Abstract:
An heat exchanger assembly includes a plurality of tubes defining a plurality of parallel refrigerant passages therein carrying a refrigerant longitudinally from an inlet header to an outlet header. Water flows from a reservoir through a distributor apparatus to provide even wetting between the ends of the tubes as the water flows laterally over the tubes between an entry edge and an exit edge. A screen is provided adjacent the exit edge to collect excess water to be deposited into a water tray provided beneath and spaced from the exit edge of the tubes. A pump is provided to move water from the water tray to the reservoir to preserve water. If excess water is lost, such as through evaporation, a supplemental water feed line provides supplemental water to the system.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The subject invention relates to a heat exchanger assembly. 
         [0003]    2. Description of the Prior Art 
         [0004]    Conventional vapor compression air conditioning systems include an evaporator for transferring heat from ambient air to evaporate a refrigerant, a compressor for compressing the refrigerant into a superheated vapor, and a condenser to condense the refrigerant back to a subcooled liquid so that it can be provided back to the evaporator through an expansion device. Known condenser assemblies include a plurality of tubes extending longitudinally between an inlet end and an outlet end for carrying a refrigerant flowing between an inlet header and an outlet header. Most condenser assemblies are cooled by ambient air flowing on the outside of the tubes. Since the heat removal capacity of air is low, attempts have been made to improve the heat removal efficiency of the condenser by using liquid water as the cooling medium in conjunction with air. This improves the heat transfer rate considerably due to latent heat of evaporation of liquid water. 
         [0005]    One such heat exchanger is disclosed in WO 00/68628 to Phelps et al., which shows a hose connected to a water outlet that drips water over condenser fins. A controller is responsive to a sensed air temperature to shut off the water flow below a certain air temperature. The system is optimized by visually inspecting the condenser to see if there is excess or insufficient water near the bottom of the unit. However, there is no mechanism to ensure that the water uniformly wets the condenser surface. 
         [0006]    A similar heat exchanger is shown in U.S. Pat. No. 4,672,817 to Croce, which shows a condenser having a perforated copper tube to allow water to saturate a wicking material until it drips vertically down over an array of fins. A common disadvantage of the condensers of Croce and Phelps is that the water flows over the fins. 
       SUMMARY OF THE INVENTION AND ADVANTAGES 
       [0007]    The invention provides for such a heat exchanger including a distributor apparatus for distributing water between the ends of the tubes to flow laterally across the tubes from the entry edge to the exit edge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0009]      FIG. 1  is a schematic view of a heat exchanger in accordance with a first embodiment of the present invention; 
           [0010]      FIG. 2  is a schematic view of a heat exchanger in accordance with a second embodiment of the present invention; 
           [0011]      FIG. 3  is a perspective view of a heat exchanger in accordance with either embodiment of the present invention; 
           [0012]      FIG. 4  is a cross sectional view of a heat exchanger according to an aspect of the present invention; 
           [0013]      FIG. 5  is a cross sectional view of a heat exchanger according to a second aspect of the present invention; 
           [0014]      FIG. 6  is a perspective view of a heat exchanger tube according to a third aspect of the present invention; 
           [0015]      FIG. 7  is a perspective view of a heat exchanger tube according to a fourth aspect of the present invention; 
           [0016]      FIG. 8  is a perspective view of a heat exchanger tube according to a fifth aspect of the present invention; 
           [0017]      FIG. 9  is a flow chart showing the control logic for an electronic control according to the first exemplary embodiment of the present invention; and 
           [0018]      FIG. 10  is a flow chart showing the control logic for an electronic control according to the second exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a heat exchanger assembly  20  is generally indicated including a plurality of tubes  22  extending longitudinally between an inlet end and an outlet end, and a extending between a pair of headers  24 ,  26 . Referring generally to  FIGS. 1-3 , an inlet header  24  is in fluid communication with the inlet end of the tubes  22  for supplying a refrigerant to the tubes  22 , and an outlet header  26  is in fluid communication with the outlet end of the tubes  22  for receiving the refrigerant. Each of the tubes  22  has a cross section including a pair of sides extending laterally between an entry edge and an exit edge. A plurality of dividers  28  extend longitudinally between the ends and between the sides to define a plurality of parallel refrigerant passages extending within each tube  22 . The headers  24 ,  26  extend vertically between a bottom and a top and the tubes  22  extend horizontally between the headers  24 ,  26  such that the sides of adjacent tubes  22  face one another. The tubes  22  are vertically spaced from one another between a bottom tube  30  extending adjacent the bottoms of the headers  24 ,  26  and a top tube  32  extending adjacent the tops of the headers  24 ,  26 . 
         [0020]    Referring again to  FIGS. 1 and 2 , according to the exemplary embodiments, the tubes  22  receive superheated refrigerant from the inlet header  24  and provide subcooled refrigerant to the outlet header  26 . A blower  34  is provided immediately upstream from the entry edge of the tubes  22  to move air over the sides of the tubes  22  to cool the refrigerant. The entry edge of the tubes  22  is disposed immediately downstream of the blower  34 , and the exit edge is disposed remotely downstream from the blower  34 . A watering system provides a supply of water to wet each of the tubes  22 . The watering system includes a reservoir  36  for storing the supply of water, and a wicking coating extending along the sides of the tubes  22  for wicking water uniformly over the sides of the tubes  22 . Heat from the refrigerant evaporates the water into vapor, and the vapor is carried away by the blower  34 . A distributor apparatus distributes water between the ends of the tubes  22  to flow laterally across the tubes  22  from the entry edge to the exit edge. The distributor apparatus includes a pipe  38  leading from the reservoir  36  to a plurality of branches  40 , with each branch  40  leading to one of a plurality of manifolds  42  extending along the entry edges of each tube  22 . 
