WO2008064816A1

WO2008064816A1 - Thermostatic expansion valve for refrigeration cycles or heat pump cycles, featuring a mechanically controlled safety function

Info

Publication number: WO2008064816A1
Application number: PCT/EP2007/010117
Authority: WO
Inventors: Juan Aguilar; Rainer Maurer; Jean-Jacques Robin
Original assignee: Otto Egelhof Gmbh & Co. Kg
Priority date: 2006-12-01
Filing date: 2007-11-22
Publication date: 2008-06-05
Also published as: DE102006057132A1; DE102006057132B4

Abstract

The invention relates to a thermostatic expansion valve for regulating a high pressure in a refrigeration cycle or heat pump cycle (11) that can be operated both transcritically and subcritically. A first actuator (36) of said thermostatic expansion valve comprises a chamber (38) that is delimited by a first effective surface (37) that contains a control filling (41). The first actuator (36) can be triggered according to the high pressure and the temperature and is movably coupled to a second actuator (46). The second actuator (46) can be triggered regardless of the temperature and in accordance with the high pressure and can be adjusted to a maximum operating pressure for opening the through-hole (29).

Description

Thermostatic expansion valve for refrigeration or heat pump circuits with mechanically controlled safety function

The invention relates to a thermostatic expansion valve for a refrigeration and / or heat pump cycle according to the preamble of claim 1.

In transcritical refrigeration or heat pump cycles, the high-pressure side heat release is usually above the critical pressure of the applied refrigerant. Due to the resulting sliding temperature gradient in the gas cooler, the pressure at the gas cooler outlet is a degree of freedom in the circulation process. Especially in cycles that use CO ₂ as a refrigerant, it is very important to adjust the high pressure as a function of the ambient conditions. to regulate the gas cooler outlet temperature in an optimum efficiency range. For CO ₂ air conditioning systems, only fixed throttles or externally controlled expansion elements are usually used in the regulation of the refrigeration cycle. The former do not allow adaptation of the high pressure to the process boundary conditions during operation. For this purpose, externally controlled expansion devices have to be controlled by electronic control elements, whose reactivity is inadequate, especially for automotive applications. Accordingly, they can not provide sufficient reliability. Other disadvantages include high susceptibility to failure, high development and acquisition costs.

DE 102 49 950 B4 discloses an expansion valve for high-pressure refrigeration systems with a valve seat, a valve element which cooperates with the valve seat, a spring arrangement acting on the valve element, and an adjusting device for the spring arrangement, wherein the spring arrangement at least a first spring and a second Spring, which act on the valve element has, the first spring defines a working area and the second spring has a variable by the adjusting spring force.

From US 6,012,300 an expansion valve has become known, which has a chamber in which the refrigerant is enclosed. The chamber is bounded by a membrane which acts indirectly on a valve element. However, the membrane is also exposed to the high-pressure side refrigerant. In particular, the active surfaces to which the refrigerant trapped in the chamber acts and those to which the high-pressure side refrigerant coming from the gas cooler acts are identical. With the described expansion valve, no protection against high pressures above a maximum permissible value (for example 120 bar) is possible. In addition, a safe starting behavior at inlet temperatures at the expansion valve above the critical temperature of the refrigerant is not possible. A reliable application can therefore not be realized with the expansion valve of the prior art. From DE 10 2005 034 709.6 a thermal expansion valve is known, which has a first and second active surface, which are coupled in movement with a valve element. The first active area is part of a stretchable separating device, which comprises a chamber with a control filling in the thermal head. Thereby, the temperature of the high-pressure side refrigerant can be detected. About this stretchable separating device of the thermal head of the temperature-dependent pressure of the control filling in the chamber is transferred to a temperature-independent spring element, which is in communication with the second effective surface, which also bears the high pressure. This refinement is intended to achieve a high-pressure-limiting function in the supercritical control range.

Object of the present invention is therefore to provide an expansion valve that adjust the high pressure of a transcritical refrigeration or heat pump cycle within an optimal range and can prevent exceeding a maximum allowable value independently.

