EP2040946A1 - Air conditioning system operating on a supercritical cycle for use in motor vehicles - Google Patents

Air conditioning system operating on a supercritical cycle for use in motor vehicles

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Publication number
EP2040946A1
EP2040946A1 EP06779016A EP06779016A EP2040946A1 EP 2040946 A1 EP2040946 A1 EP 2040946A1 EP 06779016 A EP06779016 A EP 06779016A EP 06779016 A EP06779016 A EP 06779016A EP 2040946 A1 EP2040946 A1 EP 2040946A1
Authority
EP
European Patent Office
Prior art keywords
cooler
outside air
air conditioning
air
conditioning system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06779016A
Other languages
German (de)
French (fr)
Inventor
Thomas Justin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Renault Trucks SAS
Original Assignee
Renault Trucks SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Renault Trucks SAS filed Critical Renault Trucks SAS
Publication of EP2040946A1 publication Critical patent/EP2040946A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating [HVAC] devices
    • B60H1/32Cooling devices
    • B60H1/3204Cooling devices using compression
    • B60H1/3227Cooling devices using compression characterised by the arrangement or the type of heat exchanger, e.g. condenser, evaporator
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating [HVAC] devices
    • B60H1/32Cooling devices
    • B60H1/3204Cooling devices using compression
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating [HVAC] devices
    • B60H1/32Cooling devices
    • B60H1/3233Cooling devices characterised by condensed liquid drainage means
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating [HVAC] devices
    • B60H1/32Cooling devices
    • B60H1/3233Cooling devices characterised by condensed liquid drainage means
    • B60H1/32331Cooling devices characterised by condensed liquid drainage means comprising means for the use of condensed liquid, e.g. for humidification or for improving condenser performance
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00Gas cycle refrigeration machines
    • F25B2309/06Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2339/00Details of evaporators; Details of condensers
    • F25B2339/04Details of condensers
    • F25B2339/041Details of condensers of evaporative condensers

Definitions

  • the invention relates to the field of air conditioning systems used on motor vehicles. It relates more particularly to particular arrangements of the air conditioning system to optimize performance, while simplifying the refrigerant circuit, especially when it operates with a supercritical cycle.
  • an air-conditioning unit 1 comprises four main elements, namely an evaporator 2, a compressor 3, a gas-cooler exchanger or condenser 4, and an expander 5 connected by a circuit traveled by a refrigerant.
  • thermodynamic cycle of an air-conditioning unit operating according to a basic supercritical cycle comprises a first phase corresponding to the transition between the points A1 and A2.
  • the evaporator 2 captures the calories of the ventilation air circuit to be cooled 7, remaining at constant pressure, of the order of a few bars.
  • the refrigerant which has thus captured these calories is then compressed in a compressor 3, during the phase corresponding to the transition between points A2 and A3.
  • the compressed fluid then enters the cooler or condenser 4.
  • This cooler is a heat exchanger, at which the refrigerant transfers part of its heat to the outside environment 8, according to the phase substantially corresponding to the transition between the points A3 and A4 .
  • the fluid remains at a high pressure, greater than ten bars. Then, the coolant sees its pressure drop by its passage in the expander 5, corresponding to the transition phase between the points A4 and Al. The fluid then enters the evaporator 2.
  • criteria governing the choice of a refrigerant are in particular regulatory issues with respect to the environment. These criteria led in particular to consider the replacement of chlorofluorocarbon refrigerants by fluids such as carbon dioxide for example, which also allows air conditioning systems to operate in a supercritical cycle.
  • the temperature and pressure may be beyond the critical point, meaning that the transition from gaseous to liquid state is not physically definable.
  • the organ by which the calories captured are transmitted to the external environment is not the seat of a phenomenon of condensation, but simply a cooling of the refrigerant. There is therefore no condensation in the gas cooling exchanger.
  • the term "condenser”, used for the definition of a conventional air conditioning system is not physically correct in a system operating in a supercritical cycle. Therefore, in the rest of the description, this organ will be called "cooler".
  • the pressures in the refrigerant circuit are frequently greater than 100 bar, for temperatures of the order of 15O 0 C or more.
  • the various components of the refrigerant circuit, and in particular the pipes and fittings, must therefore be designed and dimensioned accordingly.
  • the efficiency of an air conditioning unit is evaluated by measuring a coefficient of performance.
  • This coefficient of performance is equal to the ratio of the power taken from the flow of ventilation air to be cooled, divided by the power consumed by the compressor.
  • This internal heat exchanger 9 as illustrated in FIG. 1, makes it possible to cool the high-pressure refrigerant at the outlet of the cooler 8, by transferring part of its heat to the low-pressure refrigerant exiting from it. the evaporator 2.
  • the corresponding thermodynamic cycle is illustrated in dotted lines in FIG. 2.
  • the passage in the internal exchanger of the low-pressure refrigerant leaving the evaporator 2 corresponds to the transition from the point A2 to the point A2 ' .
  • a quantity of heat is received from the high-pressure fluid leaving the cooler 8.
  • the compression takes place between the points A2 'and A3', and continues with the cooling within the cooler 8 between the points A3 'and A4.
  • a complementary temperature drop is obtained by crossing the internal exchanger 9, corresponding to the transition between the points A4 and A4 '.
  • the crossing of the expander 5 causes a drop in pressure, between the points A4 'and Al'.
  • the fluid is heated inside the evaporator 2 between the points A1 'and A2.
  • the coefficient of performance is improved thanks to this internal exchanger 9, since it is equal to the ratio of the differences in enthalpy between the phases Al '-A2 and A2'-A3'.
  • One of the objectives of the invention is to allow the operation of the air conditioning circuit with a higher coefficient of performance than those measured on existing systems.
  • Another object of the invention is to simplify the refrigerant circuit by reducing the weight, the volume and consequently the cost of the air conditioning circuit.
  • Another objective is to reduce the number of areas exposed to the risk of leakage and forcing a delicate sizing.
  • Another object of the invention is to allow operations at lower pressure levels with regard to the refrigerant fluid, so as to reduce the internal pressure losses, and allow the use of less expensive materials for the realization of the different organs of the circuit.
  • the air conditioning system according to the invention is characterized in that it comprises means for humidifying the outside air used for cooling the cooler, and in that it is free of internal exchanger.
  • the invention consists in improving the cooling of the coolant at the cooler, causing a phenomenon of evaporation of a certain amount of water introduced into the outside air coming into contact with the cooler, which captures the calories dissipated by the cooler.
