Refrigerant collector for a refrigeration circuit

Abstract

The invention relates to a refrigerant collector (1) for a refrigeration circuit, comprising: - a housing (2) with a collecting chamber (3) for liquid refrigerant with temperature-variable density ρ R(T) and for refrigerator oil with temperature-variable density p L(T), - an inlet channel (4), via which the refrigerant and the refrigerator oil are supplied to the collecting chamber, - an outlet channel (6), via which the refrigerant and the refrigerator oil are removed from the collecting chamber and which is connected to the collecting chamber via a refrigerant suction opening (9), a geodetically lowest first oil duct (10) and a second oil duct (11), - and a float device (113, 213, 313, 413) which is located in the collecting chamber and has a float (115, 116, 215, 315, 415, 416) which is exposed to the liquid refrigerant and an effective density ps, for which, at different temperatures T 1 und T2 of the refrigerant where T2>T1, the following relationships apply: pR(T1)>ps>pR(T2), such that the float is located at the first temperature T1 at a geodetically high position of the collecting chamber and at the second temperature T2 at a geodetically low position of the collecting chamber. The following relationships should apply: ρR(T1)>ρL(T1) and ρR(T2)<ρL(T2), wherein the float device keeps the first oil duct closed at the first temperature T1.

Description

[0001] Refrigerant collector for a refrigeration circuit

[0002] The invention relates to a refrigerant collector for a refrigeration circuit, comprising:

[0003] - a housing with a collection chamber for liquid refrigerant with temperature-varying density PR(T) and for refrigeration oil with temperature-varying density pi_(T),

[0004] - an inlet channel through which the refrigerant and refrigeration oil are supplied to the collection chamber,

[0005] - an outlet channel through which the refrigerant and refrigeration oil are extracted from the collection chamber and which is connected to the collection chamber via a refrigerant intake opening, a geodetically lowest first oil channel and a second oil channel,

[0006] - and a float device located in the collection chamber with a float exposed to the liquid refrigerant and an effective density ps, for which, at different temperatures Ti and T2 of the refrigerant with T2>TI, the following relationships apply: PR(TI)>PS>PR(T2), SO that the float is located at a geodesically high position in the collection chamber at the first temperature Ti and at a geodesically low position in the collection chamber at the second temperature T2.

[0007] A refrigerant receiver is designed to prevent liquid refrigerant from reaching the compressor during certain operating conditions of the refrigeration cycle, thus providing mechanical protection. The receiver functions as a liquid separator, primarily diverting gaseous refrigerant. Any remaining liquid components are evaporated in a downstream internal heat exchanger. A key challenge of the receiver is returning the refrigeration oil, which is separated along with the liquid refrigerant, to the gaseous intake flow upstream of the compressor. This is achieved by routing the refrigerant intake within the receiver through the liquid refrigerant / oil mixture using a U-tube or a tube-in-tube configuration, and drawing the refrigeration oil into the intake gas via a small oil channel.

[0008] The design of this oil channel is particularly critical, as its diameter and position must be precisely matched to the mass flow rates, flow velocities, and fill quantities of refrigerant and refrigeration oil in the refrigerant receiver. Since compromises must always be made to ensure oil return at all operating points, a small amount of liquid refrigerant always enters the intake area via the oil channel. This amount should be kept to a minimum. When using CO2 as the refrigerant, another phenomenon occurs at low temperatures, starting at approximately -16°C (the exact temperature depends on the refrigeration oil used): Above this temperature, the refrigeration oil has a higher density than the liquid refrigerant, which consequently floats on top. An oil sump forms below the refrigerant, from which the refrigeration oil can be extracted.Depending on the refrigeration oil used and the temperature, the oil also dissolves in the liquid refrigerant, resulting in a layered transition zone with different oil concentrations.

[0009] Below this low temperature, later also referred to as the inverse temperature, the situation changes. The density of the liquid refrigerant is greater than the density of the refrigeration oil, causing the oil to float on top of the liquid refrigerant. This means that only liquid refrigerant is returned via the geodesically positioned oil channel at the bottom, while the refrigeration oil floating on top of the liquid refrigerant can no longer be returned. The refrigerant receiver fills with refrigeration oil, and the refrigeration cycle must be shut down.

