Fan Handbook, Selection, Application and Design, Bleier-text

Fan Handbook, Selection, Application and Design, Bleier-text

(Parte 1 de 4)


Other McGraw-Hill Handbooks of Interest Avallone and Baumeister * marks' standard handbook for mechanicalENGINEERSBrady etal • materials handbookBrink • handbook of fluid sealingChironis and Sclater • mechanisms and mechanical devices sourcebookCzernik • gasket handbookHarris and Crede • shock and vibration handbookHicks • handbook of mechanical engineering calculationsLingaiah • machine design data handbookParmley • standard handbook of fastening and joiningRothbart » mechanical design handbookShigley and Mischke • standard handbook of machine designSkousen • valve handbookSuchy • die design handbookWalsh • electromechanical design handbookWalsh * McGRAW-HILL machining and metalworking handbook

FAN HANDBOOKSelection,Application,and Design Frank P. Bleier, re.Consulting Engineerfor Fan Design

Boston, Massachusetts Burr Ridge, IllinoisDubuque, Iowa Madison, Wisconsin New York, New YorkSan Francisco, California St. Louis, Missouri

Library of Congress Cataloging-in-Pub!ication Data

Bleier. Frank P.Fan handbook : selection, application, and design / Frank P.Bleier.p. cm.Includes index.ISBN 0-07-005933-0 (alk. paper)1. Fans (Machinery)—Handbooks, manuals, etc. I. Title.TJ960.B58 1997621.6'1 —dc21 97-23697CIPMcGraw-HillA Division o/'TheMcGraw-Hill CompaniesCopyright Q 1998 by The McGraw-Hill Companies, Inc. All rights reserved.Printed in the United States of America. Except as permitted under theUnited States Copyright Act of 1976. no part of this publication maybe reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of thepublisher. 5 6 7 8 9 BKM BKM 0987654321

ISBN 0-07-005933-0

The sponsoring editorfor this book was Harold B. Crawford, the editingsupervisor was Paul fi. Sobel, and the production supervisor was TinaCameron. It was set in Times Roman by North Market Street Graphics.

McGraw-Hill books are available at special quantity discounts to use aspremiums and sales promotions, or for use in corporate training programs.For more information, please write to the Director of Special Sales,McGraw-Hill. 1 1 West 19th Street, New York. NY 1001 1. Or contact yourlocal bookstore.

Information contained in this work has been obtained by TheMcGraw-Hill Companies, Inc. ("McGraw-Hill") from sourcesbelieved to be reliable. However, neither McGraw-Hill nor itsauthors guarantee the accuracy or completeness of any informa-tion published herein and neither McGraw-Hill nor its authorsshall be responsible for any errors, omissions, or damages arisingout of use of this information. This work is published with theunderstanding that McGraw-Hill and its authors are supplyinginformation but are not attempting to render engineering or otherprofessional services. If such services are required, the assistanceof an appropriate professional should be sought.

Foreword xiPreface xiiiList of Symbols xvConversion Factors xvii Chapter 1. Basics of Stationary and Moving Air 1.1

Atmospheric Pressure / /. /Static Pressure / 1.3Airflow Through a Round Duct of Constant Diameter. Velocity Pressure / 1,3Airflow Through a Converging Cone / 1.9Airflow Through a Diverging Cone / /.//Aerodynamic Paradox / 1.12Tennis Ball with Top Spin / 1. 13Airflow Through a Sharp Orifice. Vena Contracta / 1.14Venturi Inlet / 1.14Airflow Along a Surface / 1.16

Chapter 2. Airfoils and Single-Thickness Sheet Metal Profiles 2.1Description and Function of an Airfoil / 2.1Influence of Shape on Airfoil Performance / 2.3Lift Coefficient, Drag Coefficient / 2.3Characteristic Curves of Airfoils / 2.4Single-Thickness Sheet Metal Profiles / 2.8Function ofAirfoil Blades in Axial and Centrifugal Fans / 2.10 Chapter 3. Types of Fans, Terminology, and Mechanical Construction 3.1

