EP3479903B1 - Centrifuge - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a centrifuge, in particular a laboratory centrifuge. Centrifuges of the type presented here are used, for example, in biotechnology, the pharmaceutical industry, medical technology and environmental analysis. Such a centrifuge is used to centrifuge a product, in particular a container or vessel with a sample or substance arranged therein, or a large number of such products at speeds which can be more than 3,000 rpm, for example more than 15,000 rpm. As a result of the centrifugation, accelerations acting on the product are to be generated which, for example, can be more than 15,000 x g (in particular more than 16,000 x g, more than 20,000 x g up to more than 60,000 x g). Centrifugation is intended to break down a mixture of substances formed by the sample or the substance into components of different densities. Depending on the chemical and / or physical properties of the substance mixture, specific control of the pressure and / or temperature conditions can also take place during centrifugation. To name just a few examples, the use of a laboratory centrifuge in connection with a polymerase chain reaction (PCR), a determination of the hematocrit, cytological examinations or the centrifugation of microtiter, blood bags, petroleum vessels or blood vessels, etc. the like.

1. a) Im Bereich der Zustandsänderung (I) - (II) findet eine Verdichtung des Kältemittels statt. Der Verdichter saugt hierbei überhitzten Dampf an, was in dem Diagramm gemäß Fig. 2 daran zu erkennen ist, dass sich der Zustandspunkt (I) rechts von der Taulinie befindet. Die während der Zustandsänderung (I) - (II) erzeugte Enthalpiedifferenz h₂-h₁ entspricht der zugeführten technischen Arbeit des Verdichters, die während der Komprimierung des Kältemittels durch den Verdichter verrichtet wird. Aus dem Verdichter tritt Dampf aus, welcher stärker überhitzt ist als bei dem Eintritt in den Verdichter. Die weitere Überhitzung ist bedingt durch die im Verdichter stattfindende polytrope Verdichtung und den Wärmeeintrag durch Reibung bei der Kompression sowie den Wärmeeintrag durch das verdichtete überhitzte Fluid.
2. b) Im Bereich der Zustandsänderung (II) - (III) wird das Kältemittel durch den Verflüssiger, welcher auch als Kondensator bezeichnet werden kann, unterkühlt. Die Druckverluste, die durch den inneren Widerstand entstehen, sind relativ gering, so dass die Zustandsänderung vereinfacht als isobar betrachtet werden kaum. Durch die näherungsweise isobare Änderung entsteht der größte Verlusteintrag oder es findet ein Nebeneintrag von Energie durch freie Konvektion an der Außenwand des Verflüssigers statt. In den Verflüssiger gelangt überhitzter Dampf, der durch die isobare Wärmeabfuhr bis unter die Taulinie unterkühlt wird, so dass das Kältemittel den Verflüssiger in flüssigem Zustand verlässt.
3. c) Während der Zustandsänderung (III) - (IV) wird in dem Expansionselement, das vereinfacht als adiabat betrachtet wird, das Kältemittel auf ein geringeres Druck- und Temperaturniveau entspannt. Hier erfolgt eine isenthalpe Zustandsänderung. Aus dem Expansionselement tritt dann das Kältemittel in einem Zustand als Nassdampf aus, was im Diagramm gemäß Fig. 2 daran zu erkennen ist, dass die Linie für die Zustandsänderung (III) - (IV) im Gebiet zwischen der Taulinie und der Siedelinie des Kältemittels endet. Die Besonderheit der Zustandsänderung (III) - (IV) im Bereich des Expansionselements im realen Prozess ist, dass hier das Kältemittel nicht vollständig auf das Druckniveau gemäß dem Anfangszustand (I) entspannt wird. Dieser Druckunterschied wird während der Zustandsänderung (IV) - (I) durch den Verdampfer verursacht der durch seinen inneren Strömungswiderstand eine Druckdifferenz herbeiführt.
4. d) Während der Zustandsänderung (IV) - (I) erfolgt in dem Verdampfer die eigentliche Nutzung des Kältekreislaufs in Form der Wärmeübertragung von dem Kälteträger, insbesondere der Zentrifugenkammer und/oder einem Sicherheitskessel und etwaigen Kühlrippen, in das Kältemittel. Durch die Temperatursenke, die durch die vorherigen Zustandsänderungen und den Eintrag von Arbeit erzeugt wurde, kann Kälte abgegeben werden, welche letztendlich genutzt wird, um die Temperatur des Produkts in der Zentrifugenkammer zumindest unterhalb eines Schwellwerts der Temperatur zu halten. In dem Verdampfer erfolgt über eine geeignete Wärmetauscherfläche ein Phasenwechsel des Kältemittels von einem dem Eingang des Verdampfers zugeführten Nassdampf zu einem den Verdampfer verlassenden überhitzten Dampf, der dann von dem Verdichter angesaugt wird.

As a result of the high speeds of a rotor of the centrifuge, on which the products are held (possibly pivotable as a result of the centrifugation force), there is a relatively high input of heat into a centrifuge chamber of the centrifuge. In order to guarantee defined temperatures of the product during centrifugation, cooling of the centrifuge chamber is therefore necessary, which is usually done by means of a refrigeration circuit. In conventional refrigeration circuits of this type used in centrifuges, a compressor, a condenser, an expansion element and an evaporator are used, with the generation of the cold by evaporation and liquefaction of refrigerant takes place in a closed refrigeration cycle. The artificial temperature sink created in this way is then used to dissipate heat from the centrifuge chamber. Fig. 1 FIG. 10 shows, by way of example and schematically, such a refrigeration cycle, which is a counterclockwise cycle in a diagram in which the logarithm of the pressure p is shown over the enthalpy h in FIG Fig. 2 is shown.

1. a) In the area of the change of state (I) - (II), the refrigerant is compressed. The compressor draws in superheated steam, which is shown in the diagram Fig. 2 it can be seen from the fact that the state point (I) is to the right of the dew line. The enthalpy difference h ₂ -h ₁ generated during the change of state (I) - (II) corresponds to the technical work supplied to the compressor, which is performed during the compression of the refrigerant by the compressor. Steam escapes from the compressor, which is more superheated than when it entered the compressor. The further overheating is due to the polytropic compression taking place in the compressor and the heat input through friction during compression and the heat input from the compressed, overheated fluid.
2. b) In the area of the change of state (II) - (III) the refrigerant is subcooled by the condenser, which can also be referred to as a condenser. The pressure losses caused by the internal resistance are relatively small, so that the change in state can hardly be viewed in simplified terms as isobaric. The approximately isobaric change results in the greatest loss input or there is a secondary input of energy through free convection on the outer wall of the condenser. Superheated vapor enters the condenser and is subcooled to below the dew line due to isobaric heat dissipation, so that the refrigerant leaves the condenser in a liquid state.
3. c) During the change of state (III) - (IV), the refrigerant is expanded to a lower pressure and temperature level in the expansion element, which is simply regarded as adiabatic. An isenthalpic change of state takes place here. The refrigerant then emerges from the expansion element in a state as wet steam, as shown in the diagram Fig. 2 it can be seen that the line for the change in state (III) - (IV) in the area between the dew line and the boiling line of the refrigerant ends. The special feature of the change of state (III) - (IV) in the area of the expansion element in the real process is that here the refrigerant is not completely expanded to the pressure level according to the initial state (I). This pressure difference is caused by the evaporator during the change of state (IV) - (I), which creates a pressure difference due to its internal flow resistance.
4. d) During the change of state (IV) - (I), the actual use of the refrigeration circuit takes place in the evaporator in the form of heat transfer from the refrigerant, in particular the centrifuge chamber and / or a safety vessel and any cooling fins, into the refrigerant. The temperature sink that was generated by the previous changes in state and the input of work, cold can be released, which is ultimately used to keep the temperature of the product in the centrifuge chamber at least below a threshold temperature. In the evaporator, a phase change of the refrigerant takes place via a suitable heat exchanger surface from a wet steam supplied to the inlet of the evaporator to a superheated steam leaving the evaporator, which is then sucked in by the compressor.

