Device for cooling a consumer with a super-cooled liquid in a cooling circuit

Abstract

A super-cooled liquid medium, preferably super-cooled liquid nitrogen, is pumped through a sub-cooler and cooled by the same medium that evaporates in the vacuum. This super-cooled nitrogen is used as coolant for a consumer. If a small amount of heat is emitted by the consumer to the nitrogen, the liquid medium can be guided in the circuit wherein the sub-cooler is arranged. For compensating volume fluctuations, such a circuit requires a compensation vessel, which is very expensive and can only be operated in the presence of a super-cooled medium when either a part of the medium is heated using external energy, or an inert gas which boils at very low temperatures is used as a pressure compensation medium. According to the disclosure, when a supply container for the liquid medium is integrated into the cooling circuit and used as a compensation vessel, a separate compensation vessel is not required.

Claims

1. A device for cooling a consumer, comprising: a cooling circuit for circulating a cooling fluid, in which there is provided a pump and a super-cooler, wherein the super-cooler has: a container which is fluidically connected, via a supply line equipped with an expansion valve, to a storage tank for the cooling liquid and which serves for accommodating a cooling bath; a gas removal line, arranged on the container, for discharging evaporated cooling liquid; and a heat exchanger which, during proper use of the device, is immersed in the cooling bath and is integrated into the cooling circuit, and characterized in that, the storage tank includes a volume of cooling fluid which is substantially greater than the volume of cooling fluid within the cooling circuit and, during use of the device, a flow open connection line having a first end and a second end, the first end fluidly connected to a branch point of the cooling circuit and the second end is fluidly connected to a branch point of the supply line, upstream of the expansion valve, and wherein when said cooling fluid within the cooling circuit becomes heated thereby building pressure, said fluid flows via the flow open connection line into the storage tank to relieve pressure within the cooling circuit thus maintaining a substantially constant pressure throughout the device.

2. The device as claimed in claim 1, wherein a second super-cooler is arranged in the supply line, between a mouth of the flow open connection line and the expansion valve.

3. The device as claimed in claim 1, wherein a phase separator is provided in the supply line, upstream of the expansion valve.

4. The device as claimed in claim 1, wherein the flow open connection line opens into the cooling circuit downstream of the consumer but upstream of the pump.

5. The device as claimed in claim 1, wherein the gas removal line is equipped with a vacuum pump.

6. The device as claimed in claim 1, wherein the storage tank is equipped with a pressurization vaporizer.

7. The device as claimed in claim 1, wherein a superconducting component is provided as the consumer.

Description

(1) Exemplary embodiments of the invention are illustrated in schematic views of the drawings, in which:

(2) FIG. 1 shows the circuit diagram of a device according to the invention in a first embodiment,

(3) FIG. 2 shows the circuit diagram of a device according to the invention in a second embodiment,

(4) FIG. 3 shows the circuit diagram of a device according to the invention in third first embodiment.

(5) In the following, parts of the embodiments shown that have the same effect have in each case the same reference number.

(6) The device 1 shown in FIG. 1 comprises a cooling circuit 2 for cooling a consumer (not shown here), for example a superconducting cable or magnet. The cooling circuit 2 comprises a forward-flow line 3 for supplying, to the consumer, a liquid coolant, in particular a cryogenic coolant such as for example liquid nitrogen, LNG or a liquefied noble gas, and a return-flow line 4 for removing liquid coolant from the consumer. The forward-flow line 3 and the return-flow line 4 are fluidically connected to one another, and a pump 5 conveys the liquid coolant within the cooling circuit 2.

(7) A super-cooler 6 is arranged in the forward-flow line, downstream of the pump 5. The super-cooler 6 comprises a pressure container 7 in which there is accommodated a cooling bath 8. The forward-flow line 3, fed through the pressure container 7, enters the cooling bath 8 with a heat exchanger, for example a cooling coil 9. In order to supply fresh liquid coolant to the cooling bath 8, a supply line 12, which is connected to the sump of a storage tank 11, for example a standing tank, opens into the pressure container 7. The pressure in the storage tank 11 is in that context held at a predefined value by means of a tank pressure control unit, for example using an air vaporizer 13. In the supply line 12, there is arranged an expansion valve 14 by means of which it is possible to set a maximum pressure in the supply line 12 downstream of the expansion valve 14. In an upper regionwhich during proper use of the device 1 is filled with gaseous coolantwithin the pressure container 7, there opens a gas removal line 15 into which a vacuum pump 16 is optionally integrated. The cooling circuit 2 and the fittings fluidically connected to the storage tank 11 are not fluidically independent of one another but rather are coupled to one another via a connection line 17 that, between a branching point 18 upstream of the expansion valve and a branching point 19 upstream of the pump 5, produces a flow connection between the supply line 12 and the cooling circuit 2.

