EP3479903A1 - Centrifuge - Google Patents

Abstract

The invention relates to a centrifuge (1), in particular a laboratory centrifuge. In the centrifuge (1) find a primary refrigeration circuit (14) and a secondary refrigeration circuit (15) use, which are thermally coupled to each other via a heat exchanger (16). The centrifuge (1) has a control unit (39) with control logic (38). The control unit (39) controls the primary refrigeration circuit (14) and the secondary refrigeration circuit (15) so that they are operated simultaneously and thus the centrifuge chamber (12) supplied cold in the primary refrigeration circuit (14) and in the Secondary refrigeration circuit (15) is generated. The embodiment of the invention expands in particular the possibilities of in the centrifuge (1) usable refrigerant.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a centrifuge, in particular a laboratory centrifuge. Centrifuges of the present type are used, for example, in biotechnology, the pharmaceutical industry, medical technology and environmental analysis. By means of such a centrifuge is carried out a centrifugation of a product, in particular a container or vessel with sample or substance arranged therein, or a plurality of such products at speeds which may be more than 3,000 U / min, for example. More than 15,000 U / min. As a result of the centrifugation, accelerations acting on the product are to be produced, which may be, for example, more than 15,000 × g (in particular more than 16,000 × g, more than 20,000 × g up to more than 60,000 × g). The 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, a targeted control of the pressure and / or temperature conditions can additionally take place during the centrifugation. To mention 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 centrifuging of microtitres, blood bags, petroleum vessels or blood vessels u. Ä.

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 rotational speeds of a rotor of the centrifuge, on which the products are held (possibly pivotable as a result of the centrifuging force), a relatively high heat input into a centrifuge chamber of the centrifuge takes place. In order to ensure defined temperatures of the product during centrifugation, therefore, a cooling of the centrifuge chamber is required, which usually takes place by means of a refrigeration cycle. In conventional such refrigerating circuits used in centrifuges, a compressor, a condenser, an expansion element and an evaporator are used, wherein the generation of the cold by evaporation and liquefaction of refrigerant in a closed refrigeration cycle takes place. The artificial temperature sink thus produced is then used to remove heat from the centrifuge chamber. Fig. 1 shows by way of example and schematically such a refrigeration cycle, which is shown as a left-handed cyclic process in a diagram in which the logarithm of the pressure p over the enthalpy h, in Fig. 2 is shown.

1. a) In the region of the state change (I) - (II), a compression of the refrigerant takes place. The compressor sucks in this case superheated steam, which in the diagram according to Fig. 2 It can be seen that the state point (I) is to the right of the dew line. The enthalpy difference h ₂ -h ₁ produced during the state changes (I) - (II) corresponds to the supplied technical work of the compressor, which is performed during the compression of the refrigerant by the compressor. Steam exits the compressor, which is more superheated than when entering the compressor. Further overheating is due to the polytropic compression taking place in the compressor and the heat input due to friction during compression as well as the heat input by the compressed superheated fluid.
2. b) In the region of state change (II) - (III), the refrigerant is undercooled by the condenser, which may also be referred to as a condenser. The pressure losses caused by the internal resistance are relatively low, so that the change of state simplified as isobar considered to be hardly. As a result of the approximately isobaric change, the largest loss entry occurs or there is a secondary entry of energy through free convection on the outer wall of the liquefier. Superheated steam passes into the condenser, which is subcooled by the isobaric heat dissipation to below the dew point, so that the refrigerant leaves the condenser in a liquid state.
3. c) During the state change (III) - (IV), the refrigerant is expanded to a lower pressure and temperature level in the expansion element, which is simply considered adiabatic. Here is an isenthalpe change of state. From the expansion element then exits the refrigerant in a state of wet steam, which in the diagram according to Fig. 2 It can be seen that the line for change of state (III) - (IV) in the area between the dew line and the boiling line of the refrigerant ends. The peculiarity of the change of state (III) - (IV) in the region of the expansion element in the real process is that here the refrigerant is not completely depressurized to the pressure level according to the initial state (I). This pressure difference is caused during the state change (IV) - (I) by the evaporator which causes a pressure difference by its internal flow resistance.
4. d) During the state change (IV) - (I) takes place in the evaporator, the actual use of the refrigeration cycle in the form of heat transfer from the refrigerant, in particular the centrifuge chamber and / or a safety boiler and any cooling fins in the refrigerant. The temperature sink created by the previous state changes and the input of work may release cold which is ultimately used to maintain the temperature of the product in the centrifuge chamber at least below a threshold temperature. In the evaporator via a suitable heat exchanger surface, a phase change of the refrigerant from a wet steam supplied to the inlet of the evaporator to a superheated steam leaving the evaporator, which is then sucked by the compressor.

The F-Gas Regulation (Regulation EU No. 517/2014 of the European Parliament and of the Council of 16.04.2014, which is valid from 01.01.2015), is aimed at emissions of fluorinated greenhouse gases (F-gases) by the year 2030 be reduced to 21% in several steps specified in the F-Gas Regulation. As a result, conventionally used refrigerants such as 1,1,1,2-tetrafluoroethane (R-134a) or R404a need to be replaced with alternative refrigerants, which is a challenge for centrifuges of the present type. The reason for this is that the centrifuges in operation generate very high kinetic energies, which are generated in close proximity to the refrigeration cycle and in the event of a crash of the centrifuge can destroy the inner workings of the centrifuge including the refrigeration cycle. This can escape the coolant in a crash and catch fire, which can also cause a fire in a crash spark. In order to avoid the occurrence of a fire in the event of a crash, special requirements with regard to the flammability of the refrigerant must be observed. On the other hand, a refrigerant which ensures the particular requirements with regard to combustibility must also be powerful enough to ensure the cooling required during operation of the centrifuge.

