Counter-flow cooling of a transmission line by supercritical helium

The task of cooling a superconducting power transmission line in which the 'go' and 'return' streams of supercritical helium are in thermal contact through the cable dielectric is examined both analytically and using an exact numerical solution to the flow equations with real helium properties. Temperature and pressure distributions are given for level and inclined terrain, an acceptable range of dielectric thermal conductivity is established, and the theoretical minimum refrigerator power is computed; the latter is compared with power computed for a real refrigerator. (author)