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1
Content available Verification of heat flux and temperature calculation on the control rod outer surface
Taler J., Cebula A.
Archives of Thermodynamics
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2011
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Vol. 32, no. 3
157-173
EN
The paper presents heat transfer calculation results concerning a control rod of Forsmark Nuclear Power Plant (NPP). The part of the control rod, which is the object of interest, is surrounded by a mixing region of hot and cold flows and, as a consequence, is subjected to thermal fluctuations. The paper describes a numerical test which validates the method based on the solution of the inverse heat conduction problem (IHCP). The comparison of the results achieved by two methods, computational fluid dynamics (CFD) simulations and IHCP, including a description of the IHCP method used in the calculation process, shows a very good agreement between the methods.
2
Content available Determination of temperature and thermal stresses distribution in power boiler elements with use inverse heat conduction method
Grądziel S.
Archives of Thermodynamics
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2011
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Vol. 32, no. 3
191-200
EN
The following paper presents the method for solving one-dimensional inverse boundary heat conduction problems. The method is used to estimate the unknown thermal boundary condition on inner surface of a thick-walled Y-branch. Solution is based on measured temperature transients at two points inside the element's wall thickness. Y-branch is installed in a fresh steam pipeline in a power plant in Poland. Determination of an unknown boundary condition allows for the calculation of transient temperature distribution in the whole element. Next, stresses caused by non-uniform transient temperature distribution and by steam pressure inside a Y-branch are calculated using the finite element method. The proposed algorithm can be used for thermal-strength state monitoring in similar elements, when it is not possible to determine a 3-D thermal boundary condition. The calculated temperature and stress transients can be used for the calculation of element durability. More accurate temperature and stress monitoring will contribute to a substantial decrease of maximal stresses that occur during transient start-up and shut-down processes.
3
Content available remote Numerical optimization of steam pipeline heating with respect to thermal stresses
Lubecki S., Taler D., Sobota T.
Archives of Thermodynamics
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2008
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Vol. 29, no. 4
87-96
EN
In this paper, temperature distributions of the fluid and pipeline are determined using the explicit finite difference method. Transient temperature responses of the fluid and pipeline wall together with thermal stresses on internal and external wall surfaces were obtained from numerical solution. The optimum time changes of the steam temperature during pipeline heating was calculated by using the Duhamel's integral.
4
Content available remote Predictions of heat transfer correlations for helically coiled tube-in-tube heat exchangers
Sobota T.
Archives of Thermodynamics
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2007
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Vol. 28, no. 3
29-40
EN
A method which allows numerical calculations unknown parameters in correlation formulas for Nusselt number and calculations of heat transfer coefficient was presented. The values of unknown parameters and heat transfer coefficients were determined on the hot and cold fluid side simultaneously with-out necessity of prior indirect calculations of overall heat transfer coefficient. Calculations were carried out on the basis of experimental data for parallel and counter flow in helically coiled heat exchanger CCX14 tube in tube type. As a result of numerical calculations distributions of Nusselt number versus of Reynolds number in circular and annular channel were presented.
5
Metoda inwersji w lokalizacji obszarów o zwiększonej wibroaktywności
Stryczniewicz L.
Mechanika / Akademia Górniczo-Hutnicza im. St. Staszica
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2004
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T. 23, z. 2
307-315
EN
Inverse methods allow for an acoustic assessment of machines on the bases of analysis of acoustic field parameters. Modeling of the vibroacoustic energy radiation from the sound source to the receiver and the knowledge of the true value of an acoustic pressure at the measuring points allows to reverse the propagation path and thus to determine the parameters of the source itself. Inverse methods can be applicable in the identification of vibroacoustic energy sources and in the sound radiation assessment. Reciprocity methods are often used together with inverse methods. The inverse method is very sensitive to the position of the substitute sources. This feature can be also utilized for the determination of the position of the actual sources. In the article are presented the examples from research carried by the author of machines in view of estimating the possibility to locate the zones of increased vibroactivation by the method of inversion. The computable procedure let estimate both the location and partial acoustic powers of noise sources on the base of the acoustic field's parameters
PL
Metody inwersyjne pozwalają na ocenę akustyczną maszyn na podstawie analizy parametrów pola akustycznego. Metody inwersji w wibroakustyce mogą znaleźć zastosowane w problemach identyfikacji źródeł energii wibroakustycznej i ocenie promieniowania dźwięku. Bardzo często z metodami inwersji łączone są metody wzajemnościowe. Metoda inwersji jest bardzo wrażliwa na lokalizację źródeł zastępczych. Własność" ta może być również wykorzystana do wyznaczania położenia źródeł rzeczywistych. Wrażliwość metody zależy także od rozmieszczenia punktów obserwacji. W artykule przedstawiono przykłady z przeprowadzonych przez autora badań pod kątem oszacowania możliwości lokalizacji obszarów o zwiększonej wibroaktywności metodą inwersji. Procedury obliczeniowe pozwoliły na podstawie parametrów pola akustycznego oszacować zarówno położenie, jak i cząstkowe moce akustyczne złożonych źródeł dźwięku.
6
Content available remote Rekonstrukcja zmian temperatury powierzchni gruntu w Polsce w ostatnim 500-leciu na podstawie profili geotermicznych
Majorowicz J., Šafanda J., Przybylak R., Wójcik G.
Przegląd Geofizyczny
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2001
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Z. 4
305-321
EN
Reconstruction of the ground surface temperature history in Poland was derived from the in-version of the temperature profiles with depth in over 20 wells. Temperature histories for the period 1500 A.D. till 1977 A.D. agree well with instrumental record of the surface air temperature available for the last two centuries. We are observing large warming since early 19th century of the magnitude of 0.6-0.9°C preceded by a colder climate since 1500 A.D. interrupted by a warmer one with a local maximum in the 1700 A.D. The climatic reconstructions based on the deepest wells (> 470 m depth) show very god correlation among groups of wells. The statistical correlation of the reconstructed histories (from the well temperature data) with the instrumental record (air temperature) from the homogeneous Warsaw series is very high. Statistical correlation coefficient as high as 0.9 is seen for some groups of wells. Geothermal data and their inversion is the only direct physical method to determine the value of warming/cooling events in the past. This is done without the need of calibration based on the correlation with the present air surface temperature record as needed for the proxy reconstructions (tree rings etc
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