US20090314023A1

US20090314023A1 - Heating, Ventilating and/or Air Conditioning System With Cold Air Storage

Info

Publication number: US20090314023A1
Application number: US12/487,534
Authority: US
Inventors: Laurent Labaste Mauhe; Regine Haller; Jean Luc THUEZ; Laurent Delaforge; Abdelmajid Taklanti; Thierry Cheng; Kevin Morvan; Marie Lecollier
Original assignee: Valeo Systemes Thermiques SAS
Current assignee: Valeo Systemes Thermiques SAS
Priority date: 2008-06-19
Filing date: 2009-06-18
Publication date: 2009-12-24
Also published as: EP2136161A1; FR2932875B1; FR2932875A1; EP2136161B1

Abstract

The invention relates to a heating, ventilating and/or air conditioning system with a main air conditioning loop (10) for a refrigerant including at least one compressor (11), a condenser (12), an expansion device (13) and an evaporator (14), a cold storage heat exchanger (21) suitable for storing cold during operation of the compressor (11), and a secondary air-conditioning loop (20 a) comprising the cold storage heat exchanger (21). The secondary air-conditioning loop (20 a) is suitable to cool the evaporator (14) when the compressor (11) is out of operation. The secondary air-conditioning loop (20 a) includes a fluid circulation branch disposed in parallel with a main air conditioning loop (10) common section including at least the evaporator (14). The fluid circulation branch contains a cold production element (21) able to cool the refrigerant toward the evaporator. The invention is particularly dedicated to heating, ventilating and/or air conditioning systems in “Stop and Start” cars.

