EP2590878B1 - Refrigeration system for cooling a container - Google Patents

Refrigeration system for cooling a container Download PDF

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Publication number
EP2590878B1
EP2590878B1 EP11722022.8A EP11722022A EP2590878B1 EP 2590878 B1 EP2590878 B1 EP 2590878B1 EP 11722022 A EP11722022 A EP 11722022A EP 2590878 B1 EP2590878 B1 EP 2590878B1
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EP
European Patent Office
Prior art keywords
compressor
cooling
refrigeration system
pressure
container
Prior art date
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EP11722022.8A
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German (de)
French (fr)
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EP2590878A2 (en
Inventor
Wolfgang Sandkoetter
Dieter Mosemann
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GEA Refrigeration Germany GmbH
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GEA Refrigeration Germany GmbH
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/022—Compressor control arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/04—Refrigeration circuit bypassing means
    • F25B2400/0401—Refrigeration circuit bypassing means for the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/07—Details of compressors or related parts
    • F25B2400/075—Details of compressors or related parts with parallel compressors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/13—Economisers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D11/00—Self-contained movable devices, e.g. domestic refrigerators
    • F25D11/003—Transport containers

Definitions

  • the invention relates to a refrigeration system for cooling the interior of a refrigerated container, which can be used universally, for example, on ships, or a truck, a small van, a refrigerated wagon, which is part of a cold chain for transporting refrigerated and frozen goods.
  • the invention thus relates to a refrigeration system for refrigerated transport.
  • container interior, container or refrigerated container are used for these cold rooms in the following text. Accordingly, the term container cooling is used to represent these mobile cold rooms to be cooled.
  • Cooling air flow and the basic structure of refrigerated containers for ships are in DE 202007008764 described.
  • the interior of a refrigerated container is surrounded by thermally insulated side walls, roof and floor, the interior floor generally being designed with air distribution devices, for example longitudinal ribs, which form channels for guiding cold air.
  • the document US 2006/225445 A1 shows a refrigeration system according to the preamble of claim 1.
  • Refrigerated containers must also be built in such a way that they can be transported using the respective specific transport systems on the road, at sea or by rail (truck-trailer reefers, marine reefers or trail reefers).
  • the useful temperature of such a container interior depends on the cargo to be cooled.
  • Such refrigerated containers must be able to carry out cooling or freezing processes for the cargo and then keep them at a predetermined level, the cold storage temperature.
  • the cooling capacity during the cooling or freezing process and during refrigerated transport storage for the same container size differs very significantly depending on the product properties and the usable temperature level in the container interior.
  • different climatic ambient conditions will generally be present on the outer wall of the container, which are regionally caused by passing through different climatic zones or only by the daily course of the temperature, so that the temperature level of the heat sink changes and thus the condensation temperature of the refrigeration system Container cooling.
  • the refrigeration system for container cooling must be able to be operated efficiently and be variable in such a way that the refrigeration capacity and the useful temperature let vary and can be operated economically and environmentally friendly at the different condensation temperatures without restriction.
  • the refrigerated container with its refrigeration system must be able to be operated in a stack of containers; its operating regime must be individually adaptable to the goods to be cooled.
  • one-stage or two-stage refrigeration systems are used in refrigeration systems for container cooling, which have compressors, condensers, expansion devices and evaporators.
  • the container is cooled directly by circulating refrigerant, which absorbs heat from the room to be cooled on the evaporator.
  • the refrigerant is compressed in one or more stages in one or more compressors to a higher pressure and thus to a condensation temperature above the heat sink (container environment) and then cooled by releasing heat to the environment in a gas cooler or in a condenser and then back in one or more stages to the pressure in the evaporator, which creates liquid refrigerant and flash vapor at the lower evaporation temperature of the refrigerant.
  • This arrangement is each carried out only in one stage or only in several stages, so that this refrigeration system, either in the one-stage or in the two-stage version, is not suitable for the desired application range of a refrigerated container.
  • the patent US 4730464 describes a cooling system for cooling a room with air with a compressor and a turbocharger.
  • the variability of the refrigeration system is very limited in terms of refrigeration capacity and evaporation temperature.
  • the patent DE 3620847 discloses an absorption refrigeration system which is supplemented by a heat pipe solar collector.
  • the lack of stackability of such a refrigerated container is disadvantageous for ship use.
  • Container cooling systems with a storage effect without their own refrigeration, with so-called indirect cooling, are also known.
  • the coolant is cooled away from the container and then introduced into cavities on the container.
  • Slurry ice also known as binary ice, cools the wall of the container.
  • the cooling temperature is defined by the ice, which consists of water and additives, and therefore not very much variable. It is not possible to cool an individual container at a different temperature and the cooling time is limited.
  • DE 9110982U1 discloses a container cooling and the channel system required for this by means of cooled water, which is provided by a cold water production system without heat exchangers on the refrigerated container coming into contact with fluorinated hydrocarbons.
  • the container is disadvantageously not self-sufficient.
  • EP0664426 the wall of the container is provided with tubular heat transfer surfaces. Through which a heat transfer fluid with phase change is passed. The cooling process is very slow, so that no cooling can be achieved.
  • the aim and object of the present invention is to provide a refrigeration system for universal cooling of the interior of a container, the usable temperature of which can be adapted within wide limits to the requirements of the goods to be refrigerated, so that cooling or freezing processes and storage of the goods at an individually predetermined temperature level possible are.
  • Another object of the invention is a refrigeration system for cooling the interior of a container, the usable temperature level and the refrigeration capacity thereof can be adapted during the cooling or freezing process and during refrigerated transport storage.
  • Another object of the invention is that the refrigeration system can be operated in a container stack without restrictions during container transport in a wide variety of climatic conditions.
  • Another object of the invention is that the refrigeration system for the container cooling is so variable that the usable temperature and cooling capacity can be adjusted as required and can be operated economically and in an environmentally friendly manner at the different condensation temperatures.
  • the object of the present invention is achieved by a refrigeration system with the features of independent claim 1. Further possible configurations of the invention are specified in the subclaims.
  • the refrigeration system according to the invention has at least two speed-controlled compressors, an n gas cooler, at least one throttle point, at least one internal heat exchanger or an intermediate-pressure liquid separator, an evaporator and controllable valve devices with opening and closing functions, which relate the relative arrangement of the compressors to one another and thus Change the circulation of the refrigerant in the refrigeration system by opening and closing it.
  • a first controllable valve device is arranged on a first compressor as a controllable bypass between the suction and pressure side
  • a second controllable valve device is arranged on a second compressor as a controllable bypass between the suction and pressure side and is a third controllable valve device between the pressure side of the first and suction side of the second compressor.
  • the communicating connection of the first controllable valve device opens on the pressure side of the first compressor after the third controllable valve device (downstream) and the communicating connection of the second controllable valve device branches off on the suction side of the second compressor before the third controllable valve device (upstream ).
  • the compressors can be operated either in parallel, i.e. at the same suction pressure and at the same back pressure, or one after the other, whereby one compressor as the first compression stage (LP or low pressure compressor) and the second compressor as the second Compression stage works at a higher pressure level (HP or high pressure compressor).
  • the usable temperature, cooling capacity and pressure ratio of the compressors can be adapted to requirements within wide limits.
  • the refrigeration is realized in one stage, since the usable temperature is still above freezing.
  • one of the two compressors is used alone to maintain the useful temperature or both compressors are operated in parallel for lowering the temperature from the introduction temperature to a useful temperature.
  • the first and the second controllable valve device are opened and the third controllable valve device is closed. If both compressors work in parallel, they work at the same pressure levels on their suction and pressure side. This operation is referred to here as operating mode NK.
  • TK operating mode For container transport of frozen goods, i.e. at useful temperatures well below freezing, refrigeration is carried out in two stages.
  • the first and the second controllable valve device are closed and the third controllable valve device is opened. This operation is referred to here as the TK operating mode.
  • the suction pressure of the first compressor which forms the first compression stage and is referred to as the low-pressure compressor or LP compressor
  • the back pressure of the LP compressor is roughly the suction pressure of the second compressor, which is the second compression stage forms uhd
  • Both compressors work at different pressure levels on their suction and pressure sides.
  • the back pressure of the HP compressor is the highest pressure in the refrigeration system. Its pressure level corresponds directly to the condensation temperature at pressures that are lower than the critical pressure of the refrigerant used in the refrigeration circuit of the refrigeration system, or the pressure is regulated at pressures above the critical pressure of the refrigerant used as a function of the gas cooler outlet temperature.
  • the high-pressure refrigerant in the internal heat exchanger is cooled by a partial refrigerant flow that is expanded to the pressure level downstream of the LP compressor before it is expanded to the suction pressure of the LP compressor.
  • the partial refrigerant flow evaporates by absorbing heat from the high-pressure refrigerant.
  • This vaporous partial refrigerant stream emerging from the internal heat exchanger is fed to the low-pressure compressor on the pressure side. It is then pumped into the gas cooler by the HP compressor at the highest pressure level.
  • the pressure after the LP compressor determines the degree of cooling of the high-pressure refrigerant. It is based on the relation of the volume flows of LP and HP compressors and can be adjusted by speed control of both compressors in relation to the most economical mode of operation.
  • the operating modes NK and TK can advantageously be combined when storing uncooled goods in order to reduce the cooling rate due to very high cooling capacity to accelerate to a certain temperature.
  • the operating mode NK is first implemented until a predetermined temperature is reached in the refrigerated container.
  • the controllable valve devices are opened or closed as described above for the NK operating mode. Both compressors work at the same pressure level on their suction and pressure side.
  • the system then switches to TK mode, which changes the pressure levels of both compressors, reduces the cooling capacity and increases the efficiency of the cooling process.
  • the controllable valve devices are opened or closed as described above for the TK operating mode. This combination of the two operating modes NK and TK is referred to here as the "cooling-down" mode
  • the three controllable valve devices are opened or closed according to the NK operating mode, although only one of the two compressors is started up.
  • the operating mode NK is retained until the intake pressure has reached a specified target size. Only then are the three controllable valve devices opened or closed in accordance with the TK operating mode, and the second compressor is started up as an LP compressor. Now both compressors work at different pressure levels.
  • the natural refrigerant CO 2 can advantageously be used in the refrigeration cycle, the direct greenhouse potential of which has the value 1 and the heat of vaporization per cubic meter of vapor volume sucked in is approximately ten times greater than that of R134a.
  • compressors and pipe cross sections can be dimensioned very small.
  • the refrigeration system for mobile refrigerated containers can be designed to be very compact and space-saving. Internal heat exchangers or intermediate pressure liquid separators are arranged as described in the exemplary embodiment, so that the known advantages of a CO 2 refrigeration system for economical operation are realized.
  • the arrangement of the compressors according to the invention can be combined with known arrangements of further plant components. These are plant designs with an intercooler, intermediate pressure liquid separator, economizer connection on the compressor or intermediate pressure feed between the compressors.
  • Fig. 1 shows in very simplified form a known single-stage refrigeration cycle process with the refrigerant R134a shown in a section of a pressure-enthalpy diagram (lg p, h diagram) with the four circuit components of a refrigeration system.