This object is achieved by an expansion valve according to the features of claim 1. Through the use of a first actuator, which is controlled by the high pressure and the temperature of the refrigerant dependent, wherein the control filling of the first actuator has a filling density which is immediately below the critical density of the control filling and a second actuator which thermally independent and high pressure can be driven dependent is created by the movement coupling an expansion valve, which on the one hand controls a refrigerant circuit with optimum high pressure and on the other hand comprises a mechanically controllable security element. When a maximum set opening pressure or operating pressure is exceeded, the passage opening is released, so that an excess pressure in the refrigerant circuit prevents and thus a safety function against excessive operating pressures is given. Such an expansion valve allows in a refrigeration or heat pump cycle, in particular with an internal heat exchanger, an optimal high pressure as a function of an outlet temperature. temperature of the refrigerant leaving the inner heat exchanger of the refrigeration pump and / or heat cycle. In addition, in any operating position exceeding a predefined maximum high pressure can be prevented automatically and without external control.

According to an advantageous embodiment of the invention, it is provided that the first actuator has a chamber whose inner volume is temperature-dependent variable. As a result, the temperature of the high-pressure-side refrigerant, which flows into the expansion valve, for example, from the inner heat exchanger, can be absorbed. Thus, an operation-adapted control of the circuit via a first active surface can take place, which is formed on the chamber and preferably receives the valve element. Preferably, the first active surface of the first actuator is a part of the bellows actuator. As a result, a component-reduced arrangement and an immediate force effect can be achieved.

According to a preferred embodiment of the invention, it is provided that the chamber is designed bellows-like or membrane-like and is made of a thermally conductive material. As a result, the temperature of the high-pressure side refrigerant, which rests against the active surfaces of the chamber in the high-pressure chamber, can be exactly sensed. This results in a fast control of the first actuator or the flow cross-section determining valve element.

The control filling provided in the chamber of the first actuator is preferably designed such that the valve element allows an opening and closing movement for controlling a COP-optimized high-pressure region. As a result, the first actuator can be actuated under normal operating conditions.

Furthermore, it is preferably provided that the chamber, in particular the inner contour of the chamber, by a sleeve. or webs is guided. This allows deformations due to the effect of Control filling and the high-pressure side refrigerant can be prevented.

In addition, it is preferably provided that, in addition, a mixture of substances for the control filling is selected, which has a critical temperature which is below the critical temperature of the refrigerant to be controlled. Thus, it is achieved that the isochore, temperature-dependent pressure change of the control charge continues approximately at the same slope as in the two-phase state after it has left the vapor pressure range.

Furthermore, it is preferably provided that the second actuator is adjustable to a maximum opening pressure for opening the passage opening. This makes it possible that a voltage applied to the active surface of the second actuator high pressure independent of temperature then causes an actuating movement of the coupled first actuator or its valve element as soon as a maximum operating pressure is exceeded.

According to a further advantageous embodiment of the invention, it is provided that the second actuator has a membrane or plate spring-shaped element with a second active surface and the first actuator is provided for movement coupled thereto. This membrane or dish spring-shaped element allows an arrangement in a high-pressure chamber, in which the high-pressure chamber is made possible with respect to a space separated by the membrane or plate spring-shaped element with atmospheric pressure. Preferably, the second actuator is constructed with a discontinuous path-force characteristic, so that the element endeavors to switch from a predefined initial rest position into a second component-specific end position with sufficient force surplus of a force formed by the applied high pressure. In this second component-specific end position, an enlargement of the opening cross-section of the passage opening of the expansion valve takes place. Furthermore, it is preferably provided that the membrane or plate spring-shaped element has its own biasing force, which is at least partially or completely adjustable to the maximum opening pressure. As a result, a small number of components and a simple structure can be made possible.

It is preferably provided that the membrane- or dish-spring-shaped element separates the valve housing into a high-pressure chamber and a room with atmospheric pressure. This allows the high pressure to operate against the atmospheric pressure, so that in different applications the same conditions of use are given. In addition, this embodiment has the advantage that when using a power storage element, which counteracts a lifting movement of the membrane or plate spring-shaped element is adjustable from the outside.

The second actuator is alternatively subjected to a mechanical biasing force, in particular by a spring element, which is preferably set such that when the predefined maximum high pressure of the refrigerant circuit is exceeded, the valve element of the first actuator with a valve lift is controlled. This makes it possible for a passage opening to be opened as a function of the applied pressure and thus a sufficient flow cross-section to be released in order to avoid a further increase in the maximum permissible high pressure.

