Abstract:
A dished head header assembly for a heat exchanger having a containment body that includes a rounded, or dished, wall portion forming an interior cavity. A flange attaches to the containment body and fastens the header assembly to the heat exchanger. A plurality of refrigerant passageways are extended through an opening in the containment body into the interior cavity. At least one baffle is attached to the rounded wall portion. The baffle divides the interior cavity into a plurality of sub-cavities. At least one divider divides the sub-cavities into a plurality of chambers. The plurality of passageways includes an inlet connection and an outlet connection for a plurality of refrigerant circuits. Each passageway is disposed in a corresponding chamber of the plurality of chambers. Extensions into the headers with diffusers insure efficient operation and performance of the heat exchanger. The adjustable flow restrictor plate maintains optimum velocities to further enhance performance.

Description:
FIELD OF THE INVENTION 
   The present invention is directed to shell and tube heat exchangers. In particular, the present invention is directed to headers for shell and tube heat exchangers used with heating ventilation and air conditioning (HVAC) systems. 
   BACKGROUND OF THE INVENTION 
   Shell and tube heat exchangers typically include headers on each end of the shell in order to provide access to the tubes within the shell for cleaning or service. The headers also provide containment for refrigerant or heat exchange fluid and provide the refrigerant or heat exchange fluid to the tubes. Chiller systems typically include a chiller heat exchanger, which is a shell and tube heat exchanger having a refrigerant flow in the tubes and heat exchange fluid, such as water, flowing in the shell. Each end of the chiller heat exchanger includes a header fastened to the shell. The header includes a flat head plate and a baffle chamber. The head plate is a flat, thick plate that provides containment of the refrigerant within the system. A gasket is placed between the head plate and the baffle chamber in order to reduce leakage. The baffle chamber contains one or more baffles to direct the flow of refrigerant into the tubes of the shell. The baffles also substantially prevent leakage between the inlet and outlet. A second gasket is placed between the baffle chamber and the shell in order to reduce leakage. Chiller systems may also include multiple refrigerant circuits having refrigerant loops that are independent of each other. In systems having multiple circuits, a divider between the circuits must also be included in the baffle chamber and independently attached. The divider requires bolts that fasten the divider to the end of the shell, adding to the complexity of installation, requiring additional gaskets, reducing the area available for tubes within the shell, and causing additional stress on the bolts fastening the header to the shell. These chiller heat exchangers have the additional drawback that multiple gaskets are required, thus increasing the occurrences of leakage of refrigerant and increasing the service costs. These chiller heat exchangers have the further drawback that the flat plate on the header is relatively thick and heavy, thereby increasing material cost and weight of the system. Additional bolts positioned at the center of the flat head, referred to as center bolts, are required on the flat heads to try to minimize deflection and avoid excessively thick heads. However, these center bolts are generally overstressed and result in additional leakage paths and cost. 
   Therefore, what is needed is a header assembly that contains refrigerant, requires simpler gasketing, weighs less, costs less, provides reduced stress for the fasteners attaching the head to the heat exchanger, provides high velocity refrigerant flow, and high efficiency operation, and eliminates the center bolts. 
   SUMMARY OF THE INVENTION 
   The present invention includes a dished-head header assembly for a heat exchanger having a containment body. The containment body includes a rounded, or dished, wall portion forming an interior cavity. A flange attaches to the containment body and fastens the header assembly to the heat exchanger. A plurality of refrigerant passageways are extended through an opening in the containment body into the interior cavity. At least one baffle is attached to the rounded wall portion. The baffle divides the interior cavity into a plurality of sub-cavities. At least one divider divides the sub-cavities into a plurality of chambers. The plurality of passageways includes an inlet connection and an outlet connection for a plurality of refrigerant circuits. Each passageway is disposed in a corresponding chamber of the plurality of chambers. Extensions into the headers with diffusers insure efficient operation and performance of the heat exchanger. The adjustable flow restrictor plate maintains optimum velocities to further enhance performance. 
