| In recent years,underground railway is developing rapidly within cities in China.The subway has become a preferred daily means of transportation for people in population-intensive cities.However,with the increasing demand of subway and some abuses,for example overheating,lower air velocity and uneven temperature distribution in carriages,are gradually emerging during the daily operation.Therefore,it plays a significant role for consideration of thermal environmental needs and passengers’ thermal comfort in subway’s development.Field measurement and associated numerical simulation were adopted as the main analysis methods in this study.Firstly,the field measurement was carried out in one subway line in Zhengzhou to characterize the thermal environmental conditions in cabins and daily ridership.The research results reveal that the cabin’s temperature and relative humidity in the vertical direction are susceptible to passenger flow and show a positive correlation.The increasing ridership blocks the air movement and intensifies the unevenness of the temperature and humidity distribution in the cabin.Moreover,when the ridership reaches the peak,the most obvious temperature and relative humidity differences among 1.1m level and 1.7m level and 0.5m level will also appear.Secondly,the survey investigated 378 passengers to obtain their thermal sensation information through questionnaires.The possible influencing factors are analyzed and take a further discussion on those factors with high correlation.The results show that the passenger load reaches more than 50 people,the proportion of sultry in the carriage is increasing with the increase of passengers.when the passenger load reaches more than 200 people,the increasing ridership leads to the passengers’ thermal sensation alternate between warm and hot.Compare to the normal period,passengers are less sensitive to temperature during the peak period under the similar temperature condition.The peak temperature demand is lower than the normal period by 0.5℃,and the acceptable range is increased by 0.8℃.Finally,the physical model of the tested subway cabin was established to simulate the thermal environment conditions of the different air supply temperature and air supply speed of the half-load and full-load car models.The results show that increasing the supply air temperature will increase the unevenness of the temperaturecarriage.However,the temperature in the fully loaded carriage does not change as fast as the temperature in the half-load carriage.Due to the increasing number of passengers,the overall temperature of the compartment under the same environment is 1℃ higher than subway of the half-load,which has little influence on the air flow field of the compartment.The increase of air velocity will make the temperature field distribution more even and the average wind speed inside the carriage will also increase.Adopted PMV as the index to evaluate passengers’ thermal comfort in various thermal conditions.Taking energy conservation and adaptability into account,this study proposes reliable basis data for the air conditioning design in subway during normal and peak periods in winter. |