  • this water can be projected in the form of microdroplets at the cooler.
  • the heat captured by these microdroplets can vaporize a certain amount, within the limit of the saturation of air vapor in contact with the cooler.
  • the coolant temperature at the outlet of the cooler is lowered, with the consequence that it is possible to dispense with the internal heat exchanger, used in previous systems to deliver to the pressure reducer a coolant at a sufficiently low temperature. This lowering of the temperature is obtained without the inconvenience observed in the art previous, which was an increase in the temperature and pressure of the fluid before entering the cooler.
  • the use of a phenomenon of evaporation at the cooler level makes it possible to improve the performance of this cooler, and consequently, the coefficient of performance of the whole system.
  • the improvement in the coefficient of performance is all the more appreciable because it is combined with a reduction in the complexity of the refrigerant circuit, and more specifically by the elimination of the internal exchanger required in the systems of the art. prior.
  • This advantage is further accentuated by the fact that the maximum pressure and / or temperature are reduced. Indeed, the compression phase is from the dew point and not from a higher temperature point as after passing through the internal exchanger of the prior art, which is favorable in terms of sizing the installation air conditioning.
  • the water spray can be projected directly on the chiller, or even in a flow of air to ventilate the chiller.
  • the ventilation can be forced, or even result from a natural convection, depending on the desired performance and the powers involved. It is also possible to use porous moist materials, known by the general name of "wetted media ", which can be passed through the ventilation air so as to load moisture which is then vaporized in contact with the cooler.
  • the means for humidifying the air in contact with the cooler can be fed by the recovery of the condensed water at the evaporator. In this way, all or part of the water produced at the evaporator can be used and reused to cool the cooler according to the invention. In the case where the water production at the evaporator is sufficient compared to the consumption for cooling the cooler, the autonomy can be obtained. It is also possible to provide this spray from an independent and autonomous reserve.
  • Figure 1 is a simplified diagram of an air conditioning system operating with a supercritical refrigerant fluid according to the state of the art.
  • FIG. 2 is an enthalpy / pressure diagram on which the steps of the thermodynamic cycle of systems of the prior art are simplified.
  • FIG. 3 is a simplified diagram of the air conditioning system according to the invention.
  • Figure 4 is an enthalpy / pressure diagram on which are shown in a simplified manner the different steps of the thermodynamic cycle of the refrigerant.
  • the air-conditioning system illustrated in FIG. 3 conventionally comprises an evaporator 22 traversed by the stream of air 27 to be cooled.
  • This evaporator 22 comprises an internal circuit connected to the refrigerant circuit 26.
  • the outlet of the evaporator 22 is connected to a compressor 23 which compresses this refrigerant fluid.
  • the cooling step takes place under temperature and pressure conditions beyond the critical point of the fluid, which justifies the term "supercritical".
  • the fluid used in a supercritical cycle may be carbon dioxide, the pressure and the temperature of the critical point of which are respectively 73 bars and 32 ° C.
  • the refrigerant is expanded at the expander 25 to then penetrate at reduced pressure into the evaporator 22.
  • the cooler 24 is associated with means for humidifying the outside air coming into contact with the cooler.
  • liquid water 32 is sprayed into the outside air, to capture a part of the heat dissipated by the cooler 24, in order to increase the heat exchange within the cooler 24.
  • This spray can take place directly on the cooler 24 itself, or preferentially in the air flow 28 which will be brought by ventilation in contact with the cooler 24.
  • the air conditioning system has a satisfactory coefficient of performance, without requiring the addition of an internal heat exchanger used on existing systems.
  • the water 32 which is used at the chiller 2 can be advantageously recovered at the level of the evaporator 22, at which a portion of the water contained in the flow of the condensate is condensed. ventilation air 27 to cool.
  • this water 33 can be collected by flow in a manifold 34 and then conveyed via a pipe 35 suitable for a tank 36.
  • the tank makes it possible to manage any discrepancies between the condensate flow rate and the flow rate necessary to humidification.
  • This tank 36 can optionally be supplied by an external water supply via the opening 37, to start the operation of the device when the water production of the evaporator 22 has not been sufficient, or that the weather conditions do not do not allow it.
  • This reservoir 36 may be equipped with a sensor 38 of the volume of water it contains, the information delivered by this sensor being conveyed to a suitable control and control unit 40, ensuring the management of the system.
  • a drain mechanism 41 and an overflow outlet 42 may also be provided. The emptying 41 can also be obtained by opening a valve 43 controlled by the control unit already mentioned.
  • a quantity of water can be taken from the lower part of the tank 36, so as to be conveyed near the cooler 24.
  • a metering mechanism 41 including in particular a pump for example volumetric 45 controlled by the control unit 40, ensures the spraying characteristic of a quantity given, and at times chosen to optimize the operation of the air conditioning system.
  • Filtration devices 47 may be provided upstream of the metering system, to prevent fouling of the pump 45, and downstream of the metering system 44, to prevent fouling of the spray members.
  • the bodies providing this spraying may in particular be constituted by nozzles 48 at high pressure, for which the diameter and the pressure of the water make it possible to determine the size of the droplets.
  • thermodynamic cycle of the system according to the invention is illustrated in FIG. 4, in solid lines, in comparison with a system of the prior art including an internal exchanger shown in dashed lines.
  • the heat captured by the refrigerant at the evaporator 22 corresponds to the transition between points Bl and B 2 of the diagram, during which, at constant pressure, the enthalpy of the refrigerant increases.
  • the variation of enthalpy during this phase corresponds to the energy captured by the system on the ventilation airflow 27 to be cooled.
  • B2 and B3 correspond to the compression phase, in which the pressure of the coolant increases, typically from 30 to 40 bar to about 90 bar.
  • the variation of enthalpy during this phase corresponds to the energy consumed by the compressor, to the efficiency of the latter.
  • the coefficient of performance of the system is therefore calculated by the ratio between the energy captured on the airflow, that is to say the difference in enthalpy between the points Bl and B2, relative to the energy consumed by compressor, ie the difference in enthalpy between points B2 and B3.
  • the coefficient of performance is order of 1.90.
  • a similar cycle implemented on a system of the prior art, including an internal exchanger, has a coefficient of performance of the order of 1.5. This coefficient is calculated as taking into account the energy captured at the level of the evaporator 22, corresponding to the transition between the points
  • the flow temperature at the outlet of compressor 27 in the system according to the invention is of the order of 92 ° C. (B3), compared with a temperature in the region of 160 ° C. (A3 ') at the output of compressor 3 in the prior art.
