Study On Optimal Operation Of Variable Capacity And Variable Air Volume Of Direct Expansion Air Conditioning Unit In Metro Station

With the continuous development of urban rail transit and the increasingly serious energy,the ventilation and air conditioning system,as an important part of the subway system,has attracted more and more attention.It is of great significance for the sustainable and healthy development of the city metro to choose a reasonable ventilation and air conditioning system and an effective energy-saving operation strategy.As a kind of air-conditioning unit which has not been mass-produced and widely applicated in the metro station at present,the direct expansion air-conditioning unit has a great potential for application.Taking a metro station in Guangzhou as the research background and a prototype of magnetic levitation variable speed centrifugal air-conditioning unit as the research object,this paper studies the feasibility and energy-saving potential of the unit's variable capacity and variable air volume operation for the large HVAC system of the metro station.First of all,the software simulation method is adopted.Taking a practical engineering program as an example,establishes the air-conditioning load model of the large HVAC system by using the EnergyPlus simulation engine.Then the public area's annual hourly load characteristic of the metro station is studied.Secondly,taking a water-cooled direct expansion air-conditioning unit prototype as an experimental object,IPLV test and orthogonal test were carried out,aiming at the actual performance and influencing factors of the direct expansion air-conditioning unit.It provides sufficient and credible data samples for the latter's numerical simulation calculation and optimal operation strategy analysis.In addition,based on the experimental data,this paper uses the SPSS data analysis software to establish the numerical model of the magnetic levitation variable speed centrifugal air-conditioning unit by stepwise multiple regression analysis,and the correctness of the model is further determined through statistical tests,which meets the practical application requirements of the engineering program.In the last part,several cooperative frequency conversion control mode and strategy of direct expansion air conditioning system are analyzed and studied.Combined with the air-conditioning load model of metro station system and the numerical model of the unit,the simulation of the whole year operation energy consumption of the station air conditioning system is carried out,and the running results of the corresponding energy saving operation mode are obtained.Through the full year simulation,the control strategy of the direct expansion air-conditioning unit is compared and analyzed.The outcome indicates that better way and strategy is that adjusting the air volume before compressor capacity of the unit,which is also energy-saving and stable to control during the operation.Under this control operation mode,the energy saving rate of the whole year operation is 52.97% compared with the constant capacity and variable air volume control operation,and the annual energy saving can be about 9.6wkWh.