Description

This invention concerns a heating, ventilation and/or air conditioning system and, in particular, heating, ventilation and/or air conditioning systems that allow storage of cold air.
The invention has an application in the area of heating, ventilation and/or air conditioning systems for motor vehicles with an internal combustion engine. More specifically, the invention has a particularly advantageous application in the area of heating, ventilation and/or air conditioning systems for motor vehicles equipped with an automatic stop and start system for their internal combustion engine. Such a configuration is also known in English under the name “Stop & Start.”
Heating, ventilation and/or air conditioning systems involve a thermodynamic air conditioning loop, usually including a compressor designed to compress and circulate a refrigerant, generally a fluoroethane compound such as the one designated under the name of R134a. The compressor is driven by the vehicle's internal combustion engine by means of a belt connected to the engine crankshaft. The refrigerant in its high pressure gaseous state then traverse a condenser and exchanges heat with ambient air coming directly from the front of the vehicle and/or a fan. The refrigerant comes out of the condenser in its high pressure liquid state. Then, an expander, specifically an escape valve, reduces liquid refrigerant pressure and temperature. The refrigerant then goes through an evaporator In which it exchanges heat with air assigned to the thermal treatment of the vehicle interior. To do this, low temperature evaporation of the refrigerant requires an energy input which is provided by the air going through the evaporator. Thus the air for the thermal treatment of the vehicle interior is cooled. Moreover, the refrigerant is vaporized under low pressure, at least partially. It is then introduced in its gaseous state into the compressor to run again through the thermodynamic air conditioning loop.
Because of the mechanical link between compressor and internal combustion engine, it is evident that heating, ventilation and/or air conditioning systems can only operate if the internal combustion engine is working, as the thermodynamic air conditioning loop is stopped when the engine is turned off.
Now, with the current widespread use of hybrid propulsion in motor vehicles, situations in which the internal combustion engine stops tend to increase, resulting in negative consequences on the passengers' comfort. The comfort level in the car interior decreases every time the vehicle's internal combustion engine stops and the feeling of discomfort may be perceived as feeling hot or cold.
This invention seeks to remedy the above-mentioned problems. More specifically, it targets the micro hybridization case specifically illustrated by the “Stop & Start” system, in which the internal combustion engine shuts down when the vehicle stops for relatively short periods and during which it is advisable to maintain passenger comfort by ensuring the continued operation of the heating, ventilation and/or air conditioning system.
An initial solution for this problem consists in using storage evaporators such as those described in the French patent applications FR2847973 and FR2878613. Storage evaporators contain a phase change material (PCM) that can modify their state during normal operation of the thermodynamic air conditioning loop. Through the phase change, the phase change material allows storing heat energy in the form of latent heat from solidification or phase change. This thermal energy is returned in the form of cold to the conditioned air when the compressor stops operating after the internal combustion engine is turned off; the phase change material returns to its initial state by releasing stored heat. The phase change materials most traditionally used are paraffins, with a melting point, for instance, between 5 and 12° C.
This storage evaporator technology does however have a certain number of drawbacks.
It should be specifically noted that the time range of these devices is relatively limited, generally less than one minute, so that the quantity of phase change material taken on is limited by the space allowed in the internal volume of the evaporators and by the space allowed to the heating, ventilation and/or air conditioning system in the vehicle. And increasingly this space is being decreased by automotive manufacturers.
Another drawback is represented by an increased loss of charge in the air circulation circuit for air conditioning. As the pipes of the storage evaporators are larger than those of traditional evaporators, this creates a decrease of the section where air flows, which can only be compensated by using a more powerful fan motor unit. Such a component is more expensive and it is uses a significantly greater amount of electric energy.
Finally, it should also be noted that using storage evaporators to ensure air conditioning function impacts on the architecture of the heating, ventilation and/or air conditioning installation which integrates the components of the heating, ventilation and/or air conditioning system.
Furthermore, the current tendency toward a certain standardization of the architecture of heating, ventilation and/or air conditioning equipment, heating, ventilation and/or air conditioning systems and their integrated components. The use of a storage evaporator for a part of a vehicle platform involves therefore a loss in terms of standardization and a multiplication of references of heating, ventilation and/or air conditioning and heating equipment, ventilation and/or air conditioning systems.
To remedy these drawbacks these days a second solution is used, based on separating evaporation and cold storage functions and putting in place two thermodynamic air conditioning loops. Therefore, on one hand there is a traditional main thermodynamic loop that allows generation of frigories in an evaporator when the compressor is in operation and, on the other hand, a secondary loop that allows storing these frigories in a cold storage heat exchanger and returning them by cooling the evaporators with the cold stored in the cold storage heat exchanger when the compressor is not operating. Such a system is specifically described in the application for French patent FR2861163.
