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Modelling outdoor thermal comfort of humans performing physical activity: applications to health and emergency heat stress preparedness

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Title: Modelling outdoor thermal comfort of humans performing physical activity: applications to health and emergency heat stress preparedness
Author: Vanos, Jennifer; Warland, Jon; Gillespie, Terry; Kenny, Natasha
Department: Department of Land Resource Science
Program: Land Resource Science
Advisor: Warland, Jon
Abstract: Humans are tightly linked to their thermal microclimatic environments, yet few studies have evaluated the outdoor thermal comfort of users performing physical activity. The purpose of this research was to critically review, assess, and apply findings using the COMFA ('COMfort FormulA') human energy budget for users performing physical activity outdoors. Research objectives were: to apply an improved multi-segmented skin temperature approach to the COMFA model; to evaluate its accuracy in predicting actual thermal sensation (ATS); to implement techniques to account for human behaviours associated with clothing and metabolic variations; to spatially assess human energy budget moderating effects of urban parks; and to investigate extreme heat stress situations. To evaluate modelled mean skin temperature (T_sk), field tests were conducted on subjects performing 30 minute outdoor sessions of steady-state moderately intense activity (cycling and running). The model accurately predicted T_sk, showing significantly strong agreement (r = 0.859, p<0.01). ATS votes displayed significantly strong rank correlation with budget scores calculated using both measured and predicted T_sk (r_s = 0.507 and 0.517, respectively, p<0.01). A further improvement of Incorporating conditioning level of an individual gave more realistic estimations of metabolism for budget estimation. Adopting a new relative wind velocity (v_r) equation, which incorporates wind to body angle, revealed errors of the original v_r equation in the modelling of convective heat loss and T_sk. Application of the COMFA model in urban spaces showed that energy budgets were more closely correlated to incoming solar radiation (r = 0.941) than air temperature (r = 0.490), with a significantly strong linear regression found with radiation absorbed by a human (R^2=0.858). Treed greenspace was shown to strongly enhance thermal comfort the greatest, decreasing budgets on average by 25.5 Wm^2. Budget values were found to be a strong predictor of emergency dispatch calls received in Toronto during the July 2010 heat wave (R^2 = 0.86). This study has displayed the potential of the COMFA outdoor model as a new tool to make heat forecasting more meaningful to the public, emergency responders, and urban planners.
Date: 2011-11

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