STATE OF THE ART

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

The publication EP 3 015 791 A1 Proposes to use in a centrifuge instead of a refrigerant R-134a based on CO ₂ (R744) refrigerant or at least one hydrocarbon refrigerant, which also mixtures are to be used. As a result, a higher efficiency of the refrigeration cycle is to be achieved, whereby the refrigeration cycle can have a smaller power consumption or can bring about a greater cooling effect with the same power consumption. Examples of possible refrigerants are 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 proposes to arrange an injection system in the evaporator of the refrigeration cycle, wherein the pressure in the compressor is to be limited by controlling the injection. Furthermore, it is proposed that the refrigeration cycle has at least one bypass for bridging an internal heat exchanger. In contrast to a refrigeration cycle in which a refrigerant R-134a is used, here in the refrigeration cycle between the low pressure side and the high pressure side, a larger pressure difference is required 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, an altered safety design of the centrifuge, which must be designed for a triple working pressure, and / or a restriction of the compressor pressure conditional. By means of a hot gas bypass must also be ensured that hot refrigerant is supplied to the evaporator, whereby an ice formation, for example. Must be avoided at the triple point of CO ₂ in the evaporator. In this case, a control of the hot gas bypass in dependence on the temperature in the suction line of the compressor is required, wherein suitably the hot gas bypass is used in a partial load operation. Alternatively, a control of the compressor can take place to avoid the formation of ice or a control of said injection system can take place. During operation of the centrifuge and the refrigeration cycle critical pressure increases are excluded in the refrigeration cycle due to the cooling capacity of the refrigeration cycle. However, a standstill of the centrifuge and of the refrigeration cycle can be problematic, since (for example as a consequence of an increased ambient temperature) an increase in pressure of the refrigerant in the non-operated refrigeration cycle can result. Remedy suggests EP 3 015 791 A1 a refrigeration cycle cascade with an additional, operated only at a standstill further refrigeration cycle. With the further refrigeration cycle, the non-operated, for example, CO ₂ -based compressor refrigeration cycle should be cooled at standstill in order to prevent a critical pressure increase in the CO ₂ -based compressor refrigeration cycle, while the further refrigeration cycle during operation of the centrifuge and the CO ₂ -based compressor refrigeration cycle is not operated.

The publication DE 10 2014 110 467 A1 Proposes that not only a refrigeration cycle be used in a centrifuge. Rather, the generation of the cold should be done by a primary refrigeration cycle, which is then thermally coupled via a heat exchanger with a secondary cooling circuit in which a refrigerant is circulated via a pump. The primary refrigeration circuit downstream secondary cooling circuit thus serves only to transport the cold, which has been generated by the primary refrigeration cycle, from the heat exchanger to the centrifuge chamber. In the primary refrigeration cycle then a conventional combustible refrigerant can be used, which may have low costs, but may have a high specific enthalpy of vaporization. By contrast, a non-combustible heat transfer medium (such as, for example, a cooling water with additives (for example, salt or alcohol) which reduce the freezing point) can be used for the secondary cooling circuit. If the primary refrigeration cycle and the secondary refrigeration cycle are then separated from one another via a safety wall, the combustible primary refrigeration cycle can be protected by the safety wall in the event of a crash, while the crash can possibly have effects on the non-combustible secondary refrigeration cycle. The primary refrigeration cycle may extend below the secondary refrigeration cycle or a safety boiler or laterally offset thereto in the housing of the centrifuge. A safety boiler can be fastened to the housing of the centrifuge via a clamping connection such that in the event of a crash a relative movement of the safety boiler relative to the housing of the centrifuge is possible. It is also proposed that lines of the primary refrigeration cycle are made of a mechanically stronger material than lines of the secondary cooling circuit, whereby it is also possible that lines of the secondary cooling circuit are specifically equipped with predetermined breaking points. In the case of a crash of the centrifuge, in which no complete absorption of the kinetic energy can take place through the safety boiler, due to the weaker formation of the lines of the secondary cooling circuit, the mechanical connection between the secondary cooling circuit and the primary refrigeration circuit can be separated, which is to be prevented in that the energy due to the crash via the lines of the secondary cooling circuit to the primary refrigeration cycle is transmitted, which there could be damage, leakage of the refrigerant of the primary refrigeration circuit and thus a fire.

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

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 has for its object to propose a centrifuge, which in particular with regard to

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

is improved.

SOLUTION

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

DESCRIPTION OF THE INVENTION

For the sake of simplicity of the description, in the present description there is spoken of "cold generation" as well as "cold transfer", although only a temperature sink can be generated when the physical view is correct, to which heat transfer then occurs.

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

According to the invention, the centrifuge has both a primary refrigeration cycle and a secondary refrigeration cycle. The secondary refrigeration cycle is thermally coupled (in particular via a heat exchanger) to the primary refrigeration cycle, so that cold generated in the primary refrigeration cycle can be transferred to the secondary refrigeration cycle. Furthermore, the secondary refrigeration cycle is thermally coupled to the centrifuge chamber, so that both the generated in the primary refrigeration cycle and transferred through the heat exchanger cold and the cold generated in the secondary refrigeration cycle can be transferred cumulatively 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 cycle and the secondary refrigeration cycle. In this case, the control takes place such that during operation of the centrifuge with a rotation of the rotor, a generation of cold by means of the primary refrigeration cycle takes place and / or a simultaneous operation of the primary refrigeration cycle and the secondary refrigeration cycle takes place.

