Patent Publication Number: US-2006005955-A1

Title: Heat exchanger apparatus and methods for controlling the temperature of a high purity, re-circulating liquid

Description:
RELATED APPLICATIONS  
      This application is a continuation-in-part of U.S. patent application Ser. No. 10/889,779, filed Jul. 12, 2004 and titled HEAT EXCHANGER APPARATUS FOR A RECIRCULATION LOOP AND RELATED METHODS AND SYSTEMS, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to the field of cooling and heating fluids. More particularly, the present invention relates to cooling and heating fluids in fluid recirculation loops, such as those used in the manufacture of semiconductor wafers, which require the avoidance or at least minimization of impurities being introduced into the fluid in the recirculation loop. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Understanding that drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings. The drawings are listed below.  
       FIG. 1  is a schematic view of a method and system for heat transfer and temperature control of a process liquid wherein the heat exchanger apparatus has two gas separators adapted to separate pressurized gas into gas streams having different temperatures.  
       FIG. 2A  is a perspective view of the housing of the heat exchanger apparatus with an inlet manifold fitting and an outlet manifold fitting extending through one of the end caps.  
       FIG. 2B  is a perspective view of the same housing shown in  FIG. 2A  with complete inlet and outlet fittings.  
       FIG. 2C  is a perspective view of the heat exchanger apparatus with a partial cut-away view of the housing.  
       FIG. 3A  is an exploded perspective view of the components of the heat exchanger apparatus.  
       FIG. 3B  an enlarged perspective view of the gas separator case and an exploded perspective view of the components of the gas separator for delivery of a stream of cold gas and the gas separator for delivery of a stream of cold gas.  
       FIG. 3C  an exploded perspective view of the components shown in  FIG. 3B  from another viewing angle.  
       FIG. 3D  is an enlarged perspective view of a vortex generator.  
       FIG. 3E  is an enlarged perspective view of a stream decoupler.  
       FIG. 4A  is a perspective view of the side of the heat exchanger apparatus shown in  FIG. 2B .  
       FIG. 4B  is a cross-sectional view of the heat exchanger apparatus taken along cutting line  4 B-B in  FIG. 4A .  
       FIG. 4C  is a cross-sectional view of the heat exchanger apparatus taken along cutting line  4 C- 4 C in  FIG. 4A .  
       FIG. 5  is an exploded perspective view of the inlet fitting for the fluid which flows into the heat exchanger apparatus for heat transfer.  
       FIG. 6A  depicts the heat exchange tubes after being positioned within the passages of the body of a manifold fitting such that they extend beyond the first end of the body.  
       FIG. 6B  depicts tubes  140  have been cut off to be as close as possible to being flush with the face of the body of the manifold fitting.  
       FIG. 6C  depicts an infrared heater exposing the inlet ends of the tubes and the portion of the body of the manifold fitting under its face to fuse the tubes and the body at least under its face.  
       FIG. 6D  is a perspective view of the body of the manifold fitting and the spacing around the inlet ends of the heat transfer tubes before the inlet ends and the body are fused.  
       FIG. 6E  is a cross-sectional view of the body of the manifold fitting and the spacing around the inlet ends of the heat transfer tubes before the inlet ends and the body are fused.  
       FIG. 6F  depicts the inlet ends of heat transfer tubes before being fused to the body of the manifold fitting.  
       FIG. 6G  depicts the inlet ends of heat transfer tubes after being fused to the body of the manifold fitting.  
       FIG. 7  is a schematic view of a method and system for heat transfer and temperature control of a process liquid wherein the heat exchanger apparatus has one gas separator adapted to separate pressurized gas into gas streams having different temperatures.  
       FIG. 8  is an exploded perspective view of the components of a heat exchanger apparatus having one gas separator adapted to separate pressurized gas into gas streams having different temperatures.  
       FIG. 9A  is a perspective view of the side of the heat exchanger apparatus shown in  FIG. 7 .  
       FIG. 9B  is a cross-sectional view of the heat exchanger apparatus taken along cutting line  9 B- 9 B in  FIG. 9A .  
       FIG. 10A  is a schematic view of another method and system for heat transfer and temperature control of a process liquid wherein the heat exchanger apparatus has one gas separator adapted to separate pressurized gas into gas streams having different temperatures and a hot gas passage which receives heated gas from an electric heater.  
       FIG. 10B  is a cross-sectional view of the heat exchanger apparatus taken along cuffing line  10 B- 10 B in  FIG. 10A .  
       FIG. 11A  is a schematic view of an additional method and system for heat transfer and temperature control of a process fluid wherein the heat exchanger apparatus has a fluid passage component. A case is also shown which has a pair of gas separators in fluid communication with the heat transfer tubes.  
       FIG. 11B  is a perspective view of the heat exchanger apparatus taken along cutting line  11 B- 11 B in  FIG. 11A .  
       FIG. 11C  is a perspective view of the housing of the heat exchanger apparatus shown in  FIG. 11B  with an inlet manifold fitting and an outlet manifold fitting extending through one of the end caps via manifold fitting receptacles. The other end cap is shown with an inlet fitting and an outlet fitting.  
       FIG. 11D  is a cross-sectional view of the heat exchanger apparatus taken along cutting line  11 D- 11 D in  FIG. 11C .  
       FIG. 11E  is a perspective view of the case containing two gas separators.  
       FIG. 11F  is a cut-away view of the case and the two gas separators taken along cutting line  11 F- 11 F in  FIG. 11E .  
       FIG. 12A  is a schematic view of another method and system for heat transfer and temperature control of a process liquid. The heat exchanger apparatus has a housing around a liquid passage component and heat transfer tubes around the liquid passage component. A case is also shown which has a pair of gas separators in fluid communication with the heat transfer tubes.  
       FIG. 12B  is a perspective view and partial cut-away of the heat exchanger apparatus and a perspective view of the case shown in  FIG. 12A .  
       FIG. 13  is a schematic view of yet another method and system for heat transfer and temperature control of a process liquid.  
       FIG. 14  is a perspective view of a tube  140  (without combs) which is wound from one end of fluid directional component (not shown) and then back to the same end. 
