Skin and inner layer of clothing

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Skin and inner layer of clothing

  1. 1. A .Tahan PhDReady Made Garment Technology Dept. Faculty of Applied ArtsDamietta University, Damietta, Egypt tahan@mans.edu.eg 1
  2. 2. Thermo-physiological Wear Comfort Due To The Heat AndSweat Transfer From Body Skin InConsequences Of The Properties Of Clothing 2
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  5. 5. Waste heat from bodyskin must be dissipatedall the time andwhenever necessary,aided by evaporation ofsweat from the skin. 5
  6. 6. Clothing has, as one of itsmain functions, the controlof heat and moisturetransfer from the body tothe environment. 6
  7. 7. The physical properties of thefabric’s material andconstruction (structure &design) as well as the physicalactivities(metabolic) of the bodyhave been considered for theway affecting the thermalproperties of the fabrics. 7
  8. 8. SkinMicroclimate and inner layer of clothing 8
  9. 9. Firstly:The passive system is such a Heatflow from the central up to the skinsurface by the conduction andvascular mechanism.With the skin layer periphery, whichtransports heat from heat producingareas within the body to skinsurface, 9
  10. 10. the heat is transferred by skinsurface to the microclimatebetween the body surfacelayer and the garment layerassociated with the exchangeof heat by process ofconduction, radiation,convection and evaporation tothe environment 10
  11. 11. Secondly,the natural control system whichcontrols the skin blood flow, sweatingand shivering necessary heat tomaintain normal body temperature forcooling.The maximum value occurs when theentire skin surface is 100% wet fromregulatory sweating. 11
  12. 12. Both depend on the evaporativepotential of the environment as afunction of• air movement,• vapour pressure gradient from the skin surface through clothing to ambient air and• the resistance of clothing against the sweat transfer of water vapour 12
  13. 13. Fig (5) 13
  14. 14. In order to be comfortablethermophysoliogically theclothing microclimate should liein the range: ◦ 35±2 c Temperature 50± 10% RH 25± 5 m/sec air velocityFabric has its insulative ability aswater and air permeability,absorbency ,wickabilityand other properties related tothermal comfort 14
  15. 15. In this aspect, a mathematicalmodel has been developed todescribe the dynamic heat andmoisture transport behaviour ofthe toddler 6 to 12 years old heattransfers. 15
  16. 16.  Textile materialsFabric physical properties:1. Weight per Unit Area2. Air Permeability3. Water Permeability4. Moisture Regains 16
  17. 17. The yarn through the Garment swellat high humidity could have a largeinfluence on the measured airpermeability for hygroscopic fibressuch as cotton, wool. RepresentedThe phenomena of TESV(Thermal Effective Specific Volume). K= f/m m3/sec .kg, 17
  18. 18. This relationship means, as wateraccumulates through void spacesof yarn-to-yarn and the fabric byhydrophilic or hydrophilicphobicgroups,there is absolutely changes in thefabric dry thermal insulation. 18
  19. 19. Effect of Fabric Construction vrs TESV (thermal insulation) cottonT dry wet moistESV S4 Fabric construction 19
  20. 20. Effect of Fabric Construction vrs(TESV) at maximum hloding water 4Thermal Effective Specific 3.5 COTTON Volume(m3/sec.m/kg) 3 C/POLY 2.5 2 1.5 1 0.5 0 S4 141 20
  21. 21. Considering1. Conduction2. Convection,3. Radiation And4. Vapour Transfer Diffusity through the garment 21
  22. 22. So the heat is produced by metabolismQm., by other way Qm = Heat dissipatedto the ambient due to the metabolic heatproduction and the rate of working,Qm = QE ± QR ± QC± QCdQE = Evaporation Heat transferQR = Radiation Heat transferQC = Convection Heat transferQCd = Conduction Heat transfer 22
  23. 23. Heat Transfer by Conduction 23
  24. 24. Qcd= AW(Ts-Ta)Ta = ambiant air temperature,Ts = skin temperatureA =surface area of garmentW = conduction heat transfer coefficient of the used material (w/m2˚C.), 24
