The thermal conditions inside switch cabinets for industrial applications without cooling devices are equally influenced by natural convection and radiation heat transfer. In this work the open source library OpenFOAM is applied and enhanced, in order to simulate the temperature field of the air inside the cabinet. Turbulent natural convection heat transfer is modeled using Menter's SST model. Radiation heat transfer is modeled using a surface-to-surface model, whereas the view factors are computed based on a Monte Carlo algorithm. Numerical results obtained with different flow models are compared with measurements and correlations from literature for a cavity and a Rayleigh-Bénard test case. The Radiation model is validated against comparative numerical data. Finally, the models are applied to calculate the temperature field of a switch cabinet test rig. These numerical results are compared with experimental data.