Numerical Research On The Changes Of Indoor Environment Parameters In Qinghai-Tibet(Golmud-Lhasa)Air-Conditioned Passenger Train In Winter

The air-conditioned passenger train operating in winter along the Qinghai-Tibet Railway located at an altitude of above 3000 meters was made new requirements,because of its special climate environment of low pressure,low temperature,hypoxia,and great daily temperature difference.The passengers in the air-conditioned passenger train operating in winter along the Qinghai-Tibet Railway were easily caused the altitude sickness because of the low temperature,low pressure,hypoxia and high CO₂ concentration inside the train,which resulted in influencing the thermal comfort of the passengers.So it has great practical significance on the air-conditioned passenger train operating in winter along the Qinghai-Tibet Railway to study the changes of indoor environment parameters and passenger thermal comfort inside of it.The main works of the paper are as follows:?1?The No.z6811 air-conditioned passenger train of 25 T was taken as an example,and the unsteady heat transfer process of the compartment enclosure was calculated using the Z transfer function method.In the calculation of unsteady heat transfer process,the convection heat transfer coefficient of the outer surface applied to the plateau train was determined first.Secondly,on the basis of acquisition of the meteorological data at main train stations,considering the effect of train running direction on the solar radiation heat gain fully,the train running route lines were simplified reasonably the hourly air conditioning outside sol-air temperature was taken as the function of the running time to determine the air conditioning outside sol-air temperature along the railway operating in winter.?2?The flow field,temperature field,CO₂ concentration field and O₂ concentration field in the No.z6811 air-conditioned passenger train of 25 T in conditions of different air supply parameters were conducted numerical analysis using the FLUENT software at main stations.The mathematic and physical models of hard seat compartment in air conditioned train of 25 T were set up,to study the influence of air supply parameters and boundary conditions at main stations on the flow field,temperature field,CO₂ concentration field and O₂ concentration field.?3?The modified equation of the body heat balance and the PMV index were used to research the thermal comfort of the passengers in conditions of different air supply parameters at main stations.The results showed that: In the process of Qinghai-Tibet Railway air-conditioned passenger train running,the influence of solar radiation on the thermal environment in compartment could not been ignored.Because of the air supply location and the door,the wind velocity around passengers near the corridor was faster than around other passengers,and some of the passengers had draft sensation.The whole airflow had the trend from the central compartment to the east train door.By the heat dissipation of passengers and the radiator and the velocity field,the temperature in the passenger area was higher than the corridor,and there was a large temperature gradient around the passenger area.There was rising thermal plume above the passengers,and high temperature gas accumulation below the luggage rack.By the coupling effect of velocity field and temperature field and the return air of the door,the CO₂ concentration in the upper region of the compartment showed a rising trend from the central compartment to the door and the CO₂ concentration under the seat decreased.The CO₂ concentration in the upper region was higher than that under the seat.There was a large CO₂ concentration gradient around the passengers breathing area.The temporal and spatial variation of O₂ concentration had inverse correlation with the temporal and spatial variation of CO₂ concentration.The O₂ concentration was low in the area of high CO₂ concentration,and the O₂ concentration was high in the area of low CO₂ concentration.There was a large O₂ concentration gradient around the passengers breathing area.The PMV values vary from 0.5 to 1,most values were in the range of-0.5 to 0.5,and the thermal comfort of the passengers was great.With the increasing of the wind velocity,the flow field,temperature field,CO₂ concentration field and O₂ concentration field in the train changed significantly,the overall air velocity improved,and the vortex increased and moved.By the effects of velocity field on the temperature field,the temperature distribution was more uniform and decreased.The local temperature changed.By the coupling effect of flow field and temperature field on the CO₂ concentration field,the CO₂ concentration distribution was more uniform and decreased.The temporal and spatial variation of O₂ concentration had inverse correlation with the temporal and spatial variation of CO₂ concentration.With the increasing of the wind velocity,the overall O₂ concentration distribution was more uniform and increased.The fluctuation of the PMV value was heavier and the fluctuation range increased from-1 to 1,the local area was beyond the range of-1 to 1,the thermal comfort distribution in the compartment was uneven.The air-conditioned passenger train operating in winter along the Qinghai-Tibet Railway was not only influenced by the changing meteorological parameters along the line,but also the compartment enclosure,and the dissipation of the passengers and electric heaters.More meticulous work should been done to obtain more practical,accurate,and complete research results because of these complex and changeable factors.