  • Fig. 2 the arrangement of the compressors in operating mode NK is shown according to the invention.
  • the compressors work here in a refrigeration system with a liquid subcooler.
  • these compressors have a second connection, an economizer connection, via which fluid can be fed into the working chambers if the pressure is sufficiently high. This allows multi-stage refrigeration system operation.
  • Fig. 3 the arrangement of the compressors in operating mode TK is shown according to the invention, which corresponds to the two-stage arrangement according to the invention.
  • the refrigeration system has an intermediate pressure liquid separator.
  • Fig. 4 the arrangement of the compressors in operating mode TK according to the invention is shown in a refrigeration system with an internal heat exchanger.
  • Fig. 5 shows the single-stage refrigeration cycle process for the NK operating mode with a small temperature difference between heat sink and usable temperature (both compressors work in one stage in parallel operation).
  • Fig. 6 shows the two-stage refrigeration cycle process for the TK mode with a large temperature difference between the heat sink and the useful temperature (one compressor is LP and one compressor is HP).
  • Fig. 7 shows an arrangement according to the invention with a controller, one of the two possible operating modes (operating mode NK) is shown.
  • the compressor 1 (type piston compressor, scroll compressor or rotary piston compressor) raises the pressure from the evaporation pressure to the condensation pressure, which is determined by the temperature of the heat sink and by the refrigerant.
  • the refrigerant is liquefied in the heat exchanger 2 and then expanded into the evaporator 4 at the throttle point 3. This creates flash vapor and liquid.
  • the liquid evaporates by absorbing heat from the interior of the container and thus cools the interior of the container.
  • Fig. 2 shows a refrigeration system with its components which, according to the invention, allow alternate one and two-stage operation of the refrigeration system for container cooling, that is to say can be operated either in the NK or TK operating mode.
  • the NK operating mode is highlighted by thick lines.
  • evaporators 4 In addition to the heat exchanger 2, which works as a condenser or gas cooler depending on the temperature level in relation to the critical temperature of the refrigerant, evaporators 4, compressors 11 and 21, which are operated at a higher or lower speed depending on the power requirement or the operating condition, are a first controllable bypass 13 and a second controllable bypass 23 as well as the first controllable valve device 12, the second controllable valve device 22 and the third controllable valve device 30.
  • the first controllable valve device 12 is arranged on the first compressor 11 as a controllable bypass 13 between its suction and pressure side
  • the second controllable valve device 22 is arranged on the second compressor 21 as a controllable bypass 23 between its suction and pressure side
  • is a third controllable valve device 30 is arranged between the pressure side of the first compressor 11 and the suction side of the second compressor 21.
  • the communicating connection of the first controllable bypass 13 opens on the pressure side of the first compressor 11 after the third controllable valve device 30 (downstream) and the communicating connection of the second controllable bypass 23 branches off on the suction side of the second compressor 21 before the third controllable valve device 30 ( upstream).
  • the compressors 11, 21 can optionally be operated in parallel, that is to say with the same suction pressure and the same back pressure, or in succession, whereby the first compressor 11 as the first compression stage (ND - or low pressure compressor) and the second compressor 21 works as a second compression stage at a higher pressure level (HP or high pressure compressor).
  • controllable valve devices 12 and 22 are open and controllable valve device 30 is closed.
  • NK which is referred to, the two compressors 11 and 21 are operated in parallel. Both compressors work with the same suction pressure and the same back pressure with one-stage compression.
  • the example relates to the use of scroll compressors with an intermediate pressure connection, a so-called economizer connection.
  • Both compressors are of the same type and size with the same application limits. They are shown here in the NK operating mode and are therefore operated with an intermediate pressure feed in single-stage compression, so that the refrigerant is cooled in the inner heat exchanger 50 after leaving the heat exchanger 2 before it is expanded in the first throttle point 52.
  • the cooling is implemented by a partial refrigerant flow which is expanded in the throttle point 51 to the intermediate pressure level. This increases the efficiency of the refrigeration system even with single-stage compressor operation. Necessary valve devices in front of the economizer connections of the two compressors 11 and 21 are not shown in the figure.
  • compressors are operated in the same refrigeration system for another container application for the transport of frozen goods in the TK operating mode.
  • Figure 3 shows a refrigeration system with its components which, according to the invention, allow alternate one and two-stage operation of the refrigeration system for container cooling, that is to say can be operated either in the NK or TK operating mode.
  • the TK operating mode for container transport of frozen goods is highlighted by thick lines.
  • the refrigeration is implemented in two stages.
  • the first controllable valve device 12 and the second controllable valve device 22 are closed and the third controllable valve device 30 is opened.
  • the suction pressure of the first compressor 11 is roughly approximate to the evaporation pressure, and its back pressure is roughly approximate the suction pressure of the second compressor 21. Both compressors operate at different pressure levels on their suction and pressure sides.
  • the back pressure of the compressor 21 is the highest pressure in the refrigeration system. Its pressure level corresponds directly to the condensation temperature at pressures that are lower than the critical pressure of the refrigerant used in the refrigeration system of the refrigeration system, or it is regulated at pressures above the critical pressure of the refrigerant used as a function of the gas cooler outlet temperature.
  • the refrigeration system in Figure 3 shows an intermediate pressure liquid separator 60, which enables a two-stage expansion at the throttling points 61 and 62. Liquid and flash vapor after the first expansion stage are fed in between the compressors 11 and 21 at intermediate pressure, the desired value of which is aimed at by changing the speed of the compressor 21. This increases the efficiency of refrigeration.
  • Figure 4 shows another refrigeration system with its components, which, according to the invention, enables alternate one and two-stage operation for container cooling, that is to say can be operated either in the NK or TK operating mode.
  • the TK operating mode is highlighted by thick lines.
  • the refrigeration system according to Figure 4 shows after the heat exchanger 2, which works depending on the temperature level in relation to the critical temperature of the refrigerant as a condenser or gas cooler, the inner heat exchanger 50, in which the refrigerant is cooled to an intermediate temperature before it is expanded at the throttle point 52.
  • the inner heat exchanger 50 in which the refrigerant is cooled to an intermediate temperature before it is expanded at the throttle point 52.
  • a partial refrigerant flow at the throttle point 51 is expanded to an intermediate pressure, the setpoint of which is regulated by the speed of the compressor 21.
  • the efficiency of refrigeration increases.
  • Fig. 5 shows the single-stage refrigeration cycle process in a pressure-enthalpy diagram for the refrigerant CO 2 in the NK operating mode at a heat sink temperature lower than 32 ° C and a useful temperature higher than 0 ° C.
  • This representation corresponds to the operation of the compressors in operating mode NK. Compression along line 72, heat removal with subsequent liquefaction of the CO 2 along line 73, throttle relaxation along line 74 and evaporation by heat absorption from the interior of the container along line 71 at 0 ° C.
  • the useful temperature of, for example, 12 ° C for banana transport could thus be achieved.
  • Line 76 illustrates the critical temperature isotherm for CO 2 .
  • Fig. 6 shows the two-stage refrigeration cycle according to Figure 3 in a pressure-enthalpy diagram for the refrigerant CO 2 in the TK operating mode at a heat sink temperature greater than 32 ° C and a useful temperature greater than - 32 ° C.
  • This representation corresponds to the operation of the compressors in operating mode TK. Compression along line 72.1 in compressor 11 and compression along line 72.2 in compressor 21, heat extraction in heat exchanger 2 along line 73.1, first stage throttle relaxation along line 74.1 to the temperature level of 25 ° C. with an intermediate cooling effect along line 73.2 and second stage throttle relaxation along line 74.2, evaporation by heat absorption the container interior along line 71 at -30 ° C. This would enable the usable temperature of, for example, -22 ° C for frozen meat to be achieved.
  • Line 76 illustrates the critical temperature isotherm for CO 2 .
  • Fig. 7 shows an arrangement according to the invention with control 80 and the most important control lines for controlling the shut-off valve devices 12, 22, 30 and for speed control of the drive motors 86, 88 for the two compressors 11, 21 and the points for measuring the temperature in the container interior at the temperature Measuring point 92 and for measuring the ambient temperature at temperature measuring point 94; as well as for measuring the pressures at a pressure measuring point 81 before the compressors and a pressure measuring point 97 after the two compressors and a pressure measuring point 96 after the controllable valve device, which in operating mode NK is equal to the suction pressure of the second compressor during this pressure in the TK operating mode there is an intermediate pressure between the first and the second compressor.
  • the above-mentioned measured variables are the input variable at the control 80.
  • the interior temperature at the temperature measuring point 92 is determined from the container 91 as a singular variable or as an average value from a plurality of measuring points (not shown) and is the input variable at the input 93 of the control 80.
  • the decision about the operating mode NK or TK is made by an algorithm in the control which evaluates the temperature in the container interior at the temperature measuring point 92 and the temperature for cooling air at the temperature measuring point 94, the signal of which reaches the control via measuring line 95.
  • the operating mode NK is shown, in which the two compressors 11 and 21 are operated in parallel.
  • the controllable valve devices 12 and 22, the signals of which are output by the controller 80, are opened via the control lines 83 and 84, while the controllable valve device 30 receives no signal from the controller 80 via control line 85 and remains closed when de-energized.
  • the speed of the two drive motors 86, 88 of the first and second compressors 11, 22 changes the control 80 via the control lines 87 for the first compressor and 89 for the second compressor depending on a target / actual comparison of the pressure at the pressure measuring point 81 , which is fed into the controller at input 82, and a setpoint value preset in controller 80.
  • the controller can also regulate the inside temperature of the container using a target / actual comparison using a second algorithm.
  • the refrigeration system is controlled so that the operating modes NK and TK can be changed during operation. This is particularly advantageous when storing uncooled goods in order to shorten the cooling time due to very high cooling capacity up to a certain temperature and to maintain the quality of the product to be cooled.
  • the operating mode NK is first implemented until a target temperature in the refrigerated container is reached.
  • the controllable valve devices 12, 22, 30 are opened or closed as described above for the NK operating mode.
  • the compressors 11, 21 operate at the same pressure levels on their suction and pressure sides.
  • the mode of operation TK is changed, as a result of which the pressure levels of the compressors 11, 21 change, the cooling capacity drops and the efficiency of the cooling generation increases.
  • the controllable valve devices 12, 22, 30 are opened or closed for the TK operating mode.
  • the controlled variable for the first compressor is the pressure at the pressure measuring point 81, as described above for the NK operating mode.
  • the speed of the second compressor is increased or decreased by the controller 80 so that the pressure at the pressure measuring point 96 with a calculated pressure from the current operating conditions at the two pressure measuring points according to the relationship "square root of the product pressure at the pressure Measuring point 81 and pressure at the pressure measuring point 97 "largely coincide.
  • the combination of the two operating modes NK and TK can be operated as rapid cooling immediately after storage in the container, referred to as "cooling-down" mode.
  • This cooling mode starts with the operating mode NK until a specified setpoint is reached at the pressure measuring point and then switches over to the operating mode TK.
  • the algorithm of the control 80 advantageously also starts both compressors of the refrigeration system with the NK operating mode for deep-freeze storage without rapid cooling and switches over to the TK operating mode as previously described.
  • the operating mode NK is maintained until a set intake pressure is reached. Only then are the controllable valve devices 12, 22, 30 opened or closed in accordance with the TK operating mode, and the compressors 11, 21 operate at different pressure levels.
  • the The useful temperature in the interior of a container can be adapted to the requirements of the refrigerated goods within wide limits, so that both cooling processes and refrigerated and freezer storage are possible at an individually specified temperature level.
  • Operating mode and usable temperature level within the cold store of the container are selected as required during refrigerated transport storage and after changing the refrigerated goods so that the refrigerated container can be used efficiently.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Devices That Are Associated With Refrigeration Equipment (AREA)

