DE102004023834A1 - Expansion device for a refrigerant - Google Patents

Abstract

The invention relates to an expansion device (16) for a refrigerant, in particular expansion device (16) for controlling the high-pressure level of a refrigerant circuit (10) of an air conditioning system. DOLLAR A According to the invention it is proposed that the expansion device (16) comprises at least one expansion valve (26) and an expansion machine (36). DOLLAR A Furthermore, the invention relates to an air conditioner, in particular an air conditioner for a motor vehicle with a refrigerant circuit (10) having such an expansion device (16).

Description

The The present invention relates to an expansion device for a refrigerant, in particular an expansion device for regulating the high pressure level a refrigerant circuit an air conditioner, according to the preamble of claim 1. The other The present invention relates to an air conditioner with such Expansion device.

The standard version of an air conditioning system generally consists of an evaporator, a condenser or gas cooler, an expansion valve, a compressor and possibly an internal heat exchanger. In particular, when the refrigerant CO _{2 is} used, at least under some environmental conditions, a supercritical operation of the refrigerant and the refrigerant circuit of the air conditioner is required. This means that in the condenser, the refrigerant is not condensed, but that gas is only cooled in the supercritical state. For this reason, the heat exchanger, which operates as a condenser in conventional refrigeration systems and is called in supercritical operation of the refrigeration system and gas cooler.

In refrigeration systems with refrigerants which, due to their thermodynamic properties, release the heat in the supercritical range, the pressure during the heat release can be set independently of the temperature. In order to use this, compared to refrigerants with heat in the wet steam area, additional degree of freedom, typically adjustable expansion valves are used. Thus, in the case of the refrigerant CO _2, such an expansion valve regulates the high-pressure level of the refrigeration cycle, so that the efficiency of the refrigeration system or the refrigerating capacity of the refrigerant circuit can be optimally adjusted.

A Correctional Facility the sketched standard version a refrigeration system For example, it is the expansion valve through a work-performing Expansion device to replace a so-called expansion machine. In this way, the expansion process of the refrigeration cycle is designed to be more effective and at the same time gaining expansion work. The relaxation energy of the refrigerant is thus transformed into mechanical work and for others, downstream processes made usable.

Out the prior art, various technical solutions are known to practically realize an expansion machine.

The DE 198 41 686 A1 discloses a compressor refrigeration machine in which a refrigerant is compressed to supercritical pressure in a compressor, then cooled by heat exchange with the air by means of a gas cooler and then supplied to an expansion machine. As an expansion or expansion machine for the cooled refrigerant, which is at critical pressure level, is in the device of the DE 198 41 686 A1 a gear motor used, which has a housing with at least two mutually rotatable gears.

From the DE 100 13 191 C1 is an air conditioner, in particular an air conditioner for motor vehicles is known, whose refrigerant circuit comprises a gear machine with a helical toothing, which serves as an expansion machine for the supercritical refrigerant. The gear machine generates energy during the expansion process of the refrigerant, inter alia by recovering the volume change work, which in turn can be used in the refrigerant circuit for compressing the refrigerant. The air conditioning of DE 100 13 191 C1 is configured such that the refrigerant carbon dioxide (CO ₂ ) in the refrigerant circuit is brought from a supercritical state to a wet steam state.

Independent of the selected technology The regulation requirements of the expansion machine make a special Challenge.

One Another problem is that an expansion machine a Safety function Has. The expansion machine is said to be at too extreme loads of Systems, enable that System to bring it back to a stable state or, if necessary safely shut down the system. These extreme conditions, the far away from the normal operating conditions, therefore be taken into account in the design of the expansion machine, what a optimal design of the expansion machine, especially in normal operation makes it hard.

Advantages of invention

The expansion device for a refrigerant according to the invention, in particular such an expansion device for regulating the high-pressure level of a refrigerant circuit of an air conditioning system, has at least one expansion valve and an expansion machine. By this combined structure of the expansion device is part of the heavy control tasks of the expansion process, and also the security tasks of Transfer expansion machine from the machine to the expansion valve. The expansion machine thus has only the task of energy recovery, and to provide the recovered energy in the appropriate form for further use. The setting of the high pressure as well as the safety function is taken over by the expansion valve of the expansion device.

On this way it is possible an expansion device for a refrigerant operate such that both the setting of the high pressure level as well as providing the recovered energy in each other almost independent and thus optimal feasible is. For example, the speed of the expansion machine be optimized for energy use and conversion without that the high pressure level to be set must be taken into account.

