Patent Application
20170189916
The invention relates to a centrifuge.
Undesired heat is generated during the operation of a centrifuge, which heat has a damaging effect on the material to be centrifuged. What is especially problematic here is that, for safety reasons, the centrifuge rotor whose rotation and the resulting atmospheric friction produces most of the heat is usually arranged within a vessel firmly sealed by a lid, which makes it difficult for the heat to escape. Often, for biological samples, a temperature of 4° C. often is required and has to be maintained during centrifugation. Active cooling is therefore indispensable, especially for longer operating times and high speeds of rotation, and sample temperatures below ambient temperature.
Various approaches for cooling centrifuges are known in the prior art. Particularly frequent is the use of compressor-based cooling systems for this purpose. While this type of cooling has been tried and tested and proven reliable, it also has a number of disadvantages. First of all, the use of compressed media for heat extraction makes it necessary to use conducting means such as copper pipes which are capable of withstanding pressures of the order of approx. 25 bar. However, copper pipes are not only expensive, their rigidity limits their use to certain places of a centrifuge, and they provide a relatively small heat-transfer surface. Secondly, temperature is usually controlled using a two-point control, i.e. by switching the compressor on and off. The more precisely the temperature is to be set, the more frequently the compressor will have to be turned on and off. This results in additional vibration of the rotor and/or the centrifuge, in addition to the usual vibration in operation, which has a detrimental effect on the material to be centrifuged and the service life of the centrifuge. Frequently turning the centrifuge off and on also increases the power consumption of the device. Furthermore, the use of refrigerants may be problematic from various points of view, besides the above mentioned high pressures. On the one hand, the use of flammable refrigerants in centrifuges is prohibited for safety reasons. On the other hand, there are more and more legal restrictions concerning the environmental compatibility of the refrigerants. It may thus sometimes be a challenge to find reliable, admissible and low-cost refrigerants suitable for cooling centrifuges.
It is the object of the present invention to provide a centrifuge which does not have the above mentioned disadvantages and which can be cooled efficiently and in a low-cost manner, whose operation is low in vibration and thus gentle on the product, and which is unproblematic from a safety point of view.
The invention is based on the finding that conventional refrigeration systems for centrifuges, in particular compression refrigeration systems, can be replaced with magnetocaloric cooling and that in this way, a centrifuge can be created in a simple manner which is safer, more economical and gentler in operation than conventional centrifuges. Moreover, this results in a number of new design options for optimizing the centrifuge even further.
According to the invention, the centrifuge has a safety vessel with a vessel wall, a rotor which is arranged in the safety vessel and is connected via a drive shaft to a drive device, wherein at least the drive shaft extends through the safety vessel, and a cooling system for cooling the interior space of the safety vessel, which comprises a heat transfer medium for taking up heat from the safety vessel, a refrigerating unit and conducting means for the heat transfer medium. The refrigerating unit is based on the magnetocaloric effect. The interior space of the safety vessel is cooled by a first cooling circuit. The magnetocaloric effect of the refrigerating unit extracts heat from the heat transfer medium of the first cooling circuit and feeds the heat to a second cooling circuit. The refrigerating unit contains magnetocaloric material which will heat up when exposed to a magnetic field, and which will cool down again once said magnetic field is removed. Cyclically exposing this magnetocaloric material to a magnetic field and circulating a heat transfer medium of the second cooling circuit around said material will cause heat to be extracted from said material, and circulating a heat transfer medium of the first cooling circuit around said material to which heat is released will trigger a heat transfer process. In other words, the heat transfer medium of a first cooling circuit—the so-called cold circuit—and the heat transfer medium of a second cooling circuit—the so-called heat circuit—will alternately and repeatedly circulate round the magnetocaloric material, in a manner synchronized to the magnetic field. This has the advantage that the use of a compression refrigeration system and a refrigerant suitable for this purpose can be dispensed with. Eliminating the compressor will result in smoother operation of the centrifuge and thus gentler handling of the material to be centrifuged, as there will be no vibrations and no agitation caused thereby. Furthermore, power consumption will be lower since there will be no constant turning on and off of a compressor which requires a lot of power. Moreover, the thermodynamic efficiency of magnetic refrigeration systems is higher than that of conventional compression-based refrigeration systems. Further advantages of this magnetocaloric refrigeration which result in cost savings will be explained in more detail below.
Considered particularly advantageous is the use of cooling water as a heat transfer medium, which water additionally contains additives such as salt or alcohol which will reduce the freezing point. These solutions are inexpensive, environmentally friendly and non-flammable.
More specifically, the conducting means for the heat transfer medium are designed as low-pressure lines for an operating pressure of below 3 bar. This is a simple way of expanding the constructive design options for the conducting means. For example, by suitably designing the conducting means, a larger surface will be available for heat extraction. Moreover, flexible materials can now also be used which can be adapted better to the surfaces to be cooled, thus enabling more efficient cooling. Furthermore, the flexible materials are usually also lighter in weight and less expensive than the materials used for high-pressure lines, e.g. copper.
