Wet Bulb Globe Temperature (WBGT)

The wet bulb globe temperature can be used to measure general heat-stress index

The Wet Bulb Globe Temperature (WBGT) can be measured by 

  • the black globe temperature 
  • the natural wet-bulb temperature
  • the shade air temperature

Outdoor with Solar Radiation

The Wet Bulb Globe Temperature (WBGT) for outdoor conditions:

WBGT = 0.7 Tnwb + 0.2 Tg + 0.1 Ta                                (1)

where 

WBGT = the Wet Bulb Globe Temperature (oC)

Tnwb =  the natural wet-bulb temperature (oC)

Tg = the black globe temperature (oC)

Ta = the (shade) air temperature (oC)

The black globe thermometer (Tg)

A 150 mm (6 inch) black globe with a thermometer located at the centre.

Represents the integrated effects of radiation and wind.

The natural wet-bulb temperature (Tnwb)

A thermometer with its bulb covered with a wettened cotton wick supplied with water. Evaporation cools the thermometer. Not shielded from wind or radiation.

Represents the integrated effect of humidity, wind and radiation.

The (shade) air temperature (Ta)

Measured by a thermometer shielded from radiation.

Indoor - with negligible Solar Radiation

The Wet Bulb Globe Temperature (WBGT) can be calculated for indoor conditions as 

WBGT = 0.7 Tnwb + 0.3 Tg                            (2)

Related Topics

  • Physiology - Human physiology, air quality and comfort temperatures, activity and metabolic rates, health effects of carbon monoxide and more
  • Air Psychrometrics - The study of moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content

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