Heat Exchangers with Variable Unit-Area Thermal Conductivities

Abstract

A heat exchanger with a heat-exchanging portion is electrochemically deposited onto a base (for thermal coupling to a heat source) or directly on the heat source. The heat-exchanging portion comprises extensions that define openings (e.g., channels) for passing heat transfer fluid through the heat exchanger. The geometry of these c and/or openings varies throughout the exchange to achieve different unit-area thermal conductivities for at least two different portions of the heat-receiving surface. For example, the thickness, height, spacing, shape, and/or materials of the heat-exchanging extensions may be selected to achieve the desired heat transfer at each zone. This variability in unit-area thermal conductivities may be used to accommodate for “hot spots”, heating of the heat transfer fluid, fluid dynamics, and other factors associated with the heat exchanger operation. Electrochemical additive manufacturing (ECAM) is used to fabricate at least heat-exchanging extensions thereby enabling precise and zone-specific thermal transfer characteristics.

1 . A heat exchanger for use on a heat source comprising a heat-transferring surface, the heat exchanger comprising:
 a base comprising a heat-receiving surface for thermal coupling to the heat-transferring surface; and   a heat-exchanging portion electrochemically deposited on and attached to the base and comprising heat-exchanging extensions, wherein:
 the heat-exchanging extensions comprise heat-exchanging surfaces extending to the base, 
 a combination of the heat-exchanging surfaces and the base forms openings for circulating a heat transfer fluid through the heat exchanger, 
 the openings such that the heat transfer fluid directly interfaces the heat-exchanging surfaces while circulating through the heat exchanger, and 
 the heat-exchanging extensions are electrochemically deposited such that a unit-volume material to space ratio between the heat-exchanging extensions and the openings is different for at least two different portions of the heat-receiving surface. 
   
     
     
         2 . The heat exchanger of  claim 1 , wherein the heat-exchanging surfaces of the heat-exchanging extensions have a height (H) that is different at different parts of the heat-receiving surface. 
     
     
         3 . The heat exchanger of  claim 2 , wherein:
 the heat exchanger comprises a heat exchanger inlet and a heat exchanger outlet,   the heat exchanger inlet is configured to receive the heat transfer fluid into the heat exchanger,   the heat exchanger outlet is configured to discharge the heat transfer fluid from the heat exchanger, and   the height (H) increases along a pathway of the heat transfer fluid from the heat exchanger inlet to the heat exchanger outlet.   
     
     
         4 . The heat exchanger of  claim 1 , wherein:
 the heat-exchanging extensions are continuous fins having a thickness (T) defined by the heat-exchanging surfaces and two adjacent ones of the openings,   the thickness (T) is different at different parts of the heat-receiving surface.   
     
     
         5 . The heat exchanger of  claim 4 , wherein:
 the heat exchanger comprises a heat exchanger inlet and a heat exchanger outlet,   the heat exchanger inlet is configured to receive the heat transfer fluid into the heat exchanger,   the heat exchanger outlet is configured to discharge the heat transfer fluid from the heat exchanger, and   the thickness (T) changes along or perpendicular to a pathway of the heat transfer fluid from the heat exchanger inlet to the heat exchanger outlet.   
     
     
         6 . The heat exchanger of  claim 1 , wherein:
 the openings have an opening width (Wo), defined as an average space between any two closest pairs of the heat-exchanging surfaces,   the opening width (Wo) is different at different parts of the heat-receiving surface.   
     
     
         7 . The heat exchanger of  claim 6 , wherein:
 the heat exchanger comprises a heat exchanger inlet and a heat exchanger outlet,   the heat exchanger inlet is configured to receive the heat transfer fluid into the heat exchanger,   the heat exchanger outlet is configured to discharge the heat transfer fluid from the heat exchanger, and   the opening width (Wo) decreases along a pathway of the heat transfer fluid from the heat exchanger inlet to the heat exchanger outlet.   
     
     
         8 . The heat exchanger of  claim 1 , wherein:
 the heat-exchanging extensions are individual disjoined structures, extending perpendicular to the base,   each of the heat-exchanging extensions has a largest cross-sectional dimension different at different parts of the heat-receiving surface.   
     
     
         9 . The heat exchanger of  claim 1 , wherein:
 the heat-exchanging extensions are individual disjoined structures, extending perpendicular to the base,   each of the heat-exchanging extensions has a cross-sectional shape that is different at different parts of the heat-receiving surface.   
     
     
         10 . The heat exchanger of  claim 1 , wherein a cross-sectional shape is selected from the group consisting of a circle, an oval, a square, and a triangle. 
     
     
         11 . The heat exchanger of  claim 1 , wherein material composition of the heat-exchanging extensions differs at different parts of the heat-receiving surface. 
     
     
         12 . The heat exchanger of  claim 1 , wherein:
 the heat-exchanging surfaces of the heat-exchanging extensions have a height (H), and   material composition of the heat-exchanging extensions differs along the height (H).   
     
     
         13 . The heat exchanger of  claim 1 , wherein the base and the heat-exchanging portion have different compositions. 
     
     
         14 . The heat exchanger of  claim 13 , wherein:
 the base is formed from tungsten; and   the heat-exchanging portion is formed from copper.   
     
     
         15 . The heat exchanger of  claim 1 , wherein:
 the base comprises a base surface extending into and forming a bottom of the openings, and   the base surface is non-planar.   
     
     
         16 . The heat exchanger of  claim 15 , wherein the base surface comprises a set of base-surface protrusions, each having a shape selected from the group consisting of a cylinder, a pyramid, a hemispherical dimple, a trapezoidal rib, a sinusoid, and a square wave. 
     
     
         17 . The heat exchanger of  claim 16 , wherein the set of base-surface protrusions define a pitch between two adjacent ones in the set of base-surface protrusions such that the pitch varies along or perpendicular to a pathway of the heat transfer fluid. 
     
     
         18 . The heat exchanger of  claim 1 , wherein a surface area of the heat-exchanging surfaces of the heat-exchanging extensions, per unit area of the heat-receiving surface, changes along or perpendicular to a pathway of the heat transfer. 
     
     
         19 . The heat exchanger of  claim 1 , wherein the heat-exchanging surfaces of the heat-exchanging extensions comprise sidewall protrusions extending to adjacent one of the heat-exchanging surfaces. 
     
     
         20 . A heat source assembly comprising:
 a heat source comprising a heat-transferring surface; and   a heat exchanger comprising a base and a heat-exchanging portion, wherein:
 the base comprising a heat-receiving surface mechanically adhered to the heat-transferring surface, 
 the heat-exchanging portion is electrochemically deposited on and attached to the base and comprises heat-exchanging extensions, 
 the heat-exchanging extensions comprise heat-exchanging surfaces extending to the base, 
 a combination of the heat-exchanging surfaces and the base forms openings for circulating a heat transfer fluid through the heat exchanger, 
 the openings extend to the base such that the heat transfer fluid directly interfaces the base and the heat-exchanging surfaces while circulating through the heat exchanger, and 
 the heat-exchanging extensions are electrochemically deposited such that a unit-volume material to space ratio between the heat-exchanging extensions and the openings is different for at least two different portions of the heat-receiving surface.