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1 Systems : journal of transdisciplinary systems science

1 2004

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Termo-hydrauliczne własności nadkrytycznych strumienic dwufazowych para-woda

Trela M., Kwidziński R.

Systems : journal of transdisciplinary systems science

2004

Vol. 9, Sp. 2/2

1037-1043

Referat dotyczy strumienie parowo-wodnych, które mogą spełniać role pompy bądź wymiennika ciepła. W pracy przedstawiono wyniki badań eksperymentalnych modelowej strumienicy, metodę wyznaczania współczynnika przejmowania ciepła oraz maksymalnego ciśnienia wylotowego ze strumienicy. Sformułowano model zjawiska oparty o bilans pędu obu fax z uwzględnieniem rzeczywistych strat nieodwracalności w komorze micsxania i dyfuzorze.

The paper concerns experimental and theoretical studies of thermo-hydraulic performance of two-phase steam-water injector, in which the steam is a driving medium. In this type of injectors, the energy of the steam is used to push cold water from a lower to higher pressure, additionally heating it. Thus the steam injector can work as a pump or a heat exchanger. The steam injector consists generally of steam nozzle, water nozzle, mixing chamber and diffuser. The steam entering the injector is expanded and accelerated in converging-diverging steam nozzle. Having supersonic velocity and very low pressure, the steam enters the mixing chamber. Here, it meets liquid water which is drawn through the annular slot (the water nozzle). In the mixing chamber steam and water exchange heat, momentum (due to the temperature and velocity differences) and mass (due to condensation of steam on water). Usually the condensation process is terminated at the throat of the mixing chamber, followed by a rapid increase of pressure in this region (called the shock wave). Then, water is decelerated in the diffuser, which causes a further increase of pressure. The aim of the paper is to present the results of investigation of both heat transfer between the steam and water in the mixing chamber and maximum discharge pressure of the steam injector. The experimental Investigations of the steam injector comprised measurements of ptcssurCj temperature and void fraction profiles along the mixing chamber and diffuser. The mixing chamber and diffuser of test injector were made of transparent material. This allowed visual and photographic observations of flow structures in stroboscopic light as well as void fraction measurements by capacitance method. In theoretical part of the investigations, correlation for heat transfer coefficient was obtained. It is based on the dimensional analysis of one-dimensional two-fluid model of two-phase flow in the injector. The model of maximum discharge pressure from the steam injector was formulated applying the momentum balance equation. It takes into account irreversible losses due to the friction and temperature difference between both phases.