Uneven liquid flow distribution in radial ducts in transformer winding cooling systems shown by CFD and experimental measurements

摘要

Determination and optimisation of the winding hot-spot temperature is essential for managing the loading capability and thermal ageing of transformers. The liquid flow in the various winding cooling ducts directly impacts the position and temperature of the hot-spot. This paper uses experimental measurements using particle image velocimetry (PIV) on a test rig and computational fluid dynamics (CFD) to model the flows in a zig-zag type directed flow disk type winding cooling system to show how the flow distribution, hot-spot position and temperature varies with flow rate. Traditional thermal-hydraulic network models which are commonly used to predict flows and hot spot temperatures do not predict some of the phenomena observed, such as reverse flow at high and low flow rates and consequently have a restricted range of flow rates where they produce accurate results. These results are very important for good thermal design and this research shows for example, that increasing already high liquid flow rates does not necessarily lead to reduced temperatures.