Clothing Comfort Determining Factors

Clothing Comfort and its Determinants

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Dr. Muhammad Mushtaq Mangat www.mushtaqmangat.org

26/11/12

Lecture 2

Clothing Comfort Determining Factors

  Objective:

  To have an understanding about the factors

which have the ability to alter clothing comfort

Determining Factors Human body

Comfort

clothing

Environment

Interaction

  Continuous interaction among human body,

environment and clothing

  Dynamic situation

  No stable situation

  Many more external factors

Factors affecting clothing comfort

  Factors related to the wearer

  (metabolism of person, age, experiences, level of health, mental and economic position, types of activities)

  Clothing structure and chemical nature of fibers

  (fibre and yarn types, fabric structure, mechanical and thermal properties of fabric, clothing design, fitting)

  External Conditions

  (moisture, ambient and radiant temperature, wind speed)

Human body

  A complex system

  Needs intake to produce heat

  Heat is used as energy to keep running the

whole system

  Food energy is converted into thermal

energy

  Activities increases energy by using stored

fat energy

Human body: a fuel cell

 

Consumption of food is similar to combustion but not exactly

 

Combustion produces heat as by product of combustion

 

Human body needs a constant temperature for smooth running

 

Higher temperature increases the reaction rate and causes discomfort

 

Shivering increases the heat production process by utilizing stored energy (fats)

 

Not heat, no required temperature result is death

Conti…

  Source of heat is burning of glucose

  Human body breaks the glucose and gets

energy

  Produced energy is always higher than

required

  Excess energy needs to be removed

Conti…

  Chemical reaction in human body are

exothermic due to breaking of bonds

  Human body also receives energy from

environment, through radiation, conduction and convection share is small

  Most suitable temperature for working of

human body is around 37 °C

Heat Production Due To Exercises

Dog has fewer sweat glands, keep mouth open to release extra heat

Human Body Physiology

Human Body and Thermal Transfer

 

Humans are bipedal while animals are quadruped.

 

Human has 40% less expose to radiation as compared to animals

 

Human head is at height and experiences cool and wind blowing more than other parts of body.

 

Human skin has four layers and the inner parts are bones, muscle, fat and finally skin.

 

More than 80% heat is produced in muscle

 

Occurrence of heat production and its consumption is concurrence process

 

Always difference in heat production and consumption

 

Heat production and consumption is regulated by the brain.

 

Skin quality, thermal receptors, radiation, evaporation, sweat glands, shivering process, metabolism rate, and experience affect this regulation.

Amount of Heat

  Human body produces heat depends upon

the intake at rest position

  Average human takes 2400 Kilocalories,

  It is equal to 2791.2 Watt or 116.3 Watts per

Hr

  Commonly 100 Watts is taken in general

  Human body area is between 1.6-1.8 m2

  116/1.6= 72 W/hr or 116/1.8= 64 W/hr

Heat Generation and Activities

  Human metabolic rate is measured in Met, a

seated person Met is equal to 1

 

1Met = 58 W/m2 (356 Btu/hr)

  Human body area= 1.6-1.8 m2

  Total heat produced= 1.6*58= 92 W/hr-

1.8*58=104 W/hr

  Commonly 100 W/hr for whole body or 70 W/hr

per meter area of human is used in literature

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Environment and Human Body [2]

  Human body

 

exchange heat with environment through conduction, radiation, convection

  Sweat generation

and evaporation is also a method to dissipate heat

http://hyperphysics.phyastr.gsu.edu/hbase/thermo/ imgheat/bodycool4.gif

Human Body Temperature Control

 

Neural feedback mechanisms controls the temperature of human body through the hypothalmus

 

It is based on sensors attached with hypothalmus

 

Sweating and shivering are two main action which body takes after sensing the variation of temperature

 

Vasoconstriction to decrease the flow of blood in case of winter

 

Vasodilation to increase the blood flow in case of high temperature

 

Sweating to decrease the skin temperature and shivering to increase the skin temperature

 

Erection of hairs on skin increase the thermal resistance under cold conditions [3]

Human body temperature controller [4]

[5]

Human Body Heat Exchange [2]

Cooling of Body [2]

Heat Transfer and Human body [6]

Shade for Cooling

Human temperature Variation [7]

Chart showing diurnal variation in body temperature, ranging from about 37.5 °C from 10 a.m. to 6 p.m., and falling to about 36.3 °C from 2 a.m. to 6 a.m.

