EP3569953A1 - Coolant circuit running device and method for operating a coolant circuit running device with a hybrid evaporator - Google Patents

Abstract

Refrigeration circuit device with a refrigerant circuit K through which refrigerant flows, comprising at least one compressor, a condenser, an expansion medium and at least one evaporator (1) and a coolant circuit thermally coupled to the refrigeration circuit K made of a water-based coolant or coolant mixture, the evaporator (1) and / or the condenser is provided with at least one refrigerant channel and at least one coolant channel running parallel to it, the refrigerant being CO ₂ and the evaporator (1) and / or the condenser being a coupled tube-in-tube system / has an inner tube (2) and an outer tube (3) surrounding it on the outside, with an annular gap (4) which is narrow in relation to the diameters of the inner tube (2) and outer tube (3) between the inner tube (2) and the outer tube (3) is formed, and wherein the specific volume of the refrigerant is matched to the size of the annular gap (4).

Description

The invention relates to a refrigeration cycle device with a refrigerant circuit through which refrigerant flows with at least one evaporator, a condenser, an expansion agent and at least one evaporator. In particular, the invention relates to such a refrigeration cycle device in which the refrigeration cycle thus formed is thermally coupled to a coolant circuit. The invention relates more particularly to a CO ₂ -driven refrigeration cycle and a corresponding refrigeration cycle device, the invention particularly relates to the design and operation of the evaporator as a so-called hybrid evaporator. The invention also relates to a method of operating such a refrigeration cycle device with a CO ₂ -based refrigerant and a glycol-based refrigerant in a refrigerant circuit coupled thereto.

In the known in the art such refrigeration cycle devices and corresponding operating method for refrigeration cycle devices with CO ₂ refrigerant is a problem in that only relatively low efficiencies can be achieved. Furthermore, the known in the prior art such devices have the disadvantage that it may lead to unwanted liquid hammer in a compressor of the refrigeration cycle by the not completely evaporated refrigerant. The previously known such refrigeration cycle devices also had the disadvantage that an uneven operating behavior was given. The temperature ranges and the operating ranges of such refrigeration cycle devices were also comparatively limited.

In contrast, it is the object of the present invention to provide a refrigeration cycle device with a CO ₂ -based refrigerant and at least one evaporator and a method for operating such a refrigeration cycle device, in which a higher efficiency is achieved with a smoother operating behavior and greater operational reliability over a long-term service life.

This object is achieved with a refrigeration cycle device with the features of claim 1 and with a method with the steps according to claim 9. Advantageous embodiments and modifications of the invention are the subject of the dependent claims.

According to the invention, a refrigeration cycle device is provided with a refrigerant circuit K through which at least one compressor, a condenser, an expansion medium and at least one evaporator and a refrigerant circuit thermally coupled to the refrigeration circuit K from a water-based coolant, for example glycol, or a coolant mixture, wherein the evaporator and / or the condenser is provided with at least one refrigerant passage and at least one coolant passage extending parallel thereto, wherein the evaporator and / or condenser is a coupled tube-in-tube system having an inner tube and an outer tube surrounding it, wherein between Inner tube and outer tube a narrow annular gap is formed.

A narrow annular gap between the inner tube and outer tube according to the invention is such an annular gap which has a small dimension in relation to the diameters of the outer tube and the inner tube, for example of the order of less than 10% of the diameter of the inner tube. According to the invention, the narrow annular gap is adapted in its dimension to the specific volume of the refrigerant, which is preferably a CO ₂ -based refrigerant. This means that the specific volume and the size of the annular gap are coordinated so that the performance of the evaporator or condenser is optimized and can be ensured. Thus, the invention provides an evaporator and / or condenser formed as a double tube, in which a refrigerant channel in the form of a narrow annular gap is present between an outer tube and an inner tube, while a water-based coolant or the like is present in the inner tube.

This may be present in the inner tube flowing or standing. The arrangement of the CO ₂ refrigerant in the annular gap between the outer tube and the inner tube can also be reversed, namely in the sense that the evaporator or the condenser at least partially provides a change between the outer tube and the inner tube, as will be described below.

The advantages of a so-formed hybrid evaporator for a refrigeration cycle device have been found in particular in refrigeration cycle devices based on a CO ₂ as refrigerant: With smaller temperature differences, a more stable operation and a higher efficiency can be achieved. By virtue of the evaporator provided with an inner tube for the coolant (eg, glycol) and a coolant flowing past the inner tube, surprisingly, better operating conditions have also been established. In particular, the harmful liquid blows on the compressor can thus be avoided if, as is often the case in the state of the art, not yet vaporized refrigerant is compressed in the compressor and can thus lead to damage to the compressor or even to destruction of the compressor. Due to the inventive design of the refrigeration cycle device, a relatively high efficiency in the performance was surprisingly achieved despite the lower temperature differences. Surprisingly, despite the low temperature differences between the internal coolant and the outside passing refrigerant, a high efficiency has been achieved. The larger heat transfer surface due to the internal coolant in the inner tube of the hybrid evaporator results in such a tube-in-pipe system, that CO ₂ operated refrigeration cycle devices can be operated very stable and quiet without the otherwise existing turbulence in the CO ₂ - refrigerant circuit.