   The present invention also includes another embodiment including a header assembly for attachment to a heat exchanger. The header assembly include a containment body having a rounded wall portion that forms an interior cavity. A flange portion is attached to the containment body and is configured to fasten the header assembly to the heat exchanger. At least one divider is attached to the containment body and is configured and disposed to divide the interior cavity into a plurality of chambers. A gasket is arranged and disposed to seal the chambers of the containment body against the heat exchanger to substantially prevent leaks of refrigerant to the atmosphere and between the plurality of chambers when the header assembly is attached to the heat exchanger. The plurality of chambers include a return chamber each corresponding to a refrigerant circuits. 
   The present invention also includes a heat exchanger, including chiller heat exchangers. The heater exchanger includes a shell for containing heat transfer fluid having a first end and a second end. A plurality of tubes for containing refrigerant are arranged and disposed within the shell. The plurality of tubes includes a first set of tubes and a second set of tubes. A first header assembly is detachably fastened to the first end and includes a first containment body. The first containment body includes a first rounded wall portion forming a first interior cavity. A flange attaches to the containment body and fastens the first header assembly to the shell. A plurality of refrigerant passageways are extended through an opening in the first containment body into the first interior cavity. At least one baffle is attached to the first rounded wall portion. The baffle divides the interior cavity into a plurality of sub-cavities. At least one first divider divides the sub-cavities into a plurality of chambers. The plurality of refrigerant passageways includes an inlet connection and an outlet connection for a plurality of refrigerant circuits. Each passageway is disposed in a corresponding chamber of the plurality of first chambers. 
   A first gasket is disposed between the first header assembly and the first end of the shell to substantially prevent leakage of refrigerant from the first header assembly. A second header assembly is detachably fastened to the second end of the shell. The second header assembly includes a second containment body having return chambers. The second containment body includes a second rounded wall portion forming an interior cavity. A flange attaches to the second containment body and fastens the header assembly to the shell. A gasket seals the chambers of the second containment body against the heat exchanger in order to substantially prevent leaks of refrigerant to the atmosphere and seals between the plurality of return chambers when the header assembly is attached to the heat exchanger. At least one divider divides the cavity into a plurality of chambers. The plurality of chambers includes a return chamber for each refrigerant circuit. A second gasket is disposed between the second header and the second end substantially preventing leakage of refrigerant from the second header assembly. 
   One advantage of the present invention is that the rounded header geometry provides containment of the refrigerant with less material, stronger attachment to the flange and variable chamber sizes via flow restrictor plates to maintain high refrigerant velocities and high operating efficiency. 
   Another advantage of the present invention is that the header assembly only requires a single gasket between the shell and the header. The reduction in the number of gaskets provides a more reliable seal that has reduced leaks and reduced service costs. 
   Another advantage of the present invention is the lack of center bolts attaching the header to the shell. Center bolts are not required because of the inherent strength and efficiency of the rounded/dished heads. The removal of the need for center bolts provides a seal that is easier to maintain, provides less stress on the bolts of the flange and provides a greater amount of area in which tubes for heat exchange may be installed. 
   Another advantage of the present invention is the attachment of the baffles to the header, providing a single piece for installation. Utilizing a single piece header allows for installation that is simpler and less susceptible to leakage. 
   Another advantage of the present invention is that the inlet piping is attached to the header and extended into the inlet and outlet chambers for more direct flow, increasing the velocity of the refrigerant and efficiency of the operation of the heat exchanger. In addition, the extended nozzles are easier and less costly to fabricate. Diffusers at the end of the extended nozzles facilitate efficient operation and improve performance. 
   Another advantage of the present invention is that the baffles may be arranged in a plurality of configurations, which can adjust the size of the chambers within the head. Adjustment of the chamber size provides control of the velocity of the refrigerant and residence time of the refrigerant in the header. The control of the velocity and residence time allows the header to be customized to the particular application and/or retrofitted to existing heat exchangers. 
   Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a side view of a known chiller heat exchanger. 
       FIG. 2  shows a side view of a chiller heat exchanger according to the present invention. 