With the F-gas regulation (Regulation EU No. 517/2014 of the European Parliament and of the Council of April 16, 2014, which is valid from January 1, 2015), emissions of fluorinated greenhouse gases (F-gases) are to be expected by the year 2030 can be reduced to 21% in several steps specified in the F-gas regulation. As a result, previously commonly used refrigerants such as 1,1,1,2-tetrafluoroethane (R-134a) or R404a have to be replaced by alternative refrigerants, which is a challenge for centrifuges of the type presented here. The reason for this is that the centrifuges generate very high kinetic energies during operation, which are generated in the immediate vicinity of the refrigeration circuit and can destroy the inner workings of the centrifuge including the refrigeration circuit in the event of a crash of the centrifuge. In this way, in the event of a crash, the coolant can escape and catch fire, and in the event of a crash a spark causing the fire can also occur. In order to avoid a fire in the event of a crash, special requirements regarding the flammability of the refrigerant must be observed. On the other hand, a refrigerant that ensures the special requirements in terms of flammability must also be powerful enough to ensure the cooling required when the centrifuge is in operation.

STATE OF THE ART

Laboratory centrifuges with refrigeration circuits are, for example, sold by the applicant (see www.sigma-zentrifugen.de/de/produkte/zentrifugen.html) and in the publication DE 10 2012 002 593 A1 described.

The pamphlet EP 3 015 791 A1 suggests using a CO ₂ (R744) -based refrigerant or at least a hydrocarbon refrigerant in a centrifuge instead of a refrigerant R-134a, with mixtures also being used. This is intended to achieve a higher degree of efficiency of the refrigeration circuit, so that the refrigeration circuit can have a lower power consumption or, with the same power consumption, can bring about a stronger cooling effect. Possible refrigerants are, for example, propane (R-290), propene (R-1270), butane (R-600) and isobutane (R-600a), which can be easily recycled since they are naturally occurring Substances that do not lead to the undesirable greenhouse effect when the refrigerant is released. EP 3 015 791 A1 further suggests arranging an injection system in the evaporator of the refrigeration circuit, the pressure in the compressor being limited by controlling the injection. It is also proposed that the refrigeration circuit have at least one bypass to bypass an internal heat exchanger. In contrast to a refrigeration circuit in which a refrigerant R-134a is used, a greater pressure difference is required here in the refrigeration circuit between the low-pressure side and the high-pressure side, which in EP 3 015 791 A1 with a pressure of 1 bar on the low pressure side and 8 bar on the high pressure side. As a result, a changed safety design of the centrifuge, which must be designed for three times the working pressure, and / or a restriction of the compressor pressure is required. A hot gas bypass must also ensure that warm refrigerant is fed to the evaporator, so that ice formation, for example at the triple point of CO ₂ in the evaporator, must be avoided. This requires the hot gas bypass to be controlled as a function of the temperature in the suction line of the compressor, the hot gas bypass being expediently used in partial load operation. Alternatively, to avoid ice formation, the compressor can be regulated or the injection system mentioned can be controlled. During operation of the centrifuge and the refrigeration circuit, critical pressure increases in the refrigeration circuit are excluded due to the cooling capacity of the refrigeration circuit. However, a standstill of the centrifuge and the refrigeration circuit can be problematic, since there is an increase in pressure of the refrigerant in the non-operated refrigeration circuit (for example as a result of an increased ambient temperature) can result. To remedy this, suggests EP 3 015 791 A1 a refrigeration circuit cascade with an additional refrigeration circuit, which is only operated at a standstill. With the additional cooling circuit, the non-operated, for example, CO ₂ -based compressor cooling circuit is to be cooled during standstill in order to prevent a critical pressure increase in the CO ₂ -based compressor cooling circuit, while the further cooling circuit is during operation of the centrifuge and the CO ₂ -based compressor refrigeration cycle is not operated.

The pamphlet DE 10 2014 110 467 A1 suggests that a centrifuge not just use a refrigeration cycle. Rather, the cold should be generated by a primary cooling circuit, which is then thermally coupled via a heat exchanger to a secondary cooling circuit in which a refrigerant is circulated by a pump. The secondary cooling circuit arranged downstream of the primary cooling circuit thus only serves to transport the cold that has been generated by the primary cooling circuit from the heat exchanger to the centrifuge chamber. A conventional flammable refrigerant can then be used in the primary refrigeration circuit, which under certain circumstances has low costs, but can have a large specific enthalpy of vaporization. In contrast, a non-flammable heat transfer medium (such as, for example, cooling water with additives (for example salt or alcohol) that lower the freezing point) can be used for the secondary cooling circuit. If the primary cooling circuit and the secondary cooling circuit are then separated from one another by a safety wall, the combustible primary cooling circuit can be protected by the safety wall in the event of a crash, while the crash can at most have effects on the non-combustible secondary cooling circuit. The primary cooling circuit can extend below the secondary cooling circuit or a safety boiler or laterally offset to this in the housing of the centrifuge. A safety vessel can be fastened to the housing of the centrifuge via a clamp connection in such a way that in the event of a crash a relative movement of the safety vessel with respect to the housing of the centrifuge is possible. It is also proposed that lines of the primary cooling circuit are made from a mechanically stronger material than lines of the secondary cooling circuit, it also being possible for lines of the secondary cooling circuit to be specifically equipped with predetermined breaking points. In the event of a crash of the centrifuge, in which the kinetic energy cannot be completely absorbed by the safety vessel, the mechanical connection between the secondary cooling circuit and the primary cooling circuit can be separated due to the weaker design of the lines of the secondary cooling circuit, which is intended to prevent this that the energy as a result of the crash via the lines of the secondary cooling circuit to the primary cooling circuit is transferred, which could lead to damage, leakage of the refrigerant of the primary refrigeration circuit and thus a fire.

Further prior art, in which a magnetocaloric material is cyclically exposed to a magnetic field in a centrifuge in a refrigeration circuit, is from the publication DE 10 2014 107 294 B4 known.

DE 10 2014 110 467 A1 discloses a laboratory centrifuge with a primary refrigeration circuit which has a compressor, a condenser, a fan, a filter dryer and a heat exchanger with an integrated evaporator. A flammable refrigerant is used in the primary refrigeration circuit. In the heat exchanger, the cold generated in the primary cooling circuit is transferred to a secondary cooling circuit in which a non-combustible heat transfer medium is circulated by means of a pump. A cooling coil of the secondary cooling circuit extends for cooling a safety boiler in secondary pipelines around the safety boiler. A conventional flammable refrigerant can thus be used in the primary refrigeration circuit, which can have a large specific enthalpy of vaporization at comparatively low procurement costs. In contrast, the use of a non-combustible heat transfer medium in the secondary circuit can reduce the occurrence of a fire in the event of a rotor crash and the breakdown of the safety boiler.

EP 2 910 870 A1 discloses a general freezing or refrigeration device which has a primary refrigeration circuit with a compressor, a condenser and a throttle and a first evaporator, and a secondary refrigeration circuit with a compressor, a condenser, a consumer, a throttle and a second evaporator . A cascade condenser has the evaporator of the primary refrigeration circuit and the condenser of the primary refrigeration circuit, forming a heat exchanger between the refrigerants of the two refrigeration circuits. The generated cold is released to an object such as a freezer or cooling room via the evaporator of the secondary cooling circuit. The refrigeration device should be designed and operated in such a way that there is the possibility of freezing in the area of the evaporator of the secondary refrigeration circuit, which is why a defrosting function must be necessary. Furthermore, the dimensioning of the refrigeration device is carried out in such a way that when it is operated in an environment with a temperature that is higher than the critical temperature of the refrigerant, the refrigerant in the secondary refrigeration circuit passes through the Ambient air is heated, so that a gaseous phase results when the circulation of the refrigerant is stopped in the secondary refrigeration circuit, whereby a pressure increase in the secondary refrigeration circuit is established. EP 2 910 870 A1 is dedicated to the problem of at least reducing such a pressure increase in the secondary refrigeration circuit when the circulation of the refrigerant in the secondary refrigeration circuit is interrupted. EP 2 910 970 A1 proposes for this purpose to provide an expansion tank in the secondary refrigeration circuit, which ensures the interruption of the circulation of the refrigerant in the secondary refrigeration circuit in order to limit the pressure increase. The expansion tank is arranged below the cascade condenser. If the circulation of the refrigerant in the secondary refrigeration circuit is stopped, the condensed and liquefied refrigerant in the primary refrigeration circuit is quickly collected in the expansion tank, whereby a pressure increase in the secondary refrigeration circuit can be avoided.

