Abstract:
A removal device for removing gas bubbles and/or dirt particles from a liquid in a conduit system includes a housing ( 12 ) with an entry ( 14 ) and an exit ( 16 ) and a inter space ( 18 ) which is defined by the housing ( 12 ), wherein in the inter space a number of plates ( 20 ) are provided which extend substantially transversally to a main flow direction ( 58 ), wherein the plates ( 20 ) define a main ongoing flow channel ( 22 ), and wherein the plate define branch flow channels ( 21 ) which end in at least one quiet zone ( 44;48 ), and wherein at least one plate ( 50 ) defines a merge flow channel for a merge flow which merges with the main flow ( 22 ) at a merge point which is located downstream.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/NL2010/050626, filed Sep. 27, 2010, which claims the benefit of Netherlands Application No. 2003551, filed Sep. 25, 2009, the contents of which is incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a removal device for micro-bubbles and dirt from a liquid in a conduit system. Removal devices are known. 
     PRIOR ART 
     In the prior art, various removal devices have been developed. EP0244881A1 discloses a removal device with flow channels 3 which are inclined, see FIG. 1 of EP0244881A1. The flow channels 3 are defined by longitudinal baffles 2 which are inclined. At the upper end and lower end of the flow channels 3, lateral baffles 11, 12 are provided which define quiet zones 8. 
     It was found that the flow in the removal device according to EP0244881A1 has a disadvantageous form. 
     U.S. Pat. No. 4,096,063 discloses a removal device with a flow channel with lateral baffles 3 which define quiet zones 5. As can be seen in FIG. 8 of U.S. Pat. No. 4,096,063, in use, eddies are created in the quiet zones 5 in which dirt can settle down. 
     The cross-section of the flow channels in U.S. Pat. No. 4,096,063 (when seen in the direction of flow) is elongate. The flow channels extend vertically when seen in cross-section, see FIG. 1 of U.S. Pat. No. 4,096,063. The quiet zones 5 are located on the left side and on the right side of the flow channels. It was found that the form of the flow channels is disadvantageous for the functioning of the removal device. 
     U.S. Pat. No. 4,895,652 also discloses a removal device with lateral baffles. The flow channels are (in cross section) rectangular and are provided at an angle α with the horizontal, see column 3, line 61 of U.S. Pat. No. 4,895,652. Lateral baffles 11 form quiet zones in the form of gutters 4, 5 which extend transverse to the direction of flow. In use, dirt particles collect in the lower gutters 4 and, due to the angle α at which the gutters 4, 5 extend, slide in a downwards direction. Gas particles collect in the gutters above and slide upwards due to the angle α of the gutters 4,5. One or more collection chambers are provided, see column 3, lines 7-8: “collecting chamber”. A removal device according to U.S. Pat. No. 4,895,652 is also called a “cross-flow separator”, i.e. a removal device with a cross-flow. 
     The device to U.S. Pat. No. 4,895,652 was found to have only a moderate performance in practice. 
     OBJECT OF THE INVENTION 
     It is an object of the invention to provide an improved removal device for micro-bubbles and/or dirt particles. 
     SUMMARY OF THE INVENTION 
     During research, it was found that the removal devices which are mentioned above have various disadvantages. The efficiency of removal of dirt and gas particles is lower than desired. Moreover, the resistance to flow is higher than desired. The velocity with which the liquid flows through the removal devices, is relatively high. 
     In the present invention, a reduction of the velocity has been achieved in another way. 
     The invention provides a removal device for removing gas bubbles and/or dirt particles from a liquid in a liquid conduit system, the removal device comprising a housing having an entry and an exit and an inner space which is defined by the housing, wherein in the inner space a number of plates are provided which extend substantially transverse to a main flow direction, wherein the plates define a main ongoing flow channel which extends between the entry and the exit, and wherein the plates define branch flow channels which branch off from the main channel, and which end in at least one quiet zone, and wherein at least one plate defines a return flow channel for a return flow which merges with the main flow at a downstream merge point. 
