Heat Exchange Device with Variable Tube Material

Abstract

A heat exchange device utilizing variable tube materials is provided. In one particular embodiment, the heat exchange device is an evaporative condenser with a multi-pass tube bundle. The first few tube passes (typically 1-3 tube passes) of the tube bundle, which in operation are typically exposed to superheated refrigerant gas, are comprised of a material that is highly resistant to corrosion (e.g., 316/316L stainless steel). The remaining tube passes, which in operation are typically exposed to a lower-temperature refrigerant (i.e., saturated two-phase or subcooled liquid), are comprised of one or more lower-cost, less corrosion-resistant material (e.g., 304/304L stainless steel).

We claim: 
     
         1 . A heat exchange device comprising:
 a multi-pass tube bundle with at least a first pass and a subsequent pass;   the first pass comprising a first material and the subsequent pass comprising a second material; and,   the first material being different from the second material.   
     
     
         2 . The heat exchange device of  claim 1 , wherein at least one tube defines both the first pass and the subsequent pass. 
     
     
         3 . The heat exchange device of  claim 2 , wherein the at least one tube is defined by a plurality of connected tube sections. 
     
     
         4 . The heat exchange device of  claim 3 , wherein the tube sections are selected from the group including straight tubes, canes, return bends, and hairpins. 
     
     
         5 . The heat exchange device of  claim 1 , wherein the first material has a greater resistance to corrosion than the second material. 
     
     
         6 . The heat exchange device of  claim 5 , wherein the multi-pass tube bundle defines an evaporative condenser adapted to discharge heat to an external, recirculating, evaporative fluid. 
     
     
         7 . The heat exchange device of  claim 1 , wherein the first material is 316/316L stainless steel and the second material is 304/304L stainless steel. 
     
     
         8 . The heat exchange device of  claim 1 , wherein the first material is disposed at an outer surface of the first pass of the tube and the second material is disposed at an outer surface of the subsequent pass of the tube. 
     
     
         9 . The heat exchange device of  claim 1 , wherein the first material has a higher concentration of nickel, molybdenum, or both nickel and molybdenum than the second material. 
     
     
         10 . The heat exchange device of  claim 1 , wherein the first pass of the tube is the only pass of the tube comprised of the first material. 
     
     
         11 . The heat exchange device of  claim 1 , wherein the tube has a second pass comprised of the first material. 
     
     
         12 . The heat exchange device of  claim 1 , wherein the first pass of the tube is connected to an inlet of the multi-pass tube bundle and the subsequent pass of the tube is connected to an outlet of the multi-pass tube bundle. 
     
     
         13 . The heat exchange device of  claim 1 , wherein a first tube section defines the first pass and a second tube section defines the subsequent pass. 
     
     
         14 . The heat exchange device of  claim 12 , wherein the first tube section and the second tube section are connected in series. 
     
     
         15 . The heat exchange device of  claim 1  further comprising a first group of tube passes and a subsequent group of passes, wherein: the first group of tube passes includes the first pass and the subsequent group of passes includes the subsequent pass; and, each tube pass in the first group of tube passes comprises the first material and each tube pass in the second group of tube passes comprises the second material. 
     
     
         16 . The heat exchange device of  claim 14 , where a number of tube passes in the first group of tube passes is less than a number of tube passes in the second group of tube passes. 
     
     
         17 . The heat exchange device of  claim 15 , wherein the first group of tube passes are the only group of tube passes comprised of the first material. 
     
     
         18 . The heat exchange device of  claim 15 , wherein the second group of tube passes comprises all remaining tube passes of the multi-pass tube bundle.