Research On Flow Field Distribution And Passenger Thermal Comfort In Subway Carriages

In the research of the air conditioning and ventilation system of subway trains,the boundary conditions of the human body are usually set to a constant heat flow,which cannot reflect the interaction between the actual passenger’s own thermal regulation and the environment of the carriage.It is difficult to truly simulate the flow field distribution and passenger thermal comfort in the actual carriage,and it cannot reasonably evaluate the performance of the air conditioning and ventilation system.Therefore,referring to the average human body size of Chinese adult men,combined with the 57-node human thermal regulation model based on the Stolwijk model to simulate the thermal regulation response of actual passengers,so as to effectively evaluate the performance of air conditioning and ventilation systems.Taking the train carriage of Beijing Metro Line 15 as the research object,the air distribution in the carriage was measured experimentally,and the measurement results were compared with the simulation results of STAR-CCM+software.The results show that under the proper simplification of geometric model of the carriage and the pulsation characteristics of the turbulence,the error between the two is basically within 10%,which verifies the feasibility of the Realizable k-?turbulence model for simulating the flow field in the carriage.On this basis,the characteristics of the airflow organization in the carriage were studied,and it was found that the airflow velocity in the carriage is large on both sides and small in the middle,and the fluidity of the air flow is good.Taking into account the actual crowdedness of passengers in the subway carriage,a CFD model of the subway carriage with 96 passengers was established.In addition,the coupled calculation method of the thermal environment of the carriage and the thermal regulation model of the human body is used to simulate and optimize the flow field distribution in the carriage and the thermal comfort of passengers.At the same time,the non-uniformity indexes K_t and K_u,the energy utilization coefficient η,and the thermal comfort index PMV-PPD are used to compare and analyze the various schemes,so as to find the optimal air conditioning and ventilation layout scheme.Research shows that:(1)The decentralized arrangement of the vents and cross-flow fans can better improve the uneven air distribution in the original carriage and the overheating of some standing passengers.(2)The optimization effect of the airflow organization scheme of the upper and lower sides of the carriage with 3:1 distribution of air supply and return air on the upper side is the best,which effectively solves the problem of excessive wind speed on the upper side of the original carriage.It also improves the uniformity of air distribution in the carriage and the thermal comfort of passengers,with the highest energy utilization coefficient.