Calculation of Roughness Effects in Cooling Channels for Thermal Conduction of an Air Cooled Electrical Excited Synchronous Machine

The roughness of the laminated iron sheets in the cooling channel has an influence to the thermal conductance between air and iron package. In this paper the thermal behavior of an electrical excited synchronous machine with air cooling was simulated with an CFD program and a lumped parameter model. The results are compared to the measurement of a constructed machine. The machine is also used to get the values of roughness in the application. This measured values are recalculated to the equivalent sand corn roughness used in the simulation. The lumped parameter model is updated with a new simulation module to simulate the roughness of the sheets in the air flow channel. The necessity is shown in the results of a further paper where the correction parameter of the conductivity were to high. With the implemented roughness the lumped parameter model is verified to the measurement and CFD simulation. The results show a reduction of the necessary correction parameter in the lumped parameter model. In consequence the model calculation accuracy is raised.