By in the subclaims listed Features are advantageous developments of the expansion device according to the invention possible.

In an advantageous embodiment the expansion device according to the invention are the expansion machine and the adjustable expansion valve in Row to each other in the refrigerant circuit of Air conditioning arranged.

In an alternative, advantageous embodiment of the expansion device according to the invention Both the variable expansion valve and the expansion machine are parallel to each other in the refrigerant circuit the air conditioning arranged. The parallel connection of expansion valve and expansion machine allows It also simplifies the sizing of the expansion machine. This can in the case of parallel connection only for the usual or optimal mass flow are designed, wherein the expansion valve would be used if increased mass flows would occur.

A such parallel connection of the essential components of the expansion device also means a non-negligible in terms of safety of the refrigeration system Advantage. Thus, in case of failure of the expansion machine, the expansion valve enter an "emergency stop mode" and despite inoperable Expansion machine ensure a safe shutdown of the plant.

In advantageous embodiments the expansion valve is a controllable valve with which the High pressure level of the refrigerant circuit can regulate. It can be both external and internal act regulated valve. The expansion valve can be an electric operated valve or a mechanically or thermally controlled Be a valve. A possible Embodiment of the Expansion valve which can be used, consists in an overflow valve, which opens at a given mass flow of the coolant.

In a particularly advantageous embodiment of the expansion device according to the invention, are their adjustable expansion valve and the expansion machine summarized in a structural unit to a compact module. One such module leaves integrate easily into appropriate refrigeration circuits.

There the regulation of the high pressure level of the refrigerant circuit substantially through the expansion valve has the expansion machine only the task, the recovered To provide energy in a suitable form. So can the drive shaft the expansion machine, for example, directly to the drive shaft of the refrigerant compressor be coupled or coupled. This is particularly advantageous Further development of the claimed expansion device, as the Speed of the expander expansion machine independent of the regulation of the high pressure selected can be. An adaptation of the speed of the expansion machine to the speed of the compressor can thus be done freely.

If the expansion machine advantageously a pre or densification device for the refrigerant drives, the volume flow generated can be set as desired, since he is no longer aware of the regulation of the high pressure level of the refrigerant being affected. The task of regulating the expansion machine for setting the high pressure level in the refrigerant circuit and the Provision of recoverable mechanical energy in suitable form are in an advantageous manner no longer linked together. Because these two tasks are at the state of the art of expansion Technology different demands on the speed of the expansion machine have been, have been complex solutions, such as a controllable transmission to achieve an additional Degrees of freedom.

An advantageous development of the expansion device according to the invention results in the event that the expansion machine of the expansion device with an electric machine, in particular with an electric generator operatively connected or operatively connected. When the recovered energy is to be converted into electrical energy by means of a generator, the claimed expansion device is of great use. The expansion valve of the expander can set the optimum high pressure while the characteristic of the expansion machine, for example, the characteristic of a conventional motor vehicle generator corresponds. The regulation of the output voltage of the generator is greatly simplified by such an arrangement. The freely selectable speed of the expansion machine of the claimed expansion device thus allows a constant output voltage at the generator. In addition, required security features can be optimized.

A particularly advantageous embodiment the device according to the invention results from the fact that the expansion device or at least the expansion machine of the expansion device in a structural Unit with an electric machine, for example a generator is designed. So it is possible both machines, d. H. both the expansion machine, as well as the electric machine in a common housing, which is typically forms a hermetic unit to arrange.

With the claimed, inventive expansion device let yourself advantageously an air conditioner, in particular a dynamically operated Air conditioning for to develop a motor vehicle. By the division of tasks of the components of Expansion device of the refrigeration cycle the air conditioning leaves Both the regulation of the high pressure level of the refrigerant and thus the efficiency or the cooling capacity of the refrigeration cycle optimize as well as in addition Energy through the expansion process by means of an expansion machine win. The additional energy thus gained can be advantageously for the operation of other components of the air conditioner or the refrigeration cycle deploy.

In particular, for a refrigerant which releases the heat in the supercritical region, as is the case with the refrigerant CO _2, for example, thus results in an advantageous development of the refrigeration cycle and a connected to such a refrigeration cycle air conditioning.

The Inventive expansion device allows Thus, to simplify the regulation of an expansion machine or such a regulation is possible close.