Six Fan Categories / 3.1Axial-Flow Fans / 3.1Centrifugal Fans / 3.8Axial-Centrifugal Fans / .?./.?RoofVentilators / 3.16Cross-Flow Blowers / 3.19Vortex or Regenerative Blowers / 3.20Conclusion / 3.20 Chapter 4. Axial-Flow Fans 4.1Nomenclature / 4.1Mathematical Fan Design versus Kxperimental Cut-and-Try Methods / 4.1 vi CONTENTS

Axial Flow and Helical Flow / 4.2Blade Twist, Velocity Distribution / 4.3Two-Stage Axial-Flow Fans / 4.28Influence ofTip Clearance on the Performance of Vaneaxial Fans / 4.38Vaneaxial Fans with Slotted Blades / 4.39Applications with Fluctuating Systems / 4.44Noise Level / 4.44Outlet Diffuser and Outlet Tail Piece / 4.45Selection of Axial-Flow Fans / 4.46Overlapping Performance Ranges / 4.53Sample Design Calculation for a 27-in Vaneaxial Fan / 4.56Axial-Flow Fans Driven by Compressed Air / 4.69 Chapter 5. Fan Laws 5.1

Conversion of Fan Performance / 5. 1Variation in Fan Speed / 5. /Variation in Fan Size / 5.4Variation in Both Fan Size and Fan Speed / 5.6Variation in Size and Speed with Reciprocal Ratios / 5.7Variation in Density / 5.9Machining Down the Fan Wheel Outside Diameter / 5. 12 Chapter 6. System Resistance 6.1

Airflow Systems / 6.1Airflow Through a Pool of Stationary Liquid / 6.1Airflow Through Filter Bags / 6.3Airflow Through a Grain Bin / 6.4Airflow Through a Ventilating System / 6.4Comparison of System Characteristic Curves and Changing Speed Curves / 6.6Shifting the Operating Point Out of the Stalling Range / 6.6Pressure Losses in Ventilating Systems / 6.7How the Static Pressure Varies Along a Ventilating System / 6.8 Chapter 7. Centrifugal Fans 7.1

Flow Pattern / 7.1Operating Principle / 7.1Drive Arrangements / 7.2Types of Blades / 7.2Pressure Blowers,Turbo Blowers / 7.42Turbo Compressors / 7.46Two Centrifugal Fans in Parallel / 7.55Volume Control / 7.55Summary / 7.58 Chapter 8. Fan Selection, Specific Speed, Examples 8.1

Selection of Axial-Flow Fans / 8.1Selection of Centrifugal Fans / 8.1Specific Speed N„ Specific Diameter D, / 8.2


Examples of the Selection and Application of Fans / 8.3Conclusion / 8.12

Chapter 9. Axial-Centrifugal Fans 9.1 Flow Patterns for Various Configurations / 9.1Performance of Axial-Centrifugal Fans / 9.4

Chapter 10. Roof Ventilators 10.1 Four Ways to Subdivide Them / 10.1Ten Configurations of Roof Ventilators / 10.2

Chapter 1. Ventilation Requirements and Duct Systems 1.1OSHA Regulations / //./Comfort Conditions / 1.1Five Methods to Calculate the Air Volume Required for a Space / 1.2Four Methods to Design Duct Systems and to Determine the Required StaticPressure / 1.8

Chapter 12. Agricultural Ventilation Requirements 12.1 Types of Ventilation for Agricultural Requirements / 12.

Chapter 13. Cross-Flow Blowers 13.1Review / 13.Flow Pattern and Appearance / 13.1Performance of Cross-Flow Blowers / 13.3Advantages and Disadvantages / 13.3

Chapter 14. Flow Coefficient and Pressure Coefficient 14.1Review / 14.1Two Methods for Comparing Performance / 14.1Comparison of Coefficients for Various Fan Types / 14.6Plotting y versus <p Instead of Static Pressure versus Air Volume / 14.7

Chapter 15. Vortex Blowers 15.1Review / 15.1Flow Pattern and Appearance / 15.Principal Dimensions of the Vortex Blower / 15.1Performance of the Vortex Blower / 15.2Noise Level of the Vortex Blower / 15.3Applications of the Vortex Blower / 15.4

Viii CONTENTS Chapter 16. Various Methods to Drive a Fan 16.1

Prime Movers / 16.1Types of Motor Drive / 16.1Types of FJectric Motors Used to Drive a Fan / 16.1Summary / 16.2

