Patent Publication Number: US-2011067427-A1

Title: Air Conditioning Device For Heating, Ventilation and/or Air Conditioning Installation

Description:
The invention relates to an air conditioning circuit for a heating, ventilation and/or air conditioning installation. 
     Motor vehicles are routinely equipped with a heating, ventilation and/or air conditioning installation to modify the aerothermal parameters of an air flow diffused inside the vehicle interior. 
     The heating, ventilation and/or air conditioning installation also comprises an air conditioning circuit with a coolant circulating therein. The coolant is, for example, a hydrofluorocarbon, particularly the coolant known under the reference R134a, or a hydrofluoro-olefin-based compound, particularly the coolant known under the reference HFO1234yf. The present invention is also applicable with any coolants equivalent to those mentioned above. The present invention is also applicable with supercritical fluids, particularly carbon dioxide. 
     The air conditioning circuit particularly comprises an external heat exchanger, particularly positioned at the front of the vehicle, for exchanging heat with an air flow external to the vehicle. The external heat exchanger is traversed by the external air flow but is not in contact with the air flow to be diffused in the vehicle interior. 
     The external heat exchanger is a heat exchange device extracting heat from the external air flow passing therethrough. However, the efficiency of the external heat exchanger is particularly degraded due to the formation of frost on the inserts arranged in the air flow passage on passing through the external heat exchanger. Frosting may appear when water vapor, present in the surrounding ambient air flow and passing through the external heat exchanger, condenses on the external surfaces of the external heat exchanger and freezes. While slight frost formation is not detrimental to heat exchanges on the external heat exchanger, an accumulation of frost is, on the other hand, particularly harmful and may result in the complete blockage of the external air flow passage via the external heat exchanger. Such frosting induces impaired air conditioning circuit performance. 
     As a result, air conditioning circuits must be fitted, almost systematically, with an effective external heat exchanger defrosting system. To solve the defrosting problem, a number of solutions have been proposed. 
     A first well-known method is that operating on the basis of “thermodynamic cycle inversion”. If defrosting is required, the role of the external heat exchanger is reversed and, as it operates as a gas condenser or cooler, the heat released during the defrosting phase on the external heat exchanger melts the frost. 
     A second method is that operating on the basis of “hot gas bypassing”. When the need for defrosting is detected, opening a bypass valve enables the compressor to discharge the coolant directly, particularly in the form of “hot” gases, into the external heat exchanger, bypassing part of the air conditioning circuit. The advantages of this method lie in the simplicity of the embodiment of the air conditioning circuit, the lack of heat extraction at the heat source and, in sum, a relatively low energy cost. 
     However, such a method only provides a low air conditioning circuit defrosting power and, in some designs, inefficiency. Document US 2007/0137228 discloses such a system and envisages an air conditioning circuit suitable for defrosting at a low ambient temperature. However, the drawback of the device described in this document is a loss of heating capacity during defrosting. 
     One aim of the invention is thus that of remedying the abovementioned drawbacks. It thus relates to an air conditioning circuit for a heating, ventilation and/or air conditioning installation. More specifically, the invention relates to an air conditioning circuit for a heating, ventilation and/or air conditioning installation, particularly a motor vehicle interior, comprising at least, according to the direction of closed circuit coolant circulation, a compressor, a first heat exchanger, suitable for heating an air flow to be distributed in the vehicle interior, a first expansion member, an external heat exchanger and a second heat exchanger, suitable for dehumidifying and/or cooling the air flow to be distributed in the vehicle interior. The air conditioning circuit comprises a storage device connected to the outlet of the first heat exchanger, to be able to store the calories from the first heat exchanger in the storage device with a maximum capacity, and connected to the outlet of the heat exchanger, to redistribute the calories via the coolant in the second heat exchanger to defrost same and/or restore the stored energy. 
     It is thus possible to defrost or limit the frosting of the external heat exchanger and/or the second heat exchanger by means of the storage device. Indeed, the temperature of the storage device is maintained by the air conditioning circuit while ensuring maximum energy performance. Subsequently, the calories stored are used to defrost the external heat exchanger and/or second heat exchanger by limiting the drop in the air conditioning circuit performance. 
     According to one example of an embodiment, the air conditioning circuit comprises a first bypass arm arranged in parallel with the first expansion member. 
