Micro-tube metal matrix heat exchanger and method of manufacture

Abstract

A heat exchanger is characterized by having two or more fluid flow circuits, each formed by multiple small cross-section “micro-tubes” contained within a surrounding metal structure, or “metal matrix.” Its function is to efficiently transfer heat from one fluid to another in a highly compact assembly. Most any metal or metal alloy can be considered for the micro-tubes. The micro-tubes, while typically arranged in alternating layers of alternating flow circuits, may be organized in any number of arrangements including co-linear and at cross angles to provide for co-flow, counter flow and cross flow. The metal matrix, is provided in one embodiment by a metal or metal alloy powder consolidated in a hot isostatic pressing (HIP) process. This process also joins the tubes together and to the matrix itself, producing a monolithic structure.

What is claimed is: 
     
         1 : A method for forming a heat exchanger for transferring heat between two separate fluids, the method including the steps of:
 arranging a plurality of first tubes comprising a first set of tubes to be formed of a first material adjacent to a plurality of second tubes comprising a second set of tubes to be formed of a second material, and with interstices between the first tubes and the second tubes;   at least partially filling the interstices of said arranging step with a metal powder formed of a third material, the third material different from at least the first material; and   raising the combination of the first tubes, the second tubes, and the metal powder up to a sintering temperature for the third material, to sinter the metal powder into a metal matrix between the first tubes and the second tubes.   
     
     
         2 : The method of  claim 1  wherein said heating step occurs under pressure greater than atmospheric pressure. 
     
     
         3 : The method of  claim 2  wherein said heating step occurs within a hot isostatic press. 
     
     
         4 : The method of  claim 3  wherein the first material and the second material of said arranging step are different from each other. 
     
     
         5 : The method of  claim 3  wherein the first material and the second material of said arranging step are similar. 
     
     
         6 : The method of  claim 1  wherein said arranging step includes the first material forming the first set of tubes having a melting point higher than the temperature of said raising step. 
     
     
         7 : The method of  claim 1  wherein said arranging step includes said first set of tubes having a circular cross-section. 
     
     
         8 : The method of  claim 1  wherein said arranging step includes said first set of tubes and said second set of tubes being arranged with elongate central axes thereof parallel to each other for at least a portion of a length of said first set of tubes and said second set of tubes. 
     
     
         9 : The method of  claim 8  wherein said arranging step includes said first set of tubes and said second set of tubes having elongate central axes thereof which are parallel to each other over a majority of a length of said first set of tubes and said second set of tubes. 
     
     
         10 : The method of  claim 8  wherein said arranging step includes said first set of tubes and said second set of tubes being arranged in planar layers which alternate with each other. 
     
     
         11 : The method of  claim 10  wherein said arranging step includes said first set of tubes and said second set of tubes being arranged with each tube of each said set of tubes spaced vertically or horizontally from adjacent tubes. 
     
     
         12 : The method of  claim 10  wherein said arranging step includes said first set of tubes and said second set of tubes being arranged with each tube of each said set of tubes spaced in a hexagonal close packed arrangement. 
     
     
         13 : The method of  claim 1  wherein said first set of tubes and said second set of tubes of said arranging step are arranged in a counter-flow relationship within the heat exchanger. 
     
     
         14 : The method of  claim 1  wherein said first set of tubes and said second set of tubes of said arranging step are arranged in a co-flow relationship within the heat exchanger. 
     
     
         15 : The method of  claim 1  wherein said first set of tubes and said second set of tubes of said arranging step are arranged in a cross-flow relationship within the heat exchanger. 
     
     
         16 : The method of  claim 1  wherein at least said first set of tubes of said arranging step include protuberances on an inside surface of said first set of tubes, said protuberances enhancing a surface area of said inside surface of said first set of tubes relative to a plain cylindrical inside surface. 
     
     
         17 : The method of  claim 1  wherein said arranging step includes the heat exchanger having two pairs of opposing faces including two opposing side faces and two opposing end faces, said opposing side faces supporting opposing ends of each of said first set of tubes, said opposing end faces supporting opposing ends of each of said second set of tubes, said first set of tubes having central portions thereof extending parallel with central portions of said second set of tubes. 
     
     
         18 : The method of  claim 17  wherein said first set of tubes of said arranging step includes said central portions thereof extending in a direction parallel to a plane of said lateral faces, said first set of tubes including inlet portions thereof and outlet portions thereof between said central portions and said lateral faces which are oriented perpendicular to a plane of said lateral faces. 
     
     
         19 : The method of  claim 17  wherein said first set of tubes of said arranging step have at least portions thereof each including a similar series of regularly spaced bends between ends of each of said first set of tubes. 
     
     
         20 : The method of  claim 19  wherein said second set of tubes of said arranging step have at least portions of at least some tubes thereof each including a similar series of regularly spaced bends between ends of each of said second set of tubes, said first set of tubes and said second set of tubes having a similar form to maintain a parallel relationship along at least portions thereof which include said series of regularly spaced bends therein. 
     
     
         21 : The method of  claim 19  wherein said regularly spaced bends of said first set of tubes of said arranging step are spaced from each other by linear sections of said first set of tubes, such that said first set of tubes have a zig-zag form. 
     
     
         22 : The method of  claim 17  wherein said central portions of said first set of tubes of said arranging step and said central portions of said second set of tubes of said arranging step exhibit a close packed hexagonal relationship with at least one of said second set of tubes in physical contact with at least two of said first set of tubes.