       FIG. 3  shows a cutaway view of a chiller heat exchanger according to one embodiment of the present invention. 
       FIG. 4A  shows a cutaway side view of an inlet/outlet header according to one embodiment of the present invention. 
       FIG. 4B  shows a cutaway front view of an inlet/outlet header according to one embodiment of the present invention. 
       FIG. 5A  shows a cutaway side view of a return header according to one embodiment of the present invention. 
       FIG. 5B  shows a cutaway front view of a return header according to one embodiment of the present invention. 
       FIG. 6  shows a perspective view of an inlet/outlet header according to one embodiment of the present invention. 
       FIG. 7  shows a perspective view of a return header according to one embodiment of the present invention. 
       FIG. 8A  shows a cutaway side view of an inlet/outlet header according to an alternate embodiment of the present invention. 
       FIG. 8B  shows a cutaway front view of an inlet/outlet header according to an alternate embodiment of the present invention. 
       FIG. 9A  shows a cutaway side view of a return header according to an alternate embodiment of the present invention. 
       FIG. 9B  shows a cutaway front view of a return header according to an alternate embodiment of the present invention. 
       FIG. 10  shows a perspective view of an inlet/outlet header according to an alternate embodiment of the present invention. 
       FIG. 11  shows a perspective view of a return header according to an alternate embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   HVAC systems may include refrigerant circuits having a compressor, a condenser, and an evaporator connected in a refrigerant loop. Refrigerant is circulated through the refrigerant loop to the various components. The compressor compresses refrigerant vapor and delivers it to the condenser. The refrigerant vapor delivered by the compressor to the condenser enters into a heat exchange relationship with water or other suitable heat exchange fluid, heating the water while undergoing a phase change to a refrigerant liquid as a result of the heat exchange relationship with the water. The refrigerant leaves the condenser and is delivered to an evaporator. One type of evaporator or cooler is referred to as a chiller heat exchanger, commonly referred to as a direct expansion heat exchanger. The chiller heat exchanger places the liquid refrigerant from the condenser into a heat exchange relationship with a fluid, typically water, and undergoes a phase change to a refrigerant vapor as a result of the heat exchange relationship with the fluid, removing heat from the fluid, typically resulting in a reduction in fluid temperature. The cooled fluid then may be used for cooling applications, including the cooling of buildings. The vapor refrigerant in the chiller heat exchanger exits the chiller heat exchanger and returns to the compressor to complete the cycle. Chiller systems may also include multiple refrigerant circuits having independent refrigerant loops. Refrigerant in the refrigerant loops circulate through one or more compressors, condensers and evaporators, without combining refrigerant streams. Multiple refrigerant circuits may share single components, such as evaporators. When multiple refrigerant loops share a single component, the refrigerant streams remain independent of each other, but exchange heat with the same fluid. In chiller heat exchangers, multiple sets of tubes may be used to maintain independent refrigerant loops. The utilization of a single component in multiple circuit systems allows for increased efficiency of the system and reduction in space required for the chiller system. 
