Microchannel heat exchanger fabricated by wire electro-discharge machining

Abstract

The present invention provides panels for a microchannel heat exchanger core wherein the panels may have greater than about 36 fins per inch of the panel. The microchannels of the panels may have an aspect ratio of at least about 10. Panels are also provided having microchannels and fins on one side of the panel or on opposite sides of the panel. Methods are also provided for machining the panels of the present invention.

1 . A panel for a microchannel heat exchanger core comprising: 
 a plurality of microchannels, the microchannels having a defined depth and a defined width;    a plurality of fins, wherein the fins separate the microchannels by  5  providing walls for the microchannels; and    wherein the panel has a fin density of greater than about 36 fins per inch of the panel.    
   
   
       2 . The panel of  claim 1  wherein the microchannels have an aspect ratio of depth to width of at least about 10.  
   
   
       3 . The panel of  claim 2  wherein the aspect ratio is from about 10 to about 100 .  
   
   
       4 . The panel of  claim 1  wherein there are from about 40 to about 110 fins per inch of the panel.  
   
   
       5 . The panel of  claim 1  wherein the fins have a thickness of from about 0.0015 inches to about 0.009 inches.  
   
   
       6 . The panel of  claim 1  wherein the microchannels have a depth of from about 0.125 inches to about 0.500 inches.  
   
   
       7 . The panel of  claim 1  wherein the microchannels have a width of from about 0.009 inches to about 0.0165 inches.  
   
   
       8 . The panel of  claim 1  wherein the panel comprises a material wherein the material comprises aluminum alloys, stainless steel alloys, copper alloys, titanium alloys, iridium alloys, rhodium alloys, graphite, carbon-carbon fiber matrix composites, carbon-silicon composites, aluminum-silicon carbide composites, boron carbide, titanium carbide or titanium nitride.  
   
   
       9 . The panel of  claim 8  wherein the material is a low-density material  
   
   
       10 . The panel of  claim 9  wherein the low-density material is an aluminum alloy.  
   
   
       11 . A panel for a microchannel heat exchanger core comprising: 
 a plurality of microchannels, the microchannels having a defined depth and a defined width and an aspect ratio of depth to width of at least about 10;    a plurality of fins, wherein the fins separate the microchannels by providing walls for the microchannels; and    wherein the panel has a fin density of from about 40 to about 110 fins per inch of the panel.    
   
   
       12 . The panel of  claim 11  wherein the walls of a microchannel are parallel to each other.  
   
   
       13 . The panel of  claim 11  wherein the panel has from about 50 to about 80 fins per inch of the panel.  
   
   
       14 . The panel of  claim 11  wherein the aspect ratio is from about 15 to about 30.  
   
   
       15 . The panel of  claim 11  wherein each of the microchannels has a rounded bottom surface.  
   
   
       16 . The panel of  claim 15  wherein the rounded bottom surfaces have a radius of from about 0.005 inches to about 0.012 inches.  
   
   
       17 . The panel of  claim 11  wherein the plurality of microchannels and fins are disposed on only one side of the panel.  
   
   
       18 . The panel of  claim 11  wherein the panel further comprises a top side and a bottom side and the plurality of microchannels and fins are disposed on both the top side and the bottom side of the panel.  
   
   
       19 . A panel for a microchannel heat exchanger core comprising: 
 a top side and a bottom side;    a plurality of microchannels, the microchannels having a defined depth and a defined width and an aspect ratio of depth to width of at least about 10;    a plurality of fins, the fins separating the microchannels by providing walls for the microchannels and wherein there are greater than about 36 fins per inch of the panel; and    wherein the microchannels and fins are disposed on both the top and bottom sides of the panel.    
   
   
       20 . The panel of  claim 19  wherein the aspect ratio is from about 10 to about 40 and the number of fins is from about 40 to about 80 per inch.  
   