    
    
     INDEX OF ELEMENTS IDENTIFIED IN THE DRAWINGS  
      Elements shown in one or more of or discussed with reference to  FIGS. 1, 7 ,  10 A,  11 A,  12 A and  13 :  
       10  process tank  
       20  recirculation pump  
       30  optional component  
       35  bypass line  
       60  controller  
       62  temperature sensor  
       70  compressed gas source  
       72  first valve for gas delivery  
       74  second valve for gas delivery  
      Elements shown in one or more of or discussed with reference to FIGS.  1 ,  2 A- 2 C,  3 a,  4 A- 4 C, and  9 A- 9 B,  10 A- 10 B,  11 A- 11 D, and  14 :  
       100  heat exchanger apparatus  
       110  housing  
       112  shell  
       120  end cap  
       122  access portal  
       124  exhaust vent  
       130  end cap  
       132  inlet opening  
       134  outlet opening  
       140  heat transfer tubes  
       142   i  inlet ends of heat transfer tubes  140   
       142   o  outlet ends of heat transfer tubes  140   
       150  tube support combs  
       152  comb holes  
       160  baffle  
       162  baffle holes  
       164  baffle access  
      Elements shown in one or more of or discussed with reference to  FIGS. 2A-2C ,  3 A,  5 ,  6 A- 6 G and  8 ,  9 A- 9 B,  10 B,  11 B- 11 D,  13  and  14 :  
       200   i  inlet fitting  
       200   o  outlet fitting  
       204   i  anchorable inlet manifold fitting  
       204   o  anchorable outlet manifold fitting  
       205   i  connected inlet manifold fitting  
       205   o  connected outlet manifold fitting  
       206   i  extension of inlet manifold fitting  
       206   o  extension of outlet manifold fitting  
       210   i  inlet manifold fitting  
       210   o  outlet manifold fitting  
       212   i  first end of body  220   i    
       212   o  first end of body  220   o    
       214   i  second end of body  220   i    
       214   o  second end of body  220   o    
       216   i  passages  
       216   o  passages  
       217   i  terminal portion of passage  216   i    
       218   i  face at the first end of body  220   i    
       218   o  face at the first end of body  220   o    
       220   i  body of inlet manifold fitting  
       220   o  body of outlet manifold fitting  
       222   i  seal interface of body  220   i    
       222   o  seal interface of body  220   o    
       224   i  track of body  220   i    
       224   o  track of body  220   o    
       226   i  groove of body  220   i    
       226   o  groove of body  220   o    
       240   i  manifold fitting receptacle  
       240   o  manifold fitting receptacle  
       242   i  threads of manifold fitting receptacle  240   i    
       242   o  threads of manifold fitting receptacle  240   o    
       244   i  sleeve portion of manifold fitting receptacle  240   i    
       244   o  sleeve portion of manifold fitting receptacle  240   o    
       250   i  fitting nut  
       250   o  fitting nut  
       252   i  threads of fitting nut  250   i    
       252   o  threads (not shown) of fitting nut  250   o    
       260   i  fluid communicator  
       260   o  fluid communicator  
       262   i  conduit of fluid communicator  260   i    
       263   i  flared end of neck  264   i  of fluid communicator  260   i    
       263   o  flared end of neck  264 O of fluid communicator  260   o    
       264   i  neck of fluid communicator  260   i    
       264   o  neck of fluid communicator  260   o    
       266   i  elbow of fluid communicator  260   i    
       266   o  elbow of fluid communicator  260   o    
       268   i  neck of fluid communicator  260   i    
       268   o  neck of fluid communicator  260   o    
       269   i  threads  
       260   o  threads  
       270   i  fitting nut  
       270   o  fitting nut  
       299  infrared heater  
      Elements shown in one or more of or discussed with reference to  FIGS. 1, 2C ,  3 A- 3 E,  4 A- 4 C,  8  and  9 A- 9 B,  10 B,  11 A- 11 B,  11 E- 11 F and  12 A- 12 B:  
       300  gas separator case  
       302  exhaust end of gas separator case  
       304  delivery end of gas separator case  
       306  grooves  
       308  baffle rim of gas separator case  300   
       322  gas inlets  
       326  gas channels  
       328  gas channel extension  
       332  exhaust portal for gas separators  400   c  and  400   h    
       334  delivery portals  
       342   c  access portal for gas separator  400   c    
       342   h  access portal for gas separator  400   c    
       360   c  cold gas stream chamber  
       360   h  hot gas stream chamber  
       370  delivery chamber  
      Elements shown in one or more of or discussed with reference to  FIGS. 3A-3E ,  4 A- 4 C,  8 ,  9 A- 9 B,  11 E- 11 F, and  12 A- 12 B:  
       400  hot gas passage  
       400   c  gas separator for delivery of stream of cold gas  
       400   h  gas separator for delivery of stream of hot gas  
       402  gas heater  
       403  inlet to the hot gas passage  400   
       405  channel of hot gas passage  400   
       406  outlet to the hot gas passage  400   
       410   c  flow restrictor for gas separator  400   c    
       410   h  flow restrictor for gas separator  400   h    
       412   c  slot  
       412   h  slot  
       420   c  hot gas separator  
       420   h  hot gas separator  
       422   c  vent holes  
       422   h  vent holes  
       424   c  bands  
       424   h  bands  
       426   c  vent holes  
       426   h  vent holes  
       430   c  stream decoupler  
       430   h  stream decoupler  
       440   c  expansion chamber  
       440   h  expansion chamber  
       450   c  vortex generator  
       450   h  vortex generator  
       452   c  slanted tunnels  
       452   h  slanted tunnels  
       453   c  interior surface or perimeter  
       453   h  interior surface or perimeter  
       460   c  cold gas discharge nozzle  
       460   h  cold gas discharge nozzle  
       470   h  cold gas separator of gas separator  400   h    
       472   h  vent holes  
       490  annular grooves  
       492  O-rings  
      Elements shown in one or more of or discussed with reference to  FIGS. 11A-11E  and  12 A- 12 B:  
       600  coupling tube  
       670  fitting nut  
       1100  heat exchanger apparatus with a liquid passage component  
       1110  housing  
       1120  end cap  
       1122  inlet portal  
       1124  outlet portal  
       1130  end cap  
       1170   i  inlet fitting of the inlet portal  
       1170   o  outlet fitting of the outlet portal  
       1172   i  fitting nut of the inlet portal  
       1172   o  fitting nut of the outlet portal  
       1174   i  channel of the inlet fitting  
       1174   o  channel of the outlet fitting  
       1400  fluid passage component  
       1403  inlet of fluid passage component  1400   
       1405  channel of fluid passage component  1400   
       1406  outlet of fluid passage component  1400   
       1499  weir  
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
      The inventions described hereinafter relate to a recirculation loop heat exchanger apparatus and related methods and systems. The apparatus enables the temperature of a fluid source to be controlled by heat transfer across plastic tubes that isolate the fluid source from the cooling or heating fluid. The inventions also related to specific components as utilized with a recirculation loop heat exchanger apparatus or another apparatus.  
      A heat exchanger apparatus for a recirculation loop has many uses in cooling and/or heating a fluid. One example of such a use is in the manufacture of semiconductors wafers. Maintenance of the temperature of fluids used during the manufacture of semiconductor wafers is needed during many of the processing steps. Examples of such fluids used in the semiconductor manufacturing process include liquids used to etch, liquids used in photolithography processes, rinsing liquids, and cleaning fluids. Examples of etching liquids include hydrogen peroxide (H 2 O 2 ) and acids such as hydrofluoric acid (HF) and hydrochloric acid (HCL). Examples of liquids used in photolithography processes include resist liquids and developer liquids. Slurry solutions and chemicals used in chemical-mechanical planarization (CMP) are also examples of processes that can be sensitive to small changes in temperature. Examples of rinsing liquids include deionized water and liquids used in the process known in semiconductor manufacturing industry as the RCA clean such as RCA rinsing liquids. Components used to contact such liquids are formed from materials which remain chemically inert to the liquid.  
      The heat exchanger apparatus has a small footprint which is ideal for use in the manufacture of semiconductor wafers. Due to the costs of facilities used in the manufacture of semiconductor wafers, it is beneficial to minimize the space required for all devices utilized in the manufacturing process.  
      In addition to controlling the temperature of the source liquid, the heat exchanger apparatus can be used to cool the source liquid from an elevated temperature in preparation for releasing into waste chemical lines. In many semiconductor fabrication facilities, waste line pipes cannot accept fluids warmer than about 50° C., due to the pipe material, and the chemically reactive characteristics of certain waste fluids. Accordingly, liquids, such as those mentioned above which are heated to e.g., 75° C., as is needed for efficient processing, cannot be released into waste lines, without first allowing them to cool down. Ordinarily, heated liquids are allowed to cool in a tank or reservoir within a processing unit. However, the processing unit is then not useable during the cool down interval. Consequently, manufacture of semiconductors is slowed. The heat exchanger apparatus allows this drawback to be minimized, by actively cooling the liquid, instead of storing the liquid in bulk and waiting for it to passively cool down in the tank. Specifically, the heat exchanger apparatus accelerates the rate of cooling and reduces the time required before the liquid source reaches a temperature acceptable for release into manufacturing facility waste lines. As a result, the processing unit is more readily available to process additional flat media.  
      In the embodiments disclosed herein of a heat exchange apparatus, a plurality of heat transfer tubes are helically wound around a fluid directional component for heat transfer. Various embodiments of a fluid directional component are disclosed including a fluid passage component, a temperature changing component, and a blocking component.  
      The fluid passage component and some embodiments of the temperature changing component are configured to block the flow of fluid through the center or main portion of the space defined by the heat transfer tubes while directing the flow of fluid across the tubes. Examples of a fluid passage component include tubular structures. The tubular structure may be utilized to transport a gas or a liquid. An example of a temperature changing component include at least one gas separator. Another example of a temperature changing component is an electrical gas heater.  
