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1

Identification of the average and local boundary condition of heat transfer during cooling with a water spray under surface boiling

Jasiewicz Elżbieta, Hadała Beata, Malinowski Andrzej

Computer Methods in Materials Science

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2020

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Vol. 20, No. 4

147--155

EN

The study determined the local and average heat transfer coefficient and the heat flux on the surface of a cylinder cooled with a water nozzle. The inverse method was used to identify the heat transfer coefficient. An objective function was defined to determine the distance between the measured and calculated temperatures. Two models describing the heat transfer coefficient on the cooled surface were considered. The first model described changes in the heat transfer coefficient as a function of the sample radius and cooling time, and the second one assumed the dependence of the heat transfer coefficient solely on time. Numerical simulations showed significant differences in the determined heat transfer coefficients depending on the adopted model of the boundary condition. The performed tests included experimental temperature measurements at selected points of the sensor, numerical simulations of temperature changes, and the inverse solution.

2

Analysis of the Slab Temperature, Thermal Stresses and Fractures Computed with the Implementation of Local and Average Boundary Conditions in the Secondary Cooling Zones

Hadała B., Malinowski Z., Telejko T.

Archives of Metallurgy and Materials

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2016

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Vol. 61, iss. 4

2027--2036

EN

The numerical simulations of the temperature fields have been accomplished for slab casting made of a low carbon steel. The casting process of slab of 1500 mm in width and 225 mm in height has been modeled. Two types of boundary condition models of heat transfer have been employed in numerical simulations. The heat transfer coefficient in the first boundary condition model was calculated from the formula which takes into account the slab surface temperature and water flow rate in each secondary cooling zone. The second boundary condition model defines the heat transfer coefficient around each water spray nozzle. The temperature fields resulting from the average in zones water flow rate and from the nozzles arrangement have been compared. The thermal stresses and deformations resulted from such temperature field have given higher values of fracture criterion at slab corners.

3

Influence of the sample geometry on the inverse determination of the heat transfer coefficient distribution on the axially symmetrical sample cooled by the water spray

Cebo-Rudnicka A., Malinowski Z., Hadała B., Telejko T.

Computer Methods in Materials Science

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2013

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Vol. 13, No. 2

269--275

EN

The paper presents the results of the heat transfer coefficient determination while the water spray cooling process. To determine the boundary condition over the metal surface cooled by water spray the inverse heat conduction problem has been used. In the investigations the axially symmetrical sample has been used as a cooled object. Because of the specific setup of the sensor used in investigations, two finite element models have been tested in the inverse determination of the heat transfer coefficient. The first one, which simplifies the sensor geometry to a cylinder and the second one, that describes the real shape of the sensor. Also, the comparison between two different models employed to determine the heat transfer coefficient over the cooled sample surface have been presented. The boundary condition models differ in description of the function that has been employed to approximate the heat transfer coefficient distribution over the cooled surface in the time of cooling.

PL

W pracy przedstawiono wyniki obliczeń współczynnika wymiany ciepła wyznaczonego na podstawie badań eksperymentalnych. Do wyznaczenia warunku brzegowego na powierzchni metalu chłodzonego natryskiem wodnym wykorzystano rozwiązanie brzegowego odwrotnego zagadnienia przewodzenia ciepła. Badania eksperymentalne przeprowadzono dla próbki osiowosymetrycznej. Ze względu na specyficzną budowę czujnika wykorzystanego w badaniach, w algorytmie metody odwrotnej przetestowano dwa modele elementów skończonych opisujące geometrię próbki. Pierwszy model upraszczał geometrię próbki do postaci „zwykłego” walca, drugi model opisywał rzeczywisty kształt próbki. W pracy testowano również dwa modele aproksymacji warunku brzegowego.