OBJECT OF THE INVENTION

• der Umweltverträglichkeit,
• der Temperaturregelung in der Zentrifugenkammer,
• der Sicherheit gegenüber der Entstehung eines Brandes,
• der Kosten und/oder
• der Effizienz

verbessert ist.The invention is based on the object of proposing a centrifuge which, in particular with regard to

• environmental compatibility,
• the temperature control in the centrifuge chamber,
• the security against the development of a fire,
• the cost and / or
• of efficiency

is improved.

SOLUTION

The object of the invention is achieved according to the invention with the features of the independent patent claim. Further preferred embodiments according to the invention can be found in the dependent claims.

DESCRIPTION OF THE INVENTION

To simplify the description, the present description speaks of “generation of cold” and “transfer of cold”, although if the physical approach is correct, only a temperature sink can be generated to which heat is then transferred.

The centrifuge according to the invention, which is in particular a laboratory centrifuge, has a housing and a centrifuge chamber arranged in the housing. A rotatably mounted rotor (and driven by a motor) can be arranged in the centrifuge chamber. The centrifuge chamber usually surrounds a safety element at least in a partial circumferential area, which can also be a safety vessel extending completely in the circumferential direction (for example single-walled or double-walled).

According to the invention, the centrifuge has both a primary refrigeration circuit and a secondary refrigeration circuit. The secondary cooling circuit is thermally coupled to the primary cooling circuit (in particular via a heat exchanger), so that cold generated in the primary cooling circuit can be transferred to the secondary cooling circuit. Furthermore, the secondary refrigeration circuit is thermally coupled to the centrifuge chamber so that both the cold generated in the primary refrigeration circuit and transferred via the heat exchanger and the cold generated in the secondary refrigeration circuit can be cumulatively transferred to the centrifuge chamber.

According to the invention, the centrifuge has a control unit. The control unit has control logic that controls the primary refrigeration circuit and the secondary refrigeration circuit. The control is carried out in such a way that while the centrifuge is operating with a rotation of the rotor, cold is generated by means of the primary cooling circuit and / or the primary cooling circuit and the secondary cooling circuit are operated simultaneously.

While the prior art according to the document EP 3 015 791 A1 suggests only the use of a refrigeration circuit cascade with two refrigeration circuits in order to operate them alternately if necessary, the invention proposes for the first time to operate the primary refrigeration circuit and the secondary refrigeration circuit at the same time, so that both said refrigeration circuits are used to generate the one used to cool the centrifuge chamber Cold can make a contribution.

The two refrigeration circuits can be individually adapted (for example with regard to the changes in state, the pressure changes and the enthalpy difference and / or to the refrigerant used in the refrigeration circuits), which results in increased efficiency and / or an improved ratio with regard to the structural volume and the Costs compared to the refrigeration capacity that can be generated. Furthermore, the configuration according to the invention enables any choice of refrigerants in the two refrigeration circuits, which means that the scope for design in terms of efficiency, environmental compatibility, security against the occurrence of a fire and / or costs can be expanded. Under certain circumstances, the configuration according to the invention also enables new control options for controlling the temperature in the centrifuge chamber, depending on the configuration and coordination of the control and operation of the two refrigeration circuits.

In the context of the invention, a “refrigeration cycle” is understood to mean a cycle with a refrigerant, in which cold is generated using electrical power. It is possible here that a compression of the refrigerant and / or a change in the aggregate state of the refrigerant is generated in a refrigeration circuit, the refrigeration circuit uses a magnetocaloric effect, the refrigeration circuit has electrical Peltier cooling, the refrigeration circuit generates cold using a vortex tube or in in which the refrigeration cycle generates cold using an absorption refrigeration cycle or a compression refrigeration cycle. In contrast, a refrigeration circuit does not include a "cooling circuit" in which only a refrigerant is conveyed, in particular by means of a pump, and by means of which a transport of cold from a transfer location (such as a heat exchanger, in which a transfer of cold that has been generated externally by the cooling circuit takes place to the refrigerant of the cooling circuit) to the centrifuge chamber.

The "control unit" in the sense of the invention can be a control unit in the form of a singular structural unit, several interconnected or flanged control unit modules or several interconnected or networked control subunits.

While in principle the aforementioned or other configurations of the refrigeration circuits can be used within the scope of the invention for the configuration of the refrigeration circuit, the primary refrigeration circuit and / or the secondary refrigeration circuit have a suggestion of the invention a compressor, a condenser, an expansion device and an evaporator. This choice of the design of the refrigeration circuit has proven to be advantageous in terms of installation space, costs, energy efficiency and the refrigerants that can be used.

In the context of the invention, the primary refrigeration circuit can be designed as a high-pressure circuit, while the secondary refrigeration circuit can be designed as a low-pressure circuit. This enables the different design of the different refrigeration circuits with a potential for optimizing the generation of the required cold.

While the fundamental aim is that no flammable refrigerant is used in a centrifuge in order to avoid a fire, a further proposal of the invention in the centrifuge (due to the inventive design, possibly without a significantly increased risk of fire) can also A flammable refrigerant (in particular a flame-retardant refrigerant, a flammable refrigerant or a highly flammable refrigerant) can be used, especially if this is (only) used for the primary cooling circuit. This proposal is based on the knowledge that the lines and components of the primary refrigeration circuit u. U. can also be arranged outside a safety vessel of the centrifuge, so that even in the event of a centrifuge crash, the flammable refrigerant in the primary refrigeration circuit cannot escape from the lines and / or cannot be ignited.

For these or other embodiments, the invention further proposes that a non-flammable or hardly flammable refrigerant is used in the secondary refrigeration circuit. This configuration takes into account the fact that u. U. the refrigerant of the secondary refrigeration circuit is also arranged in the area of the safety boiler of the centrifuge or even inside the same, so that it is basically exposed to the risk of a fire in the event of a centrifuge crash. By using the non-flammable or hardly flammable refrigerant, however, the fundamental risk of a fire occurring can at least be reduced.

For a particular embodiment, the invention proposes that the primary refrigeration circuit has a flammable refrigerant (in particular a hardly inflammable refrigerant, a flammable refrigerant or a highly flammable refrigerant), while the secondary refrigeration circuit has a non-flammable or hardly inflammable refrigerant. Also it is possible that the primary refrigeration circuit has a non-flammable or hardly inflammable refrigerant and the secondary refrigeration circuit has a non-flammable or hardly inflammable refrigerant. In these cases, the two refrigeration circuits can have the same or different refrigerants.

The refrigerants are classified in terms of flammability and flammability, in particular in accordance with the standards DIN EN 378-1 and ISO 817 (see section 6.1.3.3 in the version valid on the filing date of the present patent application) as follows:
A "non-flammable refrigerant" is a refrigerant which, according to SN DIN EN 378-1, has no flame spread and is assigned to group A1 (low toxicity) or B1 (higher toxicity). This requires that when the test is carried out in air at 60 ° C and at a pressure of 1.013 bar, this refrigerant does not spread flame if it is a single-substance refrigerant. If a mixed refrigerant is used, this is also assigned to these groups if the WCFF (unfavorable distribution of the components of the mixture, which results in the highest flammability) of the mixture, determined by an analysis of the fractionation, was not found in a test at 60 ° C and 1.013 bar Flame spread causes.

" Flame-resistant refrigerants" are category A2L refrigerants in accordance with ISO 817 (Section 6.1.3.3) which, when tested at 60 ° C and a pressure of 1.013 bar, lead to flame spread, a lower explosion limit (LFL)> 3.5 vol. -%, have a heat of combustion that is <19,000 kJ / kg, and have a maximum flame propagation speed that is ≤ 10 cm / s when tested at 23 ° C and a pressure of 1.013 bar. A refrigerant R1234yf is preferably used as the flame-retardant refrigerant in this A2L category.

