Abstract:
A multi-pass heat exchanger having a return manifold with a partition, a front wall, and a rear wall is provided. The partition separates the return manifold into a collection chamber and a distribution chamber. The front and rear walls define a fluid channel. The front wall has a plurality of perforations placing the fluid channel in separate fluid communication with the collection chamber and the distribution chamber.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present disclosure relates to multi-pass heat exchangers. More particularly, the present disclosure relates to a multi-pass heat exchanger having a distributing insert in the return manifold. 
         [0003]    2. Description of Prior Art 
         [0004]    Refrigeration systems are well known in the art and ubiquitous in such industries as food service, chemical, residential and commercial cooling, and automotive. On a larger scale, heat exchangers are required for office buildings and for residential purposes. Lack of efficiency is a great concern with such systems. 
         [0005]    Traditional refrigeration cycles, or air conditioners, include a compressor, a condenser, an expansion valve, an evaporator, and a refrigerant whose evaporation creates the cool temperature. In some refrigeration systems, the evaporator is a series of parallel narrow tubes, which provide parallel refrigerant paths. When the refrigerant passes through the expansion valve, a pressure and temperature drop occurs. 
         [0006]    In many refrigerant vapor compression systems, as the refrigerant passes through the expansion valve, a portion of the fluid expands to vapor. The resulting two-phase mixture can cause maldistribution in the evaporator, which is a common problem with heat exchangers that use parallel refrigerant paths, resulting in poor heat exchanger efficiency. For heat exchangers that have relatively few parallel refrigerant paths (typically 20 or less), even distribution of the two-phase fluid is achieved through a distribution device that individually feeds each parallel refrigerant path. However, for heat exchanges with many parallel refrigerant paths (typically more than 20), individual distribution to each parallel refrigerant path is often not practical. In most cases, a simple inlet header is used, which can lead to significant refrigerant maldistribution to the heat exchanger. Additionally, gravity and the increase in overall volume as the flow transitions from the expansion device to the inlet header also act to cause the liquid and vapor to separate. 
         [0007]    Previously, it has been proposed by U.S. Pat. No. 7,143,605 to include a distributor tube positioned within the inlet manifold to reduce maldistribution. While the distributor tube within the inlet manifold has proven to be helpful to reduce maldistribution, the maldistribution of the liquid-phase and vapor-phase within the heat exchanger remains problematic. 
         [0008]    Therefore, there exists a need for heat exchanger that overcome, alleviate, and/or mitigate one or more of the aforementioned and other deleterious effects of prior art heat exchangers. 
       SUMMARY OF THE INVENTION 
       [0009]    A multi-pass heat exchanger having a return manifold with a partition, a front wall, and a rear wall is provided. The partition separates the return manifold into a collection chamber and a distribution chamber. The front and rear walls define a fluid channel. The front wall has a plurality of perforations placing the fluid channel in separate fluid communication with the collection chamber and the distribution chamber. 
         [0010]    A multi-pass heat exchanger having an inlet manifold, a return manifold, a plurality of channels, and a distributing insert is provided. The inlet manifold has a first partition defining an inlet chamber and an outlet chamber. The return manifold has a second partition defining a collection chamber and a distributing chamber. The plurality of channels define a first fluid flow path between the inlet chamber and the collection chamber and a second fluid flow path between the distributing chamber and the outlet chamber. The distributing insert is within the return manifold. The distributing insert has a first plurality of perforations in fluid communication with the collecting chamber and a second plurality of perforations in fluid communication with the distributing chamber. 
         [0011]    The above-described and other features and advantages of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    These and other objects of the present disclosure will be more apparent from the following detailed description of the present disclosure, in conjunction with the accompanying drawings wherein: 
           [0013]      FIG. 1  is a sectional view of an exemplary embodiment of heat exchanger with a distributing insert tube according to the present disclosure; 
           [0014]      FIG. 2  is a sectional view of the heat exchanger of the present disclosure, taken along lines  2 - 2  of  FIG. 1 ; and 
           [0015]      FIG. 3  is a sectional view of an alternative exemplary embodiment of the heat exchanger of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Referring now to the figures and in particular to  FIGS. 1 and 2 , an exemplary embodiment of a heat exchanger according to the present disclosure is shown and is generally referred to by reference numeral  10 . Heat exchanger  10  is a parallel path heat exchanger and, advantageously, includes an insert  44  that collects, mixes, and distributes fluid within a return manifold of the heat exchanger. 