In one aspect of the present invention, a control or regulating unit is provided which can be used to control or regulate the refrigerating unit and thus to adjust the temperature of the safety vessel interior. This ensures that, depending on the individual application and operating status, a predetermined optimum temperature will be maintained within the centrifuge.
For conveying the heat transfer medium through the conducting means, pumps are provided in each circuit. Here it is advantageous for the pumps to be capable of also being controlled and/or regulated by the control or regulating unit. In this way, the temperature within the centrifuge can be additionally adjusted via the amount and the rate of the heat transfer medium conveyed through the conducting means.
In an advantageous further embodiment of the invention, the safety vessel has an interior which faces the rotor and an exterior which cooperates with the cooling system, and the conducting means of the first cooling circuit is at least in some parts formed by the safety vessel, so that the heat transfer medium has direct surface-area contact with the vessel wall exterior of the safety vessel and flows over it. This is advantageous in that direct contact of the heat transfer medium with the vessel wall makes for more efficient cooling than can be achieved by means of a heat transfer medium which flows through lines which are for example provided on the exterior of the safety vessel.
It is advantageous for the heat transfer medium to be guided through the conducting means in a concentric manner about a central axis of the safety vessel. This allows for uniform cooling of the vessel interior.
In one aspect of the present invention, in some parts of the conducting means, the heat transfer medium is guided in parallel and/or radially relative to the central axis of the safety vessel. Thus, the structural conditions of the centrifuge can be taken into account and it is possible to cool a larger surface of the vessel wall.
In yet another advantageous embodiment of the invention, the safety vessel is of a double-wall design having an interior wall and an exterior wall. The heat transfer medium flows between the interior and exterior walls, in which case it makes direct surface contact with the exterior of the safety vessel interior wall and flows over it. Consequently, this makes it possible to cool almost the entire surface of the safety vessel interior wall whilst the exterior wall may have insulation formed thereon, for example.
In accordance with one embodiment of the invention, it has proven advantageous for the interior wall to form an interior vessel and for the exterior wall to form an exterior vessel, with the interior and exterior vessels being arranged concentrically to one another, wherein the interior and exterior vessels are matched to each other proportionally in such a way that, in certain areas, the interior and exterior walls are uniformly spaced from each other. This facilitates production of the safety vessel and allows a more uniform flow of heat transfer medium between the interior and exterior walls.
To provide better control of the flow of the heat transfer medium and to effect even more uniform cooling, it is advantageous to provide flow directing means, in particular made of plastic or sheet metal, between the interior and exterior walls, which are part of the conducting means.
In an advantageous further development of the invention, conducting means are provided which are incorporated into the material of the safety vessel wall. This on the one hand determines the flow paths of the heat transfer medium, which further improves the cooling action. On the other hand, this makes the safety vessel design more robust which has a positive effect on the safety of the centrifuge.
In an alternative embodiment, mutually associated recesses are provided in the exterior of the interior wall and in the interior of the exterior wall, which recesses, taken together, form the conducting means, i.e. the safety vessel cooling duct. Hence it is no longer necessary to incorporate separate components for the lines into the safety vessel wall, which in turn makes production of the safety vessel easier and cheaper.
Moreover, it is considered advantageous to provide an inlet of the heat transfer medium into the safety vessel conducting means and an outlet of the heat transfer medium, and to arrange either the inlet in the area of the upper edge of the safety vessel and the outlet in the area of a vessel bottom of the safety vessel, or the other wand round. So, from a vertical perspective, after heat extraction, the heat transfer medium can be introduced on the one side of the safety vessel, and can be withdrawn on the other side of the safety vessel.
In yet another advantageous embodiment, following the inlet is an annular manifold which preferably extends in one plane. In particular in combination with the above described conducts which at least in parts extend in parallel to the central axis of the safety vessel, this will ensure fast and uniform distribution of the cooled heat transfer medium.
It has also proved useful to provide an annular collector duct, which preferably extends in one plane, upstream of the outlet. This design simplifies the removal of the heat transfer medium after it has passed through the wall.
With a view to simplifying production and reducing production costs, it is considered advantageous to use an aluminum part made in a pressure die-casting process for the vessel wall. Equally suited for this purpose is zinc.
In an alternative embodiment, U-shaped line profiles are fitted onto the exterior of the vessel wall, which constitute the conducting means of the safety vessel. In this case, the U shape is closed by the vessel wall so that—viewed in cross-section of the line profile—both legs extend towards the vessel wall. This may be advantageous for solutions which are aimed especially at saving space and weight since a single-wall safety vessel has smaller outer dimensions and is of lower weight. However, these solutions still benefit from the advantage that the heat transfer medium passes directly over the wall of the safety vessel.
