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Feasibility study on application of steam injectors as feedwater heaters in supercritical Rankine cycle

Trela M., Kwidziński R., Głuch J., Butrymowicz D.

Archives of Thermodynamics

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2009

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Vol. 30, no. 4

133-147

EN

In the paper, a mathematical model of steam-water injector is presented. The model was used in heat balance calculations of Rankine cycle to examine the influence of novel injector feedwater heater system on efficiency of supercritical 600 MW coal-burned turbine unit. Also, the geometry of the injector system suitable for the considered Rankine cycle was determined. Analysis of cycle efficiency showed that application of steam-water injectors is most beneficial in the low pressure part of the Rankine cycle. Efficiency rise could be gained due to the absence of thermal degradation during the injector operation and due to its pumping work. Heat transfer coefficients for the injectors reach high values in the range of 190-806 kW/m[^2]K. Therefore, the heat transfer area in the system of injectors appeared to be smaller by a factor of 60 compared to equivalent shell-and-tube feedwater heaters. Size estimations of the new feedwater injectors shows that the overall dimensions and weight of the proposed injector system, consisting of several injectors connected in parallel, is significantly smaller compared to common shell-and-tube heaters. Exact proportions, however, will depend on detailed design of the entire system geometry.

2

Exergy analysis of losses in a two-phase steam-water injector

Trela M., Kwidziński R., Butrymowicz D.

Chemical and Process Engineering

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2008

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Vol. 29, z. 2

453-464

EN

Exergy losses in elements of a steam-water injector have been determined. Exemplary calculations based on the experimental data showed that the highest irreversible losses take place in a two-phase flow in the mixing chamber and in the shock wave region. The exergy efficiency for the injector, defined as the outlet to inlet exergy ratio, has been found to lie in the range of 28-36%.

PL

Wyznaczono straty egzergii w elementach składowych strumienicy parowo-wodnej. Na podstawie obliczeń opartych na wynikach badań eksperymentalnych stwierdzono, że największe straty nieodwracalności występują w przepływie dwufazowym w komorze mieszania i w obszarze fali uderzeniowej. Obliczono także sprawność egzegetyczną, zdefiniowaną jako iloraz egzergii wylotowej i wlotowej, która dla badanej strumienicy wynosiła 28-36%.

3

Termo-hydrauliczne własności nadkrytycznych strumienic dwufazowych para-woda

Trela M., Kwidziński R.

Systems : journal of transdisciplinary systems science

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2004

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Vol. 9, Sp. 2/2

1037-1043

PL

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.

EN

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.