Optimal current-lead design for the rolls of pierced-metal sheet

Abstract

An optimal current-lead design based on a spiral roll-up of pierced-metal sheet is presented wherein full consideration is given to the geometric shape and to the convective heat transfer to vapor permeating the lead. This lead design called PJR (pierced "jelly-roll") is an attractive option to a variety of superconducting systems because of its low cost ease of fabrication, mechanical ruggedness, and thermal stability. Energy balance equations for this lead are integrated with the temperature-dependent properties of the sheet metal. The effect of convective cooling with the extended surface area resulting from the metal piercing is included in terms of a new dimensionless parameter. The optimal heat flow distribution and the corresponding geometric lead parameter that minimizes the cooling load are calculated. Design data are presented for various geometric conditions and lead materials.