Abstract:
The invention relates to an absorption plate for a vehicle air-conditioner, through which a flow of absorbent fluid ( 110 ) passes, said fluid flowing along at least one exchange surface ( 130 ), the exothermic absorption of a coolant occurring through said at least one exchange surface ( 130 ) by increasing the concentration of the coolant in the absorbent fluid ( 110 ), the plate comprising, along said at least one exchange surface ( 130 ), a means ( 150 ) for rendering the temperature of the flow of absorbent fluid uniform, characterized in that the means ( 150 ) for rendering the temperature uniform is a separate turbulence means for said at least one exchange surface ( 130 ), and increases the turbulence of the flow of absorbent fluid ( 110 ) along said at least one exchange surface ( 130 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the US National Stage under 35 USC §371 of International Application No. PCT/2012/051060 filed May 14, 2012, which in turn, claims priority to French App. Nos. 1154624, 1154625, and 1154626 all of which were filed on May 27, 2011. 
     BACKGROUND 
     The present invention relates generally to an absorption plate for an air conditioner mounted on an automobile. 
     Devises for air conditioning by absorption are known in the prior art. For example, document FR 2 941 773 describes an air conditioner by absorption comprising absorption plates in which an absorbing fluid, lithium bromide, circulates and absorbs a refrigerating fluid, water vapor. On the other hand, this system has in particular the disadvantage of presenting an efficiency limited by the absorption capacities of the absorbing fluid in the refrigerating fluid. In fact, during the exothermic reaction of absorption on the surface, the absorbing fluid, lithium bromide, in contact with the refrigerating fluid, water vapor, heats up and the surface layer is rapidly saturated with refrigerating fluid. The absorption is limited by the transfer rate toward the center of the heat flow released and/or of the refrigerating fluid. The result is a rather weak total efficiency of the system because the transfer rate (of the heat released and of the refrigerating fluid absorbed) in the direction of the center of the flow of absorbing solution very strongly limits the absorption capacities during the traversing of the plate. 
     Moreover, the document U.S. Pat. No. 4,223,539 describes another type of air conditioner by absorption in which the absorbing fluid is sprayed onto refrigerating tubes where it flows out and absorbs the refrigerating fluid, and the surface of these tubes comprises protuberances creating a surface turbulence. Such an implementation is expensive because the process for manufacturing protuberances on the surface of a tube is not easy to carry out and its feasibility on an industrial scale has not been demonstrated. Furthermore, this implementation binds the protuberances to the surface on which the fluid is flowing and this makes any modification of the protuberances or of the surface difficult. This also complicates the supplying because the complexity of such a component limits the number of suppliers. Therefore, this implementation cannot be adapted to the automobile area, where flexibility and costs are parameters that direct the design. Finally, the bulkiness of such a system does not allow it to be integrated into a vehicle, when the geometric limitations of the vehicle are taken in to consideration. 
     SUMMARY 
     One goal is to provide an air conditioner by absorption that overcomes the disadvantages of the prior art documents cited above and in particular, first of all, to provide an air conditioner by absorption that has an elevated absorption yield without, however, requiring complex components for its implementation. 
     To this end a first aspect of the invention relates to an absorption plate for a vehicle air conditioner. 
     The plate improves the absorption efficiency of the absorbing fluid by homogenizing the flow along the exchange surface or grid. In other words, all along the flow, the temperature of the absorbing fluid and/or the concentration of the refrigerating fluid in the absorbing fluid tend to be homogenous in such a manner that there is little difference of temperature and of concentration between the surface layer and the zone in the center of the film. 
     These means of turbulence and/or of instability in accordance with this implementation are efficient for homogenizing the flow of absorbing fluid. They take advantage of characteristics of the flow for increasing its instability in order to cause turbulent currents that will homogenize the temperature of the flow of absorbing fluid and/or the concentration of refrigerating fluid in the flow of absorbing fluid. These means of turbulence and/or of instability do not make the plate excessively complex because they are distinct from the exchange surface, which is generally complex. The disclosed air conditioner by absorption allows for the possibility of standardizing the plates and of maintaining a manufacturing cost of interest while improving the absorption efficiency with distinct turbulence means. 
     The plate also improves the efficiency of the absorption by the absorbing fluid by bringing about at least a mixture of the flow along the exchange surface in order to render uniform the temperature and the concentration of refrigerating fluid. In other words, the surface layer is mixed with the rest of the absorbing fluid in such a manner that the surface layer downstream from the mixing/homogenizing means is not saturated with refrigerating fluid. As a consequence, the absorbing fluid downstream from the homogenization means can then reabsorb the refrigerating fluid efficiently. 
     A second aspect is a vehicle air conditioner comprising at least one absorption plate. 