During the prior art according to the document EP 3 015 791 A1 proposes only the use of a refrigeration cycle cascade with two refrigeration circuits to operate this at best alternately, the invention proposes for the first time to operate simultaneously the primary refrigeration cycle and the secondary refrigeration cycle, so that both mentioned refrigeration circuits used to produce the used for cooling the centrifuge chamber Cold can provide a contribution. Here, the two refrigeration circuits can be adjusted individually (for example, with regard to the state changes, the pressure changes and the enthalpy difference and / or to the respectively used in the refrigeration circuits refrigerant), resulting in an increased efficiency and / or an improved ratio in terms of construction volume and Cost over the producible cooling capacity can result. Furthermore, the inventive design allows any choice of refrigerant in the two refrigeration circuits, with which the Design scope in terms of efficiency, environmental compatibility, the security against the development of a fire and / or increase the cost. Under certain circumstances, the inventive design also allows new control options for the control of the temperature in the centrifuge chamber depending on the design 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 refrigeration is produced by using electrical power. It is possible here that in a refrigeration cycle, a compression of the refrigerant and / or a change in an aggregate state of the refrigerant is generated, the refrigeration circuit uses a magnetocaloric effect, the refrigeration cycle has an electric Peltier cooling, the refrigeration circuit generates cold using a vortex tube or in the refrigeration cycle is a generation of cold using an absorption refrigeration cycle or a compression refrigeration cycle. By contrast, a refrigeration cycle does not include a "cooling circuit" in which only a refrigerant is conveyed by means of a pump and by means of a transport of cold from a transfer point (such as a heat exchanger, in which a transmission of cold, which was generated externally from the cooling circuit is done, to the refrigerant of the refrigeration cycle) takes place to the centrifuge chamber.

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

While in principle for the design of the refrigeration cycle, the aforementioned or other embodiments of the refrigeration circuits can be used in the invention, the primary refrigeration cycle and / or the secondary refrigeration cycle for a proposal of the invention comprises a compressor, a condenser, an expansion device and an evaporator on. This choice of embodiment of the refrigeration cycle has been found to be advantageous in terms of space, cost, energy efficiency and usable refrigerant.

In the context of the invention, the primary refrigeration cycle may be formed as a high pressure circuit, while the secondary refrigeration cycle may be formed as a low pressure circuit. This allows the different design of different refrigerant circuits with a potential for optimizing the generation of the required cold.

While it is generally desirable that no flammable refrigerant be used in a centrifuge to prevent a fire, for a further proposal of the invention in the centrifuge (by the inventive design, and possibly without a significantly increased risk of fire) a combustible refrigerant (in particular, a flame retardant refrigerant, a flammable refrigerant, or a highly flammable refrigerant) may be used, especially when used (only) for the primary refrigeration cycle. This proposal is based on the finding that the lines and components of the primary refrigeration cycle u. U. also outside a safety boiler of the centrifuge can be arranged so that even in the case of a centrifuge crash the combustible refrigerant in the primary refrigeration circuit can not escape from the lines and / or can not be ignited.

For these or other embodiments, the invention further proposes that in the secondary refrigeration cycle, a non-flammable or flame-retardant refrigerant is used. This embodiment takes into account the fact that u. U. the refrigerant of the secondary refrigeration circuit is also located in the same area of the safety boiler of the centrifuge or even inside, so that this is basically exposed in a centrifuge crash the risk of the formation of a fire. The use of the non-flammable or flame-retardant refrigerant, however, can at least reduce the inherent risk of the occurrence of a fire.

For a particular embodiment, the invention proposes that the primary refrigeration cycle comprises a combustible refrigerant (especially a low flammable refrigerant, a flammable refrigerant or a highly flammable refrigerant), while the secondary refrigeration cycle has a nonflammable or low flammable refrigerant. It is also possible that the primary refrigeration cycle, a non-flammable or flame retardant refrigerant and the secondary refrigeration cycle has a non-flammable or flame retardant refrigerant. In these cases, the two refrigeration circuits may have the same or different refrigerants.

• Ein "nicht entflammbares Kältemittel" ist ein Kältemittel, welches gemäß SN DIN EN 378-1 keine Flammenausbreitung aufweist und der Gruppe A1 (geringe Toxizität) oder B1 (höhere Toxizität) zugeordnet ist. Die erfordert, dass bei einer Prüfung in Luft mit 60 °C und bei einem Druck von 1,013 bar keine Flammenausbreitung dieses Kältemittels erfolgt, wenn es sich um Ein-Stoff-Kältemittel handelt. Findet ein Gemisch-Kältemittel Einsatz, ist dies ebenfalls diesen Gruppen zugeordnet, wenn die durch eine Analyse der Fraktionierung bestimmte WCFF (ungünstige Verteilung der Bestandteile des Gemisches, welche die höchste Brennbarkeit ergibt) des Gemisches bei einer Prüfung mit 60 °C und 1,013 bar keine Flammenausbreitung bewirkt.

In this case, the refrigerants are classified with regard to combustibility 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 at 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 propagation and is assigned to group A1 (low toxicity) or B1 (higher toxicity). This requires that, when tested in air at 60 ° C and at a pressure of 1.013 bar, there will be no flame propagation of this refrigerant if it is a one-component refrigerant. If a mixture refrigerant is used, this is also assigned to these groups if the WCFF determined by an analysis of the fractionation (unfavorable distribution of the constituents of the mixture, which gives the highest combustibility) of the mixture in a test at 60 ° C and 1.013 bar no Flame spread causes.

" Flammable 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, cause flame propagation, 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 velocity that is ≤ 10 cm / s when tested at 23 ° C and a pressure of 1.013 bar. Preferably used as flame retardant refrigerant of this category A2L refrigerant R1234yf use.