Description

Die Erfindung betrifft eine Kälteanlage zur Kühlung des Innenraumes eines Kühlcontainers, der beispielsweise auf Schiffen universell eingesetzt werden kann, oder eines Lastkraftwagens, eines Kleintransporters, eines Kühlwaggons, die Teil einer Kühlkette zum Transport von Kühl- und Gefriergut ist. Die Erfindung betrifft somit eine Kälteanlage für gekühlten Transport. Für diese Kühlräume werden im folgenden Text die Begriffe Containerinnenraum, Container oder Kühlcontainer verwendet. Dementsprechend wird stellvertretend für diese zu kühlenden mobilen Kühlräume der Begriff Containerkühlung verwendet.The invention relates to a refrigeration system for cooling the interior of a refrigerated container, which can be used universally, for example, on ships, or a truck, a small van, a refrigerated wagon, which is part of a cold chain for transporting refrigerated and frozen goods. The invention thus relates to a refrigeration system for refrigerated transport. The terms container interior, container or refrigerated container are used for these cold rooms in the following text. Accordingly, the term container cooling is used to represent these mobile cold rooms to be cooled.

Kühlluftführung und prinzipieller Aufbau von Kühlcontainern für Schiffe sind in DE 202007008764 beschrieben. Der Innenraumes eines Kühlcontainers ist von thermisch isolierten Seitenwänden, Dach und Boden umgeben, wobei der Innenboden im allgemeinen noch mit Luftverteileinrichtungen, zum Beispiel Längsrippen, ausgeführt ist, die Kanäle zur Führung von Kaltluft bilden. Das Dokument US 2006/225445 A1 zeigt eine Kälteanlage gemäß des Oberbegriffs von Anspruch 1.Cooling air flow and the basic structure of refrigerated containers for ships are in DE 202007008764 described. The interior of a refrigerated container is surrounded by thermally insulated side walls, roof and floor, the interior floor generally being designed with air distribution devices, for example longitudinal ribs, which form channels for guiding cold air. The document US 2006/225445 A1 shows a refrigeration system according to the preamble of claim 1.

Kühlcontainer müssen außerdem so gebaut sein, dass ihr Transport mit den jeweiligen spezifischen Transportsystemen auf der Straße, auf See oder auf der Schiene (truck-trailer reefers, marine reefers oder trail reefers) möglich ist.Refrigerated containers must also be built in such a way that they can be transported using the respective specific transport systems on the road, at sea or by rail (truck-trailer reefers, marine reefers or trail reefers).

Die Nutztemperatur eines solchen Containerinnenraumes ist dabei von der zu kühlenden Ladung abhängig. Solche Kühlcontainer müssen in der Lage sein, Kühl- oder Gefrierprozesse der Ladung auszuführen und danach auf vorgegebenem Niveau, der Kühllagertemperatur, zu halten.The useful temperature of such a container interior depends on the cargo to be cooled. Such refrigerated containers must be able to carry out cooling or freezing processes for the cargo and then keep them at a predetermined level, the cold storage temperature.

Je nach Produkteigenschaft und Nutztemperaturniveau im Containerinnenraum unterscheidet sich die Kälteleistung während des Kühl- oder Gefrierprozesses und während der Kühltransportlagerung für die gleiche Containergröße sehr deutlich. Während des Kühltransportes eines Containers werden in der Regel unterschiedliche klimatische Umgebungsbedingungen an der Außenwand des Containers anliegen, die regional durch Passieren unterschiedlicher Klimazonen oder nur durch den Tagesgang der Temperatur bedingt sind, so dass sich das Temperaturniveau der Wärmesenke ändert und damit die Kondensationstemperatur der Kälteanlage zur Containerkühlung.The cooling capacity during the cooling or freezing process and during refrigerated transport storage for the same container size differs very significantly depending on the product properties and the usable temperature level in the container interior. During the cooling transport of a container, different climatic ambient conditions will generally be present on the outer wall of the container, which are regionally caused by passing through different climatic zones or only by the daily course of the temperature, so that the temperature level of the heat sink changes and thus the condensation temperature of the refrigeration system Container cooling.

Im Ergebnis muss die Kälteanlage für die Containerkühlung effizient betrieben werden können und so variabel sein, dass sich Kälteleistung und Nutztemperatur variieren lassen und bei den unterschiedlichen Kondensationstemperaturen ohne Einschränkung wirtschaftlich und umweltfreundlich betrieben werden kann.As a result, the refrigeration system for container cooling must be able to be operated efficiently and be variable in such a way that the refrigeration capacity and the useful temperature let vary and can be operated economically and environmentally friendly at the different condensation temperatures without restriction.

Der Kühlcontainer mit seiner Kälteanlage muss in einem Containerstapel betreibbar sein, sein Betriebsregime muss individuell an das zu kühlende Transportgut anpassbar sein.The refrigerated container with its refrigeration system must be able to be operated in a stack of containers; its operating regime must be individually adaptable to the goods to be cooled.

Außerdem sollte Platzbedarf und Masse einer mobilen Kälteanlage möglichst klein sein.In addition, the space and mass of a mobile refrigeration system should be as small as possible.

In Kälteanlagen zur Containerkühlung werden gemäß dem Stand der Technik einstufige oder zweistufige Kälteanlagen eingesetzt, die Verdichter, Kondensator, Expansionseinrichtungen und Verdampfer aufweisen.According to the prior art, one-stage or two-stage refrigeration systems are used in refrigeration systems for container cooling, which have compressors, condensers, expansion devices and evaporators.

Der Container wird durch zirkulierendes Kältemittel, das am Verdampfer Wärme aus dem zu kühlenden Raum aufnimmt, direkt gekühlt. Dazu wird das Kältemittel in einer oder in mehreren Stufen in einem oder mehreren Verdichtern auf einen höheren Druck und damit auf eine Kondensationstemperatur oberhalb der Wärmesenke (Containerumgebung) verdichtet und danach durch Wärmeabgabe an die Umgebung in einem Gaskühler oder in einem Kondensator abgekühlt und danach wieder in einer oder mehreren Stufen auf den Druck im Verdampfer entspannt, wodurch flüssiges Kältemittel und flash-Dampf bei der tieferen Verdampfungstemperatur des Kältemittels entstehen. Diese Anordnung ist jeweils nur einstufig oder nur mehrstufig ausgeführt, so dass diese Kälteanlage entweder in der einstufigen oder in der zweistufigen Ausführung nicht für die gewünschte Anwendungsbreite eines Kühlcontainers geeignet Ist.The container is cooled directly by circulating refrigerant, which absorbs heat from the room to be cooled on the evaporator. For this purpose, the refrigerant is compressed in one or more stages in one or more compressors to a higher pressure and thus to a condensation temperature above the heat sink (container environment) and then cooled by releasing heat to the environment in a gas cooler or in a condenser and then back in one or more stages to the pressure in the evaporator, which creates liquid refrigerant and flash vapor at the lower evaporation temperature of the refrigerant. This arrangement is each carried out only in one stage or only in several stages, so that this refrigeration system, either in the one-stage or in the two-stage version, is not suitable for the desired application range of a refrigerated container.

Das Patent US 4730464 beschreibt ein Kühlsystem zum Kühlen eines Raumes mit Luft mit einem Verdichter und einem Turbolader. Die Variabilität des Kältesystems ist jedoch in Bezug auf Kälteleistung und Verdampfungstemperatur sehr begrenzt.The patent US 4730464 describes a cooling system for cooling a room with air with a compressor and a turbocharger. The variability of the refrigeration system is very limited in terms of refrigeration capacity and evaporation temperature.

Das Patent DE 3620847 offenbart eine Absorptionskälteanlage, die durch einen Wärmerohr-Solarkollektor ergänzt wird. Nachteilig ist für den Schiffseinsatz die fehlende Möglichkeit der Stapelbarkeit eines solchen Kühlcontainers.The patent DE 3620847 discloses an absorption refrigeration system which is supplemented by a heat pipe solar collector. The lack of stackability of such a refrigerated container is disadvantageous for ship use.

Bekannt sind auch Containerkühlungen mit Speicherwirkung ohne eigene Kälteerzeugung, mit sogenannter indirekter Kühlung. Der Kälteträger wird dabei abseits vom Container abgekühlt und danach in Hohlräume am Container eingebracht. Gemäß Patent DE 29722052 kühlt Slurry-Eis, auch als Binäreis bezeichnet, die Wandung des Containers. Die Kühltemperatur ist dabei durch das Eis, das aus Wasser und Zusatzstoffen besteht, definiert und damit nicht sehr variabel. Die Kühlung eines individuellen Containers bei einer anderen Temperatur ist nicht möglich und die Kühldauer ist begrenzt.Container cooling systems with a storage effect without their own refrigeration, with so-called indirect cooling, are also known. The coolant is cooled away from the container and then introduced into cavities on the container. According to patent DE 29722052 Slurry ice, also known as binary ice, cools the wall of the container. The cooling temperature is defined by the ice, which consists of water and additives, and therefore not very much variable. It is not possible to cool an individual container at a different temperature and the cooling time is limited.

Außerdem sind in den meist vertikalen Wänden Eis und Flüssigkeit nicht homogen verteilt.In addition, ice and liquid are not distributed homogeneously in the mostly vertical walls.

