Research On Calculation Methods Of Clothing Insulation And Thermal Comfort Based On Infrared Thermal Imaging Technology

With the rapid development of intelligent technology,in order to achieve real-time computer control,it is necessary to estimate clothing thermal insulation and thermal comfort of occupants in real time through non-contact measurement.Clothing insulation is an important factor affecting human thermal comfort,it is usually a fixed value when the clothing ensemble are determined in the standard.However,real clothing insulation is greatly affected by the environment and activity level(metabolic rate).Thus,the heat flow method for obtaining clothing insulation through thermal equilibrium between the skin layer and environment was proposed.Later,a non-contact method for easy acquisition of clothing insulation was proposed.The method was implemented via infrared imager.However,the above methods are mostly theoretical studies that have only been validated in limited conditions,and do not fully consider the impact of different activity levels and different clothing in winter and summer.They have certain limitations.In this paper,above methods are compared and analyzed based on experiment data.Three activity levels are considered,sedentary(1.0 Met),walking at speed of 0.8 m/s(1.8 Met),and 1.2 m/s(2.6 Met).The feasibility and accuracy of above methods are analyzed by comparing the PMV calculated by the clothing insulation with the actual thermal sensation(TSV)of the subjects obtained by questionnaire.The reasons for the deviation are analyzed and the method is corrected in this paper.Subsequently,this paper proposes a method for calculating the clothing insulation based on the heat exchange analysis of the two-node model,which verifies the accuracy of the modified non-contact method.The results shows that the non-contact method based on infrared technology is the closest to the questionnaire in predicting the thermal comfort of occupants in different conditions.The average deviation of thermal sensation under multi-layered dressed in winter is 0.46 scales,and the average deviation of thermal sensation under single-layered dressed in summer is 0.36 scales.Due to the sweating effect on skin temperature,the higher the activity level,the lower the prediction accuracy.Therefore,this paper considers two sensitive factors,face and neck temperature and skin wetness,and proposes a corrected method based on characteristic skin temperature and skin wetness.After correction,the prediction accuracy of multi-layered dressed in winter has been improved by 11%,and the prediction accuracy of single-layered dressed in summer has been improved by 6%.And the predicted thermal comfort using the two-node model is closest to the corrected non-contact method.This indicates that the corrected non-contact method can accurately estimate clothing insulation of occupants’ in different activity levels.It can be benefit to obtain indoor human thermal sensation and adjust and control thermal environment intelligently.