[0010] A refrigerant receiver of the type mentioned above is described in CN 117 685 696 A. The density of the float is adjusted to the two operating temperatures Ti and T2 of the refrigerant such that at the lower temperature Ti, the float rises due to the higher density of the refrigerant and opens the lowest oil channel, and at the higher temperature T2, it sinks due to the lower density of the refrigerant and closes this oil channel. Such a float buoyancy characteristic is obviously unsuitable for the previously described low-temperature stratification of the refrigeration oil on the refrigerant, as this would result in only the refrigerant at the bottom being drawn in, and not the refrigeration oil.

[0011] The same applies to the refrigerant collector known from EP 3 929 505 B1, whose float floats on the liquid refrigerant at any operating temperature.

[0012] Another refrigerant receiver with a float device is known from JP H10-205 931 A. The lowest geodetic oil channel is always open, regardless of the state of the float device.

[0013] The present invention is based on the objective of constructively improving a generic refrigerant distributor with regard to the low-temperature stratification of the refrigeration machine oil on the refrigerant.

[0014] The solution to this problem arises from the features of claim 1. Accordingly, the following relationships should hold for the temperature-varying densities PR of the refrigerant and p of the refrigeration oil: PR(TI)>PL(TI) and PR(T2) <PL(T2), wobei die Schwimmervorrichtung den (geodätisch tiefsten) ersten Ölkanal bei der (niedrigeren) ersten Temperatur Ti geschlossen hält. Die Auftriebscharakteristik der Schwimmervorrichtung, d.h. deren effektive Dichte ist folglich derart auf die Dichten PR des Kältemittels und PL des Kältemaschinenöls abgestimmt, dass idealerweise nur Kältemaschinenöl aus dem ersten Ölkanal rückgesaugt werden kann. Unter der effektiven Dichte ist die Dichte eines homogenen Schwimmers zu verstehen, der unter Berücksichtigung der einzelnen Gewichtskräfte und des kinematischen Zusammenwirkens aller Komponenten der Schwimmervorrichtung dasselbe Auftriebsverhalten wie deren Schwimmer aufweist.

[0015] From a design perspective, hollow floats made of plastic or metal, which can be filled with gas or refrigerant, are suitable. Alternatively, floats made of solid material with the required density or density distribution are possible.

[0016] Advantageous embodiments of the invention are the subject of the dependent claims.

[0017] Preferably, the following relationships should hold for the effective density ps: PL(TI)>PS>PL(T2). The density PR of the refrigerant and the density PL of the refrigeration oil change linearly with temperature to a good approximation, where PR(TI)>PL(TI) and P R(T2) <PL(T2) ergibt, dass die Dichteänderung des Kältemaschinenöls einen flacheren Verlauf als die Dichteänderung des Kältemittels hat. Der Bereich der Dichte ps ist für das Intervall PL(TI)> PS>PL(T2) is therefore smaller than for the interval PR(TI)>PS>PR(T2), so that the float device at least in the case of complete low-temperature stratification obtains a more precise buoyancy characteristic with regard to the desired oil intake.

[0018] In the case of the inverse temperature Tj mentioned above with Ti <Tj<T2 schneiden sich die temperaturveränderlichen Dichteverläufe des flüssigen Kältemittels und des Kältemaschinenöls, so dass dort jeweils für die Dichte pi gilt: pi=pR(Ti)=pL(Tj). In weiterer Einschränkung des Intervalls der effektiven Dichte ps der Schwimmervorrichtung sollen bei der inversen Temperatur Tj die Beziehungen gelten: 0,95pj<ps(Tj)<1 ,05pi. Außerdem soll die Schwimmervorrichtung den (geodätisch höheren) zweiten Ölkanal bei der (niedrigeren) ersten Temperatur Ti geöffnet und bei der (höheren) zweiten Temperatur T2 geschlossen halten. Dadurch kann auch unterhalb der inversen Temperatur das auf dem Kältemittel aufschwimmende Kältemaschinenöl angesaugt werden.

[0019] The float device can have a valve actuated by the float, which opens and closes the oil channels. The float should actuate the valve either in the same direction or – for example, via a lever mechanism – in opposite directions.

[0020] Furthermore, the float device can have independent floats that open and close the oil channels.

