An Introduction to Aircraft Thermal Management

Description

Aircraft Thermal Management (ATM)focuses on how to manage heat in an aircraft to meet the temperature requirements for passengers and vehicle. This primarily involves removing heat and protecting equipment, systems, and structure from heat sources that could raise their temperature beyond design limits. Crew and passengers must be neither too hot nor too cold during airplane operations. Thus, maintaining thermal comport is critically important, and not a trivial operation. Written by Mark F. Ahlers, a retired Boeing Technical Fellow and its first Thermal Marshal, An Introduction to Aircraft Thermal Management is the ultimate source of knowledge concerning: Temperature and thermal related requirementsAirplane-generated heat sourcesExternal heat sourcesAircraft heat sinksFire and FailuresEnvironmental control systemsThermal designAnalytical modelingAnalytical softwareTestingMilitary aircraft thermal management Fully illustrated and amply referenced, An Introduction to Aircraft Thermal Management provides a very balanced approach between theory and practice, best practices and technical insights.It is a must-have reference for both young engineers starting in the filed and for seasoned professionals willing to re-sharpen their skills. Cover Table of Contents Introduction CHAPTER 1 Why Aircraft Thermal Management Matters 1.1 Introduction 1.2 Temperature Requirements 1.3 Removing Heat 1.4 Protection 1.5 Increased Importance 1.5.1 Composite Materials 1.5.1.1 Advantages over Metals 1.5.1.2 Disadvantages of Using Composites 1.5.2 Higher Heat Loads 1.5.3 More Electric Aircraft 1.5.3.1 No-Bleed Systems 1.5.3.2 Electric Actuators 1.5.3.3 Challenges References CHAPTER 2 Temperature and Thermal-Related Requirements 2.1 Introduct ion 2.2 Outside Ambient Conditions 2.2.1 Climate and Aircraft Performance 2.2.1.1 Standard Day 2.2.1.2 Environmental Envelope 2.2.1.3 Safe Operations 2.2.1.4 Performance 2.2.1.5 Operational Requirements and Limits 2.2.1.6 OAT and Airplane Performance 2.2.1.7 MIL-HDBK-310 2.2.2 Boundary Temperature Calculations 2.2.2.1 Ground 2.2.2.2 Sky 2.2.2.3 Ram Air 2.2.3 Boundary Pressure Calculations 2.2.3.1 Pounds Mass versus Pounds Force 2.2.3.2 Total (Ram) Pressure 2.2.4 Humidity 2.2.5 Solar Flux 2.2.6 Wind Speed 2.3 Pressurized Volume 2.3.1 Passenger Cabin and Flight Deck (Thermal Comfort) 2.3.1.1 Thermal Comfort Parameters 2.3.1.2 Thermal Load 2.3.1.3 Predicted Mean Vote 2.3.1.4 Predicted Percentage Dissatisfied 2.3.2 Cargo Compartments 2.3.3 Equipment 2.4 Unpressurized Area 2.4.1 Fuel 2.4.2 Hydraulics 2.5 Structure 2.5.1 External Bulk 2.5.2 Internal References CHAPTER 3 Airplane-Generated Heat Sources 3.1 Introduction 3.2 Occupants 3.2.1 Sensible Heat 3.2.2 Latent Heat 3.2.3 Passengers and Crew 3.2.4 Live Animal Cargo 3.2.5 Avionics and Electrical Equipment 3.3 Flight Controls and Hydraulic Systems 3.3.1 Hydraulic 3.3.2 Electric 3.3.3 Flight Control Thermal Impact 3.4 Lights 3.5 Power Feeders 3.5.1 Electromagnetic Interference 3.5.2 Inductive Loads 3.6 Brakes 3.6.1 Brake Heat Sink 