     Upon entry in the housing of the removal device, the main liquid flow is divided stepwise and is spread over a much larger surface area in the housing. This occurs in a forced way. The main flow can be divided directly after entry in the housing. 
     As a result of this, the velocity of the flow is reduced. The velocity of the liquid is reduced proportionally with the increase of the cross-sectional surface area. 
     In an embodiment, the removal device has a circular housing with a certain diameter, when seen from above. 
     A large exchange area is thereby created for the removal of micro-bubbles and dirt particles. 
     The main liquid flow is forced into a different form (i.e. flattened) by plates which are laterally placed with respect to the liquid flow in the housing of the removal device. The plates define interspaces between the plates. 
     With these plates, it is prevented that non-desired eddies are created in the quiet zones by the main liquid flow in a lower and upper region of the housing of the removal device. 
     A small portion of the main liquid flow is diverted through the quiet zones, between the laterally placed plates. In this way, it is achieved that the surface area of the flow is substantially increased, and that the velocity is substantially decreased. 
     In a different way than known from the mentioned prior art, multiple partial flows merge in the quiet zones. 
     In an embodiment of the invention, the controlled partial liquid flow has a forced trajectory. The trajectory is created by an endplate which is provided in front of the discharge opening in the housing of the removal device, which endplate has a constricted opening with respect to the main flow channel. Between this endplate and the housing of the removal device, a space is provided which is in liquid communication with the quiet zones via openings at the upper end and lower end of the space. The constricted opening in the endplate provides a limited drop of pressure in the main liquid flow during passage of the main liquid flow through the opening. 
     In use, the difference in pressure upstream and downstream of the endplate causes the diversion of the partial liquid flows (or branch flows) from the main flow in an upward and downward direction. 
     By providing the required dimensions to the constricted opening, the velocity of the partial liquid flows can be limited, in such a way that micro-bubbles and dirt particles are not carried with the flow. 
     In an embodiment, the plates which are oriented laterally to the main flow channel are provided with a curved edge, i.e. a baffle, with which the branch flow is curved into the branch flow channels. The necessity of providing a baffle for the liquid flow, and the degree of curvature of the baffle which is provided, is influenced by the velocity of the liquid, the constricted opening in the endplate and the viscosity of the liquid. 
     In a further embodiment, a curvature in the edges of the plates near the quiet zone in the direction of the liquid flow is provided, in such a way that the liquid is guided gradually and in a curved manner into the quiet zones and has less resistance. 
     The constricted opening can also be provided with a curvature in the direction of the liquid flow, which causes a better guiding of the liquid and a reduction of the resistance. Downstream of the constricted opening, the flow channel widens. In an embodiment, the widening of a flow channel is gradual, which reduces the loss of pressure. 
     In a further embodiment, the ends of the (guided) baffles are entirely or in part provided with a jagged or profiled rim, or with an irregular surface, with which a controlled torrent in the liquid is stimulated in order to prevent undesired vibrations at critical liquid velocities. In this way noise or possible damage to the installation is avoided. 
     The removal device can be provided in three variants: 
     1. a combined micro-bubbles and dirt removal device, i.e. as disclosed above. 
     2. a removal device for micro-bubbles, wherein only the upper part is provided in the housing according to the description above. The lower part of the removal device is not critical, as long as the forced division of the liquid flow according to the disclosed principle is maintained.
 
3. a dirt removal device, wherein only the lower part in the housing is provided according to the description above. The upper part of the removal device is not critical in this embodiment, as long as the forced division of the main liquid flow according to the disclosed principle is maintained.
 
     In an embodiment, the lateral plates form a row of lateral plates which are placed one after the other when viewed in the direction of the flow. This is a very efficient configuration which leads to a high removal efficiency. 
     In an embodiment, the lateral plates form an upper row and a lower row. 