Moreover a double loop heating, ventilation and/or air conditioning system is also known, in which a main thermodynamic air conditioning loop, in addition to the usual heating, ventilation and/or air conditioning system components, includes a cold storage heat exchanger arranged serially with the evaporator downstream from the expansion member. During the compression/expansion thermodynamic cycle the refrigerant circulates in the main thermodynamic loop successively cools the phase change material in the cold storage heat exchanger, and the conditioned air through the evaporator. Then, when the compressor is stopped, a secondary thermodynamic loop is activated. The secondary thermodynamic loop includes the cold storage heat exchanger, the evaporator and a circulating pump. When it flows through the secondary thermodynamic loop, the refrigerant cools as it comes in contact with the phase change material, which then releases the heat energy it had stored and flows through the evaporator to cool the conditioned air, to the extent of the latent solidification heat stored in the phase change material. The application for French patent FR2836421 describes one such system.
In this known double loop heating, ventilation and/or air conditioning system, the secondary thermodynamic loop consists of two sections connected in parallel on the main thermodynamic loop. A first section which includes the circulating pump is placed between the outlet of the cold storage heat exchanger and the evaporator inlet, and a second section, which includes a first valve, is placed between the outlet of the evaporators and the inlet for the cold storage heat exchanger. Furthermore, a second valve is also placed in the main loop between the cold storage heat exchanger and the evaporator. The valves are configured in such a way so when the compressor is operating, the first valve is closed and the second valve is open, whereas, when the compressor is turned off, the second valve is closed and the first valve is open.
It can be seen that this heating, ventilation and/or air conditioning system described in the application for French patent FR2836421 is somewhat complex because of the presence of two parallel sections in the main thermodynamic loop to obtain the second thermodynamic air conditioning loop and two valves that must be perfectly calibrated to allow proper operation of the system, whether the compressor is turned on or off.
So the purpose of the invention is to offer a simpler to produce heating, ventilation and/or air conditioning system with two thermodynamic air conditioning loops.
This goal is achieved, in accordance with the invention, through a heating, ventilation and/or air conditioning system with a main thermodynamic air conditioning loop which includes at least a compressor, a condenser, an expansion member, an evaporator, a cold storage heat exchanger capable of storing cold during compressor operation, a secondary thermodynamic air conditioning loop that integrates the cold storage heat exchanger and assigned to cool the evaporators when the compressor is not in operation.
The secondary air conditioning loop includes a fluid circulation section placed in parallel with the main thermodynamic air conditioning loop on a common section including at least the evaporator, the fluid circulation section which contains a cold-producing element capable of cooling the refrigerant going to the evaporator.
Thus the secondary loop of the heating, ventilation and/or air conditioning system according to the invention only includes a single section instead of two as in the case of the above-mentioned French patent application.
According to the first implementation method, the cold-producing element consists of a cold storage heat exchanger.
In this implementation method, the cold storage heat exchanger has the role of cold spot assigned to cool the refrigerant before it flows into the evaporator. For this purpose, the fluid circulation section needs a refrigerant circulation pump.
Accordingly, the fluid circulation section includes a refrigerant expander located upstream from the cold storage heat exchanger and an expander bypass device. Sub-cooling of the phase change material is also obtained, which gives improved storage time frames.
The secondary thermodynamic air conditioning loop preferably contains a switching device, specifically made in the shape of three way valve with at least a first position in which the switching device allows the refrigerant to flow through the expander placed upstream from the cold storage heat exchanger and stops the refrigerant from flowing through the expander bypass section, and a second position in which the switching device stops the flow of the refrigerant through the expander and allows the refrigerant to flow into the expander bypass section.
In order to ensure the flow of the refrigerant through the fluid circulation section of the secondary loop, the invention requires the expansion device of the main air conditioning loop to be an ejector with a low pressure inlet connected to the fluid circulation section.
According to a second implementation method, the cold producing element consists of a secondary expander. The secondary thermodynamic air conditioning loop therefore includes a secondary compressor.
The section common to the main and secondary thermodynamics air conditioning loops includes, in addition to the evaporator, the secondary compressor and the cold storage heat exchanger.
The secondary thermodynamic air conditioning loop preferably includes a switching device, specifically made in the form of a three-way valve, with at least a first position in which the switching device allows the refrigerant to flow through the secondary compressor located upstream from the cold storage heat exchanger and it stops the refrigerant from flowing into a section that bypasses the secondary compressor and a second position in which the switching device stops the refrigerant from flowing through the secondary compressor, allowing refrigerant to flow into the section that bypasses the secondary compressor.
In this implementation method, the cold storage heat exchanger works as a condenser in the secondary thermodynamic de air conditioning loop.
According to this invention, the secondary thermodynamic air conditioning loop requires a control device, specifically in the form of a three way valve, with a first position in which the control device allows storing cold in the storage heat exchanger and a second position in which the control device allows returning the stored cold from the cold storage heat exchanger.