Chapter 17. Fanless Air Movers 17.1

Principle of Operation / 17.1Performance / 17.1 Chapter 18. Performance Testing of Fans 18.1

Description of the AMCA Test Code ' 18.1Various Laboratory Test Setups . /8.Accessories Used with Outlet and Inlet Ducts / 18.3Instruments / 18.6Test Procedure / 18.17Test Forms / / 18.20 Chapter 19. Vacuum Cleaners 19.1

Review / 19.1Configurations / 19.1Testing / 19.2Performance / 19.8 Chapter 20. Fan Performance as Shown in Catalogs 20.1

Three Ways to Present Fan Performance / 20.1Computation of Rating Tables for Belt Drive, Derived from Test PerformanceCurves / 20.2Computation of Rating Tables for Belt Drive from Another RatingTable / 20.3Analyzing Rating Tables Published by Manufacturers / 20.4 Chapter 21. Air Curtains 21.1

Flow Pattern and Function / 21.1Outside Wind / 21.1Induced Airflow / 21.1Requirements / 21.2Three Examples / 21.7Performance Testing / 21.8Summary / 21.8

Chapter 2. Ceiling Fans 2.1 Description / 2.1Function During the Heating Season / 2.1

CONTENTS ix Function During the Summer / 2.1Performance / 2.2Applications / 2.3Summary / 2.4

Chapter 23. AMCA Standards 23.1Standards Handbook / 23.Centrifugal Fans / 23.1Drive Arrangements for Centrifugal Fans / 23.1Operating Limits for Centrifugal Fans / 23.4Spark-Resistant Construction / 23.6Summary / 23.8 Chapter 24. Mechanical Strength 24.1

Centrifugal Force / 24.1Tensile Stress and Yield Stress / 24.1Axial Reaction Force / 24.2Shaft Torque / 24.3Test Pit / 24.3 Chapter 25. Trouble Shooting and Problem Solving 25.1

Guidelines / 25.1Converging Cone / 25.2Wrong Rotation / 25.2Wrong Inlet Spin / 25.2Wrong Units (Metric) / 25.2 Chapter 26. Installation, Safety, and Maintenance 26.1

Safety Precautions / 26.1Airflow at Fan Inlet and Outlet / 26.2High-Temperature Fans / 26.2V-Belt Drive / 26.2Lubrication of Bearings and Couplings / 26.4Vibration / 26.4Protection of Fan While Not in Use / 26.5 Index follows Chap. 26 1.1

After receiving a degree in applied physics, Mr. Bleier worked for three fan manu-facturers, first as a draftsman in Lyons, France, next as a test engineer in East Moline,Illinois, and then as a director of research in Chicago, Illinois. Since then, he hasworked as a consulting engineer for 137 fan manufacturers, most of them in theUnited States, some in Canada, and one in Germany.Over the years, Mr. Bleier has designed and tested close to 800 fans, among themmost of the units pictured in this book. His designs ranged in size from a 4-in-diameter vaneaxial fan, used to ventilate a copy machine, to a 1000-hp, four-stageturbo blower, producing more than 300 in of static pressure, for pneumatic convey-ing of grain from cargo ships. Some of his other interesting assignments haveincluded the design of low-noise exhaust fans for invasion ships used by the Navyduring World War I and the development of a pressure blower used to pressurizethe flotation bags of an Army tank to make it amphibious.Mr. Bleier has written seven articles for technical magazines and for two engi-neering handbooks in simple, easy-to-understand language. He also has held twelveseminars at universities and for industrial groups. He is listed in Who's Who in Engi-neering and holds several patents on mixed-flow fans.By sharing his broad experience with others, Mr. Bleier will help engineering stu-dents and people engaged in the design, manufacture, selection, application, andoperation of fans. If you are active in one of these fields, you will benefit from read-ing this book. Jerome R. Reich, Ph.D.Chicago, Illinois

