Two-step numerical simulation of the heat transfer from a flat plate to a swirling jet flow from rotating pipe

Purpose: Impinging jets have been widely studied and the addition of swirl has been found to be beneficial to heat transfer. Since there is no literature on RANS nor experimental data of swirling jet flows generated by a rotating pipe, this paper attempts to fill such gap by providing results on the performance of this type of design. Design/methodology/approach: Since the flow has a different behaviour at different parts of the design, the same turbulent model cannot be used for the full domain. To over-come this complexity, the simulation is split into two coupled stages. This is an alternative to use the costly Reynold Stress Model (RSM) for the rotating pipe simulation and the SST k-ω model for the impingement. Findings: To induce swirl by rotating pipes with swirl intensity ranging from 0 to 0.5 affects the velocity profiles but not noticeably the spreading angle. The heat transfer is increased with respect to a non-swirling flow only at short nozzle-to-plate distances H/D < 6, where H is the distance and D is the diameter of the pipe. For the impinging zone, the highest average heat transfer is achieved at H/D = 5 with swirl intensity S = 0.5. This is the highest swirl studied in this work. Research limitations/implications: High-fidelity simulations or experimental analysis may provide reliable data for higher swirl intensities, which is not covered in this work with RANS. Practical implications: This two-step approach and the data provided is of interest to other related investigations (e.g. using arrays of jets or other surfaces than flat plates). Originality/value: This paper is the first of its kind RANS simulation of the heat transfer from a flat plate to a swirling impinging jet flow issuing from a rotating pipe. An extensive study of these CFD simulations has been carried out with the emphasis of splitting the large domain into two parts to facilitate the use of different turbulent models and periodic boundary conditions for the flow confined in the pipe