Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: entropy balance

Sortuj według:

Ogranicz wyniki do:

Selected aspects of the choice of live steam pressure in PWR nuclear power plant

Laskowski Rafał, Smyk Adam, Jurkowski Romuald, Ancé Julien, Wołowicz Marcin, Uzunow Nikołaj

Archives of Thermodynamics

2022

Vol. 43, no 3

85--109

In commercially available generation III and III+ PWR (pressurized water reactor) reactors, pressure of steam produced in steam generators varies in a relatively wide range from 5.7 to 7.8 MPa. Therefore, it is important to ask which value of steam pressure should be used for a specific unit, taking into account different location conditions, the size of the power system and conditions of operation with other sources of electricity generation. The paper analyzes the effect of steam pressure at the outlet of a steam generator on the performance of a PWR nuclear power plant by presenting changes in gross and net power and efficiency of the unit for steam pressures in the range of 6.8 to 7.8 MPa. In order to determine losses in the thermal system of the PWR power plant, in particular those caused by flow resistance and live steam throttling between the steam generator and the turbine inlet, results concerning entropy generation in the thermal system of the power plant have been presented. A model of a nuclear power plant was developed using the Ebsilon software and validated based on data concerning the Olkiluoto Unit 3 EPR (evolutionary power reactor) power plant. The calculations in the model were done for design conditions and for a constant thermal power of the steam generator. Under nominal conditions of the Olkiluoto Unit 3 EPR power unit, steam pressure is about 7.8 MPa and the steam dryness fraction is 0.997. The analysis indicates that in the assumed range of live steam pressure the gross power output and efficiency increase by 32 MW and 0.735 percentage point, respectively, and the net power output and efficiency increase by 27.8 MW and 0.638 percentage point, respectively. In the case of all types of commercially available PWR reactors, water pressure in the primary circuit is in the range of 15.5−16.0 MPa. For such pressure, reducing the live steam pressure leads to a reduction in the efficiency of the unit. Although a higher steam pressure increases the efficiency of the system, it is necessary to take into account the limitations resulting from technical and economic criteria as well as operating conditions of the primary circuit, including the necessary DNBR (departure from nucleate boiling ratio) margin. For the above reasons, increasing the live steam pressure above 7.8 MPa (the value used in EPR units that have already been completed) is unjustified, as it is associated with higher costs of the steam generator and the high-pressure part of the turbine.

A role of the heat and work uncompensated transformations in the balance of entropy and the turbomachinery eﬃcienc

Kowalczyk T., Ziółkowski P., Sławiński D., Cisak M., Badur J.

Transactions of the Institute of Fluid-Flow Machinery

2017

nr 135

11--27

The notion of heat uncompensated transformation has early been introduced by Clausius in 1854 and next, after ﬁfty years of forgetting, in 1904 Duhem has revalorized it and combined it with a new notion of work uncompensated transformation [3]. In this way the so-called ClausiusDuhem inequality has been established. In our paper we wish to present a novelized procedure of estimating the role of the uncompensated transformations of heat and work within the ﬂow of viscous and heat conducting working ﬂuid like water stream. The original procedure was introduced by Puzyrewski and it is essential in expressing of a local, in time and space, balance of entropy. Futhermore, this unique approach leads to redeﬁnition of the eﬃciency notion, as is usually applied to ﬂuid-ﬂow machineries, to a new one important in computational ﬂuid dynamics (CFD) three-dimensional modeling. As a result, it is shown that usage of the polytropic eﬃciency, instead of the isentropic eﬃciency, is more convenient and seems to be natural in CFD approach. Helpfully, we have also found a correlation between those two eﬃciency deﬁnitions with usage of proposed new dimensionless (criterion) number.

Application of selected balance methods to the evaluation of performance parameters of the extraction back-pressure power unit in a combined heat and power plant

Tokarz T., Karpiel T.

Mechanics / AGH University of Science and Technology

2008

Vol. 27, no. 1

43-52

Thermal measurements of the extraction back-pressure power unit in the combined heat and power plant for a wide range of working loads were utilised to develop an algorithm for computing performance parameters of the power unit. The calculation procedures use the enthalpy balance method and the entropy balance method. Adequacy of the two methods was compared on the basis of performance characteristics of the investigated power unit.

Na podstawie pomiarów cieplnych bloku upustowo-przeciwprężnego elektrociepłowni, przeprowadzonych w szerokim zakresie obciążeń eksploatacyjnych, opracowano algorytm obliczeń podstawowych parametrów charakteryzujących pracę bloku. W tym celu przeprowadzono wymagane obliczenia, wykorzystując zasady entalpowej i entropowej metody bilansowej. Następnie dokonano analizy porównawczej przydatności obu metod do sformułowania poprawności oceny efektywności pracy badanego bloku.