What is operative temperature? How is it related to the mean ambient and radiant temperatures? How does it differ from effective temperature?

Operative temperature is a measure of the thermal conditions experienced by a person in an indoor environment. It is a weighted average of the air temperature and the mean radiant temperature, considering radiation and convection heat exchange within the space. The purpose of calculating the operative temperature is to accurately predict the thermal comfort of people indoors.

Operative temperature is related to the mean ambient and radiant temperatures through a weighted average. The mean ambient temperature refers to the average air temperature in the room, while the mean radiant temperature represents the average temperature of the surrounding surfaces that emit or absorb radiation. The operative temperature takes into account both air temperature and mean radiant temperature to provide a better representation of the actual thermal conditions experienced by a person in the indoor environment. The operative temperature can be calculated using the following formula: \[ T_{op} = (h_c * T_a + h_r * T_r) / (h_c + h_r) \] where: - \(T_{op}\) is the operative temperature - \(T_a\) is the mean ambient (air) temperature - \(T_r\) is the mean radiant temperature - \(h_c\) is the convective heat transfer coefficient - \(h_r\) is the radiative heat transfer coefficient

Effective temperature is another measure of thermal comfort in an indoor environment. It represents the temperature of a uniform environment with the same humidity and air velocity where a person would feel the same level of overall heat loss as in the actual environment. The effective temperature takes into account the combination of air temperature, mean radiant temperature, relative humidity, and air velocity.

The main difference between operative temperature and effective temperature is in the factors they consider when determining thermal comfort. Operative temperature takes into account only air temperature and mean radiant temperature, while effective temperature considers additional factors such as relative humidity and air velocity. Operative temperature is focused on radiation and convection heat exchange, while effective temperature provides a more comprehensive assessment of overall heat loss in a given environment. In summary, the operative temperature is a measure of thermal comfort that considers both the mean ambient (air) temperature and mean radiant temperature, providing a more accurate representation of the actual thermal conditions experienced by a person in an indoor environment. On the other hand, effective temperature offers a broader view of thermal comfort by including factors such as relative humidity and air velocity.