      The blocking component is positioned in the housing of the heat exchanger apparatus with the heat transfer tubes positioned around the blocking structure. The blocking component does not deliver a fluid but blocks its fluid flow through the center of the coils of the heat transfer tubes or main portion of the space defined by the heat transfer tubes. An embodiment of a heat exchange apparatus utilizing a blocking component, has fluid delivered directly into the housing so that the fluid flows substantially across the heat transfer tubes from one end of the housing to the other before exiting out of the housing. Examples of blocking components include closed and hollow structures and solid structures. In one embodiment, the blocking component is rod shaped. The blocking component may have any shape which is similar or identical to those of the exterior of the fluid passage components and the temperature changing components disclosed herein. The blocking component may have any shape which substantially blocks fluid flow through the center of the coils so that the fluid is directed substantially across the heat transfer tubes from one end of the housing to the other before exiting out of the housing.  
      The housing of the heat exchange apparatus, the fluid directional component and the heat transfer tubes enable heat to be transferred between two fluids as one of the fluids travels around in the coils of the heat transfer tubes and the other fluid travels in a path that is essentially transverse to the coils. The fluid directional component is configured to direct fluid such that the fluid does not pass through the center of coils and instead directs the fluid from one end of the housing of the heat exchanger apparatus to the other end and across the coils of the heat transfer tubes. For example, a fluid directional component which is a hollow tube or a gas separator receives the fluid and then directs the fluid into the space between the housing and the exterior of the fluid directional component.  
       FIGS. 1, 7 ,  10 A,  11 A,  12 A and  13  provide schematic diagrams of the methods and systems used to alter and control the temperature of a process fluid, without adversely affecting the quality thereof. In one embodiment, the method comprises: sensing the temperature of the process liquid; controlling the delivery of a pressurized gas from a source of pressurized gas; changing the temperature of the pressurized gas; delivering the gas, after its temperature has been changed, to contact at least one plastic heat transfer tube; and circulating a liquid from a source of liquid such that the liquid flows and is in contact with the heat transfer tube to enable the heat transfer tube to heat or cool the liquid contacting the heat transfer tube to control the temperature of the liquid in the source. As described below, the delivery of the pressurized gas can be controlled by selectively delivering the pressurized gas or by selectively adjusting the pressure of the pressurized gas. The embodiments disclosed herein enable the temperature of a liquid in the source of liquid to be maintained in a range from about 0° C. to about 120° C. Some embodiments permit the temperature to be in a range from about 10° C. to about 40° C. Other embodiments permit the temperature to be in a range from about 15° C. to about 30° C.  
      Heat transfer tubes  140  are shown in the schematic diagrams of the methods and systems shown in and described with reference to  FIGS. 1, 7 ,  10 A,  11 A,  12 A and  13 . Perspective views of heat transfer tubes  140  are shown in  FIGS. 2C, 3A ,  4 B,  4 C,  8 ,  9 B,  10 B,  11 D and  12 B. With the exception of the embodiment shown in  FIG. 12B , heat transfer tubes  140  extend helically around a fluid directional component in coils or spirals with varying diameters such that there are coils around coils. Also the coils are different distances from the exterior of the fluid directional component. Stated otherwise, the coils are ringed around each other to create offset layers around the fluid directional component. At least some of the coils are concentric with respect to some of the other coils. These coils are also in a spatial relationship which minimizes their contact with each other. The coiled configuration permits a large volume of heat transfer tubes to be positioned in a small volume of the housing. The coiled and offset configuration of the heat transfer tubes creates a tortuous path for the fluid passing around the heat transfer tubes while maximizing the surface area exposed for transferring heat between the fluids.  
      The fluid flow is forced across the bank of helical tubes between fluid directional component and shell  112 . Flow is generally across tubes and not along the length of the tubes. Enhanced heat transfer is achieved due to mixing caused by flow through the tortuous path created by array of helical tubes.  
      A heat exchange apparatus which has heat transfer tubes helically positioned around a fluid directional component can be manufactured by various methods. For example, heat transfer tubes  140  can be manually positioned around a fluid directional component. The plurality of smaller diameter heat transfer tubes have a reduced bend radius before buckling would occur than a single larger tube with the same flow capacity. The smaller heat transfer tubes may be flexible so that they can be mechanically wound around a fluid directional component and avoid buckling due to their helical configuration within the housing of the heat exchange apparatus. Due to this flexibility, heat transfer tubes  140  may contact each other if support structures are not used to maintain transfer tubes in a particular spatial relationship. Support combs  150  are examples of support structures capable of maintaining heat transfer tubes  140  in their relative positions to other heat transfer tubes. Other support structures capable of maintaining heat transfer tubes  140  in relatively fixed positions may also be used.  
      In some embodiments, the heat transfer tubes are able to maintain their spatial relationship with respect to each other in between support structures and even avoid contacting each other. In other embodiments, the spatial relationship as defined by their relative positions in a support structure is maintained between two support structures in a configuration such that they do not contact each along the majority of the length between the two support structures. While the holes of the support combs are spaced apart to minimize contact between the tubes, the rigidity of the tubes also assists in their ability to avoid contacting each other as the rigidity enables the tubes to maintain their spatial relationship to adjacent tubes between support combs. When tubes are used with increased flexibility, then more support structures may be needed which are more closely positioned with respect to each other to prevent the tubes from contacting each other.  
      Any number of support structures such as combs  150  may be used such as one, two, three, four, five, six, etc. Also, any support structures may be used which are capable of holding the plurality of heat transfer tubes in a generally circular configuration. For example, support structures which hold each coil at three points maintains each coil in a generally circular configuration. In the embodiments depicted herein, three support combs  150  are used to maintain the coils of the plurality of heat transfer tubes in a generally circular configuration.  
      In one embodiment, three support combs are used and each comb has 28 holes per row and 6 holes per column and 12 heat transfer tubes are wound in these holes. The heat transfer tubes may be held in the holes of such an embodiment by threading several of the tubes into an interior row of each of the combs and followed by threading several other tubes into the next outer row. Note that for simplicity, not all of the coils which can be wound around a fluid directional component, are shown. For example, in one embodiment, the number of coils is 4 times greater than the number shown.  
      Comb  150  may, as shown, have holes in a column which are staggered with respect to the holes of an adjacent column and similarly the holes of a row may also be staggered with respect to the holes of an adjacent row. Some tubes  140  may be threaded such that the coils are not parallel and lean with slightly different orientations or with reverse orientations. The tubes positioned in outer rows may have a substantially reverse helix angle with respect to tubes positioned in inner rows.  FIG. 14  depicts a tube  140  (without combs) which is wound from one end and then back such that there is an inner helically wound set of coils and an outer helically wound set of coils. Tube  140  which is shown in  FIG. 14  without other tubes to present a simplistic view depicts a first set of coils having a substantially reverse helix angle with respect to the second set of coils.  
      By positioning coils of heat transfer tubes such that spirals with greater diameters are positioned around coils with smaller diameters, heat transfer tubes can have long lengths while being wrapped around a fluid directional component which is much shorter. For example, in one embodiment, the length of the fluid directional component, may be about 12 inches. In one embodiment, the length of the heat transfer tubes relative to the length of the fluid directional component is about 3:1 to about 100:1. In other embodiments, it ranges from about 5:1 to about 30:1, 10:1 to about 20:1, and 12:1 to about 15:1. Heat transfer tubes  140  may all have the same length or tubes used in a single apparatus may have different lengths.  
      The volume of the heat tubes relative to the volume defined by the exterior of the fluid directional component and the housing of the heat exchange apparatus may range from about 5% to about 75% in one embodiment. The space between the housing the fluid directional component is also referred to as the plenum. In other embodiments, the volume of the heat tubes relative to the volume of the plenum may range from about 10% to about 60%, from about 15% to about 50%, from about 25% to about 45%, from about 30% to about 40%, and about 35%.  
