EP2565567B1 - Method and device for cooling and generating an atmosphere similar to air and cooling vehicle - Google Patents

Description

The present invention relates to a method and a device for cooling and generating an air-like atmosphere, in particular for cooling of refrigerated goods in a cooling area with application in refrigerated vehicles.

The prior art describes various methods and devices for cooling refrigerated goods. The present invention is concerned with the cooling using cryogenic gases, which are stored and applied in particular in liquefied form. Many of these applications are operated or supervised by humans. In particular, when freezing and transporting goods, in most cases foods, people must have access to the devices and the refrigerated or refrigerated goods. This presupposes that there is an atmosphere that is breathable and safe for humans.

Numerous attempts to use refrigerated liquefied air for cooling encountered various difficulties. On the one hand, it is relatively difficult to produce liquid air in exactly the desired mixing ratio of nitrogen and oxygen, on the other hand, the different boiling points of oxygen and nitrogen, the oxygen depleted in such stores, so that after some time actually no mixing ratio with enough oxygen is present. Although an excessively high oxygen content is not harmful to humans, it increases the risk of fire and explosion, which is why cooling with pure oxygen is generally out of the question. It has therefore typically been preferred in most applications, a cooling with pure nitrogen, but with the result that cold rooms, which are supplied with larger amounts of nitrogen must be well ventilated before a visit by persons or a continuous ventilation process must be carried out, which is energetically mostly unfavorable because some of the cold used can not be used and is discharged with the exhaust air to the environment.

US 5921091 and DE4018265 C1 disclose a method for cooling a chilled goods by means of at least one refrigerated liquefied gas, wherein the cooling takes place in a cooling area in which at least temporarily an air-like and safe for humans breathable atmosphere is needed, wherein at least a first container with cold-liquefied oxygen and at least a second Containers are connected with nitrogen liquefied nitrogen via supply lines to the cooling area, wherein a controller causes nitrogen and oxygen are supplied in such a ratio to the cooling area, there is maintained a mixing ratio approximately corresponding to that in the natural atmosphere of the earth.

US 5921091 and DE4018265 C1 disclose a device for cooling a refrigerated goods by means of at least one refrigerated liquefied gas, wherein the cooling takes place in a cooling area in which at least temporarily an air-like and safe for humans respirable atmosphere is needed, wherein at least a first container with cold-liquefied oxygen and a second container with nitrogen-liquefied nitrogen via supply lines to the cooling area and a control device for controlling the mixing ratio of oxygen and nitrogen is present.

In refrigerated vehicles, various concepts for maintaining the accessibility of a refrigerator have been proposed. One possibility is to use indirect cooling, in which cold is introduced into a cooling area only via heat exchangers. Such a concept is for example in the EP 1 593 918 A2 described. Another possibility is to introduce liquid nitrogen or cryogenic nitrogen gas directly into a cooling area, but to allow a visit only after a thorough ventilation. Such a concept is for example in the WO 2009/147193 A1 described.

In larger plants, where, for example, foods are frozen deeply, there are freezing streets, in which cold-liquefied nitrogen is used as a bath or by means of spraying. Such devices are for example in the EP 0 983 729 A1 described. Since the environment of such cooling equipment for staff must remain accessible, the nitrogen used for cooling is generally sucked off, with a significant portion of the cold used is lost, although the walk-around environment of the cooling device is often kept at a relatively low temperature.

Against this background, it is an object of the present invention to provide a method and apparatus for cooling refrigerated by means of at least one refrigerated liquefied gas, which requires little equipment, uses available refrigeration efficiently and is safe for personnel, refrigerated goods and the technical environment. The application intended for refrigerated vehicles.

To achieve this object, a method according to claim 1 and a refrigerator of a refrigerated vehicle with a device according to claim 7. Advantageous embodiments are specified in the respective dependent claims, wherein the individual configurations can be combined in a technically meaningful way with each other and these combinations belong to the invention. A refrigerated vehicle according to claim 10 is used to solve the tasks set.