According to an advantageous aspect of the invention, a preferably stationary coolant, for example a glycol-based coolant, is present in the inner tube of the evaporator and a CO ₂ refrigerant flows in the annular gap. The coolant in the relatively large inner diameter tube in relation to the diameter of the outer tube gives even in a significant amount of heat to the refrigerant from. In this way, not only the outer shell of the outer tube for the refrigeration effect is usable, but also the outer surface of the inner tube, in which the glycol is filled or allowed to flow as a coolant.

According to a further advantageous aspect of the invention, the inner tube and the outer tube of the evaporator are provided with a closely spaced diameter ratio of D ₁ / D ₂ of at least 4/5.

According to a further advantageous aspect of the invention, the outer tube is formed as a tube jacket which surrounds the inner tube of the evaporator at least in sections. The region of the refrigerant channel (outer tube) formed as a pipe jacket has the corresponding inlets and outlets for a flow of the refrigerant in the refrigeration cycle K. The evaporator can be realized as a compact, tubular evaporator. The design effort for the production of the tube-in-tube system of the evaporator according to the invention is relatively low.

According to a further advantageous embodiment of the invention, a narrow annular gap of less than 10% of the diameter D _{1 of} the inner tube is provided between the inner tube and the outer tube of the evaporator. Due to the comparatively narrow annular gap in which the refrigerant of the refrigeration cycle flows, an optimal speed of the CO ₂ refrigerant is achieved. The size of the annular gap is matched to the specific volume of CO ₂ used as the refrigerant.

According to a further advantageous aspect of the invention, an annular gap for refrigerant of the refrigeration circuit K is formed in the evaporator of the refrigeration cycle device, which is at least partially provided with thermal bridges between the inner tube and the outer tube. By means of such thermal bridges, which can be realized for example in the form of a metal spiral, an even better heat transfer to the evaporator is achieved. The heat absorption is increased, and a higher efficiency can thus be achieved with relatively little effort become. Alternatively, thermal bridges in the form of webs between pipe walls can be provided.

According to a further advantageous embodiment of the invention, a refrigeration cycle device is provided with an evaporator and / or a condenser with a tube-in-tube system, wherein the tube-in-tube system is constructed with an integrated change between inner tube and outer tube. The inner tube and the outer tube are thus combined at least once alternately in a single component of the refrigeration cycle device. Preferably, several changes are provided between the inner tube and the outer tube within the evaporator or the condenser. A change between the inner tube and the outer tube means that the refrigerant and the coolant, which are present in their respective channels in the inner tube and the outer tube, are alternately outside or inside. By such alternate exchange of inner tube / outer tube in one and the same component, a better balance in performance and operation can be achieved. In this way, the poorer heat transfer from the inner tube to the outside, which is quasi insulated by the outer tube surrounding it, is compensated. Also, with such a specific change of the inside / outside and thus an exchange of external refrigerant to internal refrigerant, a special operation of the refrigeration cycle device can be achieved. It is also conceivable that such a refrigeration cycle device for a heating operation in winter, for example, to defrost, is used and is used in reverse circuit for a cooling operation in summer in an air conditioner. With the inventive solution of an alternate exchange of inner tube to outer tube can thus be achieved with the same circuit a larger variety of modes of operation. Also can be further increase the efficiency of the evaporator and / or the capacitor.

According to a further related aspect of the invention, the annular gap is formed as a refrigerant passage, which over the longitudinal extent of the evaporator or the Condenser alternately outside and inside. The structural design of such a change between inside and outside annular gap can be realized with the skilled person known means. The inner tube and the outer tube can be realized for example via a tapered point and a line system. The structural design of the exchange between inner tube and outer tube can also be realized by the course of the channels, in particular the outer annular gap.

The invention also relates to a method according to claim 9 for operating a refrigeration cycle device according to one of claims 1 to 8 with at least one evaporator for a CO ₂ refrigerant for heat absorption of a refrigeration system or the like, the method being characterized by an evaporator serving as a hybrid evaporator in the form of a pipe-in-pipe system with an internally flowing or stationary coolant, in particular a glycol-based coolant, and a CO ₂ refrigerant flowing past it outside is operated. With such a procedure, a CO ₂ -based refrigeration cycle can be operated in a more stable manner. There are no undesirable pressure spikes, and liquid compression in the compressor is thus also effectively avoided. Not least, high efficiencies can still be achieved with comparatively low temperature differences in such a CO ₂ -based refrigeration cycle.

