and Cooling technology Page 3
to ventilation and air conditioning technology
Room climate plays a significant role in the well-being and working capacity
of human beings. Observation has revealed an air quality range within which
people generally feel at their best. This range is known as the comfort range
and is mainly characterised by the components represented in Fig. 1.
Fig. 1 Most important components of comfort
||t1 = Room air temperature
t2 = Radiation temperature
= Air humidity
v = Air velocity
thermal comfort are not the individual components, but rather their "joint effect".
In this way air temperature and heat radiation (wall temperature) can to some
extent mutually compensate for one another, or a relatively high ambient temperature
can be made tolerable by a light increase in air velocity, etc.
In addition to those mentioned above, many further factors influence comfort.
Some examples include air purity, noise level, electrostatic state of air and
clothing, age, gender, habits, type of work, etc. Thus we can see that no strict
boundaries can be plotted for the comfort range. Nevertheless, for normally
clothed, seated persons, or those undertaking only light physical activity,
certain average values have been determined. Some of them will be clarified
in the following.
1.1.1 Room air temperature
For our central European climate, hygiene specialists generally recommend a most
favourable room air temperature for normally clothed, seated people not carrying
out physical labour, of 20 ... 21°C in winter, and of 21 ... 22°C in summer at
an average outside temperature (ca. 24°C). The reason for the higher temperature
in summer is that people generally dress more lightly at this time, and thus require
a higher ambient temperature at the same body surface temperature in order to
maintain the same amount of heat dissipation to the surroundings.
The room air temperature of 20 ... 21°C in winter can only be regarded as a rough
average, and only applies where their is no room air movement. Where the air is
in movement, which is always the case in ventilated areas, this results in a cooling
effect, which can be unpleasant. Thus, a room temperature of 22°C is recommended.
Experience also shows again and again that women feel the cold more readily than
men. The same applies to older people (over 40 years) in comparison to younger.
It is thereby advisable, under certain circumstances, to heat rooms primarily
frequented by women or older people at a temperature which is 1 K higher.
On hot summer days, when the outside temperature climbs to 28 ... 32°C, and when
people clothe themselves more lightly, a room temperature of 21 ... 22°C will
generally be found to be too cold. This is especially the case when one only stays
in such areas (department stores, theatres, assembly halls, etc.) for a short
time. On hot summer days it is therefore recommended to raise the room temperature
in relation to the outside temperature (see Fig. 2).