This invention will be better understood after reading the description below of the implementation variants in relation with the figures in the attached tables, including, but not limited to

- FIG. 1 a is the outline of the first implementation method of a heating, ventilation and/or air conditioning system according to the invention that operates when the compressor is operating,

FIG. 1 b is the outline of the first implementation method of the heating, ventilation and/or air conditioning system in FIG. 1 a that operates when the compressor is shut down,

FIG. 2 a is the outline of a second implementation method of a heating, ventilation and/or air conditioning system according to the invention that operates when the compressor is operating, and

FIG. 2 b is the outline of a second implementation method of the heating, ventilation and/or air conditioning system in FIG. 2 a which operates when the compressor is turned off.

FIGS. 1 a and 1 b show a heating, ventilation and/or air conditioning system according to a first implementation method, which includes a main thermodynamic air conditioning loop 10 including, in the direction of refrigerant flow, a compressor 11, a condenser 12, an expansion device 13, an evaporator 14 and a tank 15.
The compressor 11 is driven by the internal combustion engine, not illustrated, of a motor vehicle. The refrigerant, for instance R134a, is brought by the compressor 11 to the high pressure and high temperature gaseous state. The refrigerant then undergoes a stage change when passing through the condenser 12 and exchanges calories with the ambient air from the front of the vehicle, drawn or not, in order to be cooled. When it comes out of the condenser 12, the refrigerant is then in its liquid state at high pressure.
Pressure and temperature of the refrigerant in its liquid form are lowered when it flows through expansion device 13, such as an expander or, as in the example shown in FIGS. 1 a and 1 b, an ejector. Then refrigerant temperature drops when it passes through the evaporator 14. The evaporator 14 is traversed by a flow of air that can be distributed into the vehicle's interior.
The liquid and gaseous states of the refrigerant that come out of the evaporator 14 are separated by the tank 15, the gaseous state is returned to the compressor 11 to be again compressed, whereas the liquid state flows through a storage loop assigned to store cold in a storage heat exchanger capable of storing cold.
The cold stored in the heat exchanger will be further returned to the refrigerant in order to extend the air conditioning function in the vehicle interior after the compressor is turned off following a shutdown of the internal combustion engine.
FIG. 1 a presents a first implementation method of the heating, ventilation and/or air conditioning system in which the compressor 11 is operating.
The liquid and gaseous states of the refrigerant coming out of the evaporator 14 are separated by the Tank 15, with the gaseous states being returned to the compressor 11 to be compressed again, whereas the liquid state flows into a storage loop assigned to storing cold in a storage heat exchanger capable of storing cold, 10 From the tank 15, the refrigerant under low pressure in its liquid state is directed by a first three way valve 22 into the storage loop 20.
Storage loop 20 consists also of a secondary thermodynamic air conditioning loop 20 a. Storage loop 20 includes, in the refrigerant circulation direction, an expander 23, a storage heat exchanger 21, a second three-way valve 24, an electric circulating pump 25 and a one-way valve 26.
The secondary thermodynamic air conditioning loop 20 a consists specifically of the storage heat exchanger 21, a second three way valve 24, an electric circulating pump 25 and the one-way valve 26.
The secondary thermodynamic air conditioning loop 20 a therefore consists of a fluid circulating section located on a common section in parallel with the main thermodynamic main air conditioning loop 10. The secondary thermodynamic air conditioning loop 20 a and the main thermodynamic air conditioning loop 10 have in common at least the evaporator 14. According to the implementation example in FIGS. 1 a and 1 b, both the main thermodynamic air conditioning loops 10 and secondary thermodynamic air conditioning 20 a require tank 15 in common. The main 10 and secondary 20 a thermodynamic air conditioning loops can be isolated from each other by means of the second three way valve 24
The first three way valve 22 is connected with the storage heat exchanger 21 by means of two circulation sections arranged in parallel. One of the circulation sections includes an expander 23 and the other section constitutes a bypass section of expander 23.
The first three way valve 22 constitutes a switching device between the circulation section containing expander 23 and the bypass section of expander 23.
In this first operating mode of the first implementation method, as presented in FIG. 1 a, the first three way valve 22 10 occupies a first position in which it opens circulation of the refrigerant from the tank 15 to the storage heat exchanger 21 through the expander 23 and the appropriate circulation section. The first position is also such that the three way valve 22 closes the bypass section of expander 23.
Expander 23 operates as a second pressure stage for the refrigerant whose temperature has dropped to a figure compatible with the solidification temperature of the phase change material (PCM) of the cold storage heat exchanger 21.
