Heat exchanger

Claim 1

A HEAT EXCHANGER FOR USE IN A BATH OF A FIRST LIQUID CRYOGENIC FLUID TO PROVIDE HEAT TRANSFER BETWEEN SAID FIRST CRYOGENIC FLUID AND ANOTHER CRYOGENIC FLUID, THE IMPROVEMENT COMPRISING: A PLURALITY OF CLOSED SANDWICH ELEMENTS EACH INCLUDING A PAIR OF SPACED APART SIDE WALLS HAVING SMOOTH PLANAR OUTER SURFACES AND FORMING THEREBETWEEN FIRST AXIAL FLOW PASSAGES, A PAIR OF SPACED SEPARATION STRIPS EXTENDING AXIALLY ALONG RESPECTIVE EDGES OF OPPOSED SIDE WALLS OF ADJACENT SANDWICH ELEMENTS DEFINING SECOND AXIAL FLOW PASSAGES, THE STRIP OF EACH PAIR BEING OF DIFFERENT CROSS-SECTIONAL WIDTH AND CONVERGING IN THE DIRECTION OF A COMMON AXIS, AND A PAIR OF AXIALLY SPACED HEADER STRUCTURES CONNECTED TO OPPOSED ENDS OF THE HEAT EXCHANGER AND IN FLUID COMMUNICATION WITH SAID FIRST AXIAL PASSAGES FOR MOVING SAID SECOND CRYOGENIC FLUID ALONG A FLOW PATH PARALLEL TO THE FLOW PATH OF SAID FIRST CRYOGENIC FLUID, SAID SEPARATION STRIPS HAVING SMOOTH PLANAR SURFACES FOR DEFINING, WITH SAID SMOOTH PLANAR OUTER SURFACES OF SAID CLOSED SANDWICH ELEMENTS A FLOW PATH OF CONSTANT AXIAL CROSS-SECTION HAVING SMOOTH PLANAR BOUNDARIES TO MINIMIZE THE DEPOSIT OF CONTAMINANTS UPON SUBMERSION OF SAID HEAT EXCHANGER INTO SAID FIRST CRYOGENIC LIQUID BATH.