Heat Transfer at Gas- and Coolant Side

The development of modern combustion engines has considerably increased the output of specific power. The need of a higher capacity of the engine's cooling system resulted in the attempt to increase the heat transfer by allowing for local boiling of the liquid coolant in regions subject to a high thermal load. The numerical simulation of this very complex multi-phase heat transport requires realistic models. At the ISW a test channel designed particularly for subcooled boiling flow experiments has been installed. The experiments on this device investigated a set of boiling flow conditions which are typically found in the liquid cooling system of internal combustion engines. Thereby, the main focus lied on the effect of the motion of the fluid on the bubble dynamics. Based on the experimental data and the large set of boiling curves obtained from these a boiling model could be successfully developed. The proposed model has already been employed in the simulation of an entire cylinder block, where it gave promising results. In the ongoing and future work our major subjects in this field will be the validation of the boiling model for pure water as coolant medium, as well as the experimental investigation of several effects which have proven to be relevant in subcooled boiling, like surface roughness, surface orientation, contamination of the surface, and surface vibration. Based on these investigations it is intended to modify the boiling model to capture these effects as well.