Temperature globe

Heat. Personal monitoring of the environmental conditions which impose a heat stress on a worker is impractical, so fixed station measurement of such parameters as wet bulb globe temperature are usually made (see Temperature measurements). These stations are carefully selected so that the results, plus worker location and workload data, can be combined to yield an overall heat stress estimate. Heat strain, the effect on the human, can be estimated from core body temperature, but this is usually only a research tool. 

Does the employer regularly monitor heat eonditions (i.e., dry bulb or adjusted dry bulb temperatures) to determine the risk of heat stress and to establish appropriate work/rest regimens (Note Wet bulb globe temperature is not the most appropriate measure of environmental heat eonditions when employees are wearing vapor impermeable proteetive elothing.)... 

ISO EN 7243 Diagnostic method for hot environments Hot environments Elstimation of the heat stress on working man, based on the WTlGT index (wet hulb globe temperature... 

The ISO philosophy for the assessment of hot environments is to use a simple, fast method of monitoring the environment, based on the wet bulb globe temperature (WBGT) index (ISO 7243). If the WBGT value exceeds the provided reference value, or if a more detailed analysis is required, then ISO 7933 provides an analytical method of assessment. 

Corrected effective temperature An empirical comfort index that uses the dry bulb, wet bulb, and globe temperatures and the relative air velocity in a space. 

Globe temperature The temperature of the surroundings (mean radiant temperature) as recorded by a black globe thermometer. 

Black-Globe temperature the temperature inside a hollow copper sphere 15.2 cm (6 in.) in diameter painted matt-black on the outside and containing a thermometer inserted so that its sensing unit is at the center of the sphere. This temperature is a measure of the intensity of radiant heat from the surroundings or the sun. 

Wet-bulb globe temperature Index a mathematical expression... 

Stafford Country Public Schools, Office of Safety Security (unknown year) Wet Bulb Globe Temperature Index (WBGT). Available at www.pen.kl2.va.us/Div/Stafford/Safety/wetbulb.html (accessed 13 April 2006). 

A more complex and well-known climatic index is the Wet Bulb Globe Temperature (WBGT), used as a heat stress indicator. The WBGT is a composite temperature used to estimate the effect of temperature, humidity, and solar radiation on humans. It is used by industrial hygienists, athletes, and the military to determine appropriate exposure levels to high temperatures. It is derived from the following formula ... 

Soot formation is commonly observed in the pyrolysis or combustion process of simple hydrocarbons and coals. Soot does great harm to people s health through carcinogenic effects and the presence of soot in air also leads to visibility reduction, globe temperature decrease, and acid deposition. Soot can suspend in the air for up to 1 month and can be delivered by wind to distant places, which causes wide range pollution. Soot suspended in flames is important to combustion systems because it will significantly enhance radiative heat transfer due to its large surface area (Fletcher et al., 1997). 

An index discussed later is the wet-bulb globe temperature (WBGT). When making wet-bulb readings for WBGT, the wet-bulb thermometer must be stationary and not involve moving air. 

Wet-Bulb Globe Temperature Index Researchers developed the WBGT index as a simple-to-use method for determining if military troops were likely to suffer from heat illnesses in hot environments. The WBGT index requires only two or three measurements wet-bulb (static) temperature (WB), dry-bulb temperature (DB), and globe temperature (GT). One can compute WBGT values from one of two equations, depending on the presence of a solar load. 

The Wet Bulb Globe Temperature index (WBGT) can be calculated from the formula ... 

WBGT = 0.7 X natural wet bulb temperature + 0.3 x globe temperature... 

A globe thermometer is a thermometer inserted into a matt black copper globe. This provides a measure of radiant (infra-red) heat energy. A simple eqiration gives the mean radiant temperature from the globe temperature. Air velocity, if it is in one clear direction, can be measured with a vane anemometer otherwise a Kata thermometer or hot-wire anemometer can be nsed. The Kata thermometer is warmed and then the time for temperatiue drop between two poirrts observed. A chart gives the airflow. 

For a hghtly clothed man, with mean radiarrt temperatrrre t, black-globe temperature tg, and dry bitlb temperature t (all in °C), airvelocity v in metres/mirr, artd vaponr pressure of water in air, p in mbar ... 

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