Abstract:
A flow control system in an inlet duct to a heat exchanger includes a door having a first end and a second end opposite the first end. The first end rotates about an axis and the second end moves between an open position and a closed position to respectively allow and prevent flow into the heat exchanger. The second end has a rounded configuration. A plurality of mixing elements are downstream of the door. At least one mixing element has a base portion and a distal portion, and the base portion has a base width and the distal portion has a distal width. The base width is wider that the distal width.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to heat exchangers and, more particularly, to apparatus and methods of managing flow distribution into heat exchangers. 
         [0002]    Heat exchanger life is driven by strain ranges and their location within the heat exchanger. These strain ranges are a function of the temperature gradients present, both spatial and temporal, as well as the heat exchanger design. The flow distribution into the heat exchanger is one factor driving the strain ranges and their location. 
         [0003]    Current designs include a valve immediately upstream of the heat exchanger and which causes severe flow maldistribution. This, in turn, causes large spatial flow gradients, flow spikes locally that can exceed 10× uniform flow, and temporal flow gradients, as the valve opens and closes. The spatial gradients can also move to different locations on the heat exchanger entrance. 
         [0004]      FIG. 1  is a plan view of a current design of a heat exchanger  10  and duct/manifold  11 . A valve door  12  has a trailing edge  12   a  that, when nearly closed, allows a jetted flow  13  to enter the heat exchanger  10 . This trailing edge design can cause large spatial flow gradients. It can also cause temporal gradients when the valve door moves  12  from one position to another. A large vortex  14  can also exist behind the valve door  12  and which can starve areas of the heat exchanger inlet  10   a , such as in the area  15 .  FIG. 2  depicts, at the heat exchanger inlet, a flow distribution created by the design of  FIG. 1 . 
         [0005]    As can be seen, there is a need for improved apparatus and methods to control flow maldistribution into a heat exchanger. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect of the present invention, a flow control system in an inlet duct to a heat exchanger comprises a door having a first end and a second end opposite the first end; wherein the first end rotates about an axis; wherein the second end moves between an open position and a closed position to respectively allow and prevent flow into the heat exchanger; wherein the second end has a rounded configuration; a plurality of mixing elements downstream of the door; wherein at least one mixing element has a base portion and a distal portion; wherein the base portion has a base width and the distal portion has a distal width; and wherein the base width is wider that the distal width. 
         [0007]    In another aspect of the present invention, a flow control system in an inlet duct to a heat exchanger comprises a door having a downstream end where a flow in the inlet duct enters the heat exchanger wherein the downstream end moves between an open position and a closed position to respectively allow and prevent flow into the heat exchanger; wherein the downstream end has a smooth, rounded surface; wherein the downstream end decreases separation of the flow from the door; wherein the downstream end increases diffusion of the flow past the door; and a mixer downstream of the door; and wherein the mixer provides a non-lineally increasing flow area as the downstream end moves between the closed position and the open position. 
         [0008]    In yet another aspect of the present invention, a flow control system in an inlet duct to a heat exchanger comprises a door having a downstream end where a flow in the inlet duct enters the heat exchanger; wherein the downstream end moves between an open position and a closed position to respectively allow and prevent flow into the heat exchanger; a mixer downstream of the door; wherein the mixer has a plurality of mixer openings through which the flow passes; wherein at least one mixer opening has a base portion and a distal portion; wherein the at least one mixer opening: provides a continuous increase in flow area from the base portion to the distal portion; decreases temporal flow gradients when the door is near the closed position; and decreases spatial flow gradients at an inlet of the heat exchanger. 
         [0009]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a side view of a heat exchanger and duct/manifold according to a prior design; 
           [0011]      FIG. 2  depicts a flow distribution into a heat exchanger according to a prior design; 
           [0012]      FIG. 3  is a perspective external view of a flow control system according to an embodiment of the present invention; 
           [0013]      FIG. 3A  is a is a side internal view of a valve door of the flow control system of  FIG. 3 ; 
           [0014]      FIG. 3B  is a plane internal view of a mixer of the flow control system of  FIG. 3 ; 
           [0015]      FIGS. 4A-4D  depict alternate embodiments of a trailing edge of a valve door of a flow control system according to the present invention; 
           [0016]      FIGS. 5A-5E  depict alternate embodiments of a mixer of a flow control system according to the present invention; 
           [0017]      FIG. 6  is a front view of a mixer of a flow control system according to the present invention; 
           [0018]      FIG. 7  is a side view of a flow control system and flow distribution according to an embodiment of the present invention; 
           [0019]      FIG. 8  depicts a flow distribution into a heat exchanger according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0021]    Various inventive features are described below that can each be used independently of one another or in combination with other features. However, any single inventive feature may not address any of the problems discussed above or may only address one of the problems discussed above. Further, one or more of the problems discussed above may not be fully addressed by any of the features described below. 