"Flammable refrigerants" are assigned to groups A2 (low toxicity) or B2 (higher toxicity) of the SN DIN EN 378-1 standard and, for a single-substance refrigerant and for a mixed refrigerant, meet the conditions that a When tested at 60 ° C and a pressure of 1.013 bar, the flame spreads, the lower explosion limit (LFL) being> 3.5% by volume and the heat of combustion being <19,000 kJ / kg.

Finally, refrigerants are regarded as "highly flammable refrigerants" which, according to the SN DIN EN 378-1 standard, are classified in groups A3 (low toxicity) and B3 (higher toxicity) get ranked. Single-substance refrigerants and mixed refrigerant use are assigned to these groups if a test at 60 ° C and a pressure of 1.013 bar results in flame spread and the lower explosion limit (LFL) ≤ 3.5% by volume or the heat of combustion is ≥ 19,000 kJ / kg.

Furthermore, in the present patent application, single-substance or mixture refrigerants are regarded as "flammable refrigerants" if they are assigned to one of the flammability classes A2, B2, A2L, B2L, A3, B3 according to SN DIN EN 378-1 and are hardly inflammable , are flammable or highly flammable, while the single-substance or mixture refrigerants, which are assigned to groups A1 or B1 and are not flammable, are referred to as "non-flammable refrigerants" .

In the refrigeration circuits, a heat exchanger can be arranged in the area of the condenser of the primary refrigeration circuit and / or in the transfer area between the two refrigeration circuits, i.e. the evaporator of the primary refrigeration circuit and the condenser of the secondary refrigeration circuit. Here, heat exchangers of any type can be used within the scope of the invention. For example (without being limited to this embodiment) a plate heat exchanger or a tube bundle heat exchanger can be used. For a preferred embodiment of the invention, a microchannel heat exchanger is used for a heat exchanger, in particular for the heat exchanger in the area of the condenser of the primary refrigeration circuit. This is understood to mean a heat exchanger in which a body or block (for example made of metal, in particular aluminum, consisting of one or more parts) has a plurality of small channels with a transverse extension of the channels or a diameter of the same of, for example, less than 2 mm or 1 mm from the Refrigerant is flowed through, with which a high degree of efficiency, a small filling volume of the refrigerant, a low weight and a compact design can be achieved. The refrigerant is therefore not routed in pipes here. It is possible that the channels of bores in the body or block are formed in the microchannel heat exchanger or the body or block is formed from several parts, for example welded or soldered together, which can have grooves and delimit the channels when connected to one another. For the use of the heat exchanger in the area of the condenser of the primary cooling circuit, ambient air can then be conducted past the body or block directly and / or through cooling fins attached thereto by means of a fan. With regard to a possible configuration of such a microchannel heat exchanger, reference is made to heat exchangers of this type, such as these are distributed, for example, by Danfoss or on the Internet site
www.kka-online.info/artikel/kka_Neue_Trends_bei_Komplettverfluessigungssaetzen_1406699
are described.

In principle, the components of the refrigeration circuits and the heat exchangers used can be arranged at any point in the centrifuge. For one proposal of the invention, the primary refrigeration circuit, a heat exchanger which couples the primary refrigeration circuit with the secondary refrigeration circuit, and at least part of the secondary refrigeration circuit are arranged on a side of a safety element, in particular a safety boiler, facing away from the centrifuge chamber. In other words, the rotor of the centrifuge on the one hand and the primary refrigeration circuit on the other hand are on different sides of the safety element, which means for the design of the safety element as a safety boiler that the rotor is located inside the safety boiler, while the primary refrigeration circuit is arranged outside the safety boiler is. In this case, even if a flame-retardant refrigerant or a flammable refrigerant is used in the primary refrigeration circuit, the development of a fire can be reliably prevented, which also enables the use of an inexpensive refrigerant in the centrifuge, at least for the primary refrigeration circuit.

There are various possibilities for distributing the components of the refrigeration circuits and the lines in the housing of the centrifuge. To name only one non-limiting example, the housing of the centrifuge can have an approximately rectangular horizontal section. In this case the security element is a security kettle with a circular horizontal section. Between a corner of the housing and the safety boiler with a circular horizontal section there is an intermediate space in which, within the scope of the invention, a compressor of the primary refrigeration circuit can be arranged particularly advantageously. A corresponding other gap results between another corner of the housing and the safety boiler. The compressor of the secondary refrigeration circuit can then be arranged in this other intermediate space. The heat exchanger, which thermally couples the primary refrigeration circuit and the secondary refrigeration circuit to one another, can in this case be arranged in an intermediate space which is between a Side wall of the housing and the safety boiler results, which is preferably an intermediate space between the compressor of the primary refrigeration circuit, the compressor of the secondary refrigeration circuit, the side wall of the housing and the safety boiler. On the one hand, the line connections (in particular from and to the heat exchanger) in the two refrigeration circuits can be kept relatively short as a result. On the other hand, in this way the heat exchanger (protected by the safety boiler) can be arranged in a particularly space-saving manner.

There are different options for controlling or regulating (in the following also just "control" for short) the compressors of the refrigeration circuits. For example, speed-regulated compressors can be used. However, these require a converter, additional components and / or increased sensor expenditure and control expenditure, which can increase costs. According to a proposal of the invention, the control logic of the control unit is designed in such a way that a compressor of the primary refrigeration circuit and / or a compressor of the secondary refrigeration circuit are / is controlled in ON operating states and OFF operating states. This means that non-speed-regulated compressors can also be used, which thus only have an active and an inactive operating state. In this case, the regulation of the compression output and thus the cold generated can be controlled via the duration of the ON operating states and the ratio of the duration of the ON operating states to the duration of the OFF operating states taking place in between.

It is entirely possible here for the two compressors of the refrigeration circuits to be switched to the ON operating state at the same time. If, on the other hand, an undesired increased peak current due to the simultaneous switching on of the compressors is to be avoided, the compressor of the primary refrigeration circuit and the compressor of the secondary refrigeration circuit are controlled to the ON operating state with a time delay for a proposal by the inventors. In contrast, the change to the OFF operating state can take place simultaneously or also with a time offset.

For a further proposal of the invention, the control logic of the control unit of the centrifuge is designed in such a way that the primary refrigeration circuit is independent of a required refrigeration capacity for cooling the centrifuge chamber (and thus independent of the deviation of the actual temperature inside the centrifuge chamber from the setpoint temperature) is operated in an ON operating state. As a result, the temperature fluctuations in the evaporator of the primary refrigeration circuit are not as pronounced as would be the case for an alternating change between an ON operating state and an OFF operating state in the primary refrigeration circuit. In this case, only the secondary refrigeration circuit is switched back and forth between an ON operating state and an OFF operating state, depending on the refrigeration capacity required to cool the centrifuge chamber. The background to this embodiment is that the possible amount of heat to be dissipated from the primary refrigeration circuit depends on the condensation temperature, this being increased according to the invention, which can result in a reduction in output. A more precise regulation of the temperature in the centrifuge chamber can possibly take place by means of such a different control of the two refrigeration circuits.

Advantageous further developments of the invention emerge from the patent claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are only exemplary and can come into effect alternatively or cumulatively without the advantages necessarily having to be achieved by embodiments according to the invention. Without changing the subject matter of the attached claims, the following applies to the disclosure content of the original application documents and the patent: Further features can be found in the drawings - in particular the illustrated geometries and the relative dimensions of several components to one another and their relative arrangement and operative connection. The combination of features of different embodiments of the invention or of features of different patent claims is also possible, deviating from the selected back-references of the patent claims, and is hereby suggested. This also applies to features that are shown in separate drawings or mentioned in their description. These features can also be combined with features of different patent claims. Features listed in the claims for further embodiments of the invention can also be omitted.

The number of features mentioned in the claims and the description are to be understood in such a way that precisely this number or a greater number than the stated number is present without the need for the explicit use of the adverb "at least". For example, when an element is mentioned, it is to be understood that there is exactly one element, two elements or more elements. These characteristics can be supplemented by other characteristics or be the only characteristics that make up the product in question.

