Sensation of Climate and Discomfort Index

Abstract

Applying the equation of turbulent transfer to the heat loss from a human body, an equation is obtained which describes that the heat loss is proportional to the gradient of total heat (enthalpy) . But for practical purposes the heat loss is assumed to be proportional to the difference of total heat, and a transfer coefficient is introduced instead of eddy diffusion coefficient. When it is comfortable, i. e. in spring or autumn, the heat loss is considered to be the normal. An index (=comfort index) Ic is defined as a ratio (heat loss)/(normal heat loss), and also another index (discomfort index) ID is efined as ID=1-Ic. Thus ID will denote the rate of disturbance for the development of normal heat loss. ID will also be used as a climatic index ; thus adopting reasonable values for the total heat, it is found that
(i) ID>30% corresponds to the climate : without clothes, (ii) 30%>ID>10% : summer clothes,
(iii) 10%>ID>-10%: spring clothes, (iv) -10%>ID>-30%: winter clothes, (v) -30%>ID: protecting outfit against cold.
The effect of wind on the index is readily taken into account by assuming the square root law of wind velocity for the coefficient, and it is shown explicitly that the effect is larger in the cooler climate than in the warmer. The difference in the indices due to clothing is also discussed and the relation is proved to be linear. Finally two charts are given, one (Fig. 1 in the text) denoting relations between (dry-bulb) temperature, relative umidity, wet-bulb temperature, enthalpy, discomfort index, and wind velocity, and the other (Fig. 2 in the text) denoting the relation between our index ID and hitherto used index ID'.