The Development Of Comfort Temperature For Bedding System And Analysis Of Influencing Factors

The bedding system is composed of bedding stuff and sleepwear,generally including bed,mattress,pillow,pajama and quilt.As an essential part of sleep,the bedding system,together with the indoor environment,affects the thermal comfort during sleep.The research on thermal comfort at home and abroad is mainly focused on the human body in the awake state,while the research on the sleeping state is relatively less.It should be noted that the physiological parameters and heat transfer modes of the human body in the sleep state are different from those in the awake state.Therefore,it is of great significance to study the effect of the bedding system on thermal comfort in the sleep stateThe purpose of this study is to explore the effect of factors on the thermal comfort of sleep,including theoretical and experimental study.Firstly,this paper investigated the influence of three factors on the total thermal insulation of the bedding system,and developed empirical formulas to predict the total thermal insulation of the bedding system Secondly,the influence of human body,environment and bedding system on sleep thermal comfort was analyzed theoretically,and the thermal balance equation in the awake state was modified to establish the theoretical prediction model for sleep thermal comfort;Thirdly,the prediction model was validated by human sleep experiment,the relationship between the total thermal insulation of the bedding system and the lower limit of sleep comfort temperature was obtained,and the impact of each factor on the comfort temperature was analyzed through the parametric study.The results are shown as follows(1)The type of fillings had a significant effect on the total thermal insulation of the bedding system.Compared with the silk and wool fillings,the thermal insulation ofbedding system with down filling was greater.When the filling weight was small,the thermal insulation of bedding system with wool filling was higher than that of silk filling;when the filling weight was large,the thermal insulation of bedding system with silk filling was higher than that of wool filling.The total thermal insulation increased with the increasing of the filling weight,and the growth rate slows down gradually.The total thermal insulation in crouching sleeping posture was the largest,and that in supine sleeping with arms outside was the lowest,and no difference was detected between the supine sleeping and sideways sleeping postures for different filling weights.Logarithm formulas were successfully established to quantitatively evaluate the effect of the filling material,the filling weight of quilt and the change of sleeping posture on the total thermal insulation of bedding system(2)Based on heat balance equation of human body,this paper analyzed the specific influence on sleep thermal comfort from three aspects,i.e.,bedding system factors including the thermal insulation of bedding system and permeation efficiency,human factors including metabolic rate,body surface area,skin temperature and skin wettedness,environment factors including ambient temperature and relative humidity.A thermal comfort model was developed to predict the ambient temperature of the bedding system with a specific thermal insulation to keep a sleeper comfort during the whole night.When the total thermal insulation of the bedding system increased by lclo,the ambient temperature corresponding to comfortable sleep decreased by 5.2℃(3)Sleep experiments showed that there were obvious individual difference in the sensitivity of cold during sleep.Women were more sensitive to cold environment and preferred a neutral and warm environment.Men could endure lower temperature and preferred a neutral and cold environment to maintain the environment temperature required for comfortable sleep.The comfort temperature for women was about 1.3℃ higher than that for men.The results of physiological experiments showed that the predicted comfort temperatures agreed well with the measured comfort temperature,which demonstrated the accuracy of the theoretical model.The parametric study showed that when the mean skin temperature,skin wettedness and moisture permeability index increased,the corresponding comfort temperature increased;whereas the corresponding comfort temperature decreased when the relative humidity of the environment increased.