  • a complementary lowering of temperature is carried out at the level of the internal exchanger 9, bringing the temperature of the order of 45 ° C. at the outlet of the cooler 4 to a temperature of the order of 35 0 C at the inlet of the expander 5, which corresponds to the transition illustrated between the points A4 and A4 '.
  • the same temperature of the order of 35 0 C is obtained directly at the outlet of the cooler 24.
  • the system according to the invention is advantageous in that it allows operation at a lower temperature, with a more favorable coefficient of performance ratio, and this combined with a simpler refrigerant circuit structure.
  • the comparison of the pressure levels achieved is also in favor of the invention, since at a better coefficient of performance (1.90 compared to 1.50), the maximum pressure reached in the circuit is of the order of 90 bars. , compared with the 120 bars observed in the prior art, in the presence of an internal exchanger.
  • Such an improvement can be obtained when a quantity of water Sufficient is available, especially if the production of water recovered at the evaporator achieves autonomy. This of course depends on the climatic conditions, and in particular the humidity level and the ambient temperature. Thus, the maximum temperature and pressure values reached in the cooler can be optimized according to these climatic conditions.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Conditioning Control Device (AREA)

Abstract

The invention relates to an air conditioning system operating on a supercritical cycle for a vehicle, comprising a circuit through which a refrigerant flows, which circuit comprises an evaporator (22) where the refrigerant collects heat from the ventilation air to be conditioned, a compressor (23), a cooler (24) where the refrigerant releases heat into the outside air, and an expander (25), characterized in that it comprises means (48) for humidifying the outside air that contacts the cooler (24) and in that it has no internal heat exchanger.

Description

SYSTEME DE CLIMATISATION D'AIR FONCTIONNANT SELON UN AIR CONDITIONING SYSTEM OPERATING ACCORDING TO A
CYCLE SUPERCRITIOUE UTILISABLE SUR LES VEHICULESSUPERCRITICAL CYCLE FOR USE ON VEHICLES
AUTOMOBILESAUTOMOBILES
Domaine techniqueTechnical area
L'invention se rattache au domaine des systèmes de climatisation utilisés sur les véhicules automobiles. Elle vise plus particulièrement des agencements particuliers du système de climatisation permettant d'optimiser les performances, tout en simplifiant le circuit du fluide réfrigérant, en particulier lorsque celui-ci fonctionne avec un cycle supercritique.The invention relates to the field of air conditioning systems used on motor vehicles. It relates more particularly to particular arrangements of the air conditioning system to optimize performance, while simplifying the refrigerant circuit, especially when it operates with a supercritical cycle.
Techniques antérieuresPrevious techniques
De façon générale, et comme illustré à la figure 1, un groupe de climatisation 1 comporte quatre éléments principaux, à savoir un évaporateur 2, un compresseur 3, un échangeur refroidisseur de gaz ou condenseur 4, et un détendeur 5, reliés par un circuit parcouru par un fluide réfrigérant.In general, and as illustrated in FIG. 1, an air-conditioning unit 1 comprises four main elements, namely an evaporator 2, a compressor 3, a gas-cooler exchanger or condenser 4, and an expander 5 connected by a circuit traveled by a refrigerant.
Le cycle thermodynamique d'un groupe de climatisation fonctionnant selon un cycle supercritique basique, tel qu'illustré en traits gras à la figure 2, comporte une première phase, correspondant à la transition entre les points Al et A2. Lors de cette première phase, l'évaporateur 2 capte les calories du circuit d'air de ventilation à refroidir 7, en restant à pression constante, de l'ordre de quelques bars. Le fluide réfrigérant qui a ainsi capté ces calories est ensuite comprimé dans un compresseur 3, lors de la phase correspondant à la transition entre les points A2 et A3. Le fluide comprimé pénètre ensuite dans le refroidisseur ou condenseur 4. Ce refroidisseur est un échangeur thermique, au niveau duquel le fluide réfrigérant cède une partie de sa chaleur au milieu extérieur 8, selon la phase correspondant sensiblement à la transition entre les points A3 et A4. Le fluide reste à une pression élevée, supérieure à la dizaine de bars. Puis, le fluide réfrigérant voit sa pression chuter par son passage dans le détendeur 5, correspondant à la phase de transition entre les points A4 et Al. Le fluide rentre alors dans l'évaporateur 2. Parmi les critères qui gouvernent le choix d'un fluide réfrigérant figurent en particulier des questions de réglementation par rapport au respect de l'environnement. Ces critères ont conduit notamment à envisager le remplacement des fluides réfrigérants de type chlorofluorocarbone par des fluides tels que le dioxyde de carbone par exemple, qui permet de plus aux systèmes de climatisation de fonctionner suivant un cycle supercritique.The thermodynamic cycle of an air-conditioning unit operating according to a basic supercritical cycle, as shown in bold lines in FIG. 2, comprises a first phase corresponding to the transition between the points A1 and A2. During this first phase, the evaporator 2 captures the calories of the ventilation air circuit to be cooled 7, remaining at constant pressure, of the order of a few bars. The refrigerant which has thus captured these calories is then compressed in a compressor 3, during the phase corresponding to the transition between points A2 and A3. The compressed fluid then enters the cooler or condenser 4. This cooler is a heat exchanger, at which the refrigerant transfers part of its heat to the outside environment 8, according to the phase substantially corresponding to the transition between the points A3 and A4 . The fluid remains at a high pressure, greater than ten bars. Then, the coolant sees its pressure drop by its passage in the expander 5, corresponding to the transition phase between the points A4 and Al. The fluid then enters the evaporator 2. Among the criteria governing the choice of a refrigerant are in particular regulatory issues with respect to the environment. These criteria led in particular to consider the replacement of chlorofluorocarbon refrigerants by fluids such as carbon dioxide for example, which also allows air conditioning systems to operate in a supercritical cycle.
