Re-visitation Of The Thermal Environment Evaluation Index Standard Effective Temperature(SET*)

With the improvement of living standards,people have higher requirements for the thermal environment.A good thermal environment can not only make people feel comfortable physically and mentally,but also benefit their health and work efficiency.The thermal comfort feeling of human body to the environment is the result of the comprehensive effect of the parameters of thermal environment?air temperature,humidity,wind speed,average radiation temperature,etc.?and the parameters of human side?metabolic rate,clothing thermal resistance?on human body.Its comprehensive effect can be evaluated by the thermal comfort evaluation index.The standard effective temperature?SET*?,developed by Gagge et al.is one of the most common thermal environment evaluation indices.SET*is an equivalent temperature index that assumes that people in the actual environment have the same mean skin temperature(t_sk)and skin wettedness?w?as those in an imaginary standard environment.Although the PMV index is widely applied,the SET*model is more complex and considers a greater amount of parameters.The PMV is originally based on the heat balance equation in close to neutral conditions and is only valuable for predicting steady-state comfort responses.By contrast,the SET*model takes all basic thermoregulatory processes and skin wettedness into consideration,which has greater application potential.The previous studies focused on the application of SET*but lack in-depth study of its internal mechanism as well as its accuracy and applicability verification.Although the SET*model considers the effect of various parameters and is fairly accurate at rest and at low exercise intensity,both the rationality of its calculation method and the limitation of its applicable conditions affect its practicality and accuracy.If there are problems in the application scope or internal operation mechanism of the indicators,the final evaluation and analysis results will be affected.There are a lot of intermediate variables and logical relations in SET*index.By studying its internal mechanism,we can find out the existing problems and revise them according to the latest research results or experimental data.The main research contents of this are as follows:The sensitivity of parameters affecting SET index was studied by orthogonal experiment.The characteristics of SET*index are compared with other commonly used therm al comfort evaluation indexes.Using theoretical analysis,we find that certain problems exist in the calculation and hypothesis of the existing SET*model:?1?It is inaccurate to assume that a human subject in the standard environment has the same heat e xchange at the skin surface as in the actual environment,if the metabolic rate is different in the actual environment.?2?It is difficult to find a value for the equivalent air temperature?SET*?of the standard environment in which a subject has the sam e mean skin temperature and skin wettedness as in the actual environment based on the two-node model.A modified calculation method for an improved SET*model is proposed based on the results of theoretical analysis and experiments.As a result the predict ion accuracy of SET*is improved,particularly in the high metabolic rate region.The improved SET*model shows better performance for the evaluation,design,and control of the thermal environment.