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PIDTune
PIDTune Vs. Heat Exchanger Performance

PIDTune 與 Heat Exchanger Performance 使用情況與統計

PID Tuner uses the IMC (Internal Model Control) method to calculate PID tuning parameters. I’ve tried a lot of tuning methods over the years and have found this one to be the best. The app is written for the iPad to show all the information on one page. The program calculates: PID Parameters: Controller Gain (Kc) Integral Time (Ti) Derivative Time (Td) For process types First Order with Dead Time (FO) Second Order with Dead Time (SO) Integrating or Long Time Constant with Dead Time (I) For controller types Parallel (non-interacting) c(s) = Kc (1 + 1/(Ti s) + Td s) Series (interacting) c(s) = Kc (Ti s + 1)/(Ti s)(Td s + 1) For controller modes PID PI You can either enter the process gain (Kp) directly or enter the changes in the controlled virable (CV) and manipulated variable (MV). Tuning aggression is adjusted using the slider to set the closed loop time constant to the process time constant ratio (λ/Ƭ). The closed loop time constant (λ) is the time the controller is expected to reach set point (plus the dead time (ϴ)). Setting the closed loop time constant to process time constant ratio (λ/Ƭ) to 1.0 will make the MV change to its final value and allow the process to settle out to the setpoint. Setting (λ/Ƭ) greater than 1.0 will give a slower responce. Setting (λ/Ƭ) less than 1.0 will cause the MV to make a larger change and then reduce to its final value. Tight tuning would be to set the close loop time constant to the dead time. Use the Integrating Process type (Ƭ = ∞) for both integrating processes or processes with long time constants. These processes use the maximum slope as the process gain. Tuning aggression for these processes is determined by setting the closed loop time constant to the dead time ratio (λ/ϴ). Once again, setting the closed loop time constat to the dead time gives tight control. References: “Probably the test simple PID tuning rules in the World,” Sigurd Skogestad, Jounal of Process Control, July 3, 2001 “Consider the generalized IMC-PID method for PID controller tuning of time-delay processes,” Y. Lee, S. Park, M. Lee, Hydrocarbon Processing, January 2006

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Heat Exchanger Performance

HeatX (Heat Exchanger) App is developed mainly to evaluate performance in a shell and tube heat exchanger in terms of its over all heat transfer U-coefficient. It also helps in determining different maintenance requirement based on change in its performance characteristics due to degradation. To facilitate continuous monitoring now multiple heat exchanger data can be saved in a file with unique title and can be reloaded as and when required. Manufacturers generally provide design specification data such as heat transfer Area, U-coefficient, effectiveness for a given capacity performance. However, these values tend to vary over a period of time and often it is necessary to evaluate and compare design specification data with actual performance. This app serves as a tool for different maintenance personnel, energy and application engineers in monitoring performance and energy efficiency in a shell and tube heat exchanger. Fluid Properties: Users can quickly select different fluids for both shell side and tube side application from a list of most common fluids used in industrial applications. The key property data such as density and heat capacity is evaluated based on given temperature and pressure for the given fluid. For fluids that are not in the list, users can create a custom fluid with known property data. Data can be edited in both SI and USCS unit standards. Heat Exchanger Data: One can choose heat exchanger depending upon type of application as well as flows. Both inside and out side tube heat transfer area can be computed using the tube dimensional data for verification purpose as shown in the following screen shot. Performance Summary The over all heat transfer coefficient is computed and presented in the main screen. The additional result gives different key performance characteristics of a heat exchanger. App notes has all the definition and brief descriptions of different key parameters presented in the summary. In addition, provided link for the documentation of implementation and validation of math-models used with guidelines for periodic maintenance activities.