The Identification of Local Parameters for Steam Condensation with the Presence of Air in Plate Heat Exchanger Based on Process Mathematical Model

Abstract

The condensation of vapour in the presence of noncondensing gas inside the channels of Plate Heat Exchanger (PHE) is studied on the example of steam condensation from its mixture with air. The mathematical one dimensional model of the process is developed. It is represented by the system of ordinary differential equations accounting for the change of process local parameters along the channel length. The identification of correlations for heat and mass transfer coefficients, as also pressure losses in condensing two-phase flow, is performed based on a comparison of modelling results with experimental data. The experimental model of PHE channel corrugated field consists of four corrugated plates forming three channels. The plate length is 1 m, its width is 0.225 m and a height of corrugations 0.005 m. The corrugations inclination angle to the main flow direction is 60 °. The correlations for two-phase flow are based on single-phase correlations obtained for a considered channel. For mass transfer coefficient, the most accurate results are obtained using approach accounting for transverse mass flux influence based on a stagnant film model with correction for density variation across the turbulent boundary layer. For the prediction of pressure drop in two-phase condensing flow the separate phases, model is used at low Reynolds numbers of the liquid film and dispersed annular flow model further on channel length, with growing mass flow rate of condensed liquid. The resulting mathematical model with correlations identified on experimental data can be used for the design of PHE for condensation of steam from its mixture with air.