EP1596140A2 - Expansion apparatus for refrigerant - Google Patents

Abstract

The expansion device (16) regulates the high-pressure level of a refrigerant circuit (10) in an air conditioner. The expansion device includes at least one expansion valve (26) and one expansion engine (36), which may be operated in series or parallel in the refrigerant cycle.

Description

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

State of the art

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 possibility for improvement of the outlined standard version of a refrigeration system For example, it is the expansion valve through a work-performing Expansion device to replace a so-called expansion machine. To this Way, the expansion process of the refrigeration cycle is designed to be more effective and to be recovered at the same time expansion work. The relaxation energy of the Refrigerant is thus converted into mechanical work and for others, downstream processes made usable.

From the prior art, various technical solutions are known to a To realize expansion machine practically.

DE 198 41 686 A1 discloses a compressor chiller in which a refrigerant is compressed to supercritical pressure in a compressor, then through Heat exchange with the air cooled by a gas cooler and then one Expander is supplied. As an expansion or relaxation machine for The cooled refrigerant, which is at critical pressure level, is in the Device of DE 198 41 686 A1 uses a gear motor having a housing with Has at least two mutually rotatable gears.

From DE 100 13 191 C1 an air conditioner, in particular an air conditioner for motor vehicles is known, whose refrigerant circuit has 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 system of DE 100 13 191 C1 is configured in such a way that the refrigerant carbon dioxide (CO ₂ ) in the refrigerant circuit is brought from a supercritical state into a wet steam state.

Regardless of the selected technology, the Regulatory requirements of the expansion machine is a particular challenge dar.

Another problem is that an expansion machine a Safety function has to fulfill. The expansion machine is supposed to be too extreme Loads of the system, allow the system to return to a stable state or, if necessary, shut down the system safely. These extremes Conditions that are far removed from the normal operating conditions must therefore be considered in the design of the expansion machine, which is an optimal Design of the expansion machine, especially in normal operation makes heavy.

Advantages of the invention

The expansion device according to the invention for a refrigerant, in particular a Such expansion device for controlling the high pressure level of Refrigerant circuit of an air conditioner, has at least one expansion valve and a Expansion machine on. By this combined structure of the expansion device becomes part of the heavy control tasks of the expansion process, or the Safety tasks of the expansion machine from the machine to the expansion valve transfer. The expansion machine thus has only the task of Energy recovery, and the recovered energy in the appropriate form to to provide further use. The setting of the high pressure and the Safety function is provided by the expansion valve expansion valve accepted.

In this way, it is possible to an expansion device for a refrigerant such operate both the setting of the high pressure level and the provision the energy recovered in each other from almost independent and thus optimal Way is feasible. For example, the speed of the expansion machine on the energy use and conversion are optimized without the need to be adjusted High pressure level is to be observed here.

The features listed in the dependent claims are advantageous Further developments of the expansion device according to the invention possible.

In an advantageous embodiment of the expansion device according to the invention Both the expansion machine and the variable expansion valve are in series with each other Refrigerant circuit of the air conditioning arranged.

In an alternative, advantageous embodiment of the invention Expansion means are the variable expansion valve and the expansion machine arranged parallel to each other in the refrigerant circuit of the air conditioner. The Parallel connection of expansion valve and expansion machine also makes it possible to simplify the dimensioning of the expansion machine. This can be done in the case of Parallel connection designed only for the usual or optimal mass flow with the expansion valve being used, if increased Mass flows would occur.

Such a parallel connection of the essential components of the expansion device also means one with regard to the safety of the refrigeration system negligible benefit. So can the failure of the expansion machine the Expansion valve in an "emergency stop mode" occur and despite inoperative Expansion machine ensure a safe shutdown of the plant.

In advantageous embodiments, the expansion valve is a controllable valve, with which can regulate the high pressure level of the refrigerant circuit. It can be both externally and internally controlled. The Expansion valve can be an electrically operated valve or even a mechanical or thermally controlled valve. A possible embodiment of the expansion valve which can be used, consists in an overflow valve, which at a predetermined mass flow of the coolant opens.