Dans les systèmes de climatisation fonctionnant selon un cycle supercritique, la température et la pression peuvent se situer au-delà du point critique, signifiant que le passage de l'état gazeux à l'état liquide n'est pas physiquement définissable. Parmi, les conséquences, l'organe par lequel les calories captées sont transmises au milieu extérieur n'est pas le siège d'un phénomène de condensation, mais simplement d'un refroidissement du fluide réfrigérant. Il n'y a donc pas de condensation dans l'échangeur de refroidissement du gaz. Ainsi, l'appellation de "condenseur", utilisée pour la définition d'un système de climatisation classique, n'est pas exacte d'un point de vue physique dans un système fonctionnant selon un cycle supercritique. Partant, dans le reste de la description, cet organe sera appelé "refroidisseur". Si l'emploi de systèmes fonctionnant selon des cycles supercritiques convient pour des raisons environnementales, il présente en revanche certaines contraintes en termes de dimensionnement. En effet, les pressions régnant dans le circuit du fluide réfrigérant sont fréquemment supérieures à 100 bars, pour des températures de l'ordre de 15O0C, voire plus. Les différents composants du circuit du fluide réfrigérant, et en particulier les canalisations et raccords, doivent donc être conçus et dimensionnés en conséquence.In supercritical air conditioning systems, the temperature and pressure may be beyond the critical point, meaning that the transition from gaseous to liquid state is not physically definable. Among the consequences, the organ by which the calories captured are transmitted to the external environment is not the seat of a phenomenon of condensation, but simply a cooling of the refrigerant. There is therefore no condensation in the gas cooling exchanger. Thus, the term "condenser", used for the definition of a conventional air conditioning system, is not physically correct in a system operating in a supercritical cycle. Therefore, in the rest of the description, this organ will be called "cooler". Although the use of systems operating on supercritical cycles is appropriate for environmental reasons, it does have certain design constraints. Indeed, the pressures in the refrigerant circuit are frequently greater than 100 bar, for temperatures of the order of 15O 0 C or more. The various components of the refrigerant circuit, and in particular the pipes and fittings, must therefore be designed and dimensioned accordingly.
De façon générale, l'efficacité d'un groupe de climatisation est évaluée par la mesure d'un coefficient de performance. Ce coefficient de performance est égal au ratio de la puissance prélevée sur le flux d'air de ventilation à refroidir, divisé par la puissance consommée par le compresseur. Ainsi, pour obtenir un coefficient de performance satisfaisant avec l'emploi d'un système fonctionnant selon un cycle supercritique, il est nécessaire d'utiliser un dispositif complémentaire, appelé « échangeur interne » tel qu'il est décrit par exemple dans le document EP-I 316 450. Cet échangeur interne 9, tel qu'illustré à la figure 1, permet de refroidir le fluide réfrigérant à haute pression en sortie du refroidisseur 8, en transférant une partie de sa chaleur vers le fluide réfrigérant à basse pression sortant de l'évaporateur 2. Le cycle thermodynamique correspondant est illustré en traits pointillés à la figure 2. Le passage dans l'échangeur interne du fluide réfrigérant à basse pression sortant de l'évaporateur 2, correspond à la transition du point A2 au point A2'. Pendant cette phase, une quantité de chaleur est reçue depuis le fluide à haute pression en sortie du refroidisseur 8. La compression s'effectue entre les points A2' et A3', et se poursuit par le refroidissement au sein du refroidisseur 8 entre les points A3' et A4. Une chute de température complémentaire est obtenue par la traversée de l'échangeur interne 9, correspondant à la transition entre les points A4 et A4'. La traversée du détendeur 5 provoque une baisse de pression, entre les points A4' et Al '. Puis, le fluide se réchauffe à l'intérieur de l'évaporateur 2, entre les points Al ' et A2. Globalement, le coefficient de performance est amélioré grâce à cet échangeur interne 9, puisqu'il est égal au rapport des différences d'enthalpie entre les phases Al '-A2 et A2'-A3'.In general, the efficiency of an air conditioning unit is evaluated by measuring a coefficient of performance. This coefficient of performance is equal to the ratio of the power taken from the flow of ventilation air to be cooled, divided by the power consumed by the compressor. Thus, to obtain a satisfactory coefficient of performance with the use of a system operating in a supercritical cycle, it is necessary to use a complementary device, called "internal exchanger" as described for example in the document EP This internal heat exchanger 9, as illustrated in FIG. 1, makes it possible to cool the high-pressure refrigerant at the outlet of the cooler 8, by transferring part of its heat to the low-pressure refrigerant exiting from it. the evaporator 2. The corresponding thermodynamic cycle is illustrated in dotted lines in FIG. 2. The passage in the internal exchanger of the low-pressure refrigerant leaving the evaporator 2 corresponds to the transition from the point A2 to the point A2 ' . During this phase, a quantity of heat is received from the high-pressure fluid leaving the cooler 8. The compression takes place between the points A2 'and A3', and continues with the cooling within the cooler 8 between the points A3 'and A4. A complementary temperature drop is obtained by crossing the internal exchanger 9, corresponding to the transition between the points A4 and A4 '. The crossing of the expander 5 causes a drop in pressure, between the points A4 'and Al'. Then, the fluid is heated inside the evaporator 2 between the points A1 'and A2. Overall, the coefficient of performance is improved thanks to this internal exchanger 9, since it is equal to the ratio of the differences in enthalpy between the phases Al '-A2 and A2'-A3'.
On conçoit que l'emploi de cet échangeur interne, s'il est nécessaire pour obtenir un coefficient de performance satisfaisant, engendre cependant une complexification du circuit du fluide réfrigérant. Ceci est d'autant plus pénalisant qu'il entraîne des niveaux de température et de pression élevés. En effet, grâce à la chute de température du fluide en amont du détendeur 5, les échanges de chaleur dans l'évaporateur 2 sont plus efficaces, car le fluide réfrigérant se trouve à température moindre. Toutefois, cette amélioration des échanges dans l'évaporateur se traduit par une augmentation de la température du fluide à comprimer, au niveau de l'échangeur interne 9. Le fluide comprimé se retrouve donc dans le refroidisseur 4 à un niveau de température très élevé et à haute pression. Ceci engendre donc des contraintes en termes d'étanchéité et de tenue des matériaux. L'emploi de composants complémentaires provoque également une augmentation du poids et du prix de revient du circuit global.It is understood that the use of this internal exchanger, if it is necessary to obtain a satisfactory coefficient of performance, however, causes a complexity of the refrigerant circuit. This is all the more penalizing as it leads to high temperature and pressure levels. Indeed, thanks to the temperature drop of the fluid upstream of the expander 5, the heat exchange in the evaporator 2 is more efficient because the coolant is at a lower temperature. However, this improvement of the exchanges in the evaporator results in an increase in the temperature of the fluid to be compressed at the level of the internal exchanger 9. The compressed fluid is therefore found in the cooler 4 at a very high temperature level and at high pressure. This therefore generates constraints in terms of sealing and holding materials. The use of complementary components also causes an increase in the weight and the cost price of the global circuit.
