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Control-volume-based model of the steam-water injector flow

Kwidziński R.

Archives of Thermodynamics

2010

Vol. 31, no. 1

45-59

The paper presents equations of a mathematical model to calculate flow parameters in characteristic cross-sections in the steam-water injector. In the model, component parts of the injector (steam nozzle, water nozzle, mixing chamber, condensation wave region, diffuser) are treated as a series of connected control volumes. At first, equations for the steam nozzle and water nozzle are written and solved for known flow parameters at the injector inlet. Next, the flow properties in two-phase flow comprising mixing chamber and condensation wave region are determined from mass, momentum and energy balance equations. Then, water compression in diffuser is taken into account to evaluate the flow parameters at the injector outlet. Irreversible losses due to friction, condensation and shock wave formation are taken into account for the flow in the steam nozzle. In two-phase flow domain, thermal and mechanical nonequilibrium between vapour and liquid is modelled. For diffuser, frictional pressure loss is considered. Comparison of the model predictions with experimental data shows good agreement, with an error not exceeding 15% for discharge (outlet) pressure and 1 K for outlet temperature.

Exergy analysis of steam-water injector performance

Trela M., Kwidziński R.

Archives of Thermodynamics

2008

Vol. 29, no. 1

41-58

Exergy analysis is applied to estimate irreversible losses during operation to steam-water injector. Exergy destruction was determined for individual parts of the injector including steam nozzle, water nozzle and diffuser as well as for two-phase flow region comprising mixing chamber and condensation shock wave. Example calculations based on own experimental data showed that highest irreversible losses take place in two-phase flow region. Significant losses are also observed in the steam nozzle, while the losses in liquid-only flow in the water nozzle and diffuser are small and negligible. Exergy efficiency defined as outlet to inlet exergy ratio was also calculated for the injector and found to be in the range of 28-36%.