A mathematical model of the double-pipe system with TBCs application

Department of Thermal Processes, Air Protection, and Waste Utilisation Cracow University of Technology, Cracow, Poland

^* Corresponding author: mariusz.granda@pk.edu.pl

Abstract

Following Rankine’s cycle efficiency, steam with ever-higher parameters is used to improve the efficiency of advanced ultra-supercritical power plants. The high steam parameters require the use of expensive high-alloy steels. Therefore, design concepts with reduced investment costs are more and more popular. In the power industry, the use of thermal barrier coatings to protect components exposed to high temperatures is becoming ever more common. The innovative concept is a double-pipe system with a thermal barrier that provides insulation for the primary pipe, in which ultra-supercritical steam flows. On the outside, the pipe is cooled by lower performance steam. The following paper presents a two-dimensional mathematical model of the proposed solution. A set of heat transfer equations allows the determination of the temperature field in the steady and transient-state operation of such a system. The numerical model is compared with the CFD one. The temperature gradient in the inner pipe wall with and without coating was determined. In addition, the response of the wall temperature to the step-change of the steam temperature was investigated. The paper shows that the use of TBCs allows reducing high-alloy steels and improving the handling properties of thick-walled components.