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Thermal Comfort - Coggle Diagram

- - - - physical condition of environment
        
        perceived by group: room temperature, etc
        
        perceived by individual: MRT, etc
    - - "asking" activity
        
        POE
        
        the building is already built and occupied
    - - substantial majority (> 80%) of the occupants find thermally acceptable
  - - - 75 of all occupant complaints within buildings are thermal comfort related
      - the thermal environment has been shown to have up to a 10 effect on worker productivity
      - energy consumption
      - over 80 billion annually is spent to heat and cool buildings
- - - - the rate of air movement at a point without regard to direction
    - - moisture content of the air
    - - the temperature of the air at a point
    - - the temperature of a uniform black enclosure that exchanges the same amount of heat by radiation with the occupant as the actual surroundings
      - measuring all surface temperatures and calculation of angle factors is time-consuming
        
        MRT is avoided
      - formula
        
        it is a homogenous steady state area weighted average of the uncontrolled/unconditioned surface temperatures
      - the temperature at which the body would exchange the same heat by radiation
  - - - the resistance to sensible heat transfer provided by a clothing ensemble [clo] (1 clo = 0.155 m2.C/W)
      - thermo-physiological comfort
        
        the clothing material’s capacity to balance moisture and heat between the body and the environment
        
        property of textile materials
    - - the rate of transformation of chemical energy into heat and mechanical work by metabolic activities of an individual [met] (1 met = 58.2 W/m2)
      - energy released by metabolism depends on muscular activity
      - body surface for a normal adult is 1.7 m2
      - average activity level for the last hour should be used when evaluating metabolic rate due to the body’s heat capacity
- - - - heat sensor
        
        located in hypothalamus
        
        emit signals when temp. > 37 C
      - cold sensor
        
        located in skin
        
        emit signals when temp. < 34 C
      - If signals (impulses) are of the same magnitude, you feel thermally neutral
    - - heating
        
        reduced blood flow
        
        shivering
      - cooling
        
        increased blood flow
        
        sweating (evaporation)
  - - - maintaining temp. around 37 C (heat generated = heat outputs)
    - - process of determining the heat transfer between body and environment
    - - heat generation
        
        the metabolic rate (M) provides energy to enable the body to do mechanical work (W)
        
        the remainder is released as heat (M-W)
      - heat transfer
        
        conduction (K)
        
        convection (C)
        
        radiation (R)
        
        evaporation (E)
      - heat storage (S)
        
        all heats (heat generation + heat transfer) and loss rates provide a heat storage
        
        heat balance
        
        S = 0
        
        net heat gain
        
        S > 0
        
        body temp. raises
        
        net heat loss
        
        S < 0
        
        body temp. falls
    - - S = M - W - E - (R+C)
        
        evaporate heat loss (E)
        
        release of latent heat energy from the evaporation of body fluid
        
        respiration heat losses (Eres)
        
        latent (Erel)
        
        sensible (Erec)
        
        heat losses from skin (Esk)
        
        skin diffusion (Edif)
        
        regulatory sweating (Ersw)
        
        the humidity of the skin & the evaporation of water
        
        saturation rate of surrounding air (relative humidity)
        
        radiative and convective (R+C)
        
        heat loss by radiative
        
        skin temp. > temp. of surrounding surface
        
        more noticeable when sitting near a cold window (felt as "radiation draught")
        
        heat loss by convective
        
        skin temp. < dry bulb temp.
        
        at normal indoor conditions, R = C
      - air velocity is an important parameter in determining turbulence intensity a measure of draught
      - heat conduction from clothing can be transferred to the environment via convection and radiation
  - - - e.g. air temp. is 5 C and someone feels hot because uses heavily clothed
  - - - Heat produced must equal heat lost
      - Signals from Heat and Cold sensors must neutralize each other
    - - Operative temp. (to)
        
        the uniform temperature of an imaginary black enclosure and air
        
        in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual nonuniform environment
        
        calculated based on air temperature (dry
        bulb), MRT, and air velocity
      - Effective temp. (te)
        
        temperature of an environment at 50% RH that results in the same total heat loss from the skin as for the actual environment
      - Dew Point temp.
        
        temperature at which the air needs to be cooled to become saturated (at constant pressure)
        
        e.g. in order to achieve a relative humidity of 100%
- - - - +3 (hot) to -3 (cold)
  - - - -0.5 to +0.5
    - - < 10%