Liquid metal operated heat exchanger

This invention relates to a heat exchanger arrangement of the shell and tube type especially adapted for the use of high temperature liquid metal as a heating medium. The arrangement incorporates a tube bundle comprising a plurality of bayonet tube assemblies through which the liquid metal is circulated in indirect heat exchange relation with vaporizable fluid that flows through the shell. The tube assemblies incorporate a double walled bayonet tube containing a gas space which provides a thermal barrier to minimize heat loss from the heating medium. Various embodiments of evaporator and evaporator-superheater organizations utilizing the heat exchanger arrangement are described. (U.S.)