The reference signs contained in the claims do not restrict the scope of the subject matter protected by the claims. They only serve the purpose of making the claims easier to understand.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

zeigt schematisch einen einzigen Kältekreislauf einer Zentrifuge mit den in dem Kältekreislauf auftretenden Zuständen (I) bis (IV) des Kältemittels (Stand der Technik).

Fig. 2

zeigt den Kältekreislauf gemäß Fig. 1 in einem linksläufigen Kreisprozess mit der Darstellung der Zustände (I) bis (IV) mit dem Logarithmus des Drucks p über der Enthalpie h (Stand der Technik).

Fig. 3

zeigt eine Zentrifuge mit einem Primär-Kältekreislauf und einem Sekundär-Kältekreislauf und Kennzeichnung der Zustände der Kältemittel (I) bis (VIII) in schematischer Darstellung.

Fig. 4

zeigt die beiden linksläufigen Kreisprozesse des Primär-Kältekreislaufs und des Sekundär-Kältekreislaufs mit den Zuständen (I) bis (VIII) bei Darstellung des Logarithmus des Drucks p über der Enthalpie h für eine Kälteanlage gemäß Fig. 3.

Fig. 5

zeigt eine Zentrifuge in einer teilgeschnittenen Draufsicht oder einem Horizontal-schnitt.

Fig. 6

zeigt die Zentrifuge gemäß Fig. 5 in einer teilgeschnittenen räumlichen Ansicht schräg von oben und links vorne.

Fig. 7

zeigt die Zentrifuge gemäß Fig. 5 und 6 in einer teilgeschnittenen räumlichen Ansicht schräg von oben und rechts hinten.

Fig. 8

zeigt die Zentrifuge gemäß den Fig. 5 bis 7 in einer teilgeschnittenen horizontalen Ansicht schräg von rechts hinten.

Fig. 9

zeigt eine Steuerung der Verdichter der Kältekreisläufe einer Zentrifuge für eine Dauerkühlung.

Fig. 10

zeigt die Steuerung der Verdichter der Kältekreisläufe für eine Temperaturregelung mit zeitversetzter Ansteuerung der Verdichter in einen ON-Betriebszustand.

Fig. 11

zeigt eine Steuerung der Verdichter der Kältekreisläufe der Zentrifuge mit permanentem Betrieb des Verdichters des Primär-Kältekreislaufs und temperatur-abhängiger alternierender Ansteuerung des Sekundär-Kältekreislaufs in ON-Betriebszustände und OFF-Betriebszustände.

In the following, the invention is further explained and described with reference to preferred exemplary embodiments shown in the figures.

Fig. 1

shows schematically a single refrigeration circuit of a centrifuge with the states (I) to (IV) of the refrigerant (prior art) occurring in the refrigeration circuit.

Fig. 2

shows the refrigeration cycle according to Fig. 1 in a left-hand cycle with the representation of the states (I) to (IV) with the logarithm of the pressure p over the enthalpy h (state of the art).

Fig. 3

shows a centrifuge with a primary refrigeration circuit and a secondary refrigeration circuit and identification of the states of the refrigerants (I) to (VIII) in a schematic representation.

Fig. 4

shows the two counterclockwise cycle processes of the primary refrigeration circuit and the secondary refrigeration circuit with states (I) to (VIII) when the logarithm of the pressure p is plotted against the enthalpy h for a refrigeration system according to FIG Fig. 3 .

Fig. 5

shows a centrifuge in a partially sectioned plan view or a horizontal section.

Fig. 6

shows the centrifuge according to Fig. 5 in a partially cut three-dimensional view obliquely from above and front left.

Fig. 7

shows the centrifuge according to Fig. 5 and 6th in a partially sectioned spatial view obliquely from above and right behind.

Fig. 8

shows the centrifuge according to FIG Figures 5 to 7 in a partially sectioned horizontal view obliquely from the right behind.

Fig. 9

shows a control of the compressors of the refrigeration circuits of a centrifuge for continuous cooling.

Fig. 10

shows the control of the compressors of the refrigeration circuits for temperature control with time-delayed activation of the compressors in an ON operating state.

Fig. 11

shows a control of the compressor of the refrigeration circuit of the centrifuge with permanent operation of the compressor of the primary refrigeration circuit and temperature-dependent alternating control of the secondary refrigeration circuit in ON operating states and OFF operating states.

FIGURE DESCRIPTION

Fig. 1 shows a centrifuge 1 according to the prior art. The centrifuge 1 has a refrigeration system 2. The refrigeration system 2 here has a single refrigeration circuit 3. In the refrigeration circuit 3 are a compressor 5, which is driven by a motor 4 operated with electrical energy, a liquefier or condenser 6, an expansion element 7 (in particular an expansion valve or a throttle) and an evaporator 8 in this order via lines 9a, 9b , 9c, 9d connected to one another in a closed circuit.

In Fig. 1 the circled numbers identify the states (I), (II), (III) and (IV) of the coolant used in the refrigeration circuit 3. Between the compressor 5 and the expansion element 7, the condenser 6 with the lines 9a, 9b forms a high-pressure circuit part 10, while between the expansion element 7 and the compressor 5 the evaporator 8 with the lines 9c, 9d forms a low-pressure circuit part 11. In the area of the evaporator 8, the cold generated in the cooling circuit 3 is transferred to the centrifuge chamber 12, which is only shown schematically here. An energetic exchange of the refrigeration circuit 3 takes place via the provision of cold for the centrifuge chamber 12 by the evaporator 8, on the one hand, by applying electrical power to the motor 4 and compressing the refrigerant in the area of the compressor 5. On the other hand, in the area of the condenser 6 a heat exchange with the ambient air, whereby a fan can be driven with electrical power. The condenser 6 thus forms a heat exchanger 13.

Fig. 2 shows the counter-clockwise cycle, like this with steps a) to d) and the changes of state (I) - (II), (II) - (III), (III) - (IV) and (IV) - (I) in the introductory part of the description under the heading "Technical Field of the Invention" has been described.

Fig. 3 schematically shows a centrifuge 1 according to the invention, in which the refrigeration system 2 has a primary refrigeration circuit 14 and a secondary refrigeration circuit 15. The primary refrigeration circuit 14 is coupled to the secondary refrigeration circuit 15 via a heat exchanger 16. The secondary refrigeration circuit 15 basically corresponds to the refrigeration circuit 3 according to FIG Fig. 1 , this also having corresponding states (I), (II), (III) and (IV). In the secondary refrigeration circuit 15, components which are contained in the refrigeration circuit 3 are identified by the same reference symbols, and these are referred to below with the same designations. With an otherwise corresponding design, the evaporator 6 communicates differently in the secondary refrigeration circuit 15 Fig. 1 not with the ambient air. Rather, the evaporator 6 is part of the heat exchanger 16.

In the primary refrigeration circuit 14 are a compressor 17, which is driven by a motor 18 driven by means of electrical energy, a condenser 19, which is designed here as a heat exchanger 20 and is thermally coupled to the ambient air via a fan, an expansion element 21 and a Evaporator 22, which together with condenser 6 forms heat exchanger 16, connected to one another in a closed circuit via lines 23a, 23b, 23c, 23d. In the primary refrigeration circuit 14, the states (V), (VI), (VII) and (VIII) identify the states of the refrigerant between the evaporator 22 and the compressor 17 (state V), between the compressor 17 and the condenser 19 ( State VI), between the condenser 19 and the expansion element 21 (state VII) and between the expansion element 21 and the evaporator 22 (state VIII). In the primary refrigeration circuit 14, the refrigerant also circulates between a high-pressure circuit part and a low-pressure circuit part, as has been explained above for the refrigeration circuit 3. The primary refrigeration circuit 14 forms a high-pressure circuit 24, while the secondary refrigeration circuit 15 forms a low-pressure circuit 25.

