Multi-stage heat exchange apparatus and method

Claim 1

IN A METHOD FOR PROGRESSIVELY COOLING A LIQUID BY PASSAGE THEREOF THROUGH FIRST AND SECOND, SERIALLY CONNECTED COOLING STAGES OF A MULTISTAGE EVAPORATOR WHICH IS ADAPTED TO CONTAIN A LIQUID AND VAPOROUS COOLING MEDIUM THEREIN, THE STEPS OF, DIVIDING A STREAM OF SAID LIQUID AT ENTRY TEMPERATURE INTO FIRST AND SECOND STREAMS, PASSING SAID FIRST LIQUID STREAM THROUGH SAID FIRST COOLING STAGE OF SAID EVAPORATOR IN HEAT EXCHANGER RELATIONSHIP WITH SAID LIQUID COOLING MEDIUM WITH RESULTANT LOWERING OF THE TEMPERATURE OF SAID FIRST LIQUID STREAM BELOW SAID ENTRY TEMPERATURE, MAINTAINING THE TEMPERATURE OF SAID SECOND LIQUID STREAM AT SUBSTANTIALLY ENTRY TEMPERATURE AND MIXING SAID SECOND LIQUID STREAM WITH SAID FIRST LIQUID STREAM AFTER THE LATTER HAS BEEN PASSED THROUGH SAID FIRST COOLING STAGE TO PROVIDE AN INTERMIXED STREAM OF LIQUID AT AN INTERMEDIATE TEMPERATURE WHICH IS LOWER THAN SAID ENTRY TEMPERATURE, DIVIDING SAID INTERMIXED STREAM OF LIQUID INTO THIRD AND FOURTH STREAMS, PASSING SAID THIRD LIQUID STREAM