"Flammable refrigerants" are assigned to the groups A2 (low toxicity) or B2 (higher toxicity) of the standard SN DIN EN 378-1 and meet for a one-substance refrigerant and for a mixture refrigerant employment the conditions that it with a Test at 60 ° C and a pressure of 1.013 bar to a flame propagation comes, the lower explosion limit (LFL)> 3.5 vol .-% and the heat of combustion is <19,000 kJ / kg.

Finally, "highly flammable refrigerants" are considered to be refrigerants which are classified according to the standard SN DIN EN 378-1 in the groups A3 (low toxicity) and B3 (higher toxicity). Here, one-substance-refrigerant and mixture-refrigerant use are assigned to these groups, if it comes with a test with 60 ° C and a pressure of 1.013 bar to a flame propagation and the lower explosion limit (LFL) ≤ 3.5 vol .-% or the heat of combustion is ≥ 19,000 kJ / kg.

Furthermore, in the present patent application, one-substance or mixture refrigerants are regarded as "combustible 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 one-component or mixture refrigerants associated with groups A1 or B1 and which are not flammable are referred to as "non-flammable refrigerants" .

In the refrigeration circuits, a heat exchanger in the region of the condenser of the primary refrigeration cycle and / or in the region of the transfer between the two refrigeration circuits, ie the evaporator of the primary refrigeration circuit and the condenser of the secondary refrigeration cycle, can be arranged. This heat exchangers of any type can be used in the invention. For example, (not limited to this embodiment) a plate heat exchanger or a shell and tube heat exchanger may 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 region of the condenser of the primary refrigeration cycle. This is to be understood as meaning 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 extent of the channels or a diameter thereof of, for example, less than 2 mm or 1 mm of the Refrigerant is flowed through, whereby a high efficiency, a small filling volume of the refrigerant, a low weight and a compact design can be achieved. The refrigerant is thus not routed here in pipes. It is possible that in the microchannel heat exchanger, the channels are formed by bores of the body or block or the body or block of several, for example, welded together or soldered parts is formed, which may have grooves and limit the channels when connected to each other. To the use of the heat exchanger in the region of the condenser of the primary refrigeration circuit, ambient air can then be conducted past the body or block directly and / or to cooling fins attached thereto by means of a blower. With regard to a possible embodiment of such a microchannel heat exchanger, reference is made to heat exchangers of this type, as are sold, for example, by the company Danfoss or on the Internet site
www.kka-online.info/artikel/kka_New Trends_bei_Komplettverflessigungssaetzen_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 a proposal of the invention, the primary refrigeration cycle, a heat exchanger, which couples the primary refrigeration cycle with the secondary refrigeration cycle, and at least a portion of the secondary refrigeration cycle on a side facing away from the centrifuge chamber of a security element, in particular a safety boiler, arranged. 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 security element, which means for the formation of the security element as a safety boiler, that the rotor is located inside the safety boiler, while the primary refrigeration circuit outside the safety boiler is. In this case, the emergence of a fire can be reliably prevented even when using a flame-retardant refrigerant or a combustible refrigerant in the primary refrigeration cycle, which is also in the centrifuge, the use of a low-cost refrigerant allows at least for the primary refrigeration cycle.

There are many possibilities for distributing the components of the refrigeration circuits and the lines in the housing of the centrifuge. By way of non-limiting example, the centrifuge housing may have an approximately rectangular horizontal section. In this case, the security element is a safety vessel with a circular horizontal section. Between a corner of the housing and the safety vessel with a circular horizontal section results in a gap in which in the context of the invention, a compressor of the primary refrigeration cycle can be arranged particularly advantageous. A corresponding other space results between another corner of the housing and the safety boiler. In this other space then the compressor of the secondary refrigeration cycle can be arranged. The heat exchanger, which thermally couples the primary refrigeration cycle and the secondary refrigeration cycle together, may in this case be arranged in a space which results between a side wall of the housing and the safety vessel, which is preferably a 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, this allows the line connections (in particular from and to the Heat exchanger) are kept relatively short in the two refrigeration circuits. On the other hand, the heat exchanger (protected by the safety boiler) can be arranged in a particularly space-saving manner in this way.

For the control or regulation (in the following also briefly only "control") of the compressors of the refrigeration circuits there are different possibilities. For example, variable speed compressors can be used. However, these require a converter, other components and / or increased sensor complexity and regulatory effort, which can increase the cost. According to one proposal of the invention, the control logic of the control unit is designed such that a compressor of the primary refrigeration cycle and / or a compressor of the secondary refrigeration cycle is / are activated in ON operating states and OFF operating states. Thus, non-speed-controlled compressor can be used, which thus have only an active and a non-active operating state. In this case, the control of the compression power and hence the generated cold can be controlled over the duration of the ON operating conditions and the ratio of the duration of the ON operating conditions to the duration of the intermediate OFF operating conditions.

It is quite possible that the two compressors of the refrigeration circuits are simultaneously controlled in the ON operating state. If, however, an undesirable increased peak current due to the simultaneous switching of the compressor can be avoided, are controlled for a proposal by the inventor of the compressor of the primary refrigeration cycle and the compressor of the secondary refrigeration circuit with a time delay in the ON operating state. On the other hand, the change to the OFF operating state can take place simultaneously or likewise with a time offset.