After flowing through the expander 23, the refrigerant enters into the cold storage heat exchanger 21 After it flows through it, the refrigerant is at a temperature that allows the phase changing fluid (PCM) to change phase and take calories from the refrigerant. This step constitutes the cold storage stage in the cold storage heat exchanger 21.
After crossing the cold storage heat exchanger 21 and solidifying the phase change material contained in the cold storage heat exchanger 21, the refrigerant taken by means of the second three way valve 24, set in the first position, from the cold storage heat exchanger 21 to a low pressure inlet of the expansion device 13.
The expansion device 13 according to the implementation example in FIGS. 1 a and 1 b is an ejector. The ejector also ensures the circulation of the refrigerant in the storage loop 20.
FIG. 1 b shows the first implementation method of the heating, ventilation and/or air conditioning system in which the compressor 11 is not in operation. In this state, the compressor (11) is no longer driven by the vehicle's internal combustion engine.
Comfort in the vehicle's interior is maintained by the storage loop 20 and more specifically by an adapted configuration of the storage loop 20 which constitutes the secondary thermodynamic air conditioning loop 20 a the operation of which will be described in reference to FIG. 1 b.
The secondary thermodynamic air conditioning loop 20 a is defined by the first and second three way valves 22 and 24, being placed in the second positions.
The secondary thermodynamic air conditioning loop 20 a includes a fluid circulation section set on a common section in parallel with the main thermodynamic air conditioning loop. According to the implementation example, this common section consists, specifically, of the evaporator 14.
In this second operating mode of the first implementation method, as shown in FIG. 1 b, the secondary thermodynamic air conditioning loop 20 air conditioning secondary 20 a is such that the first three way valve 22 stops the flow of the refrigerant from the tank 15 to the expander 23. The first three way valve 22 therefore occupies a second position in which it opens the flow of the refrigerant from the tank 15 to the storage heat exchanger 21 by means of the bypass expander section 23 and closes the circulation section where the extender 23 is located.
Moreover, the secondary thermodynamic air conditioning loop 20 a is such that the second three way valve 24 stops the flow of the refrigerant from the cold storage heat exchanger 21 to the low pressure inlet of expansion device 13. The second three way valve 24 then takes a second position in which it opens the flow of the fluid that refrigerates the cold storage heat exchanger 21 toward the evaporator 14 by means of the electric circulation pump 25 and the one way valve 26.
When the secondary thermodynamic air conditioning loop 20 a is in operation, the expander 23 is bypassed by the first three way valve 22 so that the fluid circulation section essentially consists of the cold storage heat exchanger 21 connected with the electric circulating pump 25 by the second three way valve 24. The one-way valve 26 is located at the outlet of the electric circulating pump 25.
So, when the compressor 11 is not operating, the cold storage heat exchanger 21 is used as a cold spot to cool the refrigerant that circulates in the secondary thermodynamic air conditioning loop 20 a. The cold storage heat exchanger 21 therefore operates as an element to produce cold and is capable of cooling the refrigerant going into the evaporator 14. So evaporator 14 can continue for a certain period of time to ensure its function of cooling the air flow into the vehicle's interior and thus maintain passenger comfort.
In this first implementation method, the second three way valve 24 which constitutes a control device with a first position in which the second three way valve 24 allows storing cold in the cold storage heat exchanger 21 and a second position in which the second three way valve 24 allows the cold stored in the cold storage heat exchanger 21 to be returned.
FIGS. 2 a and 2 b show a heating, ventilation and/or air conditioning system in accordance with a second implementation method which includes a main thermodynamic air conditioning loop 10′ which involves, in the direction of refrigerant flow, a compressor 11, a condenser 12, an expansion device 13′, an evaporator 14 and a tank 15.
The main thermodynamic air conditioning loop 10 therefore includes the traditional components of a heating, ventilation and/or air conditioning system.
In the described example of this second implementation method, the expansion device 13 consists of an expander, in particular a thermostatic expander.
The main thermodynamic air conditioning loop 10′ also includes, in the direction of refrigerant flow and located between the evaporator 14 and the tank (15), in the direction of refrigerant flow, a third three way valve 16, a secondary electric compressor 17 and a cold storage heat exchanger 18.
The cold storage heat exchanger 18 in the implementation example in FIGS. 2 a and 2 b is similar to the storage heat exchanger 21 in FIGS. 1 a and 1 b. Consequently, the characteristics of the storage heat exchanger 21 will be, unless otherwise indicated, also those of storage heat exchanger 18.
The third three way valve 16 is connected with the storage heat exchanger 18 by two circulation sections set in parallel. One of the circulation sections includes the secondary electric compressor 17 and the other section is a section that bypasses the secondary electric compressor 17. In a particularly advantageous fashion, the secondary electric compressor 17 has a low cylinder capacity.