Let me say a few words about Robert Andrews Millikan. He was the Americanphysicist who performed the so-called oil-drop experiment to determine the electriccharge ofan electron. Millikan also was a good teacher and was proud ofit. He oncemade the statement:"I can explain anything to anybody"That's quite a statement. Itimpressed me. In writing this book, I have kept this statement in mind and have triedto produce an understandable text and to present some effortless reading material.The story of fans is about airflow considerations, such as velocities, pressures, andturbulence losses. This book will give explanations of these concepts and presentsample calculations to enable engineers and nonengineers to design fans and sys-tem&/to select and apply fans for systems, and to meet requirements for air volume,static pressure, brake horsepower, and efficiency.If the reader is familiar with high school mathematics, he or she will be able tounderstand and apply the principles, graphs, and formulae presented here. Calculusand differential equations are not used in this book. Instead, a "feel" for aerody-namics will be developed gradually, ajudgment ofwhat an air stream will or will notdo.The early chapters present the basics that will be needed to understand the prin-ciples discussed in later, more advanced chapters.In grateful memory to Mr. Archibald H. Davismy former boss and teacher. Frank P. BleierChicago, Illinois xiil

Cvmbol Meaning UnitAR Air ratio 1A Area ftAa Annular area ft:AR Aspect ratio Ia Angle of attack5 Air angle past bladeahp Air horsepower hpBP Barometric pressure inHgP Relative air anglep + ct Blade angle o/ Blade width inbhp Brake horsepower hpft /mincfm or Q Rate of flowD Wheel diameter ind Hub diameter inDB Dry-bulb temperature opWB Wet-bulb temperature opt Temperature opT Absolute temperature KdB Decibel sound level dBDR Diffuser ratio 1Ds Specific diameter inSpecific speed min"'£J Frequency, musical note sV Volts VA Amps AW Watts WkW Kilowatts kWME Mechanical or total efficiency %SE Static efficiency %r Radius inP Air density lb/ft*Re Reynolds numberrpm Revolutions per minute min"1SP Static pressure, positive inWC, psiSP Static pressure, negative inWCinHgTP Total pressure inWCV Vacuum inHgft'V VolumeV Velocity fpmVP Velocity pressureFlow coefficient inWC Pressure coefficient

VOLUME 1 ft' = 1728 in'

1 fpm (foot per minute) = 0.01 1364 mph {miles per hour)1 mph = 8 fpmAcceleration due to gravity f> = 32. 17 ft/s2 PRESSURE

xvii xvtu CONVERSION FACTORSTEMPERATUREl°Fs(|-)0C.bgi32oFsff,CThus (example) 80°F*<80-32) x |26.7°CAbsolute temperature T=T+ 459 7Example: 80"F= 539.7 K (absolute temperature) xvtu CONVERSION FACTORSTEMPERATUREl°Fs(|-)0C.bgi32oFsff,CThus (example) 80°F*<80-32) x |26.7°CAbsolute temperature T=T+ 459 7Example: 80"F= 539.7 K (absolute temperature)


Our planet earth has an average diameter of about 7914 mi or a radius of 3957 mi. Itis surrounded by a comparatively thin layer of air.The air pressure is highest close toearth, due to compression by the weight of the air above. At higher altitudes, as theheight of the air column above becomes less, the air pressure decreases, as shown inFig. 1 . 1 . At sea level, the atmospheric or barometric pressure is 29.92 inHg. At an alti-tude of 15 mi or 79,20 ft, which is only 0.4 percent of the earth's radius, the atmo-spheric pressure is only 1.0 inHg (3 percent of the sea level pressure). However,some rarified air extends about 50 mi up, which still is only 13 percent of the earth'sradius.The air consists mainly of nitrogen (about 78 percent by volume) and oxygen(about 21 percent by volume) plus less than 1 percent of other gases. Air is a physi-

Altitude (Miles)FIGURE 1.1 Atmospheric pressure %'ersus altitude. 1.1

1.2 CHAFfER ONE cal mixture (not a chemical compound) of these gases. Normally, air also containssome water vapor. This reduces the air density, as will be discussed in Chap. 18, ontesting.According to the National Advisory Committee for Aeronautics (NACA), latersucceeded by the National Aeronautics and Space Administration (NASA), tem-perature, atmospheric pressure, and air density at various altitudes are as shown inTable 1.1. TABLE 1.1 Temperature, Pressure, and Density versus Altitude

(Parte 1 de 4)