In a particularly advantageous embodiment of the invention Expansion device, are their controllable expansion valve and the Expansion machine in a structural unit to a compact module summarized. Such a module can be easily in corresponding Integrate refrigeration circuits.

Since the control of the high pressure level of the refrigerant circuit substantially by the expansion valve is made, the expansion machine has only the Task to provide the recovered energy in an appropriate form. So can the Drive shaft of the expansion machine, for example, directly to the drive shaft of the Refrigerant compressor be coupled or coupled. This is especially one advantageous development of the claimed expansion device, since the Speed of the expander expansion machine independent of the Control of the high pressure can be selected. 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 forward or Compressor for the refrigerant drives, the generated Volume flow can be set arbitrarily, since it is no longer dependent on the regulation of High pressure levels of the refrigerant is affected. The task of a regulation of Expansion machine for adjusting the high pressure level in the refrigerant circuit and the provision of the recoverable mechanical energy in an appropriate form advantageously no longer linked together. Because these two tasks are included Expansion machines of the prior art have different requirements for the Speed of the expansion machine 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 expander of the expander with a electrical machine, in particular with an electric generator operatively connected or is operatively connected. When the recovered energy by means of a generator in electrical energy is to be converted, so is the claimed Expansion device of great benefit. The expansion valve of the Expansion device can set the optimum high pressure while the characteristic the expansion machine, for example, the characteristic of a conventional motor vehicle generator equivalent. The regulation of the output voltage of the generator is by such Arrangement greatly simplified. 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 functions are optimized.

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

With the claimed, inventive expansion device can be in Advantageously, an air conditioner, in particular a dynamically operated Further develop air conditioning for a motor vehicle. By the division of tasks of the Components of the expansion device of the refrigeration cycle of the air conditioning can be both the regulation of the high pressure level of the refrigerant and thus the Optimize efficiency and the cooling capacity of the refrigeration cycle as well as in addition Gain energy through the expansion process by means of an expansion machine. The thus obtained additional energy can be advantageously for operation use other components of the air conditioning or refrigeration circuit.

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 thus makes it possible to control a To simplify the expansion machine or to make such a regulation possible.

Further advantages and features of the expansion device according to the invention or an air conditioning system according to the invention with such an expansion device in Refrigerant circuit will become apparent from the following description of some Embodiments.

drawings

In the drawing, three embodiments of the invention Expander or examples of three refrigerant circuits using Expansion devices according to the invention shown in the following Description will be explained in more detail. The figures of the drawings, whose Description and claims contain numerous features in combination. One A person skilled in the art will also consider these features individually and make further, meaningful ones Combine combinations, which are thus to be regarded as also disclosed.

It shows

Fig. 1

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

Fig. 2

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

Fig. 3

a second embodiment of an inventive Expansion device and the associated refrigerant circuit a Air conditioning,

Fig. 4.

a further embodiment of an inventive Expansion device and the associated refrigerant circuit a Air conditioning.

Description of the embodiments

The illustrated in Fig. 1 in principle refrigerant circuit 10 of an air conditioner has a compressor 12, a condenser or gas cooler 14, an expansion device 16 and an evaporator 18, which via corresponding connecting means 20th 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 cooled as gas in the supercritical state. For this reason, this heat exchanger 14 is referred to as gas cooler when using the supercritical operation of the refrigerant. Subsequently, the thus cooled refrigerant is expanded by means of an expansion device 16 to a lower pressure and further cooled. The expansion device 16 is usually followed by an evaporator 18, 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 controlling the throttling at the expansion device of Refrigerant circulation can be the pressure on the high pressure side of the thermodynamic Circular process can be controlled or regulated, so that the specific cooling capacity of the Air conditioning can be varied in the desired manner. So it is possible one to obtain maximum effective coefficient of performance by the pressure of the high pressure side of the Thermodynamic cycle (high pressure level) depending on the Temperature at the gas cooler outlet or the ambient temperature in an adapted manner is set.