     A further aspect is an automobile comprising at least one air conditioner having such an absorption plate. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Other characteristics and advantages of the present invention will appear more clearly upon a reading of the following detailed description of an embodiment of the invention given as a non-limiting example and illustrated by the attached drawings in which: 
         FIG. 1  shows an absorption plate in accordance with the prior art; 
         FIG. 2  shows an absorption plate in accordance with a first embodiment of the absorption plate; 
         FIG. 3  shows an absorption plate in accordance with a second embodiment of the absorption plate; 
         FIG. 4  shows an absorption plate in accordance with a third embodiment of the absorption plate; 
         FIG. 5  shows an absorption plate in accordance with a fourth embodiment of the absorption plate; 
         FIG. 6  shows an absorption plate in accordance with a fifth embodiment of the absorption plate; 
         FIG. 7  shows an absorption plate in accordance with a sixth embodiment of the absorption plate; 
         FIG. 8  shows an absorption plate in accordance with a seventh embodiment of the absorption plate; 
         FIG. 9  shows an absorption plate in accordance with an eighth embodiment of the absorption plate; 
         FIG. 10  shows the plate of  FIG. 9  in cross-section; 
         FIG. 11  shows an absorption plate in accordance with the ninth embodiment of the absorption plate viewed from the front; and 
         FIG. 12  shows the plate of  FIG. 11  in cross-section. 
     
    
    
     DESCRIPTION 
       FIG. 1  shows an absorption plate like those known in the prior art. Two exchange surfaces or grids  30  define a conduit into which a flow of absorbing fluid  10 , of lithium bromide, for example, circulates by gravity. A frame integrates the grids  30  and its upper part  20  comprises a feed hole through which the absorbing fluid enters between the two plates. The lower part  40  comprises, for its part, an exit hole connected to the rest of the absorbing fluid circuit. The flow between the two plates is substantially laminar, as the arrows between the grids  30  show. The plate is arranged in a reservoir containing a gaseous phase rich in refrigerating vapor. This can be water in the form of vapor, for example. 
     During the course of its trajectory between the two plates the lithium bromide absorbs the water through the grids  30  in their outer layer. The lithium bromide becomes loaded with water and its concentration of water of the saline solution of lithium bromide will increase as well as its temperature. The absorption capacity is limited by the transfer rate in the direction of the center of the flow of saline solution of the refrigerant absorbed on the surface of the saline solution and of the heat released. In the case of a flow of lithium bromide that is laminar or slightly unstable the heat released at the surface and the absorbed refrigerant diffuse very slowly in the direction of the center of the flow of saline solution. 
       FIG. 2  shows a first illustrative embodiment of a plate according to a in which two obstacles  150  are arranged in the flow of lithium bromide  110 . These obstacles form stop points for the fluid and downstream of each obstacle  150  eddies or vortices are caused in such a manner that the flowing out becomes unstable and a homogenization of the temperature and/or of the concentration of water in the lithium bromide is brought about. The outer layer of the flow is mixed in the rest of the flow and the temperature and/or the concentration in water of the lithium bromide is lowered in the zone in the proximity of the grid, which allows the efficiency of the absorption and of the air conditioner to be increased. The obstacles  150  are connected, for example, to the frame by a wire and their form can be varied (prismatic, spherical or even any one desired). 
       FIG. 3  shows a second illustrative embodiment whereby the obstacle  255  is arranged on a grid  230 . The presence of the obstacle  255  in the flow  210  establishes a stop point on the one hand and a variation of the section of the flowing out on the other hand. The result is an increasing of the instability of the flow and the flow&#39;s turbulence increases. 
     The streams of the initial flow become mixed and the temperature and/or the concentration in water of the lithium bromide becomes homogenized in such a manner that the efficiency of the absorption is improved. The obstacle  255  is advantageously fixed on the grid and on the frame and serves as reinforcement. This embodiment provides on the one hand an increase in the efficiency of the air conditioner and allows at the same time an increase in the rigidity of the plates. 
       FIG. 4  shows a third illustrative embodiment in which the refrigerant vapor is injected into the flow  310  in the form of bubbles. To this end a conduit  360  connected to a high-pressure refrigerant vapor zone is placed on a grid  330  and can inject bubbles  365  of refrigerant into the flow  310 . The refrigerant bubbles rise in the flow and their movement causes instabilities and turbulent eddies in the flow  310  of lithium bromide, causing a homogenization of the temperature and/or of the concentration in water of the lithium bromide. The conduit  360  advantageously serves as a reinforcement of the grid and allows the plate to be rigidified by being connected to the frame. Also, the injecting into the flow of lithium bromide of the vapor taken in the reservoir can be envisaged, which even further increases the efficiency of the system. 
