RTD (Resident Time Distribution)
 | Purpose of the program |  |
RTD (Residence Time Distribution) program is a component of the software for chemical engineering. RTD is intended for investigation of hydrodynamic flows in chemical apparatuses on the base of stimulus - response technique. This technique includes the injection of a small amount of the tagged inert particles (tracer) in the inlet stream and the observation of the corresponding response in the outlet stream of an apparatus. A flow model is then selected by matching the experimental RTD curve with that obtained from the mathematical model. The suitable model is one that matches the experimental data with the smallest error and describes the flow in the apparatus with the smallest number of physical parameters. The program provides the convenient interface and powerful tools for: - initial experimental data processing;
- creation model of the flow in reactor with using the predefined flow patterns as the building blocks;
- estimation of the flow model parameters;
- simulation of a system responses to the input signals of different types (including Dirac, step);
- creation a user-defined flow patterns.
| Structure | |
RTD is based on use of Experts. Experts accompany user when he estimates kinetic parameters, input experimental data or creates new flow models. Each Expert provides user with sequential directions and legends for better understanding the immediate procedure. Experts ensure not only two-way traffic but also long-jump navigation inside the current Expert and among them. | Initial data processing | |
The Experiment Expert ensures initial data processing that includes the followings: - spike correction;
- filtration (median, linear and parabolic filters);
- linear transformation;
- normalization;
- baseline correction (from start to end, horizontal through start or end point);
- tail correction (according to an exponential law);
- cutting fragment of valuable data;
- evaluations of moments of the zero, first, second and third order.
| Creation of flow model | |
The Model Expert provides the convenient graphical interface for creation and modification of the flow models on the base of the followings flow patterns: - CSTR;
- CSTRs in series (n);
- CSTRs in series (n) with back mixing;
- CSTR with bypass;
- CSTR with dead zone;
- CSTR with bypass and dead zone;
- CSTR with bypass and dead zone in series (n);
- Plug Flow Reactor with back mixing;
- Plug Flow Reactor.
Flow model is described by its transfer function. Flow models of different complexity may be constructed by combination of several flow patterns. Any possible connections of blocks are supported, including parallel and series connection, loops and recycling. Each of the flow patterns is described by its transfer function. The transfer function of the whole model is generated automatically. | Flow parameters estimation | |
With the Estimation expert user can estimate the best values for hydrodynamic flow models that are nonlinear in the parameters. Estimation is done in time domain by the least square method. The convolution approach is used. To do that, model output signal is calculated at some values of unknown parameters as convolution of the model transfer function (in time domain) and experimental input signal. Then it is compared with experimental signal. Parameter values are changed to reduce the lack of fit and the process is repeated automatically, if it is necessary.
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