Algorithms for the calculation of the projected area factors of seated and standing persons

Moderate thermal environments, other than being affected by the mutual radiative heat exchange at low frequency among the internal surfaces, are often characterized by the presence of high intensity sources, that is, radiant sources showing a small area, a high emission temperature and a strongly directional beam. The sun's direct radiation can be considered to be among these radiant sources. In these cases, the computation of the mean radiant temperature and, consequently, the evaluation of the thermal comfort conditions, require knowledge of the “project area factor”, fp, of the subject. Moreover, the fp parameters are also applicable to derivation of the shape factors between subjects and the surrounding surfaces. For a manual evaluation of the projected area factors, a well-known set of graphs is available. But, when using computerized procedures, the handling of graphs can lead to troublesome operations and could involve reading errors. To avoid problems, we have developed two simple polynomial algorithms, founded on earlier data, for the automatic calculation of the projected area factors of seated and standing persons. A validation of the algorithms is also reported through the paper, for selected cases.