       FIG. 1  depicts an embodiment of the heat exchanger apparatus at  100  which has two temperature changing components identified at  400   c  and  400   h.  The temperature changing components, referred to herein as gas separators, receive pressurized gas and then change the temperature of the gas. Gas separator  400   c  delivers a stream of cold gas into the housing  110  of heat exchanger apparatus  100  while gas separator  400   h  delivers a stream of hot gas into housing  110 .  
      Liquid from process tank  10  flows to heat transfer tubes  140  or other heat transfer tubes via recirculation pump  20  which pressurizes the liquid. The process liquid may optionally return from heat transfer tubes  140  after passing through an optional component  30  such as a flow meter, filter, valve, etc. Liquid may also be routed through a bypass line  35  for high flow to optional component  30  from the line or the fluid communicator which delivers the pressurized liquid to heat transfer tubes  140 . Alternatively, the liquid may return from the heat transfer tubes  140  to feed into the recirculating process between the process tank  10  and the recirculation pump  20 . This enables high fluid flow though the bypass line  35  to be recirculated back to the liquid source. The liquid flowing through the heat exchanger apparatus mixes with the liquid flowing to the recirculation pump. The liquid source temperature can be altered and controlled by controlling the heat transferred to the liquid flow through the heat exchanger apparatus and mixing of the two liquid flows in the recirculation loop.  
      The temperature of process tank  10 , the source of the liquid, is monitored and controlled via a controller  60  which is electronically coupled to a temperature sensor  62 . Temperature sensor  62  is positioned to determine the temperature of the liquid in the process tank.  
      Compressed gas, such as nitrogen or air, is delivered to gas separator  400   c  and gas separator  400   h  in housing  110  of heat exchanger apparatus  100  from compressed gas source  70 . First valve  72  controls gas delivery to gas separator  400   c.  Second valve  74  controls gas delivery to gas separator  400   h.  The compressed gas may be supplied to the gas separator at a flow rate of about 10 to about 35 standard cubic feet per minute (SCFM) and at a pressure of about 50 to 100 psig. For manufacturing semiconductor wafers, the compressed gas is typically supplied to the gas separator at a flow rate of about 15 SCFM and at a pressure of about 80 psig.  
      Apparatus  100  may be utilized to maintain a liquid in a process tank at room temperature (approximately 22° C.). For such a use, apparatus  100  may be designed to adjust the temperature of the process tank or ambient bath by ±5° C. to maintain it at approximately 22° C. Apparatus  100  may also be utilized to heat or cool the liquid beyond ambient temperature. The gas streams or fractions generated by the gas separators may have temperatures ranging from about −40° C. to about 110° C. The cold gas stream generated by the gas separator may have a temperature ranging from about 28° C. to about 50° C. below the temperature of the pressurized gas received by the gas separator. The amount of heat transferred by apparatus  100  varies depending on the design. For example, it may be designed to transfer about 75 to about 300 watts. It may be designed to transfer about 120 watts for typical uses in the manufacture of semiconductor wafers.  
       FIG. 2A  shows housing  110 . Housing  110  comprises shell  112  and end caps  120  and  130 . Shell  112  is the open body of housing  110 . End caps  120  and  130  are at opposite ends and butt up to shell  112 .  
      Inlet manifold fitting  210   i  and outlet manifold fitting  210   o  are shown extending through end cap  130 . Inlet manifold fitting  210   i  and outlet manifold fitting  210   o  are respectively positioned within manifold fitting receptacle  240   i  and manifold fitting receptacle  240   o.    FIG. 5  provides a more detailed view of inlet manifold fitting  210   i  and outlet manifold fitting  210   o.  A method for manufacturing such fittings is described in reference to  FIGS. 6A-6G .  
      Each manifold fitting has a body. Body  220   i  of inlet manifold fitting  210   i  and body  220   o  of outlet manifold fitting  210   o  are formed from a plastic material as described in more detail below. Body  220   i  of inlet manifold fitting  210   i  and body  220   o  of outlet manifold fitting  210   o  respectively hold the inlet ends  142   i  and outlet ends  142   o  of heat transfer tubes  140 . This configuration permits each manifold fitting to be coupled with a single fluid communicator having only one conduit such as a tube or a bulkhead.  FIG. 4B  and  FIG. 9B  show tubes  140  extending through manifold fitting receptacle  240  and positioned in manifold fitting  210 .  
      The clustering of the plurality of heat transfer tubes  140  at their ends enables a large volume of flowing fluid to be delivered from and returned to process tank  10  or another source of fluid and to then be separated into much smaller flowing volumes within housing  110  of apparatus  100 . Separating the fluid into smaller flowing volumes within the separate tubes of the plurality of heat transfer tubes  140  provides for more efficient heat exchange. Tubes  140  have a large surface area, a relatively thin wall thickness, and a relatively small inner diameter. These factors enhance the ability of the fluid in tubes  140  to be heated or cooled by fluid contacting the outside of the tubes  140 .  
       FIG. 2B  shows inlet fitting  200   i  and outlet fitting  200   o  fully assembled. The same components of inlet fitting  200   i  are shown in an exploded perspective view in  FIG. 8 . Note that, as shown, the components of outlet fitting  200   o  and inlet fitting  200   i  may be essentially identical. As shown in  FIG. 2A , manifold fitting receptacle  240   i  and manifold fitting receptacle  240   o  both have threads which are respectively identified at  242   i  and  242   o.  Threads  242   i  and  242   o  are respectively engaged by the threads  252   i  (shown only in  FIG. 5 ) of fitting nut  250   i  and threads  252   o  (not shown) of fitting nut  250   i.  Such threads are examples of locking components.  
      As mentioned above, the configuration of the manifold fittings permits the opposing ends of the plurality of heat transfer tubes  140  to be collectively coupled with a single fluid communicator having only one conduit such as a tube. Fluid communicator  260   i  and fluid communicator  260   o  are examples of such fluid communicators having only a single conduit. The fluid communicator may have more than one conduit. However, it is beneficial for the single conduit or multiple conduits to have a diameter or perimeter that is larger than the inner diameter or inner perimeter of tubes  240 . Conduit  262   i  of fluid communicator  260   i  is shown in  FIG. 5 .  FIG. 4B  and  FIG. 9B  show the transition from manifold fitting  210  to fluid communicator  260 .  
      The embodiments of fluid communicators depicted in  FIG. 2B  each comprise an elbow between necks. As shown in  FIG. 5 , neck  264   i  and neck  264   o  each have a flared end respectively identified at  263   i  and  263   o.  Flared ends  263   i  and  263   o  respectively seal against a seal interface  222   i  of body  220   i  and a seal interface  222   o  of body  220   o.  Respectively extending from the other ends of elbow  266   i  and  266   o  are necks  268   i  and  268   o.  Fitting nut  270   i  and fitting nut  270   o  are respectively positioned onto threads  269   i  and  269   o  of fluid communicator  260   i  and  260   o  to attach a tube or conduit (not shown).  
       FIG. 3A  is an exploded perspective view of heat exchanger apparatus  100 . Gas separator case  300  has an exhaust end  302  opposite from delivery end  304 . Along the length of gas separator case  300  are grooves  306  which receive tube support combs  150 . As shown in  FIG. 2C , heat transfer tubes  140  are positioned within comb holes  152  of tube support combs  150 . Support combs  150  have tabs  154  which are sized to permit them to be positioned in baffles holes  162  of baffle  160 . Baffle  160  has an opening referred to as the baffle access  164  positioned around gas separator case  300  against its baffle rim  308 . The configuration of baffle  160  around gas separator case  300  as it is held between support combs  150  and baffle rim  308  stabilizes support combs  150  and baffle  160 .  
