EP0577869B1 - Refrigeration system with a vacuum-tight collecting conduit for the vapor of the working fluid - Google Patents

Abstract

Refrigeration system with a vacuum-tight collecting conduit (1) for the vapour of the working fluid, which contains at least two connection points (2...11), to which any evaporators (13, 19, 22, 28, 32, 34) for working fluid or a sorbent medium container (42) with a sorbent filling (43) which can absorb the working fluid can be connected in a vacuum-tight manner. <IMAGE>

Description

The invention relates to a cooling system with a working medium vapor manifold, to which at least one evaporator and at least one sorbent container are connected in a vacuum-tight manner.

DE-OS 3425419 discloses cooling processes based on the sorption principle, water being evaporated from an aqueous solution and adsorbed as water vapor in a sorbent filling. The amount of steaming water cools down while the sorbent filling is heated. This process takes place in closed systems in which the negative pressure, in order to allow the aqueous solution to evaporate at correspondingly low temperatures, is built up during the manufacture of the system and is maintained for the period of use. These cooling devices are relatively inflexible because the evaporator must always be firmly connected to the entire device.

From DE-OS 4003107 an ice maker based on the sorption principle is known. Here, an aqueous liquid is frozen in an icing vessel using a vacuum-proof sorbent container that contains a solid sorbent and to which a vacuum pump is connected. This ice maker is used, for example, to make ice cubes for cooling beverages.

A continuously operating cooling system with zeolite is known from FR-A-2 544 842. A working fluid evaporator and a condenser are connected to at least one zeolite adsorber via a connecting line. Several shut-off valves open the path of the working fluid vapor from the evaporator to the zeolite filling or from the zeolite filling to the condenser. A vacuum pump is used to maintain the negative pressure. It is coupled to the working fluid steam line via a shut-off device.

The object of the present invention is to develop a universally applicable cooling system which can also be operated economically.

This object is achieved by the features of claim 1.

The subclaims represent further advantageous methods and configurations.

The cooling system thus consists, on the one hand, of a vacuum-tight working medium vapor manifold which contains at least two connection points to which at least one evaporator and at least one sorbent container can be connected in a vacuum-tight manner. A vacuum pump is also required for operation in order to generate sufficient vacuum, for example when using zeolite as sorbent and water as working medium, so that water can evaporate at low temperatures. For economic reasons, the vacuum pump should only be put into operation when the System pressure conditions make this necessary and be out of order for the rest of the time.

Vacuum pumps suitable for this have long been state of the art. However, vacuum pumps without oil lubrication, so-called dry-running vacuum pumps, are particularly advantageous. With a two-stage, dry-running vacuum pump, final pressures of 8 hPa can be achieved today. A three-stage pump must be provided for lower pressures.

Vacuum ejectors have also recently become known. which are powered by compressed air. These usually multi-stage Venturi nozzles reach final pressures of 8 hPa by means of a compressed air supply of 5 to 6 bar. Compressed air supply systems of this type are used in many commercial operations but also in larger trucks. present on the train and in airplanes. Since these vacuum pumps are extremely inexpensive and have low air consumption, a cooling system with these vacuum pumps is particularly economical.

Since at high altitudes the ambient air pressure is only between 200 and 300 hPa, compressed air-powered vacuum ejectors can work even more economically and efficiently.

However, cooling systems that are installed in cars can also benefit from the vacuum devices that are common today. Since many vehicle components, such as central locking, braking and steering assistance, require negative pressure, it also makes sense here. to replace the current vacuum pump with a pump with a lower final pressure. The additional effort is low, since neither a new motor nor a more complex control are necessary. The additional weight is also limited. because an additional suction stage can only be integrated in the pump housing.

The vacuum pump evacuates the sorbent container, the working fluid vapor manifold and the connected evaporators via a connecting line. It is advantageous to use a device in the connecting line between the sorbent container and the vacuum pump which prevents air from entering the cooling system when the vacuum pump is at a standstill and thus adversely affecting the adsorption in the sorbent. For example, simple check valves come into question, but also mechanically or electrically operated valves.

The sorbent container itself can be designed in a variety of ways. However, all constructions must be carried out so that the working fluid vapor flowing into the sorbent container can reach all layers of sorbent. This is imperative. Extract air and non-condensable gases from all areas of the sorbent filling. The incoming working fluid vapor must not prevent the air cushions from being extracted. It is therefore advisable to arrange the inlet opening of the working fluid vapor on one side and the connection line to the vacuum pump on the other side of the sorbent filling.

