Abstract
In this paper, the electronic expansion valve (EXV) on the single-tube heat exchange experimental platform was used as a research object. Firstly, the EXVs were selected according to the experimental requirements, and the functional parameters were set. Subsequently, the effective opening ranges of the EXVs were determined by manual control, and the control effects of the EXVs installed at the front and back ends of the test section were compared. Finally, by self-tuning and optimizing the best response curves, the proportional and integral coefficients suitable for the experimental platform were obtained; thus, the automatic intelligent control of EXV based on the proportional integral (PI) control algorithm was realized. From setting EXV functional parameters to realizing PI control, an appropriate experimental system-debugging solution for the whole process could be obtained. Based on the solution, the system stability could be improved, and the transition process time could be shortened. Furthermore, the solution also provided a method to guarantee the accuracy of experimental data and could be applied to the debugging of similar experimental systems.
Highlights
The electronic expansion valve (EXV) is widely used for its flexible control, rapid response, and relatively independent sensing, adjustment, and execution components [1,2,3].Typically, the EXV is mostly used to regulate the flow rate of the refrigerants [4,5,6,7,8], and the influence of various factors on the flow rate characteristics of the EXV have been frequently studied [9,10]
Liu et al [12] investigated the effects of inlet pressure and temperature and EXV opening on the flow characteristics of CO2 through the EXV and predicted the mass flow rate through the EXV, and the results showed that the maximum deviation of the predicted value was less than 15.3%
Chen et al [13] showed that the mass flow rate of R245fa refrigerant increases with increasing openness, condensing temperature, subcooling, and orifice diameter, as it flows through the EXV
Summary
The electronic expansion valve (EXV) is widely used for its flexible control, rapid response, and relatively independent sensing, adjustment, and execution components [1,2,3]. The current research focuses on the application of EXV, and the function parameters setting of EXV, while the determination of its effective opening range is rarely mentioned or studied, and the EXV in the experimental platform is generally located at a fixed position in the refrigerant circulation circuit, and the control effects of EXVs in different positions are rarely compared. By setting the EXV functional parameters and determining its effective opening range, it can achieve reasonable control of the degree of superheat (DS) at the outlet of the test section. It realizes the control of EXV by the PI control algorithm through self-tuning and self-tuning optimization
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