Heat and Moisture Transfer Between Human Body and Environment

Human adaptation under cold or hot temperatures has always required specific fabrics for clothing. Sports or protective garment companies propose to improve performance or safety. Behind thermal comfort lays many physical/physiological topics: human thermoregulation loop, natural or forced convection, heat and vapor transfer through porous textile layers, solar and infrared radiation effects. This book leads through progressive and pedagogic stages to discern the weight of all the concerned physical parameters.

Teacher and researcher, Jean-Paul Fohr worked in various disciplines around fluid mechanics and heat. His publications in CNRS laboratories demonstrate a multidisciplinary career.

Preface ix

Chapter 1. Building a Model for a Coupled Problem 1

1.1. Basic equations of the models (Appendix 1) 2

1.2. Boundary layers 3

1.2.1. Forced convection 4

1.2.2. Natural convection 6

1.3. Heat balance for a “system” and boundary conditions 8

1.4. On the problem of cooling of a cup of tea 11

1.4.1. Balance equations 12

1.4.2. Research of transfer correlations13

1.4.3. Surface temperature as a function of average temperature of the liquid 15

1.4.4. Liquid temperature as a function of time 16

1.5. Bather on a beach 19

Chapter 2. Approximate Determination of Transfer Coefficients 25

2.1. Natural convection around an isolated sphere 25

2.1.1. Equations of boundary layers depending on velocity and temperature 26

2.1.2. Integration over the boundary layer thickness 28

2.1.3. Dimensionless formulation 32

2.1.4. Numerical solution 33

2.2. Coupled exchanges around the head of a baby lying down 37

2.2.1. System of equations 38

2.2.2. Boundary layers for the horizontal disk 40

2.2.3. Boundary layers on curved surfaces 41

2.3. Forced convection around a cylinder 43

2.3.1. System of equations 44

2.3.2. Integration of the equations of the dynamic boundary layer 46

2.3.3. Dimensionless integral equation 48

2.3.4. Resolution of the upwind dynamic boundary layer 50

2.3.5. Resolution of the downwind dynamic boundary layer 55

2.3.6. Resolution of the thermal boundary layer 56

Chapter 3. Human Thermal Models 61

3.1. The Fanger model: from climatic chamber to standard 61

3.1.1. Environment and human body physical parameters 62

3.1.2. Equilibrium balance equation in the Fanger model 69

3.1.3. Examples of ambient environment qualifications 72

3.2. Gagge model 76

3.2.1. A simple, unsteady and regulated geometrical model 76

3.2.2. Response of “human system” to a sudden change in metabolism 78

3.3. Stolwijk 25 node model 80

3.4. Thermal model of a baby lying down 82

3.4.1. Geometrical division 82

3.4.2. Metabolism and respiration 83

3.4.3. Exchanges of the uncovered part of the head 84

3.4.4. Conduction between body layers 85

3.4.5. Sensible heat exchanges of the trunk 87

3.4.6. Trunk evaporation 88

3.4.7. Blood convection 89

3.4.8. System of equations 90

3.4.9. Simulation results 91

Chapter 4. Heat and Humidity Transfer in Clothing 97

4.1. From heterogeneous porous to continuous model media 98

4.2. Heat diffusion and convection 100

4.3. Vapor diffusion 101

4.4. The effect of bound water 105

4.5. Liquid water diffusion 111

4.6. Mass and energy balances 119

4.7. Limit conditions 121

4.8. Processing for a numerical resolution 123

4.9. First example: condensation in a multilayer 124

4.10. Convection and diffusion 128

4.11. Taking account of radiation 130

4.12. Second example: firefighters’ clothing 135

4.13. Traditional warm weather clothing 137

Appendices 143

Appendix 1 145

Appendix 2 151

Appendix 3 155

Bibliography 157

Index 161

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