Exposé de l'invention Un des objectifs de l'invention est de permettre le fonctionnement du circuit de climatisation avec un coefficient de performance plus élevé que ceux mesurés sur les systèmes existants. Un autre objectif de l'invention est de simplifier le circuit du fluide réfrigérant, en réduisant le poids, le volume et par voie de conséquence le coût du circuit de climatisation. Un autre objectif est de diminuer le nombre de zones exposées aux risques de fuites et obligeant à un dimensionnement délicat. Un autre objectif de l'invention est de permettre des fonctionnements à des niveaux de pression moins élevés en ce qui concerne le fluide réfrigérant, de manière à réduire les pertes de charge internes, et permettre l'emploi de matériaux moins coûteux pour la réalisation des différents organes du circuit.SUMMARY OF THE INVENTION One of the objectives of the invention is to allow the operation of the air conditioning circuit with a higher coefficient of performance than those measured on existing systems. Another object of the invention is to simplify the refrigerant circuit by reducing the weight, the volume and consequently the cost of the air conditioning circuit. Another objective is to reduce the number of areas exposed to the risk of leakage and forcing a delicate sizing. Another object of the invention is to allow operations at lower pressure levels with regard to the refrigerant fluid, so as to reduce the internal pressure losses, and allow the use of less expensive materials for the realization of the different organs of the circuit.
Ainsi, le système de climatisation conforme à l'invention se caractérise en ce qu'il comporte des moyens pour humidifier l'air extérieur utilisé pour refroidir le refroidisseur, et en ce qu'il est exempt d'échangeur interne.Thus, the air conditioning system according to the invention is characterized in that it comprises means for humidifying the outside air used for cooling the cooler, and in that it is free of internal exchanger.
Autrement dit, l'invention consiste à améliorer le refroidissement du fluide réfrigérant au niveau du refroidisseur, en provoquant un phénomène d'évaporation d'une certaine quantité d'eau introduite dans l'air extérieur venant au contact du refroidisseur, qui capte les calories dissipées par le refroidisseur. Dans une forme de réalisation particulière, cette eau peut être projetée à l'état de microgouttelettes au niveau du refroidisseur. De la sorte, la chaleur captée par ces microgouttelettes permet d'en vaporiser une certaine quantité, dans la limite de la saturation en vapeur de l'air au contact du refroidisseur. Ainsi, la température du fluide réfrigérant en sortie du refroidisseur est abaissée, avec pour conséquence qu'il est possible de s'affranchir de l'échangeur interne, utilisé dans les systèmes antérieurs pour délivrer au détendeur un fluide réfrigérant à température suffisamment basse. Cet abaissement de la température s'obtient sans l'inconvénient observé dans l'art antérieur, qui était une augmentation de la température et de la pression du fluide avant son entrée dans le refroidisseur.In other words, the invention consists in improving the cooling of the coolant at the cooler, causing a phenomenon of evaporation of a certain amount of water introduced into the outside air coming into contact with the cooler, which captures the calories dissipated by the cooler. In a particular embodiment, this water can be projected in the form of microdroplets at the cooler. In this way, the heat captured by these microdroplets can vaporize a certain amount, within the limit of the saturation of air vapor in contact with the cooler. Thus, the coolant temperature at the outlet of the cooler is lowered, with the consequence that it is possible to dispense with the internal heat exchanger, used in previous systems to deliver to the pressure reducer a coolant at a sufficiently low temperature. This lowering of the temperature is obtained without the inconvenience observed in the art previous, which was an increase in the temperature and pressure of the fluid before entering the cooler.
En d'autres termes, l'utilisation d'un phénomène d'évaporation au niveau de refroidisseur permet d'améliorer les performances de ce dernier, et par conséquent, le coefficient de performance de l'ensemble du système. L'amélioration du coefficient de performance est d'autant plus appréciable qu'elle est combinée à une réduction de la complexité du circuit du fluide réfrigérant, et plus précisément par l'élimination de l'échangeur interne nécessaire dans les systèmes de l'art antérieur. Cet avantage est encore accentué par le fait que la pression et/ou température maximales sont réduites. En effet, la phase de compression se fait à partir du point de rosée et non d'un point de température supérieure comme après passage dans l'échangeur interne de l'art antérieur, ce qui est favorable en termes de dimensionnement de l'installation de climatisation.In other words, the use of a phenomenon of evaporation at the cooler level makes it possible to improve the performance of this cooler, and consequently, the coefficient of performance of the whole system. The improvement in the coefficient of performance is all the more appreciable because it is combined with a reduction in the complexity of the refrigerant circuit, and more specifically by the elimination of the internal exchanger required in the systems of the art. prior. This advantage is further accentuated by the fact that the maximum pressure and / or temperature are reduced. Indeed, the compression phase is from the dew point and not from a higher temperature point as after passing through the internal exchanger of the prior art, which is favorable in terms of sizing the installation air conditioning.
L'eau pulvérisée peut être projetée directement sur le refroidisseur, ou bien encore dans un flux d'air destiné à ventiler le refroidisseur. La ventilation peut être forcée, ou bien encore résulter d'une convection naturelle, en fonction des performances souhaitées et des puissances mises en jeu. Il est également possible d'utiliser des matériaux poreux humidifiés, connus sous l'appellation générale de « wetted média », qui peuvent être traversés par l'air de ventilation de manière à se charger en humidité qui est ensuite vaporisée au contact du refroidisseur.The water spray can be projected directly on the chiller, or even in a flow of air to ventilate the chiller. The ventilation can be forced, or even result from a natural convection, depending on the desired performance and the powers involved. It is also possible to use porous moist materials, known by the general name of "wetted media ", Which can be passed through the ventilation air so as to load moisture which is then vaporized in contact with the cooler.