   
       21 . The panel of  claim 19  wherein the panel comprises an aluminum alloy, a stainless steel alloy, a copper alloy, a titanium alloy, an iridium alloy, a rhodium alloy, graphite, a carbon-carbon fiber matrix composite, a carbon-silicon composite, an aluminum-silicon carbide composite, boron carbide, titanium carbide or titanium nitride.  
   
   
       22 . The panel of  claim 19  wherein the panel comprises an aluminum alloy.  
   
   
       23 . The panel of  claim 19  wherein the length of the microchannels is from about 1 inch to about 4.5 inches.  
   
   
       24 . The panel of  claim 19  wherein the number of fins on the top side of the panel is different from the number of fins on the bottom side of the panel.  
   
   
       25 . A panel for a microchannel heat exchanger core comprising: 
 a plurality of microchannels, the microchannels having a defined depth and a defined width and an aspect ratio of depth to width of at least from about 10 to about 40 and wherein the microchannels have a depth of from about 0.125 inches to about 0.50 inches and a width of from about 0.009 inches to about 0.0165 inches; and    a plurality of fins, the fins separating the microchannels by providing walls for the microchannels, wherein there are from about 40 to about 80 fins per inch of the panel and wherein the fins have a thickness of from  10  about 0.0015 inches to about 0.009 inches.    
   
   
       26 . The panel of  claim 25  wherein the microchannels and fins are on a top side of the panel.  
   
   
       27 . The panel of  claim 25  wherein the microchannels and fins are on both the top side and a bottom side of the panel.  
   
   
       28 . The panel of  claim 27  wherein the number of fins on the top side is the same as the number of fins on the bottom side.  
   
   
       29 . The panel of  claim 27  wherein the number of fins on the top side is different from the number of fins on the bottom side.  
   
   
       30 . The panel of  claim 27  wherein the aspect ratio of the microchannels on the top side is the same as the aspect ratio of the microchannels on the bottom side.  
   
   
       31 . The panel of  claim 27  wherein the aspect ratio of the microchannels on the top side is different from the aspect ratio of the microchannels on the bottom side.  
   
   
       32 . The panel of  claim 27  wherein the relative orientation of microchannels on the top side is at an angle of about 0 to about 90 degrees with respect to the orientation of the microchannels on the bottom side.  
   
   
       33 . The panel of  claim 25  wherein there are from about 50 to about 80 fins per inch of the panel, and the aspect ratio is from about 10 to about 20.  
   
   
       34 . The panel of  claim 25  wherein there are from about 40 to about 60 fins per inch of the panel, and the aspect ratio is from about 15 to about 30.  
   
   
       35 . A microchannel heat exchanger core comprising at least one panel, the panel comprising: 
 a plurality of microchannels, the microchannels having a defined depth and a defined width and an aspect ratio of depth to width of at least 10; and    a plurality of fins, the fins separating the microchannels by providing walls for the microchannels and wherein there are greater than about 36 fins per inch of the panel.    
   
   
       36 . The microchannel heat exchanger core of  claim 35  wherein there are from about 40 to about 80 fins per inch and wherein the aspect ratio is from about 10 to about 40.  
   
   
       37 . The microchannel heat exchanger core of  claim 35  wherein the at least one panel comprises a plurality of panels.  
   
   
       38 . The microchannel heat exchanger core of  claim 37  wherein the plurality of panels are arranged one on top of the other.  
   
   
       39 . The microchannel heat exchanger core of  claim 38  further comprising at least one spacer sheet disposed between at least two of the panels.  
   
   
       40 . The microchannel heat exchanger core of  claim 38  wherein the plurality of panels are joined by brazing, welding or gasketing.  
   
   
       41 . The microchannel heat exchanger core of  claim 38  wherein the plurality of panels are arranged alternately wherein the microchannels of one panel are substantially perpendicular to the microchannels of a next panel.  
   
   
       42 . A method of machining a panel, comprising the steps of: 
 applying a voltage to at least one electrode;    moving the electrode downward into one side of the panel to a desired depth, wherein a microchannel is formed in the panel;    discontinuing application of the voltage to the electrode; and    thereafter, moving the electrode upward out of the panel.    
   