It is also advantageous to carry out the connection points on the sorbent container by means of light or quick-release connections. This ensures easy replacement of the sorbent container when the sorbent is saturated.

Sorbent containers with saturated sorbent can generally be regenerated by adding heat at higher temperatures. The working fluid is expelled in vapor form from the sorbent. This regeneration can take place at any time and in any place. It is advantageous, for example. To do this, use waste heat flows from combustion processes or use low-tariff electricity via an electric heater. Depending on the regeneration method, the sorbent containers can be adapted to the regeneration process by installing an electrical resistance heater or by designing thermodynamically favorable heat exchanger outer walls.

Also the dissipation of the heat of reaction, which is released during the sorption of working fluid vapor in the sorbent filling. is very effectively possible using the latter. Of course, the heat of sorption can also be dissipated and used in any other known manner.

Of course, regeneration of the sorbent filling can also be carried out without prior separation from the working agent vapor manifold. Appropriately, however, the entry of expelled working fluid vapor into the manifold must be prevented. This is made possible by simple check valves at the connection points, but also mechanically or electrically operated shut-off valves. If it is possible to re-liquefy the escaping working fluid vapor, it can be returned to the evaporator via separate lines.

All absorption and adsorption substances known from refrigeration technology can be considered as sorbents. The use of molecular sieves or zeolites has proven to be particularly advantageous. Zeolites adsorb up to 30 percent by weight of water and release it again in vapor form at temperatures of up to 300 ° C. Accordingly, the ideal working fluid is water, which evaporates in the evaporators and flows in vapor form via the working fluid vapor manifold into the zeolite containers. Since the vapor pressure of water is relatively low, the vacuum pump must reach a minimum pressure of 6.1 hPa, for example, to enable evaporation temperatures of 0 ° C. At this pressure, the water in the evaporator can completely ice up. This creates the possibility of further cooling the evaporator arrangement even after uncoupling from the working fluid vapor manifold by generating a larger ice reserve. Only if the vacuum pump can generate the low pressure can the water vapor flow unhindered through the manifold into the sorbent container and be adsorbed by the zeolite filling.

All vacuum-proof and vacuum-tight lines are suitable as working medium vapor manifolds. Since the working fluid vapor generally has relatively low temperatures, flexible plastic lines can also be used. In principle, all known fittings can be used at the connection points. It is important that all connection points not occupied by an evaporator can be closed, for example by self-closing quick couplings.

If both the evaporator and the sorbent container can be easily connected, the working medium vapor manifold can also be installed stationary at the respective place of use. It then connects, for example, all evaporator connection points with a single sorbent container or else only a single evaporator with several sorbent containers. Of course, connection points via which only small steam volumes are to be drawn off can also be integrated into a larger cooling system with smaller line cross sections. In this way, a highly branched manifold network can be created, which is designed, for example, for only one sorbent container with only one vacuum pump.

In this invention, the term “evaporator” denotes all devices in which the working fluid evaporates and flows out in vapor form into the working fluid vapor manifold. So everyone comes as an evaporator systems that are common in refrigeration today, in particular the evaporator plate of a refrigerator or freezer, the evaporation line of a beverage cooler or the air cooler of an air conditioning system.

The surface, the flow cross-section and the general design of the evaporator are characterized by the work equipment used. When water is used as the working medium, the evaporator can, for example, advantageously adopt the evaporator types according to German laid-open publications DE-OS 4003107 and DE-OS 4138114. Since all evaporator types can be permanently connected to one and the same working medium vapor manifold, but the evaporation temperatures should be adjustable to different depths, it is advantageous if a steam throttle is installed either in the evaporator itself or at the connection point to the working medium steam manifold, which controls the steam flow reduced so much that a higher evaporation temperature is possible than the working fluid vapor pressure in the working fluid vapor manifold would allow. The working fluid vapor pressure in the manifold determines the lowest possible evaporation temperature in the connected evaporators.

In principle, the vacuum pump could be in operation without interruption in order to maintain the negative pressure required for the evaporation of the working fluid. But if the cooling system is sufficiently tight. it is sufficient if the vacuum pump only sucks the penetrated gases or the non-condensable gases released from the sorbent from time to time in order to make the sorbent filling accessible to the working fluid vapor. For energy reasons, however, it makes sense to start the vacuum pump only if possible when new evaporators are connected or when a temporarily lower evaporation temperature is necessary when connecting devices for ice production.