Clothing and Comfort

  Clothing is our second skin

  Clothing helps controlling the heat

exchange between human body and environment

  People adjust clothing to have a better

thermal comfort

  Every clothing has a distinct nature to control

heat flow from one side to other side

H&M transfer and Clothing [8]

Moisture Flow through Clothing [9]

Schematic diagram of liquid water and moisture transfer of clothing system [10]

Primary Function of Clothing

  Thermal insulation

  Support to transfer moisture from skin to

environment

  Protection from radiation

  Social satisfaction

  Safety of human body from injuries

  Facilitate for better functioning

Clothing and Thermal Insulation

  Clothing provides thermal resistance

  Thermal resistance is measured in “clo”

Clo= 0.155 m2K/W

  It is zero for a naked person and 1 for an

ordinary suit

  It depends upon the moisture, structure and

fiber contents of clothing

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Environment

  Environment is third factor in clothing

comfort

  Three main elements of environment:

  Temperature (ambient, globe)

  Humidity

  Wind speed

Environment Temperature

  Heat flow due to temperature difference

through conduction. Human body remains in touch with adjacent things directly or through clothing

 

Air wind affects the heat transfer through convection process

  There is a net difference of heat transfer

through radiation

Humidity Ratio Humidity affects the moisture transfer from skin to environment Higher humidity will reduce the difference in humidity level between skin and air Skin becomes unable to transfer heat through evaporation and human body temperature increases Clothing also reduces the moisture flow Clothing having ability to transport moisture from skin to environment are much liked

Summary

  Thermal comfort is highly dependent upon the

heat produced and heat dissipate from human body

  A balance is required for a better thermal

comfort

  Balance is achieved by increasing heat

production (activities and food, increasing ambient temperature, heavy clothing to provide insulation), or heat loss (decreasing ambient temperature, high wind to take moisture, minimum clothing)

Activities

  Calculate total clo of your clothing and

compare with others

  Measured clo values of your clothing under

different temperature

  Is there any linear relationship between these

two

 

References [1]Robert E. Peary in the clothes he wore when he explored the North Pole, Source: http://www.bing.com/images/search?q=clothing+of+north+pole +&view=detail&id=1E6D08E67DD13306D836128EE217E4094FCC9E75&first=61&FORM=IDFRIR [2] http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/imgheat/bodycool4.gif [3] http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatreg.html [4] http://en.wikipedia.org/wiki/File:Illu_diencephalon_.jpg [5] Gersˇak, J., & Marcˇic, M., Development of a mathematical model for the heat transfer of the system man – clothing –environment. International Journal of Clothing Science and Technology, 2007. 19: p. 234-241. [6] Bartiz, M., et al., Human Body Tempertaure to Analyze the Comfort during Manufacturing Process, in International Conference 6th Workshop on European Scientific and Industrial Collaboration on promoting Advanced Technologies in Manufacturing WESIC‘082008: Romania. [7] http://en.wikipedia.org/wiki/Thermoregulation [8] http://www.bing.com/images/search?q=heat+and+mass+transfer+through +clothing&view=detail&id=C36BC550AAF5B04C53030467CB0F6E90063CF386&first=31&FORM=IDFRIR [9]Gersˇak, J., & Marcˇic, M., Development of a mathematical model for the heat transfer of the system man – clothing –environment. International Journal of Clothing Science and Technology, 2007. 19: p. 234-241. [10] Satsumoto, Y., Murayama, C., and Takeuchi, M. , Effect of Moisture Sorption of Underwear Material on Clothing Microclimate in a Hot Environment. Heat Transfer-Asian Research, 2009. 38(1). [11]Source: http://www.engineeringtoolbox.com/clo-clothing-thermal-insulation-d_732.html [12] Source: INNOVA Air Tech