A vapor compression method and system including: a compressor configured to circulate a working fluid and operate at a plurality of operating conditions; an evaporator in fluid communication with the compressor, the evaporator heat exchanger comprising: a shell configured to allow the working fluid to flow therethrough; a plurality of parallel-spaced tubes disposed within the shell, the plurality of parallel spaced tubes configured to allow a heat transfer fluid to flow therethrough; and at least one baffle operably coupled to the plurality of parallel-spaced tubes, the at least one baffle configured to divide the shell into at least two chambers; an expansion valve assembly in fluid communication with the evaporator; and a control device operably coupled to the compressor and the expansion valve assembly, the control device configured to operate the valve assembly based at least in part on the plurality of operating conditions.