DE 9110982U1 offenbart eine Containerkühlung und das dazu erforderliche Kanalsystem mittels gekühlten Wassers, das durch eine Kaltwassererzeugungsanlage bereitgestellt wird, ohne dass Wärmeübertrager am Kühlcontainer mit fluorierten Kohlenwasserstoffen in Berührung kommen. Der Container ist nachteilig nicht autark einsetzbar. DE 9110982U1 discloses a container cooling and the channel system required for this by means of cooled water, which is provided by a cold water production system without heat exchangers on the refrigerated container coming into contact with fluorinated hydrocarbons. The container is disadvantageously not self-sufficient.

Durch Verwendung von Wasser als Kälteträger zielt der Einsatz dieses Patentes auf den Transport von Gütern oberhalb des Gefrierpunktes. Das schränkt auch den Einsatz des Kühlcontainers ein.By using water as a coolant, the use of this patent is aimed at the transportation of goods above freezing. This also limits the use of the reefer container.

In EP0664426 ist die Wandung des Containers mit röhrenförmigen Wärmeübertragerflächen versehen. Durch das ein Wärmeträgerfluid mit Phasenwechsel geführt wird. Der Abkühlprozess ist sehr träge, so dass keine bedarfsgerechte Kühlung erreicht werden kann.In EP0664426 the wall of the container is provided with tubular heat transfer surfaces. Through which a heat transfer fluid with phase change is passed. The cooling process is very slow, so that no cooling can be achieved.

Ziel und Aufgabe der vorliegenden Erfindung ist es, eine Kälteanlage zur universellen Kühlung des Innenraumes eines Containers zu schaffen, dessen Nutztemperatur an die Anforderungen des Kühlgutes in weiten Grenzen angepasst werden kann, so dass. Kühl- oder Gefrierprozesse und Lagerung des Gutes bei individuell vorgegebenem Temperaturniveau möglich sind.The aim and object of the present invention is to provide a refrigeration system for universal cooling of the interior of a container, the usable temperature of which can be adapted within wide limits to the requirements of the goods to be refrigerated, so that cooling or freezing processes and storage of the goods at an individually predetermined temperature level possible are.

Ein weiteres Ziel der Erfindung ist eine Kälteanlage zur Kühlung des Innenraumes eines Containers, deren Nutztemperatumiveau und deren Kälteleistung während des Kühl- oder Gefrierprozesses und während der Kühltransportlagerung angepasst werden können.Another object of the invention is a refrigeration system for cooling the interior of a container, the usable temperature level and the refrigeration capacity thereof can be adapted during the cooling or freezing process and during refrigerated transport storage.

Ein weiteres Ziel der Erfindung besteht darin, dass die Kälteanlage während des Containertransportes bei unterschiedlichsten klimatischen Bedingungen auch in einem Containerstapel ohne Einschränkungen betrieben werden kann.Another object of the invention is that the refrigeration system can be operated in a container stack without restrictions during container transport in a wide variety of climatic conditions.

Ein weiteres Ziel der Erfindung besteht darin, dass die Kälteanlage für die Containerkühlung so variabel ist, dass Nutztemperatur und Kälteleistung bedarfsgerecht angepasst werden können und bei den unterschiedlichen Kondensationstemperaturen ohne Einschränkung wirtschaftlich und umweltfreundlich betrieben werden kann.Another object of the invention is that the refrigeration system for the container cooling is so variable that the usable temperature and cooling capacity can be adjusted as required and can be operated economically and in an environmentally friendly manner at the different condensation temperatures.

Die Aufgabe der vorliegenden Erfindung wird durch eine Kälteanlage mit den Merkmalen des unabhängigen Anspruchs 1 gelöst. Weitere mögliche Ausgestaltungen der Erfindung sind in den Unteransprüchen angegeben.
Die Kälteanlage gemäß der Erfindung hat mindestens zwei drehzahlgeregelte Verdichter, ein n Gaskühler, mindestens eine Drosselstelle, mindestens einen inneren Wärmeübertrager oder einen Zwischendruck-Flüssigkeitsabscheider, einen Verdampfer und steuerbare Ventileinrichtungen mit Öffnungs- und Schließfunktionen, welche die relative Anordnung der Verdichter zueinander und damit die Zirkulation des Kältemittels in der Kälteanlage durch Öffnen und Schließen verändern.The object of the present invention is achieved by a refrigeration system with the features of independent claim 1. Further possible configurations of the invention are specified in the subclaims.
The refrigeration system according to the invention has at least two speed-controlled compressors, an n gas cooler, at least one throttle point, at least one internal heat exchanger or an intermediate-pressure liquid separator, an evaporator and controllable valve devices with opening and closing functions, which relate the relative arrangement of the compressors to one another and thus Change the circulation of the refrigerant in the refrigeration system by opening and closing it.

Gemäß den Merkmalen der Erfindung ist eine erste steuerbare Ventileinrichtung an einem ersten Verdichter als steuerbarer Bypass zwischen Saug- und Druckseite angeordnet, ist eine zweite steuerbare Ventileinrichtung an einem zweiten Verdichter als steuerbarer Bypass zwischen Saug- und Druckseite angeordnet und ist eine dritte steuerbare Ventileinrichtung zwischen Druckseite des ersten und Saugseite des zweiten Verdichters angeordnet.According to the features of the invention, a first controllable valve device is arranged on a first compressor as a controllable bypass between the suction and pressure side, a second controllable valve device is arranged on a second compressor as a controllable bypass between the suction and pressure side and is a third controllable valve device between the pressure side of the first and suction side of the second compressor.

Gemäß den Merkmalen der Erfindung mündet die kommunizierende Verbindung der ersten steuerbaren Ventileinrichtung auf der Druckseite des ersten Verdichters nach der dritten steuerbaren Ventileinrichtung (stromabwärts) und die kommunizierende Verbindung der zweiten steuerbaren Ventileinrichtung zweigt auf der Saugseite des zweiten Verdichters vor der dritten steuerbaren Ventileinrichtung ab (stromaufwärts).According to the features of the invention, the communicating connection of the first controllable valve device opens on the pressure side of the first compressor after the third controllable valve device (downstream) and the communicating connection of the second controllable valve device branches off on the suction side of the second compressor before the third controllable valve device (upstream ).

Durch Änderung der Öffnungs- und Schließstellung der steuerbaren Ventileinrichtungen können die Verdichter wahlweise parallel, das heißt bei gleichem Ansaugdruck und bei gleichem Gegendruck, betrieben werden oder hintereinander, wodurch dabei ein Verdichter als erste Verdichtungsstufe (ND- oder Niederdruckverdichter) und der zweite Verdichter als zweite Verdichtungsstufe bei höherem Druckniveau (HD- oder Hochdruckverdichter) arbeitet.By changing the opening and closing position of the controllable valve devices, the compressors can be operated either in parallel, i.e. at the same suction pressure and at the same back pressure, or one after the other, whereby one compressor as the first compression stage (LP or low pressure compressor) and the second compressor as the second Compression stage works at a higher pressure level (HP or high pressure compressor).

Im Ergebnis der veränderten Öffnungs- und Schließstellungen der steuerbaren Ventileinrichtungen und durch Änderung der Drehzahl der Verdichter können Nutztemperatur, Kälteleistung und Druckverhältnis der Verdichter in weiten Grenzen an den Bedarf angepasst werden.As a result of the changed opening and closing positions of the controllable valve devices and by changing the speed of the compressors, the usable temperature, cooling capacity and pressure ratio of the compressors can be adapted to requirements within wide limits.

Für Containertransport von Frischware, z. B. Obst, Gemüse oder auch Fleisch wird die Kälteerzeugung einstufig realisiert, da die Nutztemperatur noch oberhalb des Gefrierpunktes liegt. Dazu wird einer der beiden Verdichter allein zum Halten der Nutztemperatur oder es werden beide Verdichter für die Temperaturabsenkung von der Einbring- auf eine Nutztemperatur parallel betrieben. Dabei sind die erste und die zweite st uerbare Ventileinrichtung geöffnet und die dritte steuerbare Ventileinrichtung geschlossen. Wenn beide Verdichter parallel arbeiten, arbeiten sie bei gleichen Druckniveaus auf ihrer Saug- und Druckseite. Dieser Betrieb wird hier als Betriebsart NK bezeichnet.For container transport of fresh goods, e.g. B. fruit, vegetables or meat, the refrigeration is realized in one stage, since the usable temperature is still above freezing. For this purpose, one of the two compressors is used alone to maintain the useful temperature or both compressors are operated in parallel for lowering the temperature from the introduction temperature to a useful temperature. The first and the second controllable valve device are opened and the third controllable valve device is closed. If both compressors work in parallel, they work at the same pressure levels on their suction and pressure side. This operation is referred to here as operating mode NK.

Für Containertransport von Gefriergut, also bei Nutztemperauren deutlich unter dem Gefrierpunkt, wird die Kälteerzeugung zweistufig realisiert. Dazu werden die erste und die zweite steuerbare Ventileinrichtung geschlossen und die dritte steuerbare Ventileinrichtung geöffnet. Dieser Betrieb wird hier als Betriebsart TK bezeichnet.For container transport of frozen goods, i.e. at useful temperatures well below freezing, refrigeration is carried out in two stages. For this purpose, the first and the second controllable valve device are closed and the third controllable valve device is opened. This operation is referred to here as the TK operating mode.

Bei Betriebsart TK ist Ansaugdruck des ersten Verdichters, der die erste Verdichtungsstufe bildet und als Niederdruckverdichter oder ND-Verdichter bezeichnet wird, in grober Näherung gleich Verdampfungsdruck, und der Gegendruck des ND-Verdichters ist in grober Näherung Ansaugdruck des zweiten Verdichters, der die zweite Verdichtungsstufe bildet uhd als Hochdruckverdichter oder HD-Verdichter bezeichnet wird. Beide Verdichter arbeiten bei unterschiedlichen Druckniveaus auf ihrer Saug- und Druckseite.In the TK operating mode, the suction pressure of the first compressor, which forms the first compression stage and is referred to as the low-pressure compressor or LP compressor, is roughly equal to the evaporation pressure, and the back pressure of the LP compressor is roughly the suction pressure of the second compressor, which is the second compression stage forms uhd is referred to as high pressure compressor or high pressure compressor. Both compressors work at different pressure levels on their suction and pressure sides.

Der Gegendruck des HD-Verdichters ist der höchste Druck der Kälteanlage. Sein Druckniveau korrespondiert bei Drücken, die kleiner sind als der kritische Druck des im Kältekreislauf der Kälteanlage verwendeten Kältemittels direkt zur Kondensationstemperatur, oder der Druck wird bei Drücken oberhalb des kritischen Druckes des verwendeten Kältemittels in Abhängigkeit der Gaskühleraustrittstemperatur geregelt.The back pressure of the HP compressor is the highest pressure in the refrigeration system. Its pressure level corresponds directly to the condensation temperature at pressures that are lower than the critical pressure of the refrigerant used in the refrigeration circuit of the refrigeration system, or the pressure is regulated at pressures above the critical pressure of the refrigerant used as a function of the gas cooler outlet temperature.

