PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 8

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  odwrotne przewodzenie ciepła
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available A study on power losses of the 50 kVA SiC converter including reverse conduction phenomenon
Rąbkowski J., Płatek T.
Bulletin of the Polish Academy of Sciences. Technical Sciences
|
2016
|
Vol. 64, nr 4
907--914
EN
This paper deals with performance of the 50 kVA three-phase converter built with switches based on SiC MOSFET and anti-parallel Schottky diodes. In contrast to popular IGBT converters, a negative switch current is capable of flowing through the reverse conducting transistor, which results in different distribution of power losses among the devices. Thus, equations describing the conduction power losses of the transistor and diode are improved and verified by means of circuit simulations in Saber. Moreover, a comparison of power losses calculated with the use of standard and new equations is also shown. Total power losses in three SiC MOSFET modules of a 50 kVA converter operating at 20 kHz are up to 30% lower when reverse conduction is taken into account. This shows the importance of the discussed problem and proves that much better accuracy in the estimation of power losses and junction temperatures of SiC devices may be obtained with the proposed approach.
2
Content available Analysis of the possibility of determining the internal structure of composite material by estimating its thermal diffusivity
Kucypera S.
Archives of Thermodynamics
|
2014
|
Vol. 35, no. 1
3--15
EN
The aim of this paper is analysis of the possibility of determining the internal structure of the fibrous composite material by estimating its thermal diffusivity. A thermal diffusivity of the composite material was determined by applying inverse heat conduction method and measurement data. The idea of the proposed method depends on measuring the timedependent temperature distribution at selected points of the sample and identification of the thermal diffusivity by solving a transient inverse heat conduction problem. The investigated system which was used for the identification of thermal parameters consists of two cylindrical samples, in which transient temperature field is forced by the electric heater located between them. The temperature response of the system is measured in the chosen point of sample. One dimensional discrete mathematical model of the transient heat conduction within the investigated sample has been formulated based on the control volume method. The optimal dynamic filtration method as solution of the inverse problem has been applied to identify unknown diffusivity of multi-layered fibrous composite material. Next using this thermal diffusivity of the composite material its internal structure was determined. The chosen results have been presented in the paper.
3
Content available remote Application of swarm intelligence algorithms in solving the inverse heat conduction problem
Hetmaniok E., Słota D., Zielonka A.
Computer Assisted Methods in Engineering and Science
|
2012
|
Vol. 19, no. 4
361-367
EN
In the paper a proposal of using selected swarm intelligence algorithms for solving the inverse heat conduction problem is presented. The analyzed problem consist s in reconstructing temperature distribution in the given domain and the form of heat transfer coefficient ap pearing in the boundary condition of the third kind. The investigated approaches are based on the Art ificial Bee Colony algorithm and the Ant Colony Optimization algorithm, the efficiency of which are ex amined and compared
4
Content available Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes
Taler D., Taler J., Kowal A.
Archives of Thermodynamics
|
2011
|
Vol. 32, no. 1
77-88
EN
The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surface of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.
5
Content available remote A new method of drum heating determination during start-up of steam boilers
Taler D., Dzierwa P.
Archives of Thermodynamics
|
2009
|
Vol. 30, no. 4
81-95
EN
A method for determining time-optimum medium temperature changes is presented. Heating and cooling of pressure exposed elements will be conducted in such way, that the circumferential stresses caused by pressure and fluid temperature variations at the edge of the opening and at the point of stress concentration, do not exceed the allowable values. How-ever, the calculated optimum temperature changes are difficult to follow in practice in the initial stage of heating. It is however possible to in-crease the fluid temperature stepwise to the minimum value and then heat the pressure component according to the determined optimum temperature changes. Allowing stepwise fluid temperature increase at the beginning of heating ensures that the heating time of a thick-walled component is shorter, than heating time resulting from the calculations according to EN 12952-3 European Standard or TRD 301 regulations.
6
Identyfikacja zależnych od temperatury parametrów cieplnych ciał ortotropowych z wykorzystaniem rozwiązania zagadnienia odwrotnego przewodzenia ciepła
Kucypera S.
Modelowanie Inżynierskie
|
2007
|
T. 3, nr 34
79-84
PL
W zagadnieniach identyfikacji procesów termofizycznych istnieje często konieczność wyznaczenia charakterystyk temperaturowych dla współczynnika przewodzenia ciepła i ciepła właściwego materiałów ortotropowych. Dlatego celem niniejszej pracy jest identyfikacja charakterystyk temperaturowych parametrów termofizycznych materiałów ortotropowych za pomocą rozwiązania odwrotnego zagadnienia przewodzenia ciepła oraz danych pomiarowych. Do rozwiązania zagadnienia odwrotnego wykorzystano iteracyjną metodę dynamicznej estymacji sekwencyjnej. Przedstawiono przykładowe wyniki analizy.
EN
In the identification of the thermophysical processes often it is necessary to determine temperature characteristics for the thermal conductivity and specific heat of the ortotropic materials. Therefore the aim of this paper is identification temperature characteristics of the thermophysical parameters of the ortotropic materials by means of solving the inverse heat conduction problem and measurements data.. To solve the inverse problem the iterative sequential dynamic estimation method has been used. Selected results of the analysis have been presented.
7
Content available remote Measurement of unsteady fluid temperature with the use of inverse heat conduction solution
Taler J., Wójtowicz B.
Archives of Thermodynamics
|
2007
|
Vol. 28, no. 3
3-14
EN
An analytical method for determining temperature of the fluid affecting a thick walled component based on an inverse heat conduction problem is presented in this paper. Effectiveness of the method is illustrated by following examples: one of a temperature sensor attached to the outer surface of a thick-walled pipe or placed inside a pipe wall heated by a flow of steam from inside and another of a cylindrical thermometer quickly submerged in boiling water.
8
Content available remote Inverse analysis of the heat conduction process induced by impinging jet
Woelke M., Bogusławski L.
Archives of Mechanics
|
2002
|
Vol. 54, nr 4
299-317
EN
This paper presents an analysis of the cooling process of a solid, induced by the impingement of an air jet. Solutions of the inverse heat conduction problem were obtained by applying the heat functions to formulate the base functions of the Finite Element Method. The applied heat functions identically satisfy the heat conduction equation in dimensionless co-ordinates. The minimisation of the functional, presented in this paper, leads to the solutions of the analysed problem. The temperature distribution of the analysed solid was determined by solving the inverse heat conduction problem by means of the temperature measurements taken inside the solid. Properties of the heat function were applied to reconstruct the distribution of the Bi number on the heat exchange surface; this in turn enables to determine the heat transfer coefficient on the analysed surface. The results of the analysis were compared with the data found in the literature.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.