The inventive method for cooling refrigerated goods by means of at least one refrigerated liquefied gas, wherein the cooling takes place in a cooling area in which at least temporarily an air-like and safe for humans breathable atmosphere is required, is characterized in that at least one first container with kälteverflüssigtem Oxygen (LOX) and at least one second container with nitrogen liquefied nitrogen (LIN) are connected via supply lines to the cooling area, wherein a regulator causes nitrogen and oxygen to be supplied to the cooling area in such a ratio that there is a mixing ratio approximately corresponding to is maintained in the natural earth atmosphere. Although the invention requires separate containers for storing oxygen and nitrogen, it is relatively uncomplicated in terms of apparatus. In the wake of global efforts to conserve energy, the disadvantage of having two or more separate tanks is not as severe as the useless one Consumption of energy. In the case of vehicles, for reasons of symmetry or other considerations, it makes sense anyway to use more individual tanks in order to stockpile a required medium. For stationary installations, the use of separate tanks is generally not a big problem either.

The concept of the invention is to supply either cryogenic nitrogen or cryogenic oxygen directly to a cooling area for cooling, which only leads to low cooling losses, provided that the cooling area is completed and well insulated. Nevertheless, people can stay in this area at any time as long as it is ensured that if there is a shortage of oxygen cooled with oxygen we will be cooled and if there is too much oxygen enrichment with nitrogen.

In one embodiment of the invention, the nitrogen and oxygen are fed separately to the cooling zone. For this purpose, no precise mixing devices are required to ensure a desired ratio, but the component required in each case can be supplied by very simple control operations in an appropriate amount. It is not necessary to use two completely separate feed systems, but it is also possible to alternately feed a feed system with nitrogen or oxygen as needed.

In another embodiment of the invention, nitrogen and oxygen are first mixed and the resulting mixture is fed to the cooling zone. This variant is particularly suitable for maintaining a specific mixing ratio in the cooling area exactly and to maintain a continuous feed.

In a further embodiment, it is also possible to mix nitrogen and oxygen already in the liquid state in the appropriate ratio, whereby quasi-liquid air is formed. Here, the equipment costs shifted to the mixing process, while the further supply. and regulation is simplified.

According to a preferred embodiment of the invention, the control of the supply of nitrogen and oxygen by means of a control device which is connected to a temperature sensor and / or a mixture ratio of nitrogen and oxygen in the cooling area detecting gas sensor is connected, wherein the control device, the temperature measured by the temperature sensor with a predefinable setpoint temperature and the measured by the gas sensor mixing ratio of nitrogen and oxygen with a desired range, preferably approximately equal to the mixing ratio in the earth's atmosphere, and compares with the set temperature and / or deviation of the mixing ratio of the target range cryogenic oxygen and / or nitrogen are supplied, in such quantities that the setpoint temperature is exceeded and the mixing ratio is in the desired range. If one chooses, for example, the target range for oxygen between 18 and 22%, on the one hand for human respiration well suited and on the other hand not associated with an increased fire hazard, it can be supplied at a oxygen content of 20% and exceeding the target temperature either cryogenic oxygen or cryogenic nitrogen become. Both substances can be used simultaneously for cooling. However, if the oxygen content reaches 22%, then with further cooling required only nitrogen can be used for cooling, the oxygen content falls to 18%, so only oxygen can be used for cooling. Despite the simple control structure, effective cooling can be achieved. Of course, more can be done in the control room Measured values, z. B. on the remaining stocks of oxygen and nitrogen processed and taken into account in the scheme. In the described type of control it is never necessary to perform a ventilation before people enter the cooling area.

To increase safety, it is intended to completely stop the supply of oxygen and nitrogen when one of the components is not or no longer available with a required minimum pressure. This can be accomplished by simple safety valves that only open when a certain minimum pressure is applied. In this way, malfunctions of the control are prevented, because neither nitrogen nor oxygen can be supplied, unless the other component is available for balancing and producing the desired mixing ratio.

Fig. 1:

schematisch den Aufbau einer erfindungsgemäßen Vorrichtung und

Fig. 2:

die Anwendung der Erfindung auf ein Kühlfahrzeug.

Further details and the environment of the invention and exemplary embodiments are explained in more detail below with reference to the drawing. However, the invention is not limited to the exemplary embodiments shown. Show it:

Fig. 1:

schematically the structure of a device according to the invention and

Fig. 2:

the application of the invention to a refrigerated vehicle.

