Parallel flow evaporator with shaped manifolds

Abstract

A method is provided for mitigating two-phase refrigerant maldistribution in heat exchange channels of a parallel flow evaporator. An inlet manifold of the evaporator includes a first stage, at least one intermediate stage, and a final stage. Each stage includes an expansion chamber, a contraction chamber, and at least one heat exchange channel interconnecting the stage to an outlet manifold of the evaporator. The method includes throttling the two-phase refrigerant in the expansion chamber of each stage, flowing a portion of the throttled refrigerant through the at least one heat exchange channel to the outlet manifold, mixing and jetting the two-phase refrigerant in each contraction chamber to increase the velocity of the refrigerant, and passing the refrigerant out an exit of the outlet manifold.

1 . A method for mitigating two-phase refrigerant maldistribution in heat exchange channels of a parallel flow evaporator, the method comprising the steps of:
 providing a two-phase refrigerant to an inlet manifold of the evaporator, the inlet manifold comprising a first stage, at least one intermediate stage, and a final stage, each stage comprising an expansion chamber, a contraction chamber, and at least one heat exchange channel interconnecting the stage to an outlet manifold;   throttling the two-phase refrigerant in the expansion chamber of each stage;   flowing a portion of the throttled refrigerant through the at least one heat exchange channel to the outlet manifold;   mixing and jetting the two-phase refrigerant in each contraction chamber to increase the velocity of the refrigerant thereby; and   passing the refrigerant out an exit of the outlet manifold.   
   
   
       2 . The method as set forth in  claim 1 , wherein a plurality heat exchange channels interconnect one stage to the outlet manifold, and the step of flowing a portion of the throttled refrigerant includes flowing through the plurality of heat exchange channels. 
   
   
       3 . The method as set forth in  claim 1 , wherein the at least one heat exchange channel is fluidly connected to the expansion chamber. 
   
   
       4 . The method as set forth in  claim 1 , further including the step of balancing hydraulic resistances between the contraction stage and the associated heat exchange channel. 
   
   
       5 . The method as set forth in  claim 4 , wherein the hydraulic resistance of the contraction chamber is at least one and a half times lower than the hydraulic resistance of the associated channel. 
   
   
       6 . The method as set forth in  claim 1 , wherein the outlet manifold further comprises a first stage, at least one intermediate stage, and a final stage, each stage comprising an expansion chamber and a contraction chamber, the heat exchange channels interconnecting the stages in the inlet manifold to the stages in the outlet manifold. 
   
   
       7 . The method as set forth in  claim 6 , the heat exchange channels interconnecting the expansion chambers in the inlet manifold to the expansion chambers in the outlet manifold. 
   
   
       8 . The method as set forth in  claim 1 , wherein the mixing step comprises placing refrigerant-mixing inserts in the contraction chambers. 
   
   
       9 . The method as set forth in  claim 1 , wherein the heat exchange channels are microchannels. 
   
   
       10 . In a parallel flow evaporator comprising an inlet manifold, an outlet manifold, and a plurality of channels fluidly connecting the inlet manifold to the outlet manifold, a method for mitigating two-phase refrigerant maldistribution in the channels, the method comprising the steps of:
 partially evaporating the two-phase refrigerant through a repetitive series of stages in the inlet manifold, wherein each stage comprises an expansion chamber, a contraction chamber, and at least one of the channels; and   balancing hydraulic resistances between each stage and the associated channel.   
   
   
       11 . The method as set forth in  claim 10 , wherein the balancing step comprises configuring the hydraulic resistance of the contraction chamber to be at least one and a half times lower than the hydraulic resistance of the associated channel. 
   
   
       12 . The method as set forth in  claim 11 , wherein configuring the hydraulic resistance of the contraction chamber comprises sizing a cross-sectional area of the contraction chamber. 
   
   
       13 . The method as set forth in  claim 10 , wherein a refrigerant flow rate progressively decreases through the repetitive series of stages in the inlet manifold. 
   
   
       14 . The method as set forth in  claim 13 , wherein the expansion chambers of the repetitive series of stages in the inlet manifold comprise progressively smaller cross-sectional areas defining a cross-sectional area reduction ratio, the ratio being proportional to the progressively decreasing refrigerant flow rate. 
   
   
       15 . The method as set forth in  claim 13 , wherein the contraction chambers of the repetitive series of stages in the inlet manifold comprise progressively smaller cross-sectional areas defining a cross-sectional area reduction ratio, the ratio being proportional to the progressively decreasing refrigerant flow rate. 
   
   
       16 . The method as set forth in  claim 10 , further including the step of partially evaporating the refrigerant through a repetitive series of stages in the outlet manifold, wherein the stages comprise an expansion chamber, a contraction chamber, and at least one of the channels. 
   
   
       17 . The method as set forth in  claim 16 , wherein a refrigerant flow rate progressively increases through the repetitive series of stages in the outlet manifold. 
   
   
       18 . The method as set forth in  claim 16 , wherein the expansion chambers of the repetitive series of stages in the inlet manifold comprise progressively smaller cross-sectional areas, and the expansion chambers of the repetitive series of stages in the outlet manifold comprise progressively larger cross-sectional areas. 
   
   
       19 . The method as set forth in  claim 18 , wherein the progressively larger cross-sectional areas of the expansion chambers in the outlet manifold are proportional to the progressively smaller cross-sectional areas of the expansion chambers in the inlet manifold. 
   
   
       20 . The method as set forth in  claim 10 , wherein the heat exchange channels are microchannels.