     FIG. 1  shows a known chiller heat exchanger for use with an HVAC system having flat plate headers  109  and  117 . The chiller heat exchanger shown in  FIG. 1  is a shell and tube heat exchanger having a shell  101 , which receives a fluid, typically water, through shell inlet line  103 . The water in the shell  101  enters into a heat exchange relationship with refrigerant passing through tubes arranged within the shell  101 . The water then exits the shell  101  through water outlet line  105 . Liquid refrigerant, typically from a condenser, is circulated to the chiller heat exchanger through refrigerant inlet line  107 . Refrigerant inlet line  107  delivers the liquid refrigerant to the first flat header  109 . The first flat header  109  comprises a head plate  111  and a baffle chamber  113 . The head plate  111  is a flat, relatively thick plate that provides containment for the refrigerant within the system. A gasket must be placed between the head plate  111  and the baffle chamber  113  in order to reduce leakage. The baffle chamber  113  contains one or more baffles that direct the flow of refrigerant into a first set of tubes  309  (see  FIG. 3 ) that are arranged in the shell  101  and substantially prevents the direct flow of refrigerant between the inlet and outlet. The head plate  111  and the baffle chamber  113  are fastened to a tubesheet  115  of shell  101  by fasteners  116 . A second gasket must be placed between the baffle chamber  113  and the tubesheet  115  in order to reduce leakage. The shell  101  includes a tubesheet  115  at each end of the shell  101  and provides openings into which refrigerant may pass and a flange to which the header may be attached. The return end of the shell  101  includes a second header  117 . Like the first flat header  109 , the second header  117  comprises a head plate  111  and baffle chamber  113 . Also like the first flat header  109 , the head plate  111  is a flat, relatively thick plate. Also like the first header  109 , the second flat header  117  requires at least two gaskets in order to reduce leakage. Center bolts  120  are also shown on the inlet/outlet and return heads. The liquid refrigerant from refrigerant inlet line  107  passes through the first flat header  109 , enters the tubes arranged within the shell  101  and travels to the second flat header  117 . Heat transfer between the refrigerant and heat transfer fluid takes place within the shell  101  and generally results in a mixed phase refrigerant, i.e., liquid and vaporous refrigerant. The refrigerant in the second flat header  117  then enters a second set of tubes  311  (see  FIG. 3 ), which flow back in a direction toward the first flat header  109 . The refrigerant continues to exchange heat with the fluid in the shell  101  and reenters the first flat header  109 . The refrigerant then exits the first flat header  109  through outlet line  119  substantially as a vapor. The baffle chamber  113  in each of the first flat header  109  and second flat header  117  may also include an arrangement that provides a number of passes of refrigerant across the shell that is greater than two. 
     FIG. 2  shows a chiller heat exchanger according to the present invention.  FIG. 2  has substantially the same arrangement of shell  101 , shell inlet line  103 , water outlet line  105 , tubesheet  115 , refrigerant inlet line  107  and refrigerant outlet line  119 , as shown and described with respect to  FIG. 1 . However, unlike  FIG. 1 ,  FIG. 2  includes a first header  201  and a second header  203  having a curved geometry, without the use of a baffle chamber  113  and with a single gasket between first header  201  and second header  203  and tubesheets  115 . The curved or dished heads are inexpensive and may be easily fabricated and eliminate the need for center bolts. The gasket may be fabricated from any suitable sealing device that provides sealing of the first and second headers  201  and  203  against the tubesheets  115 . Suitable materials include, but are not limited to neoprene or rubber. First header  201  and second header  203  are attached to shell  101  by fasteners  116 . Although  FIG. 2  shows bolts fastening the first and second headers  201  and  203  against the tubesheet, any suitable fastening means may be used, including welding, clamping or adhering the first and second headers  201  and  203  to the tubesheet  115 . The refrigerant inlet  108  and refrigerant outlet  119  pass through the curved portion of first header  201  and provides refrigerant to and takes refrigerant from the chiller heat exchanger. Although  FIG. 2  only shows one refrigerant inlet  107  and one refrigerant outlet  117 , the chiller heat exchanger may include multiple inlets and outlets, corresponding to multiple circuits. 
     FIG. 3  shows a cutaway view of the heat exchanger according to the present invention, as shown in  FIG. 2 . Shell  101  contains a plurality of tubes  301 , which fluidly connect inlet chamber  303  and outlet chamber  305  to return chamber  307 . The tubes  301  are divided into a first set of tubes  309  and a second set of tubes  311 . Inlet chamber  303  receives refrigerant, typically liquid refrigerant, from refrigerant inlet line  107 . Refrigerant inlet line  107  includes a refrigerant diffuser  306  that diffuses the flow of refrigerant and distributes the refrigerant across tubes  301  of the first set of tubes  309 . Although diffuser  306  has been shown as a plate that directs flow substantially perpendicular to the flow into the chiller heat exchanger, any configuration of diffuser  306  may be used so long as the flow of refrigerant is sufficiently diffused to maintain efficient operation of the chiller heat exchanger. The refrigerant in tubes  301  of the first set of tubes  309  flows from the inlet chamber  303  to the return chamber  307 . Also, a flow restrictor plate  801  (see  FIG. 8A ) may be included to assure high velocity and enhanced performance. The location of the restrictor plate can be adjusted to achieve the desired refrigerant flow rate and achieve improved efficiencies of operation. 
