A system for cooling a refrigerant includes (a) an evaporator comprising one or more lengths of tubing each having an upstream first cross-sectional area and a second downstream cross-sectional area, the second cross-sectional area being greater than the first cross-sectional area, the expansion in cross-sectional area between the first circular cross-sectional area and the second circular cross-sectional area being smooth and continuous; and (b) a compressor and a condenser for converting the refrigerant from a gas to a liquid for introduction into the evaporator.