This project has been established by the Electrical Power Engineering Group at the University of Southampton to address some fundamental issues associated with the application of superconducting technology to power apparatus. One of the critical aspects for the application of high temperature superconductor (HTS) technology is suitable electrical insulation materials. In many HTS devices, liquid nitrogen (LN2) is a cheap and excellent cooling medium and also a good electrical insulator. However, bubbles are easily formed due to trapped vapour on surfaces during filling, thermally or electrically induced. These bubbles are known to reduce the breakdown withstand level.
This project is studying the thermally induced bubble dynamics and boiling process under electric fields. To date results have been obtained using rod-plane and inclined-plane electrodes. These results are useful for understanding electrohydrodynamic (EHD) phenomena influencing the bubble behaviour in liquid nitrogen and for developing a means of removing the gas from the cryostat of HTS transformers or fault current limiters (FCL) during âquenchâ. In addition, the EHD technique can be used as an effective heat transfer enhancement method in liquids. Obtained experimental results of liquid nitrogen boiling curves under applied electric fields will allow future cooling equipment to exploit this phenomena.