The Study For Heat Transfer Enhancement Structure Optimization Of Wall Turbulator Based On The Inverse Problem

In recent years, the theory research and application research of the inverse heat transfer problem have been gradually aroused the interest of many scholars. The inverse heat transfer problem widely exists in the natural science and engineering technology, such as aerospace、chemica、material processing、power engineering、metallurgical engineering and non-destructive testing etc. The inverse heat transfer problem(IHTP) is a typical among many inverse problems.Contrary to the direct problem, the inverse problem based on the internal/surface temperature or other easily measured physical quantities calculates the unknown parameters:thermal parameters、boundary conditions、heat flow、the geometry and the source term etc, which has important theoretical research value and practical significance.The inverse geometry convection heat problem is an important part of the inverse heat transfer problem.It is aimed to deduce the demanded shape through some measurable thermal properties.The method is to take the original structure of the turbulator as the initial conditions. When the other conditions are unchanged,we use the conjugate gradient method(CGM) combined with the sensitivity method and the adjoint gradient method, then through FLUENT、UDF technology and the dynamic mesh model to optimize the turbulator structure, so as to obtain the best heat transfer effect and the optimal turbulator structure.The difficulty and innovation of this paper:Firstly,the ill-posed of the inverse problem in mathematics makes the solution more difficult and complex than the direct problem.In addition, the study of the inverse heat transfer problem at home and abroad mainly focus on inverse heat conduction problem However there are few study on the inverse convection heat transfer problem.Because the inverse convection heat transfer problem considers the influence of flow.In this case,the ill-posedness is even more difficult to control.Finally, the author writes the conjugate gradient equation、the sensitivity equation and the adjoint equation compiled by C language.Then author combines the UDF user interface with the software of FLUENT, to optimize the structure of the turbulator and obtain the ideal enhanced heat transfer structure by dynamic mesh technique.In the shape optimization process, when the turbulator shape is changed, points of the boundary will be moving,so the whole adjacent grid also need to adjust, which involves the dynamic mesh.In this paper, we use the spring-based smoothing to change the grid coordinates and the local remeshing to smooth grid. Based on the above theory, we can use the optimization algorithm to design the optimal turbulator. The conjugate gradient method can effectively solve the inverse convective heat transfer problem,which can be verified through the optimized semicircle, triangular, hexagon and pentagon turbulator and the comprehensive heat transfer effect of the optimized turbulator is better than the turbulator before optimization.