Nach Verlassen des Gaskühlers wird das unter hohem Druck stehende Kältemittel im inneren Wärmeübertrager durch einen Kältemittelteilstrom, der auf das Druckniveau nach dem ND-Verdichter entspannt wird, gekühlt, bevor es auf den Saugdruck des ND-Verdichters entspannt wird. Der Kältemittelteilstrom verdampft durch Wärmeaufnahme aus dem unter hohem Druck stehenden Kältemittel. Dieser aus dem inneren Wärmeübertrager austretende dampfförmige Kältemittelteilstrom wird dem ND-Verdichter auf der Druckseite zugeführt. Er wird danach vom HD-Verdichter bei höchstem Druckniveau in den Gaskühler gefördert.After leaving the gas cooler, the high-pressure refrigerant in the internal heat exchanger is cooled by a partial refrigerant flow that is expanded to the pressure level downstream of the LP compressor before it is expanded to the suction pressure of the LP compressor. The partial refrigerant flow evaporates by absorbing heat from the high-pressure refrigerant. This vaporous partial refrigerant stream emerging from the internal heat exchanger is fed to the low-pressure compressor on the pressure side. It is then pumped into the gas cooler by the HP compressor at the highest pressure level.

Der Druck nach dem ND-Verdichter bestimmt das Maß der Abkühlung des unter hohem Druck stehenden Kältemittels. Er stellt sich aus der Relation der Volumenströme von ND- und HD-Verdichter ein und kann durch Drehzahlregelung beider Verdichter in Bezug auf wirtschaftlichste Betriebsweise angepasst werden.The pressure after the LP compressor determines the degree of cooling of the high-pressure refrigerant. It is based on the relation of the volume flows of LP and HP compressors and can be adjusted by speed control of both compressors in relation to the most economical mode of operation.

Die Betriebsarten NK und TK können vorteilhaft bei Einlagerung ungekühlter Ware kombiniert werden, um die Abkühlgeschwindigkeit durch sehr große Kälteleistung bis zu einer bestimmten Temperatur zu beschleunigen. Dazu wird zunächst die Betriebsart NK realisiert bis eine vorgegebene Temperatur im Kühlcontainer erreicht ist. Die steuerbaren Ventileinrichtungen werden dabei wie oben für die Betriebsart NK beschrieben geöffnet oder geschlossen. Beide Verdichter arbeiten bei gleichen Druckniveaus auf ihrer Saug- und Druckseite. Danach wird auf Betriebsart TK gewechselt, wodurch sich die Druckniveaus beider Verdichter ändern, die Kälteleistung sinkt und die Effizienz der Kälteerzeugung steigt an. Die steuerbaren Ventileinrichtungen werden dabei wie oben für die Betriebsart TK beschrieben geöffnet oder geschlossen. Diese Kombination der beiden Betriebsarten NK und TK soll hier als "cooling-down" Modus bezeichnet werdenThe operating modes NK and TK can advantageously be combined when storing uncooled goods in order to reduce the cooling rate due to very high cooling capacity to accelerate to a certain temperature. For this purpose, the operating mode NK is first implemented until a predetermined temperature is reached in the refrigerated container. The controllable valve devices are opened or closed as described above for the NK operating mode. Both compressors work at the same pressure level on their suction and pressure side. The system then switches to TK mode, which changes the pressure levels of both compressors, reduces the cooling capacity and increases the efficiency of the cooling process. The controllable valve devices are opened or closed as described above for the TK operating mode. This combination of the two operating modes NK and TK is referred to here as the "cooling-down" mode

Auch in der Startphase für die Betriebsart TK ohne "cooling down" - Modus werden die drei steuerbaren Ventileinrichtungen gemäß Betriebsart NK geöffnet beziehungsweise geschlossen, obwohl nur einer der beiden Verdichter in Betrieb genommen wird. Die Betriebsart NK bleibt erhalten, bis der Ansaugdruck einen vorgegebene Soll-Größe erreicht hat. Erst danach werden die drei steuerbaren Ventileinrichtungen gemäß Betriebsart TK geöffnet beziehungsweise geschlossen, und der zweite Verdichter wird als ND-Verdichter in Betrieb genommen. Jetzt arbeiten beide Verdichter bei unterschiedlichen Druckniveaus.Even in the start phase for the TK operating mode without "cooling down" mode, the three controllable valve devices are opened or closed according to the NK operating mode, although only one of the two compressors is started up. The operating mode NK is retained until the intake pressure has reached a specified target size. Only then are the three controllable valve devices opened or closed in accordance with the TK operating mode, and the second compressor is started up as an LP compressor. Now both compressors work at different pressure levels.

Vorteilhaft kann das natürliche Kältemittel CO2 im Kältekreislauf benutzt werden, dessen direktes Treibhauspotential den Wert 1 hat, und dessen Verdampfungswärme pro Kubikmeter angesaugtes Dampfvolumen ungefähr zehnmal größer ist als das von R134a.The natural refrigerant CO 2 can advantageously be used in the refrigeration cycle, the direct greenhouse potential of which has the value 1 and the heat of vaporization per cubic meter of vapor volume sucked in is approximately ten times greater than that of R134a.

Dadurch können Verdichter und Rohrleitungsquerschnitte sehr klein dimensioniert werden. Die Kälteanlage für mobile Kühlcontainer kann sehr kompakt und platzsparend ausgeführt werden. Innere Wärmeübertrager oder Zwischendruck-Flüssigkeitsabscheider sind wie im Ausführungsbeispiel beschrieben angeordnet, sodass die bekannten Vorteile einer CO2-Kälteanlage für wirtschaftliche Betriebsweise realisieret werden.This means that compressors and pipe cross sections can be dimensioned very small. The refrigeration system for mobile refrigerated containers can be designed to be very compact and space-saving. Internal heat exchangers or intermediate pressure liquid separators are arranged as described in the exemplary embodiment, so that the known advantages of a CO 2 refrigeration system for economical operation are realized.

Durch die folgenden Beispiele soll veranschaulicht werden, wie die steuerbaren Ventileinrichtungen die Funktion der Kälteanlage verändern.The following examples illustrate how the controllable valve devices change the function of the refrigeration system.

Die erfindungsgemäße Anordnung der Verdichter kann mit bekannten Anordnungen weiterer Anlagenkomponenten kombiniert werden Das sind Anlagenausführungen mit Zwischenkühler, Zwischendruck-Flüssigkeitsabscheider, Economiseranschluss am Verdichter oder Zwischendruckeinspeisung zwischen den Verdichtern. Durch die folgenden Beispiele soll veranschaulicht werden, dass die Lehre der Erfindung für unterschiedlichste Anlagenkonfigurationen uneingeschränkt anwendbar ist.The arrangement of the compressors according to the invention can be combined with known arrangements of further plant components. These are plant designs with an intercooler, intermediate pressure liquid separator, economizer connection on the compressor or intermediate pressure feed between the compressors. Through the The following examples are intended to illustrate that the teaching of the invention can be used without restriction for a wide variety of system configurations.

Fig. 1 zeigt sehr vereinfacht einen bekannten einstufigen Kältekreisprozess mit dem Kältemittel R134a dargestellt in einem Ausschnitt eines Druck-Enthalpie-Diagramm (lg p,h-Diagramm) mit den vier Kreislaufkomponenten einer Kälteanlage. In Fig. 2 ist die Anordnung der Verdichter in Betriebsart NK gemäß der Erfindung dargestellt. Die Verdichter arbeiten hier in einer Kälteanlage mit Flüssigkeitsunterkühler. Diese Verdichter haben neben dem Ansaugstutzen einen zweiten Anschluss, einen Economiseranschluss, über den Fluid in die Arbeitskammem eingespeist werden kann, wenn der Druck ausreichend groß ist. Das erlaubt mehrstufigen Kälteanlagenbetrieb. Fig. 1 shows in very simplified form a known single-stage refrigeration cycle process with the refrigerant R134a shown in a section of a pressure-enthalpy diagram (lg p, h diagram) with the four circuit components of a refrigeration system. In Fig. 2 the arrangement of the compressors in operating mode NK is shown according to the invention. The compressors work here in a refrigeration system with a liquid subcooler. In addition to the intake manifold, these compressors have a second connection, an economizer connection, via which fluid can be fed into the working chambers if the pressure is sufficiently high. This allows multi-stage refrigeration system operation.

In Fig. 3 ist die Anordnung der Verdichter in Betriebsart TK gemäß der Erfindung dargestellt, was der zweistufigen Anordnung gemäß der Erfindung entspricht. Die Kälteanlage hat einen Zwischendruck-Flüssigkeitsabscheider.In Fig. 3 the arrangement of the compressors in operating mode TK is shown according to the invention, which corresponds to the two-stage arrangement according to the invention. The refrigeration system has an intermediate pressure liquid separator.

In Fig. 4 ist die Anordnung der Verdichter in Betriebsart TK gemäß der Erfindung in einer Kälteanlage mit innerem Wärmeübertrager dargestellt.In Fig. 4 the arrangement of the compressors in operating mode TK according to the invention is shown in a refrigeration system with an internal heat exchanger.

Fig. 5 zeigt den einstufigen Kältekreisprozess für die Betriebsart NK bei kleiner Temperaturdifferenz zwischen Wärmesenke und Nutztemperatur (beide Verdichter arbeiten einstufig im Parallelbetrieb). Fig. 5 shows the single-stage refrigeration cycle process for the NK operating mode with a small temperature difference between heat sink and usable temperature (both compressors work in one stage in parallel operation).

Fig. 6 zeigt den zweistufigen Kältekreisprozess für die Betriebsart TK bei großer Temperaturdifferenz zwischen Wärmesenke und Nutztemperatur (ein Verdichter ist ND- und ein Verdichter ist HD-Verdichter). Fig. 6 shows the two-stage refrigeration cycle process for the TK mode with a large temperature difference between the heat sink and the useful temperature (one compressor is LP and one compressor is HP).

Fig. 7 zeigt eine Anordnung gemäß der Erfindung mit einer Steuerung, dargestellt ist eine der beiden möglichen Betriebsarten (Betriebsart NK). Fig. 7 shows an arrangement according to the invention with a controller, one of the two possible operating modes (operating mode NK) is shown.