      Pressurized gas is introduced into gas separator case  300  by a compressed gas line (not shown) and into gas inlets  322   c  and  322   h  shown in  FIG. 3B  and  FIG. 4A . The pressurized gas then flows from gas inlets  322   c  and  322   h  respectively via gas channels identified in  FIG. 4B  at  326   c  and at  326   h  to gas separators  400   c  and  400   h.  The gas channel may include an optional gas channel extension such as the extension shown at  328   c  in  FIG. 4C .  
      As discussed in more detail with respect to  FIGS. 3B-3E , gas separator  400   c  and gas separator  400   h  each receive pressurized gas and separate the pressurized gas into two gas streams. Both gas separators separate the pressurized gas they receive into a high temperature stream and a low temperature stream relative to the temperature of the pressurized gas before separation. Gas separator  400   c  directs a relatively cooler gas stream into housing  110  and vents the relatively hotter gas stream it generated to exhaust vent  124 . Gas separator  400   h  directs a relatively hotter gas stream into housing  110  and vents the relatively cooler gas stream it generated to exhaust vent  124 . This configuration enables fluid in tubes  140  to be either cooled or heated as is needed. Note that the gas separators typically operate separately as simultaneous operation would counteract their ability to alter the temperature of the fluid in the tubes. The gas stream used for heat transfer is referred to herein as the heat transfer gas stream while the other gas stream is referred to as the bypass gas stream. Since the heat transfer gas stream delivered by gas separator  400   c  has a low temperature relative to the temperature of the pressurized gas before separation, the letter “c” is used to indicate that its heat exchange gas stream has a relatively cooler temperature. The letter “h” is used in association with gas separator  400   h  as its heat exchange gas stream has a relatively hotter temperature.  
      When gas separator  400   c  delivers a relatively cooler gas stream or gas separator  400   h  delivers a relatively hotter gas stream into the space defined by housing  110  for heat transfer with the fluid in tubes  140 , the gas stream is delivered at delivery end  304  of gas separator case via delivery portals  334 . The other stream of gas vented by gas separator  400   c  (relatively hotter than the pressurized gas) or by gas separator  400   h  (relatively cooler than the pressurized gas), the bypass gas stream, is directed out of housing  100  in manner which limits its contact with the plurality of heat transfer tubes or other heat transfer tubes. Such a gas stream is directly vented via exhaust portal  332  out of gas separator case  300 . As best seen in  FIG. 4A , the bypass gas streams exhausted by gas separator  400   c  and gas separator  400   h  via exhaust portal  332  out of gas separator case  300  are vented out of heat exchanger apparatus  100  via exhaust vent  124  of end cap  120 .  
      Exhaust vent  124 , shown in  FIGS. 3A and 4A , is also the exit for the streams of gas which have been used for the heat transfer with the fluid in tubes  140 . The heat exchange gas streams are released into housing  110  out of gas separator case  300  via delivery portals  334 . After passing by tubes  140 , these gas streams pass out of housing  110  via exhaust vent  124 . As one of the gas separators operates, its heat exchange gas stream and its bypass gas stream recombine in housing  110  at the vent side of baffle  160  and exit exhaust vent  124 . Note that exhaust vent  124  may be threaded for coupling with an external conduit to direct the discharged gas flow to a collector.  
      The heat exchange gas stream passes through baffle holes  162  of baffle  160  before exiting via exhaust vent  124 , as best understood in reference to  FIG. 3A  and  FIG. 4A . Baffle  160  provides uniform flow or distribution across tubes  140  so that the heat exchange gas stream is able to uniformly contact tubes  140 . Baffle  160  provides a physical barrier to enhance circulation so that the heat exchange gas stream does not immediately exit via exhaust  124 . As shown in other embodiments, baffle  160  serves the same purpose with respect to liquids. Baffle  160  also allows the bypass gas stream to exit via the same vent as the heat exchange gas stream while isolating as much as possible the heat transfer tubes from the bypass stream. When the heat exchange gas stream has been released into the space defined by housing  110 , its pressure has dropped significantly as compared with the pressure of the gas when delivered into the gas separator. However, as the heat exchange gas stream flows through baffle  160  and out of exhaust vent  124 , it counters potential ingress of air or gas surrounding heat exchanger apparatus  100 . The physical barrier of baffle  160  also further assists in minimizing the ingress of surrounding gas.  
       FIGS. 3A-3E  provide detailed views of the components of the two gas separators in gas separator case  300  which are identified as gas separator  400   c  and gas separator  400   h.  The general operation of the gas separators and each of their respective individual components will now be described in detail. In the discussion below, each of the components that are common to both gas separator  400   h  and gas separator  400   c  will be described with reference to a generic reference numeral while the same components are identified in the drawings by reference numerals which include the letter “c” or “h” to designate which gas separator the component is used with in gas separator case  300 . Whenever a component in one gas separator is different from the corresponding component in the other or is not present in the other, that component will be described with reference to a specific reference numeral which includes the letter “c” or “h” to designate which gas separator the component is used with in gas separator case  300 .  
      Gas separators  400   c  and  400   h  each include a flow restrictor  410 , a hot gas separator  420 , a stream decoupler  430 , an expansion chamber  440 , a vortex generator  450 , and a cold gas discharge nozzle  460 . Gas separator  400   h  also includes a cold gas separator  470   h.    
      The compressed gas is introduced directly into vortex generator  450  via gas channel  320 . Vortex generator  450  forces the pressurized gas to rotate and thereby create a vortex from the pressurized gas. As seen in  FIG. 3D , vortex generator  450  has a plurality of slanted tunnels  452  that direct the gas along the interior surface or perimeter  453  of the internal bore of the device. Tunnels  452  direct gas into the bore of the gas separator at an angle that is at least approximately tangential to the interior surface  453  to initiate the rotation of the pressurized gas.  
      The vortex is forced down the expansion chamber  440  towards the stream decoupler  430 . The vortex travels down expansion chamber  440  along the inside perimeter of the chamber. Although the expansion chamber shown in the accompanying drawings is tapered such that its interior diameter increases as it approaches the stream decoupler  430 , other embodiments are possible. For instance, the expansion chamber could have a uniform interior diameter or, alternatively, its interior diameter could decrease as it approaches the stream decoupler. Although stream decoupler  430  need not be present in all embodiments of gas separators, it has been found that, under certain conditions, it may be useful to include a stream decoupler to straighten out the vortex somewhat prior to venting the hot gas stream through the hot gas separator  420 . Stream decoupler  430  has an opening with a plurality of projections or vanes  432 , as best seen in  FIG. 3E , which facilitate straightening the outer regions of the vortex.  
      After passing through stream decoupler  430 , the now hot gas at the perimeter of the interior bore of the gas separator is vented by hot gas separator  420 . Although they serve essentially the same purpose, it can be seen from the accompanying figures that hot gas separator  420   h  differs structurally from hot gas separator  420   c.  It should be understood, however, that some embodiments of the invention may have two gas separators, each of which have components which are identical.  
      Hot gas separator  420   h  has a plurality of vent holes  422   h.  The hot gas stream is vented through the hot gas separator  420   h  and then out through vent holes  422   h.  As is discussed in greater detail below, the amount of hot gas that is allowed to vent through vent holes  422   h  may be controlled by controlling how far flow restrictor  410   h  is threaded into hot gas separator  420   h.    
      Hot gas separator  420   c  instead directs the hot gas through vent holes  422   c  that lead back towards the center of the device and outside of the interior bore. Optionally, one or more bands  424  may be disposed around the perimeter of the region to which the hot gas is directed, as shown in the accompanying figures. These bands  424  may also have vent holes  426   c  that are coaxial with vent holes  422   c.  Bands  424  may be used to provide support for a gas permeable muffling cover (not shown). Such a cover may be comprised of any suitable material which allows gas to permeate there through and may be tightly fit over bands  424  in order to reduce the noise associated with venting the hot gas.  