An energetic exchange of the primary refrigeration circuit 14 takes place via the provision of cold for the heat exchanger 16 by the evaporator 22, on the one hand, by applying electrical power to the motor 18 and compressing the refrigerant in the area of the compressor 17. On the other hand, in the area of the condenser 19 a heat exchange with the ambient air, whereby a fan can be driven with electrical power. An energetic exchange of the secondary refrigeration circuit 15 takes place via the provision of cold by the heat exchanger 16 to the condenser on the one hand by applying electrical power to the motor 4 and compressing the refrigerant in the area of the compressor 5, on the other hand in the area of the evaporator 8 cooling of the centrifuge chamber 12.

The refrigeration circuits 14, 15 can be operated simultaneously. On the basis of the introduction of electrical energy via the motor 18 and the compressor 17 driven by it, cold is generated in the primary refrigeration circuit 14, which is transferred via the heat exchanger 16 to the secondary refrigeration circuit 15 in that the evaporator 22 releases cold to the condenser 6 and in that the transferred cold is used in the condenser 6 to liquefy the refrigerant of the secondary refrigeration circuit 15. In the secondary refrigeration circuit 15, additional refrigeration is generated with the introduction of electrical energy via the motor 4 and the compressor 5 driven by it. The refrigeration generated in this way by the primary refrigeration circuit 14 and the secondary refrigeration circuit 15 is then accumulated by the evaporator 8 of the secondary refrigeration circuit 15 are transferred to the centrifuge chamber 12. It is possible that the mass flows, the refrigerants and / or the pressures in the two refrigeration circuits 14, 15 are different.

Fig. 4 shows the two counterclockwise cycle processes of the two refrigeration circuits 14, 15 in a diagram in which the logarithm of the pressure p is shown over the enthalpy h. The coupling of the two refrigeration circuits 14, 15 via the heat exchanger 16 is based on the principle that the coolant in the secondary refrigeration circuit 15 can be cooled more deeply as a result of the supply of cold via the heat exchanger 16 from the primary refrigeration circuit 14 than this This is the case when the coolant cooling the centrifuge chamber 12 is thermally coupled to the environment via a condenser 6 in the form of a heat exchanger 13. The secondary cooling circuit 15 absorbs heat from the centrifuge chamber 12 and transfers it in the heat exchanger 16 via the condenser 6 of the secondary cooling circuit 15 to the primary cooling circuit 14, here the evaporator 22 of the heat exchanger 16.

In Fig. 4 correspond to the respective cycle processes (I) - (II), (II) - (III), (III) - (IV), (IV) - (I) for the secondary refrigeration circuit 15 and (V) - (VI), (VI) - (VII), (VII) - (VIII), (VIII) - (V) for the primary refrigeration circuit 14 basically the in Fig. 2 cycle process shown and described in the introduction to the description, but these cycle processes then take place at different pressures, temperatures and specific enthalpies.

The heat transfer between the refrigeration circuits 14, 15 takes place in the area of the heat exchanger 16, which is shown in the cycle processes according to FIG Fig. 4 in the changes of state (II) - (III) of the secondary refrigeration circuit 15 and (VIII) - (V) of the primary refrigeration circuit 14 is shown. The evaporation temperature of the primary refrigeration circuit 14 must be slightly lower than the condensation temperature of the secondary refrigeration circuit 15 in order to enable the required heat transfer through an artificial temperature sink. The lower the temperature gradient in the heat exchanger 16, the greater the mass flow in the primary refrigeration circuit 14 must be selected. The significant reduction in the final temperature of the liquefaction in the area of the condenser 6 of the secondary refrigeration circuit 15 increases the enthalpy difference required for the evaporation of the refrigerant. According to the enthalpy difference, more heat can be removed from the centrifuge chamber 12. In addition, the achievable injection temperature in the evaporator 8 of the primary refrigeration circuit 15 is reduced. The lower injection temperature creates a greater temperature gradient between the refrigerant and the centrifuge chamber 12, which improves the dissipation of heat.

With the diagram according to Fig. 4 the operation of the refrigeration system 2 formed with the primary refrigeration circuit 14 and the secondary refrigeration circuit 15 is only intended to be shown qualitatively. In Fig. 4 the cycle processes are shown by way of example for a refrigerant in the refrigeration circuits 14, 15, which is each designed as a refrigerant R1234yf. In this diagram, h = 200 kJ / kg and s = 1 kJ / (kg K) at 0 ° C on the boiling curve have been selected as the reference state.

It is possible for the injection temperatures in the evaporator 8 of the secondary cooling circuit 15 to be reduced to a minimum by using the two refrigeration circuits 14, 15 connected in series. The reduced inlet temperature of the refrigerant in the area of the condenser 6 increases the specific internal energy to be absorbed by the refrigerant, which is necessary in order to completely evaporate it. Thus, the Amount of heat that can be transferred from the centrifuge chamber 12 to the refrigerant. With the refrigeration system 2 according to the invention, it is possible, due to the respective vapor pressure curve, to use a refrigerant which has less enthalpy of vaporization and a higher injection temperature at the same pressure levels. The refrigeration system 2 according to the invention can u. U. are operated at significantly higher ambient temperatures than a refrigeration system 2 according to Fig. 1 with only one refrigeration circuit 3. This does indeed result in a loss of performance. However, this loss of performance does not affect the refrigeration system as much as a single-stage refrigeration system 3.

With the refrigeration system 2 according to the invention with two refrigeration circuits 14, 15 coupled to one another, it is possible u. U. also to use a flammable refrigerant in the primary refrigeration circuit 14, since the primary refrigeration circuit 14 can be spatially separated from the centrifuge chamber 12 via a safety element 26, in particular a safety boiler 27.

Figures 5 to 8 show an exemplary structural design of a centrifuge 1 with the integration of the components required for the refrigeration system 2. The centrifuge 1 has a housing 28, which is basically angular in horizontal section and can be closed by means of a cover 29. In the housing 28, the safety element 26 in the form of the safety vessel 27, in which the rotor rotates, is arranged in a sub-space 30 which is accessible via the cover 29. In contrast, essential components of the refrigeration system 2, in particular the compressors 5, 17, the heat exchanger 16 and the condenser 19 or heat exchanger 20 are in an adjacent subspace 31, which is not accessible via the cover 29, so that the housing 28 is closed here and associated lines 9, 23 are arranged. Electronic control devices, a control panel and displays of the centrifuge 1 are also arranged in the subspace 31 and the closed housing part connected to it. In Fig. 5 the subspaces 30, 31, which are not separated from one another by a wall here, are separated from one another by the fictitious curved separating plane shown in broken lines.

For the exemplary embodiment shown, the compressor 17 of the primary refrigeration circuit 14 is arranged in an intermediate space 32 between a corner 33 and the safety boiler 27. The compressor 5 of the secondary refrigeration circuit 15 is arranged in an intermediate space 34 between an adjacent corner 35 and the safety boiler 27. The heat exchanger 16 is in turn arranged in an intermediate space 36 between a side wall 37 connecting the two corners 33, 35 and the safety boiler 27.

In Fig. 8 it can be seen that the two expansion elements 7, 21 are arranged in a plane below the safety boiler 27 (laterally offset to this in the subspace 31 or even below the safety boiler 27 in the subspace 30), which results in a compact design and / or lines from the expansion elements 7, 21 to the evaporator 8 can be kept short.

Schematic is in Fig. 3 outlines that the two refrigeration circuits 14, 15 are controlled via an electronic control unit 39 having control logic 38. The control unit 39 controls the power of the compressors 5, 17 via control lines 40, 41, which is done by directly controlling the electrical application of the motors 4, 18 or by transmitting a control signal to the motors 4, 18, in which, u. U. By means of a control sub-unit, the suitable electrical application of the motors 4, 18 is controlled. For the control of the refrigeration circuits 14, 15 by the control unit 39, the invention also includes the following possibilities:
In Fig. 9 the operating state 43 of the compressors 5, 17 or the motors 4, 18 is shown over the time 42, which results from the activation of the same by the control unit 39. There is no speed regulation of the compressors 5, 17 here, but rather they are switched to an ON operating state 45 and an OFF depending on the cooling requirement, which is determined on the basis of a temperature sensor 44 in the centrifuge chamber 12, whose measurement signal is also fed to the control unit 39 -Operating state 46 switched, which is done by activating or deactivating the motors 4, 18. Fig. 9 shows the control for ensuring permanent cooling with maximum cooling capacity. In Fig. 9 the controlled operating behavior of the secondary refrigeration circuit 15, that is to say of the compressor 5, is shown with a solid operating curve 47, while the operating curve 48 for the operating behavior of the primary refrigeration circuit 14 and thus of the compressor 17 is shown with a broken line. For the permanent cooling, the operating states are permanently switched to the ON operating state 45. While the switchover can also take place simultaneously, shows Fig. 9 that the switchover to the ON operating state 45 for the operating curves 47, 48 takes place with a time offset 49, whereby a reduction in the peak currents is brought about by a temporal separation of the two peaks as a result of the switchover of the motors 4, 18 to the ON operating state 45 can. For the illustrated embodiment, the activation of the secondary cooling circuit 15 takes place before the activation of the primary circuit 14, while a reverse time offset 49 is also possible.