For a further proposal of the invention, the control logic of the control unit of the centrifuge is designed such that the primary refrigeration circuit regardless of a required cooling 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. Thus, the temperature fluctuations that occur in the evaporator of the primary refrigeration circuit are not as great as would be the case for an alternating changeover between an ON operating state and an OFF operating state in the primary refrigeration cycle. In this case, only the secondary refrigeration cycle is switched between an ON operation state and an OFF operation state depending on a required refrigerating capacity for cooling the centrifuge chamber. Background of this Embodiment is that the possible dissipated amount of heat of the primary refrigeration cycle is dependent on the condensation temperature, which is increased according to the invention, whereby a reduction of the power can be done. Possibly, by means of such a different activation of the two refrigeration circuits, a more accurate regulation of the temperature in the centrifuge chamber can take place.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages having to be achieved by embodiments according to the invention. Without thereby altering the subject matter of the appended claims, as regards the disclosure 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 and their relative arrangement and operative connection. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims. Likewise, in the claims listed features for further embodiments of the invention can be omitted.

The features mentioned in the patent claims and the description are to be understood in terms of their number that exactly this number or a greater number than the said number is present, without requiring an explicit use of the adverb "at least". For example, when talking about an element, it should be understood that there is exactly one element, two elements or more elements. These features may be supplemented by other features or be the only characteristics that make up the product in question.

The reference numerals contained in the claims do not limit the scope of the objects protected by the claims. They are for the sole 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 Horizontalschnitt.

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 temperaturabhängiger alternierender Ansteuerung des Sekundär-Kältekreislaufs in ON-Betriebszustände und OFF-Betriebszustände.

In the following the invention will be further explained and described with reference to preferred embodiments shown in the figures.

Fig. 1

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

Fig. 2

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

Fig. 3

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

Fig. 4

shows the two left-handed cycles of the primary refrigeration cycle and the secondary refrigeration cycle with the states (I) to (VIII) in representing the logarithm of the pressure p over the enthalpy h for a refrigeration system according to 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 sectioned spatial view obliquely from above and left front.

Fig. 7

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

Fig. 8

shows the centrifuge according to the Fig. 5 to 7 in a partially cut horizontal view diagonally 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 a temperature control with time-shifted control of the compressor in an ON operating state.

Fig. 11

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

DESCRIPTION OF THE FIGURES

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 cycle 3. In the refrigeration cycle 3, a compressor 5 driven by an electric power motor 4, a condenser or condenser 6, an expansion element 7 (specifically, an expansion valve or a throttle), and an evaporator 8 are connected in this order via lines 9a, 9b , 9c, 9d connected in a closed circuit.

In Fig. 1 the circled numerals indicate the states (I), (II), (III) and (IV) of the coolant used in the refrigeration cycle 3. Between the compressor 5 and the expansion element 7, the condenser 6 forms a high pressure circuit part 10 with the lines 9a, 9b, 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 refrigeration cycle 3 is transferred to the centrifuge chamber 12, which is shown here only schematically. An energetic exchange of the refrigeration cycle 3 takes place via the provision of refrigeration for the centrifuge chamber 12 through the evaporator 8 on the one hand by the application of electrical power to the motor 4 and the compression of the refrigerant in the region of the compressor 5. On the other hand takes place in the region of the condenser 6 a Heat exchange with the ambient air, in which case a fan with electric power can be driven. The condenser 6 thus forms a heat exchanger 13.

Fig. 2 shows the left-handed cyclic process, such as this with the steps a) to d) and the state changes (I) - (II), (II) - (III), (III) - (IV) and (IV) - (I) in of the introduction to 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 comprises a primary refrigeration cycle 14 and a secondary refrigeration cycle 15. The primary refrigeration cycle 14 is coupled via a heat exchanger 16 to the secondary refrigeration cycle 15. Here, the secondary refrigeration cycle 15 basically corresponds to the refrigeration cycle 3 according to Fig. 1 which also has corresponding states (I), (II), (III) and (IV). In the secondary refrigeration cycle 15, components included in the refrigeration cycle 3 are identified with the same reference numerals and will be referred to hereinafter by the same designations. With otherwise appropriate design communicates in the secondary refrigeration circuit 15, the evaporator 6 differing from Fig. 1 not with the ambient air. Rather, the evaporator 6 is part of the heat exchanger 16.

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

An energetic exchange of the primary refrigeration cycle 14 takes place via the provision of cold for the heat exchanger 16 through the evaporator 22 on the one hand by the application of electric motor 18 and the compression of the refrigerant in the region of the compressor 17. On the other hand, takes place in the region of the condenser 19 a heat exchange with the ambient air, in which case a fan with electric power can be driven. An energetic exchange of the secondary refrigeration cycle 15 via the provision of cold through the heat exchanger 16 to the condenser on the one hand by the application of the motor 4 with electrical power and the compression of the Refrigerant in the region of the compressor 5. On the other hand, takes place in the region of the evaporator 8, a cooling of the centrifuge chamber 12th

The refrigeration circuits 14, 15 can be operated simultaneously. Based on the introduction of electrical energy through the motor 18 and the compressor 17 driven therefrom, refrigeration is generated in the primary refrigeration cycle 14, which is transmitted via the heat exchanger 16 to the secondary refrigeration circuit 15 by the evaporator 22 gives off cold to the condenser 6 and by the transferred cold is used in the condenser 6 for liquefying the refrigerant of the secondary refrigeration circuit 15. In the secondary refrigeration cycle 15 supplementary refrigeration is generated with the introduction of electrical energy via the motor 4 and the compressor 5 driven therefrom. The refrigeration generated in this way by the primary refrigeration circuit 14 and the secondary refrigeration circuit 15 is then cumulated by the evaporator 8 of the secondary refrigeration cycle 15 is transmitted to the centrifuge chamber 12. It is possible that the mass flows, the refrigerant and / or the pressures in the two refrigeration circuits 14, 15 are different.

