Application of Numeric Methods in Temperature Analysis of Steam Boiler's Membrane Wall
by
Mária Carnogurská
Department of Energetik. Technical University of Kosice, Slowakia

This contribution contains the results of the solution of temperature field in cross-section of a steam boiler's membrane consisting of a boiler and flat iron as 2D task. The calculation is made by the method of finite elements because the analytical methods of calculation do not make it possible to determine the temperature distribution in the membrane wall as a whole.

The basic physical model for the temperature analysis will be analysed. During heat flow from the furnace through the wall of the boiler, the outside part of the boiler's wall is stressed by pressure since the internal (colder) part opposes its free heat expansion. On the other hand, the internal part of the boiler is stressed by tension. The steam mixture inside the boiler is in the region of gauge pressure at the temperature of working mixture tm, therefore the resulting stress in the boiler's wall is given by the sum of stress due to temperature and stress due to overpressure.

The present-day methods of temperature stress load are based on the work of Werne. The relations for the calculation of temperatures in critical places of the boiler are specific and they are derived from the basic relations valid for heat transmission. They make it possible to determine the temperature at the peak of the boiler, the temperature in the wall of the membrane from the side of heat radiation, and the temperature at the internal side of the boiler.

The solution made in this contribution is based on the application of numeric methods contained in COSMOS/M program leaning on control equation of heat transmission in solid body with suitable boundary conditions.

The results of temperature distribution are analysed in this contribution for the membrane wall with constant thickness of the attached flat iron and with variable thickness. At the same time the stress conditions due to temperature stress of the membrane wall are also determined.

Date received: January 31, 2000