Selon une autre caractéristique de l'invention, les moyens pour humidifier l'air au contact du refroidisseur peuvent être alimentés par la récupération de l'eau condensée au niveau de l'évaporateur. De la sorte, tout ou partie de l'eau produite au niveau de l'évaporateur peut être mise à profit et réutilisée pour refroidir le refroidisseur, conformément à l'invention. Dans le cas où la production d'eau au niveau de l'évaporateur est suffisante par rapport à la consommation pour le refroidissement du refroidisseur, l'autonomie peut être obtenue. Il est également possible d'assurer cette pulvérisation à partir d'une réserve indépendante et autonome. Description sommaire des figuresAccording to another characteristic of the invention, the means for humidifying the air in contact with the cooler can be fed by the recovery of the condensed water at the evaporator. In this way, all or part of the water produced at the evaporator can be used and reused to cool the cooler according to the invention. In the case where the water production at the evaporator is sufficient compared to the consumption for cooling the cooler, the autonomy can be obtained. It is also possible to provide this spray from an independent and autonomous reserve. Brief description of the figures
La manière de réaliser l'invention, ainsi que les avantages qui en découlent, ressortiront bien de la description du mode de réalisation qui suit, à l'appui des figures annexées, dans lesquelles :The manner of carrying out the invention, as well as the advantages which result therefrom, will emerge clearly from the following description of the embodiment, in support of the appended figures, in which:
La figure 1 est un schéma simplifié d'un système de climatisation fonctionnant avec un fluide réfrigérant supercritique selon l'état de la technique.Figure 1 is a simplified diagram of an air conditioning system operating with a supercritical refrigerant fluid according to the state of the art.
La figure 2 est un diagramme enthalpie/pression sur lequel figurent de façon simplifié les étapes du cycle thermodynamique de systèmes de l'art antérieur.FIG. 2 is an enthalpy / pressure diagram on which the steps of the thermodynamic cycle of systems of the prior art are simplified.
La figure 3 est un schéma simplifié du système de climatisation conforme à l'invention.Figure 3 is a simplified diagram of the air conditioning system according to the invention.
La figure 4 est un diagramme enthalpie/pression sur lequel figurent de façon simplifiée les différentes étapes du cycle thermodynamique du fluide réfrigérant.Figure 4 is an enthalpy / pressure diagram on which are shown in a simplified manner the different steps of the thermodynamic cycle of the refrigerant.
Manière de réaliser l'inventionWay of realizing the invention
Le système d'air conditionné illustré à la figure 3 comporte de manière classique un évaporateur 22 traversé par le flux d'air 27 à refroidir. Cet évaporateur 22 comporte un circuit interne relié au circuit du fluide réfrigérant 26. La sortie de l'évaporateur 22 est reliée à un compresseur 23 qui comprime ce fluide réfrigérant. L'étape de refroidissement se déroule dans des conditions de température et de pression situées au-delà du point critique du fluide, ce qui justifie le qualificatif de "supercritique". A titre d'exemple, le fluide utilisé suivant un cycle supercritique peut être du dioxyde de carbone, dont la pression et la température du point critique sont respectivement de 73 bars et 320C. Après refroidissement dans le refroidisseur 24, le fluide réfrigérant est détendu au niveau du détendeur 25 pour ensuite pénétrer à pression réduite dans l'évaporateur 22.The air-conditioning system illustrated in FIG. 3 conventionally comprises an evaporator 22 traversed by the stream of air 27 to be cooled. This evaporator 22 comprises an internal circuit connected to the refrigerant circuit 26. The outlet of the evaporator 22 is connected to a compressor 23 which compresses this refrigerant fluid. The cooling step takes place under temperature and pressure conditions beyond the critical point of the fluid, which justifies the term "supercritical". By way of example, the fluid used in a supercritical cycle may be carbon dioxide, the pressure and the temperature of the critical point of which are respectively 73 bars and 32 ° C. After cooling in the cooler 24, the refrigerant is expanded at the expander 25 to then penetrate at reduced pressure into the evaporator 22.
Conformément à l'invention, le refroidisseur 24 est associé à des moyens permettant d'humidifier l'air extérieur venant au contact du refroidisseur. Dans le mode de réalisation illustré, on pulvérise de l'eau liquide 32 dans l'air extérieur, pour capter une partie de la chaleur dissipée par le refroidisseur 24, afin d'augmenter l'échange de chaleur au sein du refroidisseur 24. Cette pulvérisation peut intervenir directement sur le refroidisseur 24 lui-même, ou préférentiellement dans le flux d'air 28 qui sera amené par ventilation au contact du refroidisseur 24. Grâce à ce refroidissement par évaporation, le système de climatisation possède un coefficient de performance satisfaisant, sans nécessiter l'adjonction d'un échangeur interne de chaleur employé sur les systèmes existants.According to the invention, the cooler 24 is associated with means for humidifying the outside air coming into contact with the cooler. In the illustrated embodiment, liquid water 32 is sprayed into the outside air, to capture a part of the heat dissipated by the cooler 24, in order to increase the heat exchange within the cooler 24. This spray can take place directly on the cooler 24 itself, or preferentially in the air flow 28 which will be brought by ventilation in contact with the cooler 24. With this evaporative cooling, the air conditioning system has a satisfactory coefficient of performance, without requiring the addition of an internal heat exchanger used on existing systems.
Conformément à une caractéristique de l'invention, l'eau 32 qui est utilisée au niveau du refroidisseur 2 peut être avantageusement récupérée au niveau de l'évaporateur 22, au niveau duquel se condense une partie de l'eau contenue dans le flux d'air de ventilation 27 à refroidir.According to a characteristic of the invention, the water 32 which is used at the chiller 2 can be advantageously recovered at the level of the evaporator 22, at which a portion of the water contained in the flow of the condensate is condensed. ventilation air 27 to cool.
Comme illustré à la figure 3, cette eau 33 peut être recueillie par écoulement dans un collecteur 34, puis acheminée par une canalisation 35 appropriée à un réservoir 36. Le réservoir permet de gérer les éventuels écarts entre le débit de condensât et le débit nécessaire à l'humidification. Ce réservoir 36 peut éventuellement être alimenté par un apport d'eau extérieur via l'ouverture 37, pour amorcer le fonctionnement du dispositif lorsque la production d'eau de l'évaporateur 22 n'a pas été suffisante, ou que les conditions météorologiques ne le permettent pas. Ce réservoir 36 peut être équipé d'un capteur 38 du volume d'eau qu'il contient, l'information délivrée par ce capteur étant acheminée vers une unité de contrôle et de commande appropriée 40, assurant la gestion du système. Un mécanisme de vidange 41 et d'évacuation d'un trop-plein 42 peut également être prévu. La vidange 41 peut également être obtenue par l'ouverture d'une vanne 43 commandée par l'unité de contrôle commande déjà évoquée.As illustrated in FIG. 3, this water 33 can be collected by flow in a manifold 34 and then conveyed via a pipe 35 suitable for a tank 36. The tank makes it possible to manage any discrepancies between the condensate flow rate and the flow rate necessary to humidification. This tank 36 can optionally be supplied by an external water supply via the opening 37, to start the operation of the device when the water production of the evaporator 22 has not been sufficient, or that the weather conditions do not do not allow it. This reservoir 36 may be equipped with a sensor 38 of the volume of water it contains, the information delivered by this sensor being conveyed to a suitable control and control unit 40, ensuring the management of the system. A drain mechanism 41 and an overflow outlet 42 may also be provided. The emptying 41 can also be obtained by opening a valve 43 controlled by the control unit already mentioned.