     Advantageously, the air conditioning circuit comprises a first switching means arranged at the outlet of the first heat exchanger, to control the circulation of the coolant through the storage device. Preferentially, the first switching means is a first “three-way” valve or a first intermediate heat transfer fluid/coolant heat exchanger. 
     Alternatively or additionally, the air conditioning circuit comprises a second switching means arranged at the outlet of the external heat exchanger, to control the circulation of the coolant through the storage device or in a bypass arm of the storage device, referred to as the second bypass arm, particularly when the use of the storage device is not intended to favor energy restoration or further cooling of the coolant at the outlet of the external heat exchanger operating as a condenser. 
     Preferentially, the second switching means is a second “three-way” valve or a second intermediate heat transfer fluid/coolant heat exchanger. Particularly advantageously, the second bypass arm of the storage device is connected to the second “three-way” valve. 
     Moreover, the second intermediate heat transfer fluid/coolant heat exchanger is arranged at the outlet of the external heat exchanger, to enable storage management and/or energy restoration and the high pressure end and/or further cooling at the low pressure end. 
     According to further embodiments, the air conditioning circuit comprises a second expansion member. In particular, the second expansion member is controlled such that the coolant pressure at the outlet of the second expansion member is greater than the saturation pressure of the air flow to be distributed in the vehicle interior passing through the second heat exchanger to prevent frosting of the air flow to be distributed in the vehicle interior. 
     Preferentially, the air conditioning circuit comprises a third bypass arm arranged in parallel with the second expansion member and/or the second heat exchanger. 
     According to various designs, the first switching means and the second switching means are designed such that the coolant from the compressor passes successively through,
         the first heat exchanger, the first bypass pipe, the thermal storage device, the first return pipe, the first expansion member, the external heat exchanger, the second bypass arm and the third bypass arm, or   the first heat exchanger, the first expansion member, the external heat exchanger, the storage device and the third bypass arm, or   the first heat exchanger, the first bypass arm, the external heat exchanger, the storage device, the second expansion member and the second heat exchanger, or   the first heat exchanger, the first bypass pipe, the thermal storage device, the first return pipe, the first expansion member, the external heat exchanger, the second bypass arm, the second expansion member and the second heat exchanger.       

     Preferentially, the storage device contains a phase change material having a phase change temperature between 5° C. and 20° C., particularly between 10° C. and 15° C. 
    
    
     
       Further features and advantages of the present invention will emerge on reading the following detailed description including examples of embodiments given as a non-limitative illustration with reference to the appended figures, which may serve to complete the comprehension of the present invention and the description of the embodiment thereof, and, if applicable, contribute to the definition thereof, wherein: 
         FIG. 1  represents a schematic view of the air conditioning circuit according to a first operating mode, referred to as the “heating—storage mode”, wherein the vehicle interior is heated and the energy stored in the storage device is maintained, 
         FIG. 2  represents a schematic view of the air conditioning circuit according to a second operating mode, referred to as the “first heating—defrosting mode”, wherein the vehicle interior is heated and the external heat exchanger is defrosted using the storage device at the low pressure end of the thermodynamic circuit, 
         FIG. 3  represents a schematic view of the air conditioning circuit according to a third operating mode, referred to as the “second heating—defrosting mode”, wherein the vehicle interior is heated and the external heat exchanger is defrosted using the storage device at the high pressure end of the thermodynamic circuit, 
         FIG. 4  represents a schematic view of the air conditioning circuit according to a fourth operating mode, referred to as the “demisting—defrosting mode”, wherein the vehicle interior is demisted and/or frost formation on the external heat exchanger is limited using the storage device, 
         FIG. 5  represents a schematic view of the air conditioning circuit according to a fifth mode, referred to as the “cooling mode”, wherein the interior is cooled using the storage device, and 
         FIG. 6  represents a schematic view of the air conditioning circuit according to an alternative embodiment of the invention comprising a circuit on water. 
     
    
    
       FIG. 1  represents schematically an air conditioning circuit  12  according to the invention for a heating, ventilation and/or air conditioning installation. 
     The air conditioning circuit  12  enables the circulation of a coolant, particularly a subcritical fluid, such as R134A or equivalent, or a supercritical fluid, such as R744 or carbon dioxide. 