         [0021]    A screen  44  is provided adjacent the exit edge of the tubes  22  for collecting excess water flowing from each tube  22 , and a water tray  46  is provided below the screen  44  and spaced from the exit edge of the tubes  22  for receiving the excess water from the screen  44  and from the tubes  22 . A pump  48  is provided to move water from the water tray  46  to the reservoir  36 , and an electronic control  50  in communication with the pump  48  and the water tray  46  activates the pump  48  according to the volume of water in the water tray  46 . To accomplish this, the electronic control  50  includes a high level water tray sensor  52  positioned within the water tray  46  to activate the pump  48  in response to a high level of water in the water tray  46 . 
         [0022]    According to a first exemplary embodiment, shown specifically in  FIG. 1 , a supplemental water feed line  54  is provided to supply water from a supplemental source, such as a city water line, to the water tray  46 . A supplemental valve  56  within the supplemental water feed line  54  is in communication with the electronic control  50 , which includes a low level water tray sensor  58  and a low level reservoir sensor  60 . If the water level in both the water tray  46  and the reservoir  36  falls below a threshold value, the supplemental valve  56  is opened to allow water to flow from the supplemental source into the water tray  46 , as shown by the control logic of  FIG. 9 . The controller reads the level of the water tray  46 , represented as L 1 , and the level of the reservoir  36 , represented as L h  and compares the levels first to a desired setting in each respective container, represented as L s1  and L sh , respectively. If the sum of the levels of the water tray  46  and reservoir  36  is less than the sum of the respective desired settings, the supplemental valve  56  is opened. Additionally, the level of the water tray  46  is compared to the desired setting for the water tray  46 . If L 1  is greater than L s1 , pump  48  is activated to move water into the reservoir  36 . The pump  48  will stop when L h  is greater than L sh , or will alternatively stop when L 1  is less than L s1 . 
         [0023]    According to a second exemplary embodiment, shown specifically in  FIG. 2 , the supplemental water feed line  54  supplies water from the supplemental source directly into the reservoir  36 . The electronic control  50  communicates with the low level reservoir sensor  60  to activate the supplemental valve  56  in response to a low level of water in the reservoir  36 . If the water level in the reservoir  36  falls below a threshold value, the supplemental valve  56  is opened to allow water to flow from the supplemental source to the reservoir  36 , as shown in the control logic of  FIG. 10 . In this embodiment, only a water tray  46  sensor is used, represented again as L 1 , and desired setting for the water tray  46  is represented as L s1 . When L 1  is less than L s1 , the pump  48  will be stopped to prevent pumping all of the water out of the water tray  46 , and the supplemental valve  56  will be opened to refill the water tray  46 . Once L 1  becomes greater than L s1 , the pump  48  will be reactivated to fill the reservoir  36 , and the supplemental valve  56  will be closed. 
         [0024]    The water metering system distributes a specified flow rate of water from the reservoir  36  to the sides of the tubes  22 . According to the first exemplary embodiment shown in  FIG. 1 , the water metering system includes a metering valve  62  in the pipe  38  for adjustably controlling the flow rate of water from the reservoir  36  to the tubes  22 . The metering valve  62  of the present embodiment is a solenoid valve in communication with the electronic control  50 . The reservoir  36  of the present embodiment is positioned vertically above the top tube  32  so that gravity will draw the water from the reservoir  36  toward the tubes  22  when the metering valve  62  is opened. To initiate water flow from the reservoir  36 , a high level reservoir sensor  64  communicates with the electronic control  50  to activate the solenoid valve in response to a high level of water in the reservoir  36 . Once the valve has been opened, it remains open as long as the heat exchanger is operating so that the water flow is continuous. 
         [0025]    According to the second exemplary embodiment shown in  FIG. 2 , the reservoir  36  is positioned below or level with the tubes  22  of the heat exchanger. The water metering system includes a wicking material to draw water by capillary action from the reservoir  36  to the manifolds  42 . 
         [0026]    According to a first aspect of either embodiment, as shown in  FIGS. 1 and 2 , the sides of the tubes  22  slope downwardly from the entry edge to the exit edge. Each of the sides of the tubes  22  slope at the same angle so that the sides of the tubes  22  are parallel with each other. Alternatively, as shown in  FIG. 4 , the sides of the bottom tube  30  slope at a first angle and the sides of the top tube  32  slope at a last angle different from the first angle. Each tube  22  between the bottom tube  30  and the top tube  32  slopes at progressively increasing angles from the first angle to the last angle to promote more efficient wetting of the plurality of tubes  22 . 
         [0027]    According to a second aspect of either embodiment, as show in  FIG. 5 , the bottom tube  30  has a first distance between the entry edge and the exit edge and the top tube  32  has a last distance between the entry edge and the exit edge. The last distance is greater than the first distance and each of the tubes  22  between the bottom and top tubes  30 ,  32  have a progressively increasing distance between the entry edge and the exit edge from the first distance and less than the last distance. The varying distances allows the heat exchanger to be customized according to the local cooling load. 
         [0028]    According to a third aspect of either embodiment, as shown in  FIG. 6 , the sides of the tubes  22  have a profile having a flat shape between the ends. According to a fourth aspect, as shown in  FIG. 7 , the sides of the tubes  22  have a profile having an arced shape between the ends. According to a fifth aspect, as shown in  FIG. 8 , the sides of the tubes  22  have a profile having a ridged semi-circular shape extending between the entry and exit edges, the profile formed as a result of extruding the tubes  22  so that the refrigerant passages have a circular shape integrally formed with one another. 
         [0029]    While the invention has been described with reference to an exemplary 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.