Abstract
The present invention relates to a centrifuge, in particular a laboratory centrifuge, comprising a rotor which is rotatably mounted in an interior of a rotor chamber and is designed to accommodate sample vessels, a drive motor to set the rotor in rotation, and a cooling device which is designed to dissipate heat from the interior of the rotor chamber via a coolant, the cooling device being designed to use an elastocaloric effect and having at least one cooling unit which comprises an elastocaloric material arranged between a counter block and a punch, the punch being designed to periodically apply a force to the elastocaloric material and then to let the elastocaloric material relax again, the cooling device being designed to transfer both heat from the elastocaloric material to the coolant and from the coolant to the elastocaloric material. The present invention also relates to a method for cooling an interior of a rotor chamber of such a centrifuge.
Claims
1. A centrifuge, comprising: a rotor rotatably mounted in an interior of a rotor chamber and being designed to accommodate sample vessels, a drive motor to set the rotor in rotation, and a cooling device designed to dissipate heat from the interior of the rotor chamber via a coolant, wherein the cooling device is designed to use an elastocaloric effect and has at least one cooling unit which comprises an elastocaloric material arranged between a counter block and a punch, the punch being designed to periodically apply a force to the elastocaloric material and then to let the elastocaloric material relax again, the cooling device being designed to transfer both heat from the elastocaloric material to the coolant and from the coolant to the elastocaloric material, wherein the cooling device comprises a cooling group which has a plurality of cooling units connected in series, the cooling units being arranged and designed such that a rotating eccentric successively applies a force to the punches of the cooling units, and wherein the eccentric has an eccentrically rotating shaft which is surrounded by a sleeve that is rotatable relative to the shaft.
2. The centrifuge according to claim 1, wherein the cooling device has two coolant circuits, and wherein the cooling unit is connectable to one of the two coolant circuits via valves.
3. The centrifuge according to claim 2, wherein at least one pump is provided which conveys the coolant in both coolant circuits.
4. The centrifuge according to claim 2, wherein each of the two coolant circuits comprises a heat pipe and the coolant is transported in the coolant circuits exclusively passively.
5. The centrifuge according to claim 1, wherein the cooling device comprises at least one of the following features: the cooling device has a plurality of cooling units connected in series, the counter block and the punch are designed to periodically apply pressure to the elastocaloric material, the elastocaloric material is designed to be rod-shaped, the cooling device comprises a plurality of elements with elastocaloric material, the cooling device is designed to use latent heat of the coolant, the cooling device is designed to transport heat from the rotor chamber of the centrifuge to a cooler equipped with a fan, which is designed to dissipate at least part of the heat into ambient air, the coolant is in direct contact with at least one of the counter block and the elastocaloric material, the coolant comprises at least one of water and ethanol, the cooling device comprises a drive motor which is designed to periodically apply the force to the punch, the drive motor is a motor from a group consisting of electromagnetic linear drive, spindle-mechanical linear drive, hydraulic unit, piezo actuator, pneumatic unit, lifting magnets, and the elastocaloric material comprises at least one material from a group consisting of nickel-titanium alloy (NiTi), nickel-titanium-copper alloy (NiTiCu), nickel-iron-gallium alloy (Ni.sub.2FeGa), copper-zinc-aluminum alloy (CuZnAl), nickel-titanium-hafnium alloy (NiTiHf), copper-aluminum-nickel alloy (CuAlNi), copper-aluminum-beryllium alloy (CuAlBe), titanium-nickel-iron alloy (TiNiFe), titanium-nickel-copper-cobalt alloy (TiNiCuCo).
6. (canceled)
7. The centrifuge according to claim 1, wherein the cooling device has only one coolant circuit and transport of the coolant in this coolant circuit takes place exclusively passively.
8. The centrifuge according to claim 1, wherein the drive motor drives both the rotor and the eccentric.
9. (canceled)
10. A method for cooling an interior of a rotor chamber of a centrifuge, comprising the steps of: transferring heat from the interior of the rotor chamber to a coolant, transferring heat from an elastocaloric material to the coolant, cooling the coolant in a cooler, transferring heat from the coolant to the elastocaloric material, and feeding the coolant to the rotor chamber of the centrifuge.
