Patent Publication Number: US-6698509-B2

Title: Heat exchangers with flow distributing orifice partitions

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to heat exchangers, and in particular, to heat exchangers involving gas/liquid, two-phase flow, such as in evaporators or condensers. 
     In heat exchangers involving two-phase, gas/liquid fluids, flow distribution inside the heat exchanger is a major problem when the two-phase flow passes through multiple channels which are all connected to common inlet and outlet manifolds, the gas and liquid have a tendency to flow through different channels at different rates due to the differential momentum and the changes in flow direction inside the heat exchanger. This causes uneven flow distribution for both the gas and the liquid, and this in turn directly affects the heat transfer performance, especially in the area close to the outlet where the liquid mass proportion is usually quite low. Any maldistribution of the liquid results in dry-out zones or hot zones. Also, if the liquid-rich areas or channels cannot evaporate all of the liquid, some of the liquid can exit from the heat exchanger. This often has deleterious effects on the system in which the heat exchanger is used. For example, in a refrigerant evaporator system, liquid exiting from the evaporator causes the flow control or expansion valve to close reducing the refrigerant mass flow. This reduces the total heat transfer of the evaporator. 
     In conventional designs for evaporators and condensers, the two-phase flow enters the inlet manifold in a direction usually perpendicular to the main heat transfer channels. Because the gas has much lower momentum, it is easier for it to change direction and pass through the first few channels, but the liquid tends to keep travelling to the end of the manifold due to its higher momentum. As a result, the last few channels usually have much higher liquid flow rates and lower gas flow rates than the first one. Several methods have been tried in the past to even out the flow distribution in evaporators. One of these is the use of an apertured inlet manifold as shown in U.S. Pat. No. 3,976,128 issued to Patel et al. Another approach is to divide the evaporator up into zones or smaller groupings of the flow channels connected together in series, such as is shown in U.S. Pat. No. 4,274,482 issued to Noriaki Sonoda. While these approaches tend to help a bit, the flow distribution is still not ideal and inefficient hot zones still result. 
     SUMMARY OF THE INVENTION 
     In the present invention, barriers or partitions are used in the inlet manifold to divide the heat exchanger into sections. The barriers have orifices to allow a predetermined proportion of the flow to pass through to subsequent sections, so that the flow in the sequential sections is maintained in parallel and more evenly distributed. 
     According to the invention, there is provided a heat exchanger comprising a first plurality of stacked, tube-like members having respective inlet and outlet distal end portions defining respective of inlet and outlet openings. All of the inlet openings are joined together so that the inlet distal end portions form a first inlet manifold, and all of the outlet openings are joined together so that the outlet distal end portions form a first outlet manifold. A second plurality of stacked, tube-like members is located adjacent to the first plurality of tube-like members. The second plurality of tube-like members also has inlet and outlet distal end portions defining respective inlet and outlet openings. All of the inlet openings are joined together so that the inlet distal end portions form a second inlet manifold and all of the outlet openings are joined together so that the outlet distal end portions form a second outlet manifolds. The second outlet manifold is joined to communicate with the first outlet manifold. The second inlet manifold is joined to communicate with the first inlet manifold. A barrier is located between the first and second inlet manifolds. The barrier defines an orifice to permit the portion only of the flow in the first inlet manifold to pass into the second inlet manifold. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is an elevational view of a preferred embodiment of a heat exchanger according to the present invention; 
     FIG. 2 is a top or plan view of the heat exchanger shown in FIG. 1; 
     FIG. 3 is a left end view of the heat exchanger shown in FIG. 1; 
     FIG. 4 is an enlarged elevational view of one of the main core plates used to make the heat exchanger of FIG. 1; 
     FIG. 5 is a left side or edge view of the plate shown in FIG. 4; 
     FIG. 6 is an enlarged sectional view taken along lines  6 — 6  of FIG. 4; 
     FIG. 7 is a plan view of one type of barrier or partition shim plate used in the heat exchanger shown in FIGS. 1 to  3 ; 
     FIG. 8 is an enlarged sectional view taken along lines  8 — 8  of FIG. 7; 
     FIG. 9 is a left end view of the barrier plate shown in FIG. 7; 
     FIG. 10 is a front or elevational view of the barrier plate shown in FIG. 7; 
     FIG. 11 is a plan view, similar to FIG. 7, but showing another type of barrier or partition plate used in the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 12 is plan view, similar to FIGS. 7 and 11, but showing yet another type of barrier or partition plate used in the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 13 is an elevational view, similar to FIG. 4, but showing another type of core plate used in the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 14 is an elevational view similar to FIGS. 4 and 13, but showing yet another type of core plate used in the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 15 is an enlarged sectional view taken along lines  15 — 15  of FIG. 14; 
