Abstract:
The invention relates to a condensing heat exchanger comprising a condenser section containing a plurality of internal fins, on which water is condensed and a succeeding slurper section, in which the condensate is removed. The condenser section and the slurper section are connected by a capillary bridge comprising capillary spaces wherein the condensate formed on the fins is transported by means of capillary forces inside the slurper section.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This application claims the priority of European application 00114618.2, filed Jul. 7, 2001, the disclosure of which is expressly incorporated by reference herein.  
           [0002]    The invention relates to condensing heat exchangers, and more particularly to condensing heat exchangers employing both a condenser section and a slurper section.  
           [0003]    A condensing heat exchanger is a main component of air conditioning systems. It simultaneously cools and de-humidifies the air to be conditioned. During this process water condenses on the surface of the air side surface (air fins) of the condensing heat exchanger. The condensed water on the air fins has to be separated from the air stream. On earth this is generally done by the gravity forces. For space applications under the absence of gravity the condensed water is sucked off by applying underpressure.  
           [0004]    A prior art design principle (FIG. 1) already proven in several applications, e.g. in spacelab missions, is to add a so called slurper section  3  to the condenser section  1  of the condensing heat exchanger  16  from which the condensed water together with some air is sucked off through the slurpor holes  7  by applying underpressure. However, this design requires that the air flow velocity is high enough to push the condensed water out from the air fins against the capillary forces which tend to hold the water inside the air fins. In case of low air flow velocities and when the distance between neighbouring fins  2  is small a significant amount of water can accumulate inside the air fins and is released spontaneously. This could result in a poor water separation performance of the slurper section.  
           [0005]    The object of the present invention is to provide a condensing heat exchanger in which trapping of the condensate BA inside the condensing section can be decreased and a high water separation can be obtained.  
           [0006]    In accordance with the invention the condensing heat exchanger comprises a capillary bridge, which connects the condensing section and the slurper section of the condensing heat exchanger. The capillary bridge comprises capillary spaces wherein the condensate formed on the fins of the condenser section is transported inside the slurper section by means of capillary forces.  
           [0007]    In a preferred embodiment the capillary space is defined by an interstitial space which is formed by at least one plate arranged in proximity to a section of the internal surface of the slurper section. The water is pulled from the condensing section into the interstitial spaces between the plates and the surface of the slurper section by capillary forces and transported inside the slurper section. By applying, for example, reduced pressure the water together with an air stream penetrates through dedicated slurper holes through which it exits the slurper section.  
           [0008]    The plates can be attached to the surface of the slurper section by means of clamps or bolts. An advantage arising from the use of clamps or bolts for attaching the plates to the slurper section is that the capillary bridge is capable of being added to an existing hardware or being removed after assembly of the condensing heat exchanger.  
           [0009]    In another embodiment of the invention the capillary bridge is formed by a capillary fleece or mesh. The water is pulled by capillary forces from the air fins into the cavities of the fleece or mesh and then exits by applying e.g. reduced pressure together with an air stream through dedicated slurper holes.  
           [0010]    In the case of the capillary bridge comprising plates, the distance between the plates and the internal surface of the slurper section, which affects the capillary force, is adjusted by dedicated spacers. When using a fleece or a mesh as capillary bridge the fleece or mesh is directly applied on the internal surface of the slurper section without spacers. The plate, fleece or mesh can be attached by mechanical treatments e.g. solding or welding.  
           [0011]    In a further embodiment of the invention the surface of the condensing section is coated. Preferably a hydrophilic coating is used. Thus, the transport of the water condensed on the air fins toward the capillary bridge is supported. Other surface treatments, e.g. mechanical, thermal or chemical treatments, which result into a hydrophilic characteristic of the surface are possible.  
           [0012]    The condensing heat exchanger according to the invention can be used under microgravity conditions or under 1 and higher gravity conditions. In the case of using the condensing heat exchanger under micro-gravity conditions, e.g. space applications, the water is extracted from the air stream in the slurper section through applied underpressure. In this application the condensing heat exchanger can be used in any spatial orientation.  
           [0013]    When the condensate should be removed solely by gravity, for example, on earth, the condensing heat exchanger should be oriented in such a manner that the plates forming the capillary bridge are oriented parallel to the gravity force. The water sucked into the capillary bridge by capillary forces is pulled down to the bottom of the capillary bridge by gravity. At the bottom of the capillary bridge a water column is formed. If the height of the water column in the capillary bridge produces a hydrostatic pressure which is greater than the capillary pressure of the capillary bridge the water can leave the capillary bridge. In order not to block the water suction from the fins at the bottom of the condenser section the slurper section including the capillary bridge has to be extended below the bottom of the condensing heat exchanger. So it is guaranteed that the water can leave the slurper section by gravity forces without applying underpressure.  
           [0014]    The present invention is dedicated mainly to space application for use in manned spacecrafts. However, it can also be applied on earth to improve water separation performance of a condensing heat exchanger.  
