Numerical Simulation Of Heat Transfer Performance In Tube Inserted With Wire Mesh

With the energy crisis, environmental degradation and other issues becoming increasingly severe, improving energy utilization efficiency and developing renewable and clean energy dominate the new energy revolution. Heat transfer equipments are widely used in engineering files as energy transfer and transformation tools, such as petroleum, chemical, power, mining etc. Therefore, it is an efficient way to relieve the energy crisis by developing high-efficiency and compact-structure heat transfer equipments. This paper presents two novel enhanced heat transfer tubes. The flow and heat transfer performance is studies by numerical method with water as the working fluid, under constant heat flux boundary conditions, indicating the principles of heat transfer enhancement.First, the heat transfer tube inserted with mesh cylinder is proposed in this paper. Micron-sacle mesh screen, centimeter-scale diameter and meter-scale tube constitute a complex multi-scale computational model. Since the enormous quantity of screen mesh and the difficulty of mesh generation, it develops the equal equivalent diameter and flow area criteria, turning 3D mesh into 2D mesh. Through bridging mesh, it links mesh of micron level and mesh in mainstream region reasonably. The numerical results are compared with experimental data to ensure the reliability and accuracy. The study indicates that both enhanced and deterorated heat transfer region occure in the heat transfer tube, and there is a strong linear relationship between the length of enhaced region and Reynolds number. The periodic enhanced haet transfer tube is then further proposed based on the linear relationship, with segmented mesh cylinder inserted. The results showed that, ① periodically enhanced heat transfer tubes can achieve full-length heat transfer enhancement, eliminating deterioration area;②velocity and temperature fields are effectively modulated. New velocity distribution happens with larger velocity and velocity near the wall so that the boundary thickness gets thinner.Secondly, the study of the effects of the mesh cylinder exit head in perodical enhanced heat transfer tube on the performance is further carried on. Comparing the performance of heat transfer tube with none head, solid head and porous mesh head, the results shows that the tube with solid exit head performs best and the tube with none exit head performs worst.Finally, the mesh cone is proposed to replace the mesh cylilnder to create a new enhace heat transfer tube.Compared with the bottom surface perpendicular to the side surface of cylinder, the tapered bottom surface can effectively reduce the flow resistance. Three different wire bottom diameter(δ/D=0.6,0.7,0.8), the spacing (S/D=2,2.5,3) and mesh size (PPI=80,200,400) compose 27 groups structural parameters. The influences of parameters on heat transfer performance are studied by laminar flow model and perodic boundary condition, selecting the optimal parameter group. The results showed that,① the larger mesh bottom diameter δ and mesh cone interval S, the more excellent overall heat transfer performance; ②the influences of mesh size is related to the working condition. Re<400, the heat transfer tube with small PPI mesh cone performs better; 400<Re<800, the heat transfer tube with middle PPI mesh cone performs better; Re> 800, the heat transfer tube with large PPI mesh cone performs better.