11. The centrifuge according to claim 1, wherein the centrifuge comprises a laboratory centrifuge.
12. The centrifuge according to claim 3, wherein a single pump is provided for both coolant circuits.
13. (canceled)
14. The centrifuge according to claim 1, wherein the sleeve is mounted via a ball bearing on the shaft.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present invention is described in more detail below with reference to the embodiments shown in the figures. The embodiments serve only to describe preferred embodiments of the present invention, without this being restricted to the examples. Identical or identically acting components are numbered with the same reference signs. Repeated components are not identified separately in each figure. Schematically, in the drawings:
[0028] FIG. 1 is a perspective view of a centrifuge;
[0029] FIG. 2 shows the centrifuge according to FIG. 1 without a cover;
[0030] FIG. 3 shows the centrifuge according to FIGS. 1 and 2 without a housing;
[0031] FIG. 4 is a cross section through a cooling unit;
[0032] FIG. 5 shows a first embodiment of a cooling device;
[0033] FIG. 6 shows a second embodiment of a cooling device with a plurality of cooling units;
[0034] FIG. 7 shows a third embodiment of a cooling device with only one pump;
[0035] FIG. 8 shows a fourth embodiment of a cooling device with heat pipes;
[0036] FIG. 8a shows a first embodiment of the connection of the heat pipes according to FIG. 8 with the cooling unit;
[0037] FIG. 8b shows a second embodiment of the connection of the heat pipes according to FIG. 8 with the cooling unit;
[0038] FIG. 8c shows a third embodiment of the connection of the heat pipes according to FIG. 8 with the cooling unit;
[0039] FIG. 9 is a cross section through a further embodiment of a cooling unit;
[0040] FIG. 10 is a cross section through a cooling group with cooling units according to FIG. 9;
[0041] FIG. 11 shows a fifth embodiment of a cooling device with a cooling group according to FIG. 10;
[0042] FIG. 12 shows a drive for the cooling unit with an eccentric shaft and a piston;
[0043] FIG. 13 shows a drive for the cooling unit with an eccentric;
[0044] FIG. 14 shows a drive for the cooling unit with an eccentric shaft and a sleeve; and
[0045] FIG. 15 is a flowchart of the method.
DETAILED DESCRIPTION OF THE INVENTION
[0046] FIGS. 1 to 3 show a centrifuge according to the present invention, here a laboratory centrifuge 1, the basic structure of which is similar to a conventional centrifuge; in this case, a floor-standing centrifuge. The laboratory centrifuge 1 comprises a housing 10 and a cover 11. The housing 10 has ventilation openings 13 through which warm air can be dissipated from the housing 10 of the laboratory centrifuge 1 into the outside environment. In addition, the laboratory centrifuge 1 has an operating unit 12 by means of which an operator can set various parameters on the centrifuge, for example the speed of rotation and the desired temperature at which the samples are to be kept. In FIG. 2, the cover 11 and in FIG. 3 the entire housing 10 has been removed, so that the support frame 15 of the laboratory centrifuge 1 is visible in FIG. 3. As can be seen from these figures, the laboratory centrifuge 1 has a rotor chamber 14, in the interior 141 of which a rotor 16 is rotatably mounted. The rotor 16 is designed to accommodate sample vessels, for example as a fixed-angle rotor or as a swing-bucket rotor. So that the samples in the rotor 16 continue to remain cooled to a predetermined temperature during centrifugation, the rotor chamber 14 must be cooled during operation of the centrifuge. For this purpose, the laboratory centrifuge 1 has a cooling device 18, which will be described in more detail below. The laboratory centrifuge 1 likewise has a drive motor 17 to drive the rotor 16 and, in particular, also the cooling device 18.
