Economizer

Abstract

Disclosed is an economizer including a plurality of coil stacks. Each coil stack includes a tube coiled such that adjacent layers of the tube contact one another in a radial direction. Further, the coil stacks are axially spaced from one another to allow exhaust to flow between adjacent coil stacks.

What is claimed is: 
     
         1 . An economizer comprising:
 a plurality of coil stacks, each coil stack including a tube coiled such that adjacent layers of the tube contact one another in a radial direction, the coil stacks axially spaced from one another to allow exhaust to flow between adjacent coil stacks.   
     
     
         2 . The economizer according to  claim 1 , wherein the coils stacks are axially spaced from one another such that an axial gap is provided between adjacent coil stacks, the axial gap related to the diameter of the tubes by a ratio within the range of 0.25:1 and 0.5:1. 
     
     
         3 . The economizer according to  claim 2 , wherein the axial gap is within the range of about 3/16 inches (0.48 cm) and ⅜ inches (0.95 cm). 
     
     
         4 . The economizer according to  claim 3 , wherein there are between  30  and  36  coil stacks. 
     
     
         5 . The economizer according to  claim 4 , wherein the tube diameter is about 0.75 inches (1.9 cm). 
     
     
         6 . The economizer according to  claim 1 , wherein the economizer does not include any heat-transfer fins. 
     
     
         7 . A heat recovery system comprising:
 a boiler configured to generate a flow of exhaust; and   an economizer including a plurality of coil stacks, each coil stack including a tube coiled such that adjacent layers of the tube contact one another in a radial direction, the coil stacks axially spaced from one another to allow the exhaust from the boiler to flow between adjacent coil stacks.   
     
     
         8 . The system as recited in  claim 7 , wherein each coil stack is disposed about an axis, the economizer arranged relative to the boiler such that the exhaust enters the economizer flowing in a direction parallel to the axis. 
     
     
         9 . The system as recited in  claim 8 , wherein the exhaust flows radially, in a direction perpendicular to the axis, between adjacent coil stacks. 
     
     
         10 . The system as recited in  claim 7 , wherein a flow of a working fluid is provided to the economizer, the working fluid heated by the exhaust from the boiler. 
     
     
         11 . The system as recited in  claim 10 , wherein the working fluid is water. 
     
     
         12 . The system as recited in  claim 10 , wherein the economizer includes an inlet manifold in communication with each of the coils stacks, the working fluid provided to the inlet manifold. 
     
     
         13 . The system as recited in  claim 7 , including a conduit configured to direct exhaust toward the economizer, the conduit including a plurality of fins configured to swirl the flow of exhaust as the exhaust enters the economizer. 
     
     
         14 . The system according to  claim 7 , wherein the axial gap is within the range of about 3/16 inches (0.48 cm) and ⅜ inches (0.95 cm). 
     
     
         15 . The system according to  claim 14 , wherein there are between  30  and  36  coil stacks. 
     
     
         16 . The system according to  claim 15 , wherein the tube diameter is about 0.75 inches (1.9 cm). 
     
     
         17 . The system according to  claim 7 , wherein the exhaust flows from the boiler to the economizer without the aid of an exhaust fan. 
     
     
         18 . A method for heating a working fluid comprising:
 providing a boiler;   providing an economizer including a plurality of coil stacks, each coil stack including a tube coiled such that adjacent layers of the tube contact one another in a radial direction, the coil stacks axially spaced from one another;   establishing a flow of a working fluid within each of the coil stacks; and   establishing a flow of exhaust from the boiler between adjacent coil stacks to heat the working fluid carried within the coil stacks.   
     
     
         19 . The method as recited in  claim 18 , wherein the working fluid is water. 
     
     
         20 . The method as recited in  claim 19 , including condensing water on the outside of the coil stacks to increase heat transfer between the exhaust and the water carried within the coil stacks.