     The air conditioning circuit  12  comprises, in particular, in the direction of closed circuit circulation of the coolant, a compressor  14 , suitable for circulating the coolant inside the air conditioning circuit  12 , a first heat exchanger  16 , operating as a condenser  16  and suitable for heating an air flow to be distributed in the vehicle interior, a first expansion member  18 , such as, for example, an electronic expansion valve or a thermostatic expansion valve, an external heat exchanger  20 , a second expansion member  22 , a second heat exchanger  24 , operating as an evaporator  24  and suitable for dehumidifying and/or cooling the air flow to be distributed in the vehicle interior, and an accumulator  26 . At the outlet, the accumulator  26  is connected to the inlet of the compressor  14 . 
     The first heat exchanger  16  and the second heat exchanger  24  are placed in an air flow circulation pipe, not shown, opening into various areas of the vehicle interior. The first heat exchanger  16  and the second heat exchanger  24  are suitable for heating and/or cooling the air flow opening into the vehicle interior, particularly in an area arranged for demisting the windshield, a central aeration area and an area for feet. 
     The air flow suitable for distribution in the vehicle interior thus passes, in alternation or succession, through the first heat exchanger  16  and/or the second heat exchanger  24 . In particular, according to a particular example of an embodiment, a mixing flap is arranged in the circulation pipe to enable distribution of the air flow between the first heat exchanger  16  and the second heat exchanger  24 . Advantageously, the second heat exchanger  24  is arranged upstream from the first heat exchanger  16 , along the direction of circulation of the air flow in the circulation pipe. Preferentially, the entire air flow passes through the second heat exchanger  24  before passing through and/or bypassing the first heat exchanger  16 . 
     Advantageously, according to the invention, a thermal storage device  28  is incorporated in the air conditioning circuit  12  according to the present invention to store the calories carried by the coolant for subsequent use thereof according to the device operating modes. 
     According to one preferential arrangement, the thermal storage device  28  is arranged between the external heat exchanger  20  and the second expansion member  22 . 
     The air conditioning circuit  12  also comprises a first switching means  32 , particularly consisting of a first “three-way” valve  32 , particularly a first electrovalve  32 , arranged at the outlet of the first heat exchanger  16 . The first “three-way” valve  32  is connected, via a first bypass pipe  70 , to a first inlet of the thermal storage device  28 . A first outlet of the thermal storage device  28  is connected, via a first return pipe  72 , to the air conditioning circuit, downstream from the first “three-way” valve  32 , at a first connection point  50 . Such an arrangement makes it possible to control the storage of calories from the heat exchanger  16  to the storage device  28 . 
     The air conditioning circuit  12  comprises a first bypass arm  36 , arranged parallel with the first expansion member  18 . The first bypass arm  36  is arranged between a second connection point  52 , advantageously arranged downstream from the first connection point  50 , and a third connection point  54 , arranged downstream from the first expansion member  18 . 
     Preferentially, the first bypass channel  36  comprises a first control valve  30 , suitable for adopting an open position or a closed position to enable or block coolant circulation in the first bypass channel  36 , respectively. 
     The air conditioning circuit  12  also comprises a second switching means  34 , particularly a second “three-way” valve  34 , particularly a first electrovalve  34 , arranged at the outlet of the external heat exchanger  20 . The second “three-way” valve  34  is connected to a second bypass arm  38  and to a second inlet of the thermal storage device  28 , respectively. 
     The second bypass arm  38  is arranged between the second “three-way” valve  34  and a fourth connection point  56 , arranged downstream from the thermal storage device  28 . 
     The circulation of the coolant in the second bypass arm  38 , bypassing the storage device  28 , or in the storage device  28  is controlled by the second “three-way” valve  34  arranged at the outlet of the external heat exchanger  20 . 
     Thus, according to the present invention, the thermal storage device  28  is mounted both:
         at the outlet of the first heat exchanger  16 , to store the calories produced by and/or remaining in the first heat exchanger  16  in the first storage device  28 , with a maximum yield, and   at the outlet of the external heat exchanger  20 , to redistribute the calories via the coolant.       

     According to the invention, the storage device  28  may consist of a storage fluid tank storing the calories by working with sensible heat, or using a phase change material storage material storing the calories by working with latent heat. 
     Advantageously, the thermal storage device  28  is a dual-fluid heat exchanger enabling heat exchange between the coolant and the storage fluid/material. 
     Such a device  28  makes it possible to reduce the mass required and limit storage temperature variations. The phase change material has, according to the requirements of the invention, a phase change temperature between 5° C. and 25° C., particularly between 5° C. and 20° C., preferentially between 10° C. and 20° C. and notably between 10° C. and 15° C. 
