Numerical Study Of Heat Transfer Of Turbulent Impingement Jet

Reynolds averaged Navier-Stokes (RANS) simulations and large eddy simulations were carried out respectively to investigate the heat transfer of jet impingement which is widely used in engineering application. Different turbulent models are used to assess their performance in the simulation of heat transfer of jet impingement. Simulations were also performed to study the heat transfer characteristics of jet impingement under different conditions.By using RANS, turbulent model such as RNG, V2F, SST and Reynolds stress turbulent models are adopted to study heat transfer of turbulent round jet and slot jet impingement on plane wall and curve wall respectively and to validate the turbulent model. Experimental cases with different non-dimensional distance between the jet exit and the target wall H/D used in experiment are simulated. Numerical simulation results show that the local Nusselt number distribution predicted by V2F turbulent model are in good agreement with experimental data, which especially obtains a good prediction of the second peak with a relatively small value of H/D. Numerical results of round jet impingement on curved wall heat transfer show that the V2F still has better performance in prediction of Nusselt number distribution. Entrainment effects on heat transfer from a round gas jet to a flat wall at high temperature difference were investigated with V2F model. The heat transfer coefficient was defined in terms of the difference between the heated wall temperature and the adiabatic wall temperature. The changes of local Nusselt number and the effectiveness with Reynolds number and the temperature difference between jet and environment was studied. Additionally, the influence of different kinds of qualitative temperature was analyzed. According to the results, the Nusselt number changes little with the temperature difference between jet and environment, and the effectiveness is independent of Reynolds number, but the effectiveness varies relatively large with the temperature difference between jet and environment. So it is acceptable to use heat transfer data from unheated jets for the heated jets if the temperature difference is not too high, while corresponding deviation becomes larger with the increase of the temperature difference.Large eddy simulations were carried to study the pulse jet and continuous jet impingement heat transfer on plane wall with the same air mass flow rate. The simulations results show that the large coherent structures was generated by jet shear layer instability. In the wall impingement region, complex flow structure was periodically appeared. The pulsed jet impingement could lead to larger heat transfer coefficient, especially in the stagnation point region where the maximum Nusslet number is double than the continuous jet impingement.