[0047] FIG. 4 shows a cross section through an elastocaloric cooling unit 2. The cooling unit 2 comprises a counter block 20 which serves as an abutment for the elastocaloric material 22 and as a housing for the cooling unit 2. In one embodiment of the present invention, the elastocaloric material 22 is designed as a multiplicity of rods which are arranged between the counter block 20 and a punch 21. The punch 21 is slidably mounted on the side walls of the counter block 20 so that it transfers a force F, which force is symbolized by the black arrow, in a one-to-one manner to the elastocaloric material 22. In addition, the cooling unit 2 has a feed line 23 through which coolant can enter the cavity formed by the counter block 20 in which the elastocaloric material 22 is located. If a force F is applied to the elastocaloric material 22, it is heated, as a result of which heat is transferred to the coolant. In turn, the elastocaloric material 22 cools while it relaxes. In this case, the coolant is also cooled. The heated or cooled coolant can leave the cooling unit 2 via the discharge line 24 which, like the feed line 23, forms a channel through the counter block 20.
[0048] FIG. 5 shows a first embodiment of a cooling device 18 using the cooling unit 2. The cooling device 18 is designed to transport heat from the rotor chamber 14 of the laboratory centrifuge 1 to a cooler 180. The cooler 180 is designed, for example, as an air-liquid heat exchanger and transfers at least part of the heat of the coolant to the ambient air with the aid of the fan 181. The cooling device 18 comprises a first coolant circuit A, which is designed to transport heat from the rotor chamber 14 to the cooling unit 2. The first coolant circuit A comprises a coolant line 182 which, for example, winds around the rotor chamber 14 and thus absorbs heat from it. In addition, the cooling device 18 comprises a second coolant circuit B, which is designed to transport heat from the cooling unit 2 to the cooler 180 and which likewise has a coolant line 182 for this purpose. The same coolant is used in both coolant circuits A, B. The coolant in the coolant lines 182 is conveyed via a pump 183 in each case, which pump is located in the corresponding coolant circuit A, B. Finally, the cooling device 18 also comprises two valves, specifically a first valve 184 and a second valve 185, which are each designed as 2-way valves. The cooling unit 2 can be connected to either the first coolant circuit A or the second coolant circuit B via the inlet and outlet lines 23, 24 via the two valves 184, 185. For this purpose, the valves 184, 185 are adjusted simultaneously between their switching positions shown.
[0049] In the position shown in FIG. 5, the cooling unit 2 is connected to the second coolant circuit B, for example. The cooling device 18 is operated, for example, in this switching position, while the force F is applied to the elastocaloric material 22 of the cooling unit 2. By means of the change in the heat capacity of the elastocaloric material 22, heat is released therefrom. The heat is absorbed by the coolant of the second coolant circuit B and transported to the cooler 180. The switching position of the two valves 184, 185 is then switched over so that the cooling unit 2 is located in the first coolant circuit A. The force F is taken from the punch 21 and thus from the elastocaloric material 22, whereby this material relaxes. In doing so, the material changes its heat capacity again, in particular in such a way that the elastocaloric material 22 cools down. In this way, the elastocaloric material 22 absorbs heat from the coolant of the first coolant circuit A and thereby cools it down. The cooled coolant in the first coolant circuit A is then transported to the rotor chamber 14 and cools said chamber.
[0050] FIG. 6 shows a further embodiment of a cooling device 18. In contrast to the cooling device 18 of FIG. 5, the one in FIG. 6 uses a plurality of cooling units 2. In particular, these are connected in series between the valves 184, 185. Although two cooling units 2 are shown in this embodiment of the present invention, more than two cooling units 2 can also be used. By using a plurality of cooling units 2, more elastocaloric material 22 is also used, as a result of which greater temperature swings can be achieved. At the same time, a punch 21 does not have to apply a force F at once to the sum of the elastocaloric material 22, which force would be sufficient to compress this entire elastocaloric material 22, for example. It is sufficient to apply a smaller force F to the punches 21 of the individual cooling units 2, which force is sufficient for the elastocaloric material 22 used in the individual cooling unit 2.
[0051] Another embodiment of a cooling device 18 is shown in FIG. 7. This differs from that of FIG. 5 in that only a single pump 183 is used to convey the coolant in the coolant lines 182 of both coolant circuits A, B. In particular, the single pump 183 of this embodiment is also located between the valves 184, 185. It is therefore connected in series with the at least one cooling unit 2 and, like this, can also be connected to one of the coolant circuits A, B via the valves 184, 185.