         [0022]    Generally, the present invention provides a flow control system for a heat exchanger. The flow control system herein can be positioned in a duct leading to a heat exchanger, and include a rounded or non-sharp edge of a valve door and a mixer downstream of the valve door. 
         [0023]    The present invention can decrease or minimize spatial variation in the flow distribution entering the heat exchanger when the valve door, in the duct, is near its closed position. This decrease or minimization of spatial variation can be accomplished by the mixer, such as in the form of teeth, and the upstream valve door edge where the flow passes the valve door. 
         [0024]    Also, the present invention can decrease or minimize temporal gradients in flow distribution as the valve door opens and closes. This can be accomplished by shaping the mixer such that there is a continuous increase, such as a linear increase, in flow area as the valve door opens. 
         [0025]    By virtue of the mixer and rounded downstream edge of the valve door, the present invention can break up a large vortex that can otherwise exist downstream of or behind the valve door. A large vortex can amplify flow starved regions on the heat exchanger face when the valve door is near its closed position. Further, the downstream edge of the valve door of the present invention can increase or maximize a width of jetted flow when the door is in its near closed position. And, the present invention can decrease or minimize pressure drop when the valve door is in its full open position. 
         [0026]      FIG. 2  depicts a heat exchanger  20  with a duct or manifold  21  that can direct a flow of air to a heat exchanger inlet or face  20   a . A flow control system  22  of the present invention can be disposed in the duct  21 . The heat exchanger  20  and the duct  21  can be of any conventional design. 
         [0027]      FIG. 3A  depicts an interior view of the duct  21  with a flow  24  flowing therein. In this embodiment, the duct  21  can have an increasing cross sectional area from where the flow  24  enters the duct  21  and towards the heat exchanger face  20   a . The flow control system  22  may include a valve door  26  that may have a downstream end  26   a  and an upstream end  26   b . The downstream end  26   a  can be a portion of the valve door  26  about which the flow  24  can pass the door  26 . The upstream end  26   b  can be a portion of the valve door  26  about which the door  26  can move or pivot. 
         [0028]    The valve door  26  can pivot between an open position and a closed position. In an open position, the valve door  26  allows flow into the heat exchanger  20 . In a closed position, the valve door prevents flow into the heat exchanger. 
         [0029]    In  FIG. 3A , the valve door  26  is shown in a near closed position. In a closed position, the downstream end  26   a  of the valve door  26  can be in contact with an interior wall of the duct  21 . In an open position, the downstream end  26   a  of the valve door  26  can be disposed opposite to and interfaced with a mixer  23  of the flow control system  22 . 
         [0030]    In  FIG. 3B , the mixer  23 , in embodiments, may include a plurality of mixing elements  23   a  and/or mixing openings  23   b . In embodiments, each mixing element  23   a  may be disposed in an alternating arrangement with each mixing opening  23   b.    
         [0031]      FIGS. 4A-4D  depict some alternative embodiments of a valve door  26  and its downstream end  26   a . In general, the downstream end  26   a  has a non-sharp configuration, as distinguished from a square or rectangular configuration that has sharp corners. In embodiments, all or at least a portion of the downstream end  26   a  can have a rounded configuration or a smooth, rounded surface. 
         [0032]    In  FIG. 4A , the downstream end  26   a  includes a flat surface  26   e  in the same plane as an upstream surface  26   c  of the valve door  26 . A rounded surface  26   d  of the downstream end  26   a  is opposite to the flat surface  26   e  and extends to a plane of the downstream surface  26   f  of the valve door  26 . 
         [0033]    In  FIG. 4B , the downstream end  26   a  includes a flat surface  26   e  in the same plane as an upstream surface  26   c  of the valve door  26 . A rounded surface  26   d  of the downstream end  26   a  is opposite to the surface  26   e  and extends towards but not up to a downstream surface  26   f  of the valve door  26 . 
         [0034]    In  FIG. 4C , the downstream end  26   a  includes a flat surface  26   e  in the same plane as an upstream surface  26   c  of the valve door  26 . A rounded surface  26   d  of the downstream end  26   a , in combination with the flat surface  26   e , is in the form of a complete J-hook. 
         [0035]    In  FIG. 4D , the downstream edge  26   a  omits a flat surface in the same plane as an upstream surface  26   c  of the valve door  26 . A rounded surface  26   d  of the downstream end  26   a  is in the form of a partial J-hook. 
         [0036]      FIGS. 5A-5E  depict some alternative embodiments of mixer  23  which, for exemplary purposes, are in the form of alternating teeth and openings. In  FIGS. 5A-5E , the teeth and openings vary in shape, length, thickness, spacing, as well as gap between the valve door and mixer. 
         [0037]      FIG. 6  depicts a front elevational view of a mixer  23  according to an embodiment. The mixer  23  may have a distal section  23 - 1  and a base section  23 - 2 . In embodiments, the distal section  23 - 1  may represent a “top” section that interfaces the valve door  26  when it moves between a near closed position  28  and a partially open position  29 . The base section  23 - 2  may represent a “bottom” section that interfaces the valve door  26  when it moves between a closed position  27  and the near closed position  28 . 