     The invention further relates to the manufacturing of a removal device according to the present invention, comprising providing a housing with an entry and an exit, placing plate in the housing according the configuration of the present invention. 
     The invention further relates to a method for removing dirt and/or gas particles from a conduit system, a method comprising placing a removal device according to the present invention in a conduit and causing a flow of liquid through the removal device, wherein gas particles and/or dirt particles are removed. 
     Herein below, the invention is elucidated with reference to a non-limiting drawing. 
    
    
     
       LIST OF FIGURES 
         FIG. 1  shows a view of the removal device according to the invention. 
         FIG. 2  shows a cross-sectional side view of the removal device according to the invention in use. 
         FIG. 3  shows a substantially same view as  FIG. 1 , but as a transparent line drawing. 
         FIG. 4A  shows a schematic cross-section of the flow channel, taken in the middle of the housing according to the line A-A in  FIG. 2 . 
         FIG. 4B  shows a schematic cross-section of another embodiment of the flow channel, taken in the middle of the housing according to the line A-A in  FIG. 2 . 
         FIG. 5  schematically shows an embodiment with baffles. 
     
    
    
     Like reference numerals denote like parts. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a removal device  10  with a housing  12  an entry  14  and an exit  16 . The entry and the exit are configured to be connected to a conduit system, in such a way that the removal device is provided in-line with the conduit system. A typical conduit system for example is a warm water conduit system of a heating installation. 
     The housing  12  defines an inner space  18  with a certain volume. A number of plates  20  are provided in the housing  12 . The plates  20  extend substantially laterally to the direction of flow. In a different embodiment, the plates can also be provided at a slight angle to a transverse direction of flow. The plates  20  define spaces  21  between them. 
     The plates  20  define a main flow channel  22 . The plates  20  can be divided in two groups. A first group  38  of plates is provided above the main flow channel  22  and a second group  40  of plates is provided below the flow channel  22 . The main flow channel  22  extends in a straight line from the entry opening  24  in the housing  12  to a discharge opening  26  in the housing. The groups  38 ,  40  form rows. 
     The total surface area of the flow in the interspaces  21  plus the surface area of the main flow channel  22  is substantially larger than the surface area of the entry opening  24  and the discharge opening  26 . The surface area of the main flow channel  22  alone is also greater than the surface area of the entry opening and discharge opening. 
     The plates  20  extend transverse to the flow from a wall  12  on the left side of the housing, when seen in the direction of flow, to a wall  12  on the right side of the housing. 
     The plates  20  have a varying width  49  due to the—in top view—circular form of the housing  12 . In another form of the housing it is also possible that the plates  20  have a uniform width. 
     The plates  20  have an edge  28  on the side of the flow channel  22 . The edges  28  define entrances to the branch flow channels  21 . 
     In  FIG. 4A , the form of the main flow channel  22  is shown, which is substantially rectangular. The main flow channel  22  is delimited on the left and right side by the housing  12  of the removal device  10 . The housing  12  extends substantially vertically at this location. On the bottom side, the flow channel  22  is delimited by the ridges  28  of the lower plates  20 . The ridges  28  of the lower plates also form a substantially straight line and extend substantially horizontally. On the upper side, the flow channel  22  is delimited by the ridges  28  of the upper plates  20 . The ridges  28  of the upper plates also form a substantially straight line and extend horizontally. The flow channel has a substantially uniform width  37  and a substantially uniform height  31 . The flow channel  22  has a surface area A 2 . The flow channel  22  may also have a square form. The constricted opening  52  is substantially circular and has a diameter  39 . The diameter  39  results in a surface area A 2  of the opening  52  which is substantially smaller than the surface area A 1  of the flow channel  22 . 
     In  FIG. 4B , an alternative embodiment is shown. The edge  28  has a curved form. The plates  20  have a varying height  32 . When the flow channel  22  is seen in cross-section, the flow channel  22  has the form of an hourglass, wherein the hourglass extends horizontally. In the middle  31  the flow channel has a reduced height  33  in comparison with the heights on the height on the sides  35  of the flow channel  22 . 
