| Based on the comprehensive analysis of refrigerated containers for important means of cold chain logistics,this paper puts forward a new type of railway refrigerated container refrigeration unit suitable for road-rail transport and sea-rail transport by referring to a large number of domestic and foreign experts and scholars.The unit adopts R404 A refrigerant and capacity regulation combined with frequency conversion capacity regulation and hot air bypass capacity regulation to ensure temperature control accuracy.A series of performance experiments were carried out to test the characteristics of the refrigeration unit.First,research to understand the market demand for refrigerated container refrigeration unit capacity control system,through the analysis of the existing refrigeration unit equipment composition,working principle and the current feedback on the market refrigeration unit out of the problem,summarize and design a new refrigeration unit,while completing the refrigeration unit structure design,electrical control box design,and according to the above design,complete the refrigeration unit in the refrigeration compressor,condenser,evaporator,throttling elements and electrical equipment and other components selection,build the design of the refrigeration unit and electrical control box;complete the sensor and refrigeration unit connection,ready for the subsequent experimental data collection preparatory work.Then,the development of the control strategy of this design rail refrigeration vessel function is high-speed cooling function,capacitance adjustment function(ie,controlling internal temperature accuracy of refrigerator),temperature rise function,defrosting function,control process,and control PLC program.Strategy,and complete the tuning of PID temperature control parameters in the PLC industrial computer program by test error.Finally,on the experimental platform that has been constructed,the cooling unit of this design is subjected to cooling,heating,capacity regulation and temperature step experiments,and the energy consumption of the cooling unit is analyzed,and the operating characteristics of the capacity control system of the cooling unit of this design are summarized.The experimental results show that the designed railway refrigerated container refrigeration unit has the characteristics of fast cooling speed,high temperature control precision,low load operation(even empty box operation)air supply temperature control accuracy can also be kept at ±0.2℃.Stable capacity control system,high anti-interference,fast response speed and low energy consumption of refrigeration system. |