3.6.2 Brake Temperatures 3.6.3 Brake Heating during Successive Missions 3.6.4 MLG Wheel Well 3.6.5 BTMS Selection at Gate Release 3.6.6 Brake Fans 3.6.7 Thrust Reverses 3.6.8 Fuse Plugs 3.7 Environmental Control System 3.7.1 Air Supply 3.7.2 Packs 3.7.3 Fans 3.7.4 Anti-icing/Deicing Systems References CHAPTER 4 External Heat Sources 4.1 Introduction 4.2 Solar Heating 4.2.1 The Sun 4.2.2 Incident Solar Load 4.2.3 Time of Day and Surface Orientation 4.2.4 Solar Absorptance and Reflectance 4.2.5 Transmittance 4.2.6 Modeling Terrestrial Radiation 4.2.6.1 Extraterrestrial Radiation 4.2.6.2 Declination Angle 4.2.6.3 Solar Time 4.2.6.4 Zenith Angle 4.2.6.5 Altitude or Elevation Angle 4.2.6.6 Air Mass Model 4.2.6.7 Clear Sky Model 4.3 Aerodynamic Heating 4.3.1 Subsonic Flight 4.3.2 Supersonic Flight 4.4 Lightning References CHAPTER 5 Aircraft Heat Sinks 5.1 Introduction 5.2 Ambient Air 5.2.1 Structure and Unpressurized Ambient Cooling 5.2.2 Systems Cooling 5.2.2.1 Ram-Air Systems 5.2.2.2 Skin Heat Exchangers 5.2.2.3 Cabin Exhaust 5.3 Sky 5.4 Fuel 5.4.1 Thermal Capacitance 5.4.2 Fuel Supply Line and Energy Recovery Reference CHAPTER 6 Fires and Failures 6.1 Introduction 6.2 Fires 6.2.1 MLG Wheel Well 6.2.2 Engine and APU 6.2.3 Cargo Compartment 6.2.3.1 Class A 6.2.3.2 Class B 6.2.3.3 Class C 6.2.3.4 Class E 6.2.3.5 Class F 6.2.3.6 Cargo Liners 6.2.4 Passenger and Crew Area 6.2.4.1 Prevention 6.2.4.2 Fire Detection 6.2.4.3 Fire Suppression 6.2.5 Electrical/Electronic Bay and Lower Lobe 6.2.5.1 787 Lithium-Ion Battery Fires 6.2.5.2 Why Lithium Ion? 6.2.6 Fuel Tank Fires 6.2.7 External Fuel Fire 6.3 System Failures 6.3.1 Burst Ducts 6.3.2 Leaking Ducts References CHAPTER 7 Environmental Control Systems 7.1 Introduction 7.2 Cabin Temperature and Pressure Control 7.2.1 Air Supply (1 to 2) 7.2.1.1 No-Bleed System 7.2.1.2 Ground-Based Operation 7.2.2 Air Conditioning (3) 7.2.2.1 AIR Cycle Machine 7.2.2.2 Vapor Cycle Machine 7.2.2.3 AIR Cycle Versus Vapor Cycle Machine 7.2.3 Air Distribution (4-8) 7.2.3.1 Recirculation System 7.2.3.2 Main Cabin 7.2.3.3 Flight Deck 7.2.4 Cargo Heat and Cargo Air Conditioning 7.2.5 Cabin Pressure Control 7.3 Venting and Chiller Exhaust 7.4 EE Cooling 7.4.1 Active Cooling 7.4.2 Passive Cooling 7.4.3 Flight Critical Equipment 7.5 Protective Systems 7.5.1 Wing Anti-ice 7.5.1.1 Thermal 7.5.1.2 Chemical 7.5.1.3 Mechanical 7.5.2 Engine Anti-ice 7.5.3 Ice Detection 7.5.4 Air Data Sensors 7.5.5 Windshields References CHAPTER 8 Thermal Design 8.1 Introduction 8.2 Insulation Types 8.2.1 Fiberglass 8.2.2 Open Cell Foams 8.2.2.1 Polyimide 8.2.2.2 Melamine 8.2.3 Closed Cell Foams 8.2.4 Ceramics 8.2.5 Felt 8.2.6 Aerogels 8.3 Insulation Applications 8.3.1 Fuselage 8.3.2 Ducting and Hot Pack Components 8.3.3 Engine and Auxiliary Power Unit (APU) 8.3.4 Cargo Compartments 8.3.5 Insulation Placement: Heat Source or Receiver 8.4 Surface Coatings and Applications 8.4.1 Low Solar Absorptivity Paints 8.4.2 Low Emissivity Coatings 8.5 Radiation Shields 8.6 Phase-Change Materials 8.7 Intumescent Paints 8.8 Ablation Materials 8.9 Increase Heat Sink 8.9.1 Ram