Fans and ventilation: a practical guide : the practical reference book and guide to fans, ventilation and ancillary equipment with a comprehensive buyers' guide to worldwide manufacturers and suppliers

1 Fan h i s t o r y , types and characteristics 1.1 Introduction 1,2 Ancient history --- "Not our sort of fan" 1.2.1 The advent of mechanical air movement using "air pumps" and fires 1.2.2 Early mine ventilation fans 1.2.3 The dawn of tunnel ventilation 1.2.4 The first Mersey road tunnel 1.2.5 Mechanical draught 1.2.6 Air conditioning, heating and ventilation 1.2.7 Developments from the 1930s to the 1960s 1.2.8 More recent tunnel ventilation fans 1.2.9 Longitudinal tunnel ventilation by jet fans 1.2.10 The rise of the axial flow fan 1,3 Definitions and classification 1.3.1 Introduction 1.3.2 What is a fan? 1.4 Fan characteristics 1.5 Centrifugal fans 1.5.1 Introduction 1.5.2 Forward curved blades 1.5.3 Deep vane forward curved blades 1.5.4 Shrouded radial blades 1.5.5 Open paddle blades 1.5.6 Backplated paddle impellers 1.5.7 Radial tipped blades 1.5.8 Backward inclined blades 1.5.9 Backward curved blades 1.5.10 Reverse curve blades 1.5.11 Backward aerofoil blades 1.5.12 General comment 1.6 Axial flow fans 1.6.1 Introduction 1.6.2 Ducted axial flow fans 1.6.2.1 Tube axial fan 1.6.2.2 Vane axial fan (downstream guide vanes - DSGV) 1.6.2.3 Vane axial fan (upstream guide vanes- USGV) 1.6.2.4 Vane axial fan (upstream and downstream guide vanes- U/DSGV) 1.6.2.5 Contra-rotating axial flow fan 1.6.3 Blade forms 3 5 10 11 12 13 15 15 18 20 21 21 21 22 22 22 22 23 23 24 24 24 25 25 26 26 26 26 26 27 27 28 28 28 28 28 1.6.3.1 Free vortex 1.6.3.2 Forced vortex 1.6.3.3 Arbitrary vortex 1.6.4 Other types of axial flow fan 1.6.4.1 Truly reversible flow 1.6.4.2 Fractional solidity 1.6.4.3 High pressure axial fans 1.6.4.4 High efficiency fans 1.6.4.5 Low-pressure axial fans 1.7 Propeller fans 1.7.1 Impeller construction 1.7.2 Impeller positioning 1.7.3 Diaphragm, ring or bell mounting 1.7.4 Performance characteristics 1.8 Mixed flow fans 1.8.1 Why the need - comparison of characteristics 1.8.2 General construction 1.8.3 Performance characteristics 1.8.4 Noise characteristics 1.9 Miscellaneous fans 1.9.1 Cross flow fans 1.9.2 Ring shaped fans 1.10 Bibliography 2 The properties of gases 2.1 Explanation of terms 2.1.1 Introduction 2.1.2 Changes of state 2.1.2.1 Boiling point 2.1.2.2 Melting point 2.1.3 Ideal gases 2.1.4 Density 2.1.5 Pressure 2.2 The gas laws 2.2.1 Boyle's law and Charles' law 2.2.2 Viscosity 2.2.3 Atmospheric air 2.2.4 Water vapour 2.2.5 Dalton's law of partial pressure 2.3 Humidity 2.3.1 Introduction 2.3.2 Relative humidity 2.3.3 Absolute humidity 29 29 29 29 29 29 29 30 30 30 30 30 30 31 31 31 32 32 32 32 32 33 33 35 36 36 36 36 36 36 36 36 36 36 37 37 38 38 38 38 38 39 FANS & VENTILATION Xl Contents 2.3.4 Dry bulb, wet bulb and dew point temperature 2.3.5 Psychrometric charts 2.4 Compressibility 2.4.1 Introduction 2.4.2 Gas data 2.4.3 Acoustic problems 2.5 Hazards 2.5.1 Introduction 2.5.2 Health hazards 2.5.3 Physical hazards 2.5.4 Environmental hazards 2.5.5 Installation hazard assessment 2.6 Bibliography 3 Air and gas flow 3.1 Basic equations 3.1.1 Introduction 3.1.2 Conservation of matter 3.1.3 Conservation of energy 3.1.4 Real thermodynamic systems 3.1.5 Bernoulli's equation 3.2 Fan aerodynamics 3.2.1 Introduction 3.2.2 Elementary centrifugal fan theory 3.2.3 Elementary axial fan theory 3.2.3.1 Use of aerofoil section blades 3.2.4 Elementary mixed flow fan theory 3.3 Ductwork elements 3.3.1 Introduction 3.3.2 Diffusers 3.3.3 Blowing outlets 3.3.3.1 Punkah Iouvres 3.3.2 Grilles 3.3.4 Exhaust inlets 3.3.4.1 Comparison of blowing and exhausting 3.3.4.2 Airflow into exhaust opening for dust extract 3.3.4.3 Loss of pressure in hoods 3.3.4.4 Values of coefficient of entry Ce 3.3.4.5 General notes on exhausting 3.4 Friction charts 3.4.1 Duct friction 3.5 Losses in fittings 3.5.1 Bends 3.5.1.1 Reducing the resistance of awkward bends 3.5.2 Branches and junctions 3.5.3 Louvres and grilles 3,5.4 Expansions and contractions XII FANS & VENTILATION 39 39 39 39 39 39 39 39 41 41 41 41 41 43 45 45 45 45 45 46 47 47 47 49 50 51 51 51 53 55 56 57 58 59 59 60 61 61 62 62 64 65 65 66 66 66 3.5.5 Square or rectangular ducting 66 3.5.6 Non g.s.s. (galvanised steel sheet) ducting 67 3.5.7 Inlet boxes 67 3.5.8 Discharge bends 68 3.5.9 Weather caps 68 3.6 Air duct design 68 3.6.1 Blowing systems for H & V 69 3.6.1.1 Design schemes 69 3.6.1.2 Duct resistance calculation 69 3.6.1.3 General notes 69 3.6.2 Exhaust ventilation systems for H & V 70 3.6.2.1 Industrial schemes 70 3.6.2.2 Take-off regain 70 3.6.2.3 Effect of change in volume 70 3.7 Balancing 70 3.7.1 Unbalanced system example 70 3.7.2 Balancing scheme 71 3.7.3 Balancing tests 71 3.8 Notes on duct construction 72 3.8.1 Dirt 72 3.8.2 Damp 72 3.8.3 Noise 72 3.8.4 Inlet and discharge of fans 72 3.8.5 Temperature control 72 3.8.6 Branch connections 72 3.8.7 Fire damper 72 3.8.8 Adjustment of damper at outlets 73 3.9 Duct design for dust or refuse exhaust 73 3.9.1 General notes 73 3.9.2 Design scheme 73 3.9.3 Calculation of resistance 73 3.9.4 Balancing of dust extract systems 74 3.10 Bibliography 75 4 Fan performance Standards 77 4.1 Introduction 78 4.1.1 Fan performance 79 4.1.2 The outlet duct 79 4.1.3 ISO conventions 80 4.1.4 Common parts of ducting 81 4.1.5 National Standard comparisons 82 4.1.6 Flow conditioners 83 4.2 Laboratory Standards 84 4.3 Determining the performance of fans in-situ 84 4.3.1 Introduction 84 4.3.2 Performance ratings 84 4.3.3 Measuring stations 84