     The plates  20  have an edge  30  which is remote from the flow channel. The edges  30  define exits of the branch flow channels  21 . The housing  12  has an upper side  34  and a lower side  36 . The upper group  38  of plates has an upper edge  30  which is provided at a distance  42  of the upper side  34  of the housing  12 . Due to the distance  42 , an upper quiet zone  44  (or bubble rising zone) is defined in an upper region of the housing. Analogous to this, the lower group  40  of plates has a lower edge  30  which is provided at a distance  46  of the lower side  36  of the housing  12 . This creates a lower quiet zone  48  (or settlement zone) in a lower region of the housing. The upper quiet zone  44  is defined by the side wall of the housing  12 , the upper wall  34  of the housing  12 , and the upper ridges  30  of the upper plates  20 . The lower quiet zone  48  is defined by the side wall of the housing  12 , the lower wall  36  of the housing  12 , and the lower ridges  30  of the lower plates  20 . 
     At the downstream side of the removal device  10 , a plate  50  (or endplate) is provided just in front of the discharge opening  26 , wherein the plate  50  has a constricted opening  52 . 
     In use, the constricted opening  52  acts like a Venturi opening and creates a build-up of pressure in the main flow channel  22  upstream of the constricted opening  52 . The plate  50  defines an opening  51  at the upper side thereof and an opening  53  of the lower side thereof between the plate  50  and the housing  12 . Between the plate  50  and the housing  1 , a small space  68  is provided. The openings  51 ,  53  provide liquid communication between the space  68  and the quiet zones  44 ,  48 . 
     At the upper side  34  of the removal device, an air removal valve  54  is provided which is known from the prior art. 
     At the lower side  36  of the removal device, a dirt discharge  56  is provided. Both at the upper side  34  as at the lower side  36 , tapering surfaces are provided which cause the gas bubbles to arrive at the valve  54  respectively cause the dirt particles to arrive at the discharge  56 . 
       FIG. 2  shows the removal device  10  in use. A liquid flow  58  enters the space  18  via the entry  14 . The liquid flow  58  flows through the main flow channel  22 . The flow in the main flow channel is substantially laminar. Branch flows  60  are diverted from the main flow  58  in an upwards and downwards direction. The branch flows  60  flows through the interspaces  21 , which act as branch flow channels  21 . The branch flows are also substantially laminar. The branch flows  60  at the upper side arrive in the upper quiet zone  44 . There, the upper branch flows  60  merge. The branch flows at the lower side arrive in the lower quiet zone  48 . Here, the branch flows  60  merge. In use, the velocity in the main flow channel  22  is lower than in the entry  14  and the velocity of the branch flows between plates  20  is even lower. 
     The branch flows  60  have a substantially lower velocity of flow than the velocity of the main flow  58  at the entry  14 , because the total surface area of the flow is much larger. Because of this, gas particles can rise and dirt particles can settle. 
     In the quiet zones  44 ,  48  the flows also have a much lower velocity than the main flow  58 . This also stimulates the rising of gas particles and the settling of dirt particles. 
     From the quiet zones  44 ,  48  return flows  64 ,  66  are created which flow around the end plate  50  and merge with the main flow at a merge point  68 . 
       FIG. 3  shows substantially the same figure as  FIG. 1 , but in a line drawing. 
       FIG. 5  shows an embodiment in which the plates  20  have a baffle form  29  which guide the flow into the branch channels  21 . The baffle form result in less turbulence in the branch channels, because the branch flows are created in a more gradual way. The edges  28  can be provided with notches, fins, raffles or other discontinuities  61  in order to prevent large eddies. 
     A skilled person will readily understand that the invention can be varied in multiple ways without departing from the scope of protection as is defined by the claims.