A SYSTEM DYNAMICS MODEL OF FIRE-TUBE SHELL-BOILER

A system dynamics model of fire-tube shell boiler was developed. The d erivation of the dynamics model started with a nonlinear time-variant dynamic modeling based on the transport phenomena in the fire-tube boi ler. A linear time-invariant perturbed model around steady-state opera ting points was then derived. The identifiable parameters tau(mw), tau (wa), K, beta, and tau(d) were identified by using field test data and least-squares estimation method; the coefficients C's were, meanwhile , directly predicted by using the small-perturbation relations. Empiri cal correlations of the identifiable parameters were further derived t o account for the variation of parameters with operating conditions. T he present perturbed model is thus semi-empirical and cart describe th e dynamic behaviour of fire-tube boilers over a wide range of operatin g conditions. The predictions of dynamic responses using the present m odel were shown to agree very well with the test results.