According to a further preferred embodiment of the invention, it is provided that the second actuator comprises a clamping device. This makes it possible that different opening pressures are application-specific adjustable.

A maximum stroke movement of the first actuating element is preferably limited by a mechanical stop or a travel limiting element. This makes it possible that a temperature-dependent lifting movement of the first actuator a lifting movement of the second actuator would not override and thus the safety function would be given.

Furthermore, the passage opening is advantageously provided in a second valve element, which in turn is arranged in a passage opening between the high-pressure and low-pressure side and the bias acting on the second actuator is set such that when the predefined opening pressure is exceeded, a valve lift of the second valve element is controllable. It is thereby achieved that regardless of the temperature of the refrigerant, the first actuator is disabled, so that the safety function is accepted.

According to a further embodiment of the invention, it is provided that in a rest position of the valve element between the valve element and the valve seat, a predetermined passage opening is released. This means that if the temperature and pressure dependent excess force on the underside of the prestressed spring element is insufficient to overcome its bias, only a suitably predefined throttle cross-section is released and the thermostatic expansion valve acts as a fixed throttle, causing the high pressure in the circuit by itself established.

The invention and further advantageous embodiments and developments thereof are described in more detail below with reference to the examples shown in the drawings and explained. The features to be taken from the description and the drawings can be applied individually according to the invention individually or in combination in any combination. Show it:

1 shows a schematic representation of a refrigerant circuit,

2a shows a state diagram for illustrating the function of a refrigerant circuit with an expansion valve according to the invention, FIG. 2b shows a diagram for illustrating a valve opening cross section as a function of a stroke movement of a valve element,

Figure 3 is a schematic sectional view of a first

Embodiment of a thermostatic expansion valve

Figure 4 is a schematic sectional view of a second

Embodiment of a thermostatic expansion valve and

Figure 5 is a schematic sectional view of a third

Embodiment of a thermostatic expansion valve.

FIG. 1 shows a refrigeration and / or heat pump cycle 11 of an air conditioning system. In a refrigerant compressor 12, a gaseous refrigerant, in particular CO ₂ , is compressed. The compressed refrigerant is supplied to a gas cooler 13 where heat exchange takes place between the compressed refrigerant and the ambient to cool the refrigerant. The refrigerant leaving the gas cooler 13 reaches an internal heat exchanger 14, which communicates with an expansion valve 15. The expansion valve 15 acts on the one hand to limit the pressure of the refrigerant and on the other hand to regulate the pressure of the refrigerant at the outlet of the inner heat exchanger 14. From the expansion valve 15, the refrigerant passes to an evaporator 16. In the evaporator 16, the refrigerant absorbs heat from the environment. Downstream of the evaporator 16 is an accumulator 17 to separate refrigerant of the gas phase and the liquid phase and to collect liquid CO ₂ at the same time. The accumulator 17 is in turn connected to the inner heat exchanger 14 in connection.

Based on the state diagram of Figure 2, in which the pressure p is plotted against the specific enthalpy H, the operation of the air conditioner will now be explained. A refrigerant, for example CO ₂ , in the gas phase is compressed in the refrigerant compressor 12 (AB). Then, the hot, under high pressure, transcritical refrigerant in the gas cooler 13 and in the inner heat exchanger is cooled (B- C or CD). The pressure is reduced in the expansion valve (DE) in order to evaporate the now two-phase (gas and liquid phase) refrigerant in the evaporator 16 (EF) and thereby deprive the environment of heat. The COP is determined by the ratio of the enthalpy change Δi in step EF and the enthalpy change ΔL in step AB, ie COP = Δi / ΔL.

The critical temperature of CO ₂ is about 31 ⁰ C, which is lower than the critical temperature (often> 100 ⁰ C) of fluorocarbons, which are currently used in air conditioning systems. As a result, the temperature of CO ₂ at the exit of the internal heat exchanger 14 may become higher than the critical temperature of CO ₂ . In this state, the CO ₂ does not condense even at the outlet of the inner heat exchanger 14. Therefore, the pressure at the exit of the internal heat exchanger 14 must be regulated. Thus, when the external temperature is high, for example in the summer, it is necessary to set a high pressure at the exit of the internal heat exchanger in order to obtain a sufficient cooling capacity. The starting temperature at the inner heat exchanger 14 depends inter alia on the refrigerant side temperature at the gas cooler outlet, which in turn depends on the ambient temperature. This means that the temperature of the CO ₂ at the outlet of the internal heat exchanger 14 can also be used for the regulation of the COP-optimized high-pressure, which is otherwise dependent on the refrigerant-side gas cooler outlet temperature.

