What is Heat Stress Load?
Heat Stress Load, also known as Wet Bulb Globe Temperature (WBGT), is a comprehensive measure of heat stress in direct sunlight. It takes into account temperature, humidity, wind speed, sun angle, and cloud cover (solar radiation). This differs from the heat index, which is calculated for shady areas. Heat Stress Load is commonly used to assess the risk of heat-related illnesses and to determine appropriate work-rest cycles for outdoor workers, athletes, and others exposed to varying environmental conditions.How is Heat Stress Load Calculated?
The formula for calculating Wet Bulb Globe Temperature (WBGT) is: \[ WBGT = 0.1 \times T_d + 0.7 \times T_{wb} + 0.2 \times T_g \]Where:
- \( T_d \) = Dry Bulb Temperature (the standard air temperature)
- \( T_{wb} \) = Wet Bulb Temperature (measures the cooling effect of evaporation)
- \( T_g \) = Globe Temperature (measures the effect of solar radiation)
Steps to Calculate WBGT:
- Measure Dry Bulb Temperature (\( T_d \)): This is the standard air temperature and can be measured using a standard thermometer.
- Measure Wet Bulb Temperature (\( T_{wb} \)): This is measured using a thermometer with its bulb wrapped in a wet cloth. The evaporation of water from the cloth cools the thermometer, and the temperature is recorded.
- Measure Globe Temperature (\( T_g \)): This is measured using a black globe thermometer, which absorbs solar radiation.
- Plug these values into the WBGT formula to get the Heat Stress Load.
