Based On The Plc Variable Air Volume Control The Study Of Air Conditioning Energy Saving Inthe Magnetic Suspension Of The Subway

With the development of economy and society and the progress of science and technology,subway has become one of the important means of transportation for people to travel,but the energy consumption of metro environmental control system is huge.Subway station is a complex system with concentrated passenger flow,large amount of equipment,long running time and low environmental comfort.Among the energy consumption of the station,the energy consumption of ventilation and air conditioning occupies about 50%of the total energy consumption of the ferroenvironmental control system.At present,the traditional domestic subway air conditioning chiller sends the chilled water as refrigerant to the combined air conditioning box(there is no condensing unit in the air conditioning box),and the chilled water is processed by the meter cooler in the air conditioning box for the damp-heat load,and then the chilled water is recycled back to the chiller.The system consists of water chiller,cooling tower,circulating water pump,combined air conditioning box and water circulating pipeline.The transfer of heat from the subway station to the outside goes through five cycles.(the first cycle:outdoor atmosphere and cooling water in the cooling tower;The second cycle:through the heat transfer of cooling water into the chiller;The third cycle:chiller refrigeration cycle;The fourth cycle:through the refrigeration cycle of frozen water through the circulation pump out;The fifth cycle:chilled water enters the air conditioning box for circulation),4 times of heat exchange(the first time:cooling water and outdoor air exchange,the second time:cooling water and cooling condenser,the third time:chilled water and evaporator heat exchange,the fourth time:chilled water and indoor air conditioning box table cooler heat exchange).Because the system increases the energy consumption of chilled water transportation,the evaporation temperature ofthe whole machine is significantly reduced and the energy consumption of the subway air conditioning system is increased.Therefore,the new energy-saving combined air conditioning system and control strategy came into being.The water-cooled direct expansion air conditioning system eliminates the "secondary heat exchange and cooling water cycle",and further derives the function of the combined air conditioning box.The chiller unit is integrated into the combined air conditioning box as a functional section of the combined air conditioning box to improve the refrigerant evaporation temperature and the energy efficiency of the whole machine.With the maturity of magnetic levitation centrifugal compressor,the advantages of water-cooled direct expansion air conditioning box are further expanded.The excellent energy efficiency ratio of partial load of the magnetic levitation centrifugal compressor breaks down the traditional unit’s low energy efficiency ratio of partial load and the unit’s low energy efficiency in long-term operation under partial load.Magnetic levitation direct expansion station hall air conditioning unit,is composed of magnetic levitation centrifugal compressor,water cooled direct expansion air conditioning system and blower,etc.,modular air conditioning unit.However,most units adopt constant air flow control,which fails to bring out the energy conservation of some load conditions of the units.In this paper,through the iteration of the maglev direct expansion station hall air conditioning,from the prototype fluorine system research and development,electronic control system research and development,PLC code writing,testing and through the industry test standards.Through measurement of unit model,and find out the four kinds of control strategies,unit cold quantity air volume strategies(manual air volume given),constant cooling unit quantity strategy(manual)given cooling capacity,unit variable air volume after cooling quantity first strategy(automatic+air cooling capacity),variable air volume before cooling unit quantity strategy(air+cold quantity automatically)automatically.Through the analysis of the four control strategies,it is found that the control strategy of first variable air volume and then cooling volume is better than the other three.The energy saving effect reached 53%.