[0052] Another embodiment of the cooling device 18 is shown in FIG. 8. The embodiment of FIG. 8 differs from the previous ones in that the two coolant circuits A, B are no longer implemented via coolant lines 182, but rather via one heat pipe 186 for each coolant circuit A, B. Both the outward flow and the return flow of the coolant take place within the same heat pipe 186 in the process. The heat flow from the rotor chamber 14 to the cooler 180 is implemented via a single inflow and outflow valve 187, which is synchronized with the application of force or the relaxation of the elastocaloric material 22, analogously to the previous embodiments. The inflow and outflow valve 187 can, however, also be omitted or, in a purely functional manner, shows that the heat transfer via the cooling unit 2 is also synchronized in this embodiment over the operating phases of the cooling unit 2.
[0053] FIGS. 8a, 8b, and 8c represent different possibilities of thermally connecting the heat pipes 186 to the cooling unit 2 and the cooling units 2, respectively. FIG. 8a, for example, shows an embodiment in which the cooling unit 2 is installed directly with the heat pipes 186. Specifically, the cooling unit 2 is connected to the heat pipe 186 coming from the cooler 180 in such a way that the coolant of this heat pipe 186 is in direct contact with the elastocaloric material 22 inside the cooling unit 2. If the elastocaloric material 22 heats up, the coolant evaporates and is distributed in the entire interior of the heat pipe 186, as a result of which heat is quickly transported away from the cooling unit 2. During the relaxation of the elastocaloric material 22, the counter block 20, which is in thermal contact with the heat pipe 186 coming from the rotor chamber 14, is cooled. For example, the counter block 20 is arranged directly on the heat pipe 186, as shown in FIG. 8a. Alternatively, it would also be possible, for example, to integrate the cooling unit 2 into this heat pipe 186 in such a way that the counter block 20 is in direct contact with the coolant of the heat pipe 186. Overall, heat is therefore transferred from one heat pipe 186 to the other via the cooling unit 2.
[0054] The embodiment according to FIG. 8b shows the thermal connection of the two heat pipes 186 via the cooling unit 2 by means of separate circuits. In this case, therefore, additional coolant lines 182 with coolant are arranged, which are intended to transfer the heat from one heat pipe 186 to the other. The corresponding embodiment therefore substantially corresponds to the arrangements of the coolant circuits as shown in FIGS. 5, 6, and 7 and described in the corresponding passages of the description, whereby heat transfer only does not take place directly between the rotor chamber 14 and the cooler 180, but it rather takes place between the two heat pipes 186. Reference is therefore made to the corresponding embodiments in order to avoid repetition.
[0055] Another embodiment of the present invention is shown in FIG. 8c. This comprises a transport device 27 which is designed to adjust the cooling unit 2 between two positions, the cooling unit 2 being in contact with one of the two heat pipes 186 in each of the positions. The transport device 27 can include in this case, for example, a linear actuator, for example with a rail or the like. The adjustment of the cooling unit 2 between the two positions is synchronized with the operating phases of the cooling unit 2, so that the cooling unit 2 is in contact with the heat pipe 186 coming from the rotor chamber 14, while the elastocaloric material 22 relaxes and cools down in the process, and so that the cooling unit 2 is in contact with the heat pipe 186 coming from the cooler 180, while the force F is applied to the elastocaloric material 22 which is heated in the process. In this way, too, heat is transferred from one heat pipe 186 to the other via the cooling unit 2.
[0056] In addition, FIG. 8 shows, by way of example, a drive motor 189 which is designed to apply the force F to the punch 21 of the cooling unit 2 and thus to the elastocaloric material 22. The drive motor 189 (not shown for reasons of clarity) can also be provided in the embodiments shown above. In particular, the drive motor 189 drives all of the cooling units 2 of the cooling device 18. In principle, the drive motor 189 can be the drive motor 17 which drives the rotor 16 of the laboratory centrifuge 1. In the embodiment shown, however, it is a separate drive motor 189 which is designed exclusively to drive the cooling unit 2.
