Operative Temperature• A biophysical index of thermal sensation and discomfort.• Operative temperature is also known as dry radiant

temperature or radiant temperature. It is defined as a uniform temperature of a imaginary black

enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual non-uniform environment.

Operative temperature can be defined as the average of the mean radiant and ambient air temperatures.

The instrument used for assessing environmental thermal comfort in terms of operative temperature is called a eupatheoscope and was invented by A. F. Dufton in 1929.

• Mathematically, operative temperature can be shown as;• To = hr tmr + hc ta

hr + h c

where, • hc = convective heat transfer coefficient

• hr = linear radiative heat transfer coefficient

• t a = air temperature

• tmr = mean radiant temperature

• Application: Operative temperature is used in heat transfer and thermal comfort analysis in transportation and buildings.

Humid Operative Temperature

• The humid operative temperature is the temperature of a uniform enclosure,with a humidity of 100 percent.

• It was given by Gagge in 1981.• Much effort has gone into deriving a single index

that will indicate environmental heat stress for humans.

• Environmental variables that affect heat stress are radiation , temperature, vapor pressure.