NOVELTY - A process stream is cooled by indirect heat exchange with a cooled process refrigerant stream in a process heat exchanger, to yield cooled process stream(s) and a warm process refrigerant stream. The cooled process refrigerant stream comprises portion(s) of cooled primary refrigerant stream, and is obtained by cooling a refrigerant stream in a heat exchanger.    USE - For refrigerating a process stream, especially useful when the process stream has high flow rate and requires multiple parallel heat exchangers.    ADVANTAGE - A process stream is processed inexpensively by a simple method, using a simple system. The feed handling capacity of the system used for processing a stream is increased and the cost of multiple heat exchangers are reduced. Elimination of several refrigeration streams reduces the size of heat exchangers and complex refrigerant piping. Refrigeration of the process stream is carried out inexpensively, by providing multiple refrigerant streams to multiple, parallel process heat exchangers.    DETAILED DESCRIPTION - A process stream (201) is cooled by indirect heat exchange with a cooled process refrigerant stream (231), in a separate process heat exchanger (207), to yield cooled process stream(s) and a warm process refrigerant stream (233). The cooled process refrigerant stream comprises portion(s) of cooled primary refrigerant stream (225), and is obtained by cooling a refrigerant stream (217), selected from several open-loop refrigerant streams, by indirect heat exchange with other open-loop refrigerant streams (221,223) in a refrigerant heat exchanger (219).    An INDEPENDENT CLAIM is included for a heat exchanger system for cooling a processed stream.    DESCRIPTION OF DRAWING(S) - The figure shows the schematic flow diagram of dephlegmator heat exchanger system.    Process stream (201)    Process heat exchanger (207)    Refrigerant stream (217)    Refrigerant heat exchanger (219)    Open-loop refrigerant streams (221,223)    Cooled primary refrigerant stream (225)    Cooled process refrigerant stream (231)