A novel concept of enhanced direct-contact condensation of vapour- inert gas mixture in a spray ejector condenser

An analytical model of direct steam condensation (DCC) in the novel idea of spray ejector condenser (SEC) in the presence of inert gas has been developed. It is based on continuity, momentum and energy equations for the steam-carbon dioxide mixture and direct contact condensation mechanisms due to heat transfer and concentration. Crucial in the process of DCC is atomisation of the motive fluid in the ejector. The effect of atomised droplet size is exhibiting a significant amplification influence with increasing size of the droplet. Motive fluid is driving the secondary fluid-mixture of steam and inert gas in the Venturi nozzle and is cold enough to cause direct condensation. The intensity of heat transfer process from steam to water when the phases are in direct contact is much higher than the heat transfer intensity in surface heat exchangers. The analytical model pertains to a subcritical flow of a mixture of steam and gas in SEC. The model exhibits satisfactory agreement with experimental data. The model of DCC predicts higher values of temperature drop between inlet and outlet from the mixing section for the case of smaller steam-CO2 flow rates. Increasing the flow rate of steam mixture from 1.2 g/s to 3.6 g/s results in a reduction of steam mixture temperature from 25 degrees C to 14 degrees C respectively, at CO2 flow rate of 6.8 m3/h. Condensation without presence of CO2 in the same range of steam flow rate, i.e. from 1.2 g/s to 3.6 g/s results in reduction of steam mixture temperature from 56 degrees C to 25 degrees C respectively, confirming in such way the effect of CO2 presence on the efficiency of DCC. Such model allow for discussion of parameters affecting process of condensation in SEC and ability of application such condenser in power plants.

Automated summary

An analytical model for direct steam condensation in the presence of inert gas in a spray ejector condenser (SEC) has been developed. The model takes into account the continuity, momentum, and energy equations for the steam-carbon dioxide mixture, as well as the mechanisms of direct contact condensation due to heat transfer and concentration. The model predicts the temperature drop between the inlet and outlet of the mixing section, showing the effect of different flow rates and the presence of CO2 on the efficiency of the condensation process in SEC.