Shell-Side Fluid Distribution in Coil Wound Heat Exchangers

Abstract

Embodiments of the present invention provide improved shell-side fluid distribution in coil wound heat exchanger system and methods therefor. The fluid distribution system includes a system having a plurality of distribution arms having inner and outer cavities and valves to control the flow of shell-side fluid to control radial temperature profiles in a coil wound heat exchanger having multiple bundles of tubes.

1 . A system for indirect heat exchange between a feed gas and a refrigerant, the system comprising:
 a feed gas conduit in flow communication with a supply of the feed gas;   a shell defining a shell space;   at least one tube bundle located in the shell space, each of the at least one tube bundle comprising a first set of tubes in fluid flow communication with the feed gas conduit, a central conduit, and a distributor assembly, the first set of tubes having a cold end and a warm end and being helically wrapped around a central mandrel, the distributor assembly having a plurality of arms located above the first set of tubes, each of the plurality of arms having a first cavity including a plurality of apertures, the first cavity being in direct fluid flow communication with the central conduit, the central conduit being in fluid flow communication with a supply of the refrigerant;   wherein at least one of the plurality of arms further comprises a second cavity including a plurality of apertures and a separating wall located between the first and second cavities to inhibit fluid flow communication between the first and second cavities, the second cavity being in fluid flow communication with the central conduit only through a bypass conduit and a valve, the second cavity being located at a greater radial distance from the central mandrel than the first cavity.   
     
     
         2 . The system of  claim 1 , wherein the at least one tube bundle further comprises a second set of tubes having a cold end and a warm end, the second set of tubes being located below the plurality of arms, helically wrapped around the central mandrel, and in fluid flow communication with a first refrigerant conduit, the second set of tubes comprising the supply of the refrigerant to the central conduit. 
     
     
         3 . The system of  claim 1 , wherein the central conduit comprises the central mandrel and a plate located within the central mandrel comprises a lower end of the central conduit. 
     
     
         4 . The system of  claim 1 , wherein the first cavity has a first flow per unit bundle area and the second cavity has a second flow per unit bundle area and the second flow per unit bundle area is greater than the first flow per unit bundle area. 
     
     
         5 . The system of  claim 1 , wherein the distributor assembly is operationally configured to provide at least 10% greater flow per unit bundle area of the refrigerant through the second cavity than through the first cavity when the valve is in a fully open position. 
     
     
         6 . The system of  claim 2 , further comprising a first expansion conduit having an expansion valve, the first expansion conduit being in fluid flow communication with the cold end of the second set of tubes of a first tube bundle of the at least one tube bundle, and being in fluid flow communication with the central conduit of the first tube bundle. 
     
     
         7 . The system of  claim 2 , wherein a first tube bundle of the at least one tube bundle further includes a third set of tubes having a cold end and a warm end, the third set of tubes being in fluid flow communication with a second refrigerant conduit. 
     
     
         8 . The system of  claim 7 , further comprising a second expansion conduit having an expansion valve, the second expansion conduit being in fluid flow communication with the cold end of the third set of tubes of a second tube bundle of the at least one tube bundle, and being in fluid flow communication with the central conduit of the second tube bundle. 
     
     
         9 . The system of  claim 7 , wherein the first refrigerant conduit is operationally configured to supply a vapor stream of the refrigerant to the warm end of the second set of tubes, the second refrigerant conduit is operationally configured to supply a liquid stream of the refrigerant to the warm end of the third set of tubes. 
     
     
         10 . The system of  claim 1 , wherein the at least one tube bundle includes a hot tube bundle and a cold tube bundle, the hot tube bundle being located below the cold bundle. 
     
     
         11 . The system of  claim 1 , further comprising a refrigerant compression circuit operationally configured to withdraw the refrigerant from the shell space at a location below a hot tube bundle of the at least one tube bundle, compress and cool the refrigerant, and return the refrigerant to the warm end of the hot tube bundle, wherein the hot tube bundle is located below any other bundles of the at least one tube bundle. 
     
     
         12 . The system of  claim 11 , wherein the refrigerant compression circuit comprises a warm end conduit, a compressor assembly, and a high-pressure conduit, the compressor assembly comprising having a low-pressure end and a high-pressure end, at least one multi-stage compressor and at least one heat exchanger, the warm end conduit being in fluid flow communication with the shell space at a location below the hot tube bundle and being in fluid flow communication with the low-pressure end of the compressor assembly, the high-pressure conduit being in fluid flow communication with the high-pressure end of the compressor assembly and the warm end of the hot tube bundle. 
     
     
         13 . The system of  claim 1 , wherein the feed gas is natural gas. 
     
     
         14 . A method of cooling a feed gas stream flowing through at least one tube bundle located within a shell space of a heat exchanger against a refrigerant, each of the at least one tube bundle comprising at least one set of tubes helically wrapped around a central mandrel, the method comprising:
 (a) irrigating at each of the at least one tube bundle with the refrigerant by enabling the refrigerant to flow through a distributor assembly having a plurality of arms located above each of the at least one tube bundle;   (b) allowing the refrigerant to flow directly from a central conduit to a first cavity of each of the plurality of arms, the first cavity including a plurality of apertures;   (c) controlling flow of the refrigerant to a second cavity of at least one of the plurality of arms of the distributor assembly by operating a valve located on or upstream from a bypass conduit that provides fluid flow communication between the central conduit and the second cavity and providing a separating wall located between the first and second cavities to inhibit fluid flow communication between the first and second cavities, the second cavity including a plurality of apertures and being located at a greater radial distance from the central mandrel than the first cavity.   
     
     
         15 . The method of  claim 14 , further comprising:
 (d) selecting a location of each of the separating walls as a function of the first and second areas of the at least one tube bundle, the first area comprising a portion of the tube bundle extending from the central mandrel to the separating wall and the second area comprising a second portion of the tube bundle extending from the separating wall to an outer end of the second cavity.   
     
     
         16 . The method of  claim 15 , wherein step (d) comprises selecting the location of each of the separating walls so that the first and second areas are substantially equal. 
     
     
         17 . The method of  claim 14 , further comprising:
 (e) measuring a plurality of temperatures of a first tube bundle of the at least one tube bundle, each of the plurality temperatures being taken at different radial distance from the central mandrel;   (f) setting the position of each valve located on each bypass conduit for the distributor assembly located above the first tube bundle as a function of the plurality of temperatures.   
     
     
         18 . The method of  claim 14 , further comprising:
 (g) withdrawing the refrigerant from a warm end of the shell space;   (h) compressing and cooling the withdrawn refrigerant; and   (i) reintroducing the compressed and cooled refrigerant into a warm end of one of the at least one tube bundle.   
     
     
         19 . The method of  claim 14 , wherein step (a) further comprises irrigating a first tube bundle of the at least one tube bundle with a first refrigerant stream withdrawn from a cold end of the first tube bundle and irrigating a second tube bundle of the at least one tube bundle with at least a portion of the first refrigerant stream. 
     
     
         20 . The method of  claim 19 , wherein step (a) further comprises irrigating the second tube with a second refrigerant stream withdrawn from a cold end of the second tube bundle.