[0057] FIG. 9 shows a cooling unit 2 which is advantageously designed to utilize the latent heat of the coolant. For this purpose, the cooling unit 2, in contrast to the cooling unit 2 in FIG. 4, has an inlet valve 25 in its feed line 23 and an outlet valve 26 in its discharge line 24. The valves 25, 26 are, for example, overpressure valves which, however, can only open in one direction, specifically in the same direction, to the right in the embodiment shown in FIG. 9. The mode of operation of the cooling unit 2 according to FIG. 9 is as follows: By applying the force F to the elastocaloric material 22, heat is released. This is absorbed by the coolant, which is located in the direct vicinity of the elastocaloric material 22, whereby the coolant evaporates. This increases the pressure in the interior of the cooling unit 2, which in turn opens the outlet valve 26 and at least part of the evaporated coolant escapes to the right from the cooling unit 2, taking the absorbed heat with it in the process. This is followed by the phase of relaxation of the elastocaloric material 22, as a result of which it cools. As a result of the cooling, the pressure in the interior of the cooling unit 2 drops. The pressure drops until the inlet valve 25 opens and coolant flows into the cooling unit 2 from the left. Since the drop in pressure takes a specific amount of time, the elastocaloric material 22 also cools the counter block 20, which consists of a material with good thermal conductivity, for example metal. This process is repeated periodically so that the bottom line is that the heat released by the elastocaloric material 22 is transported away from the cooling unit 2 with the coolant in the direction of flow, i.e., to the right, while the counter block 20 continues to cool and further coolant flows into the cooling unit 2 from the left. The application of a force F to the elastocaloric material 22 via the punch 21 therefore leads, on the one hand, to a mass transport of the coolant through the cooling unit 2 and, on the other hand, to the heating of the coolant and a cooling of the counter block 20.
[0058] FIG. 10 shows a cooling group 3 in which these effects are used. Specifically, the cooling group 3 comprises a plurality of, in this case five, cooling units 2 according to FIG. 9. The cooling units 2 are connected to one another and connected in series via a coolant line 182. In addition, the cooling group 3 comprises an eccentric 30 which is designed to rotate about an axis of rotation R. As a result of the rotation of the eccentric 30, a force F is applied successively to the punches 21 of the cooling units 2 arranged in a circle around the eccentric 30. In this way, as described above for FIG. 9, the coolant located in the cooling units 2 is conveyed in the direction of rotation of the eccentric 30 through the coolant line 182 and the cooling units 2. In this case, the coolant is heated more and more while the counter blocks 20 of the cooling units 2 cool down. Overall, the cooling group 3 therefore implements both a conveyance of the coolant and a separation of the heat and cold made available by the elastocaloric material 22.
[0059] FIG. 11 shows an embodiment of a cooling device 18 using a cooling group 3 according to FIG. 10. The cooling device 18 takes advantage of the fact that the cooling group 3 provides a delivery rate for the coolant, which, however, is solely due to the heat transfer and is therefore exclusively passive. An active delivery of the coolant is not necessary, which is why this embodiment works completely without a pump. It comprises a single coolant circuit C, which is formed, for example, by coolant lines 182, but could just as well be formed by heat pipes 186. Specifically, the coolant absorbs heat in the rotor chamber 14 of the laboratory centrifuge 1, which operates at approximately 4° C. This heat is transported with the coolant via the coolant line 182 to the cooling group 3. As described above, the coolant is passed through the cooling group 3 and is heated up in the process while the counter blocks 20 of the cooling units 2 of the cooling group 3 cool down. The heated coolant is then transported via the coolant lines 182 to the cooler 180, which typically operates at room temperature, for example 21° C., and where the coolant is cooled with the aid of the fan 181. In the direction of flow behind the cooler 180, the coolant passes a valve 188, which separates the hot from the cold side and regulates the flow. The coolant cooled by the cooler 180 is then brought into contact with the counter blocks 20 of the cooling units 2 of the cooling group 3 directly. In particular, the sequence of the contact of the coolant on the backflow side to the rotor chamber 14 with the counter blocks 20 of the cooling units 2 corresponds to the opposite flow direction of the cooling units 2 through the coolant. The counter block 20 of the cooling unit 2 through which the coolant flows last within the cooling group 3 is therefore contacted first with the coolant, while the counter block 20 of the cooling unit 2 through which the coolant flows first within the cooling group 3 is contacted last with the coolant. The coolant transfers heat to the counter blocks 20 or is cooled by them until it is finally cold enough to absorb heat from the interior 141 of the rotor chamber 14 again. For the operation of this cooling device 18, it is only necessary to drive the eccentric 30 of the cooling group 3 and the fan 181. As is also shown in FIG. 11, the drive of the rotor 16 of the laboratory centrifuge 1 takes place within the rotor chamber 14 and the drive of the eccentric 30 of the cooling group 3 takes place by means of the same drive motor 17. This drive motor 17 can also be used to drive the fan 181.
