comfort
TRANSCRIPT
Human Comfort
Evaluating Comfort and Related Physical Properties of Textiles
28 - 30° C
Human Comfort
Comfort is freedom from pain, freedom from discomfort. It is a neutral state1
Comfort is a pleasant state of physiological, psychological and physical harmony between a human being and the environment2
1 Hatch, K.L. (1993). Textile science. Minneapolis, MN: West Publishing Co., p. 26.
2 Slater, K. (1985). Human comfort. Springfield, IL: Charles C. Thomas Publisher, p. 4.
What Comfort really is:
RelativeSubjective
PsychologicalPhysiological
Thermal-Sensorial-Mobile-
Human ComfortPsychological Comfort implies that
individuals need specific garments, fabrics, colors and design features to help them feel confident and at ease within the context of the various roles they assume.
Factors: Self-Image Relationship with others: Trust, love and
respect Need of privacy: Solitude, silence, anonymity
Human ComfortPhysiological Comfort refers to
maintenance of thermal balance: The proper relationship between body heat production and loss.Factors: Cardiovascular system Skeleto-muscular system Central nervous system Pulmonary system Digestive system Thermoregulatory mechanism
Human ComfortPhysical Aspects of Comfort refer to
different sensations and feelings of discomfort and/or pain, which influence the two types of comfort.
Factors: Touch Sight Hearing Taste Smell
Comfort-Related Physical Properties of Textiles
Thermo-physiological Comfort Thermal resistance Water vapor permeability (breathability) Wickability Sorption of water Water resistance, repellency and proofness Drying rate
Sensorial (Neuro-physiological) Comfort Prickliness, itchiness, inflammation Roughness Thermal character (warm/cool feeling) Electrostatic propensity
Body-Movement Comfort Stretch Weight Pressure/compression
Physical Characteristics of Textile Materials Influencing Thermal Comfort
Fabric MassFabric ThicknessFiber, Yarn, and Fabric StructuresPorosity is the ratio of air space to the total
volume of the fabric, expressed as a percentage
Cover Factor is defined as the opacity or hiding power in textiles
The Physics of Human Comfort
Body metabolism Heat transferEvaporation
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Body Thermal Balance
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Body Thermal Balance
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21
Heat Transfer
Heat Transfer refers to the transfer of heat energy from one environment to another. Heat transfer occurs whenever a temperature difference (T) exists between two environments; heat moves from the warmer surface or area to the cooler surface or area.
The rate at which heat is transferred depends on T as well as any resistance imposed between the two environments.
Modes of Heat Transfer Conduction: is the transfer of heat by physical
contact, either within a body or between two touching bodies
Convection: is heat transfer via a moving air mass within space
Radiation: involves heat transfer through space in the form of electromagnetic energy
Heat Transfer
Units. Several terms are used to quantify heat transfer: Thermal transmittance (U): is the rate of heat transfer
per unit area, U = W/m2K°. Thermal conductance ©: is defined by the same
formula, C = W/m2K° Thermal resistance (r): the rate of flow of heat
through a fabric under standard conditions. The r-value is the inverse of thermal transmittance (r = 1/U).
A fabric has a thermal resistance of one “tog” when a temperature difference between two surfaces of 0.1°C produces a heat flow equal to 1 W/m2.
A “clo” is the resistance necessary to keep a resting person (producing heat at a rate of 58 W/m2) comfortable at 21°C and at an air movement rate of 0.1 m/s.
1 clo = 1.55 togs; 1 clo = 0.1548r; 1 clo = U/0.1548
Effect of Fabric Properties on Heat Transfer Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied
Heat Transfer
Heat Transfer
Standard Test Methods CAN/CGSB-4.2 No. 70.1 – 94, Thermal
insulation performance of textile materials ASTM D 1518 – 85, Thermal transmittance of
textile materials
Thermal Insulation
cold plate
hot plate
specimenProcedure 1
cold platespecimen
hot plate
Procedure 2
cold plate
cold platespecimen
specimenhot plate Guarded Hot Plate
Thermal CharacterThermal absorptivity (b) is a transient-state
parameter that describes the thermal contact properties of a textile material (warm-cool feeling) at the beginning (first two seconds) of its contact with human skin.
Where: = thermal conductivity
c = thermal capacity
The lower the value of (b), the warmer the feeling
b = (c)1/2 [Ws1/2/m2K]
Alambeta: measurement of
transient and steady-state
thermo-physical properties
Moisture TransferIt refers to the transfer of liquid water or vapor.
The transfer of moisture generally is from the wetter environment to the drier environment until equilibrium is reached. Moisture is produced by the body in the form of perspiration (insensible and sensible perspirations).
Types of Moisture Transfer Diffusion Sorption Wicking Evaporation
Water-Proof FabricOUTER
INNER
Breathable Fabric
water vapour
Liquid water
Moisture Transfer
Factors Affecting Moisture Transfer Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied
Moisture TransferStandard Test Methods
CAN/CGSB-4.2 No. 49 – 99, Resistance of materials to water vapour diffusion
ASTM F1868-98, Thermal and evaporative resistance of clothing materials using a sweating hot plate
ISO 11092: 1993 (E), Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded-hotplate test)
ASTM E 96, Water vapor transmission of materials ASTM D 4772, Standard test method for surface
water absorption of terry fabrics (water flow test method)
AATCC Method 79, Absorbency of bleached textiles
WATER VAPOUR
DIFFUSION
Sweating Guarded Hot Plate
Water Resistance and RepellencyWater Resistance: a physical barrier to
water penetrationWater Repellent: does not allow water
penetration in one side but it allows moisture transfer from body
Water-proof: does not allow any penetration of water from either side to the other.
Shower-proof, Rain-proof
AIR
water drop
Hydrophilic
Cotton (attractive surface)
AIRwater drop
Hydrophobic
Olefin (repulsive surface)
Factors Affecting Water Resistance and Repellency Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied
Water Resistance and Repellency
Water Resistance and RepellencyStandard Test Methods
AATCC Method 21, Water repellency: Static absorption test
AATCC Method 22, Water repellency: Spray test AATCC Method 35, Water resistance: rain test AATCC Method 42, Water resistance: Impact
penetration test AATCC Method 70, Water repellency: Tumble jar
dynamic absorption test AATCC Method 127: Water resistance: Hydrostatic
pressure test
Impact penetration tester
Rain tester Hydrostatic pressure tester
Air Permeability
It is the degree to which the material is penetrable by air. It is also the rate of air flow through a fabric when there is a different air pressure on either surface of the fabric.
Air Permeability
Factors Affecting Air Permeability Fiber type and structure Yarn type and structure Fabric type and structure Finishes applied
Standard Test Methods CAN/CGSB-4.2 No. 36 – M89, Air
permeability ASTM D – 737, Air permeability of textile
fabrics