   As the refrigerant passes through the first set of tubes  309 , heat is exchanged between the refrigerant in tubes  301  and fluid present in the shell  101 . The fluid, typically water, in the shell flows into shell inlet  103 , enters into a heat exchange relationship with the refrigerant in tubes  301 , wherein the water is cooled, and exits through water outlet  105 . The shell inlet  103  and shell outlet  105  may be positioned in any configuration along the length of the shell  101  that provides efficient operation of the chiller heat exchanger. The cooled water leaving the chiller heat exchanger flows to a heat load, such as a building cooling system. Although the fluid in the shell has been described as including water, any suitable heat exchange fluid may be used within the shell  101 , including but not limited to brine or glycol solutions. The heat transfer typically involves heat passing from the water to the refrigerant and resulting in a phase change of the refrigerant from a liquid to a vapor. Refrigerant entering return chamber  307  preferably includes a mixture of vapor and liquid. The refrigerant in return header  307  is distributed across tubes  301  of the second set of tubes  311 . The refrigerant from the return chamber  307  flows in tubes  301  to outlet chamber  305 . A baffle  313  attached to first header  201  separates the inlet chamber  303  from outlet chamber  305 . Like in the first set of tubes  309 , the refrigerant exchanges heat with the fluid in the shell  101  and continues to change from a liquid to a vapor. The refrigerant in outlet header  305  is preferably a vapor. The refrigerant in outlet header  305  exits the chiller heat exchanger through outlet line  117 . From the chiller heat exchanger refrigerant outlet  117 , the refrigerant continues to circulate through the refrigerant loop. 
     FIGS. 4A and 4B  show cutaway views of first header  201  for attachment to a chiller heat exchanger for chiller systems having two refrigerant circuits. Header  201  shown in  FIGS. 4A and 4B  includes refrigerant inlet  107 , refrigerant outlet  117 , diffuser  306 , and baffle  313 , as shown and described with respect to  FIG. 3 .  FIG. 4A  shows a side view cross-section of first header  201 . Header  201  includes a flange portion  401  and a rounded wall portion  403 . The rounded wall portion  403  defines inlet chamber  303  and outlet chamber  305  when attached to a tubesheet  115  (see  FIG. 3 ). Baffle  313  divides the first header  201  into inlet chamber  303  and outlet chamber  305 .  FIGS. 4A and 4B  show a two refrigerant circuit system wherein one circuit corresponds to one of the refrigerant inlets  107  and one of the refrigerant outlets  117  and a second circuit corresponds to the other refrigerant inlet  107  and refrigerant outlet  117 .  FIG. 4B  shows a cutaway front view of first header  201 .  FIG. 4B  shows two refrigerant inlets  107  and two refrigerant outlets  117 . The refrigerant inlets  107  provide refrigerant to inlet chambers  303 . Inlet chambers  303  for each of the refrigerant circuits are divided by circuit divider  405 . Outlet chambers  305  for each of the refrigerant circuits are divided by circuit divider  405 . Circuit divider  405  extends from a first point  407  on the flange portion  401  to a second point  409  on the flange portion  401  and extends circumferentially along the rounded wall portion  403  to form a seal that substantially prevents leakage of refrigerant between the two circuits. 
     FIGS. 5A and 5B  show cutaway views of second header  203  for attachment to the opposite end of the chiller heat exchanger from the first header  201  by fasteners  116 .  FIG. 5A  shows a side view cross-section of second header  203 . Like first header  201 , second header  203  includes a flange portion  401  and a rounded wall portion  403 . The rounded wall portion  403  in  FIGS. 5A and 5B  defines return chamber  307  when attached to a tubesheet  115  (see  FIG. 3 ).  FIG. 5B  shows a cutaway front view of second header  203 .  FIG. 5B  shows two return chambers  307 , each corresponding to one of the two refrigerant circuits. Return chambers  307  for each of the refrigerant circuits are divided by circuit divider  405 . Circuit divider  405  extends from a first point  407  on the flange portion  401  to a second point  409  on the flange portion  401  and extends circumferentially along the rounded wall portion  403  to form a seal that substantially prevents leakage of refrigerant between the two circuits. 
