Simulation of Thermal Water Deaeration Based on a Matrix Approach to the Design of Heat-and-Mass Exchangers

Abstract

A matrix approach to the calculation of heat-and-mass exchangers is used to develop mathematical models of heat-and-mass transfer between water and steam and of dissolved-oxygen desorption from water in jet- or bubbling-type deaeration elements. The area of interfacial surface in the considered elements is determined using well-known methods for calculating hydrodynamic characteristics adapted on a case by case basis considering other influencing factors. The results of the experimental investigation into water deaeration in standard DA-300m and DSA-300 deaerators performed with water sampling from internal elements were used for identification models of heat-and-mass transfer and desorption of dissolved oxygen and development of their empirical support in the form of dimensionless equations for prediction of heat-and-mass transfer coefficients averaged over the interfacial area in an element. Statistical analysis methods were used to find the accuracy characteristics for the derived closed mathematical description of thermal water deaeration in the deaeration elements of interest. The proposed matrix approach to the calculation of heat-and-mass exchangers by creation of a mathematical model of individual deaeration elements was used to construct mathematical models for differently designed deaerators intended for practical important applications. The developed models were used in setting the operating conditions and improving the design of industrial deaerators. The investigations have revealed that the developed mathematical models, together with the empirical correlations as applicable, enable us to determine with an acceptable accuracy the efficiency of water deaeration in designing new or operating existing deaeration units at thermal power stations (TPS) and industrial plants.