Measurement And Analysis Of Evaporative Cooling Ventilation Cooling System In A Subway Station In Lanzhou

In China,the rapid economic growth has been more and more than ever.The development of each city is faster and faster.A large number of subway is built to relieve the pressure on urban road traffic when traveling.However,the energy consumption of air conditioning system in metro station accounts for about 40%of the total energy consumption.The appropriate air conditioning system should be selected according to local conditions to provide ventilation and cooling services for the public area of station hall platform,while evaporation cooling air conditioning system should be selected according to local conditions As an energy-saving,green and environmental protection air conditioner,it can maximize its energy saving advantages and reduce energy consumption.This thesis aims at the huge energy consumption,inadequate income and still need a lot of gr aims at the huge energy consumption,inadequate income and still need a lot of government financial subsidies in the process of metro operation.The process of direct evaporation cooling technology to produce cold air is analyzed theoretically by using the mechanism of heat and mass transfer.The ideal process and practical process of direct evaporation cooling technology to produce cold air are analyzed and explained.Then,we use detu temperature and humidity recorder,anemometer and air quality detector to measure the air conditioning system of subway station in cooling season for two consecutive years.After sorting and analyzing the data,we mainly draw the following conclusions:（1）Piston air mode:when the train enters the station,the air volume of piston air generally presents an increasing trend.The heat in the tunnel enters the platform public area with piston wind,which causes the ambient temperature of the platform public area to rise;when the train leaves the station,the heat in the public area of the platform is discharged to the rail area with the piston air,which is more unstable than the piston wind when entering the station,and the air volume also decreases,showing a declining trend.The air volume of the train entering the station to the public area of the platform through the louver air outlet shall be greater than that of the train from the public area to the rail transit area when the train leaves the station.The impact of the piston air generated by the train entering the station on the environment of the platform public area is stronger than that of the piston air formed by the outbound station.（2）Mechanical ventilation mode:in mechanical ventilation mode,when the temperature of air supply dry ball is between 22.3-27.8℃,and the relative humidity is 34%-53%,the dry bulb temperature in the public area of the station hall is kept at 23.3-24.4℃,the relative humidity is kept at 43%-50%,PM_2.5content is kept below 113μg/m³,the CO₂content is kept below 853ppm;the dry bulb temperature in the platform public area is kept at21.1-22.7℃,relative humidity is kept below 853ppm;the dry bulb temperature in the platform public area is kept at 21.1-22.7℃,and the relative humidity is kept below853ppm The humidity was kept at 53%-58%,PM_2.5was kept below 112μg/m³,and the CO₂content was kept below 752ppm.（3）Direct evaporation cooling mode:in direct evaporation cooling mode,the temperature of air inlet dry ball of the unit is between 22.1℃and 30.9℃,while the wet bulb temperature is between 14.7-15.7℃,the air dry bulb temperature after treatment of the direct evaporation cooling air conditioning unit can be reduced to 19.9-16.1℃,the maximum temperature drop can reach 14.8℃,the direct evaporation cooling efficiency of the unit is more than 90%;the dry ball in the public area of the station hall can be reduced to 14.8℃;the direct evaporation cooling efficiency of the unit is more than 90%;the dry ball in the public area of the station hall The temperature is kept at 22.8-24℃,the relative humidity is kept at 42%-54%,PM_2.5is kept below 113μg/m³,the CO₂content is kept below 863ppm;the dry bulb temperature in the public area of the platform is kept at21.6-22.1℃,the relative humidity is kept at 54%-58%,the PM_2.5content is kept below113μg/m³,and the CO₂content is kept below 745ppm;the maximum cooling capacity of the direct evaporation cooling unit reaches 518kw,which can be used to achieve The EER is up to 11.09,and the evaporation water consumption reaches 740.6kg/h.（4）Control strategy:1)for piston air mode,in the whole life cycle of metro station,the piston air outlet shall be closed in summer to reduce its disturbance to the public area in the station,and the piston air outlet shall be opened in the transitional season to make full use of the piston air to ventilate and cool the public area in the station.2)In the early stage of metro station operation,only by adjusting the mechanical ventilation mode,the demand for temperature in the public area of the station in the whole cooling season can be met,and the direct evaporation cooling mode is not required.3)In the short term and long term of metro station operation,passenger flow increases and the load in the station increases.Firstly,the station public area is cooled by mechanical ventilation mode.When the maximum mechanical air supply volume station public area is still heating up,the direct evaporation cooling mode is opened to provide cooling service temperature for the public area in the station.（5）System comparison and analysis:under the same comfort,the annual operation and maintenance cost of evaporation cooling ventilation cooling system in metro station is lower than that of traditional mechanical refrigeration system and traditional mechanical ventilation system.The initial investment is far lower than that of mechanical refrigeration system,but slightly higher than that of traditional mechanical ventilation system.In the later long-term operation,the energy consumption will be greatly reduced,Achieve the purpose of energy conservation.