[0021] Further features of the invention will become apparent from the following description and from the drawings with exemplary embodiments of refrigerant receivers according to the invention. Unless otherwise stated, identical or functionally equivalent components or features are designated with the same reference numerals. The drawings show, in a partially simplified representation:

[0022] Figure 1 shows a longitudinal section of a refrigerant collector without a float device according to the invention;

[0023] Figure 2 shows a temperature-density diagram for CO2 as a refrigerant and a typical refrigeration machine oil;

[0024] Figure 3 shows a first embodiment of a refrigerant collector according to the invention in a longitudinal section through the float device in a geodetically deep float position;

[0025] Figure 4 shows the refrigerant collector according to Figure 3 with the float device in a geodesically high float position;

[0026] Figure 5 shows a second embodiment of a refrigerant collector according to the invention in a longitudinal section through the float device in a geodesically low float position; Figure 6 shows the refrigerant collector according to Figure 5 with the float device in a geodesically high float position;

[0027] Figure 7 shows a third embodiment of a refrigerant collector according to the invention in a longitudinal section through the float device in a geodetic intermediate position;

[0028] Figure 8 shows a fourth embodiment of a refrigerant collector according to the invention in a perspective longitudinal section through the float device in a geodesically high float position.

[0029] The invention will be explained with reference to Figure 1, which shows an overall view of a refrigerant receiver 1 for a refrigeration circuit of a battery-electric vehicle. The refrigerant receiver 1 is installed in the vehicle in an upright orientation, which corresponds approximately to the direction of gravity g indicated by the adjacent arrow. The refrigerant receiver 1, which is shown here without a float device according to the invention, comprises a housing 2 with a collection chamber 3 for refrigerant and for refrigeration oil, which lubricates a refrigerant compressor located downstream in the refrigeration circuit.The refrigerant receiver 1 has an inlet channel 4, which, as a pipe, penetrates a geodesically high housing wall 5 and through which gaseous and liquid refrigerant and the refrigeration oil are supplied to the receiver 3, and an outlet channel 6, which, also as a pipe, penetrates the housing wall 5 and through which gaseous refrigerant and the refrigeration oil are extracted from the receiver 3 and supplied to a refrigerant compressor. The outlet channel 6, which extends almost to a (geodesically deep) housing bottom 7, is located in and concentric with an intake pipe 8 (pipe-in-pipe arrangement) and is connected to the receiver 3 on one side via a refrigerant intake opening 9 located in the geodesically high area of ​​the refrigerant receiver 1 and on the other side via a geodesically deep first oil channel 10 and a second oil channel 11. The oil channels 10, 11 penetrate the intake pipe 8 in the geodetically deep area of ​​the collection chamber 3.

[0030] The liquid refrigerant and the refrigeration oil are separated by gravity in the geodetically low section of the collection chamber 3, while the gaseous refrigerant remains in the geodetically high section. A baffle plate 12, positioned geodetically below and near the refrigerant intake opening 9 in the collection chamber 3, minimizes mixing of the liquid refrigerant with the gaseous refrigerant. The gaseous refrigerant is drawn in through the refrigerant intake opening 9, first via the annular gap between the intake pipe 8 and the outlet channel 6 towards the bottom of the housing 7, and then in the opposite direction via the outlet channel 6 by the refrigerant compressor, before exiting the refrigerant receiver 1. The refrigeration oil required for lubricating the refrigerant compressor is drawn from the collection chamber 3 via one of the oil channels 10, 11 by the refrigerant suction flow.

[0031] The diagram shown in Figure 2 illustrates the density PR(T) of liquid CO2 as a refrigerant and the density pi_(T) of a refrigeration oil as a function of temperature T. The refrigeration oil, marketed as Reniso ACC HV, is a commercially available lubricating oil for refrigerant compressors in refrigeration processes using supercritical CO2 as a refrigerant (R744). The diagram demonstrates, firstly, the significant temperature dependence of these densities PR(T) and pi_(T), and secondly, that there is an operating temperature Tj at which the density curves intersect, and for which, consequently, pi = pR(T) = p L (Ti). This operating temperature, subsequently referred to as the inverse temperature Tj with associated inverse density pi, is higher than an operational first temperature Ti and lower than an operational second temperature T2, i.e., Ti <Tj<T2. Vorliegend liegt Tj knapp unterhalb von -16°C.

[0032] In the operating range of the second temperature T2 (the diagram area to the left of the intersection point), the density PR(T2) of the liquid refrigerant is less than the density PL(T2) of the refrigeration oil, i.e., PR(T2) <PL(T2). Im Betriebsbereich der ersten Temperatur Ti (der Diagrammbereich rechts des Schnittpunkts) ist die Dichte PR(TI) des flüssigen Kältemittels größer als die Dichte pi_(Ti) des Kältemaschinenöls, d.h. PR(TI)> PL(TI). With ideal stratification of the liquid refrigerant and the refrigeration oil in the collection chamber 3, the refrigerant floats on the refrigeration oil in the second temperature range and, as a result of so-called refrigerant inversion, the refrigeration oil floats on the refrigerant in the first temperature range.

