1 duct System Design duct System Design Guide First Edition 2003 McGill AirFlow Corporation McGill AirFlow Corporation One Mission Park Groveport, Ohio 43125. Notice: No part of this work may be reproduced or used in any form or by any means graphic, electronic, or mechanical, including photocopying, recording, taping, or information storage and retrieval systems without the written permission of McGill AirFlow Corporation. The performance data included in this Guide have been obtained from testing programs conducted in flow measurement laboratories and detailed in the reference test reports.
2 The data are reprinted in this manual as a source of information for Design engineers. McGill AirFlow Corporation assumes no responsibility for the performance of duct System components installed in the field. McGill AirFlow Corporation is a wholly owned subsidiary of United McGill Corporation. i duct System Design Table of Contents Introduction ..vi An Overview of the Design How to Use the duct System Design Chapter 1: AirFlow Fundamentals for Supply duct Systems .. Overview .. Conservation of Continuity Equation .. Diverging Flows .. Conservation of Energy .. Static Pressure .. Velocity Total Pressure Loss in duct (Friction Loss).
3 Round duct .. Flat Oval duct .. Rectangular duct .. Acoustically Lined and Double-wall duct .. Nonstandard Pressure Loss in Supply Fittings .. Loss Diverging-flow Fittings: Branches .. Diverging-flow Fittings: Straight-Throughs, Reducers, and Miscellaneous Fittings .. Nonstandard Chapter 2: Designing Supply duct Determination of Air Volume Location of duct Runs .. Selection of a Design Equal Friction Design .. Constant Velocity Design .. Velocity Reduction Static Regain Design .. Total Pressure Which Design Method? .. Equal Friction Design .. duct Determination of System Pressure.
4 Excess Static Regain Design .. duct Determination of System Pressure .. Excess i duct System Design Chapter 3: Analyzing and Enhancing Supply duct Systems Analyzing a Preliminary Supply Balancing Equal Friction Designs .. Balancing Dampers .. Orifice Plates .. Enhanced Equal Friction Design .. Enhanced Static Regain Fan System Effect Performance Deficiencies .. duct Performance Fan Pressures .. Cost Optimization .. Chapter 4: AirFlow Fundamentals for Exhaust duct Systems Overview .. Conservation of Continuity Equation .. Converging Flows .. Conservation of Energy .. Pressure Pressure Loss in duct (Friction Loss).
5 Pressure Loss in Return or Exhaust Fittings (Dynamic Losses) .. Nonstandard Conditions for Dynamic Losses .. Chapter 5: Designing Exhaust duct Systems .. Defining the Application and Determining Determining Capture Velocities and Air Volume Locating duct Runs .. Determining duct Sizes Based on Velocity Mixing of Two Air Streams .. Determining System Pressure Requirements .. Chapter 6: Analyzing Exhaust duct Fitting Balancing the System .. Using Dampers .. Using Corrected Volume Flow Using Smaller duct Sizes and Less Efficient Specifying and Selecting a Fan .. System Considerations.
6 Chapter 7: Acoustical Fundamentals .. Overview .. Sound Power and Sound ii duct System Design Wavelength .. Loudness .. Weighting .. Chapter 8: duct System Acoustics .. Fan Noise .. Natural Attenuation .. duct Wall Elbow Reflections .. Sound Power End AirFlow -Generated Noise .. Radiated duct Break-Out Noise .. Break-In Nonmetal Chapter 9: Room Acoustics .. Air Terminal ASHRAE Room Effect .. Design NC Rating Method .. RC Rating Method .. Criteria Design Guidelines .. Other Criteria .. Spectrum Shape .. Chapter 10: Supplemental Attenuation Calculating Attenuation Double-Wall Insulated and Single-Wall Lined duct Noise Attenuation of Insulated duct Systems.
7 Dissipative Reactive Silencers .. Active No-Bullet Computer Analysis .. Appendix: General Information .. Glossary of Terms .. Conversion Tables .. Area/Diameter Tables and Equations .. Round duct Size and Area .. Spiral Flat Oval duct Shape Conversion Tables .. Nonstandard Condition Correction Velocity and Velocity iii duct System Design Product Metal Properties .. Gauge, Thickness and Weight .. ASTM Standards .. ASTM ASTM ASTM ASTM ASTM B209 .. ASTM ASTM ASTM E477 .. McGill AirFlow Corporation Manufacturing Industrial Manufacturing Standards .. Derivation of the Continuity Derivation of TP= SP+ VP.
8 Derivation of Velocity Pressure Darcy-Weisbach Equation for Calculation Friction Surface Derivation of Pressure Loss in Supply Fittings .. Derivation of Presssure Loss in Exhaust Fittings .. Negative Loss Coefficients .. Derivation of the Inlet Static Pressure Loss Pressure Loss Data .. duct .. Single-Wall duct Friction Loss Chart .. k-27 Correction Round-to-Flat Oval Transition, C vs. Velocity .. Round Slip Coupling, C vs. Diameter .. Acoustical Data .. Double-Wall Round duct .. Flat Oval Rectangular Single-Wall Round Silencers .. Round .. Rectangular .. duct Installation of Single-Wall duct and Fittings.
9 Installation of Double-Wall duct and Fittings .. UNI-COAT duct and Fittings .. Specifying duct Recommended Specifications for Commercial and Industrial Construction Specification Institute (CSI), Alexandria, Production Systems for Architects and Engineers .. Using Computers for duct Design .. UNI- duct iv duct System Design ASHRAE duct Fitting Database Program .. ASHRAE Algorithms for HVAC Acoustics .. References .. HVAC Systems duct Design , Sheet Metal and Air Conditioning Contractors National Association (SMACNA), 1990 Chantilly, VA ..A. 95. ASHRAE Handbooks, American Society of Heating, Refrigerating and Air- Conditioning Engineers (ASHRAE), Atlanta, Air Diffusion Council Publications (ADC), Chicago, American Socitey for Testing and materials (ASTM), Philadelphia, American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, OH Air Movement and Control Association (AMCA), Arlington Heights, T-Method by Robert Tsal (see reference ASHRAE Fundamentals Handbook).
10 Engineering Report 151, Flat Oval- The Alternative to Rectangular (see Part IV. EDRM, Supplementary Topics by United McGill Corporation).. Engineering Report 102, Effect of Spacing Tees (see Part IV EDRM, Supplementary Topics by United McGill Corporation).. Noise Control for Buildings and Manufacturing Plants, Bolt, Beranek and Newman, Inc., v duct System Design INTRODUCTION. Foreword These reference manuals have been compiled and written by engineers and consultants employed by United McGill Corporation and its subsidiary, McGill AirFlow Corporation. McGill AirFlow Corporation is the nation=s foremost producer of sheet metal duct and fitting components for air handling systems.