Processes that only start the vacuum pump when this is absolutely necessary are advantageous. It can thus be achieved that the cooling system only has to be evacuated for a few seconds per day, for example. There are several ways to start up the vacuum pump. On the one hand, a rising evaporation temperature in the evaporator can close a built-in thermostat and thus start the vacuum pump. Since it will usually take some time until the evaporation temperature has dropped so far that the thermostat closes again, it makes sense to equip the vacuum pump with a timer which switches the pump off after a few seconds, although the thermostat is still closed.

Another way to turn on the vacuum pump. offer pressure switches. With these, the switch-on pressure can be set in a simple manner, at which the vacuum pump switches on and switches off again after falling below the limit. But it is also advantageous to provide the connection points of the manifold with a contact. which puts the vacuum pump into operation for a predetermined period of time when coupling an evaporator.

It is particularly advantageous. if the cooling system is equipped with a so-called cold surface. This cold surface makes it possible to liquefy working fluid vapor or even freeze it out at temperatures below 0 ° C and the use of water as working fluid. However, this only makes sense if the cold surface is at a lower temperature level than the lowest evaporation temperature in the evaporator. For example, when using the cooling system in the household during the winter months, the working fluid vapor that is produced in the evaporator of a refrigerator can condense on the cold surface, which is cooled, for example, by the cold environment. In this way, no sorbent is necessary to sorb the working fluid vapor and consequently no regeneration of the sorbent. It is also particularly advantageous. to combine the cold surface with the sorbent container. This always seems to make sense if the sorbent container is at least temporarily exposed to lower temperatures. Even when using a cold surface, it must be ensured that non-condensable gases can be extracted from the system via an evacuation device.

Aircraft that fly through a very cold environment at great heights offer further applications for a cold surface. The temperatures at these altitudes can well be -50 ° C. Transport containers for food and beverages, so-called trolleys or entire cargo hold areas can be cooled via the cold surfaces during the flight. The working fluid vapor flowing out of the evaporators of the trolleys can condense or freeze out on the cold surfaces. At the bottom and during the start phase, the sorbent filling takes over the sorption of the working fluid vapor. It is also particularly advantageous if the entire cabin is air-conditioned via the cooling system according to the invention. The alternating regeneration of two sorbent fillings then takes place through hot exhaust gases from the turbine or via the so-called "bleed-air", which is on board at over 200 ° C is available. In this case, the working medium steam manifold could be firmly integrated into the aircraft and at appropriate connection points with air heat exchangers and ice makers. Trolleys etc. can be coupled at will.

Another very interesting application opens up in hotels and restaurants. Here, for example, the usual absorber mini-bar refrigerators can be replaced by simple evaporator refrigerators, which are connected to a working steam collection line, which has one or more connection points in each hotel room. In one central place. for example the engine room. the manifold opens into one or more larger sorbent containers. which can be regenerated alternately via waste heat from a wide variety of sources and at various times. Of course, this invention can also be used in private households, where refrigerators and air conditioning evaporators can be installed in any number of rooms.

What is possible in the hotel and household. can of course also be used in vehicles. In cars, trucks as well as camping vehicles, a convenient cooling system can be installed through the stationary laying of a working fluid vapor manifold with various connection points, which fulfills all conceivable cooling tasks today. For the air conditioning of vehicles, it is particularly advantageous to permanently install the vacuum pump and the working fluid vapor manifold in the vehicle, while the sorbent container and evaporator are only transported in the vehicle when needed. In this way, air conditioning can be realized, which is only for a certain period. which depends on the sorbent capacity cools a vehicle. Of course, longer cooling times without regeneration are also possible if several replacement sorbent containers are carried.

Another application example is the air conditioning of railway wagon compartments. Each wagon compartment can be air-conditioned by means of an evaporator, which in these cases acts as an air heat exchanger, via a single working medium vapor manifold. Here too, the provision of further connections means, for example, that cool boxes brought by passengers, which contain a corresponding evaporator. be connected. Likewise, the advantageous possibilities of direct ice production are also conceivable here. But the system according to the invention also opens up new application possibilities in the train restaurant. For example, one could Set up a self-service system in which the passenger cools the beverage he has selected while dispensing via an evaporator according to the invention. There is no need to keep pre-cooled beverage containers ready. Each trolley is advantageously equipped with its own sorbent container and an associated vacuum pump. A connecting line between the individual carriages can thus be omitted.