     Thus, according to the various possible designs of the air conditioning circuit  12  specific to the various operating modes according to the figures in the present invention, the storage device  28  is suitable for storing the calories carried by the coolant from the first heat exchanger  16  and/or from the external heat exchanger  20 . Therefore, the storage device  28  is thus a heat and/or cold storage device. 
     In the present description, the term “calorie” covers all types of heat liable to be carried, in particular, by a coolant, a heat transfer fluid, an air flow, etc. The storage device  28  can thus store cold or heat according to the energy stored by the coolant, heat transfer fluid or air flow and according to the storage status of the storage device  28 . 
     Finally, the air conditioning circuit  12  comprises a third bypass arm  42 , arranged in parallel with the second expansion member  22  and the second heat exchanger  24 . The third bypass arm  42  is arranged between a fifth connection point  58 , arranged downstream from the second expansion member  22 , and a sixth connection point  60 , arranged downstream from the second heat exchanger  24 . Advantageously, the sixth connection point  60  is arranged upstream from the accumulator  26 . 
     Preferentially, the third bypass channel  42  comprises a second control valve  40 , suitable for adopting an open position or a closed position to enable or block coolant circulation in the third bypass channel  42 , respectively. 
     In the various designs of the air conditioning circuit  12 , preferentially, the first expansion member  18  and the second expansion member  22  are suitable for adopting closed positions when the first control valve  30  and the second control value  40  are in the open position, respectively. 
     Such an air conditioning circuit  12  thus makes it possible to provide various operating methods according to user requirements and thus improve the comfort thereof. 
       FIG. 1  represents a schematic view of the device according to the present invention in a first operating mode, referred to as the “heating—storage mode”, wherein the vehicle interior is heated and the energy stored in the storage device  28  is maintained. 
     With reference to the diagram in  FIG. 1  illustrating the first operating mode, the first “three-way” valve  32  is controlled so as to enable the circulation of the coolant in the storage device  28  and the second “three-way” valve  34  is controlled so as to enable the circulation of the coolant in the second bypass arm  38 , bypassing the storage device  28 . 
     The first control valve  30  is in the closed position to block the circulation of the coolant in the first bypass arm  36 , the coolant circulating in the first expansion member  18 . 
     The second control valve  40  is in the open position to enable the circulation of the coolant in the third bypass arm  42 , bypassing the second expansion member  22  and the second heat exchanger  24 . 
     In this way, in the first operating mode, referred to as the “heating—storage mode”, the coolant from the compressor  14  passes, in succession, through the first heat exchanger  16 , the first “three-way” valve  32 , the first bypass pipe  70 , the thermal storage device  28 , the first return pipe  72 , the first expansion member  18 , the external heat exchanger  20 , the second “three-way” valve  34 , the second bypass arm  38 , the third bypass arm  42  and the accumulator  26  before returning to the compressor  14 . 
     In the first operating mode design according to  FIG. 1 , the external heat exchanger  20  operates as an evaporator  20 . 
     The coolant condenses in the first heat exchanger  16  by exchanging heat with the air flow passing therethrough. The air flow channeled by the circulation pipe is thus heated on passing through the first heat exchanger  16  before being distributed in the vehicle interior. 
     The coolant is then expanded in the first expansion member  18  before being evaporated in the external heat exchanger  20 , operating in this design as an evaporator  20 . For this purpose, the external heat exchanger  20  is traversed by an external air flow exchanging calories with the coolant, which is cooled in the arrangement in  FIG. 1 . The external air flow is not intended to be distributed in the vehicle interior. 
     In the design in  FIG. 1 , the second heat exchanger  24  is not operational. Therefore, the air flow liable to be distributed in the vehicle interior and channeled by the circulation pipe is only heated by the first heat exchanger  16 . 
     Before the first operating mode is started, the temperature of the coolant contained in the storage device  28  is close to the external temperature. In this operating mode, the coolant passes through the second bypass arm  38  by controlling the second “three-way” valve  34 . Indeed, in the first operating mode, it is not intended for the storage device  28  to be used to restore stored calories. The first operating mode merely makes it possible to maintain the storage of calories contained therein. 
     According to the arrangement of the air conditioning circuit in  FIG. 1 , at the outlet of the first heat exchanger  16 , the coolant circulates in the storage device  28  where it is cooled. As specified above, the temperature of the coolant initially contained in the storage device  28  is close to the external temperature, below the temperature of the coolant at the outlet of the first heat exchanger  16 . 