Gemäß Figur 1 hebt der Verdichter 1 (Bauart Kolbenverdichter, Scrollverdichter oder Rollkolbenverdichter) den Druck von Verdampfungsdruck auf Kondensationsdruck, der durch die Temperatur der Wärmesenke und durch das Kältemittel bestimmt ist, an. Durch Wärmeabfuhr zur Wärmesenke, zum Beispiel an die Umgebung, wird das Kältemittel im Wärmeübertrager 2 verflüssigt und danach an der Drosselstelle 3 in den Verdampfer 4 entspannt. Dabei entstehen Flash-Dampf und Flüssigkeit. Die Flüssigkeit verdampft durch Wärmeaufnahme aus dem Containerinnenraum und kühlt damit den Containerinnenraum.According to Figure 1 The compressor 1 (type piston compressor, scroll compressor or rotary piston compressor) raises the pressure from the evaporation pressure to the condensation pressure, which is determined by the temperature of the heat sink and by the refrigerant. By dissipating heat to the heat sink, for example to the environment, the refrigerant is liquefied in the heat exchanger 2 and then expanded into the evaporator 4 at the throttle point 3. This creates flash vapor and liquid. The liquid evaporates by absorbing heat from the interior of the container and thus cools the interior of the container.

Die weiten Bedarfsanforderungen an eine Containerkühlung lassen sich durch diese einstufige Ausführung nicht erfüllen. Die zweistufige Ausführung würde diesen Nachteil nicht beseitigen, da sie davon abweichende Einsatzgrenzen hat.The wide-ranging requirements for container cooling cannot be met with this single-stage design. The two-stage version would not eliminate this disadvantage, since it has different application limits.

In Fig. 2 ist eine Kälteanlage mit ihren Komponenten dargestellt, die gemäß der Erfindung wechselweisen ein- und zweistufigen Betrieb der Kälteanlage zur Containerkühlung ermöglichen, also wahlweise in der Betriebsart NK oder TK betrieben werden können. Hervorgehoben durch dicke Linien ist die Betriebsart NK.In Fig. 2 shows a refrigeration system with its components which, according to the invention, allow alternate one and two-stage operation of the refrigeration system for container cooling, that is to say can be operated either in the NK or TK operating mode. The NK operating mode is highlighted by thick lines.

Neben dem Wärmeübertrager 2 der je nach Temperatumiveau in Relation zur kritischen Temperatur des Kältemittels als Kondensator oder Gaskühler arbeitet, sind Verdampfer 4, Verdichter 11 und 21, die je nach Leistungsanforderung oder je nach Betriebsbedingung mit höherer oder niedrigerer Drehzahl betrieben werden, ein erster steuerbarer Bypass 13 und ein zweiter steuerbarer Bypass 23 sowie die erste steuerbare Ventileinrichtung 12 , die zweite steuerbare Ventileinrichtung 22 und die dritte steuerbare Ventileinrichtung 30 dargestellt.In addition to the heat exchanger 2, which works as a condenser or gas cooler depending on the temperature level in relation to the critical temperature of the refrigerant, evaporators 4, compressors 11 and 21, which are operated at a higher or lower speed depending on the power requirement or the operating condition, are a first controllable bypass 13 and a second controllable bypass 23 as well as the first controllable valve device 12, the second controllable valve device 22 and the third controllable valve device 30.

Die erste steuerbare Ventileinrichtung 12 ist am ersten Verdichter 11 als steuerbarer Bypass 13 zwischen dessen Saug- und Druckseite angeordnet, die zweite steuerbare Ventileinrichtung 22 ist am zweiten Verdichter 21 als steuerbarer Bypass 23 zwischen dessen Saug- und Druckseite angeordnet und ist eine dritte steuerbare Ventileinrichtung 30 ist zwischen Druckseite des ersten Verdichters 11 und Saugseite des zweiten Verdichters 21 angeordnet.The first controllable valve device 12 is arranged on the first compressor 11 as a controllable bypass 13 between its suction and pressure side, the second controllable valve device 22 is arranged on the second compressor 21 as a controllable bypass 23 between its suction and pressure side and is a third controllable valve device 30 is arranged between the pressure side of the first compressor 11 and the suction side of the second compressor 21.

Die kommunizierende Verbindung des ersten steuerbaren Bypass 13 mündet auf der Druckseite des ersten Verdichters 11 nach der dritten steuerbaren Ventileinrichtung 30 (stromabwärts) und die kommunizierende Verbindung des zweiten steuerbaren Bypass 23 zweigt auf der Saugseite des zweiten Verdichters 21 vor der dritten steuerbaren Ventileinrichtung 30 ab (stromaufwärts).The communicating connection of the first controllable bypass 13 opens on the pressure side of the first compressor 11 after the third controllable valve device 30 (downstream) and the communicating connection of the second controllable bypass 23 branches off on the suction side of the second compressor 21 before the third controllable valve device 30 ( upstream).

Durch Änderung der Öffnungs- und Schließstellungen der steuerbaren Ventileinrichtungen 12, 22, 30 können die Verdichter 11, 21 wahlweise parallel, das heißt bei gleichem Ansaugdruck und bei gleichem Gegendruck, betrieben werden oder hintereinander, wodurch dabei der erste Verdichter 11 als erste Verdichtungsstufe (ND- oder Niederdruckverdichter) und der zweite Verdichter 21 als zweite Verdichtungsstufe bei höherem Druckniveau (HD- oder Hochdruckverdichter) arbeitet.By changing the opening and closing positions of the controllable valve devices 12, 22, 30, the compressors 11, 21 can optionally be operated in parallel, that is to say with the same suction pressure and the same back pressure, or in succession, whereby the first compressor 11 as the first compression stage (ND - or low pressure compressor) and the second compressor 21 works as a second compression stage at a higher pressure level (HP or high pressure compressor).

In Fig. 2 sind die steuerbaren Ventileinrichtungen 12 und 22 geöffnet, und die steuerbare Ventileinrichtung 30 ist geschlossen. In dieser Betriebsart, die als NK bezeichnet wird, werden die beiden Verdichter 11 und 21 parallel betrieben. Beide Verdichter arbeiten bei gleichem Ansaugdruck und bei gleichem Gegendruck mit einstufiger Verdichtung.In Fig. 2 controllable valve devices 12 and 22 are open and controllable valve device 30 is closed. In this mode, which is called NK is referred to, the two compressors 11 and 21 are operated in parallel. Both compressors work with the same suction pressure and the same back pressure with one-stage compression.

Das Beispiel bezieht sich auf den Einsatz von Scrollverdichtern mit einem Zwischendruckanschluss, einem sogenannten Economiseranschluss. Beide Verdichter sind gleichen Typs und gleicher Baugröße mit gleichen Einsatzgrenzen. Sie werden hier in der Betriebsart NK gezeigt und damit bei einstufiger Verdichtung mit einer Zwischendruckeinspeisung betrieben, so dass das Kältemittel nach Verlassen des Wärmeübertragers 2 im inneren Wärmeübertrager 50 gekühlt wird, bevor es in der ersten Drosselstelle 52 entspannt wird. Die Kühlung wird durch einen Kältemittelteilstrom realisiert, der in der Drosselstelle 51 auf Zwischendruckniveau entspannt wird. Dadurch wird der Wirkungsgrad der Kälteanlage auch bei einstufigem Verdichterbetrieb vergrößert. Notwendige Ventileinrichtungen vor den Economiseranschlüssen der beiden Verdichter 11 und 21 sind in der Figur nicht dargestellt.The example relates to the use of scroll compressors with an intermediate pressure connection, a so-called economizer connection. Both compressors are of the same type and size with the same application limits. They are shown here in the NK operating mode and are therefore operated with an intermediate pressure feed in single-stage compression, so that the refrigerant is cooled in the inner heat exchanger 50 after leaving the heat exchanger 2 before it is expanded in the first throttle point 52. The cooling is implemented by a partial refrigerant flow which is expanded in the throttle point 51 to the intermediate pressure level. This increases the efficiency of the refrigeration system even with single-stage compressor operation. Necessary valve devices in front of the economizer connections of the two compressors 11 and 21 are not shown in the figure.

Diese Verdichter werden in der gleichen Kälteanlage für einen anderen Containereinsatzfall zum Transport von Tiefkühlware in der Betriebsart TK betrieben.These compressors are operated in the same refrigeration system for another container application for the transport of frozen goods in the TK operating mode.

In Figur 3 ist eine Kälteanlage mit ihren Komponenten dargestellt, die gemäß der Erfindung wechselweisen ein- und zweistufigen Betrieb der Kälteanlage zur Containerkühlung ermöglichen, also wahlweise in der Betriebsart NK oder TK betrieben werden können. Hervorgehoben durch dicke Linien ist die Betriebsart TK für Containertransport von Gefriergut.In Figure 3 shows a refrigeration system with its components which, according to the invention, allow alternate one and two-stage operation of the refrigeration system for container cooling, that is to say can be operated either in the NK or TK operating mode. The TK operating mode for container transport of frozen goods is highlighted by thick lines.

Hier wird die Kälteerzeugung zweistufig realisiert. Dazu werden die erste steuerbare Ventileinrichtung 12 und die zweite steuerbare Ventileinrichtung 22 geschlossen und die dritte steuerbare Ventileinrichtung 30 geöffnet. Bei Betriebsart TK liegt der Ansaugdruck des ersten Verdichters 11 in grober Näherung bei Verdampfungsdruck, und sein Gegendruck ist in grober Näherung Ansaugdruck des zweiten Verdichters 21. Beide Verdichter arbeiten bei unterschiedlichen Druckniveaus auf ihrer Saug- und Druckseite.Here, the refrigeration is implemented in two stages. For this purpose, the first controllable valve device 12 and the second controllable valve device 22 are closed and the third controllable valve device 30 is opened. In operating mode TK, the suction pressure of the first compressor 11 is roughly approximate to the evaporation pressure, and its back pressure is roughly approximate the suction pressure of the second compressor 21. Both compressors operate at different pressure levels on their suction and pressure sides.

Der Gegendruck des Verdichters 21 ist der höchste Druck der Kälteanlage. Sein Druckniveau korrespondiert bei Drücken, die kleiner sind als der kritische Druck des im Kältekreislauf der Kälteanlage verwendeten Kältemittels direkt zur Kondensationstemperatur, oder er wird bei Drücken oberhalb des kritischen Druckes des verwendeten Kältemittels in Abhängigkeit der Gaskühleraustrittstemperatur geregelt.The back pressure of the compressor 21 is the highest pressure in the refrigeration system. Its pressure level corresponds directly to the condensation temperature at pressures that are lower than the critical pressure of the refrigerant used in the refrigeration system of the refrigeration system, or it is regulated at pressures above the critical pressure of the refrigerant used as a function of the gas cooler outlet temperature.