Further Advantages and features of the expansion device according to the invention or an air conditioner of the invention result with such an expansion device in the refrigerant circuit from the following description of some embodiments.

drawings

In the drawing are three embodiments the expansion device according to the invention or examples of three refrigerant circuits using of expansion devices according to the invention represented, which are explained in more detail in the following description should. The figures of the drawings, their description and the claims contain numerous features in combination. An expert will To look at these features individually and to further, meaningful combinations summarized, which are thus to be regarded as also disclosed.

It shows

1 a schematic representation of the refrigerant circuit of an air conditioner,

2 A first embodiment of a arranged in a refrigerant circuit expansion device,

3 A second embodiment of an expansion device according to the invention and the associated refrigerant circuit of an air conditioner,

4 , a further embodiment of an expansion device according to the invention and the associated refrigerant circuit of an air conditioner.

description the embodiments

The in 1 shown in principle refrigerant circuit 10 An air conditioner has a compressor 12 , a condenser or gas cooler 14 , an expansion device 16 and an evaporator 18 on that via appropriate connecting means 20 are interconnected and form a closed refrigerant circuit.

The components of this circuit are operated in the manner of a compression refrigeration cycle. Here, first, a compression of a refrigerant, such as the refrigerant CO ₂ by a compressor, the so-called air compressor or simply compressor, carried out to increase the internal energy of the refrigerant. The compressed refrigerant is then cooled in a condenser or condenser by heat exchange. In the case of refrigerants which release the heat in the supercritical range, as is the case, for example, with the refrigerant CO ₂ , the refrigerant in the condenser is not liquefied but only removed as gas in the supercritical state cools. For this reason, this heat exchanger 14 when using the supercritical operation of the refrigerant referred to as a gas cooler. Subsequently, the refrigerant thus cooled by means of an expansion device 16 extended to a lower pressure while continuing to cool. The expansion device 16 is usually an evaporator 18 downstream, which is operated as a heat exchanger to transfer the released refrigerant of the refrigerant to another medium. This other medium, which interacts with the cold, expanded refrigerant via the evaporator, may be, for example, air which is supplied to a vehicle heating or cooling system (air conditioning system).

By the control of the throttling at the expansion means of the refrigerant circuit can the pressure on the high pressure side of the thermodynamic cycle be controlled or regulated so that the specific cooling capacity the air conditioning in desired Way can be varied. So it is possible to have a maximum effective Achieve performance index by the pressure of the high pressure side of the thermodynamic cycle (high pressure level) depending from the temperature at the gas cooler outlet or the ambient temperature is adjusted in an adapted manner.

Especially in refrigeration systems with refrigerants, because of their thermodynamic properties the heat in the supercritical Range release, the high pressure level in the heat release independently be set by the temperature. To this, to refrigerants with heat dissipation in the wet steam area additional To use the degree of freedom in an advantageous manner can be and / or adjustable expansion devices are used.

2 shows a first embodiment of a specific refrigerant circuit for an air conditioner using an expansion device according to the invention 16 ,

The refrigerant circuit 10 a CO ₂ air conditioning according to 2 has a compressor 12 on the example, electrically operated or can be driven via corresponding coupling elements of the internal combustion engine of a motor vehicle. In the compressor 12 First, a compression of the refrigerant, in the case described CO ₂ , carried out in order to increase the internal energy of the refrigerant. In the flow direction after the compressor 12 is a separator, especially an oil separator 20 provided, which serves to deposit the oil residues contained in the gaseous refrigerant and these via appropriate connection means 22 for example, the compressor again 12 to provide for lubrication.

The compressed and optionally purified refrigerant is in a downstream condenser or gas cooler 14 cooled by a heat exchange and is doing a portion of its internal heat energy to the air conditioning, such as a vehicle from, so that the temperature of the refrigerant drops and this possibly liquefied. If a transcritical refrigerant, such as CO _{2, is} used as refrigerant, then the refrigerant in the gas cooler 14 not condensed but only cooled, so that one does not speak in this case of a condenser but of a gas cooler.

To further reduce the temperature of the refrigerant is in the refrigerant circuit 10 according to 2 an internal heat exchanger 24 provided, which makes it possible to further cool the compressed, cooled refrigerant by means of the returning and already expanded and cooled refrigerant.