   
       43 . The method of  claim 42 , wherein the panel comprises a component of a heat exchanger.  
   
   
       44 . The method of  claim 42 , wherein the microchannel has an aspect ratio of depth to width of at least about 10.  
   
   
       45 . The method of  claim 42 , wherein the step of moving the electrode downward comprises electrical discharge machining a plurality of fins and a plurality of microchannels in the panel.  
   
   
       46 . The method of  claim 45  wherein the plurality of microchannels are machined sequentially.  
   
   
       47 . The method of  claim 42  wherein the electrode is a wire having a diameter from about 0.001 inches to about 0.012 inches.  
   
   
       48 . The method of  claim 42  wherein the electrode is a rod.  
   
   
       49 . The method of  claim 48  wherein the rod has a round, elliptical, square, rectangular or triangular cross-section.  
   
   
       50 . The method of  claim 48  wherein the rod has a round cross-section with a diameter of from about 0.008 inches to about 0.010 inches.  
   
   
       51 . The method of  claim 42  wherein the at least one electrode comprises an array of electrodes.  
   
   
       52 . The method of  claim 42  further comprising the step of shaping the microchannel by etching or laser ablation.  
   
   
       53 . The method of  claim 52  wherein the etching is chemical etching or electrochemical etching.  
   
   
       54 . The method of  claim 42  wherein from about 40 to about 80 fins per inch are machined into the panel.  
   
   
       55 . The method of  claim 42  wherein the electrical discharge machining is performed on two opposite sides of the panel.  
   
   
       56 . The method of  claim 42  wherein the panel comprises an aluminum alloy, a titanium alloy, an iridium alloy, a rhodium alloy, an aluminum-silicon carbide composite, titanium carbide or titanium nitride.  
   
   
       57 . A method of machining a panel for a microchannel heat exchanger comprising: 
 applying a voltage to at least one electrode;    performing electrical discharge machining of a plurality of microchannels and fins on the panel using the electrode, wherein the fins separate the microchannels by providing walls and wherein the microchannels have an aspect ratio of depth to width of at least about 10; and    etching the microchannels.    
   
   
       58 . The method of  claim 57  wherein the etching is chemical etching.  
   
   
       59 . The method of  claim 57  wherein a dilute acid or base is used for the etching.  
   
   
       60 . The method of  claim 57  wherein a dilute solution of potassium hydroxide having a concentration of about  5 % to about  20 % by weight is used for the etching.  
   
   
       61 . The method of  claim 57  wherein the electrical discharge machining comprises moving the electrode downward into the panel to a desired depth for the microchannel, and thereafter moving the electrode upward out of the panel, and wherein the voltage is applied to the electrode only as the  5  electrode is moved downward into the panel.  
   
   
       62 . The method of  claim 57  wherein the electrical discharge machining comprises powering the electrode throughout the machining method.  
   
   
       63 . A method of making a microchannel heat exchanger core comprising the steps of: 
 applying a voltage to at least one electrode;    performing electrical discharge machining of a plurality of  5  microchannels and fins on at least two panels using the electrode to provide machined panels, wherein the fins separate the microchannels by providing walls for the microchannels and wherein the microchannels have an aspect ratio of depth to width of at least about 10;    etching the microchannels of the machined panels;    arranging the machined panels one on top of the other; and    joining the machined panels together by brazing, welding or gasketing.    
   
   
       64 . The method of  claim 63  further comprising the step of placing a parting sheet between the machined panels before they are joined.  
   
   
       65 . The method of  claim 63  wherein the panels comprise an aluminum alloy, a titanium alloy, an iridium alloy, a rhodium alloy, titanium carbide or titanium nitride.  
   
   
       66 . A method of machining a panel comprising the steps of: 
 applying a first voltage to at least one electrode;    moving the electrode downward into one side of the panel to a desired depth, wherein a microchannel is formed in the panel;    changing the applied voltage to a second voltage;    moving the electrode sideways by a predetermined amount;    changing the applied voltage to a third voltage; and    moving the electrode upward out of the panel.