Akshay A. More
Department of Applied Mechanics , IIT Madras, Madras-600036, India
Department of Chemical Engineering Indian Institute of Technology Madras 600 036 India
Arul Prakash K
Thermo-Fluid Dynamics Laboratory, Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai-600036, India
In this paper, the effect of waviness and pyramidal fins on the enhancement of heat transfer and variations in thermal stresses of the tubes due to distribution of the recirculation zone is studied and compared with the Conventional circular tube (CCT) design. The symmetric and asymmetric distribution of temperature on the tube wall due to geometric modification and its effect on thermal stresses is studied using finite element method based commercial software ANSYS WORKBENCH (20.2).
Three-dimensional governing differential equations of fluid
flow and energy is solved using finite volume method based
commercial software ANSYS Fluent (20.2) with k-ω SST turbulence model as turbulence closure. Grid convergence
study is done on the computational domain to get optimal mesh and then heat transfer results of an optimal mesh is validated with the experimental data. The wavy nature of the tube is mainly responsible for the generation of the recirculation zones as we are having the convergent and divergent sections. This recirculation zone (Vortex zone) plays a major role in enhancing the heat transfer by mixing of the fluid. Numerical simulations shows that in case of the Wavy circular tube (WCT) generated recirculation zone always remains attached to the wall of the tube, hence responsible for the asymmetric temperature distribution over the cross-section of tube walls. In contrast, the finned wavy circular tube (FWCT) generated recirculation zone no longer remains attached to the wall of the tube due to provision of internal fins and hence gives enhanced mixing compared to the WCT design. Waviness and internal fins enhance the heat transfer but at the same time both are responsible for the asymmetric temperature distribution over the cross-section of tube and hence thermal stress studies are essential. The influence of geometric modifications, inlet temperature and mass flow rate of fluid on thermal stress and heat transfer variation is studied and discussed.