Air 8.9.2 Fuel 8.9.2.1 Fuel Flammability 8.9.2.2 Nitrogen-Generating Systems 8.9.2.3 Systems Cooling 8.9.2.4 Increasing Ambient Cooling 8.10 Reduce Heat Generation 8.11 Spot Cooling 8.11.1 Unpressurized Air 8.11.2 Pressurized Air 8.12 Modify Material References CHAPTER 9 Analytical Modeling 9.1 Introduction 9.2 Mathematical Modeling of Heat Transfer 9.2.1 Thermal Resistances 9.2.1.1 Conduction 9.2.1.2 Convection 9.2.1.3 Radiation 9.2.2 Thermal Capacitance 9.2.3 Energy Sources 9.2.4 Mass Transfer (Fluid Flow) 9.2.5 Analytical Modeling Using the Electrical Analogy 9.2.5.1 Series Resistance 9.2.5.2 Parallel Resistance 9.2.5.3 Example: Heat Transfer from an Insulated Hot-Air Duct 9.2.5.4 Iterative Method 9.3 Mathematical Modeling of Airflow Systems 9.3.1 Bernoulli’s Equation 9.3.1.1 Head 9.3.1.2 Gases 9.3.2 Pressure Generation: Fans and Pumps 9.3.2.1 Fan Pressure 9.3.2.2 Pump Head 9.3.3 System Pressure Drop 9.3.3.1 Frictional Losses 9.3.3.2 Loss Coefficients 9.3.4 Flow Calculation References CHAPTER 10 Analytical Software 10.1 Introduction 10.2 Thermal/Fluid Systems 10.2.1 SINDA 10.2.2 Computer-Aided Design (CAD) Embedded 10.3 1-D Network Flow 10.3.1 System 1-D CFD 10.3.2 Component 3-D CFD 10.4 Multi-domain/Co-simulation 10.5 Computational Fluid Dynamics 10.5.1 External Flows 10.5.2 Internal Flows 10.5.3 Advantages and Limitations 10.5.4 Expanded Use 10.6 Pre-processing 10.7 Post-processing 10.8 General Programming Environments 10.9 Tool Source 10.9.1 In-house 10.9.2 In-house versus COTS Software 10.9.3 Open Source 10.9.4 Government 10.10 Software Evaluation and Selection References CHAPTER 11 Testing 11.1 Introduction 11.2 Identifying the Need 11.2.1 Analytical Uncertainty and Design Margins 11.2.2 Certification Requirements 11.2.3 System Criticality 11.3 Material Thermal and Surface Optical Properties 11.3.1 Thermal Conductivity 11.3.1.1 Guarded Hot Plate 11.3.1.2 Comparative Cut-Bar Method 11.3.1.3 Composite Materials 11.3.2 Specific Heat 11.3.3 Infrared Emissivity and Reflectivity 11.3.4 Solar Absorptance and Reflectance 11.3.5 In-Service Degradation of Properties 11.3.5.1 Materials 11.3.5.2 Surfaces 11.4 FAA Fire Testing 11.4.1 Materials 11.4.1.1 FAA Fire Test Handbook 11.4.1.2 Burn Resistance 11.4.1.3 BurnThrough 11.4.2 Systems 11.4.2.1 Cargo 11.4.2.2 Heat Generation 11.5 Model Validation 11.5.1 Temperatures 11.5.1.1 Thermometers 11.5.1.2 Probes 11.5.2 Fluid Flow and Pressure Drops 11.5.2.1 Pitot Tube 11.5.2.2 Manometers 11.5.2.3 Mechanical Pressure Gauges 11.5.2.4 Electromechanical 11.5.2.5 Hot-Wire Anemometers 11.5.2.6 Ultrasonic Meters 11.6 Testing Boundary Conditions 11.7 Testing Standards and Procedures 11.7.1 Industry Trade Organizations 11.7.2 Engineering Societies 11.7.3 Military 11.8 Systems Testing 11.9 Airplane Testing 11.9.1 Data Extrapolation References CHAPTER 12 Military Aircraft Thermal Management 12.1 Introduction 12.2 Commercial Airframes 12.2.1 Advantages 12.2.2 Disadvantages 12.2.3 Military Avionics 12.3 Bombers 12.4 Fighters 12.5 Vertical Lift 12.6 Directed Energy Weapons (DEWs) References Nomenclature About the Author Index