This paper presents an experimental investigation and computer simulation of motor cooling sleeves in machine tools' spindles in order to examine their thermo-energetic behavior. First of all, most typical designs of cooling sleeves are identified, e. g. the single helical and the double helical channel structure. The paper highlights the simulation of these different cooling sleeve designs by means of network models with lumped parameters and computational fluid dynamics (CFD). With the help of CFD analyses, which can also take the conjugate heat transfer (CHT) into account, a profound understanding of the flow effects and the complex thermo-energetic exchange processes between the body and the flowing inside can be achieved. Because these very exacting CFD models require lengthy computation times, they have to be reduced to time-saving calculation models like network models. This step is essential for the planned integration in the control of the machine tool in order to correct the tool center point (TCP) errors due to thermo-elastic deformations. Finally, the developed thermo-hydraulic models are validated against measurements on a developed test rig utilizing thermocouples and a thermographic camera to capture temperatures. The results demonstrate that the presented models allow a sufficiently accurate characterization of the thermo-energetic behavior of motor spindles' cooling sleeves in order to achieve enhanced prediction of the temperature distribution as well as an increase in manufacturing accuracy. In conclusion, it is shown how the resulting network calculation models can be used within the project group by integrating them into the complete model of the virtual machine tool in order to predict and correct its thermo-elastic deformations that will be part of the ongoing investigations.