2a, the COP-optimized control range is represented by the characteristic curves 21 'and 21 "The intermediate double arrow 22 designates a valve stroke range from 0 to approximately 75% of the valve stroke .between the characteristic curve 21" and the characteristic curve 21'" As a result of a further stroke movement of the valve element over approximately 75% of the valve lifting range, an increase in pressure can be reduced thanks to the steeper double-cross-section characteristic of the valve element (FIG Characteristic curve 21 "" represents an adjustable high pressure limit for the refrigerant circuit 11 to be controlled. This can be made variable.

FIG. 3 shows a first embodiment of a thermostatic expansion valve according to the invention, by means of which a control according to the characteristic curves 21 'to 21 "" is made possible.

The thermostatic expansion valve 15 comprises a valve housing 26, which has a high-pressure side feed opening 27, which leads into a high-pressure chamber 28. The high-pressure chamber 28 is connected via a passage opening 29 to a low-pressure-side discharge opening 31. The passage opening 29 has a valve seat 32, in which a valve element 33 is provided in a closed position and the feed opening 27 to the discharge opening 31 separates.

In the high-pressure chamber 28, a first actuator 36 is provided, which comprises a first active surface 37, on which the valve element 33 is provided. At this first active surface 37, a chamber 38 engages or is formed as part of the chamber 38. The chamber 38 is designed like a membrane or bellows. This chamber 38 is provided with a control filling 41, the pressure in the chamber 38 is temperature-dependent. As soon as a high pressure is applied to the high-pressure side, it acts against the first active surface 37 and opens the passage opening 29, provided that the high pressure applied to the first effective surface 37 has a surplus of force relative to the pressure of the control filling 41 in the chamber 38. The opening or closing movement of the valve element 33 in the COP-optimized control range between the characteristic curves 21 'and 21 "according to Figure 2a is independent of a further second actuator 46 which can be controlled in a high pressure-dependent and thermally independent manner In the opening direction, the valve element 33 likewise experiences a stroke limitation by means of a stop 60. The first actuator 36 can additionally engage inside or outside the chamber 38 not shown in detail spring element for adaptation of the opening and closing movement include.

The second actuator 46, which can be actuated as a function of pressure, comprises a second active surface 48, which receives the first actuator 36, so that the first and second actuators 36, 46 are coupled for movement. The second actuator 46 includes, for example, a bellows 49 or a membrane, thereby providing a separation between the high pressure in the high pressure space 28 and an atmospheric pressure, which rests within the bellows 49 due to an opening to the environment in the valve housing 26. Within the bellows 49, a temperature-independent spring element 51 is preferably provided. This spring element 51 operates against the pressure prevailing in the high pressure chamber 28 high pressure and is set to a predetermined, to be controlled high pressure. The lifting movement of the second actuator 46 is limited in the opening direction by a stop 61 and closing movement by a stop 62.

This expansion valve allows a stroke movement of the second actuator 46 to be controlled and the prestress of the prestressed spring element 51 to be overcome by a force excess generated in the refrigerant circuit via the second active surface 48. As a result, a flow cross-section of the passage opening 29 is released or increased as a function of the pressure and independently of the temperature.

With sufficient excess force is thus released via a predefined stroke characteristic of the optimal opening cross-section and thus set the optimum high pressure as a function of the high-pressure side outlet temperature of the refrigerant preferably at the inner heat exchanger. The refrigerant side gas cooler exit temperature is the preferable control temperature in the cycle in view of COP optimization, and the high pressure side exit temperature at the inner heat exchanger can also be applied for the purpose of regulating the high pressure in a COP optimum range. For this purpose, either simulation or trial for the circulation, in the the expansion valve is used, which determines for each COP optimal gas cooler outlet state corresponding exit states on the inner heat exchanger. The high-pressure-side outlet temperature at the inner heat exchanger thus results in a COP-optimized pressure profile, to which the optimum valve stroke characteristic curve is aligned (FIG. 2a). However, this COP-optimal valve lift characteristic is limited to a portion of the total valve lift range to be determined in the application, for example, between 0 and 75% in the case where a thermostatic expansion valve has a single throttle body, as compared to the expansion valve 15. Beyond this approximately 75% range, the overpressure function starts, which is controlled by the second actuator 48. That is, the switching characteristic and the bias applied to the second actuator 48 are selected such that the second actuator 48 of the expansion valve 15 is capable, under all circumstances, of exceeding the predefined opening pressure, the valve element 33 beyond the above limit of the valve lift range to move. If the mass flow characteristic of the passage opening 29 above the above limit, ie the 75% range, is sufficiently steep enough to reach 100% of the total valve lift, so much mass flow from the high to the low pressure side degraded and thus a further rise of the High pressure of the refrigerant circuit can be avoided. Consequently, the safety function is achieved against excessive system pressures.