Especially in refrigeration systems with refrigerants, due to their thermodynamic Properties that release heat in the supercritical range can be the high pressure level be set at the heat emission regardless of the temperature. To this, compared to refrigerants with heat emission in the wet steam area additional To use degree of freedom in an advantageous manner, can be controlled and / or regulated Expansion facilities are used.

Fig. 2 shows a first embodiment of a special refrigerant circuit for a Air conditioning system using an expansion device 16 according to the invention.

The refrigerant circuit 10 of a CO ₂ air conditioning system according to Figure 2 has a compressor 12, which may be electrically operated, for example, or else driven by corresponding coupling elements of the internal combustion engine of a motor vehicle. In the compressor 12, first of all, compression of the refrigerant, in the case described CO ₂ , is carried out in order to increase the internal energy of the refrigerant. In the flow direction downstream of the compressor 12, a separator, in particular an oil separator 20 is provided, which serves to deposit the oil residues contained in the gaseous refrigerant and provide these via appropriate connecting means 22, for example, in turn, the compressor 12 for lubrication.

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

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

The compressed refrigerant is now supplied to an expansion device 16 and in this expanded to a lower pressure level. The inventive Expansion device 16 consists at least of a regulated expansion valve 26 and an expansion machine 36. In the embodiment of FIG. 2 are the Expansion valve 26 and the expansion machine 36 in series with each other in Cooling circuit 10 of the refrigerant connected. The expansion valve 26 is a adjustable valve, which by a corresponding position of the throttle body of the Valve can release a desired opening area and thus the Pressure level on the high pressure side of the refrigerant circuit 10 determined. The Expansion valve 26 may, for example, an electromagnetically actuated valve or but also be a purely mechanically controlled, or a thermally controlled valve. This can be both an external, as well as an internally controlled valve act. be. The controllable expansion valve 26 is followed by a Expansion machine 36, which in principle by every work Expansion device may be formed.

As expansion machines are particularly conceivable and advantageous, so-called Gear machines, which effectively convert the expansion energy into mechanical Enable work. About a corresponding wave, the expansion machine can then be operatively connected to other downstream components of the motor vehicle or in a request case operatively connected.

In this way it is possible, the expansion process in the expansion device 16 more effective and at the same time regain expansion work. in this connection the relaxation energy of the refrigerant is converted into mechanical work and thus made available for other processes. For example, by a Coupling of the drive shaft of the expansion machine 36 with the drive shaft of the Compressor 12, the work won with the expander directly back in Refrigerant circuit can be used. In specific embodiments, this can be done For example, the expansion machine 36 and the compressor 12 in a structural Unit be summarized.

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

Downstream of the expansion device 16 is an evaporator 18, which as Heat exchanger is operated to release the released cold on a support medium transfer. This carrier medium may be, for example, air, which is a vehicle Heating or cooling system (air conditioning), which is not shown in Fig. 2, in be supplied in a known manner.

Downstream of the evaporator 18 is in the embodiment of Figure 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 18th can not be regulated. The collector 28 separates on the one hand after the Evaporator still in the refrigerant existing liquid components and collects this example, in its lower part. The collector also has the task of Store refrigerant in order to compensate for small leaks in the system can. With the help of the collector can also small unevenness of the mass flow of the refrigerant can be compensated. These occur, for example, in a Speed increase of the compressor. This increases the mass flow of Refrigerant, without first the evaporator 18 can evaporate more refrigerant. The after the evaporator still liquid, d. H. non-evaporated refrigerant is in the Collector 28 deposited and stored. At a speed reduction of Compressor must then return the liquid refrigerant from the collector to the Evaporator 28 are transported. This is done by mixing the liquid refrigerant sucked by the compressor from the collector and into the refrigerant circuit 10th is transported.