     In this way, in the design of the first operating mode according to  FIG. 1 , the storage device  28  collects the calories carried by the coolant from the first heat exchanger  16 . Therefore, the storage device  28  is thus a heat storage device. 
     Advantageously according to the invention, during the first operating mode, referred to as the “heating—storage mode”, the storage device  28  accumulates energy in the form of calories. 
     Furthermore, the storage device  28  helps improve the cycle performance coefficient by reducing the temperature at the outlet of the first heat exchanger  16 . Increasing the performance coefficient thus makes it possible to store energy at least cost in respect to the power consumed by the compressor  14 . 
     In the design according to the first operating mode, energy is thus stored in the storage device  28  with an improved performance coefficient of the air conditioning circuit  12  cycle. 
     Also according to the invention, the calories stored in the storage device  28  are preferably at a mean temperature between 5° C. and 20° C., preferentially between 10° C. and 15° C. 
       FIG. 2  represents a schematic view of the device according to the present invention in a second operating mode, referred to as the “first heating—defrosting mode”, wherein the vehicle interior is heated and the external heat exchanger  20  is defrosted using the storage device  28  at the low pressure end of the air conditioning circuit  12  and restoration of the energy stored. 
     With reference to the diagram in  FIG. 2  illustrating the second operating mode, the first “three-way” valve  32  is controlled so to enable the direct connection of the outlet of the first heat exchanger  16  with the inlet of the first expansion member  18 , the circulation of the coolant not being authorized in the storage device  28 , and the second “three-way” valve  34  is controlled so as to enable the direct circulation of the coolant via the storage device  28 . 
     The first control valve  30  is in the closed position to block the circulation of the coolant in the first bypass arm  36 , the coolant circulating in the first expansion member  18 . 
     The second control valve  40  is in the open position to enable the circulation of the coolant in the third bypass arm  42 , bypassing the second expansion member  22  and the second heat exchanger  24 . 
     In this way, in the second operating mode, referred to as the “first heating—defrosting mode”, the coolant from the compressor  14  passes, in succession, through the first heat exchanger  16 , the first “three-way” valve  32 , the first expansion member  18 , the external heat exchanger  20 , the second “three-way” valve  34 , the second bypass arm  38 , the third bypass arm  42  and the accumulator  26  before returning to the compressor  14 . 
     In the second operating mode design according to  FIG. 2 , the external heat exchanger  20  operates as an evaporator  20 . 
     According to the second operating mode illustrated in  FIG. 2 , defrosting of the external surfaces of the external heat exchanger  20  may be performed at low pressures. 
     The coolant condenses in the first heat exchanger  16  by exchanging heat with the air flow passing therethrough. The air flow channeled by the circulation pipe is thus heated on passing through the first heat exchanger  16  before being distributed in the vehicle interior. 
     So as to heat the vehicle interior and simultaneously defrost the external heat exchanger  20 , the coolant evaporates partially in the external heat exchanger  20 , at a pressure determined by the storage device  28 , thus making it possible to defrost or limit the frosting of the external heat exchanger  20 . The storage device  28  thus acts, in this design, as a thermal load, performing a “thermal leverage” function at the low pressure end. The heat conveyed by the storage device  28  compensates for the cooling of the coolant such that the defrosting capacity is essentially provided by the storage device  28 . 
     The energy stored in the form of calories in the storage device  28  can thus be used at the low pressure end of the air conditioning circuit  12  to complete the evaporation of the coolant leaving the external heat exchanger  20 , which is defrosted. 
     The storage device  28  thus helps defrost the external heat exchanger  20  without impairing the efficiency of the air conditioning circuit  12 , which is the aim of the present invention. 
     Furthermore, according to the storage status of the storage device  28 , in the second operating mode design according to  FIG. 2 , the storage device  28  may also collect calories carried by the coolant from the external heat exchanger  20 . Therefore, alternatively, the storage device  28  is thus a cold storage device. 
       FIG. 3  represents a schematic view of the device according to the present invention in a third operating mode, referred to as the “second heating—defrosting mode”, wherein the vehicle interior is heated and the external heat exchanger is defrosted using the storage device  28  at the high pressure end of the air conditioning circuit  12  and restoration of the stored energy. 