         [0017]    In the illustrated embodiment, heat exchanger  10  is a micro-channel heat exchanger. However, it is contemplated by the present disclosure for insert  44  to find equal use with any type of parallel path heat exchanger. 
         [0018]      FIG. 1  illustrates heat exchanger  10  divided into two passes, namely a first pass  12  and a second pass  14 . First pass  12  and second pass  14  are defined by a transition line  16  defined by partitions  18  and  20 . 
         [0019]    Partition  18 , which separates first pass  12  from second pass  14  in an inlet manifold  22 , extends the width of the entire inlet manifold  22 . The other ends of manifold  22  are sealed by endcaps  24  having ports (not shown) defined therein. Partition  18  prevents a fluid  26 , such as a refrigerant, from by passing first and second passes  12 ,  14  through inlet manifold  22 . 
         [0020]    Partition  20 , which separates first pass  12  from second pass  14  in a return manifold  40 , extends the width of the entire return manifold  40 . Partition  20  prevents fluid  26 , such as a refrigerant, from passing to second pass  14  through return manifold  40  unless it first passes through distributing insert  44 . 
         [0021]    Fluid  26  can be either a single or a two-phase refrigerant. Thus, fluid  26  traveling through heat exchanger  10  can be in either a vapor-phase or a liquid-phase when traversing through the exchanger. Fluid  26  is represented by an arrow, which indicates the direction of flow through heat exchanger  10 . 
         [0022]    Inlet manifold  22  receives fluid  26  flowing through an internal distributor  28 . Internal distributor  28  has a series of small orifices  30  that distribute fluid into an inlet chamber  32  of inlet manifold  22 . Several micro-channel tubes (tubes)  34 , which have an inlet end  36  and an outlet end  38 , define a fluid flow path extending from inlet manifold  22  to a return manifold  40 . Inlet end  36  is in fluid flow communication with inlet chamber  32  of inlet manifold  22 . Return end  38  is in fluid flow communication with a collection chamber  42  of return manifold  40 . 
         [0023]    First pass  12  is defined as the fluid path from inlet manifold  22  to collection chamber  42  of return manifold  40  through parallel tubes  34 . Second pass  14  is defined as the fluid path from a distributing chamber  48  of return manifold  40  to outlet chamber  56  of inlet manifold  22  through parallel tubes  50 . 
         [0024]    Fluid  26  is ideally evenly distributed within tubes  34  in first pass  12 . Each tube  34  is a very narrow tube, and heat exchanger  10  has several such tubes that comprise the main body of the heat exchanger that transport fluid  26  during evaporation. Tubes  34  are aligned parallel to one another, and while  FIG. 1  shows a two-pass configuration of a heat exchanger, a multi-pass heat exchanger having more than two passes could also be used. In a multi-pass heat exchanger having more than two passes, a second return manifold replaces outlet chamber  56 , and this second return manifold directs fluid to either an outlet manifold, or another return manifold for another pass. The number of return manifolds required is dependent on the number of passes. 
         [0025]    While  FIG. 1  shows insert  44  disposed in return manifold  40 , an insert  44  could also be located in outlet chamber  56  of inlet manifold  22  opposite partition  18 , particularly if outlet chamber  56  in inlet manifold  22  is to function as a return manifold for a third pass (not shown). 
         [0026]    Fluid  26  is transported through tubes  34  to collection chamber  42 . Collection chamber  42  collects fluid from first pass  12  of tubes  34  and passes the fluid to insert  44 . Insert  44  mixes and transports fluid  26  from first pass  12  to second pass  14 . Ideally, fluid  26  is a homogeneous mix of evaporated in a vapor-phase and a liquid-phase. Collecting and mixing fluid  26  in insert  44 , enables homogenous mixing of the fluid before progressing to second pass  14 . Insert  44  has a series of collecting and distributing perforations  46  disposed along insert  44  that direct fluid  26  into and out of distributing insert  44 . 
         [0027]    Perforations  46 - 1  are positioned in insert  44  in first pass  12 . Perforations  46 - 1  receive fluid  26  from collection chamber  42 . Fluid  26  entering insert  44  at perforations  46 - 1  exits insert  44  at perforations  46 - 2  on the second pass  14 . Fluid  26  exiting through perforations  46 - 2  in insert  44  enter distributing chamber  48  where fluid  26  then enters second pass  14 . 
         [0028]    Perforations  46  are preferably of variable size to effectively mix and distribute fluid  26  within insert  44  and distributing chamber  48 . Perforations  46  can have an opening dimension that can be uniform across insert  44 , or the opening dimension of the perforations can increase in size from first pass  12  to second pass  14 . For example, perforations  46  can increase in dimension further downstream of the fluid flow path can achieve a greater degree of fluid distribution. The increase in size of perforations  46  can be incremental or one can use another pattern to decide the perforation size. 