In one aspect of the present invention, a centrifuge lid is provided which has conducting means incorporated into it or fitted onto it that are connected to the refrigerating unit. Consequently, the heat transfer medium can also be used for more efficient cooling of the centrifuge lid.
In another embodiment of the invention, the drive device is at least partially surrounded by conducting means for the heat transfer medium which are connected to the refrigerating unit. This thus also effects direct cooling of the drive device which is one cause for major heat input in the safety vessel.
In this case, it is advantageous to have the portion of the drive device which is surrounded by conducting means project into the safety vessel. For such an arrangement, cooling can easily be effected technically, for example by means of a hood including conducting means which is placed on the portion of the drive device which projects into the safety vessel and mounted thereon. In this case, cooling is effected both of the drive device and of the interior space of the safety vessel.
In yet another advantageous embodiment of the invention, heat transfer medium conducting means which are connected to the refrigerating unit are integrated in the drive device. This kind of cooling is efficient and in particular space saving.
In yet another embodiment of the invention, the safety vessel is a deep-drawn vessel made from steel plate, in particular stainless steel plate. This lowers production costs and makes for a longer service life of the safety vessel.
Additional advantages, features and possible applications of the present invention may be gathered from the description which follows, in which reference is made to the embodiments illustrated in the drawings.
Throughout the description, the claims and the drawings, those terms and associated reference signs are used as are indicated in the list of reference signs which follows below. In the drawings,
The view of
A safety vessel 30 of the centrifuge 10 is mounted on a base plate 26 together with the magnetocaloric refrigerating unit 12. The magnetocaloric refrigerating unit 12 essentially comprises a cooling aggregate 13 having a stator mounted therein which is not shown in the drawings, a heat exchanger 15, a pump device (14) (not shown) and a regulating unit 16. Heat transfer medium 19 flows through a system of conducting means 18 in a first cooling circuit 111 between the magnetocaloric refrigerating unit 12 and the safety vessel 30. The first cooling circuit 111 of the heat transfer medium 19 will be explained in more detail with reference to the embodiments shown in the figures which follow.
The safety vessel 30 has a vessel wall 32 with an interior space 31, an interior 34, an exterior 36 and a vessel bottom 38. Conducting means 18 for the heat transfer medium 19 are provided for cooling the interior space 31 of the safety vessel 30, which conducting means 18 are not shown in
Via conducting means 18, the heat transfer medium 19 previously cooled in the magnetocaloric refrigerating unit 12 in the manner described above flows to a feed line 54 provided in a first end portion below the seal 51 which feed line 54 feeds the medium 19 into the intermediate space 48. In the intermediate space 48, the heat transfer medium 19 circulates concentrically around the central axis Y of the safety vessel 30, thereby cooling especially the interior wall 40 through direct surface contact with the exterior 42 of the latter. Finally, the heat transfer medium 19 exits the intermediate space 48 via a discharge line 56 which then feeds it back to the magnetocaloric refrigerating unit 12. Insulation 58 is provided around the safety vessel and rests against the exterior of the exterior wall 44 and is only penetrated by the feed line 54, the discharge line 56 and the drive device 22 which latter extends into the safety vessel 30 through the vessel bottom 38.
For enhanced control of the flow of the heat transfer medium 19, it is also possible to provide flow directing elements in the intermediate space 48 between the interior wall 40 and the exterior wall 44.
Furthermore, it is also conceivable to position the interior wall 40 and the exterior wall 44 without any space between them, and to form the conducting means 18 in the safety vessel 30 by mutually associated recesses in the interior wall 40 and the exterior wall 44.
Instead of the cover hood 72, it is also conceivable to provide conducting means for the heat transfer medium 19 which are incorporated in the drive device 22 and connected to the refrigerating unit 70. Above the cover hood 76, a rotor 17 is connected to the drive device 22 via a drive shaft 20.
For closing the safety vessel 30, a centrifuge lid 72 is provided on the side opposite the vessel bottom 38. Mounted on the exterior 74 of this lid 72 which faces away from the interior of the safety vessel 30 are cooling ducts 80 which are connected to the magnetocaloric refrigerating unit 70 via feed and discharge lines not shown in this Figure. In this way, the safety vessel 30 is cooled both by the cover hood 72 in the area of the vessel bottom 38, and by the centrifuge lid 76 located above the rotor 17.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 107 294.4 | May 2014 | DE | national |
This patent application is the national phase entry of PCT/EP2015/055589. PCT/EP2015/055589, international application filing date Mar. 17, 2015, claims the benefit and priority of and to German patent application DE No. 10 2014 107 294.4, filed May 23, 2014. PCT/EP2015/055589, international application filing date Mar. 17, 2015 and German patent application no. DE 10 2014 107 294.4, filed May 23, 2014 are incorporated herein by reference hereto in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/055589 | 3/17/2015 | WO | 00 |
