fig3 b arranged in an alternating pattern or sandwich pattern the minimum number of fig3 a type layers 40 a required to ensure complete filling of the passages 45 47 55 57 with kettle liquid and shelf liquid could be determined and implemented independently of number of fig3 b type layers 40 b for the nitrogen rich streams required to achieve the desired sub cooling of the cryogenic liquid streams as illustrated the flow of the nitrogen rich stream c within each fig3 b type layer 40 b is a gravity assisted flow in a generally downward orientation from the nitrogen rich stream inlet 62 to one or more nitrogen rich stream outlets 66 conversely the flows of the kettle liquid a and shelf liquid b within each fig3 a type layer 40 a are against gravity in a generally upward orientation through the heat exchanger main body 30 in both heat exchanger segments 32 34 note the cryogenic liquid inlets 42 44 52 and 54 are disposed vertically below the corresponding cryogenic liquid outlets 46 48 56 and 58 such that the overall flow of the cryogenic liquids is in an upward flow orientation in both heat exchanger segments 32 34 in addition the cryogenic liquid passages 45 47 within each of the fig3 a type layer 40 a in the first heat exchange segment 32 and the passages 55 57 within each of the fig3 a type layer 40 a in the second heat exchange segment.