     FIG. 6  shows a perspective view of first header  201  according to the present invention.  FIG. 6  includes refrigerant inlets  107 , refrigerant outlets  117 , flange portion  401 , diffuser  306 , baffle  313 , and circuit divider  405 , as shown and described in  FIGS. 3 ,  4 A and  4 B. The interior spaces of inlet chamber  303  and outlet chamber  305  are shown. Inlet chambers  303  and outlet chambers  305  are defined by the surfaces of the first header  201 , rounded wall portion  403 , the circuit divider  405 , baffle  313  and tubesheet  115  (see  FIG. 3 ) when first header  201  is attached to tubesheet  115  by fasteners  116 . A gasket  601  is disposed adjacent to the flange portion  401 , circuit divider  405  and baffle  313  in order to provide a seal when the first header is fastened to tubesheet  115 . The refrigerant inlets  107  and refrigerant outlets  117  extend into the interior spaces of inlets chamber  303  and outlet chambers  305 . The extension of the refrigerant inlets  107  and refrigerant outlets  117  permit refrigerant to flow into or from the tubes  301  with a desirable flow profile and maintain efficient operation of the heat exchanger. 
     FIG. 7  shows a perspective view of second header  203  according to the present invention.  FIG. 7  includes flange portion  401 , and circuit divider  405 , as shown and described in  FIGS. 3 ,  5 A and  5 B. The interior space of return chamber  307  is shown. Return chamber  307  is formed when second header  203  is fastened to tubesheet  115  (see  FIG. 3 ) by fasteners  116 . The return chamber is defined by the rounded wall portion  403 , circuit divider  405  and tubesheet  115  when the second header  203  is attached to tubesheet  115 . The geometry of return chamber  307 , including the rounded wall portion  403 , provides efficient flow of refrigerant through the heat exchanger wherein the refrigerant maintains a high velocity. 
     FIGS. 8A and 8B  show a cutaway view of an alternate embodiment according to the present invention.  FIG. 8A  shows a cutaway side view of first header  201  having inlet chamber  303 , and outlet chamber  305  as shown and described with respect to  FIG. 4A . However,  FIG. 8A  further includes a restrictor plate  801  that reduces the volume of the chambers  303  and  305 . Restrictor plate  801  is preferably attached to the rounded wall portion  403  and sealed to provide a predetermined volume within the chambers. Although  FIG. 8A  shows the restrictor plate  801  arranged vertically within the header across refrigerant inlet  107  and refrigerant outlet  117 , restrictor plate  801  may be arranged in any suitable configuration that provides control of the volume within the inlet and outlet chambers  303  and  305 . Restrictor plate  801  provides additional control of the velocity of the refrigerant through the chiller heat exchanger. In addition, the restrictor plate  801  provides the refrigerant inlet  107  and refrigerant outlet  117  with greater stability from the additional attachment point to the first header  201 . The restrictor plate  801  also provides a surface to which the diffuser  306  may be attached, providing for easier assembly of the first header  201 .  FIG. 8B  shows a cutaway front view of first header  201  having inlet chamber  303 , and outlet chamber  305  as shown and described with respect to  FIG. 4B .  FIG. 8B  includes a restrictor plate  801  reducing the volume of the chambers  303  and  305 . As shown in  FIG. 8B , the restrictor plate  801  is circumferentially attached to wall portion  403 . Although the restrictor plate is shown as a substantially flat plate, the restrictor plate may be any geometry that reduces the volume in inlet and outlet chambers  303  and  305 . For example, the restrictor plate  801  may also be a curved portion having a smaller radius of curvature than the first and second headers  201  and  203 , forming a chamber including at least one curved surface. Further, the restrictor plates  801  may be present in any combination of chambers, including one or more of the inlet chamber  303 , outlet chamber  305 , and return chamber  307 . In addition, refrigerant inlets  107  and refrigerant outlets  117  extend through the restrictor plate  801  and are likewise attached to restrictor plate  801 . The circuit divider  405  and baffle  313  are attached to and extend from the restrictor plate  801  to an extent that allows a seal when first header  201  is attached to a tubesheet  115  (see  FIG. 3 ). Although  FIGS. 8A and 8B  show the baffle and circuit divider  405  extending from the restrictor plate  801 , the baffle  313  and circuit divider may also extend through the restrictor plate  801  to the rounded wall portion  403 . 