      After the hot gas stream is vented from the gas separator, the remaining gas stream is reflected off of flow restrictor  410  and travels down the center of the gas separator in the opposite direction. Flow restrictor  410  may be adjustable so as to allow the temperature and volume of the cold and hot streams of gas to be varied. In the depicted embodiment, adjustment of flow restrictor  410  may be made by screwing and unscrewing the flow restrictor  410 . For example, a screwdriver may be inserted via access portal  122  of housing  100  and access portal  342   c  of gas separator case  300  into slot  412   c.  As the flow restrictor  410  is unscrewed, or threaded away from the hot gas separator  420 , a greater portion of hot gas is released from the hot gas separator  420 . This likewise affects the volume and temperature of cold gas released from the opposite side of the gas separator. Note that, as shown in  FIG. 4A , access portal  342   c  for gas separator  400   c  is adjacent to access portal  342   h  for gas separator  400   c    
      As it travels down the center of the gas separator, the gas transfers heat to the gas spiraling in the other direction along the interior perimeter of the gas separator and is thereby cooled. In the depicted embodiment, the cold gas is vented through cold gas discharge nozzle  460 . Cold gas discharge nozzle  460  may optionally be adapted to be fit with a vent tube to direct the cold gas to a desired location. In the depicted embodiment, cold gas discharge nozzle  460   c  sends the cold gas stream down a portion of gas separator case  300 , including the cold gas stream chamber  360   c  and delivery chamber  370 , and out one or more delivery portals  334  in case  300 , which allows the gas stream to contact the heat transfer tubes  140 . Note that delivery chamber  370  also receives hot gas from hot gas stream chamber  360   h  as the hot gas proceeds out of delivery portals  334 .  
      A gas permeable muffler (not shown) may be located in the vent tube. For example, a muffler may comprise a plastic material, such as a woven polypropylene around hot gas separator  420   c  or an open cell foam in delivery chamber  370 . Such a device may be comprised of any suitable material which allows gas to permeate there through and reduce the noise associated with venting the cold gas.  
      Gas separator  400   h  has an additional component-cold gas separator  470   h —which is connected with cold gas discharge nozzle  460   h.  Cold gas separator  470   h  has vent holes  472   h,  which direct a cold gas stream out of the heat exchanger apparatus  100  via exhaust vent  124 . Like hot gas separator  420   c,  cold gas separator  470   h  may have one or more bands  474   h,  and may also be fit with a gas permeable muffling cover (not shown) similar to that described above in connection with the hot gas separator  420   c.    
      In embodiments of the invention including two gas separators, such as the embodiment shown in  FIGS. 3A-3C  having gas separators  400   c  and  400   h,  cold gas and hot gas stream can alternatively or simultaneously be introduced into the space defined by the apparatus housing  110  and adjacent to the heat transfer tubes  140 . This allows for maintenance of a liquid bath at a relatively constant temperature, within any desired range of temperatures, which is located remotely with respect to apparatus  100 . In other words, when the liquid bath is at or near a temperature which is undesirably high, gas separator  400   c  is utilized, which introduces cold gas into the space adjacent to heat transfer tubes  140 . Likewise, when the liquid bath is at or near a temperature which is undesirably low, gas separator  400   h  is utilized, which introduces hot gas into the space adjacent to heat transfer tubes  140 .  
      Of course, embodiments of the invention having only a single gas separator are also envisioned as described in reference to  FIGS. 7-8  and  FIGS. 9A-9B . Such embodiments may be used, for example, in environments in which it is desirable to keep a liquid bath above or below the environment temperature. For instance, if it is desired to keep a liquid bath at a temperature below the temperature of the environment, only a single gas separator is necessary to introduce cold gas into the heat transfer tubes.  
      Many of the fundamental aspects of the gas separators are well-known to those of skill in the art, as demonstrated by U.S. Pat. No. 3,173,273 issued to Fulton; U.S. Pat. No. 4,240,261 issued to Inglis; U.S. Pat. No. 5,558,069 issued to Stay; U.S. Pat. No. 5,682,749 issued to Bristow et al.; and U.S. Pat. No. 6,032,724 issued to Hatta. All of the foregoing references are hereby incorporated by reference in their entirety.  
      Gas separators  400  may be fit within gas separator case  300 , which may be configured to receive one or more gas separators. Gas separators  400  or, more particularly, one or more gas separator components, may also be configured with annular grooves  490 . Each annular groove  490  may then be fit with in O-ring  492 . Use of O-rings allows for creation of one or more seals to direct the gas to desired locations and/or prevent the passage of gas to undesired locations.  
       FIG. 5  depicts inlet fitting  200   i  in an exploded perspective view. In addition to the other components of inlet fitting  200   i,  inlet manifold fitting  210   i  is best seen in  FIG. 5 . Inlet manifold fitting  210   i  has a body  220   i  with a first end  212   i  opposite from a second end  214   i.  Passages  216   i  extend from first end  212   i  to second end  214   i.    
       FIGS. 6A-6G  depict the manufacture of inlet manifold fitting  210   i.    FIG. 6A  depicts tubes  140  after being pulled through passages  216   i  and beyond first end  212   i  of inlet manifold fitting  210   i.  Note that the while the outer diameter of each tube  140  may be slightly smaller than the diameter of each passage  216   i,  they may also be approximately the same. Ends of tubes  140  are then cut off as shown in  FIG. 6B  to be as close as possible to being essentially flush with face  218   i  of body  220   i.    FIG. 6C  depicts infrared heater  299  exposing at least a portion of body  220   i  and tubes  140  to fuse at least body  220   i  and tubes  140  at face  218   i.    
       FIGS. 6D-6E  depict an embodiment of manifold fitting  210   i  having passages  216   i  in its body  220   i  with terminal portions  217   i  which have a greater diameter at the first end  212   i  of body  220   i.  In some embodiments, inlet ends  142   i  of heat transfer tubes  140  expand upon being heated. To a less extent, in some embodiments, passages  216  of body  220  may collapse radially inward upon being heated as may the inlet ends  142  of heat transfer tubes  140  upon cooling. The spacing enables inlet ends  142   i  to expand radially outward during heating and to fuse with terminal portions  217   i  of body  220   i.  For example, in an embodiment wherein manifold fitting  210   i  and heat transfer tubes  140  are formed from polyperfluoroalkoxyethylene (PFA) and heat transfer tubes  140  have an outer diameter which is 0.158 inches and a wall thickness which is 0.02 inches, the diameter of passages  216   i  at first end  212   i  is 0.166 inches. In various embodiments, the diameters of the terminal portions of the channels and the inlet ends of the heat transfer tubes differ in diameter in a range of about 2% to about 10%. In other embodiments, the range is about 4% to about 6%. In yet another embodiment, the diameters differ by about 5%.  
       FIGS. 6F-6G  depict the inlet ends  142   i  of heat transfer tubes  140  before and after being fused to body  220   i.  As shown in  FIG. 6F , tubes  140  and body  220   i  are distinct from each other at the initiation of being heated. More particularly, the outer diameter of tubes  140  are not mechanically attached to body  220   i.  After being heated, as shown in  FIG. 6G , the outer diameter of tubes  140  have fused with body  220   i  such that they are mechanically attached and the complete perimeter is sealed to body  220   i.    
      The objective of heating tubes  140  and the portion of body  220   i  below face  218   i  is to form a fluid-tight seal between the outer diameter of tubes  140  and body  220   i  so when fluid is transferred from a fluid communicator all of the fluid flows into tubes  140  and not around tubes  140  into passages  216   i.  When heat is applied, the circular tubes expand and engage the passages  216   i.  When the materials reach their melting point temperatures, the tubes  140  and body  220   i  fuse together at heated face  218   i  and directly below the heated face  218   i.  Such results are achieved primarily through the use of plastics which are either identical or are sufficiently compatible to have similar melting temperatures. Other variables include the duration of the exposure to the heating source, the temperature of the heating source, the proximity of the heat source to face  218   i,  and the wall thickness of tubes  140 .  
