Development Of Capacity Test System For Thermal Expansion Valve

As an important part of the refrigeration system, the thermal expansionvalve adjusts refrigerant mass flow entering the evaporator according to the changeof superheat. Capacity is an important performance index of thermal expansion valve,and it characterizes refrigeration capacity of the thermal expansion valve. Capacitytest must be carried out under certain conditions which national standards stipulatestrictly. However, at present, the capacity test system for thermal expansion valvewidely used traditional single-input single-output control algorithm, which ignoredthe coupling of working condition parameters. Therefore, it is unable to make thetest conditions to achieve ideal quality, which results in low precision of capacity test.Based on the above situation, a capacity test system based on multivariable fuzzyadaptive algorithm has been developed, which can achieve the optimization controlof test conditions and accurate test of capacity. Following are the main contents ofthis paper:(1) The design of capacity test system for thermal expansion valve waspresented. The system design includes the design of opening test device, refrigerantmass flow test device and control module. Opening test device consists of sensors,magnetic valves, electric proportional valve, thermostat and so on, and it canmeasure characteristic curve of opening-thermo-bulb temperature. Refrigerant massflow test device consists of refrigerant circuit, cooling water loop and chilled waterloop, and it can measure characteristic curve of refrigerant mass flow-opening.Control module in which IPC acted as the core, realizes the collection of signal andcontrol by multi-function date acquisition card. In the system software design, VisualBasic6.0was used to develop a set of visual test software, providing a friendly andeasy-to-use user interface.(2) Research on the control algorithm of the refrigerant flow test condition wasprovided. The parameter self-turning multivariable fuzzy control alagorithm wasapplied to the control of working condition based on the analysis of the influencefactors of working condition and coupling relationship between parameters. And in this paper, the control quality of the controller was analyzed. Control results showthat the algorithm has good traceability and high control precision.(3) In the experimental research, the experimental date of capacity test systemfor thermal expansion valve was analyzed, and the performance of the system wasevaluation according to the experimental date. The experimental results show thatthe relative error of capacity test is within1.5%; combined standard uncertainty ofcapacity test is0.059kW; expanded uncertainty is0.118kW, which meets the designrequirements of the subject.