Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering (MCM'21)
Prague, Czech Republic Virtual Conference – August, 2021
Paper No. HTFF 140
DOI: 10.11159/htff21.140

Heat Transfer in High-Temperature Contact Processes with theParticipation of the Oxidized Layer
1

Aleksandra Przyłucka1, Marcin Rywotycki1

Department of Heat Engineering and Environment Protection, Faculty of Metals Engineering and Industrial Computer
Science, AGH University of Science and Technology
Czarnowiejska 66, 30 - 059 Krakow, Poland
aprzylucka@agh.edu.pl; rywotyc@agh.edu.pl

Extended Abstract

The heat transfer mechanism at the contact of two solids surfaces is common in technological processes related to themetallurgical and processing industries. It can be found in devices that use waste heat, such as thermoelectric generators [1].
The heat transfer between the generator surface and the exhaust collector surface requires the determination of the heat flux
flowing among them. Its value depends on: the type of materials used, the pressure force, the roughness and the presence of
the intermediary medium. The correct description of the process requires the knowledge of the value of the above-mentioned
flux or the value of the heat transfer coefficient as a function of the pressure force and temperature function. The heat transportmechanism at the contact also occurs in high-temperature processes, i.e., forging, hot rolling and continuous casting of steel.
Their characteristic feature is a large temperature difference between working tools. Changing the surface temperature of thetools involved in the contact has a significant effect on the value of the heat transfer coefficient through the contact [2]. The
heat flux between the tool and the workpiece depends on factors such as: temperature, pressure, contact time, surface
roughness and oxide scale thickness. Determining the boundary conditions in the above-mentioned processes is necessary toobtain an accurate and unambiguous solution of the heat conduction equation. Their direct identification and designation arecomplicated to implement. The problem can be solved by building a process model.
The available literature [3-6] allows to divide the models describing heat transfer in contact into two groups. The firstone covers the issues defining the constant, average value of the heat transfer coefficient. On the other hand, the models of
the second group describe the variable value of this coefficient in functions of the surface temperature at constant pressure
or variable pressure at a constant temperature. Due to the omission in numerical calculations of the pressures influence on aconstant heat transfer coefficient value, there are no precise results of the temperature field in high-temperature processes.
The main research objective of this work is to determine the dependence of the heat transfer coefficient at the contact asa function of surface temperature and pressure, taking into account the oxidized layer. This should be a form of mathematical
relationships that can be easily implemented in numerical calculations. The presented work covers the realization of several
partial research tasks. The experimental part consists in measuring temperature changes at specific points in two steel samples
in contact. One of the cylindrical samples is heated at temperature above 1000ºC using an electric furnace. Then the hydraulicpress subtends it with a given force against the cold sample. Thermocouples mounted in the axis of the samples allow torecord the temperature changes during the experiment. The obtained results constitute a reference point for the numericalsimulation of the two-dimensional model of the oxidation layer growth and numerical calculations of the heat flux on thecontact surface using the inverse method to determine the heat flux and heat transfer coefficient. The developed dependenciesof changes in the heat transfer coefficient can be used during numerical calculations of industrial processes in which contact
mechanisms occur.

References[1] L.S. Hewawasam, A.S. Jayasena, M.M.M. Afnan, R.A.C.P. Ranasinghe, M.A. Wijewardane, “Waste heat recovery fromthermo-electric generators (TEGs),” Energy Rep., vol. 6, supp. 2, pp. 474-479, 2020.
[2] M. Rosochowska, K. Chodnikiewicz, R. Balendra, “A new method of measuring thermal contact conductance,” J.
Mater. Process. Technol., vol. 145, no. 2, pp. 207-214, 2004.

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[3] F. Biao, T. Jing, Z. Yu-Hong, F. Li-Wu, Y. Zi-Tao, “An improved steady-state method for measuring the thermal contact
resistance and bulk thermal conductivity of thin-walled materials having a sub-millimeter thickness,” Appl. Therm. Eng.,
vol. 171, 114931, 2020.
[4] S. Mosayebidorcheh, M. Gorji-Bandpy, “Local and averaged-area analysis of steel slab heat transfer and phase change
in continuous casting process,” Appl. Therm. Eng., vol. 118, pp. 724-733, 2017.
[5] O.K. Panagouli, K. Margaronis, V. Tsotoulidou, “A multiscale model for thermal contact conductance of rough surfaces
under low applied pressure,” Int. J. Solids Struct., vol. 200-201, pp. 106-118, 2020.
[6] F. Wen-Zhen, G. Jian-Jun, C. Li, T.A. Wen-Quan, “A multi-block lattice Boltzmann method for the thermal contact
resistance at the interface of two solids,” Appl. Therm. Eng., vol. 138, pp. 122-132, 2018.

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