      The bodies of the manifold fittings and tubes  140  may be formed from any plastic material which remains inert to fluids such as hydrofluoric acid and other liquids used in manufacturing semiconductor wafers. Fluoropolymers are examples of suitable plastics. Specific examples of fluoropolymers which remain inert during exposure to various fluids include: polytetrafluoroethylene (PTFE) sold as Teflon, fluorinated ethylene propylene (FEP), polyperfluoroalkoxyethylene (PFA) and polyvinyl difluoride (PVDF). Other plastics which may be utilized include polypropylene (PP), polyvinyl chloride (PVC), and polyvinyl difluoride (PVDF). The other components of heat exchanger apparatus  100  may also be formed from such plastics.  
      The plastic components are heated at or above their melting points to fuse portions of the tubes within the passages of the body of manifold fitting to the upper portion of the body of manifold fitting. Utilizing plastics which are identical or relatively similar enables the plastic components to simultaneously reach their melting points or reach them at very similar temperatures. Proper selection of such plastics ensures that one component does not receive excessive heat once it reaches its melting point as the other component is still approaching its melting point. Avoidance of excessive heating assists in preserving the geometrical shape of the inner diameter of the tubes. Deformation of the tubes from their original geometry during heating could prevent a fluid from freely flowing through the tubes.  
      The longer that the components are exposed to the heat then the deeper the penetration of the heat. The weld depth may be twice the thickness of the wall of the tubes to ensure that there is a secure seal. As mentioned above, the walls of tubes  140  are selected to be sufficiently thin to permit rapid and efficient heat transfer. The wall thickness is also selected to be sufficiently thick to withstand the pressure of the pressurized liquid and to prevent weeping of the fluid. For example, when the fluid is hydrofluoric acid (HF) pressurized to about 45 psi, the tube may have a wall thickness ranging from about 0.01 inches to about 0.02 inches. More particularly, a tube formed for such use from polyperfluoroalkoxyethylene may have a wall thickness of about 0.02 inches. To fuse such tubes to the body of a manifold fitting, an infrared heater is set at a temperature of 600° F. and positioned about 0.5 inch away from the face of the body of the manifold fitting and the inlet ends of the tubes for about 1 minute.  
      The embodiment of heat exchanger apparatus  100 ′ shown in  FIGS. 7-8  and  FIGS. 9A-9B  which has only a single gas separator is essentially identical to the heat exchanger apparatus shown in  FIGS. 1-4C . As mentioned above, embodiments with only one gas separator may be used in environments in which it is desirable to keep a liquid bath above or below the environment temperature.  
      Like the embodiment of the heat exchanger apparatus having two gas separators, a heat exchanger apparatus having a single gas separators controls the delivery of the gas stream contacting the plurality of heat transfer tubes by: selectively enabling the gas to flow into the gas separator, selectively adjusting the pressure of the gas flowing into the gas separator, selectively adjusting the gas separator to alter the ratio of a cold or hot gas stream.  
      As best seen in  FIG. 9A , end cap  120 ′ has a different configuration compared with end cap  120  since there is only one gas separator in this embodiment of the heat exchanger apparatus. Flow restrictor  410   c  for gas separator  400   c  is accessed by access portal  122 . The other components shown in  FIG. 8  are identical to those shown in  FIG. 3A . As discussed below with reference to  FIG. 9B , the internal configuration of gas separator case  300 ′ differs from gas separator case  300 .  
       FIG. 9B  shows the same view of apparatus  100 ′ as is shown of apparatus  100  in  FIG. 4C . Since gas separator  300   c  is the only gas separator in gas separator case  300 ′, it is centered differently from separator  300   c  within gas separator case  300 . Another difference is that there is not a delivery chamber as the cold gas stream chamber  360   c  directly delivers the cold gas stream out of delivery portals  334 .  
       FIG. 10A  depicts a schematic view of a method and system for heat transfer and temperature control of a process liquid which differs from the method and system shown in  FIG. 1  by replacing gas separator  400   c  with a hot gas passage  400  which receives heated gas from a gas heater  402 . In some embodiments, a gas heater delivers more heat than a gas separator.  
      Gas heater  402  is in fluid communication with hot gas passage  400 . In the embodiment shown in  FIG. 10A , gas heater  402  is positioned outside of heat exchanger apparatus  100 ″. In another embodiment, the gas heater is within the heat exchanger apparatus. Any device capable of heating a pressurized gas and then transmitting the heated gas to hot gas passage  400  may be used as gas heater  402 . For example, gas heater  400  may be a conventional electrical heater having a resistive element such as nichrome which defines a channel through which the pressurized gas passes. The resistive element may be separated from an outer casing formed from a material such as stainless steel by an insulator such as a ceramic. Alternatively, an electric heating element may be positioned in the hot gas passage  400  to heat the gas as it passes over the heating element and delivered to the outlet for the hot gas passage  406 . An example of a heater element is Omegalux CIR-5065 sold by Omega Engineering, Inc. Those of ordinary skill in the art would recognize the need for electrical heater controls and safety devices along with needed heater mounting adaptors to position the heating element in the hot gas passage  406  and to effectively transfer and control heat to the flowing fluid. Alternatively, an electric heating element positioned around the outside of housing  110 , within housing  110 , or on the inside surface of housing  110  could be used to heat the fluid before and while it is flowing across the heat transfer tubes. An example of a heater element is a Kapton® insulated flexible heater part number KH-1012/(5)-P sold by Omega Engineering, Inc. Those of ordinary skill in the art would recognize the need for electrical heater controls and safety devices along with methods to mount the heating element on or within the housing  110  of the apparatus and effectively transfer heat to the flowing fluid.  
       FIG. 10B  depicts the tubular structure of hot gas passage  400 . Hot gas passage  400  has an inlet  403  opposite from an outlet  406 .  FIG. 10B  also shows channel  405  extending between inlet  403  and outlet  406 .  
       FIG. 11A  is a schematic view of an additional method and system for heat transfer between a fluid and a process liquid without adversely affecting the quality of the process liquid. The temperature of the process liquid is controlled by directing the process liquid through a fluid passage component  1400  which permits heat transfer with the flow of large volumes of fluids. Fluid passage component  1400  is a tube configured to receive a process liquid and to then deliver the process liquid into a heat exchanger  1100  for the exchange of heat with heat transfer tubes  140  which are wound around fluid passage component  1400 . The temperature of the fluid in the heat transfer tubes is adjusted in the embodiment shown in  FIG. 11A  by a pair of gas separators in fluid communication with heat transfer tubes  140  including a gas separator  400   c  for a cold gas stream and a hot gas separator  400   h  for a hot gas stream. The gas separators are contained in a case  300 ″.  
       FIG. 11B  depicts heat exchanger apparatus  1100  and case  300 ″. A gas stream is delivered from one of the gas separators to heat transfer tubes  140  via a coupling tube  600  which is connected with inlet fitting  200   i.  A fitting nut  670  secures coupling tube  670  to case  300 ″.  
       FIG. 11C  shows end caps  1120  and  1130  heat exchanger apparatus  1100 . Like end cap  130  of heat exchanger apparatus  100 , end cap  1130  of heat exchanger apparatus  1100  has an inlet opening  132  and an outlet opening  134 . As shown in  FIG. 11D , end cap  1120  has an inlet portal  1122  and an outlet portal  1124 . Housing end caps  1120  and  1130  are welded to the shell  112  to seal the housing and withstand the process liquid pressure flowing through the heat exchanger apparatus  1100 .  
       FIG. 11D  also shows an inlet fitting  1170   i  extending through inlet portal  1122  and an outlet fitting  1170   o  extending through outlet portal  1124 . Each fitting  1170  has a fitting nut  1172  and a channel  1174  extending through the fitting. The fittings connect the heat exchanger apparatus  1100  to the process fluid conduits. Perspective views of fitting nuts  1172   i  and  1172   o  are shown in  FIGS. 11B-11C .  
       FIG. 11D  shows the pathway for a process fluid. The process fluid enters inlet  1403  of fluid passage component  1400  via channel  1174   i  of inlet fitting  1170   i  and travels through channel  1405 . The process fluid exits channel  1405  via outlet  1406  and passes out of fluid passage component  1400  and into the space defined by housing  110  around fluid passage component  1400 . The fluid pressure then directs the fluid to pass across heat transfer tubes  140 . Alternatively, the direction of fluid flow can be reversed.  