     FIGS. 9A and 9B  show second header  203  according to an alternate embodiment of the invention.  FIG. 9A  shows a cutaway side view of second header  203  having return chamber  307 , as shown and described with respect to  FIG. 5A .  FIG. 9A  further includes a restrictor plate  801  that reduces the volume of the return chamber  307 .  FIG. 9B  shows a cutaway front view of second header  203  having return chamber  307 , as shown and described with respect to  FIG. 5B . The circuit divider  405  shown in  FIGS. 9A and 9B  is attached to and extends perpendicularly from the restrictor plate  801  to an extent that allows a seal when second header  203  is attached to a tubesheet  115  (see  FIG. 3 ). 
     FIG. 10  shows a perspective view of first header  201  according to an alternate embodiment of the invention.  FIG. 10  shows the arrangement of  FIG. 6  further comprising restrictor plate  801 . As shown and describe with respect to  FIGS. 8A and 8B , restrictor plate  801  is circumferentially attached to the wall portion  403 , reducing the volume of inlet chambers  303  and outlet chambers  305  when the first header  202  is attached to tubesheet  115 . The interior spaces of inlet chamber  303  and outlet chamber  305  are shown. Inlet chambers  303  and outlet chambers  305  are defined by the surfaces of the first header  201 , rounded wall portion  403 , circuit divider  405 , baffle  313 , tubesheet  115  (see  FIG. 3 ) and restrictor plate  801  when first header  201  is attached to tubesheet  115  by fasteners  116 . Like shown in  FIG. 6 , gasket  601  is disposed adjacent to the flange portion  401 , circuit divider  405  and baffle  313  in order to provide a seal when the first header is fastened to tubesheet  115 . The refrigerant inlets  107  and refrigerant outlets  117  extend into the interior spaces of inlet chambers  303  and outlet chambers  305  and are attached to the restrictor plate  801 . The extension of the refrigerant inlets  107  and refrigerant outlets  117  permit refrigerant to flow into the tubes  301  with a desirable flow profile and maintain efficient operation of the heat exchanger. 
     FIG. 11  shows a perspective view of second header  203  according to an alternate embodiment of the invention.  FIG. 11  shows the arrangement of  FIG. 7  further comprising restrictor plate  801 . As shown and describe with respect to  FIGS. 9A and 9B , restrictor plate  801  is circumferentially attached to the wall portion  403 , reducing the volume of return chamber  307  when the first header  202  is attached to tubesheet  115 . The interior space of return chamber  307  is shown. Return chamber  307  is formed when second header  203  is fastened to tubesheet  115  (see  FIG. 3 ) by fasteners  116 . The return chamber defined by the rounded wall portion  403 , circuit divider  405 , tubesheet  115  and restrictor plate  801  when the second header  203  is attached to tubesheet  115 . The geometry of return chamber  307 , including the rounded wall portion  403 , provides efficient flow of refrigerant through the heat exchanger wherein the refrigerant maintains a high velocity. 
   Although the invention has been shown and described with respect to two refrigerant circuits, any number of refrigerant circuits may be used. For example, two circuit dividers  405  may be attached to the rounded wall portion  403  to accommodate three circuits. Likewise, although the invention has been shown and described with respect to a two-pass system, baffles  313  and tubes  301  may be arranged into three or more passes. 
   While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.