           [0015]    Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The invention is described in more detail with reference to the accompanying drawings, in which  
         [0017]    [0017]FIG. 1 is a schematical illustration of a condensing heat exchanger according to the prior art,  
         [0018]    [0018]FIG. 2 is a cross sectional side view along the line X-X′ of the condensing heat exchanger of FIG. 1 with the additional capillary bridge according to a first embodiment of the invention,  
         [0019]    [0019]FIG. 3 is a perspective view showing the arrangement of the condensing heat exchanger according to a first embodiment of the invention,  
         [0020]    [0020]FIG. 4 is a cross sectional side view along the line X-X′ of the condensing heat exchanger of FIG. 1 with the additional capillary bridge according to a second embodiment of the invention, and  
         [0021]    [0021]FIG. 5 is a perspective view of a further embodiment of the condensing heat exchanger especially for use under  1  gravity conditions. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    [0022]FIG. 1 shows a 3D schematic illustration of a condensing heat exchanger  16  according to the prior art comprising a condenser section  1  and a succeeding slurper section  3 . The condensing section  1  comprises a stack of alternating air flow channels  4  and water channels  6 . In order to enlarge the internal surface of the condenser section  1  air fins  2  are arranged inside the air flow channels  4 . Inside the condenser section  1  the air passes the air fins  2  in parallel direction, whereas the coolant water  11  flows in the water channels  6  perpendicular to the air flow  10 . The slurper section  3  is adjacent to the condenser section  1  and comprises slurper channels  8  being an extension of the water channels  6  of the condenser section  1  but being separated from the water channel  6  by spacer bars  13 . In the slurper channel  8  slurper holes  7  are provided through which water from the air flow  10  can penetrate into the slurper channel  8  by applying an underpressure. The slurper flow  9  in the slurper channel  8  containing separated water and air is oriented parallel to the coolant water flow  11  in the condenser section  1 .  
         [0023]    [0023]FIG. 2 shows a first embodiment of the capillary bridge according to the invention. A plate  5  is arranged on either side of the air flow channel  4  to form a capillary bridge. The plates  5  are mounted in close proximity to the internal surface of the air flow channel  4  in the slurper section  3 . In the embodiment shown in FIG. 2 the plates  5  are arranged parallel to the internal surface of the air flow channel  4 . Further, the plates  5  are in direct contact with the ends of the air fins  2  of the condenser section  1 . The distance between the plates  5  and the surface of the slurper section  3  is adjusted by dedicated spacers  17 . These spacers  17  are e.g. integrated on the plates  5 . Over a slurper hole  7  the capillary bridge (i.e. the interstitial space between plate  5  and the surface of the air flow channel  4 ) is connected to a slurper channel  8  so that condensed water can be removed. The slurper holes  7  are preferably evenly spaced over the flow width inside the slurper section  3  (see FIG. 1) such that a homogeneous flow in the slurper section  3  can be achieved.  
         [0024]    [0024]FIG. 3 shows a perspective view of a condensing heat exchanger  16  according to a first embodiment of the invention. The air flow  10  in the air flow channel  4  and the slurper flow  9  in the slurper channel  8  are indicated. The plates  5  forming the capillary bridge are mounted in pairs on either side of each air flow channel  4  of the slurper section  3 . The distance between the plates  5  and the air flow channel  5  is maintained by spacers  17 . The spacers  17  and the plates  5  are attached to the surface of the air flow channel  4  by bolts  15 .  
         [0025]    [0025]FIG. 4 shows a second embodiment of the capillary bridge connecting the condensing section  1  and the slurper section  3  according to the invention. The capillary bridge comprises a mesh  12  which is attached on either side of the air flow channel  4  with no spacers between the mesh  12  and the internal surface of the air flow channel  4 . Further, the mesh  12  is in direct contact with the air fins  2  of the condenser section  1 . Thus, the condensed water of the air flow  10  in the condenser section  1  penetrates through the mesh  12  inside the slurper section  3  and towards the slurper holes  7  where the water exits the slurper section  3  through the slurper channel  8 .  
         [0026]    [0026]FIG. 5 shows another embodiment of the condensing heat exchanger according to the invention suitable for use especially under  1  gravity conditions. The condensing heat exchanger  16  comprising the condenser section  1  and the slurper section  3  including the capillary bridge is oriented such that the plate  5  of the capillary bridge is oriented parallel to the gravity force. The water sucked into the capillary bridge by capillary forces is pulled down to the bottom of the capillary bridge by gravity. At the bottom of the capillary bridge a water column is formed. If the height of the water column in the capillary bridge produces a hydrostatic pressure which is greater than the capillary pressure of the capillary bridge the water can leave the capillary bridge.  
         [0027]    In order not to block the water suction from the fins located at the bottom of the condenser section  1  the slurper section including the capillary bridge has to be extended below the bottom of the condensing heat exchanger. The minimum length of the extension  14  is the height of a water column required to establish a hydrostatic pressure greater than the capillary pressure of the capillary bridge, Thus, the length of the extension  14  varies with the distance between the surface of the air flow channel  4  and the plate  5 .  
         [0028]    The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.