(8) When the device 1 is in operation, the liquid coolant flows through the cooling circuit 2. The pressure in the cooling circuit 2 essentially corresponds to the pressure at the bottom of the storage tank 11 and therefore has a boiling temperature that is higher than the boiling temperature of the coolant at the liquid surface in the storage tank 11. The coolant is fed in the super-cooled state to a consumer via the forward-flow line 3, and the coolant heated by heat contact with the consumer, and/or with pipe sections leading to or from the consumer, flows, still in the liquid and preferably in the super-cooled state, away from the consumer via the return-flow line 4 and is fed back into the forward-flow line 3 by means of the pump 5.

(9) In order to ensure that the coolant is in the liquid state in the entire cooling circuit 2, the coolant in the forward-flow line 3 is cooled by the super-cooler 6 to a predefined temperature of for example 5 K to 10 K below its boiling temperature. The predefined temperature is chosen such that the total heat input in the cooling circuit 2 is insufficientor at most just sufficientto heat the super-cooled coolant to its boiling temperature. To that end, the coolant in the cooling bath 8 is brought to a lower pressure than the coolant in the cooling circuit 2, such that the boiling temperature at the pressure prevailing in the pressure container 7 is below the predefined temperature of the coolant in the forward-flow line 3. The required pressure is set at the expansion valve 14; if necessary, the pressure can also be reduced to a pressure of below 1 bar by using the vacuum pump 16. The gas removed via the gas removal line 15 is released to the atmosphere or is supplied to another use. It is also conceivable, within the scope of the invention, that the pressure in the pressure container 7 is controlled in dependence on a measured temperature of the coolant in the forward-flow line 3.

(10) An equalizing volume is necessary in the case of pressure fluctuations arising during operation of the cooling circuit 2. In the case of the device 1, the storage tank 11 serves as such an equalizing volume since coolant can flow freely, via the connection line 19 which is open to flow in both directions during operation of the device 1, between the cooling circuit 2 and the storage tank 11. The pressurization vaporizer 13 provides any pressure buildup which may be required in the storage tank 11. Therefore, the device 1 does not require a separate equalizing vessel assigned to the cooling circuit 2. Since the branching-off point 18 in the supply line 12 is arranged upstream of the expansion valve 14, and the expansion valve 14 controls to a predefined end pressure, pressure fluctuations arising in the cooling circuit 2 do not lead to a notable influence on the pressure ratios in the container 7.

(11) The device 20 shown in FIG. 2 differs from the device 1 only by an additional super-cooler 21 which is arranged in the supply line 12, upstream of the expansion valve 14. The super-cooler 21 has a heat exchanger 22 that is accommodated in a cooling bath 23. The cooling bath 23 is also supplied from the storage tank 11, with the difference however that an expansion valve 24 ensures that the pressure in the cooling bath 23 is lower than in the line 12, and thus the temperature of the cooling bath 23 is lower than the temperature of the coolant flowing through the heat exchanger 22. Super-cooling the coolant flowing through the supply line 12 prevents a substantial part of the coolant reaching the expansion valve 14 in the already vaporized state, which would harm the functionality of the expansion valve 14 and influence the performance of the super-cooler 6.

(12) In the device 25 shown in FIG. 3, there is located, in the supply line 12, upstream of the expansion valve 14, a phase separator 26 and, upstream of the latter, a further expansion valve 27. The phase separator comprises a vessel 28 in which gaseous coolant, produced upstream of the phase separator 26 by vaporization of liquid coolant and/or introduced from the cooling circuit 2 via the connection line 19, collects in a gas phase 29 in the phase separator 26 while the coolant which has remained in the liquid state forms a liquid phase 30 in the phase separator 26. The liquid phase 30 is fluidically connected to the super-cooler 6 via that section of the supply line 12 downstream of the phase separator 26, while gas can be removed from the gas phase 29 via a gas discharge 31 fluidically connected to the gas phase 29. The phase separator 26 ensures, in a similar manner to the second super-cooler 21 in device 20, that immediately upstream of the expansion valve 14 there is no or only a small quantity of gaseous coolant in the supply line 12, thus avoiding disruption to the function of the expansion valve 14; at the same time, it can be used to pre-cool the coolant fed to the super-cooler 6 in that, during operation, the gas phase 29 is held at a lower pressure than the pressure at the bottom of the storage tank 11.

LIST OF REFERENCE SIGNS

(13) 1. Device 2. Cooling circuit 3. Forward-flow line 4. Return-flow line 5. Pump 6. Super-cooler 7. Pressure container 8. Cooling bath 9. Cooling coil 10. - 11. Storage tank 12. Supply line 13. Air vaporizer 14. Expansion valve 15. Gas removal line 16. Vacuum pump 17. Connection line 18. Branching-off point 19. Branching-off point 20. Device 21. Super-cooler 22. Heat exchanger 23. Cooling bath 24. Expansion valve 25. Device 26. Phase separator 27. Expansion valve 28. Container 29. Gas phase 30. Liquid phase 31. Gas discharge