressure (SP) Loss for 90° and 45° Die-Formed Elbows. 52 Engineering Data QuietR® Duct Liner Pressure Loss Performance This chart is to be used in place of the standard friction chart published in the ASHRAE Handbook of Fundamentals. For conversion of round equivalents to rectangular sizes, use Table 2, "Equivalent Rectangular Duct Dimensions" from the same reference. Tests conducted in accordance with NAIMA AHS to size a duct, only the flow rate of the Figure 1: Friction chart (E = 0.09 mm). duct section is considered. For instance, if a duct with aflowrateof0