  25. 25. Heat transfer By Convection: 25
  26. 26. The rate of transfer by convection QC isdetermined from Newton’s law of cooling QC = A1 Ѱ (Tc – TA).Where the convection heat transfer coefficientѰ (w.m2/k ) it’s values depend on• Garment fitting,• Fabric design• Nature of sweat motion through the fabric structure and 26
  27. 27. Heat Transfer by Radiation 27
  28. 28. The heat transfer by Radiation fromthe body to the ambient conditiondepends upon the mean radianttemperature. The energy radiatedfrom the body is defined in terms ofits emissive power, = 0.19038 K.m2 / w 28
  29. 29. Heat transfer By Evaporation QEit depends upon the vapourpressure difference between theskin surface ,the microclimatewith garment and thesurrounding air. 29
  30. 30. QE=A2 Φε (Ps-PA) convective heat transfer Coefficient = 6 watt/m2 hc kg / Pa..m2cC pGTρ Air vapour sweat concentration Φ Sweat transfer coefficient Cp Air specific heat transfer equal (1003.5 k j/kg. k) [33] Ps = vapour pressure at skin temperature (Ts), PA = vapour pressure at ambient temperature(TA) ambient temperature 30
  31. 31. Temperature of the skinMetabolic Rate increases Up ToFour Or Five Times Setting-restingLevelBut For Clothed Subjects It CouldFollow The Equation : Ts = 25.8 + 0.267 Ta 31
  32. 32. Skin Temperature20 21 22 23 24 25 Ta31.1 31.4 31.7 32 32.2 32.5 Ts26 27 28 29 30 31 Ta32.75 33 33.3 33.5 33.8 34.1 Ts 32
  33. 33. It was found the water vapour and heat transport characteristics of fabric depend on water vapour absorption of fibres, the porosity, density and thickness of fabrics. The final equation (25 parameters) Skin temprature Skin Pressure and and microclimate microclimate A Garment (T T ) A E R ( ps P ) M s A Body AQ (23) 1 K 0.293C 2 f 1 1 [ ]2 [ ] ( Lc Ls )( N N ) 1 2 G F M (T T )(T 2 T 2 ) C A C A Convection Garment Conduction radiation 33
  34. 34. Effect of Fabric Strcture vs Heat Transfer( watt)Cotton Fabric (6 year) wet dry moistHeat transfer (K.watt) 5 P1/1 T2/2 S4 4.5 T2/2 4 P1/1 T1/3 3.5 S4 T1/3 3 2.5 S4 2 T2/2 1.5 T1/3 1 0.5 0 100 117 120 141 Fabric structure Fig 6 34
  35. 35. Effect of Fabric Structure vs Heat Transfer Cotton 6 Year at different condition Dry RH20 Wet RH20 Dry RH50 Wet RH50 Dry RH80 Wet RH80 2 1.75 Heat Transfer (K.watt) 1.5 1.25 1 0.75 0.5 0.25 0 100 117 120 141 Fabric Structure Fig (9) COTTONthat is due to the pressure differences between theskin pressure and the ambient pressure where itreached up to 5 times the dry condition. 35
  36. 36. Effect of Fabric Structure at Different Conditions vs Heat Transfer Cotton/poly 6 Year 2.5 Dry RH20 Wet RH20 Dry RH50 Wet RH50 2 Dry RH80 Wet RH80 1.5Heat Transfer (K.watt) 1 0.5 0 117 100 141 Fabric Structure Fig ( 10 ) the contribution of blended cotton is higher than the given values by the pure cotton. This high humidity prevents rapid evaporation of liquid water on the skin, gives the body the sensation of heat, and eventually triggered the sweating in the first place also causing uncomfortable feeling for the wearer. 36
  37. 37. Conclusion 37
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  39. 39. It is important to realize that the fabricsetting as well as the fabric design(especially satin) will play an importpart for absorbing water. The transferof water by means of fabric absorptionaccording to the physical propertiesappears to be much more efficient wayto keep the water vapour pressure nearthe skin very high. Consequently theheat transfer is positively high. 39
  40. 40. It is believed that the model can notonly find applications in functionalclothing design, but also in otherscientific and engineering fieldsinvolving heat and sweat transfer inporous media. 40
  41. 41. The work presented here is only alimited set of conditions such fabricmaterial, construction ,ambientcondition and the metabolic of thehuman body . 41
  42. 42. Thank you for your interesting 42

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