Valeooscope - Air Conditioning System Thermal comfort loop

6.2. Physiological comfort The notion of physiological comfort is highly subjective. Nevertheless, our perception of hot atmospheres is determined by the temperature and the humidity of the air. The definition of comfort refers to certain combinations more often than others. For example, dry air is more comfortable than humid air. This is the perfect example of apparent temperature. The figure below illustrates how humidity influences our perception of temperature, and therefore, of our comfort.

Analyses of the behaviour of vehicle occupants have identified the average comfortable temperatures. The designers of air heating and cooling systems use these values to define the characteristics and design of their systems. The following figure illustrates the need to adapt average foot and head temperatures to the tempe- rature outside the vehicle. Note that, in winter, the difference between the head and foot temperatures produced by the system is greater, in order to achieve optimal comfort for the occupants.

Human perceived temperature versus humidity

Perceived Temperature (°c)

70

40 50 60

100

20 30

Humidity (%)

80

60

0 10

40

21

20

24

27

29

0

Temperature (°c)

32

35

Heat distribution versus seasons

34

Temperature at feet level

33°C

32

30

28

26

Temperature at head level

25°C

24

22

20

-30

0

10

20

30

40

50

-20 -10

13