Fig. 10 shows the corresponding relationships for a control (which also includes a regulation) of a predetermined temperature in the centrifuge chamber 12, which does not require the provision of the maximum cooling capacity. For this purpose, the operating states of the refrigeration circuits 14, 15 are alternately switched between the ON operating state 45 and the OFF operating state 46, with the frequency of the switching back and forth and / or the ratio of the time periods for the ON operating state 45 and the OFF operating state 46 correlates with the provided cooling capacity, so that, depending on the required cooling capacity, the control unit can be used for suitable control by influencing the frequency of switching back and forth and the ratios of the time periods. A time offset 49 for switching from the OFF operating state 46 to the ON operating state 45 can also be used for this switching back and forth, the switching back from the ON operating state 45 to the OFF operating state 46 preferably then taking place without a time offset 49 . In this case, the two refrigeration circuits 14, 15 are switched over at the same frequency to provide a constant refrigeration capacity, but in the illustrated embodiment, given the time offset 49, the ON operating state 45 for the secondary refrigeration circuit 15 is longer than for the primary refrigeration circuit 14 (without this necessarily being the case).

Fig. 11 shows a modified temperature control, in which the primary cooling circuit 14 is permanently switched to the ON operating state 45, so that it provides a permanent heat sink. Here, the control of the cold supplied to the centrifuge chamber 12 is controlled only by the decrease of the cold from the primary refrigeration circuit 14 by the secondary refrigeration circuit 15 by switching the secondary refrigeration circuit 15 back and forth between the ON operating state 45 and the OFF operating state 46 takes place, whereby here to control or regulate the temperature in the centrifuge chamber 12 and thus the cold supplied to the centrifuge chamber 12, the ratio of the time periods of the ON operating states and the OFF operating states is influenced.

$$h_{\mathit{II}}=390\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{IIs}}=375\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{III}}=188\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{IV}}=188\frac{\mathit{kJ}}{\mathit{kg}}$$

Enthalpiedifferenzen : $$\mathrm{\Delta }{h}_{\mathit{II}-I}=40\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{h}_{\mathit{IIs}-I}=25\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{h}_{\mathit{III}-\mathit{II}}=-202\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{h}_{I-\mathit{IV}}=162\frac{\mathit{kJ}}{\mathit{kg}}$$

Massenstrom: $${\dot{m}}_{\mathit{ND}}=\mathrm{0,0044}\frac{\mathit{kg}}{s}$$

Kälteleistung: Q̇_o = ṁ_ND · Δh _I-IV = 0.7128 kW Kondensatorleistung ND: Q̇ _Z1 = ṁ_ND · Δh_III-II = -0,899 kW Verdichterleistung: P_ND = ṁ_ND · Δh _II-I = 0,176 kW Leistungszahl: $${\epsilon }_{\mathit{ND}}={\mathit{EER}}_{\mathit{ND}}=\frac{{\dot{Q}}_o}{P_{\mathit{ND}}}=\mathrm{4,05}$$

b) Primär-Kältekreislauf 14 Temperaturen: T_V = -5°C T_VI = 55°C T_VII = 40°C T_VIII = -15°C Drücke: p_III = 2,3 bar P_IV = 10 bar Enthalpien: $$h_V=358\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{VI}}=422\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{VIs}}=407\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{VII}}=248\frac{\mathit{kJ}}{\mathit{kg}}$$

$$h_{\mathit{VIII}}=248\frac{\mathit{kJ}}{\mathit{kg}}$$

Enthalpiedifferenzen: $$\mathrm{\Delta }{h}_{\mathit{VI}-V}=64\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{h}_{\mathit{VIs}-V}=49\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{h}_{\mathit{VII}-\mathit{VI}}=-174\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{h}_{V-\mathit{VIII}}=110\frac{\mathit{kJ}}{\mathit{kg}}$$

Massenstrom: $${\dot{m}}_{\mathit{HD}}=\mathrm{0,008}\frac{\mathit{kg}}{s}$$

Verdampferleistung HD: Q _Z2 = ṁ_HD · Δh_V-VIII = 0,889 kW Kondensatorleistung: Q̇_U = ṁ_HD · Δh_VII-VI = -1,382 kW Verdichterleistung: P_HD = ṁ_HD · Δh_VI-V = 0,512 kW Leistungszahl: $${\epsilon }_{\mathit{HD}}={\mathit{EER}}_{\mathit{HD}}=\frac{{\dot{Q}}_{Z2}}{P_{\mathit{HD}}}=\mathrm{1,74}$$

An exemplary design for the refrigeration circuits 14, 15 is given below, to which, however, the invention is not intended to be restricted. Here, the indices refer to the states (I) to (VIII) of the refrigerants in the refrigeration circuits 14, 15, such as those in FIG Fig. 3 and 4th be used.
a) Secondary cooling circuit 15 Temperatures: T _I = -20 ° C T _II = 0 ° C T _III = -10 ° C T _IV = -30 ° C Pressures: p _I = 1 bar P _II = 2.5 bar Enthalpies: $$H_{\mathrm{I.}}=350\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{II}}=390\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{IIs}}=375\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{III}}=188\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{IV}}=188\frac{\mathit{kJ}}{\mathit{kg}}$$

Enthalpy differences: $$\mathrm{\Delta }{H}_{\mathit{II}-\mathrm{I.}}=40\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{H}_{\mathit{IIs}-\mathrm{I.}}=\mathrm{25th}\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{H}_{\mathit{III}-\mathit{II}}=-202\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{H}_{\mathrm{I.}-\mathit{IV}}=162\frac{\mathit{kJ}}{\mathit{kg}}$$

Mass flow: $${\dot{m}}_{\mathit{ND}}=0.0044\frac{\mathit{kg}}{s}$$

Cooling capacity: Q̇ _o = ṁ _ND · Δ h _I-IV = 0.7128 kW Capacitor power ND: Q̇ _Z1 = ṁ _ND · Δ h _III-II = -0.899 kW Compressor capacity: P _ND = ṁ _ND · Δ h _II-I = 0.176 kW Performance figure: $${\epsilon }_{\mathit{ND}}={\mathit{EER}}_{\mathit{ND}}=\frac{{\dot{Q}}_O}{P_{\mathit{ND}}}=4.05$$

b) Primary cooling circuit 14 Temperatures: T _V = -5 ° C T _VI = 55 ° C T _VII = 40 ° C T _VIII = -15 ° C Pressures: p _III = 2.3 bar P _IV = 10 bar Enthalpies: $$H_V=358\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{VI}}=422\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{VIs}}=407\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{VII}}=248\frac{\mathit{kJ}}{\mathit{kg}}$$

$$H_{\mathit{VIII}}=248\frac{\mathit{kJ}}{\mathit{kg}}$$

Enthalpy differences: $$\mathrm{\Delta }{H}_{\mathit{VI}-V}=64\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{H}_{\mathit{VIs}-V}=49\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{H}_{\mathit{VII}-\mathit{VI}}=-174\frac{\mathit{kJ}}{\mathit{kg}}$$

$$\mathrm{\Delta }{H}_{V-\mathit{VIII}}=110\frac{\mathit{kJ}}{\mathit{kg}}$$

Mass flow: $${\dot{m}}_{\mathit{HD}}=0.008\frac{\mathit{kg}}{s}$$

Evaporator capacity HD: Q _{Z 2} = ṁ _HD · Δ h _V-VIII = 0.889 kW Capacitor power: Q̇ _U = ṁ _HD · Δ h _VII-VI = -1.382 kW Compressor capacity: P _HD = ṁ _HD · Δ h _VI-V = 0.512 kW Performance figure: $${\epsilon }_{\mathit{HD}}={\mathit{EER}}_{\mathit{HD}}=\frac{{\dot{Q}}_{Z2}}{P_{\mathit{HD}}}=1.74$$

Here HD denotes the high-pressure circuit 24, while ND denotes the low-pressure circuit 25.

