The principle

functions

and validation test results of a simplified heat-exchanger model have been briefly described. By using the said model

the mass flow of flue gas and steam （water） can be calculated on the basis of temperature and pressure concerning the working medium at inlet and outlet of the boiler’s heating surface

and the variated amount of the heating surface’s thermal resistance can be calculated without using structural parameters of the heating surface. Hence

adopting the said model to develop optimized control system for the soot-blowing devices of utility boilers

the existing problems in conventional method

such as low precision of the flow rate calculation

and non-accuracy of the fouling resistance calculation etc.

can be solved

and practical examples of the developed optimal control system for sootblowing devices being given.