Empirical modelling of heat exchangers in a CHP plant with bleed-condensing turbine

The advanced thermal diagnosis and operating control systems of the coiwentional [1,2,3] and CHP units require application of mathematical models. In the regenerative heat exchangers heat is transferred from steam to heated water. Heat transfer is multidimensional, what entails that mathematical description is complex and time consuming. For the thermal diagnosis needs, the semi-empirical model of heat exchangers has been worked out. This model enables calculation of temperature of the feed water in variable thermal load and pressure drop in the pipeline. Pressure drop between the outlet of the group of stage of the turbine and place of localization of the exchanger has been taken into account by utilization of the empirical function of pressure losses in the pipeline dependent on steam mass fiow. Empirical function describing relationship between variation of the subcooled condensate and thermal capacity of a heat exchanger has been worked out. Empirical coefficients have been estimated by the least squares method using the results of the special measurements [4]. Obtained semi-empirical model of the heat exchangers of the 70 MWel CHP unit has been verified and evaluated with statistical factors usage.