LARGE COAXIAL COLDFINGER PTC FOR PROCESS LIQUEFACTION AND HTS APPLICATIONS

Large (>100 W cooling capacity at 80 K) ‘pulse‐tube’ coolers are ideal candidates for emerging applications such as HTS transmission lines, transformers, and motor windings, meso‐scale oxygen liquefaction on‐demand, cryopumping, and cryogen boiloff recovery. A number of successful large ‘in‐line’ pulse‐tube coolers have been built, but these require embedded shell‐and‐tube process heat exchangers, hence transport of the process fluid/gas to and from the coldhead, and often a high degree of process fluid purity, to avoid clogging in the narrow inlets and outlets of these heat exchangers. It is far preferable in most circumstances to have a coldfinger design that presents a salient cold tip, with the coldhead at the end of a flexible transfer line, as is done with Gifford‐McMahon or Joule‐Thomson coolers. This paper presents some design details and data from the development of our first high‐capacity coldfinger, as well as the results of its application to a 55 gallon/day oxygen liquefier for the Navy.