Pour le fonctionnement de l'invention, une quantité d'eau peut être prélevée dans la partie basse du réservoir 36, de manière à être acheminée à proximité du refroidisseur 24. Pour ce faire, un mécanisme de dosage 41, incluant en particulier une pompe par exemple volumétrique 45 commandée par l'unité de contrôle commande 40, permet d'assurer la pulvérisation caractéristique d'une quantité donnée, et aux instants choisis pour optimiser le fonctionnement du système de climatisation. Des dispositifs de filtration 47 peuvent être prévus en amont du système de dosage, pour éviter tout encrassement de la pompe 45, et en aval du système de dosage 44, pour éviter l'encrassement des organes de pulvérisation. Dans le cas où l'humidification est réalisée par pulvérisation, les organes assurant cette pulvérisation peuvent notamment être constitués par des buses 48 à haute pression, pour lesquelles le diamètre et la pression de l'eau permettent de déterminer la taille des gouttelettes.For the operation of the invention, a quantity of water can be taken from the lower part of the tank 36, so as to be conveyed near the cooler 24. To do this, a metering mechanism 41, including in particular a pump for example volumetric 45 controlled by the control unit 40, ensures the spraying characteristic of a quantity given, and at times chosen to optimize the operation of the air conditioning system. Filtration devices 47 may be provided upstream of the metering system, to prevent fouling of the pump 45, and downstream of the metering system 44, to prevent fouling of the spray members. In the case where the wetting is carried out by spraying, the bodies providing this spraying may in particular be constituted by nozzles 48 at high pressure, for which the diameter and the pressure of the water make it possible to determine the size of the droplets.
De manière simplifiée, le cycle thermodynamique du système conforme à l'invention est illustré à la figure 4, en traits pleins, par comparaison avec un système de l'art antérieur incluant un échangeur interne montré en traits pointillés.In a simplified manner, the thermodynamic cycle of the system according to the invention is illustrated in FIG. 4, in solid lines, in comparison with a system of the prior art including an internal exchanger shown in dashed lines.
Ainsi, la chaleur captée par le fluide réfrigérant au niveau de l'évaporateur 22 correspond à la transition entre les points Bl et B 2 du diagramme, au cours de laquelle, à pression constante, l'enthalpie du fluide réfrigérant augmente. La variation d'enthalpie durant cette phase correspond à l'énergie captée par le système sur le flux d'air de ventilation 27 à refroidir. La transition entre les pointsThus, the heat captured by the refrigerant at the evaporator 22 corresponds to the transition between points Bl and B 2 of the diagram, during which, at constant pressure, the enthalpy of the refrigerant increases. The variation of enthalpy during this phase corresponds to the energy captured by the system on the ventilation airflow 27 to be cooled. The transition between points
B2 et B3 correspond à la phase de compression, dans laquelle la pression du fluide réfrigérant augmente, passant typiquement de 30 à 40 bars à 90 bars environ. La variation d'enthalpie durant cette phase correspond à l'énergie consommée par le compresseur, au rendement de ce dernier près.B2 and B3 correspond to the compression phase, in which the pressure of the coolant increases, typically from 30 to 40 bar to about 90 bar. The variation of enthalpy during this phase corresponds to the energy consumed by the compressor, to the efficiency of the latter.
Le coefficient de performance du système est donc calculé par le rapport entre l'énergie captée sur le flux d'air, c'est-à-dire la différence d'enthalpie entre les points Bl et B2, rapportée à l'énergie consommée par le compresseur, c'est-à- dire la différence d'enthalpie entre les points B2 et B3.The coefficient of performance of the system is therefore calculated by the ratio between the energy captured on the airflow, that is to say the difference in enthalpy between the points Bl and B2, relative to the energy consumed by compressor, ie the difference in enthalpy between points B2 and B3.
On constate donc dans l'exemple particulier, correspondant à des conditions de température ambiante extrêmes, du type 4O0C de température extérieure, avec un taux d'humidité de l'ordre de 50 %, que le coefficient de performance est de l'ordre de 1,90. Par comparaison, un cycle similaire, mis en œuvre sur un système de l'art antérieur, incluant un échangeur interne, présente un coefficient de performances de l'ordre de 1,5. Ce coefficient est calculé comme prenant en compte l'énergie captée au niveau de l'évaporateur 22, correspondant à la transition entre les pointsTherefore, in the particular example, corresponding to extreme ambient temperature conditions, of the external temperature type 40 ° C., with a humidity level of the order of 50%, it can be seen that the coefficient of performance is order of 1.90. By comparison, a similar cycle, implemented on a system of the prior art, including an internal exchanger, has a coefficient of performance of the order of 1.5. This coefficient is calculated as taking into account the energy captured at the level of the evaporator 22, corresponding to the transition between the points
Al ' et B2, rapportée à la phase de compression, illustrée entre les points A2' etAl 'and B2, referred to the compression phase, illustrated between the points A2' and
A3'. L'augmentation de température entre la sortie de l'évaporateur 22 et l'entrée dans le compresseur 23, illustrée par la transition entre les points B2 et A2' correspond au réchauffement intervenant par l'intermédiaire de l' échangeur interne, tel qu'illustré à la figure 1.A3. The increase in temperature between the outlet of the evaporator 22 and the inlet into the compressor 23, illustrated by the transition between the points B2 and A2 'corresponds to the heating occurring via the internal exchanger, such as illustrated in Figure 1.
A titre d'exemple de comparaison chiffrée, la température de flux en sortie de compresseur 27 dans le système conforme à l'invention, est de l'ordre de 920C (B3), à comparer avec une température voisine de 16O0C (A3') en sortie de compresseur 3 dans l'art antérieur. De même, dans l'art antérieur, un abaissement de température complémentaire est effectué au niveau de l'échangeur interne 9, faisant passer la température de l'ordre de 450C en sortie du refroidisseur 4 à une température de l'ordre de 350C en entrée du détendeur 5, ce qui correspond à la transition illustrée entre les points A4 et A4'.As an example of an encrypted comparison, the flow temperature at the outlet of compressor 27 in the system according to the invention is of the order of 92 ° C. (B3), compared with a temperature in the region of 160 ° C. (A3 ') at the output of compressor 3 in the prior art. Similarly, in the prior art, a complementary lowering of temperature is carried out at the level of the internal exchanger 9, bringing the temperature of the order of 45 ° C. at the outlet of the cooler 4 to a temperature of the order of 35 0 C at the inlet of the expander 5, which corresponds to the transition illustrated between the points A4 and A4 '.
