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Handbook of air conditioning and refrigeration / Shan K

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CHAPTER 15<br />

AIR SYSTEMS: COMPONENTS—<br />

FANS, COILS, FILTERS,<br />

AND HUMIDIFIERS<br />

15.1 FAN FUNDAMENTALS 15.2<br />

Functions <strong>and</strong> Types <strong>of</strong> Fans 15.2<br />

Fan Capacity or Volume Flow Rate 15.4<br />

Fan Pressure 15.4<br />

Fan Power <strong>and</strong> Fan Efficiency 15.4<br />

Air Temperature Increase<br />

through Fan 15.5<br />

Fan Performance Curves 15.5<br />

Influence <strong>of</strong> Elevation <strong>and</strong><br />

Temperature 15.6<br />

15.2 CENTRIFUGAL FANS 15.7<br />

Total Pressure Increase at Fan<br />

Impeller 15.7<br />

Backward-Curved Fans 15.8<br />

Radial-Bladed Fans 15.10<br />

Forward-Curved Fans 15.11<br />

Tubular or In-line Fans 15.12<br />

Unhoused Plug/Plenum Fans 15.12<br />

Centrifugal Ro<strong>of</strong> Ventilators 15.14<br />

15.3 AXIAL FANS 15.14<br />

Types <strong>of</strong> Axial Fans 15.14<br />

Velocity Triangles 15.16<br />

Performance Curves 15.18<br />

15.4 FAN CAPACITY MODULATION 15.20<br />

Fan Speed Modulation with Adjustable-<br />

Frequency, Variable-Speed Drives 15.20<br />

Inlet Vanes Modulation 15.21<br />

Inlet Cone Modulation 15.23<br />

Blade Pitch Modulation 15.24<br />

15.5 FAN SURGE AND STALL 15.24<br />

Fan Surge 15.24<br />

Fan Stall 15.24<br />

15.6 FAN CONSTRUCTION AND<br />

ARRANGEMENTS 15.25<br />

Size <strong>and</strong> Class St<strong>and</strong>ards 15.25<br />

Fan Width <strong>and</strong> Inlets 15.26<br />

Drive Arrangements <strong>and</strong> Direction <strong>of</strong><br />

Discharge 15.26<br />

High-Temperature Fans 15.27<br />

Spark-Resistant Construction 15.28<br />

Safety Devices 15.28<br />

15.7 FAN SELECTION 15.29<br />

Conditions Clarified <strong>and</strong> Factors<br />

Considered 15.29<br />

Estimated Fan Sound Power Level 15.30<br />

Comparison between Various<br />

Types <strong>of</strong> Fans 15.31<br />

Case Study—Selection <strong>of</strong> Fans 15.32<br />

15.8 COIL CHARACTERISTICS 15.32<br />

Types <strong>of</strong> Coils 15.33<br />

Fins 15.33<br />

Contact Conductance 15.37<br />

Water Circuits 15.39<br />

15.9 SENSIBLE COOLING AND SENSIBLE<br />

HEATING COILS—DRY COILS 15.39<br />

Heat Transfer in a Sensible Cooling<br />

Process 15.39<br />

Surface Heat-Transfer Coefficients 15.41<br />

Fin Efficiency 15.42<br />

Dry Coil Effectiveness 15.42<br />

Heating Coils 15.44<br />

Fluid Velocity <strong>and</strong> Pressure Drop 15.44<br />

Dry Coil at Part-Load Operation 15.44<br />

Coil Construction Parameters 15.45<br />

15.10 WATER COOLING COILS—DRY-WET<br />

COILS 15.48<br />

Dry-Wet Boundary 15.48<br />

Dry Part 15.49<br />

Wet Part 15.50<br />

Dry-Wet Coil at Part-Load Operation 15.50<br />

Selection <strong>of</strong> a Dry-Wet Coil 15.50<br />

15.11 COIL ACCESSORIES, CONDENSATE<br />

CONTROL, AND FREEZE-UP<br />

PROTECTION 15.56<br />

Coil Accessories 15.56<br />

Coil Cleanliness 15.57<br />

Condensate Collection <strong>and</strong> Drain<br />

System 15.57<br />

Coil Freeze Protection 15.58<br />

15.12 AIR CLEANING, RATING, AND<br />

ASSESSMENTS 15.60<br />

Air Filtration <strong>and</strong> Industrial Air<br />

Cleaning 15.60<br />

Atmospheric Dust <strong>and</strong> Space Air<br />

Contaminants 15.61<br />

Rating <strong>and</strong> Assessments 15.61<br />

15.13 TEST METHODS FOR AIR<br />

FILTERS 15.62<br />

Test Methods 15.62<br />

Test Unit 15.64<br />

15.14 AIR FILTERS 15.65<br />

Filtration Mechanism 15.65<br />

Classification <strong>of</strong> Air Filters 15.65<br />

Coarse Air Filters 15.65<br />

Low-Efficiency Air Filters 15.66<br />

Medium-Efficiency Air Filters 15.67<br />

High-Efficiency Air Filters 15.68<br />

15.1

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