In the drawing, several types of evaporators are connected to a working medium vapor manifold with a sorbent container and a cold surface.

A working medium vapor manifold 1 contains connection points 2 to 11. The connection point 2 is associated with a non-return valve 12 which prevents water vapor from flowing into the refrigerator evaporator 13. A float valve 14 allows water 15 to enter in small quantities from a storage tank 16 when the water level drops. The refrigerator-evaporator 13 is thermally insulated by a housing 16 and is accessible via a door 17. The evaporation temperature in the refrigerator evaporator 13 is determined by the water vapor pressure in the working fluid vapor manifold 1. The lower the working fluid vapor pressure, the lower the evaporation temperature in the refrigerator evaporator 13.

The connection point 3 is formed, for example, by a ball valve to which a flat sealing surface 18 is flanged. Vessels 19 whose opening cross section is smaller than the diameter of the flat sealing surface 18 can be attached to them. be coupled. When the ball valve 3 is opened, the pressure inside the vessel 19 drops and the aqueous liquid 20 can evaporate. This cools down and freezes. After closing the ball valve 3 and opening a ventilation valve 21, the vessel 19 with the frozen liquid can be removed. It is particularly advantageous. if the vessels 19 have thermal insulation (not shown) and are used as an insulation box. The following cooling time depends on the amount of ice produced.

The connection point 4 is connected to an air cooler 22. through which a fan 23 promotes air to be cooled. A thermostat 24 lets water 25 suck from a storage vessel 26 into the air cooler 22. The water evaporates there and cools the conveyed air flow.

The connection point 5 is closed by a blind plug and can be opened for any evaporator system if required.

The connection point 6 also contains a ball valve which, like the connection point 3, is connected to a flat sealing plate 27. The opening of this plate 27 points upwards, so that double-walled vessels 28, which contain an absorbent medium 29 in the interior of their jacket space, can be placed. By opening the ball valve 6, water evaporates from the absorbent mass 29, cools it down and generates an ice buffer. After removing the vessel 28 (the ball valve 6 is also closed beforehand and the system is ventilated as at the connection point 3), it can be used as a drinking cup.

The connection point 7 consists of a quick coupling that closes on both sides. This is connected to a mobile transport trolley 30 (trolley), which e.g. used for the transportation and storage of food and beverages in aircraft. The trolley evaporator 32 is designed in this type as a supporting side element. At the same time, it has guide rails on which trays 31 or inserts rest. The trolley, which is protected on the outside by insulation 33, is connected in aircraft galleys via the quick coupling to the on-board working fluid vapor manifold. Previously, the trolley in the catering station was loaded with on-board catering and the water supply in the trolley evaporator 32 was frozen by direct evaporation. The ice buffer built in this way also bridges longer waiting times before the trolley is connected from the catering station to the on-board working fluid steam collecting line.

The connection point 8 is connected to a beverage cooling system 34. This consists of an evaporator vessel 35, which contains a water reservoir 36, in which a stainless steel cooling coil 37 is guided. When the tap 38 is opened carefully, a valve 39 is first opened. so that water vapor can flow into the working fluid vapor collecting line 1 and the remaining amount of water together with the cooling coil 37 cools. After a few seconds, the amount of water 36 has cooled to such an extent that, by completely opening the tap 38, the liquid to be cooled can enter a container 41 through the cooling coil 37 and be cooled in a container 41 which is kept ready. By closing the tap 38, the valve 39 is closed again, so that no standstill losses occur. The container 40 can be stored at room temperature without loss.

The connection point 9 is connected to a sorbent container 42 which contains zeolite 43. An electrical heater 44 is used to regenerate the zeolite filling 43. In the lower region of the zeolite filling 43, a suction line 45 with a coupling point 46 is connected to two vacuum pumps 47, 48 opposite the connection point 9. Both vacuum pumps are connected to the suction line 45 via check valves 49, 50. The vacuum pump 47 is designed as a compressed air ejector. As soon as compressed air flows through the supply line 51, a negative pressure is generated by the Venturi effect, which evacuates the entire cooling system via the suction line 45 and the zeolite filling 43. The alternatively switchable, mechanical vacuum pump 48 is driven by an electric motor 52. which only goes into operation when a pressure sensor 54 reports excessive pressure via a signal line 53. The pressure sensor 54 is coupled to the working fluid vapor manifold 1 via the connection point 10.