     With reference to the diagram in  FIG. 3  illustrating the third operating mode, the first “three-way” valve  32  is controlled so to enable the direct connection of the outlet of the first heat exchanger  16  with the inlet of the first expansion member  18 , the circulation of the coolant not being authorized in the storage device  28 , and the second “three-way” valve  34  is controlled so as to enable the direct circulation of the coolant via the storage device  28 . 
     The first control valve  30  is in the open position to enable the circulation of the coolant in the first bypass arm  36 , the coolant bypassing the first expansion member  18 . 
     The second control valve  40  is in the closed position to block the circulation of the coolant in the third bypass arm  42 , the coolant circulating in succession in the second expansion member  22  and the second heat exchanger  24 . 
     In this way, in the third operating mode, referred to as the “second heating—defrosting mode”, the coolant from the compressor  14  passes, in succession, through the first heat exchanger  16 , the first “three-way” valve  32 , the first bypass arm  36 , the external heat exchanger  20 , the second “three-way” valve  34 , the storage device  28 , the second expansion member  22 , the second heat exchanger  24  and the accumulator  26  before returning to the compressor  14 . 
     The coolant condenses in the first heat exchanger  16  by exchanging heat with the air flow passing therethrough. The air flow channeled by the circulation pipe is thus heated on passing through the first heat exchanger  16  before being distributed in the vehicle interior. 
     In the third operating mode design according to  FIG. 3 , the external heat exchanger  20  operates as a condenser  20 . 
     According to the third operating mode of the air conditioning circuit  12  illustrated in  FIG. 3 , defrosting of the external surfaces of the external heat exchanger  20  may also be performed at high pressures. 
     The coolant condenses in the first heat exchanger  16  by exchanging heat with the air flow passing therethrough. The air flow channeled by the circulation pipe is thus heated on passing through the first heat exchanger  16  before being distributed in the vehicle interior. 
     The coolant then passes through the external heat exchanger  20  exchanging calories with the air flow passing through the external heat exchanger  20 . 
     In the event of the coolant not being completely condensed in the first heat exchanger  16 , the coolant continues to condense in the external heat exchanger  20  thus enabling the defrosting of the external heat exchanger  20 . 
     Furthermore, according to the design in  FIG. 3 , the coolant at the outlet of the first heat exchanger  16  is at a high temperature and high pressure. By bypassing the first expansion member  18 , the state of the coolant is substantially unchanged. Therefore, the external heat exchanger  20  is traversed by the coolant at a high temperature and at a high pressure thus helping, additionally and alternatively, defrost the external heat exchanger  20 . 
     At the outlet of the external heat exchanger  20 , the second “three-way” vale  34  is arranged to enable the direct circulation of the coolant via the storage device  28 . The coolant thus recovers energy on passing through the storage device  28  prior to expansion by the second expansion member  22 . 
     According to the previous storage statuses in question, the storage device  28  may alternatively store heat or cold. Therefore, the coolant is cooled or heated on passing through the storage device  28  prior to expansion by the second expansion member  22 . 
     Preferentially, on passing through the second expansion member  22 , the pressure and temperature of the coolant fall before passing through the second heat exchanger  24  wherein the coolant vaporizes by absorbing heat from the air flow passing therethrough to thus produce the cooled air flow. 
     The energy stored in the form of calories in the storage device  28  can thus be used at the high pressure end of the air conditioning circuit  12 . The storage device  28  thus enables heat exchange between the coolant and the storage fluid/material. The coolant is then situated at the outlet of the storage device  28  in a specific pressure and temperature state before passing through the second expansion member  22  wherein the expansion of the coolant is controlled such that, at the outlet of the second expansion member  22 , the low pressure of the coolant is greater than the saturation pressure of the air flow entering the second heat exchanger  24 . It is thus possible to defrost or prevent frosting of the second heat exchanger  24  without impairing the efficiency of the air conditioning circuit  12 . 
     According to this arrangement, the high pressure end of the air conditioning circuit  12  advantageously supplies a minimal amount of heat so as to heat the air flow suitable for being distributed in the vehicle interior. An additional, particularly electric, heating member may be arranged upstream from the first heat exchanger  16 , according to the direction of circulation of the air flow in the circulation pipe, so as to heat the air flow completely or partially to the desired temperature. 
       FIG. 4  represents a schematic view of the device according to the present invention in a fourth operating mode, referred to as the “demisting—defrosting mode”, wherein the vehicle interior is demisted and/or frost formation on the external heat exchanger  20  is limited using the storage device  28 . 