The advantageous arrangement of the thermostatic expansion valve at the evaporator inlet also avoids complex Leitungssatzverlegung, as required for example in the application of a thermostatic expansion valve according to US Pat. No. 6,012,300, since the valve described therein must absorb the refrigerant side outlet temperature at the gas cooler - either by a local arrangement at the gas cooler passage or by the laying of a capillary line between valve and gas cooler outlet.

The scope of the present invention thus includes a transcritical or subcritical refrigeration or heat pump cycle with an internal ren heat exchanger, which has a prescribed thermostatic expansion valve and the further advantage that the expansion valve allows an independent adjustable overpressure or safety function and can be placed without additional wiring at the evaporator inlet - as in today's systems common, without affecting the thermostatic control option of the COP having to do without optimal high pressure.

By means of this embodiment according to the invention an independently adjustable overpressure and safety function is thus made possible so that the refrigerant circuit can operate in COP-optimal high pressure. This is done by a two-stage control. The first actuator 36 operates in the COP-optimal high-pressure region. The high-pressure acts against the first active surface 37 and the control filling 41, which builds up a temperature-dependent internal pressure. The opening pressure can preferably be adjustable by a biasing device, which engages, for example, on the spring element 51 or another force element that builds up a prestressing force, starting from a preset high pressure.

FIG. 4 shows an alternative embodiment to FIG. Instead of a bellows 49, the second actuator 46 has a dish-shaped element 52, which comprises the analogous function to the bellows 49. This plate spring-shaped element 52 may have its own biasing force, so that a coordination of the compressive forces by the atmospheric pressure, at least one acting on the dish-shaped element 52 spring element 51 and the plate spring-shaped element 52 against the maximum high pressure of the refrigerant circuit can take place. If the pretensioning force of the dish-shaped element 52 is large enough, it is possible to dispense with a spring element 51 which is arranged in the atmospheric pressure space.

Alternatively, it can be provided that an additional spring element in the form of a spiral spring is located in the high-pressure chamber 28 and between the plate-spring-shaped element 52 on the one hand and one Passage opening 29 surrounding bearing surface 53 on the other hand rests. As a result, the opening movement of the plate-spring-shaped element 52 can be supported. In analogy to FIG. 3, the stops 59 to 62 are provided.

FIG. 5 shows a further alternative embodiment of the expansion valve 15. In addition to FIG. 4, this expansion valve 15 has a travel transfer element 54 which is fastened to the active surface 48 of the second actuator 46 and acts on a further valve element 56, which comprises the passage opening 29 and the valve seat 32 and is itself provided in a valve seat 58 , This path transmission element 54 enables the safety function to be ensured independently of the temperature of the mass flow. With an increase in temperature of the mass flow, an adjusting movement of the first actuator 36 and thus of the valve element 33 would take place in the valve seat 32, so that a stroke of the second actuator 46 would not lead to opening of the passage opening 29, but the flow cross-section would be reduced or even closed. The second actuator 46 is connected via the path transmission element 54 with the additional valve member 56 zugbeansprucht connected, so that at an adjustable maximum pressure, the valve element 56 raised from the valve seat 58 and the flow cross-section is increased.

Instead of the plate-spring-shaped element 51 may also be provided as a separation surface a membrane. In a preferred embodiment, such a membrane comprises an annular cross-section, which is clamped with an outer circumference on the outer wall of the high-pressure chamber 28 and receives the first actuator 36 by an analogous clamping. The membrane may be partially formed as a rubbery member or may have a rubbery, refrigerant-leakage-sealing coating to define the high-pressure space 28 in the valve body against atmospheric pressure. The setting of the opening force as a safety function is carried out in such a case only by additional spring elements in the high-pressure chamber or are provided at the opposite room with atmospheric pressure.