     FIG. 16 is an elevational view similar to FIGS. 4,  13  and  14 , but showing yet another type of core plate used in the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 17 is an enlarged scrap view of the area indicated by circle  5  in FIG. 16, but showing a modification to the location of the orifice; 
     FIG. 18 is a scrap view similar to FIG. 17 but showing yet another modification to the flow orifice; 
     FIG. 19 is a scrap view similar to FIGS. 17 and 18 but showing yet another modification to the flow orifice; 
     FIG. 20 is a scrap view similar to FIGS. 17 to  19  but showing yet another modification to the flow orifice; 
     FIG. 21 is a diagrammatic perspective view taken from the front and from the right side showing the flow path inside the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 22 is a perspective view similar to FIG. 21, but taken from the rear and from the left side of the heat exchanger of FIGS. 1 to  3 ; 
     FIG. 23 is a perspective view similar to FIGS. 21 and 22, but illustrating the flow path in another preferred embodiment of the present invention; 
     FIG. 24 is a scrap view similar to FIG. 17, but showing a portion of one of the core plates that is used in the embodiment of FIG. 23; 
     FIG. 25 is a scrap view similar to FIG. 24 but showing a modified type of orifice; 
     FIG. 26 is a scrap view similar to FIGS. 24 and 25, but showing yet another modification to the orifice; 
     FIG. 27 is a scrap view similar to FIGS. 24 to  26 , but showing yet another modification to the orifice; and 
     FIG. 28 is an elevational view of a core plate that is used in another preferred embodiment of the invention where the inlet and outlet manifolds are located at opposed ends of the core plate, rather than being adjacent as in the embodiments shown in FIGS. 1 to  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring firstly to FIGS. 1 to  6 , a preferred embodiment of the present invention is made up of a plurality of plate pairs  20  formed of back-to-back plates  14  of the type shown in FIGS. 4 to  6 . These are stacked, tube-like members having enlarged distal end portions or bosses  22 ,  26  having inlet  24  and outlet  30  openings, so that the flow travels in a U-shaped path through the plate pairs  20 . Each plate  14  preferably includes a plurality of evenly spaced dimples  6  projecting into the flow channel created by each plate pair  20 . Preferably, fins  8  are located between adjacent plate pairs. The bosses  22  on one side of the plate are joined together to form an inlet manifold  32  and the bosses  26  on the other side of the plates are joined together to form an outlet manifold  34 . As seen best in FIG. 2, a longitudinal tube  15  passes into the inlet manifold openings  24  in the plates to deliver the incoming fluid, such as a two-phase, gas/liquid mixture of refrigerant, to the right hand section of the heat exchanger  10 . FIG. 3 shows end plate  35  with an end fitting  37  having openings  39 ,  41  in communication with the inlet manifold  32  and outlet manifold  34 , respectively. 
     The heat exchanger  10  is divided into plate pair sections A, B, C, D, E by placing barrier or partition plates  7 ,  11 ,  12 , such as are shown in FIGS. 7 to  12 , between selected plate pairs in the heat exchanger. The inlet and outlet manifolds formed in the plate pairs of each section may be considered separate manifolds from each other, the inlet manifolds of adjacent sections being joined to communicate with one another and the outlet manifolds of adjacent sections being joined to communicate with one another. For example the inlet manifold  32  of section C is joined to communicate with the inlet manifold of section D and the outlet manifold of section C is joined to communicate with the outlet manifold of section D. Referring to FIGS. 21 and 22, sections are shown schematically, and the dividing walls represent actual barrier plates  7 ,  11 , and  12  as shown in FIGS. 7,  11  and  12 . As shown in FIGS. 7 to  12 , each barrier may have an end flange or flanges  42  positioned such that the barrier plates can be distinguished from one another when positioned in the heat exchanger. For example barrier plate  7  has two end flanges  42 , barrier plate  11  has a lower positioned end flange  42  and barrier plate  12  has an upper positioned end flange  42 . The direction of flow is indicated with arrows. Referring again to FIGS. 21 and 22, an inlet tube  15  delivers the fluid through an inlet  18  to the right hand section A of the heat exchanger where it would travel down along the back, or along the right hand side of the plates  14  as seen in FIG. 4, cross over and travel up the front, or along the left hand side of the plates as seen in FIG.  4 . Barrier plates  7 ,  12  each include an opening  70  to accommodate the inlet tube  15 . The flow then passes through a left hand hole  36  of barrier  7 , traveling down along the font of the next section B of plates, across and up the back of these plates to pass through a hole  38  in barrier plate  11  (see FIG. 11) which surrounds tube  15 . 
