Two-phase refrigerant distribution system for multiple pass evaporator coils
A multiple pass, parallel tube heat exchanger with a collection header extending along the length of each of a first and second pass, is provided with a bypass tube which fluidly interconnects the downstream end of the collection header to a midpoint thereof, near the end of the first pass tubes and the beginning of the second pass tubes so as to enhance the flow distribution of two-phase refrigerant from the collection header to the second pass tubes. The distribution flow is further enhanced by the insertion of an eductor nozzle within the collection header, and with the inlet of the eductor nozzle being supplied by refrigerant flow from the condenser to thereby provide a motive flow of two-phase refrigerant in the loop which includes the latter half of the collection header and the bypass tubes.
1. A heat exchanger of the type having a plurality of tubes in each of a plurality of passes, comprising:
a first header for receiving from a source, two-phase refrigerant flow and for diverting the flow to be distributed amongst a plurality of first pass tubes being disposed substantially orthogonal to said first header and substantially parallel to each other;
a second header disposed substantially orthogonal to said plurality of first pass tubes and fluidly connected thereto for receiving the two-phase refrigerant flow from said plurality of first phase tubes and for conducting the flow of refrigerant to a plurality of second pass tubes being disposed substantially orthogonal to said second header and being disposed substantially parallel to each other;
a third header being disposed substantially orthogonal to said plurality of second pass tubes and being fluidly connected thereto for receiving refrigerant flow therefrom; and
a bypass tube fluidly connected at its one end to a downstream end of said second header near a last second pass tube farthest from said first pass tubes and at its other end to an intermediate point of said second header adjacent a first second pass tube nearest to said first pass tubes, said bypass tube being capable of conducting the flow of refrigerant from said second header downstream end to said second header intermediate point and thereby aid in the uniform distribution of refrigerant flow to said second pass tubes.
2. A heat exchanger as set forth in claim 1 and including an eductor nozzle disposed in said second header near said intermediate point for receiving a booster flow of refrigerant in one end thereof and discharging a flow from the other end thereof in a direction substantially orthogonal to said second pass tubes.
3. A heat exchanger as set forth in claim 2 wherein said booster flow originates from the same source of refrigerant as that passing to said first header.
4. A heat exchanger as set forth in claim 3 wherein said source is a condenser.