Fig. 4 shows the two left-handed cycles of the two refrigeration circuits 14, 15 in a diagram in which the logarithm of the pressure p over the enthalpy h is shown. The coupling of the two refrigeration circuits 14, 15 via the heat exchanger 16, which takes place here, is based on the principle that the coolant can be cooled down more deeply in the secondary refrigeration circuit 15 as a result of the supply of cold via the heat exchanger 16 from the primary refrigeration circuit 14 than the latter Case is when the refrigerant cooling the centrifuge chamber 12 is thermally coupled via a condenser 6 in the form of a heat exchanger 13 with the environment. The secondary refrigeration cycle 15 absorbs heat from the centrifuge chamber 12 and outputs it in the heat exchanger 16 via the condenser 6 of the secondary refrigeration cycle 15 to the primary refrigeration cycle 14, here the evaporator 22 of the heat exchanger 16, from.

In Fig. 4 Corresponding to the respective cycles (I) - (II), (II) - (111), (III) - (IV), (IV) - (I) for the secondary refrigeration cycle 15 and (V) - (VI), (VI) - (VII), (VII) - (VIII), (VIII) - (V) for the primary refrigeration cycle 14 in principle the in Fig. 2 illustrated and described in the introduction to the cycle, but these cycles then take place at different pressures, temperatures and specific enthalpies.

The heat transfer between the refrigeration circuits 14, 15 takes place in the region of the heat exchanger 16, which in the cycle according to Fig. 4 in the state changes (II) - (III) of the secondary refrigeration cycle 15 and (VIII) - (V) of the primary refrigeration cycle 14 is shown. The evaporation temperature of the primary refrigeration cycle 14 must be slightly lower than the condensation temperature of the secondary refrigeration cycle 15 in order to allow the necessary 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 cycle 14 must be selected. Due to the strong reduction of the final temperature of the liquefaction in the region of the condenser 6 of the secondary refrigeration cycle 15, the required enthalpy difference for the evaporation of the refrigerant is increased. 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 lowered. The lower injection temperature creates a greater temperature gradient between the refrigerant and the centrifuge chamber 12, thus improving the dissipation of heat.

With the diagram according to Fig. 4 should only the quality of the operation of the refrigeration system 2 formed with the primary refrigeration cycle 14 and the secondary refrigeration cycle 15 are shown. In Fig. 4 the cycle processes are exemplified for a refrigerant in the refrigeration circuits 14, 15, which is in each case designed as a refrigerant R1234yf. In this diagram, h = 200 kJ / kg and s = 1 kJ / (kg K) at 0 ° C on the boiling line were chosen as the reference state.

It is possible that by using the two series-connected refrigeration circuits 14, 15, the injection temperatures in the evaporator 8 of the secondary refrigeration cycle 15 are lowered to a minimum. Due to the reduced inlet temperature of the refrigerant in the region of the condenser 6, the internal specific energy of the refrigerant to be absorbed increases, which is necessary in order to evaporate it completely. Thus, the amount of heat that can be transferred from the centrifuge chamber 12 to the refrigerant increases. 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 has a higher injection temperature at the same pressure positions. The refrigeration system 2 according to the invention can u. U. operated at much higher ambient temperatures than one Refrigeration system 2 according to Fig. 1 with only one refrigeration cycle 3. This occurs while a loss of power. However, this power loss 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 interconnected refrigeration circuits 14, 15, it is possible u. U. also use a combustible refrigerant in the primary refrigeration cycle 14, since the primary refrigeration cycle 14 spatially via a security element 26, in particular a safety boiler 27, can be separated from the centrifuge chamber 12.

Fig. 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 generally rectangular in horizontal section and can be closed by means of a cover 29. In the housing 28, the security element 26 in the form of the safety boiler 27, in which the rotor rotates, is arranged in a subspace 30, which is accessible via the cover 29. By contrast, in an adjacent subspace 31, which is not accessible via the cover 29, so that here the housing 28 is closed, essential components of the refrigeration system 2, in particular the compressor 5, 17, the heat exchanger 16 and the condenser 19 or heat exchanger 20th and associated lines 9, 23 arranged. In the subspace 31 and the closed housing part connected thereto also electronic control devices, a control panel and displays of the centrifuge 1 are arranged. In Fig. 5 are the subspaces 30, 31, which are not separated by a wall here, separated by the dashed fictitious curved separation plane shown.

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

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

• In Fig. 9 ist über der Zeit 42 der Betriebszustand 43 der Verdichter 5, 17 bzw. der Motoren 4, 18 dargestellt, welcher sich infolge der Ansteuerung derselben durch die Steuereinheit 39 ergibt. Hier erfolgt keine Drehzahlregelung der Verdichter 5, 17, sondern diese werden vielmehr je nach Kühlbedarf, der auf Grundlage eines Temperatursensors 44 in der Zentrifugenkammer 12, dessen Messsignal ebenfalls der Steuereinheit 39 zugeführt wird, ermittelt wird, in einen ON-Betriebszustand 45 und einen OFF-Betriebszustand 46 geschaltet, was durch Aktivierung oder Deaktivierung der Motoren 4, 18 erfolgt. Fig. 9 zeigt die Ansteuerung für die Gewährleistung einer Dauerkühlung mit einer maximalen Kälteleistung. In Fig. 9 ist mit durchgezogener Betriebskurve 47 das ausgesteuerte Betriebsverhalten des Sekundär-Kältekreislaufs 15, also des Verdichters 5, dargestellt, während gestrichelt die Betriebskurve 48 für das Betriebsverhalten des Primär-Kältekreislaufs 14 und damit des Verdichters 17 dargestellt ist. Für die Dauerkühlung werden die Betriebszustände dauerhaft in den ON-Betriebszustand 45 geschaltet. Während die Umschaltung durchaus auch gleichzeitig erfolgen kann, zeigt Fig.9, dass die Umschaltung in den ON-Betriebszustand 45 für die Betriebskurven 47, 48 mit einem Zeitversatz 49 erfolgt, womit eine Reduzierung der Spitzenströme durch eine zeitliche Trennung der beiden Überhöhungen infolge der Umschaltung der Motoren 4, 18 in den ON-Betriebszustand 45 herbeigeführt werden kann. Für das dargestellte Ausführungsbeispiel erfolgt die Aktivierung des Sekundär-Kältekreislaufs 15 vor der Aktivierung des Primär-Kreislaufs 14, während auch ein umgekehrter Zeitversatz 49 möglich ist.

