Multiple concentric cylindrical co-coiled heat exchanger

Abstract

A compact shell and coil heat exchanger is disclosed that accommodates widely differing volumetric flowrates between the two fluids undergoing heat exchange. Multiple co-coiled helical coils of tubing are concentrically arranged, and coil spacers are provided which maintain the tubes in overall staggered alignment, as illustrated in FIG. 1. Uniformly high transfer coefficients are maintained throughout the bundle of coils via means for ensuring that the tube-side flow through the tubes of each coil, and the shell-side flow across each coil, are kept proportional to the tube surface area of each coil.

1 ) A heat exchanger comprised of
 a) Multiple concentric helical coils of tubing, wherein each coil is coiled in the same direction;   b) A pressure vessel containing said coils;   c) At least one spacer for each coil, which maintains approximately equal tube gaps within the successive loops of the coil, and approximately equal coil-to-coil gaps between it and an adjoining coil;   d) Connections between adjoining spacers which maintain the spacers in alignment such that the tubes of adjoining coils are in staggered alignment; and   e) A tube header for each end of the collection of coils, which connects the tubes at that end to an external fluid conduit.   
   
   
       2 ) The apparatus according to claim additionally comprising a core blocker that prevents shell-side fluid from bypassing the bundle of multiple coils. 
   
   
       3 ) The apparatus according to  claim 2  wherein said tubes are are circular cross section tubes with diameters in the approximate range of 3/16 0  to ¾ inches. 
   
   
       4 ) The apparatus according to  claim 2  wherein said coil-to-coil gap is in the approximate range of 0.1 D to 0.8 D, and the tube gap is in the approximate range of 0.3 D to 1 D, where D is the diameter of the tubing. 
   
   
       5 ) The apparatus according to  claim 4  wherein said tubes include at least one of grooving and corrugations. 
   
   
       6 ) The apparatus according to  claim 3  adapted to be a refrigerant heat exchanger in an absorption refrigeration cycle, and including a bottom entry in the shell for a cold refrigerant vapor, and a warm refrigerant liquid connection to the top tube header, whereby refrigerant vapor flows axially upward through the shell, and refrigerant liquid flows countercurrently downward through the tube bundle. 
   
   
       7 ) The apparatus according to  claim 3  adapted to be a heat recovery vapor generator in an absorption cycle for producing at least one of refrigeration, heat pumping, and power, and including a bottom entry in the shell for a hot exhaust gas, a preheated absorbent liquid solution connection to the top tube header, and an outlet for partially desorbed solution from the bottom tube header, whereby exhaust gas flows axially upward through the shell, and desorbing liquid flows countercurrently downward through the tube bundle. 
   
   
       8 ) The apparatus according to  claim 3  adapted to be an evaporator for chilling a gas such as air in an absorption refrigeration cycle, and including a top entry in the shell for the gas to be chilled, and a pre-cooled refrigerant liquid connection to the bottom tube header, whereby the gas being chilled flows axially downward through the shell, and evaporating refrigerant liquid flows countercurrently upward through the tube bundle. 
   
   
       9 ) The apparatus according to  claim 3 , adapted to be a component of a closed ammonia-water absorption cycle, with ammonia-containing liquid supplied to one of the tube headers, and low pressure vapor supplied to the shell at the other end of the tube bundle. 
   
   
       10 ) A heat exchanger comprising:
 a) A bundle of multiple concentric coils of helically coiled tubing, wherein at least some of the coils have more than one tubing start, and wherein all the coils are wound in the same direction   b) A pressure containment for said bundle of coils, which admits a first fluid to one end of said bundle,   c) A tube header for each end of said bundle, which admits a second fluid into and out of said coils.   
   
   
       11 ) The apparatus according to  claim 10  additionally comprised of a central core blocker that prevents said first fluid from bypassing said bundle. 
   
   
       12 ) The apparatus according to  claim 11  additionally comprised of spacers for each coil which maintain approximately equal tube gaps and approximately equal coil gaps, and connectors for said spacers which maintain most of the tubes of adjacent coils in staggered alignment. 
   
   
       13 ) The apparatus according to  claim 12  additionally comprising a second tube header at each end of said bundle, which connects a third fluid to a subset of said coils. 
   
   
       14 ) The apparatus according to  claim 12  wherein the diameter of said tubes is in the range of 3/16 to ⅝ inches, and wherein said tube gaps are in the range of 0.1D to 1D, and the coil gaps are in the range of D/20 to ¾ D. 
   
   
       15 ) The apparatus according to  claim 12  additionally comprised of spacer strips on said blocker which maintain a gap between the blocker and the innermost coil of approximately one half the coil-to-coil gap, plus spacers that maintain the gap between the outermost coil and the containment shell at approximately one half the coil-to-coil gap. 
   
   
       16 ) The apparatus according to  claim 12  wherein the tube flow through and shell flow around the tubes of each coil are maintained approximately proportional to the tube surface area of the coil by at least one of:
 a) Placing flow-reducing inserts in the shorter tubes;   b) Using smaller diameter tubes in the smaller diameter coils; and   c) Increasing the number of tube starts in the larger coils proportional to the coil diameter.   
   
   
       17 ) A shell and coil heat exchanger comprised of multiple co-coiled concentric coils of tubing with multiple tube starts in each coil, adapted for use in an ammonia-water absorption cycle apparatus as at least one of the refrigerant heat exchanger, the heat recovery vapor generator, and the evaporator. 
   
   
       18 ) The apparatus according to  claim 17  additionally comprised of at least one spacer for each coil that maintains the tubes of that coil in staggered alignment with the tubes of an adjacent coil. 
   
   
       19 ) A shell and coil heat exchanger with multiple co-coiled concentric coils of tubing characterized in that each coil of tubing is adjusted to have tube-side flow through the tubing and shell-side flow around the tubing which is proportional to the tube surface area of that coil, the same proportionality holding for all the coils, by at least one of:
 a) Placing flow-reducing inserts in the shorter tubes;   b) Using smaller diameter tubes in the smaller diameter coils; and   c) Increasing the number of starts in the larger coils proportional to the coil diameter.   
   
   
       20 ) The apparatus according to  claim 19  additionally comprised of spacers for each coil which are interconnected so as to maintain overall staggered alignment of the tubes.