         [0029]    The size and positioning of perforations  46  can influence the degree that the pressure in the heat exchanger  10  is impacted. Thus, the total cross-section of all perforations  46  in insert  44  impacts the degree that pressure is effected in heat exchanger  10 . In an exemplary embodiment of the disclosed insert  44 , the perforations  46  are configured so that insert  44  does not cause a drop in pressure in heat exchanger  10 , or the pressure drop in insert  44  is minimal. To limit the impact on pressure in heat exchanger  10 , while still achieving adequate mixing and distribution of fluid  26 , the shape, number and positioning of perforations  46  can be adjusted. 
         [0030]    The size and positioning of perforations  46  can also influence the degree that fluid  26  is effectively distributed through heat exchanger  10 . In one embodiment, one perforation  46  can be associated with a number of tubes  34  or  50 . In some embodiments, one perforation  46 - 1  is associated with four to six tubes  34  and one perforation  46 - 2  is associated with four to six tubes  50 . In another aspect, one perforation  46 - 1  can be assigned to every tube  34  and one perforation  46 - 2  can be assigned to every tube  50 . 
         [0031]    Insert  44  in return manifold  40  permits the collection of fluid  26 , that after evaporation may contain a portion of vapor and liquid to be mixed prior to distribution to second pass  14 . The resulting two-phase mixture can cause maldistribution in the evaporator, which is a common problem with heat exchangers that use parallel refrigerant paths, resulting in poor heat exchanger efficiency. In mini-channel or micro-channel heat exchangers the concern is even greater because the flow of refrigerant is divided into many small tubes, where every tube and mini-channel is to receive just a small and equal fraction of the total refrigerant flow. 
         [0032]    Insert  44  provides a smaller chamber than return manifold  40  can provide, which increases turbulence of fluid  26  exiting the insert into chamber  48 . Additionally, perforations  46  also aid in mixing and distributing fluid  26  into chamber  48 . Turbulence in insert  44  is one factor that increases distribution and mixing of fluid  26  entering chamber  48 . Insert  44  positioned in either the return manifold  40  or an inlet manifold in between successive passes can greatly diminish maldistribution. 
         [0033]    After fluid  26  has been distributed through insert  44  and has passed transition line  16 , fluid  26  enters second pass  14 . Perforations  46 - 2  in insert  44  in second pass  14  enable fluid  26  to exit insert  44 . Fluid  26  leaving insert  44  enters chamber  48  in second pass  14  of return manifold  40 . Chamber  48  is an extension of return manifold  40 . 
         [0034]    After entering chamber  48 , fluid  26  enters tubes  50  in second pass  14 , which have an inlet end  52  and an outlet end  54 . Tubes  50  are similar to tubes  34  excluding the distinction that tubes  34  are in first pass  12 , and tubes  50  are in second pass  14 . 
         [0035]    Fluid  26  travels the length of tube  50  and exits outlet end  54  to enter outlet chamber  56 , where the fluid can continue on through several additional passes (not shown), or exit heat exchanger  10 . 
         [0036]    Referring to  FIG. 2 , a sectional view of the heat exchanger of  FIG. 1 , taken along lines  2 - 2  is shown. As shown, insert  44  can be a separate tube that is in manifold  40  that is generally D-shape, i.e., where insert  44  has an arched wall  58 - 2  and a flat wall  58 - 1 , although any other shape that is easily manufactured could be used that would permit flow of fluid  26 . Flat wall  58 - 1  has perforations  46 - 1  and  46 - 2  for collecting, receiving, mixing, and distributing fluid  26 . 
         [0037]    Insert  44  is shown in  FIG. 2  by way of example as being a separate component to heat exchanger  10 . However, it is also contemplated by the present disclosure for insert  44  to be integrally formed in return manifold  40 . For example, insert  44  integrally formed with manifold  40  is described with reference to  FIG. 3 . 
         [0038]    In the embodiment illustrated in  FIG. 3 , outer wall  58 - 2  of manifold  40  is combined with the outer wall of the manifold, while flat wall  58 - 1  is integrally formed with the outer wall. 
         [0039]    While the instant disclosure has been described with reference to one or more exemplary embodiments, 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 thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out the apparatus in present disclosure, but that the disclosed apparatus will include all embodiments falling within the scope of the disclosure.