         [0038]    In the embodiment of  FIG. 6 , one or more mixing elements  23   a  may have a distal portion  23   a - 1  and a base portion  23   a - 2 . One or more mixing openings  23   b  may have a distal portion  23   b - 1  and a base portion  23   a - 2 . In embodiments the distal portions  23   a - 1 ,  23   b - 1  of the mixing elements and openings may be positioned in the distal section  23 - 1  of the mixer, and/or the base portions  23   a - 2 ,  23   b - 2  of the mixing elements and openings may be positioned in the base section  23 - 2 . 
         [0039]    As shown in  FIG. 6 , one or more of the distal portions  23   a - 1  of the mixing elements may have a width which is less than a width of one or more of the base portions  23   a - 2  of the mixing elements. Likewise, one or more of the distal portions  23   b - 1  of the openings may have a width which is greater that a width of one or more of the base portions  23   b - 2  of the openings. 
         [0040]    Although  FIG. 6  depicts each mixing element  23   a  to be of the same configuration, the present invention includes different configurations for one or more mixing elements. Similarly, even though each mixing opening  23   b  is depicted to be of the same configuration, the present invention includes different configurations for one or more mixing openings. 
         [0041]    One or more of the mixing openings  23   b  can be defined by two opposing walls  23   c . The walls  23   c  may be non-parallel to one another and disposed, relative to one another at an angle  23   d  which can be less than 90°. The angle  23   d  may the same or different for each opening  23   b.    
         [0042]      FIG. 6  depicts valve door  26  position relative to the mixer  23  as the door moves between closed and partially open positions. When the valve door  26  is closed, its position can be denoted as position V 1 . In such position, there is zero flow area and no flow passes the door  26 . When the valve door  26  is in a near closed position, denoted as V 2 , there is a sub-flow area V 2 - a  in mixing opening  23   b  that is greater than zero to enable flow to pass the door  26 . When the valve door  26  is in a partially open position, denoted as V 3 , there is a sub-flow area V 3 - a  in mixing opening  23   b  and/or in the area above opening  23   b  that is greater than the flow area V 2 - a . Accordingly, the distal section  23 - 1  and/or the base section  23 - 2  of the mixer, and in particular, the one or more mixing openings  23   b , can provide a continuous, non-linearly (i.e., non-constant) increasing flow area (that includes sub-flow areas) as the door moves from a closed position to a partially open position. In other words, the flow area may be a non-linearly increasing flow area because the walls  23   c  are non-parallel to each other. Thus, as an example, the flow area may increase quadratically. In another example, as the downstream end of the door moves from a closed position to a partially open position, the flow area can increase according to the following equations: 
         [0000]      Area(theta)=0; for theta&lt;THETA1 
         [0000]      Area(theta)= K 1(theta−THETA1)+ K 2(theta−THETA1)̂2;
 
         [0000]      for theta&gt;THETA1;  K 1 and  K 2 constant 
         [0043]    Notwithstanding the foregoing, the present invention contemplates that one or more of the mixer openings provide a flow area other than a continuously increasing flow area. For example, one or more openings may provide a fixed flow area. 
         [0044]      FIG. 7  depicts a side view of the flow control system  22  including the mixer  23  and the downstream end  26   a  of the valve door. Upon the flow passing the door  26  and the mixer  23 , the flow enters the inlet or entrance  20   a  of the heat exchanger  20 . When comparing  FIG. 7  to  FIG. 1  (prior art), it can be seen that the jetted flow  13  in  FIG. 1  is decreased, minimized and/or eliminated in  FIG. 7 . Also, it can be seen that the vortex  14  in  FIG. 1  is decreased, minimized and/or eliminated in  FIG. 7 . And the spatial gradient  15  in  FIG. 1  is decreased, minimized and/or eliminated in  FIG. 7 . 
         [0045]      FIG. 8  depicts a flow distribution entering a heat exchanger when using the flow control system  22 . When comparing  FIG. 8  to  FIG. 2  (prior art), it can be seen that the high flow in  FIG. 1  is decreased, minimized and/or eliminated in  FIG. 8 . Also, it can be seen that the low flow in  FIG. 1  is decreased, minimized and/or eliminated in  FIG. 7 . And the large gradient in  FIG. 1  is decreased, minimized and/or eliminated in  FIG. 8 . 
         [0046]    Without intending to limit the scope of the present invention, embodiments, and in particular the downstream end, can decrease separation of the flow from the valve door, and can increase diffusion of the flow past the valve door. Further, embodiments, and in particular the mixer, can provide a continuous increase in flow area, decrease temporal flow gradients such as when the door is near a closed position, and decrease spatial flow gradients at the inlet of the heat exchanger. 
         [0047]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.