Die Kälteanlage in Figur 3 zeigt einen Zwischendruck-Flüssigkeitsabscheider 60, der eine zweistufige Entspannung an den Drosselstellen 61 und 62 ermöglicht. Flüssigkeit und Flash-Dampf nach der ersten Entspannungsstufe werden zwischen den Verdichtern 11 und 21 bei Zwischendruck, dessen Sollwert durch Drehzahländerung des Verdichters 21 angestrebt wird, eingespeist. Dadurch wird der Wirkungsgrad der Kälteerzeugung vergrößert.The refrigeration system in Figure 3 shows an intermediate pressure liquid separator 60, which enables a two-stage expansion at the throttling points 61 and 62. Liquid and flash vapor after the first expansion stage are fed in between the compressors 11 and 21 at intermediate pressure, the desired value of which is aimed at by changing the speed of the compressor 21. This increases the efficiency of refrigeration.

In Figur 4 ist eine andere Kälteanlage mit ihren Komponenten dargestellt, die gemäß der Erfindung wechselweisen ein- und zweistufigen Betrieb zur Containerkühlung ermöglicht, also wahlweise in der Betriebsart NK oder TK betrieben werden kann. Hervorgehoben durch dicke Linien ist die Betriebsart TK.In Figure 4 shows another refrigeration system with its components, which, according to the invention, enables alternate one and two-stage operation for container cooling, that is to say can be operated either in the NK or TK operating mode. The TK operating mode is highlighted by thick lines.

Die Kälteanlage gemäß Figur 4 zeigt nach dem Wärmeübertrager 2, der je nach Temperaturniveau in Relation zur kritischen Temperatur des Kältemittels als Kondensator oder Gaskühler arbeitet, den inneren Wärmeübertrager 50, in dem das Kältemittel auf eine Zwischentemperatur gekühlt wird, bevor es an der Drosselstelle 52 entspannt wird. Dazu wird ein Kältemittelteilstrom an der Drosselstelle 51 auf einen Zwischendruck entspannt, dessen Sollwert durch die Drehzahl des Verdichters 21 geregelt wird. Der Wirkungsgrad der Kälteerzeugung, vergrößert sich.The refrigeration system according to Figure 4 shows after the heat exchanger 2, which works depending on the temperature level in relation to the critical temperature of the refrigerant as a condenser or gas cooler, the inner heat exchanger 50, in which the refrigerant is cooled to an intermediate temperature before it is expanded at the throttle point 52. For this purpose, a partial refrigerant flow at the throttle point 51 is expanded to an intermediate pressure, the setpoint of which is regulated by the speed of the compressor 21. The efficiency of refrigeration increases.

Fig. 5 zeigt den einstufigen Kältekreisprozess in einem Druck-Enthalpie-Diagramm für das Kältemittel CO2 in der Betriebsart NK bei einer Wärmesenken-Temperatur kleiner als 32°C und einer Nutztemperatur größer als 0°C. Diese Darstellung entspricht dem Betrieb der Verdichter in Betriebsart NK. Verdichtung längs der Linie 72, Wärmeentzug mit folgender Verflüssigung des CO2 längs der Linie 73, Drosselentspannung längs der Linie 74 und Verdampfung durch Wärmeaufnahme aus dem Containerinnenraum längs der Linie 71 bei 0°C. Damit könnte die Nutztemperatur von beispielweise 12°C für Bananentransport realisiert werden. Die Linie 76 veranschaulicht die Isotherme der kritischen Temperatur für CO2. Fig. 5 shows the single-stage refrigeration cycle process in a pressure-enthalpy diagram for the refrigerant CO 2 in the NK operating mode at a heat sink temperature lower than 32 ° C and a useful temperature higher than 0 ° C. This representation corresponds to the operation of the compressors in operating mode NK. Compression along line 72, heat removal with subsequent liquefaction of the CO 2 along line 73, throttle relaxation along line 74 and evaporation by heat absorption from the interior of the container along line 71 at 0 ° C. The useful temperature of, for example, 12 ° C for banana transport could thus be achieved. Line 76 illustrates the critical temperature isotherm for CO 2 .

Fig. 6 zeigt den zweistufigen Kältekreisprozess gemäß Figur 3 in einem Druck-Enthalpie-Diagramm für das Kältemittel CO2 in der Betriebsart TK bei einer Wärmesenken-Temperatur größer als 32°C und einer Nutztemperatur größer als - 32°C. Diese Darstellung entspricht dem Betrieb der Verdichter in Betriebsart TK. Verdichtung längs der Linie 72.1 im Verdichter 11 und Verdichtung längs der Linie 72.2 im Verdichter 21, Wärmeentzug im Wärmeübertrager 2 längs der Linie 73.1, erste Stufe Drosselentspannung längs der Linie 74.1 auf das Temperaturniveau von 25°C mit Zwischenkühleffekt längs der Linie 73.2 und zweite Stufe der Drosselentspannung längs der Linie 74.2, Verdampfung durch Wärmeaufnahme aus dem Containerinnenraum längs der Linie 71 bei -30°C. Damit könnte die Nutztemperatur von beispielweise -22°C für Gefrierfleisch realisiert werden. Die Linie 76 veranschaulicht die Isotherme der kritischen Temperatur für CO2. Fig. 6 shows the two-stage refrigeration cycle according to Figure 3 in a pressure-enthalpy diagram for the refrigerant CO 2 in the TK operating mode at a heat sink temperature greater than 32 ° C and a useful temperature greater than - 32 ° C. This representation corresponds to the operation of the compressors in operating mode TK. Compression along line 72.1 in compressor 11 and compression along line 72.2 in compressor 21, heat extraction in heat exchanger 2 along line 73.1, first stage throttle relaxation along line 74.1 to the temperature level of 25 ° C. with an intermediate cooling effect along line 73.2 and second stage throttle relaxation along line 74.2, evaporation by heat absorption the container interior along line 71 at -30 ° C. This would enable the usable temperature of, for example, -22 ° C for frozen meat to be achieved. Line 76 illustrates the critical temperature isotherm for CO 2 .

Fig. 7 zeigt eine Anordnung gemäß der Erfindung mit Steuerung 80 und den wichtigsten Steuerleitungen zur Ansteuerung der absperrbaren Ventileinrichtungen 12, 22, 30 und zur Drehzahlregelung der Antriebsmotoren 86, 88 für die beiden Verdichter 11, 21 und den Punkten zur Messung der Temperatur im Containerinnenraum am Temperatur-Messpunkt 92 und zur Messung der Umgebungstemperatur am Temperatur-Messpunkt 94; sowie zur Messung der Drücke an einem Druck-Messpunkt 81 vor den Verdichtern und einem Druck-Messpunkt 97 nach den beiden Verdichtern und einem Druck-Messpunkt 96 nach der steuerbaren Ventileinrichtung, der in Betriebsart NK gleich dem Ansaugdruck des zweiten Verdichters ist, während dieser Druck in der Betriebsart TK Zwischendruck zwischen dem ersten und dem zweiten Verdichter ist. Fig. 7 shows an arrangement according to the invention with control 80 and the most important control lines for controlling the shut-off valve devices 12, 22, 30 and for speed control of the drive motors 86, 88 for the two compressors 11, 21 and the points for measuring the temperature in the container interior at the temperature Measuring point 92 and for measuring the ambient temperature at temperature measuring point 94; as well as for measuring the pressures at a pressure measuring point 81 before the compressors and a pressure measuring point 97 after the two compressors and a pressure measuring point 96 after the controllable valve device, which in operating mode NK is equal to the suction pressure of the second compressor during this pressure in the TK operating mode there is an intermediate pressure between the first and the second compressor.

Die genannten Messgrößen sind Eingangsgröße an der Steuerung 80. Aus dem Container 91 wird die Innenraumtemperatur am Temperatur-Messpunkt 92 als singuläre Größe oder als Mittelwert aus mehreren nicht dargestellten Messstellen ermittelt und ist Eingangsgröße am Eingang 93 der Steuerung 80.The above-mentioned measured variables are the input variable at the control 80. The interior temperature at the temperature measuring point 92 is determined from the container 91 as a singular variable or as an average value from a plurality of measuring points (not shown) and is the input variable at the input 93 of the control 80.

Die Entscheidung über die Betriebsart NK oder TK fällt ein Algorithmus in der Steuerung, der die Temperatur im Containerinnenraum an der Temperaturmessstelle 92 und die Temperatur für Kühlluft an der Temperaturmessstelle 94, deren Signal über Messleitung 95 zur Steuerung gelangt, auswertet.The decision about the operating mode NK or TK is made by an algorithm in the control which evaluates the temperature in the container interior at the temperature measuring point 92 and the temperature for cooling air at the temperature measuring point 94, the signal of which reaches the control via measuring line 95.

Dargestellt ist die Betriebsart NK, in der die beiden Verdichter 11 und 21 parallel betrieben werden. Die steuerbaren Ventileinrichtungen 12 und 22, deren Signale von Steuerung 80 abgegeben werden, werden über die Steuerleitungen 83 und 84 geöffnet, während die steuerbare Ventileinrichtung 30 über Steuerleitung 85 von der Steuerung 80 kein Signal erhält und stromlos geschlossen bleibt.The operating mode NK is shown, in which the two compressors 11 and 21 are operated in parallel. The controllable valve devices 12 and 22, the signals of which are output by the controller 80, are opened via the control lines 83 and 84, while the controllable valve device 30 receives no signal from the controller 80 via control line 85 and remains closed when de-energized.

Die Drehzahl der beiden Antriebsmotoren 86, 88 des ersten und zweiten Verdichters 11, 22 ändert die Steuerung 80 über die Steuerleitungen 87 für den ersten Verdichter und 89 für den zweiten Verdichter in Abhängigkeit eines Soll-Ist-Vergleiches des Druckes an der Druck-Messstelle 81, der am Eingang 82 in die Steuerung geführt wird, und einem in der Steuerung 80 voreingestellten Sollwert. Die Steuerung kann auch mit einem zweiten Algorithmus die Innentemperatur des Containers über Soll-Ist-Vergleich regeln.The speed of the two drive motors 86, 88 of the first and second compressors 11, 22 changes the control 80 via the control lines 87 for the first compressor and 89 for the second compressor depending on a target / actual comparison of the pressure at the pressure measuring point 81 , which is fed into the controller at input 82, and a setpoint value preset in controller 80. The controller can also regulate the inside temperature of the container using a target / actual comparison using a second algorithm.

Die Steuerung der Kälteanlage ist so ausgeführt, dass die Betriebsarten NK und TK während des Betriebs geändert werden können. Das ist besonders vorteilhaft bei Einlagerung ungekühlter Ware, um die Abkühlzeit durch sehr große Kälteleistung bis zu einer bestimmten Temperatur zu verkürzen und die Qualität des zu kühlenden Produktes zu erhalten.The refrigeration system is controlled so that the operating modes NK and TK can be changed during operation. This is particularly advantageous when storing uncooled goods in order to shorten the cooling time due to very high cooling capacity up to a certain temperature and to maintain the quality of the product to be cooled.