The third three way valve 16 constitutes a switching device between the circulation section that includes the secondary electric compressor 17 and the section that bypasses the secondary electric compressor 17. Additionally the fourth three way valve 27 is located between the expansion device 13 and the evaporator 14.
The heating, ventilation and/or air conditioning system in FIGS. 2 a and 2 b also contains a secondary thermodynamic air conditioning loop 20′a.
The secondary thermodynamic air conditioning loop 20′a consists of a section for refrigerant circulation that goes from the tank 15 to the fourth three way valve 27. Upstream from the fourth three way valve 27, the secondary thermodynamic air conditioning valve 20′a includes a secondary expander 23′, in particular a thermostatic expander.
The secondary thermodynamic air conditioning loop 20′a is located in parallel on a common section with the main thermodynamic air conditioning loop 10′.
The secondary thermodynamic air conditioning loop 20′a and the main thermodynamic air conditioning loop are located in parallel with one another.
However they include a common section commune, the loop portion that includes the evaporator 14 and the cold storage heat exchanger 18.
The secondary thermodynamic air conditioning loop 20′a consists also of the fourth three way valve 27, the evaporator 14, the third three way valve 16, the secondary electric compressor 17, and the cold storage heat exchanger 18.
The main 10 and secondary 20′a thermodynamic air conditioning loops can be insulated one from the other by means of the fourth three way valve 27.
A first operating mode of the second implementation method, as shown in FIG. 2 a, is with the compressor 11 in operation. Vehicle interior comfort is ensured in the traditional way by the main thermodynamic air conditioning loop 10′.
In this operating mode, the third three way valve 16 occupies a first position in which it opens the flow of the refrigerant from the evaporator 14 to the storage heat exchanger 18 through the section that bypasses the secondary compressor 17. The first position of the third three way valve 16 is also such that the third three way valve 16 closes the circulation section in which the secondary compressor 17 is located.
Moreover, the fourth three way valve 27 occupies a first position in which it opens the flow of the refrigerant from the expander 13 to the evaporator 14. The first position of the fourth three way valve 27 is also such that the fourth three way valve 27 closes the secondary thermodynamic air conditioning loop 20′a.
As illustrated in FIG. 2 a, the phase change material of the cold storage heat exchanger 18 cools when in contact with the refrigerant coming out of the evaporator 14. And stores cold which will be further used in the event the compressor is turned off 11.
A second operating mode of the second implementation method according to the provisions of FIG. 2 b is such that the compressor 11 is not operating. Comfort in the vehicle interior is then ensured by the secondary thermodynamic air conditioning loop 20′a, in accordance with the operating schematics illustrated in FIG. 2 b.
In this operating mode the third three way valve 16 is set in a second position in which it stops the direct flow of the refrigerant from the evaporator 14 to the cold storage heat exchanger 18. The third three way valve 16 therefore occupies the second position in which it opens refrigerant circulation from the evaporator 14 of the cold storage heat exchanger 18 through the section containing the secondary compressor 17. The secondary compressor 17 is then started.
Additionally, the fourth three way valve 27 is set in a second position in which it stops the refrigerant 20 from flowing from the expander 13 to the evaporator 14. The second position of the fourth three way valve 27 is also such that the fourth three way valve 27 opens the secondary thermodynamic air conditioning loop 20′a. Therefore it allows the refrigerant to flow between the secondary expander 23′ and the evaporator 14.
The secondary thermodynamic air conditioning loop 20′a operates as a traditional thermodynamic air conditioning loop. In this configuration, the cold storage heat exchanger 18 serves as a condenser for the refrigerant flowing out of the secondary compressor 17. The refrigerant in its liquid state coming from the cold storage heat exchanger 18 is expanded and cooled by the secondary expander 23′ before flowing into the evaporator 14. The secondary expander 23′ therefore operates as a cold producing element capable of cooling the refrigerant flowing into the evaporator 14. The air conditioning effectiveness of the secondary thermodynamic air conditioning loop 20′a is limited by the quantity of cold stored in the cold storage heat exchanger 18.
In this second implementation method, the fourth three way valve 27 constitutes a control device with a first position in which the fourth three way valve (27) allows storing cold in the cold storage heat exchanger 18 and a second position in which the fourth three way valve 27 allows the return of the cold stored in the cold storage heat exchanger stockage 18.
This invention and the implementation examples previously described use a refrigerant. The refrigerant may be a fluoroethane compound, specifically R134a, or any other alternative fluids, either natural or synthetic, specifically carbon dioxide.
Obviously, the invention is not limited to the implementation methods described above and provided solely as examples and it encompasses other variants that a professional may envisage within the scope of the claims and specifically any combinations of the various implementation methods previously described.