In Fig. 1 A supply of liquid nitrogen LIN in a first container 1 and a supply of liquid oxygen LOX in a second container 2 is shown. From the first container 1, a first feed line 3 leads via a connecting line 19 to a distribution device 11, with the liquid nitrogen, possibly even partially transferred to the gaseous state, can be distributed in a cooling region 20. In general, liquid oxygen LOX can be supplied from the second container 2 via a second supply line 4 and the connection line 19 to the distribution device 11. In the first supply line 3, a first supply valve 5 and a safety valve 7 are arranged one behind the other. The safety valve 7 opens only when a sufficient pressure is applied via a pressure line 10, which is exactly the case when the pressure in the second container 2 is sufficiently high. In the same way, a second supply valve 6 and a second safety valve 8 are arranged in the second supply line 4, wherein the safety valve 8 opens exactly when a sufficiently high pressure corresponding to the pressure in the first container 1 via a first pressure line 9. If the first container 1 or the second container 2 is empty, then the safety valves 7, 8 cause that no gas can be removed from the respective other container. If both containers 1, 2 have sufficient supply and pressure, the device can cool as intended. For this purpose, a temperature sensor 14 measures the temperature in the cooling region 20 and forwards this information via a signal line 15 to a control device 16. At the same time, a gas sensor 13 measures the mixing ratio of nitrogen and oxygen in the cooling region 20 and also forwards this information to the control device 16 via a signal line 15. In the simplest case, the control device 16 is given a desired temperature, beyond which a cooling process is triggered. Reports the temperature sensor 14 a temperature exceeded, so decides the reading of the gas sensor 13, whether oxygen or nitrogen is used for cooling. Again, you can in the simplest case, a limit, for example, specify 20% oxygen content, so that when it exceeds nitrogen and when it falls below Oxygen is used as a coolant. Energetically and for optimum utilization of existing gas reserves, a more complex regulation may make sense. For example, a target range of 18 to 22% oxygen content may be considered permissible, and the controller may then use the distance of the actual value measured by the gas sensor 13 from the limits of the target range to use either nitrogen or oxygen or both for cooling. A uniform distribution of the gases and the cold can be achieved by a blower 17.

The device described here schematically and the associated control can be used in closed systems, for example in cooling chambers or refrigerated vehicles, but also in open systems, such as. B. occur in the production of frozen food in large production halls. The invention even allows previously closed systems with ventilation or suction to be integrated as open systems in a walk-in area, since in the sum for cooling always one of the natural earth atmosphere very similar composition of nitrogen and oxygen can be used. This may even require less cooling for the entire walk-in area.

Fig. 2 schematically shows the application of the present invention to a refrigerated vehicle 18, it should be noted that such a refrigerated vehicle 18 may also have a plurality of separate and separately cooled chambers with different temperature. For simplicity, however, only the cooling of a cooling area 20 with refrigerated goods 12 will be described here. In this refrigerated vehicle 18, the first container 1 and the second container 2 are arranged in the floor area. Here, if necessary, in adaptation to the space conditions in vehicles also several small tanks or tanks of different sizes may be present, with only about a fifth or because of the lower boiling point a little more of the available Storage volume for liquid oxygen must be available. The refrigerated vehicle 18 has a supply means 21 for liquid oxygen and liquid nitrogen, which are structurally based on Fig. 1 contains described parts. Via a connection line 19, liquid oxygen and liquid nitrogen are directed to the distribution device 11, preferably arranged above in the cooling region 20. In this way, depending on the composition of the atmosphere and cooling requirements, either liquid nitrogen or liquid oxygen can be sprayed into the cooling region 20. A fan 17 can be used for uniform distribution of the temperature in the cooling region 20. Here too, a gas sensor 13 and a temperature sensor 14 measure the temperature and the mixing ratio of nitrogen and oxygen in the cooling region 20 and forward this information to the control device 16 via signal lines 15. The controller 16 then controls the feeder 21 in the basis of Fig. 1 already described.

The present invention allows the economical use of cold-liquefied oxygen and nitrogen for cooling refrigerated goods in a cooling area, at any time for people and equipment safe oxygen content can be guaranteed.