The compressed refrigerant is now an expansion device 16 supplied and expanded in this to a lower pressure level. The expansion device according to the invention 16 at least consists of a regulated expansion valve 26 and an expansion machine 36 , In the embodiment according to 2 are the expansion valve 26 and the expansion machine 36 in series with each other in the cooling circuit 10 switched the refrigerant. The expansion valve 26 is a controllable valve, which can release a desired opening cross-section through a corresponding position of the throttle body of the valve and thus the pressure level on the high pressure side of the refrigerant circuit 10 certainly. The expansion valve 26 For example, it may be an electromagnetically actuated valve or else a purely mechanically controlled valve or even a thermally regulated valve. This can be both an external, as well as an internally regulated valve. be. The adjustable expansion valve 26 Downstream is an expansion machine 36 , which can be formed in principle by any work expansion device.

When Expansion machines are particularly conceivable and advantageous, so-called Gear machines, which effectively implement the expansion energy allow in mechanical work. Over a corresponding expansion shaft can then with further expansion machine be connected downstream components of the motor vehicle or in a request case operatively connected.

In this way it is possible to expand in the expander 16 more effective and at the same time regain expansion work. This is the relaxation nergie of the refrigerant converted into mechanical work and thus made available for other processes. For example, by coupling the drive shaft of the expansion machine 36 with the drive shaft of the compressor 12 , the work won by the expansion machine is used directly again in the refrigerant circuit. In special embodiments, for example, the expansion machine 36 and the compressor 12 be summarized in a structural unit.

It may also be advantageous, the expansion device 16 consisting at least of the variable expansion valve 26 and the downstream expansion machine 36 as a compact module in a structural unit.

The expansion device 16 Downstream is an evaporator 18 , which is operated as a heat exchanger to transfer the released cold to a carrier medium. This carrier medium may be, for example, air, which is a vehicle heating or cooling system (air conditioning), which in 2 is not shown, are supplied in a known manner.

The evaporator 18 downstream is in the embodiment of 2 a so-called collector 28 , which serves as a liquid separator or storage. Such a collector 28 is particularly necessary if the filling of the evaporator 18 can not be regulated. The collector 28 On the one hand, it separates the liquid components still present in the refrigerant after the evaporator and collects them, for example, in its lower region. The collector also has the task of storing refrigerants to compensate for small leaks in the system can. With the help of the collector also small unevenness of the mass flow of the refrigerant can be compensated. These occur, for example, at a speed increase of the compressor. This increases the mass flow of the refrigerant, without first the evaporator 18 can evaporate more refrigerant. The after the evaporator still liquid, ie not evaporated refrigerant is in the collector 28 deposited and stored. At a speed reduction of the compressor then the liquid refrigerant from the collector must be returned to the evaporator 28 to get promoted. This is done by sucking the liquid refrigerant from the collector by means of the compressor and into the refrigerant circuit 10 is transported.

3 shows an alternative embodiment of the expansion device according to the invention 16 a refrigerant circuit 10 , The expansion device 16 according to the embodiment of the 3 has at least one adjustable expansion valve 26 as well as an expansion machine 36 on. In the embodiment according to 3 are the expansion valve 26 and the expansion machine 36 parallel to each other in the refrigerant circuit 10 arranged. This arrangement can be advantageously by a compact module 30 realize. The parallel connection of the expansion machine 36 and the expansion valve 26 allows the sizing of the expansion machine 36 to simplify. This can then be designed in this case only for a common mass flow. However, if increased mass flows occur, they can be derived with the help of the expansion valve. In this way, a compact and simple expansion machine can be used.

The parallel circuit according to the embodiment in 3 also means a not inconsiderable advantage for the safety of the refrigeration system. In case of failure of the expansion machine 36 can the expansion valve 26 be controlled in an "emergency stop mode", which allows a safe shutdown of the refrigeration system.

In its other structure corresponds to the refrigeration cycle 10 according to embodiment of the 3 the refrigeration cycle described above 2 ,

The two presented refrigerant circuits and in particular the two expansion devices 16 This refrigeration cycles is meant that part of the regulatory tasks of the expansion device 16 from the expansion machine 36 on the expansion valve 26 is transmitted. The expansion machine 36 thus has only the task of providing the recoverable energy in the desired form. The regulation of the high pressure level in the refrigeration cycle 10 and thus the determination of the cooling capacity or the efficiency of the air conditioner is advantageously by the expansion valve 26 accepted.