Claims

1. A heating, ventilation and/or air conditioning system, said system comprising:

a main thermodynamic air conditioning loop (10; 10′) for the circulation of a refrigerant including at least a compressor (11), a condenser (12), an expansion device (13; 13′) and an evaporator (14),

a cold storage heat exchanger (21, 18) capable of storing cold refrigerant when the compressor is operating (11),

a secondary thermodynamic air conditioning loop (20 a; 20′a) that integrates the cold storage heat exchanger (21; 18), the secondary thermodynamic air conditioning loop (20 a; 20′a) assigned to cool the evaporator (14) when the compressor (11) is not operating,

characterized by a secondary thermodynamic air conditioning loop (20 a; 20′a) that includes a fluid circulation section set on a common section in parallel with the main thermodynamic air conditioning loop (10; 10′) including at least the evaporator (14), the fluid circulation section including a cold producing element (21; 23′) that can cool the refrigerant going into the evaporator (14).

2. A system according to claim 1, in which the cold producing element is constituted by the cold storage heat exchanger (21).

3. A system according to claim 2, in which the fluid circulation section includes a refrigerant circulating pump (25).

4. A system according to either claim 2, in which the secondary thermodynamic air conditioning loop (20 a) includes a switching device (22) with at least a first position in which the switching device (22) allows the refrigerant to flow through an expander (23) located upstream from the cold storage heat exchanger (21) and stops the flow of the refrigerant into a bypass section of the expander (23), and a second position in which the switching device (22) stops the flow of the refrigerant through the expander (23) and allows the refrigerant to flow into the bypass section of the expander (23).

5. A system according to claim 4, in which the switching device is a three way valve (22).

6. A system according to claim 2, in which the expansion device of the main air conditioning loop is an ejector (13).

7. A system according to claim 6, in which the fluid circulation section is connected to a low pressure inlet of the ejector (13).

8. A system according to claim 1, in which the cold producing element is constituted of a secondary expander (23′).

9. A system according to claim 8, in which the secondary thermodynamic air conditioning loop (20′a) includes a secondary compressor (17).

10. A system according to claim 8, in which the secondary thermodynamic air conditioning loop (20′a) involves a switching device (16) with at least a first position in which the switching device (16) allows the refrigerant to flow through the secondary compressor (17) located upstream from the cold storage heat exchanger (18) and stops the flow of the refrigerant into a bypass section of the secondary compressor (17), and a second position in which the switching device (16) stops the flow of the refrigerant through the secondary compressor (17) and allows the refrigerant to flow into the bypass section of the secondary compressor (17).

11. A system according to claim 10, in which the switching device is a three way valve (16).

12. A system according to claim 1, in which the secondary thermodynamic air conditioning loop (20 a, 20′a) involves a control device (24, 27) with a first position in which the control device (24, 27) allows cold storage in the cold storage heat exchanger (21, 18) and a second position in which the control device (24, 27) allows the recovery of the cold stored in the cold storage heat exchanger (21, 18).

13. A system according to claim 12, in which the control device is a three way valve (24, 27).

14. A system according to either claim 3, in which the secondary thermodynamic air conditioning loop (20 a) includes a switching device (22) with at least a first position in which the switching device (22) allows the refrigerant to flow through an expander (23) located upstream from the cold storage heat exchanger (21) and stops the flow of the refrigerant into a bypass section of the expander (23), and a second position in which the switching device (22) stops the flow of the refrigerant through the expander (23) and allows the refrigerant to flow into the bypass section of the expander (23).

15. A system according to claim 9, in which the secondary thermodynamic air conditioning loop (20 a) involves a switching device (16) with at least a first position in which the switching device (16) allows the refrigerant to flow through the secondary compressor (17) located upstream from the cold storage heat exchanger (18) and stops the flow of the refrigerant into a bypass section of the secondary compressor (17), and a second position in which the switching device (16) stops the flow of the refrigerant through the secondary compressor (17) and allows the refrigerant to flow into the bypass section of the secondary compressor (17).