The Operative Temperature Transducer MM0060 enables you to evaluate the effect that objects/surfaces of varying temperatures have on the body. Normally, the amount of heat given off by a human body through radiation is approximately the same as the amount of heat given off by convection. Therefore, a simple air temperature measurement is a bad indication of the thermal environment. Operative temperature takes both radiation and convection into account and is therefore a much better indicator. Many of the standards used today recommend measuring the operative temperature. Operative temperature (°C) is defined as the uniform temperature of a radiantly black enclosure in which an occupant would exchange the same amount of heat by radiation and convention as in an actual non-uniform environment.
Evaluation of Thermal Comfort
The temperature value from this transducer enables you to evaluate the thermal comfort and calculate PMV values according to ISO7730. PMV values are calculated using humidity, air velocity, Clo. and Met. rates without having to measure the mean radiant temperature (tr) (which is often a difficult parameter to obtain).
Evaluating the energy consumption of a building, the temperature difference between the indoor and outdoor environments must be measured. The operative temperature is commonly used to provide the indoor temperature as it takes both the air- and radiant temperature into account.
Transducer Design
Four major factors were taken into consideration during the design of this transducer:
Size
The size has been chosen so that the ratio between heat loss by radiation and by convection is similar to that of the human body. The human body has an effective radiation area of only 0.7 times its surface area (due the insides of the arms and legs radiating against the body). If the transducer had the same surface area as the human body, its simple shape would lose 1.4 times more heat by radiation than a human body. However, the convection heat loss per unit surface area increases as the size of an object is reduced. By reducing the size of the transducer, the mean radiant temperature and air temperature have the same weighted influence on the transducer as on a person.
Shape
The shape of the transducer is determined by the need to obtain the same angle factor to the individual room enclosures as for a human being. This has been achieved by using an ellipsoid shape.
Color
The transducer's color and emission coefficient have been chosen so that the long-wave radiation absorbed by the transducer is the same as that of both a naked and a dressed person. It is not possible to simulate people in both dark and light colored clothing for short-wave radiation. The grey color chosen simulates both naked people and people dressed in light colored clothing.
Orientation
People do not maintain the same posture. For this reason, the transducer has three settings: vertical, 30° from the vertical, and horizontal, which represent the body in the standing, sitting and lying positions respectively.
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To be used with Thermal Comfort Datalogger 1221
Download MM0060 Product Data Sheet
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