Research On Characteristics And Prediction Of Outdoor Thermal Comfort In Severe Cold Area

As city development is in a new period and general secretary Xi Jinping pointed out the urbanization strategy that cities should be more livable,outdoor thermal comfort research is imperative.Outdoor thermal comfort improvement increases the number of residents coming outdoors and the time they spend there,which is of great significance to life quality improvement and energy conservation.Outdoor thermal comfort research in severe cold areas has a late start and less improvemen compared to other climate zones.Meteorological conditions in severe cold area are quite different from those in other climate zones,so the outdoor thermal comfort results of other climate zones may not be available.Therefor,outdoor thermal comfort characteristics in severe cold area can not be accurately revealed,and it is impossible to put forward planning strategy to improve outdoor thermal comfort.This study took the outdoor thermal comfort in severe cold area as the research object,analyzed the thermal comfort characteristics by means of field research and experimental research,and discussed and established the outdoor thermal comfort prediction method suitable for cities in severe cold areas.Firstly,field research was carried out and time characteristic s of outdoor thermal comfort and the characteristic differences between different populations were analyzed.In longitudinal investigation,the changes of outdoor thermal comfort of fixed people were tracked,and the effects of outdoor meteorological param eters on thermal comfort and thermal adaptation were summarized.Thermal comfort characteristics differences among populations of different ages,genders and residence time were studied in horizontal investigation.Field research can not reveal characteristics of temperature regulation in human body.Therefore,an experimental study on outdoor thermal comfort in severe cold areas was carried out,focusing on the dynamic characteristics of outdoor thermal comfort in winter and the influence of local exposure.Combined with the actual clothing conditions summarized in the pre-investigation before the experiment,four local skin exposure experimental conditions were set up,focusing on the physiological regulation phenomenon(thermal regulation phenomenon and t he changes of local skin temperatures of 7 body parts)and psychological response(the changes of thermal sensation and thermal comfort votings)of the subjects in 0-30 minutes.It was found that local exposure in winter has a significant impact on thermal comfort in severe cold area.Then,the relationship between mean skin temperature and thermal comfort was quantitatively analyzed.Before establishing outdoor thermal comfort prediction method,the applicability of several existing outdoor thermal comfort prediction methods in severe cold area were analyzed.The influence of local exposure on the prediction perfomance was compared.The results verified the importance of local exposure to thermal comfort prediction.The key points for outdoor thermal comfor t prediction method establishment were stressed.Based on the above work,a prediction method of outdoor thermal comfort in severe cold area was established.The method included human body temperature regulation model,human thermal sensation prediction model and human thermal comfort prediction model.The human body temperature regulation model took into account the thermal comfort characteristics differences between genders and ages summarized in the field research.A simplified human body model of differ ent genders and ages could be obtained,and the skin temperature changes of 7 body parts under various local exposure conditions could be calculated.Based on the importance of local exposure to thermal comfort prediction found in previous work,thermal sensation prediction model and comfort prediction model were established.These two models could predict local thermal sensation of 7 body parts,overall thermal sensation and overall thermal comfort.Considering the thermal adaptation phenomenon and thermal comfort characteristics differences among populations summarized in the field research,the temperature setting points in each season were modified and the thermal comfort cluster coefficient was introduced to establish a thermal comfort prediction model more suitable for practical application.Field research and experimental research results were used to vertify the method,and it presented a better perfomance than existing thermal comfort prediction methods.Finally,based on the established outdoor thermal comfort prediction method in severe cold area,the urban layout optimization strategy was studied.Taking Mohe,Harbin and Shenyang as the research objects,the outdoor thermal comfort under different levels of urban planning factors(building density,building heights,building layout,coverage raito of road,grassland,forest and water)under typical annual meteorological conditions was simulated.Firstly,the change trends of outdoor thermal comfort under different factor levels in each season were a nalyzed through single factor test.Focusing on thermal comfort in winter,factor levels corresponding to higher thermal comfort level were selected for orthogonal test.The orthogonal test determined the sequence of factors,optimal scheme and significanc e of the influence on outdoor thermal comfort of various factors.Urban layout optimization strategy in severe cold area was summarized.The work of this paper is helpful for better understanding the causes of outdoor thermal comfort in severe cold areas.The outdoor thermal comfort prediction method suitable for severe cold area provides technical support for improving the outdoor thermal comfort level in the early stage of urban planning.The proposed urban layout optimization strategy is helpful to promote the improvement of residential thermal environment researching and planning in severe cold area.