4 shows a further embodiment of a refrigerant circuit 10 for an air conditioning system according to the invention. In its construction corresponds to the refrigeration cycle 10 according to the embodiment of the 4 the refrigeration cycle described above 3 , so at this point just to the appropriate description 3 is referenced. Unlike the in 3 illustrated embodiment has the expansion device 16 the refrigeration cycle in the embodiment according to 4 as an expansion valve, an overflow valve 27 which opens at a predeterminable mass flow of the refrigerant, or at a corresponding pressure of the refrigerant to a throttle body of the valve. The throttle body of the overflow valve 27 is characterized by the voltage applied to the inlet side of the valve pressure of the refrigerant against the force, such as a resilient Elementes asked. This allows easy adjustment of the pressure level on the high-pressure side of the refrigerant circuit. Elaborate and thus costly electronically controlled expansion organs can be avoided in this case.

In this case, the overflow valve 27 be designed for example as a sliding seat valve. By modifying the gap geometry of a conventional sliding seat valve, the tightness of such a valve can be significantly improved. In particular, by an extension of the valve piston, the gap geometry between the valve piston (slide element) and piston guide (seat of the slide) of the sliding seat valve can be optimized. Such a modification allows the use of the sliding seat valve as an expansion device in an air conditioning system, so that a good controllability is possible with a total of low-noise operation in all operating conditions. The overflow valve 27 However, it is not limited to the design of a sliding seat valve.

Of the Refrigerant circuit according to the invention a Air conditioning system or the expansion device according to the invention for a refrigerant are not on the embodiments shown in the drawing limited.

Especially is the air conditioner according to the invention not on the use of an internal heat exchanger in the refrigerant circuit limited.

Furthermore, the expansion device according to the invention and the corresponding air conditioning is not limited to the use of CO ₂ as a refrigerant.

Claims (15)

Expansion device ( 16 ) for a refrigerant, in particular an expansion device ( 16 ) for controlling the high pressure level of a refrigerant circuit ( 10 ) of an air conditioner, characterized in that the expansion device ( 16 ) at least one expansion valve ( 26 . 27 ) and an expansion machine ( 36 ). Expansion device ( 16 ) according to claim 1, characterized in that the expansion valve ( 26 ) and the expansion machine ( 36 ) in series with one another in the refrigerant circuit ( 10 ) operate. Expansion device ( 16 ) according to claim 1, characterized in that the expansion valve ( 26 . 27 ) and the expansion machine ( 36 ) parallel to one another in the refrigerant circuit ( 10 ) operate. Expansion device ( 16 ) according to claim 3, characterized in that the regulation of the expansion valve ( 26 . 27 ) has an emergency stop mode, which in case of failure of the expansion machine ( 36 ) a safe shutdown of the refrigerant circuit ( 10 ). Expansion device ( 16 ) according to one of the preceding claims, characterized in that the expansion valve ( 26 . 27 ) and the expansion machine ( 36 ) in a structural unit ( 30 ) are integrated. Expansion device ( 16 ) according to one of the preceding claims, characterized in that the expansion valve ( 26 ) is a regulated valve. Expansion device ( 16 ) according to one of the preceding claims 1 or 3, characterized in that the expansion valve ( 27 ) is an overflow valve. Expansion device ( 16 ) according to one of the preceding claims, characterized in that the expansion machine ( 36 ) has a shaft which is the output side coupled to a drive shaft of a compressor for a refrigerant. Expansion device ( 16 ) according to one of the preceding claims, characterized in that the expansion machine ( 36 ) drives a pre or densification device for a refrigerant. Expansion device ( 16 ) according to one of the preceding claims 1 to 5, characterized in that the expansion machine ( 36 ) is operatively connected to an electrical machine, in particular an electric generator. Air conditioning, in particular air conditioning for a motor vehicle, with at least one compressor ( 12 ), a condenser or gas cooler ( 14 ) an expansion device ( 16 ) and an evaporator ( 18 ) suitably connected by connecting means ( 20 ) are interconnected to a refrigerant circuit ( 10 ) of the air conditioning system, characterized in that the expansion device ( 16 ) of the refrigerant circuit ( 10 ) at least one expansion valve ( 26 . 27 ) and an expansion machine ( 36 ). Air conditioning system according to claim 11, characterized in that the valve ( 26 . 27 ) of the expansion unit ( 16 ) is a controllable valve. Air conditioning system according to claim 11 or 12, since characterized in that the valve ( 26 . 27 ) of the expansion unit ( 16 ) an overflow valve ( 27 ). Air conditioner according to one of claims 11 to 13, with a refrigerant for the refrigerant circuit ( 10 ) which releases the heat in the supercritical region. Air conditioning system according to one of claims 11 to 14, characterized in that the refrigerant is CO ₂ use.