Abstract: An improved boiler for liquefied gases comprises at least one heat transfer surface having means for creating a falling film of liquefied gas from its upper to lower end and means to heat the surface above the temperature at which the liquefied gas boils at the prevailing pressure. The subject apparatus is particularly suited for reboiling liquid nitrogen or liquid oxygen.

Abstract: A heat exchanger has a plurality of main flow passages 2 for cooling fluid. Each main flow passage has associated with it at least one narrow channel 10 defined by a surface of the main flow passage and an auxiliary surface on a separator plate 8. Relatively hot fluid flows over the separator plate 8 and heats the auxiliary surface such that bubbles formed in the channel are flattened by the surface opposite to the auxiliary surface and pressed against the auxiliary surface. The bubbles eventually pass through holes 12 in the channel 10 into the main flow passage 2 to rejoin the evaporating liquid pool.