LIST OF REFERENCE NUMBERS

1

first container (LIN)

2

second container (LOX)

3

first supply line

4

second supply line

5

first supply valve

6

second supply valve

7

first safety valve

8th

second safety valve

9

first pressure line

10

second pressure line

11

distribution facility

12

refrigerated

13

gas sensor

14

temperature sensor

15

signal lines

16

control device

17

fan

18

Reefer Truck

19

connecting cable

20

cooling area

21

feeder

LIN

cold-liquefied nitrogen

LOX

cold-liquefied oxygen

Claims (10)

1. A method for cooling goods (12) to be cooled by means of at least one low-temperature liquefied gas, wherein the cooling is carried out in a cooling region (20), in which at least at times an atmosphere that is similar to air and can be safely breathed in by people is required, wherein at least one first container (1) with low-temperature liquefied oxygen (LOX) and at least one second container (2) with low-temperature liquefied nitrogen (LIN) are connected to the cooling region (20) via supply lines (3, 4), wherein the cooling region (20) is the cooling chamber of a cooling vehicle (18), wherein the first container (1) and the second container (2) are formed as four or five similar individual containers, of which only one contains liquid oxygen (LOX), and wherein it is achieved via a control unit (16) that nitrogen and oxygen are supplied to the cooling region (20) in such a ratio that a mixing ratio that approximately corresponds to that in the natural atmosphere of the earth is maintained there, wherein the supply of oxygen and nitrogen is completely terminated as soon as one of the components is no longer available at a required minimum pressure.
2. The method as claimed in claim 1, characterised in that the nitrogen and the oxygen are supplied separately to the cooling region (20).
3. The method as claimed in claim 1, characterised in that the nitrogen and the oxygen are initially mixed to form a mixture and the mixture is supplied to the cooling region (20).
4. The method as claimed in claim 3, characterised in that the nitrogen and the oxygen are mixed in a liquid state.
5. The method as claimed in claim 3, characterised in that the oxygen and the nitrogen are mixed in a gaseous state and the mixture is supplied to the cooling region in the gaseous state.
6. The method as claimed in any one of the preceding claims, wherein the temperature in the cooling region (20) is detected using a temperature sensor (14) and/or the mixing ratio between nitrogen and oxygen in the cooling region (20) is detected using at least one gas sensor (13), and wherein by means of the control unit (16), the temperature is compared with a specifiable target temperature and the mixing ratio of nitrogen and oxygen is compared with a target range, preferably approximately equal to the mixing ratio in the atmosphere of the earth, and wherein in case the target temperature is exceeded and/ or the mixing ratio deviates from the target value, cryogenic oxygen and/or nitrogen is/are supplied in such amounts that the temperature falls below the target temperature and the mixing ratio is within the target range.
7. A cooling chamber in a cooling vehicle (18), comprising a device for cooling goods (12) to be cooled by means of at least one low-temperature liquefied gas, wherein the cooling is carried out in a cooling region (20), in which at least at times an atmosphere that is similar to air and can be safely breathed in by people is required, wherein at least one first container (1) with low-temperature liquefied oxygen (LOX) and a second container (2) with low-temperature liquefied nitrogen (LIN) are connected to the cooling region (20) via supply lines (3, 4), wherein the first container (1) and the second container (2) are formed as four or five similar individual containers, of which only one contains liquid oxygen (LOX), and wherein a control unit (16) for controlling the mixing ratio of oxygen and nitrogen is provided, wherein the cooling region (20) is the cooling chamber of the cooling vehicle (18), on which the device is provided, and wherein in the supply line (3, 4), from each container (1, 2) one after the other a supply valve (5, 6), which is connected to the control unit (16) via a signal line (15), and a safety valve (6, 7), which is opened only if a minimum pressure is present in the respectively other container (2, 1), are provided.
8. The cooling chamber of a cooling vehicle (18), comprising a device according to claim 7, wherein a gas sensor (13) and/or a temperature sensor (14) are mounted in the cooling region (11) and are connected to the control unit (16) via signal lines (15).
9. The cooling chamber of a cooling vehicle (18), comprising a device as claimed in any one of claims 7 to 8, wherein a distribution unit (11), in particular a spray unit, is provided in the cooling region (20) and is connected to the containers (1, 2) via the supply lines (3, 4) and at least one connection line (19).
10. A cooling vehicle (18) comprising a cooling chamber and a device according to any one of claims 7 to 9.

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