The effect of the nozzle geometry on the heat transfer rate of a confined turbulent impinging jet is investigated numerically. The open source code CFD program OpenFOAM is employed to conduct the numerical simulations. The turbulence is modeled through the RANS approach using the k-$omega$-SST-model. Numerically obtained Nusselt number distributions are compared to experimental findings. It is shown that predictions of the Nusselt number distributions are significantly improved when the nozzle geometry of the jet is included in the simulations. The improvements are more pronounced at higher Reynolds numbers. Separation phenomena inside the nozzles are observed and analyzed. Axial velocity and kinetic turbulence energy profiles at the nozzle outlet of simulations comprising nozzle geometry are compared with those of simulations with a uniform velocity inlet boundary. The effect of nozzle length is investigated numerically. It is shown that when the nozzle length is shorter than the reattachment length the overall heat transfer rate of the confined impinging jet is enhanced. The effect of inlet rounding of the nozzle is studied. The rounding of the inlet lessens separation, which in turn leads to an overall decrease in heat transfer.