Experimental and numerical investigation of effects of helical turbulators in concentric tube heat exchangers

In this study, the heat transfer performance and friction characteristics of a concentric tube heat exchanger with different pitch of helical turbulators were investigated experimentally and numerically for Reynolds number range of 3000 to 14000. Therefore, an experimental system was established to obtain experimental data. Air as a hot fluid and water as a cold fluid were passed through the inner tube and outer tube of the heat exchanger, respectively.In the numerical study, the basic conservation equations in steady-state, three-dimensional (3D) and turbulent flow conditions were solved using a CFD computer code, FLUENT and by GAMBIT software for the model drawing and mesh. Conjugate heat transfers both conduction and convection was analyzed for all models.In the numerical calculation, cases corresponding to all experiments were solved by using the CFD computer code. In order to examine the effect of parameters on the heat transfer, velocity distributions and temperature contours inside the tube were obtained by the CFD code. Experimental and numerical results were compared and seen to be in a good agreement with each other. The heat transfer enhancement using helical turbulator was obtained as 291 %, 241 %, 218 % and 199 % of ratio than the smooth tube for pitch distances of p = 20, 40, 60 and 80 mm, respectively.