*Article* **Numerical Simulation of Flow and Heat Transfer of a Discontinuous Single Started Helically Ribbed Pipe**

**Simon Kügele 1,\*, Gino Omar Mathlouthi 2, Peter Renze <sup>1</sup> and Thomas Grützner <sup>3</sup>**


**Abstract:** In the present study, the turbulent flow field and the heat transfer in a single started helically ribbed pipe with a discontinuous rib are investigated. A large-eddy simulation (LES) technique is applied in a pipe section with cyclic boundary conditions. The aim of this study is to explain and further analyze the findings from the heat transfer measurements at such complex structures with the help of detailed flow simulations. The simulation results are validated with measurements at a Reynolds number of Re = 21,100 and a Prandtl number of Pr = 7 with water as fluid. The comparison clearly shows that the current method delivers accurate results concerning average flow field, turbulence quantities and local heat transfer. The results demonstrate that the applied method is capable of correctly simulating flows with heat transfer in complex three-dimensional structures. The overall heat transfer performance of the helically ribbed pipe with a discontinuous rib is compared to a smooth pipe and a continuous rib configuration. The impact of the interruption of the rib structure on pressure drop and heat transfer are analyzed in detail.

**Keywords:** large eddy simulation; pipe flow; heat transfer; ribbed tube
