Application Research On Temperature Control System For Heat Exchanger Test Process

Heat exchangers are heat exchange equipments to transfer heat from the thermal fluid to the cold fluid, which are widely used in chemical, petroleum, heating and ventilation, electrical and other industrial departments, the product quality of which plays an important role in energy efficiency. Therefore, in order to ensure the quality of heat exchangers, a professional institution is necessary to supervise the performance test of heat exchangers.Taking Shanghai Lan Bin refining equipment laboratory measurement and control system of Gansu Lanpec Technologies Limited as the background, on the basis of heat exchanger performance test principle, a heat exchanger performance test measurement and control system was studied in the thesis. With PLC as the core, the system adopted the industrial control computer to monitor t he test process. The signal collection of industrial field, control of actuators and the switch control of different test conditions were realized through PLC. The computer communicated with PLC through PROFIBUS to realize the real-time monitoring, parameter settings and data processing in the heat exchanger test process.Heat exchanger performance test focuses on establishing a testing condition meeting a certain temperature and flow requirements. When testing, set a certain inlet medium flow of both heat and cold sides of the heat exchanger specimen, then control the inlet temperature of both sides to be steady quickly at the set value of the testing condition, according to the heat exchanger test standard, collect and save corresponding data; Then change the current inlet medium flow, after the temperature be steady at the set value again, continue to test data. Finally, analyze and calculate the total heat transfer coefficient and flow resistance according to the data so that the overall performance of the heat exchanger is evaluated. In the whole test process, the key is to control the inlet temperature of both heat and cold sides of the heat exchanger specimen to be steady quickly.The inlet temperature control system of heat and cold sides of the specimen is a large delay, time-varying and multivariable nonlinear system, the traditional PID control algorithm will result in long adjusting time and low control precision, which is difficult to realize the rapid and stable temperature control of both inlet sides. The thesis established the temperature control model for heat exchanger test process, analyzed the advantages and disadvantages of PID control algorithm, and studied the fuzzy control algorithm, then combined the fuzzy control and PID control to compose fuzzy-PID control algorithm and applied it to the system, at last the rapid and stable temperature control of both inlet sides was realized in the test process. Based on MATLAB/Simulink simulation and analysis, it has shown that the fuzzy-PID control algorithm could suppress overshoot, speed up the response, shorten setting time and improve control precision, etc, which could meet the inlet temperature control requirements in heat exchanger test process.