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179Control Station the study of the heat exchanger that includes Objective According to the requirements of the work A Analysis of the behavior of the process in open loop in simulation B Obtaining the process model at two different operation points C Tuning of P PI and PID controllers D Comparison of closed loop behavior with different settings of the controller parameters considering variations of type jump in the reference jump type variations in the disturbance 1 First we learned that the heat exchanger we are studying is actually a process simulation of a commercial software Heat exchanger as shown below click to enlarge Manual mode as open loop is called Secondly its behavior is a hot liquid cooler of casing and countercurrent tube The measured process variable is the temperature of the hot liquid that comes out of the tube side exchanger To adjust this heat output temperature the controller moves a valve to manipulate the flow of coolant on the side of the housing As the warm flow rate increases the mixed flow temperature decreases and vice versa The process variable measured PV is the temperature of the hot liquid leaving the exchanger The output signal from the controller CO moves the valve to manipulate the flow of cooling liquid on the side of the housing to keep the PV at the reference point SP Heat the liquid flow as a process disturbance D As shown PV 140C CO 39 D 10 L min
Only controller during the heat exchanger 1 Design Level Operations DLO For heat exchangers we specify that SP and PV are typically at 138 C and may be produced at temperatures between 138 C and 140 C Design PV and SP 138 C in the range 138 to 140 C Expected to have warm liquid flow disorders D 10 L min 1 Collect data in DLO 2 FOPDT model fitting to design data a simple FOPDT model provides a very good approximation of the dynamic response behavior between the controller output CO signal of this process and the measured process variable PV 3 Designing with parameters CO CO bias Kc e t Calculate controller error e t SP PV Determine the deviation value Calculate controller gain Figure 3 From Figure 3 it can be seen that the PV design is stable at 138 C with the CO remaining at a constant value of 43 when the disturbance remains normal thereby CO deviation 43 by Calculated kc 0 7 C byCO CO bias Kc e t Calculated CO 43 0 7 e t When PV is equal to SP the error is 0 If CO stabilizes at 43 CO equals 43 of the CO deviation value PI controller function during heat exchanger 1 Design level operations DLO Design PV and SP 138 C in the range 138 to 140 C Expected to have warm liquid flow disorders D 10 L min 2 Collect data in DLO 3 Fit the FOPDT model to the design data 4 Use the parameters to complete the design Cycle sampling time T Calculate controller error e t Determine the deviation value Bumpless transfer Calculate controller gain and reset time Figure 4 The two setpoint step pairs are displayed from 138 C to 140 C and then back again Regardless of the setpoint warm liquid interference flow remained constant at 10 L min throughout the study Research on Heat Exchanger PID Control 1 Design level operations DLO Design PV and SP 138 C in the range 138 to 140 C Expected to have warm liquid flow disorders D 10 L min 2 Collect data in DLO 3 Fit the FOPDT model to the design data 4 Use the parameters to complete the design Controller gain reset time and derivative time Controller action Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Table 1