Experimental And Theoretical Research On Recommended Air Velocity Under Warm And Hot Environment

As one of the six main factors which would influence thermal sensation, the effects of air velocity are both advantageous and disadvantageous. By literature review, it’s found that rising air velocity could effectively decrease human thermal sensation, and improve human thermal comfort. But unsuitable air velocity would cause uncomfortable draft. Based on the research context, a further research on the compensation effect of air velocity was carried out to find out the relationship between thermal discomfort and discomfort caused by air flow by taking gender difference into account, and a group of recommended air velocity under warm and hot environment would be achieved finally.Theoretical and experimental research was taken out in this thesis. Both subjective questionnaire votes and objective physiological parameters were recorded in the experimental research. There were 10 males and 10 females subjects participated in the experiments which concluding 6 thermal conditions(air temperature vary from 30 to 34℃, air velocity vary from 0.6 to 1.4m/s) and 150 hours of exposure in total. A mathematical model called “Human Thermal Physiological Model” was used in the theoretical research, which was an important finding of our research team recently. A theoretical analysis on human thermal response under warm and hot environment was carried out by this model.Analyzing the results of the experiment, it was found that there were differences between male and female in subjective and objective thermal responses, including thermal sensation vote、air movement vote、satisfaction proportion of the environment and mean skin temperature; When air velocity was invariable, the higher the temperature, the lower the air movement vote and the number of discomfort symptoms caused by air flow; There was no significant difference between air movement vote and the time exposure to wind, but the mean discomfort symptoms caused by air flow will increase logarithmically by time.Using mean skin temperature data recorded in experiment, the accuracy of Human Thermal Physiological Model was evaluated by a new method of evaluating the accuracy of population-based models, it was found that predict values of male occupants’ mean skin temperature by this mathematical model were statistically accurate, while the predict values of female occupants’ mean skin temperature were not accurate enough. After optimizing the control system of female properly,an optimized mathematical model was proposed finally, which can predict human mean skin temperature accurately in statistics and correctly reflect the gender difference.Combining the optimized Human Thermal Physiological Model and human thermal comfort regression model obtained by experiment data, equal TSV lines were drawn in warm and hot environment firstly in order to get male and female’s comfortable air velocity zone under warm and hot environment. Then the relationship between mean skin temperature and air velocity under different air temperature was predicted by Human Thermal Physiological Model, and a concept of effective air velocity was proposed based on the change rate of mean skin temperature by increasing air velocity. Combining comfortable air velocity zone and effective air velocity together and taking the gender differences into account, a series of recommended value of air velocity was obtained which can be used in in a wide temperature range under warm and hot environment. And the result of this thesis can contribute to the improvement for national evaluation standard for thermal comfort.