      As described above, the plurality of heat transfer tubes  140  are adapted to contain a fluid and are helically wound around and along at least the majority of the length of a fluid directional component such as fluid passage component  1400  or a temperature changing component such as case  300  of gas separators or a heater. Housing  100 , the fluid directional component and heat transfer tubes  140  enable heat to be transferred between the two fluids as one of the fluids travels around in the coils of the heat transfer tubes and the other fluid travels from the inlet of the fluid directional component to the outlet of the fluid directional component. The fluid passing across heat transfer tubes  140  in housing  110  travels in a direction which is essentially parallel with an axis of housing  110  or fluid directional component and essentially transverse with respect to the coils of heat transfer tubes  140 .  
       FIGS. 11E-11F  depict gas separators  400   c  and  400   h  held in case  300 ″ The components of gas separators  400   c  and  400   h  are identical to those of the gas separators discussed above. Case  300 ″ also has the same components as the other cases which enclose gas separators, however, some of the components have slightly different configurations. For example, gas inlets  322   c  ″ and  322   h  ″ provide more direct pathways than gas inlets  322   c  and  322   h.  The embodiment of the case shown at  300 ″ has only a single exhaust portal  332 ″ and a single delivery portal  334 ″.  
       FIGS. 12A-12B  depict another embodiment of a method and system for heat transfer and temperature control of a process liquid. The heat exchanger apparatus  1100 ′ comprises a housing  1110 ′ around a liquid passage component  1400 ′ and heat transfer tubes  140  around liquid passage component  1400 ′. Liquid passage component  1400 ′ is a process tank or more particularly, a conventional overflow weir. Liquid which rises above the weir  1499 ′ flows over weir  1499 ′ and into housing  1110 ′, or more particularly an outer tank. Housing  1110 ′ has an outlet portal  1124 ′ through which gas is expelled from outlet ends  142   o  of heat transfer tubes  140 .  
      The embodiment shown in  FIGS. 12A-12B  has the identical case  300 ″ and gas separators  400   c  and  400   h  as the embodiment shown and described with reference to  FIGS. 11A-11F . Like the embodiment shown and described with reference to  FIGS. 11A-11F , a gas separator can also be replaced by a heater and a tube as described above.  
       FIG. 13  depicts a schematic view of another method and system for heat transfer and temperature control of a process liquid. The system involves heat transfer between two liquids and is particularly useful for higher heat transfer rates. Cold liquid source  70   c  and hot liquid source  70   h  are respectively delivered to fluid directional component  1400  via valves  72  and  74 . In one embodiment, hot deionized water is used as hot liquid source  70   h  to transfer heat to a process liquid. The deionized water may have a temperature of about 10° C. to about 120° C. and be useful for adjusting the temperature of the process liquid to a temperature ranging from about 15° C. to 95° C. For example, when 12 heat transfer tubes are used which each have a length of about 30 feet and have an outer diameter of 0.158″ and an inner diameter of 0.118″, deionized water having a temperature of about 90° C. can be used as the hot liquid source to transfer heat to a process liquid having a temperature of 30° C. such that about 6000 watts of heat is transferred.  
      The other components in  FIG. 13  are substantially identical to those which are identically numbered in the other schematic drawings. Note that the methods and systems described herein can be used for heat transfer between any two fluids including liquid/liquid, gas/liquid, liquid/gas and gas/gas.  
      The heat transfer tubes disclosed herein are examples of heat transfer components. The heat transfer tubes are also examples of heat transfer means for receiving a pressurized fluid in the housing for heat transfer as delivered from a fluid source, providing sufficient surface area for effective heat and transfer and for delivering the fluid out of the housing to be routed back to the fluid source.  
      The support combs are examples of support structures. Support structures are examples of means for spatially orienting the heat transfer means for effective heat transfer. The baffle is an example of means for directing the heat transfer gas stream across the heat transfer means, for minimizing contact with the heat transfer means from the bypass gas stream as the bypass gas stream is directed out of an exhaust vent, and for directing the heat transfer gas stream out of the exhaust vent after the heat transfer gas stream has contacted the heat transfer means.  
      As indicated above, a gas separator is an example of a temperature changing component. The gas separators are also examples of temperature changing means for receiving pressurized gas, for separating the pressurized gas into a high temperature stream and a low temperature stream relative to the temperature of the pressurized gas received, for directing one of the gas streams into contact with the plurality of heat transfer components and then out of the housing, and for directing the other stream out of the housing while limiting the contact with the heat transfer means. Such temperature changing means are also examples of means for cooling or heating the fluid in the heat transfer means. Other examples of means for heating or cooling the fluid in the heat transfer means include a hot bath or cold bath through which the heat transfer means passes.  
      Another example of a temperature changing component is a gas heater. Some embodiments of gas heaters are examples of temperature changing means for receiving a pressurized gas, heating the gas and directing the gas into contact with the plurality of heat transfer components. The gas heaters are also examples of means for heating the fluid in the heat transfer means.  
      The temperature changing components are examples of fluid delivery components. Other examples of fluid delivery components include fluid passage components. Examples of fluid passages components include tubular structures. Temperature changing components and fluid passage components are examples of fluid delivery components as they are able to receive a fluid and then direct the fluid into the space between the housing and the exterior of the fluid delivery component. The fluid delivery components are examples of means for receiving a fluid into the housing and delivering the fluid into contact with the plurality of heat transfer tubes.  
      The fluid delivery components are also fluid directional components. Other examples of fluid directional components include blocking components. In contrast to fluid delivery components, a blocking component does not deliver a fluid is just blocks its flow through the center of the coils. An embodiment utilizing a closed, hollow, rod-shaped structure positioned along the center axis of the housing of the heat exchanger apparatus to act as a blocking component, has fluid delivered directly into the housing so that the fluid flows substantially across the heat transfer tubes from one end of the housing to the other before exiting out of the housing.  
      A fluid directional component is positioned in the housing of the heat exchanger apparatus with the heat transfer tubes positioned around the blocking component to block the flow of fluid through the center or main portion of the space defined by the heat transfer tubes. Whether the fluid directional component is hollow like a fluid passage component, contains various structural components such as a gas separator, or is a solid blocking component, these embodiments of the fluid directional component direct fluid substantially across the coils from one end of the housing of the heat exchanger apparatus to the other end while minimizing or preventing flow through the center of the coils of the heat transfer tubes. The fluid delivery components positioned within the coils and the blocking components are examples of means for directing the fluid across the coils and minimizing or preventing flow through the center of the coils of the heat transfer tubes.  
      The inlet manifold fittings are examples of inlet manifold means for providing fluid communication between the plurality of heat transfer means and an inlet fluid communicator having a conduit in fluid communication with the fluid source to enable the plurality of heat transfer means to receive the pressurized fluid in the housing from the fluid source. The outlet manifold fittings are examples of outlet manifold means for providing fluid communication between the plurality of heat transfer means and an outlet fluid communicator having a conduit in fluid communication with the fluid source to enable the plurality of heat transfer means to deliver the pressurized fluid out of the housing to the fluid source.  
      All of the heat exchanger apparatus components, except the electrical heating element and associated control devices as described previously, can be constructed of non metallic materials enabling the apparatus to be exposed to the process liquids without adversely changing the operation of the heat exchanger apparatus.  
      Without further elaboration, it is believed that one skilled in the art can use the preceding description to utilize the invention to its fullest extent. The examples and embodiments disclosed herein are to be construed as merely illustrative and not a limitation of the scope of the present invention in any way. It will be apparent to those having skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. In other words, various modifications and improvements of the embodiments specifically disclosed in the description above are within the scope of the appended claims. Note that elements recited in means-plus-function format are intended to be construed in accordance with 35 U.S.C. § 112 ¶6. The scope of the invention is therefore defined by the following claims.