     With reference to the diagram in  FIG. 4  illustrating the fourth operating mode, the first “three-way” valve  32  is controlled so as to enable the circulation of the coolant in the storage device  28  and the second “three-way” valve  34  is controlled so as to enable the circulation of the coolant in the second bypass arm  38 , bypassing the storage device  28 . 
     The first control valve  30  is in the closed position to block the circulation of the coolant in the first bypass arm  36 , the coolant circulating in the first expansion member  18 . 
     The second control valve  40  is in the open position to enable the circulation of the coolant in the third bypass arm  42 , bypassing the second expansion member  22  and the second heat exchanger  24 . 
     In this way, in the fourth operating mode, referred to as the “demisting—defrosting mode”, the coolant from the compressor  14  passes, in succession, through the first heat exchanger  16 , the first “three-way” valve  32 , the first bypass pipe  70 , the thermal storage device  28 , the first return pipe  72 , the first expansion member  18 , the external heat exchanger  20 , the second “three-way” valve  34 , the second bypass arm  38 , the third bypass arm  42  and the accumulator  26  before returning to the compressor  14 . 
     In the fourth operating mode design according to  FIG. 4 , the external heat exchanger  20  operates as an evaporator  20 . 
     In order to demist the vehicle interior windows and/or limit frost formation in the external heat exchanger  20  according to  FIG. 4 , the coolant evaporates in the external heat exchanger  20  by absorbing the heat from the air flow passing through the external heat exchanger  20 . 
     The fluid then passes through the bypass channel  38  by controlling the second “three-way” valve  34 , since, in this operating mode, it is not intended for the storage device  28  to be used, but merely for the stored heat contained therein to be maintained. 
     The fluid then circulates in the expansion member  22  and the main evaporator  24  in succession. For this, the second control valve  40  is closed, the second expansion member  22  being open such that the coolant passes through the second heat exchanger  24 . On passing through the second expansion member  22 , the pressure and temperature of the coolant fall before passing through the second heat exchanger  24  wherein the coolant vaporizes by absorbing heat from the air flow passing therethrough to thus produce the cooled air flow. 
     According to the previous storage statuses in question, the coolant may pass through or bypass the storage device  28 . The storage device  28  is thus, according to requirements and the type of storage carried out, an energy accumulator or a thermal load, carrying out a “thermal leverage” function at the low pressure end, as defined above with reference to  FIG. 1 . 
     When the storage device  28  is used as a thermal load, carrying out a “thermal leverage” function at the low pressure end, a positive evaporation temperature can be defined in the external heat exchanger  20  to limit the risks of frosting of the external heat exchanger  20 . 
     In this operating mode, the storage device  28  is advantageously situated in a temperature range between 10° C. and 15° C. 
     Moreover, according to the energy storage temperature, the storage device  28  may be used as an additional cooling element, improving the performance coefficient of the air conditioning circuit  12 . 
     Therefore, the temperature of the storage device  28  makes it possible to define the design of the second “three-way” valve  34  in order to define whether, during the cycle, the storage device  28  is used to optimize the performance coefficient of the air conditioning circuit  12  by storing calories. In this way, for example, if the storage temperature, in the storage device  28 , is below a reference temperature, for example 15° C., the coolant from the air conditioning circuit  12  will supply the storage device  28  with calories until the reference temperature is reached. Once the reference temperature has been reached, the air conditioning circuit  12  will use the stored energy from the storage device  28  to optimize the performance coefficient of the air conditioning circuit  12  by deciding to restore the stored energy at the low pressure end as for the energy restoration for the defrosting function. 
       FIG. 5  represents a schematic view of the device according to the present invention in a fifth mode, referred to as the “cooling mode”, wherein the interior is cooled using the storage device  28 . 
     With reference to the diagram in  FIG. 5  illustrating the fifth operating mode, the first “three-way” valve  32  is controlled so as to enable the direct connection of the outlet of the first heat exchanger  16  with the inlet of the first expansion member  18 , the circulation of the coolant not being authorized in the storage device  28 , and the second “three-way” valve  34  is controlled so as to enable the direct circulation of the coolant via the storage device  28 . 
     The first control valve  30  is in the open position to enable the circulation of the coolant in the first bypass arm  36 , the coolant bypassing the first expansion member  18 . 
     The second control valve  40  is in the closed position to block the circulation of the coolant in the third bypass arm  42 , the coolant circulating in succession in the second expansion member  22  and the second heat exchanger  24 . 