[0033] In the first temperature range, i.e., in the case of refrigerant inversion, the intake of liquid refrigerant is prevented by a float device, as described below, which keeps the first oil channel 10 closed at the first temperature Ti and open at the second temperature T2. Furthermore, the refrigeration oil required for lubricating the cold medium compressor is always mixed with the intake refrigerant by the float device keeping the oil channel 10 or 11 open that is at the geodetic level of the refrigeration oil, and the oil channel 11 or 10 closed that is at the geodetic level of the liquid refrigerant, depending on the current operating temperature and the corresponding densities of the liquid refrigerant and the refrigeration oil.

[0034] Figures 3 and 4 show the first embodiment of a refrigerant receiver 1 with a float device 113 according to the invention. This device comprises a guide 14 spaced parallel to the intake pipe 8, on which two independent floats 115 and 116 are guided so as to be movable in height between a geodetic lower stop 17 or 18 and a geodetic upper stop 19 or 20. The floats 115, 116 each have a concave outer surface area 21 which is in tight contact with the corresponding convex outer surface 22 of the intake pipe 8 in the circumferential region of the oil channels 10, 11. The oil channels 10, 11 and the stops 17 to 20 are positioned relative to each other such that the floats 115, 116, in the sunken state according to Figure 3, keep the first oil channel 10 open and the second oil channel 11 closed, and in the floating state according to Figure 4, keep the first oil channel 10 closed and the second oil channel 11 open.

[0035] The operating condition of the refrigerant receiver 1 shown in Figure 3 with sunken floats 115, 116 corresponds to the second temperature range, in which, for example, the operating temperature T2 = 0°C > Tj ~ -16°C, and the refrigeration oil has a density PL(T2) = 1002 kg / m³ 3 has and the refrigerant floating on it has a density PR(T2) = 927 kg / m³ 3 The float device 113 has an effective density ps = 1015 kg / m³. 3 , where ps > PL(T2) > PR(T2) and slightly larger than pi. The correspondingly lowered floats 115, 116 keep the first oil channel 10 open for the purpose of drawing in the refrigeration oil located geodesically at the bottom and the second oil channel 11 closed to the floating refrigerant.

[0036] Figure 4 shows the operating state of the refrigerant receiver 1 in the first temperature range, in which, for example, Ti = -20°C < Tj and the refrigerant has a density PR(TI) = 1031 kg / m³ 3has and the refrigeration oil with the lower density pi_(Ti) = 1017 kg / m 3 floats on the refrigerant. The effective density ps of the float device 113 is: ps = 1015 kg / m³ 3 < pi_(Ti) < PR(TI). Both floats 115, 116 float accordingly on the refrigeration oil, with the lower float 115 keeping the first oil channel 10 to the sunken refrigerant closed and the upper float 116 keeping the second oil channel 11 open for the purpose of drawing in the refrigeration oil floating on the refrigerant.

[0037] Figures 5 and 6 show the second embodiment of the refrigerant receiver 1 with the float device 213 according to the invention, which in this embodiment has only a float 215 guided on the guide 14 and a slide 223 actuated in the same direction by the float 215, which – analogous to the first embodiment – ​​is in tight contact with the intake pipe 8. According to Figure 5, the float device 213 is located in the second temperature range with T2 > Tj, in which the float 215 is in the geodetically lower stop position, i.e., at the stop 17, and the slide 223 keeps the first oil channel 10 to the refrigeration oil open and the second oil channel 11 to the liquid refrigerant closed. According to Figure 6, the float device 213 is located in the first temperature range with Ti < Tj, in which the float 215 is in the geodetically upper stop position, i.e.,The slide 223 is located at stop 19 and holds the second oil channel 11 open to the refrigeration oil and the first oil channel 10 closed to the liquid refrigerant. The oil channels 10 and 11 are held open by slots or elongated holes 24 or other shapes in the slide 223 for better visualization of transition zones.