[0060] FIGS. 12, 13, and 14 show various possibilities for driving the cooling unit 2, i.e., for applying a force F to the punch 21 and the elastocaloric material 22. FIG. 12 shows, for example, a shaft 31 driven eccentrically about the axis of rotation R, which is connected to a piston 32 to convert the rotational movement into a linear movement, for example in the manner of a crankshaft. The piston 32 in turn transmits the movement to the punch 21 of the cooling unit 2. FIG. 13 shows an eccentric 30 rotating about the axis of rotation R, for example a cam of a camshaft. During the rotation of the eccentric 30, its eccentric bulge strikes the punch 21 of the cooling unit 2 and thus applies the force F thereto. In this case, however, there are strong frictional forces between the eccentric 30 and the punch 21. In order to avoid disadvantages associated therewith, the eccentric 30 according to FIG. 14 is therefore proposed. This in turn has an eccentric shaft 31 which can be rotated about the axis of rotation R. A ball bearing 33 is arranged on the outer circumferential surface of the eccentric shaft 31, via which, in turn, a sleeve 34 is mounted on the eccentric shaft 31. In particular, the sleeve 34 completely encloses both the ball bearing 33 and the eccentric shaft 31. The eccentric 30 according to FIG. 14 therefore comes into contact with the sleeve 34 with the punches 21 of the cooling units 2. Since the sleeve 34 is rotatably mounted relative to the eccentric shaft 31 via the ball bearing 33, the sleeve 34 rolls on the eccentric shaft 31, thereby avoiding damage to the sleeve 34 or the eccentric 30 as a whole and to the punch 21. At the same time, less drive energy has to be used. The eccentric 30 according to FIG. 14 is therefore particularly suitable for use in the cooling group 3. The eccentric shafts 31 and the eccentric 30 can be driven by the drive motor 17, 189 used in each case.
[0061] FIG. 15 shows a flowchart of method 4. The method 4 begins with the transfer 40 of heat from the interior 141 of the rotor chamber 14 to a coolant. The coolant is then transported to the elastocaloric material 22 of the cooling unit 2. There follows the transfer 41 of heat from the elastocaloric material 22 to the coolant, which is thereby heated above the ambient temperature. In the next step, the coolant is cooled 42 in a cooler 180 which operates at ambient temperature. The coolant cooled in this way is then conducted back to the cooling unit 2, where heat is transferred 43 from the coolant to the elastocaloric material 22, as a result of which the coolant is cooled down to at least the operating temperature of the rotor chamber 14. Finally, the supply 44 of the coolant to the rotor chamber 14 of the laboratory centrifuge 1 then follows. There, the coolant can again absorb heat from the interior 141 of the rotor chamber 14, and the method 4 begins again. All in all, the use according to the present invention of the elastocaloric effect for cooling a centrifuge, in particular a laboratory centrifuge 1, prevents the use of environmentally harmful and flammable coolants typically used in compressor cooling. By using the embodiments described, it is also possible to achieve a high level of economy in terms of both manufacturing and operating costs.
