Smacna duct fitting loss coefficient

Negative numbers indicate that the static regain exceeds the dynamic pressure loss of the fitting. For a pipe fitting, select k coefficient from table. Ansismacna 0062006 hvac duct construction standards. The goal of that test program was to determine if the saddle tap tee is as efficient air moving junction and if so to include the resulting loss coefficient data in the ashrae duct fitting database dfdb. The types of fittings to be used based on the designers calculations of fitting losses i. In over 50 years of serving the mechanical system marketplace, mcgill airflow has gained a technical expertise, which is unmatched in the industry. Smc manufactures coil line ductwork in 456 lengths. The problem is, the ashrae tables are automatically assigned to the fitting and there is no way to change it. Determining pressure losses for airflow in residential ductwork. The only calculator in the industry to include the 0. If there is no assigned ashrae table, you get a 0pa pressure loss. Measurements of flat oval diverging flow fitting loss coefficients.

The local loss coefficient can be estimated experimentally by the measurement on the real model, or with using of numerical simulation. Use this mobile app in the field for quick duct pressure loss calculations. Conceptual models ere are two types of pressure loss in duct systems, namely, friction loss and dynamic loss. For any given fitting, enter the flow rate and fitting information and obtain loss coefficient data and associated pressure loss. This is a conservative value for the preliminary duct sizing and pressure drop estimates, considering a required duct velocity of 2500 fpm reference 2. Every fitting has associated loss coefficients, which can be determined experimentally by measuring the total pressure loss through the fitting for varying flow conditions. B fitting loss tables coefficient duct cross section to which coefficient c is referenced is at the top of each table. The duct friction pressure drop is assumed to be 0. I have both smacna and ashrae fitting loss coefficient tables but the values for the same cross sectional ratio and flow rate ratio are not even close. Loss coefficient data for 9 ductwork fittings were generated utilizing a commerciallyavailable computational fluid dynamics cfd code.

For a duct fitting, select coefficient from ashrae table. Research article pressure losses across multiple fittings in. Appendix 6 fitting loss coefficient tables duct flow. Handbookhvac systems smacnas hvac air duct leakage test manual. The coefficient for a three section elbow in smacna duct design handbook is 0. The coefficient for a 4 inch smooth 90 elbow with a 10 inch radius is 0. Culp airflow pressure losses through rigid metallic and nonmetallic flexible ducts were studied and recommendations to improve the rating of flexible ducts were made as. Pressure loss coefficients of 6, 8 and 10inch steel pipe. Ordinary heating, ventilating, and air conditioning duct systems read air pressures at 0. Specify a loss method for a fitting or accessory instance. The fundamentals of duct system design mcgill airflow. Example of duct fitting loss v u upstream velocity of fitting h height of the duct w width of the duct r radius of the bend.

Smacnas hvac air duct leakage test manual 1985 to verify the intent of the. Appendix 6 fitting loss coefficient tables duct flow fluid. Specify a pressure loss method for duct and pipe fittings and. Smc tdc, slipdrive and raw sheet metal connectors, inc. A procedure for predicting pressure loss coefficients of duct. Often the pressure loss is regressed vs the velocity pressure and the slope of the regression is the loss coefficient. Let us use the duct fitting for the diverging and converging flow used by ashrae standard 120, as shown in figure 1, as an example.

By conducting joint performance testing as described in section vii of the smacna hvac duct construction standards, 2nd ed. Pressure losses across multiple fittings in ventilation ducts. Air duct components and minor dynamic loss coefficients. Calculate the thermal gravity effect for the twostack system shown in figure 2, where the air is 120 c and the stack heights are 15. Pressure loss coefficients of 6, 8 and 10inch steel pipe fittings by chengwei alex ding, luke carlson, christopher ellis and omid mohseni prepared for american society of heating, refrigerating and airconditioning engineers, inc. The tables as shown herein are the smacna tables with those interpretations already substituted. Duct and pipe fittings loss mechengncpe mechanical 4 aug 11 11. Consequently, the total pressure or total energy of air flowing in a duct system is generally equal to the sum of the static pressure and the velocity pressure. A total of 159 unique coefficients were generated for the various flow and geometry conditions. Correction factor to be applied to the friction loss of singlewall duct.

Minor loss coefficients for different components in air duct distribution systems. Duct and pipe fittings loss hvacr engineering engtips. Dec 09, 20 in addition, the cfd method has been used to predict the pressure loss coefficient of many other duct fittings, such as damper, orifice, transition 911, 14, and junction fittings, in hvac ductworks as well as to conduct other ductrelated studies e. The pressure loss coefficient for the duct fittings,cs, is defined by equation 1 as the ratio of the total pressure loss across pl1 and pl2 to the. Level 1 duct design develops various aspects of sizing in detail because an oversized duct. Where area change, direction change, divided flow, or united flow fittings other than those illustrated here are shown on the contract drawings, are not of proprietary manufacture, and are defined with friction loss coefficients in either the smacna hvac duct system design manual or the ashrae fundamentals handbook chapter on duct design, such. This calculator, complete with detailed instructions, enables hvac system designers to design an average duct system without additional references. Hello, i have an issue with the fittings loss coefficient. To establish the equivalent length of dryer exhaust duct for the 4 inch smooth 90 elbow with a 10 inch radius, you cancel out the equivalent factors and are left with the following. A comprehensive duct layout indicating sizes, design airflows, pressure class, and routing of the duct system. Fittings may be saved into a project file, which is easily navigated and can be stored and transferred. This database, with cloudbased access by annual subscription, includes loss coefficient tables for more than 200 round, rectangular, and flat oval duct fittings.