The method can be implemented both continuously and in clock mode. With the method thus operated, the refrigeration cycle device is also operated with surprisingly high efficiencies that set, although the coolant is located in an inner inner tube and the refrigerant flows outside in an annular gap of the outer tube over. Due to the coolant in the inner tube results in a dampening effect in clock mode.

Fig. 1

eine schematische perspektivische Ansicht eines erfindungsgemäßen Verdampfers für eine Kältekreislaufvorrichtung gemäß einem ersten Ausführungsbeispiel;

Fig. 2

eine schematische perspektivische Ansicht eines erfindungsgemäßen Verdampfers für eine Kältekreislaufvorrichtung gemäß einem zweiten Ausführungsbeispiel;

Fig. 3

eine schematische perspektivische Ansicht eines dritten Ausführungsbeispiels eines erfindungsgemäßen Verdampfers oder Kondensators für eine Kältekreislaufvorrichtung gemäß einem dritten Ausführungsbeispiel; und

Fig. 4

eine ausschnittsweise Längsschnittansicht des erfindungsgemäßen Verdampfers oder Kondensators gemäß dem dritten Ausführungsbeispiel.

Further advantages, features and embodiments of the invention will be explained in more detail below with reference to the accompanying drawings. In the drawings show:

Fig. 1

a schematic perspective view of an evaporator according to the invention for a refrigeration cycle device according to a first embodiment;

Fig. 2

a schematic perspective view of an evaporator according to the invention for a refrigeration cycle device according to a second embodiment;

Fig. 3

a schematic perspective view of a third embodiment of an evaporator or condenser according to the invention for a refrigeration cycle device according to a third embodiment; and

Fig. 4

a partial longitudinal sectional view of the evaporator or capacitor according to the invention according to the third embodiment.

The Fig. 1 shows a schematic perspective view of a first embodiment of an evaporator according to the invention for a refrigeration cycle device. The evaporator 1 is a double tube type evaporator, ie with a coupled tube-in-tube system and an inner tube 2 and an outer tube 3. The evaporator 1 is operated with a coolant circuit of a water-based coolant or coolant mixture and with a refrigerant is a CO ₂ -based refrigerant. The evaporator 1 has a refrigerant channel in an annular gap 4 between the inner tube 2 and the outer tube 3 for the CO ₂ refrigerant. The coolant in turn flows or is provided in the inner tube 2. The ratio of the diameter D ₁ / D ₂ of the inner tube (D ₁ ) to the outer tube (D ₂ ) is chosen so that a comparatively narrow annular gap 4 in the double tube of the evaporator 1 is formed. The annular gap 4 is provided in this embodiment to contain the flowing CO ₂ as a refrigerant. With the arrows in Fig. 1 and in Fig. 2 are the respective refrigerant flow in the annular gap 4 and the coolant flow in the inner tube 2 indicated by arrows.

The flows of refrigerant and coolant may also be provided in opposite directions. Due to the comparatively narrow annular gap 4, the refrigerant flowing outside in this exemplary embodiment is conducted through an annular gap 4 adapted to the specific volume of CO ₂ . The externally flowing refrigerant in the annular gap 4 virtually surrounds the coolant present in the inner tube 2, which may be, for example, a glycol or another water-based coolant. Surprisingly, this form of evaporator 1 has shown high efficiency in performance. A refrigeration cycle device operated thereby is characterized by a stable and quiet operation. Unwanted shocks in the refrigeration cycle device, in particular in front of the compressor, are thus avoided.

In the Fig. 2 is shown in a partial perspective schematic view of a second embodiment of an evaporator 1 according to the invention. In contrast to the previous embodiment, an additional heat transfer medium is here installed in the annular gap 4 between the inner tube 2 and the outer tube 3, namely in the form of a corrugated thermal bridge 5. The thermal bridge 5 can be used as a corrugated metal sheet between the outer tube 3 and the inner tube. 2 be introduced. In this way, the heat transfer is further improved. Otherwise, this second embodiment corresponds to the Fig. 2 essentially that of those previously described Fig. 1 , Again, the pipe diameter D ₁ of the inner tube 2 and the pipe diameter D ₂ of the outer tube 3 are provided such that a comparatively narrow annular gap 4 is formed, in which preferably a CO ₂ flows as a refrigerant. In the inner tube 2, a coolant flows or a coolant is included, which does not flow. The inventive evaporator 1, which could alternatively be configured as a capacitor, thus has a structurally simple shape in the form of a double tube or a tube-in-tube system. With a simple inner tube 2 and a surrounding outer tube 3 in a predefined diameter dimension so a highly efficient evaporator or condenser can be realized, which can be operated with a CO ₂ as a refrigerant in an efficient manner.

