Modeling of Heat and Moisture Transfer in Porous Textile Medium Subject to External Wind: Improving Clothing Design

  • Nesreen GhaddarEmail author
  • Kamel Ghali
Reference work entry


This chapter covers convective modeling approaches of heat and moisture transfer in textile materials coupled with human thermal response models. Fabrics are highly porous and relatively thin materials consisting mainly of solid fiber, adsorbed water vapor, and gaseous mixture of water vapor and air in the void space. Fabric ventilation is induced by external wind or body motion which causes the air to penetrate the fabric and transfer heat and water vapor away from the human skin to the environment.

Convective fabric models are developed to predict local and overall clothing ensemble ventilation rates. This modeling approach is combined with segmental bio-heat model to predict human local and overall comfort in hot humid environment. The integration of clothing ventilation models with “cylindrical” segments of the clothed human body is presented showing examples of how segmental and inter-segmental ventilation, sensible heat loss, and moisture transport through clothing are used to assess the whole body comfort.



Area of the fabric (m2)


Inner node area in contact with the outer node (m2)


Outer-node exposed surface area to air flow (m2)


Gas concentration in the micro-climate measurement location (m3 Ar /m3 air)


Fiber specific heat (J/kg K)


Gas concentration in the distribution system (m3 Ar /m3 air)


Specific heat of air at constant pressure (J/kg ⋅K)


Specific heat of air at constant volume (J/kg ⋅K)


Water vapor diffusion coefficient in air (m2/s)


Fabric thickness (m)


Gravitational acceleration (m/s2)


Heat of adsorption (J/kg)


Normalized conduction heat transfer coefficient between inner node and outer node (W/m2⋅K)


Normalized convection heat transfer coefficient between outer node and air flowing through fabric (W/m2⋅K)

hc( f-∞)

Heat transport coefficient from the fabric to the environment (W/m2⋅K)

hc( o-air)

Heat transport coefficient from the fabric to the trapped air layer (W/m2⋅K)

hc(skin -air)

Heat transport coefficient from the skin to the trapped air layer (W/m2⋅K)


Heat of vaporization of water (J/kg)


Normalized diffusion mass transfer coefficient between inner node and outer node (kg/m2⋅kPa⋅s)


Normalized mass transport coefficient between outer node and air void in the fabric (kg/m2⋅kPa⋅s)


Mass transfer coefficient between the fabric and the environment (kg/m2⋅kPa⋅s)

hm( o-air)

Mass transfer coefficient between the fabric and the air (kg/m2⋅kPa⋅s)

hm(skin -air)

Mass transfer coefficient between the skin and the air layer (kg/m2⋅kPa⋅s)


Permeability index


Thermal conductivity of air (W/m⋅K)


Linearized radiative heat transfer (W/m2⋅K)


Fabric length in z direction (m)

\( {\dot{m}}_{aY} \)

Mass flow rate of air in radial direction (kg/m2⋅s)

\( {\dot{m}}_{a\theta} \)

Mass flow rate of air in angular direction(kg/m2⋅s)

\( {\dot{m}}_{aZ} \)

Mass flow rate of air in axial direction (kg/m2⋅s)

\( {\dot{m}}_a \)

Total ventilation rate (kg/m2⋅s)


Pressure of the microclimate air (kPa)


Pressure at the external surface of the fabric (kPa)


Temperature of the microclimate air (°C)


Ambient temperature (°C)


Skin temperature (°C)


Temperature of the fabric outer layer (°C)


Temperature of the fabric void layer (°C)


Heat loss (W/m2)


Total regain in fabric (kg of adsorbed H2O/kg fiber)


Fabric dry resistance (m2⋅K/W unless specified in the equation per mm of thickness)


Fabric evaporative resistance (m2⋅kPa/W)


The dynamic resistance for ventilation through the fabric (m2⋅K/W)


Fabric cylinder radius (m)


Segment cylinder radius (m)


Liquid movement velocity (m/s)


Velocities of the environment cross wind (m/s)


Humidity ratio (kg of water/kg of air)


Air layer thickness (m)


Coordinate in vertical direction (m)

Greek Symbols


Fabric air permeability (m3/m2⋅s)


The volumetric thermal expansion (°C−1)


Viscosity of air (N·s/m2)


Angular coordinate


Porosity of fabric


Density of air (kg/m3)



Conditions of air in the annulus




Fabric outer node


Fabric void node


Conditions at the skin surface

Environment condition


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Mechanical Engineering, Faculty of Engineering and ArchitectureAmerican University of BeirutBeirutLebanon

Section editors and affiliations

  • Kambiz Vafai
    • 1
  1. 1.Department of Mechanical EngineeringUniversity of California, RiversideRiversideUSA

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