Comfort

Human ComfortEvaluating Comfort and Related Physical Properties of Textiles28 - 30 CHuman ComfortComfort is freedom from pain, freedom from discomfort. It is a neutral state1Comfort is a pleasant state of physiological, psychological and physical harmony between a human being and the environment21 Hatch, K.L. (1993). Textile science. Minneapolis, MN: West Publishing Co., p. 26.2Slater, K. (1985). Human comfort. Springfield, IL: Charles C. Thomas Publisher, p. 4.What Comfort really is:RelativeSubjectivePsychologicalPhysiologicalThermal-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-ImageRelationship with others: Trust, love and respect Need of privacy: Solitude, silence, anonymityHuman 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 mechanismHuman 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 SmellComfort-Related Physical Properties of TextilesThermo-physiological Comfort Thermal resistance Water vapor permeability (breathability) Wickability Sorption of water Water resistance, repellency and proofness Drying rateSensorial (Neuro-physiological) Comfort Prickliness, itchiness, inflammationRoughness Thermal character (warm/cool feeling) Electrostatic propensityBody-Movement Comfort Stretch Weight Pressure/compressionPhysical Characteristics of Textile Materials Influencing Thermal ComfortFabric MassFabric ThicknessFiber, Yarn, and Fabric StructuresPorosity is the ratio of air space to the total volume of the fabric, expressed as a percentageCover Factor is defined as the opacity or hiding power in textilesThe Physics of Human ComfortBody metabolism Heat transferEvaporationHBhthFhFChFRhFKTaoaIa, Ta, oa'IclTcloclTsk, oskhtC, htR, htK, htEComfort ModelBody Thermal BalanceW M HB = ) 0 =nF t Bh h H S ) cl a clf I I h , , p LBody Thermal Balance )

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A= =+ =+ =+ + + =nw a rR SR StkxkxkxATKT T k RC C CE E EK C R E h-2 1Heat TransferHeat Transfer refers to the transfer of heat energy from one environment to another. Heat transfer occurs whenever a temperature difference (AT) 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 AT 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 energyHeat TransferUnits. 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 0.1C 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 21C and at an air movement rate of 0.1 m/s. 1 clo = 1.55 togs; 1 clo = 0.1548r; 1 clo = U/0.1548Effect of Fabric Properties on Heat Transfer Fiber type and structure Yarn type and structure Fabric type and structure Finishes appliedHeat TransferHeat TransferStandard Test Methods CAN/CGSB-4.2 No. 70.1 94, Thermal insulation performance of textile materialsASTM D 1518 85, Thermal transmittance of textile materialsThermal Insulationcold platehot platespecimenProcedure 1cold platespecimenhot plateProcedure 2cold platecold platespecimenspecimenhot plateGuarded Hot PlateThermal 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:P = thermal conductivityVc = thermal capacityThe lower the value of (b), the warmer the feelingb = (PVc)1/2[Ws1/2/m2K]Alambeta: measurement of transient and steady-state thermo-physical propertiesMoisture 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 EvaporationWater-Proof FabricOUTERINNERBreathable Fabricwater vapourLiquid waterMoisture TransferFactors Affecting Moisture Transfer Fiber type and structure Yarn type and structure Fabric type and structure Finishes appliedMoisture TransferStandard Test Methods CAN/CGSB-4.2 No. 49 99, Resistance of materials to water vapour diffusionASTM 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 materialsASTM D 4772, Standard test method for surface water absorption of terry fabrics (water flow test method)AATCC Method 79, Absorbency of bleached textilesWATER VAPOUR DIFFUSIONSweating Guarded Hot PlateWater 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 bodyWater-proof: does not allow any penetration of water from either side to the other.Shower-proof, Rain-proofAIRwater dropHydrophilicCotton (attractive surface)AIRwater dropHydrophobicOlefin (repulsive surface)Factors Affecting Water Resistance and Repellency Fiber type and structure Yarn type and structure Fabric type and structure Finishes appliedWater Resistance and RepellencyWater 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 testImpact penetration testerRain tester Hydrostatic pressure testerAir PermeabilityIt 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 PermeabilityFactors Affecting Air Permeability Fiber type and structure Yarn type and structure Fabric type and structure Finishes appliedStandard Test Methods CAN/CGSB-4.2 No. 36 M89, Air permeabilityASTM D 737, Air permeability of textile fabrics