     Most of the flow then travels down the backside add up the front of the next section C of the heat exchanger plates and passes out via the outlet manifold through an outlet hole  40 , which is the left hand hole of the barrier plate  12  shown in FIG.  12  through to the outlet manifold of section D. However, some of the flow passes via the inlet manifold of section C through a small orifice  17  (see FIG. 12) and into the inlet manifold of the next section D of core plates. In this next section D, flow again travels down the back and up the front and out through the outlet hole  40  in the next barrier  12 . Again some of the flow goes through the inlet manifold through an orifice  17  into the inlet manifold of yet another section E of core plates. In this last section E of core plates, the flow goes down the back, up the front and finally out of the heat exchanger outlet  58 . 
     Referring again to FIG. 21, it will be appreciated that in the first two sections of core plates from the right A, B the fluid is flowing in series through these sections. However, when the fluid reaches the third section C, most of it travels in the U-shaped direction, but some of it is passed via the inlet manifold through the small orifices  17  in plates  12 , to the next section&#39;s inlet manifold so that the flow in the last three sections of core plates is in parallel. This parallel flow produces proportional, even flow distribution to balance the flow rate among all of the sections in the heat exchanger. 
     Rather than using the core plates of FIG.  4  and the barrier or partition plates of FIGS. 7 to  12 , the partitions of FIGS. 7 to  12  could actually be built right in or made an integral part of the core plates  50 ,  52 ,  54  as shown in FIGS. 13 to  16 . Core plate  50  as shown in FIG. 13 is equivalent to core plate  14  of FIG. 4 with a barrier plate  7  of FIG. 7 in that it has outlet opening  30  but inlet opening  24  includes an integral barrier  60  with a hole  70  therethrough to accomodate tube  15 . Core plate  52  of FIG. 14 is equivalent to core plate  14  of FIG. 4 with a barrier plate  11  of FIG. 11 in that outlet opening  30  is blocked by an integral barrier  62  and inlet opening  24  is not blocked. Core plate  54  of FIG. 16 is equivalent to core plate  14  of FIG. 4 with a barrier or partition plate  12  of FIG. 12 in that inlet opening  24  is blocked by an integral barrier  64  having a hole  70  to accommodate tube  15  and an orifice  17  thereby allowing a portion of flow to pass through the inlet manifold to the next section. It will be appreciated that the core plates of FIG.  13  and FIG. 14 would be used in the FIG. 21 embodiment in the location of the respective partitions  7  and  11 . The core plate shown in FIG. 16 would be used where the partitions  12  are indicated in FIG.  21 . 
     FIGS. 17 to  20  show different configurations of orifices  17  in core plates that would be used in the location of barriers  12  in the embodiment of FIG.  21 . The different orifices  17  are used to balance the flow rates amongst all of the sections in the manifold. The flow rates can be controlled by adjusting the sizes or locations (top or bottom) or the shapes of the orifices, such as round, vertical slot, horizontal slot or any other configuration. The location of the orifice high or low on the partition or core plate can be used to adjust the proportion of liquid to gas phase within the flow that is passed through the orifice, while the size of the hole is used more to adjust the overall mass flow rate. The sensitivities of the orifice size and location will tend to be application-specific, depending on how well mixed the two phases of the flow are at the point of flow splitting. Also, rather than one orifice hole, several smaller holes would be used. Further, the orifice in the first partition plate could be larger, or there could be more orifices, than in the second or down stream partition or barrier (see FIGS.  21  and  22 ). 
     In the embodiment represented by FIG. 23, it will be noted that there is no longitudinal inlet tube. The flow as indicated with arrows enters the left side of the heat exchanger, travels in series through the first two sections, and then in parallel through the last three sections in a manner similar to that of the embodiment of FIGS. 21 and 22. In this FIG. 23 embodiment, it will also be noted that the inlet  18  and outlet  58  are at opposite ends of the heat exchanger, rather than being adjacent as in the embodiment of FIGS. 21 and 22. In the embodiment of FIG. 23, the core plates would not have holes to accommodate a longitudinal inlet tube, as indicated in FIGS. 24 to  27 . Similar modifications will be made to the barrier or partition plates  7 ,  11 ,  12  of FIGS. 7 and 12, if such barriers are used with the core plates  14  of FIG. 4 to make a heat exchanger as indicated in FIG.  23 . 
     As mentioned above, the flow through the core plates travels in a U-shaped path in the embodiments of FIGS. 1 to  27 . However, this U-shaped path could be, in effect, straightened out, in which case core plates  56  as shown in FIG. 28 would be used. 
     As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. The foregoing description is of the preferred embodiments and is by way of example only, and is not to limit the scope of the invention.