Schematically is in Fig. 3 outlines that a control of the two refrigeration circuits 14, 15 via a control logic 38 having electronic control unit 39 is carried out. The control unit 39 controls via control lines 40, 41, the power of the compressor 5, 17, which is done by direct control of the electrical impingement of the motors 4, 18 or by transmitting a control signal to the motors 4, 18, in which then, u. U. by means of a control subunit, the appropriate electrical loading 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 is over the time 42 of the operating state 43 of the compressor 5, 17 and the motors 4, 18 shown, which results from the control thereof by the control unit 39. Here, no speed control of the compressor 5, 17, but these are rather depending on the cooling demand, which is based on a temperature sensor 44 in the centrifuge chamber 12, the measurement signal is also supplied to the control unit 39 is determined, in an ON-operating state 45 and an OFF Operating state 46 connected, which is done by activating or deactivating the motors 4, 18. Fig. 9 shows the control for ensuring continuous cooling with a maximum cooling capacity. In Fig. 9 is the continuous operation curve of the secondary refrigeration cycle 15, ie the compressor 5, shown with a solid curve 47, while the operating curve 48 for the performance of the primary refrigeration cycle 14 and thus of the compressor 17 is shown in dashed lines. For continuous cooling, the operating states are permanently switched to the ON operating state 45. While switching can be done at the same time, shows Figure 9 in that the switching to the ON operating state 45 for the operating curves 47, 48 takes place with a time offset 49, whereby a reduction of the peak currents is brought about by a temporal separation of the two overshoots as a result of the switching of the motors 4, 18 into the ON operating state 45 can. For the illustrated embodiment, the activation of the secondary refrigeration cycle 15 takes place before the activation of the primary circuit 14, while also a reversed time offset 49 is possible.

Fig. 10 shows the corresponding conditions for a control (which also includes a regulation) of a predetermined temperature in the centrifuge chamber 12, which is not the Provision of the maximum cooling capacity required. For this purpose, there is an alternating toggling of the operating states of the refrigeration circuits 14, 15 between the ON operating state 45 and the OFF operating state 46, wherein the frequency of the reciprocation and / or the ratio of the periods for the ON operating state 45 and the OFF operating state 46 correlated with the provided cooling capacity, so that by means of the control unit, depending on the required cooling capacity, a suitable control can be effected by influencing the frequency of the to-and-fro and the ratios of the durations. For this switching back and forth, a time offset 49 can be used for switching from the OFF operating state 46 in the ON operating state 45, wherein preferably then the downshift from the ON operating state 45 to the OFF operating state 46 takes place without time offset 49 , Here, for the provision of a constant cooling capacity, the switching of the two refrigeration circuits 14, 15 with the same frequency, but for the illustrated embodiment in view of the time offset 49 of the ON operating state 45 for the secondary refrigeration circuit 15 is longer than for the primary refrigeration cycle fourteenth (without this being absolutely necessary).

Fig. 11 shows a modified temperature control in which the primary refrigeration cycle 14 is permanently switched to the ON operating state 45, so that this provides a permanent heat sink. Here, the control of the centrifuge chamber 12 supplied cold is controlled only via the decrease in the cold of the primary refrigeration cycle 14 through the secondary refrigeration circuit 15 by switching on and off the secondary refrigeration circuit 15 between the ON operating state 45 and as needed OFF operating state 46 takes place, in which case for controlling or regulating the temperature in the centrifuge chamber 12 and thus the centrifugal chamber 12 supplied cold influence is taken on the ratio of the periods of the ON operating states and the OFF operating states.

In the following, an exemplary design for the refrigeration circuits 14, 15 is given, but which is not intended to limit the invention. Here, the indices refer to the states (I) to (VIII) of the refrigerants in the refrigeration circuits 14, 15, as in the Fig. 3 and 4 be used.

a) secondary refrigeration circuit 15th

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:

$H_I=350\frac{\mathit{kJ}}{\mathit{kg}}$

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

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

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

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

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

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

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

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

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

Cooling capacity: Q̇ _o = ṁ _ND · Δh _I-IV = 0.7128 kW Capacitor power ND: Q̇ _{Z 1} = ṁ _ND · Δ h _III-II = -0.899 kW Compressor power: P _ND = ṁND × Δh _II-I = 0.176 kW COP: ${\epsilon }_{\mathit{ND}}={\mathit{EER}}_{\mathit{ND}}=\frac{{\dot{Q}}_O}{P_{\mathit{ND}}}=4.05$

b) primary refrigeration 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: ${\mathrm{\Delta }\mathit{H}}_{\mathit{VI}-V}=64\frac{\mathit{kJ}}{\mathit{kg}}$

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

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

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

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

Evaporator power HD: Q̇ _{Z 2} = ṁHD · Δh _V-VIII = 0.889 kW Condenser performance: Q̇ _U = ṁ _HD · Δh _VII-VI = -1,382 kW Compressor power: P = m _{'HD HD} Δ · h _VI-V = 0.512 kW COP: ${\epsilon }_{\mathit{HD}}={\mathit{EER}}_{\mathit{HD}}=\frac{{\dot{Q}}_{Z_2}}{P_{\mathit{HD}}}=1.74$

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. It is also possible to have a different design in which the temperatures, the pressures, the enthalpies, the compressor power and / or the mass flow by ± 20%, ± 10%, ± 5% may deviate from the stated values.

