Comparative analysis of methods for determining the clothing surface temperature (tcl) in order to provide a balance between man and the environment

Abstract

The PMV (Predicted Mean Vote) is an index which shows the thermal sensation of a large group of people exposed to the same environment. However, discrepancies are found between the PMV model and thermal sensation responses obtained in field studies. One of the components for the calculation of PMV is clothing surface temperature (tcl), which can be a factor which contributes towards these discrepancies. Therefore, the aim of this article was to show tcl influence on the PMV index. For this, the calculation of tcl was done in two ways: the first was through the algorithm presented in the Annex D of ISO 7730 (2005) (Algorithm 1) and the second way was through Newton's Method (Algorithm 2), on a group of welders of a metal-mechanic industry. After calculating tcl in these two ways, (algorithms 1 and 2), the two values obtained for tcl were compared and the results were not the same. Consequently, different values for tcl generate different results for the PMV. Newton's Method, having quadratic convergence, is more precise for the calculation; therefore, the suggestion is to use this method to determine tcl since this is a variable with direct influence in determining the PMV. Relevancy to industryWhenever it is possible to determine the PMV and when this result is closer to people's responses to thermal sensation, one can provide a more appropriate environment to users in order to have Thermal Comfort and, principally, to avoid Thermal Stress.