A l'inverse, dans le dispositif conforme à l'invention, la même température de l'ordre de 350C est obtenue directement en sortie du refroidisseur 24. Autrement dit, le système conforme à l'invention est avantageux en ce qu'il permet un fonctionnement à température plus faible, avec un taux de coefficient de performance plus favorable, et ce combiné avec une structure du circuit de fluide réfrigérant plus simple.Conversely, in the device according to the invention, the same temperature of the order of 35 0 C is obtained directly at the outlet of the cooler 24. In other words, the system according to the invention is advantageous in that it allows operation at a lower temperature, with a more favorable coefficient of performance ratio, and this combined with a simpler refrigerant circuit structure.
La comparaison des niveaux de pression atteints est également en faveur de l'invention, puisqu'à coefficient de performance meilleur (1,90 à comparer à 1,50), la pression maximale atteinte dans le circuit est de l'ordre de 90 bars, à comparer avec les 120 bars observés dans l'Art Antérieur, en présence d'un échangeur interne. Une telle amélioration peut être obtenue dès lors qu'une quantité d'eau suffisante est disponible, en particulier si la production d'eau récupérée au niveau de l'évaporateur permet d'atteindre l'autonomie. Ceci dépend bien entendu des conditions climatiques, et notamment du taux d'humidité et de la température ambiants. Ainsi, les valeurs maximales de température et de pression atteintes dans le refroidisseur peuvent être optimisées en fonction de ces conditions climatiques.The comparison of the pressure levels achieved is also in favor of the invention, since at a better coefficient of performance (1.90 compared to 1.50), the maximum pressure reached in the circuit is of the order of 90 bars. , compared with the 120 bars observed in the prior art, in the presence of an internal exchanger. Such an improvement can be obtained when a quantity of water Sufficient is available, especially if the production of water recovered at the evaporator achieves autonomy. This of course depends on the climatic conditions, and in particular the humidity level and the ambient temperature. Thus, the maximum temperature and pressure values reached in the cooler can be optimized according to these climatic conditions.
Ainsi, à performances égales, il est possible d'utiliser des compresseurs de taille inférieure ou de moindre consommation. Il est également possible de définir des cycles où la pression maximum est inférieure, ce qui est avantageux en termes de dimensionnement du circuit de fluide réfrigérant. Thus, with equal performances, it is possible to use compressors of smaller size or lower consumption. It is also possible to define cycles where the maximum pressure is lower, which is advantageous in terms of sizing the refrigerant circuit.

Claims

REVENDICATIONS
1/ Système de climatisation d'air fonctionnant selon un cycle supercritique pour véhicule, comprenant un circuit parcouru par un fluide réfrigérant, ledit circuit comportant un évaporateur (22) au niveau duquel le fluide réfrigérant capte de la chaleur à l'air de ventilation à climatiser, un compresseur (23), un refroidisseur1 / air conditioning system operating in a supercritical cycle for a vehicle, comprising a circuit traversed by a refrigerant, said circuit comprising an evaporator (22) at which the coolant captures heat to the ventilation air at air conditioning, compressor (23), cooler
(24) au niveau duquel le fluide réfrigérant cède de la chaleur à l'air extérieur, et un détendeur (25), caractérisé en ce qu'il comporte des moyens (48) pour humidifier l'air extérieur venant au contact du refroidisseur (24), et en ce qu'il est exempt d'échangeur interne de chaleur.(24) at which the coolant transfers heat to the outside air, and an expander (25), characterized in that it comprises means (48) for humidifying the outside air coming into contact with the cooler ( 24), and in that it is free of internal heat exchanger.
2/ Système selon la revendication 1, caractérisé en ce que les moyens pour humidifier l'air extérieur sont alimentés par la récupération de l'eau condensée au niveau de l'évaporateur (22).2 / System according to claim 1, characterized in that the means for humidifying the outside air are supplied by the recovery of the condensed water at the evaporator (22).
3/ Système selon la revendication 1, caractérisé en ce que les moyens pour humidifier l'air extérieur assurent une projection d'eau pulvérisée dans l'air extérieur.3 / A system according to claim 1, characterized in that the means for humidifying the outside air provide a spray of water spray in the outside air.
4/ Système selon la revendication 1, caractérisé en ce que les moyens pour humidifier l'air extérieur assurent le passage de l'air extérieur à travers un média humidifié.4 / System according to claim 1, characterized in that the means for moistening the outside air ensure the passage of outside air through a humidified media.
5/ Système selon la revendication 1, caractérisé en ce que les moyens pour humidifier l'air extérieur assurent une projection d'eau pulvérisée sur le refroidisseur.5 / System according to claim 1, characterized in that the means for humidifying the outside air provide a spray of water spray on the cooler.
6/ Système de climatisation d'air selon la revendication 1, caractérisé en ce qu'il comporte des moyens pour assurer une ventilation du refroidisseur (24) par l'air extérieur humidifié. 11 Système de climatisation d'air selon la revendication 2, caractérisé en ce qu'il comporte un réservoir (36) alimenté par l'eau condensée au niveau de l'évaporateur (22).6 / air conditioning system according to claim 1, characterized in that it comprises means for ensuring ventilation of the cooler (24) by the humidified outside air. 11 air conditioning system according to claim 2, characterized in that it comprises a reservoir (36) supplied with condensed water at the evaporator (22).
8/ Système de climatisation d'air selon la revendication 1, caractérisé en ce que le fluide réfrigérant est du dioxyde de carbone.8 / air conditioning system according to claim 1, characterized in that the refrigerant is carbon dioxide.
9/ Système de climatisation d'air selon la revendication 1, caractérisé en ce qu'il comporte un système de dosage de l'eau (44) humidifiant l'air extérieur. 9 / air conditioning system according to claim 1, characterized in that it comprises a water metering system (44) humidifying the outside air.
EP06779016A 2006-07-04 2006-07-04 Air conditioning system operating on a supercritical cycle for use in motor vehicles Withdrawn EP2040946A1 (en)

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