Investigation of Elliptical Cooling Channels for a Naval Electromagnetic Railgun

Elliptical cross sections were examined for the design of cooling channels subject to biaxial and uniaxial compressive loading conditions based on an Electromagnetic (EM) Railgun. Elliptical shapes were considered due to the high surface area available for convection, relatively low impact on the stress distribution, and low stress concentration effect. The heat transfer capability of elliptical channels is maximized based on the applied heat flux and given flow conditions, by treating the channel as a variable area fin and varying the major and minor axis of the elliptical cross-section channel as well as the distance between channels. The optimal channel shape is further constrained by the applied compressive stresses. In order to test the thermal aspect of the design, a representative set of channels were machined into 1/3 scale copper rails using wire EDM. Tests were performed using a steady state heat flux to determine the overall heat transfer coefficient in order to verify the thermal calculations. In order to verify the structural aspect of the design, a numerical study of the stress concentration factors was performed. The results of both the thermal testing and numerical study were found to be in reasonable agreement with the prediction results.