The Fig. 3 shows in a perspective schematic view of a third embodiment of an evaporator 1 according to the invention or capacitor. The relevant Fig. 4 shows this embodiment in a partial longitudinal sectional view to illustrate the principle of a change between inner tube / outer tube according to the present invention. In this evaporator 1, a change between the inner tube 2 and the outer tube 3 is provided according to the invention. Like this in FIG. 3 and FIG. 4 is indicated schematically, the lying in the outer annular gap 4 refrigerant passage is diverted at a change point in the interior of the evaporator 1, and the previously inner coolant passage in the inner tube 2 is passed to the outside. With such a periodic change between inner tube and outer tube, an evaporator 1 can be provided, which has an improved balance in the operation. Because of the poorer heat transfer of the inner tube to the outer tube, the latter quasi insulating the inner tube, so at least partially an exchange between inner tube and outer tube in the evaporator 1 can be realized. The double tube of the evaporator 1 changes at least once, but preferably several times, between the inner and outer annular gap 2, in which preferably the CO _{2 flows} as a refrigerant. With such a change of the inner and outer channels of the double tube of the evaporator 1 and the operation can be adapted to different applications. Winter heating, for example, can be used to defrost an iced evaporator. In the summer, however, such an evaporator / condenser can serve as a cooling element for an air conditioner. Also in this third embodiment of the invention, the annular gap 4 is provided as a comparatively narrow annular gap in relation to the diameters D ₁ and D ₂ of the inner tube and the outer tube, as has been explained to the embodiment described above. Preferably, the order of magnitude is in the range of 10% or less of the diameter D _{1 of} the inner tube. With such a narrow annular gap, it has been shown that a particularly good matching to the specific volume of the CO ₂ refrigerant is achieved. Such a Constructed evaporator 1 therefore has advantages in terms of efficiency, variability in the operation and applications in a refrigeration cycle device.

Claims (12)

Refrigeration cycle device with a refrigerant flow through the refrigerant circuit K from at least one compressor, a condenser, an expansion agent and at least one evaporator (1) and a thermally coupled to the refrigerant circuit K coolant circuit of a water-based coolant or coolant mixture, wherein the evaporator (1) and / or the condenser is provided with at least one refrigerant passage and at least one coolant passage extending parallel thereto, characterized in that the refrigerant is CO ₂ and that the evaporator (1) and / or the condenser is a coupled tube-in-tube system an inner tube (2) and an outer tube (3) surrounding said outer tube, wherein a narrow annular gap (4) is formed between the inner tube (2) and the outer tube (3) in relation to the diameters of inner tube (2) and outer tube (3), and that the specific volume of the refrigerant is adapted to the size of the annular gap (4). Refrigeration cycle device according to claim 1, characterized in that the inner tube (2) contains a preferably stationary coolant, in particular a glycol-based coolant, and that the CO ₂ refrigerant flows in the annular gap (4). Refrigeration cycle device according to claim 1 or 2, characterized in that the inner tube (2) and the outer tube (3) are provided with a closely spaced diameter ratio D ₁ / D ₂ of at least 4/5. Refrigeration cycle device according to one of the preceding claims, characterized in that the outer tube (3) is formed as a tube jacket which surrounds the inner tube (2) at least in sections. Refrigeration cycle device according to one of the preceding claims, characterized in that a narrow annular gap (4) of less than 10% of the diameter D _{1 of} the inner tube (2) is provided between the inner tube (2) and the outer tube (3). Refrigeration cycle device according to one of the preceding claims, characterized in that an annular gap (4) for refrigerant of the refrigeration circuit K in the evaporator (1) is formed which at least partially with thermal bridges (5) between the inner tube (2) and outer tube (3) is provided. Refrigeration cycle device according to one of the preceding claims, characterized in that the tube-in-tube system of the evaporator (1) and / or the condenser with an integrated change between the inner tube (2) and outer tube (3) is constructed. Refrigeration cycle device according to claim 7, characterized in that the annular gap (4) is formed as a refrigerant channel, which lies over the longitudinal extent of the evaporator (1) or capacitor alternately outside and inside. Method for operating a refrigeration cycle device according to one of the preceding claims with at least one evaporator (1) for a CO ₂ refrigerant for heat absorption of a refrigeration system or the like, characterized in that the evaporator (1) as a hybrid evaporator in the form of a tube-in-tube System is operated with an internally flowing or stationary coolant, in particular a glycol-based coolant, and a CO ₂ refrigerant flowing past it outside. A method according to claim 9, wherein the refrigerant in a region of the evaporator (1) formed as an annular gap (4) is externally flowed by a coolant filled in an inner tube (2). The method of claim 9 or 10, wherein the refrigeration cycle device is used for a cooling operation of a refrigerator. Method according to one of claims 9 to 11, wherein a continuous operation of the evaporator (1) takes place at a varying flow rate of the refrigerant.

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