Finally, a condenser 55 is connected to the connection point 11, which liquefies the water vapor from the working medium vapor manifold or condenses it as frost via cold condensation surfaces. The evaporation temperatures in the evaporators must of course be higher than the temperature of the cold surface. The gases which hinder the free flow of water vapor can also be pumped out of the vacuum pumps 47 or 48 via a coupling point 56 and a shut-off valve 57. A non-return valve 58 prevents water vapor from flowing back into the working fluid vapor manifold 1 if the temperatures in the condenser 55 rise too high in the meantime. The liquefied water vapor 60 collects in the bottom of the condenser 55 and can be drawn off via an emptying valve 59 if necessary. It is particularly advantageous if this condensate is fed back into the storage vessels 26 and 16, for example via liquid lines. In aircraft, the cold surfaces can be cooled by the outside air.

Claims (15)

1. Cooling system with a vacuum-tight working medium vapour collecting line (1) with at least one connection point (2-8) for connection of an evaporator (13, 19, 22, 28, 30, 34) and with a sorption medium container (42) with a sorption medium filling (43) connectable to a further connection point (9) and to which a vacuum pump (47, 48) is connected, characterised in that a plurality of further connection points (2-8) are provided for interchangeable connection of any number of further evaporators (13, 19, 22, 28, 30, 34), the connection points (5) not connected to an evaporator being closed vacuum-tight.
2. Cooling system according to claim 1, characterised in that the inlet opening of the working medium vapour in the sorption medium container (42) is disposed on one side of the sorption medium filling (43) and the connecting line to the vacuum pump (47, 48) is disposed on the other side of the sorption medium filling (43), and in that the vacuum pump (47, 48) only comes into operation when infiltrated gases or non-condensable gases released from the sorption medium filling must be sucked out in order to make the sorption medium filling (43) accessible to the working medium vapour.
3. Cooling system according to one of the preceding claims, characterised in that the connecting points (2-8) to the working medium vapour collecting line (1) or the evaporators themselves are equipped with non-return valves (12) which prevent working medium vapour flowing into the evaporators in question.
4. Cooling system according to one of the preceding claims, characterised in that the vacuum pump (47) is an ejector vacuum pump operated with compressed air.
5. Cooling system according to one of the preceding claims, characterised in that the sorption medium (43) contains zeolite and the working medium is water or an acqueous solution.
6. Cooling system according to one of the preceding claims, characterised in that a working medium condenser (55) is connected to the working medium collecting line (1) and has heat exchanger areas which lie at lower temperatures than the lowest evaporation temperature and in that vacuum pump (47, 48) can suck non-condensable gases out of the working medium condenser (55).
7. Cooling system according to one of the preceding claims, characterised in that one of the evaporators (13, 22) has means (14, 24) which allow the evaporated working medium to be topped up.
8. Cooling system according to one of the preceding claims, characterised in that one of the evaporators (19) has a level indicator for the working medium.
9. Cooling system according to one of the preceding claims, characterised in that the working medium in one of the evaporators (19, 32) is ice.
10. Cooling system according to one of the preceding claims, characterised in that one of the evaporators has regulating or control elements which set the vacuum pump (47, 48) in operation if need be.
11. Cooling system according to one of the preceding claims, characterised in that one of the evaporators (13, 34, 19, 32) is designed for cooling of air or liquids and has a thermal insulation.
12. Cooling system according to one of the preceding claims, characterised in that the sorption medium container (42) comprises easily detachable closures (9, 46) which allow simple replacement of the saturated sorption medium filling (43) with a freshly regenerated sorption medium filling.
13. Cooling system according to one of the preceding claims, characterised in that a pressure sensor (54), by means of which the operation of the vacuum pump (48) is switched on or off, is connected to the working medium vapour collecting line (1).
14. Cooling system according to one of the preceding claims, characterised in that one of the evaporators (13, 22, 32) comprises a thermostat which operates the vacuum pump (47, 48) for a short time whenever the evaporation temperature rises above a set temperature.
15. Cooling system according to one of the preceding claims, characterised in that the sorption medium container (42) has means which allow regeneration of the sorption medium filling (43) by hot air, in particular by "bleed air".

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