       FIG. 5  shows a fourth illustrative embodiment. The flow  410  is heated locally by an electrical resistor placed on a grid  430 . The increase of local temperature of the saline solution of lithium bromide generates a force of floatability at the origin of an outflow opposed to the main flow  410 , which forces a homogenization of the temperature and/or of the concentration in water of the lithium bromide. The resistor  470  advantageously serves as a reinforcement to the grid and allows the plate to be rigidified by being connected to the frame. 
       FIG. 6  shows a fifth illustrative embodiment. Vibrators  580  are fixed to the grid  530  and put it in vibration. The flow in the area of the vibrators is consequently modified, which brings about an augmentation of its instability and the turbulence increases. 
     The streams of the bromide flow will then be mixed and the temperature and/or the concentration in water of the lithium bromide is homogenized. The efficiency is improved. The vibrators  580  advantageously serve as a reinforcement for the grid  530  and allow the plate to be rigidified by being connected to the frame. The vibrators  580  are arranged in a staggered configuration and vibrate in phase opposition. The flow in the area of the vibrators is therefore greatly modified and it is greatly heterogeneous all along the flow  510 . The homogenization is greatly improved with this particularly advantageous implementation. 
       FIG. 7  shows a sixth illustrative embodiment. A buffer reservoir  650  was inserted in the flow of the absorbing fluid  610 . Two vertical walls form a collector into which the grids directly discharge the flow of absorbing fluid. The buffer reservoir  650  temporarily stores the absorbing fluid before redirecting it between the grids  630 . The intermediate storage in the buffer reservoir has the effect of mixing the flow of absorbing fluid and the surface layer charged with absorbed water will be diluted in the rest of the flow in such a manner that downstream from the buffer reservoir  650  the surface layer has a concentration of water and/or a lower temperature than upstream from the buffer reservoir and presents an improved absorption capacity. At least two variants of the evacuation of the reservoir can be envisaged, to wit, distinct orifices that have the effect of maximizing the mixture of the absorbing fluid, or a slot that has the effect of maximizing the distribution of the absorbing fluid in the grids  630 . 
       FIG. 8  shows a seventh illustrative embodiment. Two blades  750  are arranged in the flow of the absorbing fluid and separate it into two secondary flows that are then reunited by two convergent blades  755  and that redistribute it between the two grids  730 . During these transformations of the flow by the blades  750  and  755  the absorbing fluid  710  is agitated and the surface layer is mixed into the rest of the flow of absorbing fluid  710 . The result is the uniformization of the temperature and of the concentration in water of the lithium bromide that allows it to absorb more water downstream from the blades  750  and  755 . 
       FIGS. 9 and 10  show an eighth illustrative embodiment of the plate, in which three injection tubes  850 ,  851  and  852  feed the main flow  810  of lithium bromide along the grid  830 . At the locations at which the secondary flows are injected, eddies are caused in such a manner that the flow becomes unstable and a homogenization of the temperature and/or the concentration in water of the lithium bromide is brought about. The external layer of the flow is mixed into the rest of the flow and the temperature and/or the concentration in water of the lithium bromide is lowered in the zone in the proximity of the grid  830 , which allows the efficiency of the absorption and of the air conditioning to be increased. The tubes  850 ,  851 ,  852  are, for example, at one quarter, one half and at three quarters of the height of the grid in order to bring about three regenerations of the flow of the absorbing fluid in order to maximize the efficiency. The injection tubes  850 ,  851 ,  852  are directly connected to the main feed chamber  825  in order to avoid adding a specific feed pump for lithium bromide for the secondary flows. 
       FIGS. 11 and 12  show a ninth illustrative embodiment of the plate in which the sidewalls  960  and  961  of the frame feed the main flow  910  of lithium bromide along the grid  930 . An agitation is brought about along the sidewalls  960  and  961  where the secondary flows are injected in such a manner that the flow becomes unstable and a homogenization of the temperature and/or of the concentration in water of the lithium bromide is brought about. The external layer of the flow mixes into the rest of the flow and the temperature and/or the concentration in water of the lithium bromide is lowered in the zone in the proximity of the grid, which allows the efficiency of the absorption and of the air conditioner to be increased. The side walls  960  and  961  are directly connected to the main feed chamber  925  in order to avoid adding a specific feed pump for lithium bromide for the secondary flows. 
     It is understood that various modifications and/or improvements obvious to the person skilled in the art can be added to the different embodiments of the plate described in the present specification without departing from the scope of the invention defined by the attached claims. In particular, the multiplying of the turbulence means on one and the same plate can be envisaged and their usage can also be mixed in order to perform several different implementations on one and the same plate. 
     In particular, reference is made to the integrating of a mixing device into the flow of absorbing fluid, but it can also be envisaged that several of them can be integrated at the same time. Finally, it is also possible to envisage implementing an overflow port in the buffer reservoir to prevent any overflow. 
     In particular, it can be envisaged that the injection orifices are multiplied on each injection tube in such a manner several regenerations of absorbing fluid are carried out along the same injection tube.