Heat exchanger header with refrigerant distribution by capillary wicking porous insert

Abstract

A heat exchanger including a tube stack having a plurality of microtubes configured to transfer heat from a refrigerant to an external fluid. The heat exchanger includes an inlet housing disposed adjacent to a fluid-inlet side of the tube stack. The inlet housing includes a reservoir where refrigerant is stored and where, due to gravity, liquid of the refrigerant pools in a bottom of the reservoir. The heat exchanger includes a wicking insert disposed at a tube stack opening of inlet housing adjacent to and covering the fluid-inlet side of the tube stack. The wicking insert has a porous structure configured to provide a capillary force within the porous structure, and is disposed within the pooled liquid to draw the liquid from the bottom of the reservoir through the porous structure of the wicking insert by the capillary force.

What is claimed is: 
     
         1 . A heat exchanger comprising:
 a tube stack assembly including a plurality of microtubes, the tube stack assembly having an inlet end and an outlet end;   an inlet housing disposed adjacent to the inlet end of the tube stack assembly, the inlet housing including a reservoir; and   a wicking insert disposed in the inlet housing, and positioned adjacent to and covering the inlet end of the tube stack assembly, wherein the wicking insert has a porous structure configured to provide a capillary force within the porous structure;   wherein the wicking insert is configured to be at least partially disposed in a refrigerant fluid within the reservoir, and the wicking insert is configured to draw the refrigerant fluid from the reservoir through the porous structure of the wicking insert due to the capillary force; and   wherein a thickness of the wicking insert varies along the inlet end of the tube stack assembly.   
     
     
         2 . The heat exchanger of  claim 1 , wherein the thickness varies in a concave shape or a convex shape. 
     
     
         3 . The heat exchanger of  claim 1 , wherein the thickness varies in a parabolic shape. 
     
     
         4 . The heat exchanger of  claim 1 , wherein the thickness varies in a conic shape. 
     
     
         5 . The heat exchanger of  claim 1 , wherein a thickness of the wicking insert is defined as spanning from an inner surface of the wicking insert, disposed adjacent to the inlet end of the tube stack assembly, to an outer surface, opposite the inner surface, and disposed adjacent to the reservoir. 
     
     
         6 . The heat exchanger of  claim 5 , wherein the thickness of the wicking insert is greatest at a center of the wicking insert. 
     
     
         7 . The heat exchanger of  claim 5 , wherein the thickness of the wicking insert is smallest at a center of the wicking insert. 
     
     
         8 . The heat exchanger of  claim 5 , wherein at least a portion of the inner surface is not parallel with a portion of the outer surface. 
     
     
         9 . The heat exchanger of  claim 8 , wherein an entirety of the inner surface is not parallel with the outer surface. 
     
     
         10 . The heat exchanger of  claim 1 , wherein the inlet housing includes an inlet header, wherein a fluid is configured to enter the inlet housing via the inlet and be stored in the reservoir. 
     
     
         11 . The heat exchanger of  claim 1 , further comprising a compressor or a pump coupled to tube stack assembly. 
     
     
         12 . The heat exchanger of  claim 11 , wherein the capillary force are configured to evenly distribute the refrigerant fluid among the wicking insert for even distribution to the plurality of microtubes. 
     
     
         13 . The heat exchanger of  claim 1 , wherein a pore density of the porous structure of the wicking insert is uniform throughout the wicking insert. 
     
     
         14 . The heat exchanger of  claim 1 , wherein the porous structure includes a gradient pore density, and wherein a pore density is largest adjacent to the tube stack assembly. 
     
     
         15 . The heat exchanger of  claim 1 , wherein one or more of the plurality of microtubes comprises a microtube wicking insert disposed within an interior of the one or more of the plurality of microtubes. 
     
     
         16 . The heat exchanger of  claim 1 , wherein the tube stack assembly further comprises an end plate having an inner face coupled to the inlet end of the plurality of microtubes, and wherein the end plate includes a plurality of through-holes, wherein each through-hole of the plurality of through-holes aligns with one microtube of the plurality of microtubes. 
     
     
         17 . An inlet assembly for providing a refrigerant fluid to a plurality of microtubes for a heat exchanger, the inlet assembly comprising:
 an inlet housing including a reservoir; and   a wicking insert positioned within the inlet housing and at least partially within the reservoir, the wicking insert having a porous structure and configured to provide a capillary force by the porous structure to draw a fluid from the reservoir into the wicking insert; and   wherein the wicking insert includes a first surface and a second surface opposite of the first surface, wherein a thickness for the wicking insert is defined between the first surface and the second surface, and wherein the thickness for the wicking insert varies along at least a portion of the wicking insert.   
     
     
         18 . The inlet assembly of  claim 17 , wherein the porous structure for the wicking insert has pore sizes that are greater than or equal to 0.2 microns and less than or equal to 100 microns. 
     
     
         19 . The inlet assembly of  claim 17 , wherein the wicking insert includes a parabolic shape. 
     
     
         20 . The inlet assembly of  claim 17 , wherein the wicking insert includes a conic shape.