The stop 59 may be designed to set a throttle cross-section. In analogy to the previous embodiments, the stops 60 to 62 may be provided.

All of the aforementioned features are essential to the invention and can be combined with one another as desired.

Claims

claims

1. Thermostatic expansion valve for controlling a high pressure of a transcritical as well as subcritically operable Kältebeziehungsweise heat pump cycle (11) with a valve housing (26) in which the input side, a high pressure in a feed port (27) and the output side, a low pressure at a discharge opening (31) is present with a valve element (33) which closes a valve seat (32) of a passage opening (29), which is arranged between the supply opening and the discharge opening (31), for flowing through the refrigerant and is moved in the opening direction and associated with a first actuator (36) in which the first actuator (36) comprises a chamber (38) bounded by a first active surface (37) and containing a control filling (41), characterized in that the first actuator (36) is temperature-controlled. and high-pressure-dependent can be controlled, wherein the control filling (41) of the first actuator (36) has a filling density which is immediately below the critical density of the control filling (41) and that the first actuator (36) with a second actuator (46) is motion-coupled and that the second actuator (46) is temperature-independent and dependent on the high pressure controllable and adjustable to a maximum operating pressure for opening the passage opening (29).

2. Expansion valve according to claim 1, characterized in that the chamber (38) of the first actuator (36) comprises an inner volume which is temperature-dependent variable and the first active surface (37) controls with a lifting movement.

3. Expansion valve according to claim 1 or 2, characterized in that the first actuator (36) has a chamber (38), the bellows or membrane-like running and made of a heat-conductive material.

4. Expansion valve according to one of the preceding claims, characterized in that the chamber (38) of the first actuator (36) filled with a control filling (41) and the first actuator (36) controlled by the temperature of the high-pressure side refrigerant in the COP optimal high-pressure region is.

5. Expansion valve according to one of the preceding claims, characterized in that the chamber (38), in particular the inner contour of the chamber (38) is guided by a sleeve or webs.

6. Expansion valve according to one of the preceding claims, characterized in that the control filling (41) has a critical temperature below the critical temperature of the refrigerant.

7. Expansion valve according to one of the preceding claims, characterized in that the second actuator (56) is adjustable to a maximum opening pressure for opening the passage opening (29) and transmits its actuating movement to the first actuator (36).

8. Expansion valve according to claim 1, characterized in that the second actuator (46) has a membrane or plate spring-shaped element (49, 52) with a second active surface (48) on which the first actuator (36) is provided for movement coupled.

9. Expansion valve according to claim 8, characterized in that the membrane or dish spring-shaped element (49, 52) separates the valve housing (26) in a high-pressure chamber (28) and a room with atmospheric pressure.

10. Expansion valve according to claim 1, characterized in that the membrane or dish spring-shaped element has its own biasing force which is partially or completely adjustable to the maximum opening pressure.

11. Expansion valve according to claim 1, characterized in that on the second actuator (46) acting mechanical biasing force of a force storage element (51) is set such that when exceeding the predefined opening pressure, the valve element (33) of the first actuator (36) with a Valve stroke is controlled and increases the flow cross-section of the passage opening (29).

12. Expansion valve according to claim 11, characterized in that for adjusting the mechanical biasing force, a tensioning device is provided, which is preferably outside of the valve housing (26) adjustable and in particular exposed to atmospheric pressure.

13. Expansion valve according to claim 1, characterized in that the maximum stroke movement of the first actuator (36) by a Wegbegrenzungselement (54) is predetermined.

14. Expansion valve according to claim 13, characterized in that the Wegbegrenzungselement (54) has a further valve element (56) which limits a passage opening (29) and when the predefined opening pressure is exceeded lifting the valve element (56) to the valve seat (58) Modification of the flow cross-section of the passage opening (29) drives.

15. Expansion valve according to one of the preceding claims, characterized in that in a rest position of the at least one valve element (33) is given a predetermined Mindestdurchlassöffnung between the valve element (33) and the valve seat (32).

16. Transcritical or subcritical refrigeration or heat pump cycle (11) with an internal heat exchanger (14), characterized by an expansion valve (15) according to one of the preceding claims.