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

In the present description, reference is made in part to the primary refrigeration cycle 14 and the secondary refrigeration cycle 15 in the form of "the refrigeration cycles 14, 15".

LIST OF REFERENCE NUMBERS

1

centrifuge

2

refrigeration plant

3

Refrigeration circuit

4

engine

5

compressor

6

Condenser, condenser

7

Expansion element or throttle

8th

Evaporator

9

management

10

High-pressure circuit portion

11

Low pressure circulation part

12

centrifuge chamber

13

heat exchangers

14

Primary refrigerant circuit

15

Secondary refrigerant circuit

16

heat exchangers

17

compressor

18

engine

19

condenser

20

heat exchangers

21

Expansion element or throttle

22

Evaporator

23

management

24

High pressure circuit

25

Low-pressure circuit

26

security element

27

safety tank

28

casing

29

cover

30

subspace

31

subspace

32

gap

33

corner

34

gap

35

corner

36

gap

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 mode

47

Operating curve (secondary refrigeration circuit)

48

Operating curve (primary refrigeration cycle)

49

time offset

I

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

II

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

III

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

IV

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

V

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

VI

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

VII

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

VIII

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

Claims (12)

Centrifuge (1) with a) a housing (28), b) a centrifuge chamber (12) in which a rotatably mounted rotor is or can be arranged, c) a primary refrigeration cycle (14) and d) a secondary refrigeration circuit (15) thermally coupled to the primary refrigeration cycle (14) and to the centrifuge chamber (12), e) wherein a control unit (39) with control logic (38) is present, which controls the primary refrigeration cycle (14) and the secondary refrigeration cycle (15) so that ea) during operation of the centrifuge (1) with a rotation of the rotor, a generation of cold by means of the primary refrigeration cycle (14) takes place and / or eb) a simultaneous operation of the primary refrigeration cycle (14) and the secondary refrigeration cycle (15) takes place. Centrifuge (1) according to claim 1, characterized in that the primary refrigeration circuit (14) and / or the secondary refrigeration circuit (15) comprises a compressor (5; 17), a condenser (6; 19), an expansion device (7; 21) and an evaporator (8; 22) have /. Centrifuge (1) according to one of the preceding claims, characterized in that the primary refrigeration circuit (14) is a high pressure circuit (24) and the secondary refrigeration circuit (15) is a low pressure circuit (25). Centrifuge (1) according to one of the preceding claims, characterized in that the primary refrigeration cycle (14) comprises a combustible refrigerant. Centrifuge (1) according to one of the preceding claims, characterized in that the secondary refrigeration circuit (15) comprises a non-flammable or flame-retardant refrigerant. Centrifuge (1) according to one of the preceding claims, characterized in that a) the primary refrigeration cycle (14) comprises a combustible refrigerant and the secondary refrigeration cycle (15) comprises a non-flammable or flame-retardant refrigerant or b) the primary refrigeration cycle (14) comprises a nonflammable or flame retardant refrigerant and the secondary refrigeration cycle (15) comprises a nonflammable or flame retardant refrigerant. Centrifuge (1) according to one of the preceding claims, characterized in that at least one heat exchanger (16; 20) is designed as a microchannel heat exchanger. Centrifuge (1) according to one of the preceding claims, characterized in that a) the primary refrigeration cycle (14), b) a heat exchanger (16) which thermally couples the primary refrigeration cycle (14) with the secondary refrigeration cycle (15), and c) at least part of the secondary refrigeration cycle (15) on one of the centrifuge chamber (12) facing away from a security element (26) are arranged. Centrifuge (1) according to one of the preceding claims, characterized in that a) a housing (28) of the centrifuge (1) has an approximately rectangular horizontal section, b) the security element (26) is a safety vessel (27) with a circular horizontal section, c) a compressor (17) of the primary refrigeration circuit (14) is arranged in a space (32) between a corner (33) of the housing (28) and the safety boiler (27), d) a compressor (5) of the secondary refrigeration circuit (15) is arranged in a gap (34) between a corner (35) of the housing (28) and the safety vessel (27), e) the or a heat exchanger (16) which thermally couples the primary refrigeration circuit (14) and the secondary refrigeration circuit (15) in an intermediate space (36) between a side wall (37) of the housing (28) and the safety boiler (27) is arranged. Centrifuge (1) according to one of the preceding claims, characterized in that the control logic (38) of the control unit (39) is designed such that a compressor (17) of the primary refrigeration cycle (14) and / or a compressor (5) of the Secondary refrigeration cycle (15) in ON operating states (45) and OFF operating states (46) is / are controlled. Centrifuge (1) according to claim 10, characterized in that the control logic (38) of the control unit (39) is designed such that the compressor (17) of the primary refrigeration cycle (14) and the compressor (5) of the secondary refrigeration cycle ( 17) are offset with a time offset (49) in the ON operating state (45) are controlled. Centrifuge (1) according to claim 10 or 11, characterized in that the control logic (38) of the control unit (39) is designed such that a) the primary refrigeration cycle (14) is operated independently of a required cooling capacity for cooling the centrifuge chamber (12) permanently in an ON operating state (45) and b) the secondary refrigeration cycle (15) is switched back and forth depending on a required cooling capacity for cooling the centrifuge chamber (12) between an ON operating state (45) and an OFF operating state (46).

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