     In this way, in the fifth operating mode, referred to as the “cooling mode”, the coolant from the compressor  14  passes, in succession, through the first heat exchanger  16 , the first “three-way” valve  32 , the first bypass arm  36 , the external heat exchanger  20 , the second “three-way” valve  34 , the storage device  28 , the second expansion member  22 , the second heat exchanger  24  and the accumulator  26  before returning to the compressor  14 . 
     In the fifth operating mode design according to  FIG. 5 , the external heat exchanger  20  operates as a condenser  20 . 
     The energy stored in the form of calories in the storage device  28  can thus be used at the “high pressure” end of the air conditioning circuit  12 . The energy stored in the storage device  28  is thus heated by the “high temperature” of the coolant before passing through the second expansion member  22 . The coolant is thus in a subcooled state at the outlet of the storage device  28 . 
     Therefore, the temperature of the storage device  28  makes it possible to define the design of the second “three-way” valve  34  in order to define whether, during the cycle, the storage device  28  is used to optimize the performance coefficient of the air conditioning circuit  12  by storing calories. In this way, for example, if the storage temperature, in the storage device  28 , is below a reference temperature, for example 15° C. as may occur when starting the vehicle, the coolant from the air conditioning circuit  12  is cooled in the storage device  28 , releasing heat. The storage device  28  thus becomes an additional cooler until the reference temperature is reached. The performance coefficient of the air conditioning circuit  12  during this operating mode is thus improved. 
     According to the invention, a second embodiment of the invention can be envisaged and is illustrated in  FIG. 6  representing a schematic view of the device according to a second embodiment of the invention comprising a circuit on water in a design equivalent to that in  FIG. 3 . 
     The other operating modes of this second embodiment may be deduced from the various designs represented in  FIGS. 1 to 5  with reference to the first embodiment. 
     The first and second switching means  32  and  34  are replaced by a first intermediate heat transfer fluid/coolant heat exchanger  44  and a second intermediate heat transfer fluid/coolant heat exchanger  46 , respectively, to store energy in the thermal storage device  28 . 
     The first and second intermediate heat transfer fluid/coolant heat exchangers  44  and  46  form, with the thermal storage device  28 , wherein a heat transfer fluid, particularly water, circulates, linking the thermal storage device  28  and the low pressure end and/or the high pressure end of the air conditioning circuit  12  according to the operating modes of the air conditioning circuit  12 . 
     The first and second intermediate heat transfer fluid/coolant heat exchangers  44  and  46  are thus dual-fluid heat exchangers enabling heat exchange between the coolant and the heat transfer fluid. 
     As represented in  FIG. 6 , the thermal storage device  28  is connected to the first intermediate heat transfer fluid/coolant heat exchanger  44  respectively via a first bypass pipe  70  and a first return pipe  72 . Moreover, the thermal storage device  28  is connected to the second intermediate heat transfer fluid/coolant heat exchanger  46  respectively via a second bypass pipe  80  and a second return pipe  82 . 
     The arrangement according to  FIG. 6  is such that the thermal storage device  28  is not traversed by the coolant. However, according to one alternative embodiment not shown, the thermal storage device  28  may be embodied in the form of a three-fluid heat exchanger between the coolant, heat transfer fluid and storage fluid/material. In such a case, the three-fluid thermal storage device  28  may be traversed by the heat transfer fluid and be arranged as defined in  FIGS. 1 to 5 . 
     For all the embodiments described above, a particular arrangement, not shown, of the second expansion member  22  may also be envisaged. Indeed, the second expansion member  22  may be formed in an equivalent manner to the first expansion member  18  and comprise a bypass arm comprising a dedicated control valve. 
     In addition to this alternative embodiment, it is also possible for the first connection point  58  to be arranged downstream from the second expansion member  22  and the bypass arm connection point of the second expansion member  22 . 
     It should be understood, however, that these examples of operation are given as illustrations of the subject matter of the invention. Obviously, the invention is not limited to these embodiments described above and merely given as examples. It covers various modifications, alternative forms and other alternative embodiments liable to be envisaged by those skilled in the art within the scope of the present invention, in particular any combinations of the various embodiments described above. 
     Furthermore, the various operating modes described above may be taken separately or combined to embody alternative embodiments and various designs of the same air conditioning circuit according to an air conditioning circuit thermal management method as defined according to the present invention.