From a physiological point of view, the very early endeavour to
understand the regulatory system of the human body temperature
dates back to Blagden [12] with his use of a thermometer in a
heated room. His experiments were about human ability to endure
high temperatures. In 1885, Richet found the ideas of brain
regulations in temperature understanding. In the 1930s, Gagge
started working on human heat exchange processes [13–16] and
he predicted thermal comfort for ASHRAE in 1969 based on a
thermal equilibrium approach [17].
In engineering, the first idea of body heat transfer was
introduced by Sir Leonard Hill, Barnard [18]. In 1914 he made a
big thermometer which integrated the influence of mean radiant
temperature, air temperature and air velocity. Furthermore,
Dufton [19] defined the equivalent temperature (Teq) in 1929. This
equivalent temperature, however, was no longer applied because