Falling film evaporator with a two-phase flow distributor

A falling film evaporator for receiving two-phase refrigerant flow from an expansion valve and delivering refrigerant vapor to a compressor, comprising:

• a plurality of heat transfer tubes supported by tube sheets and adapted to conduct the flow of liquid to be cooled therein;
• a header disposed vertically above said heat transfer tubes for receiving two-phase refrigerant flow from an expansion valve and conducting the flow to plurality of header outlets;
• and a plurality of subheaders disposed vertically above said heat transfer tubes, each of said subheaders comprising:
• an inlet for receiving two-phase refrigerant flow from a header outlet;
• a first pass conduit for receiving refrigerant from said inlet and further conducting said flow to a return bend for reversal of refrigerant flow direction, said first pass conduit having in a lower surface thereof a plurality of openings formed therein for conducting the flow of refrigerant downwardly;
• a second pass conduit disposed vertically under said first pass conduit for internally receiving refrigerant from said return bend and for externally receiving, on an upper surface thereof, refrigerant flow from said plurality of openings, with the refrigerant then flowing over an outer surface of said second pass conduit to said heat transfer tubes below.

A method of distributing two-phase refrigerant flow to a plurality of heat transfer tubes in an evaporator, comprising the steps of:

• providing a header in a vertical disposition above the heat transfer tubes for receiving two-phase refrigerant flow from an expansion valve said header having first and second pass conduits,
• providing a nozzle in an inlet of said header for propelling refrigerant flow from said inlet through said first and second pass conduits;
• and
• providing for the flow of two-phase refrigerant flow from said first pass conduit to a plurality of subheaders and for further distribution to said heat transfer tubes.