METHOD FOR MAKING BRAZED ALUMINUM HEAT EXCHANGER AND APPARATUS

• US 20110139417A1
• Filed: 12/16/2009
• Published: 06/16/2011
• Est. Priority Date: 12/16/2009
• Status: Abandoned Application

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: UOP Llc (Honeywell International Inc.)
• Inventors: Godry, Thomas J., O'Neill, Patrick S.
• Application Number:
  US12/639,980
• Publication Number:
  US 20110139417A1
• Time in Patent Office: Days
• US Class Current: 165/166
• CPC Class Codes: F25J 2210/40 Air or oxygen enriched air, i.e. generally less than 30mol% of O2
• CPC Class Codes: F25J 2250/02 Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
• CPC Class Codes: F25J 2290/20 Particular dimensions; Small scale or microdevices
• CPC Class Codes: F25J 2290/42 Modularity, pre-fabrication of modules, assembling and erection, horizontal layout, i.e. plot plan, and vertical arrangement of parts of the cryogenic unit, e.g. of the cold box
• CPC Class Codes: F25J 2290/44 Particular materials used, e.g. copper, steel or alloys thereof or surface treatments used, e.g. enhanced surface
• CPC Class Codes: F25J 3/04412 in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
• CPC Class Codes: F25J 5/002 for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger
• CPC Class Codes: F25J 5/005 in a reboiler-condenser, e.g. within a column
• CPC Class Codes: F28D 2021/0033 for cryogenic applications
• CPC Class Codes: F28D 9/0068 with means for changing flow direction of one heat exchange medium, e.g. using deflecting zones
• CPC Class Codes: F28F 13/187 especially adapted for evaporator surfaces or condenser surfaces, e.g. with nucleation sites
• CPC Class Codes: F28F 21/084 from aluminium or aluminium alloys

Abstract

Disclosed is a heat exchanger comprising a boiling passage and cooling passage defined by opposite sides of metal walls. The heat exchanger is made with high strength alloys of aluminum that have improved creep resistance that maintain tensile strength and yield strength after use in this invention. Layers of brazing material between the metal walls and a spacer member bond components of the heat exchanger together. An enhanced boiling layer (EBL) comprising metal particles bonded to each other and to a boiling side of the metal wall provides nucleate boiling pores to improve heat transfer. The EBL has a melting temperature that is higher than the melting temperature of the brazing material. Also disclosed is a process for assembling the heat exchanger.

Claims

1. A heat exchanger comprising:

a plurality of metal walls, each metal wall comprising two sides, a boiling side with a porous, enhanced boiling layer comprising brazed, thermally conductive particles comprising a highly proportioned aluminum alloy powder mixed with a eutectic alloy of aluminum and silicon integrally bonded together and metallurgically bonded to the boiling side and a cooling side, said boiling side of said plurality of metal walls defining a boiling passage and said cooling side of said plurality of metal walls defining a cooling passage and each of said plurality of metal walls further including a bonding surface and wherein each of said plurality of metal walls comprise an alloy of aluminum having mechanical properties consistent with a hardness value of at least 35 Rockwell E;

a spacer member for spacing metal walls from each other;

a layer of metal between said bonding surfaces of said metal walls and said spacer member in said heat exchanger, said layer of metal having a melting temperature that is less than a melting temperature of said enhanced boiling layer;

a boiling inlet for delivering liquid to said boiling passage;

a cooling inlet for delivering fluid to said cooling passage;

a boiling outlet for recovering vapor from said boiling passage; and

a cooling outlet for recovering fluid from said cooling passage.

2. The heat exchanger of claim 1, wherein said enhanced boiling layer includes between about 0.5 and about 1.5 wt-% silicon.

3. The heat exchanger of claim 1, wherein the highly proportioned aluminum alloy comprises 92 wt-% of the enhanced boiling layer and the eutectic alloy comprises 8 wt-% of the enhanced boiling layer.

4. The heat exchanger of claim 1, wherein said boiling side has a boiling heat transfer coefficient of above 10,000 BTU/hr/ft2°

F.

5. The heat exchanger of claim 1, wherein the eutectic alloy is 12 wt-% silicon and 88 wt-% aluminum.

6. A heat exchanger comprising:

a plurality of metal walls comprising an aluminum alloy having mechanical properties consistent with a hardness value of at least 35 Rockwell E, each metal wall comprising two sides, a boiling side with an enhanced boiling layer comprising thermally conductive particles comprising a highly proportioned aluminum alloy powder mixed with a eutectic alloy of aluminum and silicon integrally bonded together and metallurgically bonded to the boiling side and a cooling side, said thermally conductive particles comprising brazed alloy of a first metal and a second metal, said second metal alloying with said first metal to provide an alloy with a melting temperature that is lower than the melting temperature of said first metal, said boiling sides of said plurality of metal walls defining boiling passages and said cooling sides of said plurality of metal walls defining cooling passages and each of said plurality of metal walls further including a bonding surface;

a plurality of spacer bars each between pairs of said metal walls, each of said spacer bars having a bonding surface;

a layer of metal between each of said bonding surfaces of said metal walls and a bonding surface of an adjacent one of said plurality of spacer bars, said layer of metal comprising an alloy including said first metal and an elevated brazing temperature of said layer of metal is less than a melting temperature of said enhanced boiling layer;

a boiling inlet for delivering liquid to said boiling passage;

a cooling inlet for delivering fluid to said cooling passages;

a boiling outlet for recovering vapor from said boiling passages; and

a cooling outlet for recovering fluid from said cooling passages.

7. The heat exchanger of claim 6, wherein said layer of metal comprises an additional metal with a greater concentration of said additional metal than a concentration of said second metal in said enhanced boiling layer.

8. The heat exchanger of claim 6, wherein the second metal and the additional metal are silicon.

9. The heat exchanger of claim 6, wherein the enhanced boiling layer includes between 0.5 and 1.5 wt-% silicon.

10. The heat exchanger of claim 6, wherein the highly proportioned aluminum alloy comprises 92 wt-% of the enhanced boiling layer and the eutectic alloy comprises 8 wt-% of the enhanced boiling layer.

11. The heat exchanger of claim 6, wherein said enhanced boiling layer is porous and said thermally conductive particles are metallurgically bonded to the boiling side.

12. A heat exchanger comprising:

a plurality of metal walls comprising aluminum having mechanical properties consistent with a hardness value of at least 35 Rockwell E, each metal wall comprising two sides, a cooling side and a boiling side with an enhanced boiling layer comprising thermally conductive particles, said thermally conductive particles including a highly proportioned aluminum alloy powder mixed with a eutectic alloy of aluminum and silicon, said thermally conductive particles being integrally bonded together and metallurgically bonded to the boiling side, said boiling side of said plurality of metal walls defining a boiling passage and said cooling side of said plurality of metal walls defining a cooling passage and each of said plurality of metal walls further including a bonding surface;

a spacer member for spacing metal walls from each other;

a layer of metal between said bonding surfaces of said metal walls and said spacer member in said heat exchanger, said layer of metal having a melting temperature that is less than a melting temperature of said enhanced boiling layer;

a boiling inlet for delivering liquid to said boiling passage;

a cooling inlet for delivering fluid to said cooling passage;

a boiling outlet for recovering vapor from said boiling passage; and

a cooling outlet for recovering fluid from said cooling passage.

13. The heat exchanger of claim 12, wherein said boiling side has a boiling heat transfer coefficient of above 10,000 BTU/hr/ft2°

F.