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Mechanical Engineer´s Handbook P74

CHAPTER 55 PUMPS AND FANS William A. Smith College of Engineering University of South Florida Tampa, Florida 55.1 55.2 PUMPANDFANSIMILARITY SYSTEM DESIGN: THE FIRST STEP IN PUMP OR FAN SELECTION 55.2.1 Fluid System Data Required 55.2.2 Determination of Fluid Head Required 55.2.3 Total Developed Head of a Fan 55.2.4 Engineering Data for Pressure Loss in Fluid Systems 55.2.5 Systems Head Curves CHARACTERISTICS OF ROTATING FLUID MACHINES 55.3.1 Energy Transfer in Rotating Fluid Machines 55.3.2 Nondimensional Performance Characteristics of Rotating Fluid Machines 55.3.3 Importance of the Blade Inlet Angle 55.3.4 Specific Speed 1681 55.3.5 55.3.6 Modeling of Rotating Fluid Machines Summary of Modeling Laws 1691 1691 1692 1692 1692. | CHAPTER 55 PUMPS AND FANS William A. Smith College of Engineering University of South Florida Tampa Florida 55.1 PUMP AND FAN SIMILARITY 1681 55.2 SYSTEM DESIGN THE FIRST STEP IN PUMP OR FAN SELECTION 1682 55.2.1 Fluid System Data Required 1682 55.2.2 Determination of Fluid Head Required 1682 55.2.3 Total Developed Head of a Fan 1684 55.2.4 Engineering Data for Pressure Loss in Fluid Systems 1684 55.2.5 Systems Head Curves 1684 55.3 CHARACTERISTICS OF ROTATING FLUID MACHINES 1687 55.3.1 Energy Transfer in Rotating Fluid Machines 1687 55.3.2 Nondimensional Performance Characteristics of Rotating Fluid Machines 1687 55.3.3 Importance of the Blade Inlet Angle 1689 55.3.4 Specific Speed 1690 55.3.5 Modeling of Rotating Fluid Machines 1691 55.3.6 Summary of Modeling Laws 1691 55.4 PUMP SELECTION 1692 55.4.1 Basic Types Positive Displacement and Centrifugal Kinetic 1692 55.4.2 Characteristics of Positive Displacement Pumps 1692 55.4.3 Characteristics of Centrifugal Pumps 1693 55.4.4 Net Positive Suction Head NPSH 1693 55.4.5 Selection of Centrifugal Pumps 1693 55.4.6 Operating Performance of Pumps in a System 1694 55.4.7 Throttling versus Variable Speed Drive 1695 55.5 FAN SELECTION 1696 55.5.1 Types of Fans Their Characteristics 1696 55.5.2 Fan Selection 1696 55.5.3 Control of Fans for Variable Volume Service 1698 55.1 PUMP AND FAN SIMILARITY The performance characteristics of centrifugal pumps and fans i.e. rotating fluid machines are described by the same basic laws and derived equations and therefore should be treated together and not separately. Both fluid machines provide the input energy to create flow and a pressure rise in their respective fluid systems and both use the principle of fluid acceleration as the mechanism to add this energy. If the pressure rise across a fan is small 5000 Pa then the gas can be considered as an incompressible fluid and the equations developed to describe the process will be the same as for pumps. Compressors are used to obtain large