The above designs are based on the use of the refrigerant R1234yf in both refrigeration circuits 14, 15. Another design is also possible in which the temperatures, pressures, enthalpies, compressor output and / or mass flow rate by ± 20%, ± 10%, Can deviate by ± 5% from the specified values.

The arrangement of the evaporator 8 and its integration in the area of the centrifuge chamber 12 can be arbitrary within the scope of the invention. Thus, an evaporator 8 (and a heat exchanger formed with it) can extend inside a security element 26 or security vessel 27, in a wall of the security element 26 or security vessel 27 itself, or outside of the security element 26 or security vessel 27. For example, a line forming the evaporator 8 can extend in the circumferential direction of a safety boiler 27 or be integrated in this way into the safety boiler 27 itself. In particular for centrifuges 1 with low speeds, the primary refrigeration circuit 14 and the secondary refrigeration circuit 15 can both be arranged inside or outside a safety boiler 27. Particularly for centrifuges 1 with higher speeds, it is possible, in addition to a safety vessel 27, to use a safety wall which can at least partially separate the subspaces 30, 31 from one another. In this case, the secondary cooling circuit 15 can be arranged in an intermediate space between the safety boiler 27 and the safety wall, while the primary cooling circuit 14 is then arranged on the side of the safety wall facing away from the safety boiler 27. It is also possible that the safety boiler 27 is double-walled and the secondary cooling circuit 15 extends at least partially and in the area of the evaporator 8 in an intermediate space between the double walls of the safety boiler 27.

In the present description, the primary refrigeration circuit 14 and the secondary refrigeration circuit 15 are sometimes referred to in abbreviated form in the form of “the refrigeration circuits 14, 15”.

REFERENCE LIST

1

centrifuge

2

Refrigeration system

3

Refrigeration cycle

4th

engine

5

compressor

6th

Condenser, condenser

7th

Expansion element or throttle

8th

Evaporator

9

management

10

High pressure circuit part

11

Low pressure circuit part

12

Centrifuge chamber

13

Heat exchanger

14th

Primary refrigeration circuit

15th

Secondary refrigeration circuit

16

Heat exchanger

17th

compressor

18th

engine

19th

Condenser

20th

Heat exchanger

21st

Expansion element or throttle

22nd

Evaporator

23

management

24

High pressure circuit

25th

Low pressure circuit

26th

Security element

27

Safety boiler

28

casing

29

cover

30th

Subspace

31

Subspace

32

Space

33

corner

34

Space

35

corner

36

Space

37

Sidewall

38

Control logic

39

Control unit

40

Control line

41

Control line

42

time

43

Operating condition

44

Temperature sensor

45

ON operating state

46

OFF operating status

47

Operating curve (secondary refrigeration circuit)

48

Operating curve (primary cooling circuit)

49

Time offset

I.

State of the (second) refrigerant between evaporator 8 and compressor 5

II

State of the (second) refrigerant between compressor 5 and condenser 6

III

State of the (second) refrigerant between condenser 6 and expansion element 7

IV

State of the (second) refrigerant between expansion element 7 and evaporator 8

V

State of the (first) refrigerant between evaporator 22 and compressor 17

VI

State of the (first) refrigerant between compressor 17 and condenser 19

VII

State of the (first) refrigerant between condenser 19 and expansion element 21

VIII

State of the (first) refrigerant between expansion element 21 and evaporator 22

Claims (12)

1. Centrifuge (1) comprising

   a) a housing (28),

   b) a centrifugation chamber (12) wherein a rotor which is supported for being rotated is arranged or can be arranged,

   c) a primary cooling circuit (14)

   characterised by

   d) a secondary cooling circuit (15) which is thermically coupled to the primary cooling circuit (14) and to the centrifugation chamber (12),

   e) a control unit (39) being provided comprising control logic (38) which controls the primary cooling circuit (14) and the secondary cooling circuit (15) in a way such that

   ea) during an operation of the centrifuge (1) wherein the rotor is rotated cooling energy is generated by the primary cooling circuit (14) and/or

   eb) the primary cooling circuit (14) and the secondary cooling circuit (15) are operated simultaneously.
2. Centrifuge (1) of claim 1, characterised in that the primary cooling circuit (14) and/or the secondary cooling circuit (15) comprise/comprises a compressor (5; 17), a condenser (6; 19), an expanding device (7; 21) and an evaporator (8; 22).
3. Centrifuge (1) of one of the preceding claims, characterised in that the primary cooling circuit (14) is a high pressure circuit (24) and the secondary cooling circuit (15) is a low pressure circuit (25).
4. Centrifuge (1) of one of the preceding claims, characterised in that the primary cooling circuit (14) comprises a flammable refrigerant.
5. Centrifuge (1) of one of the preceding claims, characterised in that the secondary cooling circuit (15) comprises a non-flammable or low or difficult flammable refrigerant.
6. Centrifuge (1) of one of the preceding claims, characterised in that

   a) the primary cooling circuit (14) comprises a flammable refrigerant and the secondary cooling circuit (15) comprises a non-flammable or low or difficult flammable refrigerant or

   b) the primary cooling circuit (14) comprises a non-flammable or low or difficult flammable refrigerant and the second cooling circuit (15) comprises a non-flammable or low or difficult flammable refrigerant.
7. Centrifuge (1) of one of the preceding claims, characterised in that at least one heat exchanger (16; 20) is embodied as a microchannel heat exchanger.
8. Centrifuge (1) of one of the preceding claims, characterised in that

   a) the primary cooling circuit (14),

   b) a heat exchanger (16) which thermically couples the primary cooling circuit (14) to the secondary cooling circuit (15) and

   c) at least a part of the secondary cooling circuit (15)

   are arranged on a side of a securing element (26) facing towards the centrifugation chamber (12).
9. Centrifuge (1) of one of the preceding claims, characterised in that

   a) a housing (28) of the centrifuge (1) comprises an approximately rectangular horizontal section,

   b) the securing element (26) is a securing container or vessel (27)having a circular horizontal section,

   c) the compressor (17) of the primary cooling circuit (14) is arranged in an interspace (32) between an edge (33) of the housing (28) and the securing container or vessel (27),

   d) a compressor (5) of the secondary cooling circuit (15) is arranged in an intermediate space (34) between an edge (35) of the housing (28) and the securing container or vessel (27),

   e) the or a heat exchanger (16) which thermically couples the primary cooling circuit (14) and the secondary cooling circuit (15) to each other is arranged in an interspace (36) between a side wall (37) of the housing (28) and the securing container or vessel (27).
10. Centrifuge (1) of one of the preceding claims, characterised in that the control logic (38) of the control unit (39) is embodied such that it is possible to control a compressor (17) of the primary cooling circuit (14) and/or a compressor (5) of the secondary cooling circuit (15) into ON operating states (45) and OFF operating states (46).
11. Centrifuge (1) of claim 10, characterised in that the control logic (38) of the control unit (39) is designed such that the compressor (17) of the primary cooling circuit (14) and the compressor (5) of the secondary cooling circuit (17) are controlled into the ON operating state (45) with an offset in time (49).
12. Centrifuge (1) of claim 10 or 11, characterised in that the control logic (38) of the control unit (39) is embodied such that

    a) the primary cooling circuit (14) is permanently operated in an ON operating state (45) independent on the required cooling power for cooling the centrifugation chamber (12) and

    b) the secondary cooling circuit (15) is switched forth and back between an ON operating state (45) and an OFF operating state (46) dependent on a required cooling power for cooling the centrifugation chamber (12).

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