[0038] The third embodiment of the refrigerant receiver 1, shown in Figure 7, has a float device 313 with only one float 315 guided on the guide 14 and a slide 323 actuated in the opposite direction by the float 315. The direction of actuation is reversed by a lever 26 mounted approximately centrally about a pivot point 25, to which the float 315 and the slide 323 are articulated. A transient intermediate position of the float device 313 is shown, in which both oil channels 10 and 11 are open. Analogous to the second embodiment, the slide 323 keeps the first oil channel 10 open and the second oil channel 11 closed when the float 315 is in its geodetically lower stop position, and vice versa.

[0039] The fourth embodiment of the refrigerant receiver 1 according to Figure 8 has – as in the first embodiment – ​​a float device 413 with two independent floats 415 and 416, which, however, in this embodiment are coaxial and in full sealing contact, are vertically movable directly on the intake pipe 8 and are guided between the two stops 17 and 19 and 18 and 20 respectively, which are attached directly to the intake pipe 8. The operating state of the refrigerant receiver 1 in the first temperature range with Ti < Ti is shown, in which the float 415 keeps the first oil channel 10 closed and the slide 416 keeps the second oil channel 11 open.

[0040] An alternative to the (passive) float devices, not shown, could be a refrigerant collector with an active, for example electromechanically operated, adjustment device for temperature-dependent opening and closing of the oil channels.

[0041] The invention is of course not limited to the existence of only two oil channels.

Claims

Patent claims 1. Refrigerant receiver (1) for a refrigeration circuit, comprising: - a housing (2) with a collection chamber (3) for liquid refrigerant with temperature-varying density PR(T) and for refrigeration oil with temperature-varying density pi_(T), - an inlet channel (4) through which the refrigerant and the refrigeration oil are supplied to the collection chamber (3), - an outlet channel (6) through which the refrigerant and the refrigeration oil are extracted from the collection chamber (3) and which is connected to the collection chamber (3) via a refrigerant intake opening (9), a geodetically lowest first oil channel (10) and a second oil channel (11), - and a float device (113, 213, 313, 413) located in the collection chamber (3) with a float (115, 116, 215, 315, 415, 416) exposed to the liquid refrigerant and an effective density ps, for which, at different temperatures Ti and T2 of the refrigerant with T2>TI, the following relationships apply: PR(TI)>PS>PR(T2), such that the float (115, 116, 215, 315, 415, 416) is located at a geodesically high position in the collection chamber (3) at the first temperature Ti and at a geodesically low position in the collection chamber (3) at the second temperature T2, characterized by the relationships: PR(TI)>PL(TI) and PR(T2) <PL(T2), wobei die Schwimmervorrichtung (113, 213, 313, 413) den ersten Ölkanal (10) bei der ersten Temperatur Ti geschlossen hält.

2. Refrigerant collector (1) according to claim 1 , characterized by the relationships: PL(TI)>PS>PL(T2).

3. Refrigerant collector (1) according to claim 1 or 2, characterized in that at an inverse temperature Tj of the collected refrigerant with Ti <Tj<T2 gilt: Pi=PR(Ti)=p L (Ti), where the following relationships apply to ps: 0.95pj <ps(tj)<1 ,05pi.

4. Refrigerant collector (1) according to one of the preceding claims, characterized in that the float device (113, 213, 313, 413) keeps the second oil channel (11) open at the first temperature Ti and closed at the second temperature T2.

5. Refrigerant collector (1) according to claim 4, characterized in that the float device (213, 313) has a slide (223, 323) actuated by the float (215, 315) which opens and closes the oil channels (10, 11).

6. Refrigerant collector (1) according to claim 5, characterized in that the float (215) actuates the slide (223) in the same direction.

7. Refrigerant collector (1) according to claim 5, characterized in that the float (315) actuates the slide (323) in the opposite direction.

8. Refrigerant collector (1) according to one of claims 4 to 7, characterized in that the float device (113, 413) has independent floats (115, 116, 415, 416) which open and close the oil channels (10, 11).

9. Refrigerant collector (1) according to one of the preceding claims, characterized in that the outlet channel (6) extends within an intake pipe (8) through which the oil channels (10, 11) and the refrigerant intake opening (9) are penetrated, wherein the refrigerant intake opening (9) opens into the collection chamber (3) above a baffle plate (12) arranged in the housing (2).

10. Refrigerant collector (1) according to claim 9, characterized in that the float device (113, 213, 313) comprises a guide (14) spaced parallel to the intake pipe (8), on which the float(s) (115, 116, 215, 315) are guided vertically movable between a geodetically lower stop (17, 18) and a geodetically upper stop (19, 20).

Images