Fig. 3 shows an alternative embodiment of the expansion device according to the invention 16 of a refrigerant circuit 10. The expansion device 16 according to the Embodiment of Fig. 3 has at least one controllable expansion valve 26 as well an expansion machine 36. In the embodiment of FIG. 3 are the Expansion valve 26 and the expansion machine 36 parallel to each other in Refrigerant circuit 10 is arranged. This arrangement can be in an advantageous manner Way through a compact module 30 realize. The parallel connection of Expansion machine 36 and the expansion valve 26 allows the Dimensioning of the expansion machine 36 simplify. This can be in this case then be designed only for a common mass flow. Should, however, increased Mass flows occur, so they can be derived with the help of the expansion valve become. In this way is a compact and simple expansion machine usable.

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

In its other construction corresponds to the refrigeration cycle 10 according to the embodiment FIG. 3 shows the previously described refrigeration cycle according to FIG. 2.

The two presented refrigeration cycles and especially the two Expander 16 of these refrigeration circuits is meant that part of the Control tasks of the expansion device 16 of the expansion machine 36 the expansion valve 26 is transmitted. The expansion machine 36 thus only has 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 Cooling capacity or the efficiency of the air conditioner is in an advantageous manner taken over the expansion valve 26.

Figure 4 shows another embodiment of a refrigerant circuit 10 for a inventive air conditioning. In its construction, the refrigeration cycle 10 corresponds according to the embodiment of Fig. 4 the previously described refrigeration cycle after 3, so that at this point only to the corresponding description of Figure 3 is referenced. In contrast to the embodiment shown in Figure 3 has the expansion device 16 of the refrigeration cycle in the embodiment according to Figure 4 as an expansion valve overflow valve 27, which at a predetermined Mass flow of the refrigerant, or at a corresponding pressure of the refrigerant opens to a throttle body of the valve. The throttle body of the overflow valve 27th This is due to the pressure of the refrigerant applied to the inlet side of the valve placed against the force, for example a spring-elastic element. this makes possible the adjustment of the pressure level on the high pressure side of the refrigerant circuit easy way. Elaborate and therefore cost-intensive electronically controlled Expansion organs can be avoided in this case.

In this case, the overflow valve 27 may be formed, for example, as a sliding seat valve. By modifying the gap geometry of a conventional sliding seat valve leaves the tightness of such a valve significantly improve. 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 be optimized. Such a modification allows the use of the Sliding seat valve as an expansion element in an air conditioning system, allowing a good Controllability with a total of low-noise operation in all operating conditions allows becomes. However, the overflow valve 27 is not on the design of a sliding seat valve limited.

The inventive refrigerant circuit of an air conditioner or the Expansion device for a refrigerant according to the invention are not on the in the Drawing illustrated embodiments limited.

In particular, the air conditioning system according to the invention is not based on the use of a limited internal heat exchanger in the refrigerant circuit.

Furthermore, the erfmdungsgemäße expansion device 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) comprises 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 each other in the refrigerant circuit (10) are operated. Expansion device (16) according to claim 1, characterized in that the expansion valve (26,27) and the expansion machine (36) parallel to each other in the refrigerant circuit (10) are operated. Expansion device (16) according to claim 3, characterized in that the control of the expansion valve (26,27) has an emergency stop mode, which enables a safe shutdown of the refrigerant circuit (10) in case of failure of the expansion machine (36). Expansion device (16) according to one of the preceding claims, characterized in that the expansion valve (26, 27) and the expansion machine (36) are integrated in a structural unit (30). 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 can be coupled on the output side with a drive shaft of a compressor for a refrigerant. Expansion device (16) according to any 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. An air conditioning system, in particular an air conditioning system for a motor vehicle, comprising at least one compressor (12), a condenser or gas cooler (14) of an expansion device (16) and an evaporator (18) suitably interconnected by connecting means (20) Refrigerant circuit (10) of the air conditioning system, characterized in that the expansion device (16) of the refrigerant circuit (10) comprises 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, characterized in that the valve (26, 27) of the expansion unit (16) is an overflow valve (27). Air conditioning system according to one of claims 11 to 13, with a refrigerant for the Refrigerant circuit (10), which releases the heat in the supercritical area. Air conditioning system according to one of claims 11 to 14, characterized in that the refrigerant is CO ₂ use.

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