Research On Central Cooling Of City Underground Rail Traffic Station

In recent years, as the main form of city and inter-city rail traffic, subway hasstepped into the high-speed development period. As an important public infrastructure,subway station is arranged in the densely populated area. Due to noise, thermalemissions impact on the environment, the cooling tower or other heat facilities of theunderground station air conditioning system about these sections has become a problemin the construction of subway. To the end, the centralized cooling scheme of a pluralityof underground station aroused concern. Central cooling system has the main feature ofgeneral regional cooling system, also has its own particularity. Therefore, in the designand selection of the transmission and distribution system in subway station project, it isrequired that cold station site selection, the form of cold quantity transmission anddistribution, distribution power matching selection, temperature difference of the systemand other key problems be considered with the feature of the subway station itself.Taking a city underground rail transit station as the prototype, this paper analyzedthe integrated heat calculation method of the train running in the subway station train, aswell as the correlation of the different form of the station and the air conditioning loadof the station. Calculation and analysis of the hourly air conditioning load of a typicalstation is done. The time frequency of the air conditioning cooling load is done. Underdaytime running mode, the load depends mainly on the outdoor air changes (i.e. windload), in small stations. At the same time, the load depends mainly on the both the airchanges and flow variations, in large stations. It is relatively stable when talking aboutthe total load under nighttime running mode.The cold loss model of cold pipeline in metro central cooling station was built.Firstly heat transfer calculation theory was built, including the convection heat transferbetween the outer surface of the pipe and the tunnel air and radiation heat transferbetween the outer surface of the pipe and the tunnel wall surface. The segment mode ofthe fluid temperature rising and cooling loss was defined. The feature of theunderground space envelope structure heat transfer, the heat gain and the ventilation ofthe tunnel space were analyzed. The iterative calculation method of the tunnel intervalaverage air temperature and wall temperature was constructed. Based on the hourlymeteorological parameters of Chengdu, the station tunnel interval hourly airtemperature and hourly wall temperature was calculated which was later used to do the calculation of the transmission and distribution system cold loss. The Life Cycle CostAnalysis of the subway air conditioning transmission system was proposed. A fast railunderground station centralized cold station as the prototype, the energy saving analysis(LCCA) on metro centralized cold station transportation system was done. Comparesthe form of sharing with the separately using of secondary pump to see which is better.The results show that the sharing of secondary pump has enormous advantage in boththe initial investment and operation.Discussion about the form of the transportation system and the best site of the coldstation was done. On the condition of both three stations and four stations the LCCA onthe transmission and distribution system was done. Found to put the centralized coldstation in the load center is not always the best choice, considering the energy savingproblem. To take the form of sharing using of secondary pump and increasing thecooling radius properly would make a greater benefit in energy saving. The cold loss perunit length index and the pump consumption per unit length index were given. Analysisof cooling radius and the hydraulic balance problem was done.Calculation of the energy consumption and cold loss of the transmission anddistribution system was done separately with5℃,8℃and10℃temperaturedifference. The conclusion is known that to take the big temperature difference in theprocess of transmission and distribution would get an obvious energy saving effect. Butit has little to do with the cold loss.