Dazu wird zunächst die Betriebsart NK realisiert, bis eine Solltemperatur im Kühlcontainer erreicht ist. Die steuerbaren Ventileinrichtungen 12, 22, 30 werden dabei, wie oben für die Betriebsart NK beschrieben, geöffnet oder geschlossen. Die Verdichter 11, 21 arbeiten bei gleichen Druckniveaus auf ihrer Saug- und Druckseite.For this purpose, the operating mode NK is first implemented until a target temperature in the refrigerated container is reached. The controllable valve devices 12, 22, 30 are opened or closed as described above for the NK operating mode. The compressors 11, 21 operate at the same pressure levels on their suction and pressure sides.

Danach wird auf Betriebsart TK gewechselt, wodurch sich die Druckniveaus der Verdichter 11, 21 ändern, die Kälteleistung sinkt und die Effizienz der Kälteerzeugung ansteigt. Die steuerbaren Ventileinrichtungen 12, 22, 30 werden dabei für die Betriebsart TK geöffnet oder geschlossen. Regelgröße für den ersten Verdichter ist der Druck an der Druck-Messstelle 81, wie oben für Betriebsart NK beschrieben. Die Drehzahl des zweiten Verdichters wird durch die Steuerung 80 vergrößert oder verkleinert, damit der Druck an der Druck-Messstelle 96 mit einem rechnerischen Druck aus den aktuellen Betriebsbedingungen an den beiden Druck-Messstellen nach der Beziehung "Quadratwurzel aus dem Produkt Druck an der Druck-Messstelle 81 und Druck an der Druck-Messstelle 97" weitestgehend übereinstimmt.Thereafter, the mode of operation TK is changed, as a result of which the pressure levels of the compressors 11, 21 change, the cooling capacity drops and the efficiency of the cooling generation increases. The controllable valve devices 12, 22, 30 are opened or closed for the TK operating mode. The controlled variable for the first compressor is the pressure at the pressure measuring point 81, as described above for the NK operating mode. The speed of the second compressor is increased or decreased by the controller 80 so that the pressure at the pressure measuring point 96 with a calculated pressure from the current operating conditions at the two pressure measuring points according to the relationship "square root of the product pressure at the pressure Measuring point 81 and pressure at the pressure measuring point 97 "largely coincide.

Die Kombination der beiden Betriebsarten NK und TK kann als Schnellabkühlung unmittelbar nach Einlagerung in den Container betrieben werden, als "cooling-down" Modus bezeichnet. Dieser Abkühlmodus startet mit der Betriebsart NK bis ein vorgegebener Sollwert an der Druck-Messstelle erreicht ist und schaltet danach auf die Betriebsart TK um.The combination of the two operating modes NK and TK can be operated as rapid cooling immediately after storage in the container, referred to as "cooling-down" mode. This cooling mode starts with the operating mode NK until a specified setpoint is reached at the pressure measuring point and then switches over to the operating mode TK.

Vorteilhaft startet der Algorithmus der Steuerung 80 auch für Tiefkühllagerung ohne Schnellabkühlung beide Verdichter der Kälteanlage mit der Betriebsart NK und schaltet wie vorher beschrieben auf Betriebsart TK um.The algorithm of the control 80 advantageously also starts both compressors of the refrigeration system with the NK operating mode for deep-freeze storage without rapid cooling and switches over to the TK operating mode as previously described.

Je nach Sollwert der Nutztemperatur bleibt die Betriebsart NK erhalten, bis ein Soll-Ansaugdruck erreicht ist. Erst danach werden die steuerbaren Ventileinrichtungen 12, 22, 30 gemäß Betriebsart TK geöffnet beziehungsweise geschlossen, und die Verdichter 11, 21 arbeiten bei unterschiedlichen Druckniveaus.Depending on the setpoint of the useful temperature, the operating mode NK is maintained until a set intake pressure is reached. Only then are the controllable valve devices 12, 22, 30 opened or closed in accordance with the TK operating mode, and the compressors 11, 21 operate at different pressure levels.

Im Ergebnis der veränderten Öffnungs- und Schließstellungen der steuerbaren Ventileinrichtungen und der damit verbundenen Änderung der Betriebsart von NK zu TK und zurück und durch Änderung der Drehzahl der Verdichter kann die Nutztemperatur im Innenraumes eines Containers an die Anforderungen des Kühlgutes in weiten Grenzen bedarfsgerecht angepasst werden, so dass sowohl Abkühlprozesse als auch Kühl- und Gefrierlagerung bei individuell vorgegebenem Temperaturniveau möglich sind. Betriebsart und Nutztemperatumiveau innerhalb des Kühlraumes des Containers werden während der Kühltransportlagerung und nach Wechsel des Kühlgutes bedarfsgerecht gewählt, so dass der Kühlcontainer effizient eingesetzt werden kann. Aber auch Containertransport bei unterschiedlichsten klimatischen Bedingungen durch verschiedene Klimazonen in einem Containerstapel ist ohne Einschränkungen möglich, da die Wahl der Betriebsart die zu überwindende Temperaturdifferenz zwischen Nutztemperatur und Temperatur der Wärmesenke berücksichtigt. Die Kälteanlage kann damit in Bezug auf Kälteleistung und Energieeffizienz durch die Wahl der besten Betriebsart : in weiten Grenzen optimal betrieben werden, so dass Betriebskosten reduziert werden können. Damit ist der Kühlcontainer in weiten Einsatzgrenzen sehr variabel einsetzbar. Die Kälteleistung kann mit geringstem Energiebedarf erbracht werden. Die eingangs erwähnten Nachteile bekannter Lösungen sind beseitigt.As a result of the changed opening and closing positions of the controllable valve devices and the associated change in the operating mode from NK to TK and back and by changing the speed of the compressor, the The useful temperature in the interior of a container can be adapted to the requirements of the refrigerated goods within wide limits, so that both cooling processes and refrigerated and freezer storage are possible at an individually specified temperature level. Operating mode and usable temperature level within the cold store of the container are selected as required during refrigerated transport storage and after changing the refrigerated goods so that the refrigerated container can be used efficiently. However, container transport in various climatic conditions through different climatic zones in a container stack is also possible without restrictions, since the choice of operating mode takes into account the temperature difference to be overcome between the useful temperature and the temperature of the heat sink. The refrigeration system can thus be optimally operated within wide limits in terms of refrigeration capacity and energy efficiency by choosing the best operating mode, so that operating costs can be reduced. This means that the refrigerated container can be used in a wide variety of ways. The cooling capacity can be achieved with the lowest energy requirement. The disadvantages of known solutions mentioned at the outset are eliminated.

Aufstellung der verwendeten BezugszahlenList of the reference numbers used

11
Verdichtercompressor
22nd
WärmeübertragerHeat exchanger
33rd
DrosselstelleThrottling point
44th
VerdampferEvaporator
1111
erster Verdichterfirst compressor
1212th
erste steuerbare Ventileinrichtungfirst controllable valve device
1313
erster steuerbarer Bypassfirst controllable bypass
2121
zweiter Verdichtersecond compressor
2222
zweite steuerbare Ventileinrichtungsecond controllable valve device
2323
zweiter steuerbarer Bypasssecond controllable bypass
3030th
dritte steuerbare Ventileinrichtungthird controllable valve device
5050
innerer Wärmeübertragerinternal heat exchanger
5151
DrosselstelleThrottling point
5252
DrosselstelleThrottling point
6060
Zwischendruck-FlüssigkeitsabscheiderIntermediate pressure liquid separator
6161
DrosselstelleThrottling point
6262
DrosselstelleThrottling point
7171
Linie der VerdampfungLine of evaporation
7272
Linie der einstufigen VerdichtungLine of single-stage compression
72.172.1
Linie der ersten VerdichtungsstufeLine of the first compression stage
72.272.2
Linie der zweiten VerdichtungsstufeLine of the second compression stage
7373
Linie der WärmeabfuhrHeat dissipation line
73.173.1
Linie der WärmeabfuhrHeat dissipation line
7474
Linie der einstufigen DrosselentspannungLine of single-stage throttle relaxation
74.174.1
Linie der ersten DrosselentspannungLine of the first throttle relaxation
74.274.2
Linie der zweiten DrosselentspannungLine of the second throttle relaxation
7676
Isotherme der kritischen TemperaturCritical temperature isotherm
8080
Steuerungcontrol
8181
Druck-MesspunktPressure measuring point
8282
Eingangentrance
8383
SteuerleitungControl line
8484
SteuerleitungControl line
8585
SteuerleitungControl line
8686
Antriebsmotor erster VerdichterDrive motor of the first compressor
8787
Steuerleitungen erster VerdichterControl lines of the first compressor
8888
Antriebameter zweiter VerdichterDrive parameters of the second compressor
8989
Steuerleitung zweiter VerdichterControl line of the second compressor
9191
ContainerContainer
9292
Temperatur-MesspunktTemperature measuring point
9393
Eingangentrance
9494
Temperatur-MesspunktTemperature measuring point
9595
MessleitungMeasurement line
9696
Druck-MesspunktPressure measuring point
9797
Druck- MesspunktPressure measuring point

Claims (8)

  1. A refrigeration system for cooling an interior of a cooling container by lowering the temperature to a usable temperature and removing heat to a heat sink, comprising a first (11) and a second speed-regulated compressor (21), a gas cooler(2), at least one throttling point (52), at least one inner heat exchanger (50) or an intermediate pressure liquid separator (60), an evaporator (4) and controllable valve devices (12, 22, 30), wherein the first compressor (11) has a first bypass line (13) which establishes a flow connection from the pressure side of said compressor to the suction side thereof and in which a first controllable valve device (12) with opening and closing functions is arranged, wherein the second compressor has a second bypass line (23) which establishes a flow connection from the pressure side of said compressor to the suction side thereof and in which a second controllable valve device (22) with opening and closing functions is arranged,
    wherein a third controllable valve device (30) with opening and closing functions is arranged in a flow connection between the pressure side of the first compressor (11) and the suction side of the second compressor (21), wherein there are means for activating the abovementioned valve devices, and wherein there is a controller which has at least inputs for the usable and ambient temperatures and outputs for actuating the abovementioned valve devices and for separately changing the rotational speed of the two compressors (11, 21), and the controller has algorithms for the different actuation of the three valve devices (12, 22, 30) for different operating modes of the refrigeration system and for changing the rotational speed of the first and the second compressor depending on the usable and ambient temperatures,
    characterized in that
    the communicating connection of the first bypass line (13) branches off on the pressure side of the first compressor (11) after (downstream of) the third controllable valve device (30) and the communicating connection of the second bypass line (23) branches off on the suction side of the second compressor (21) before (upstream of) the third controllable valve device (30).
  2. The refrigeration system for cooling the interior of a cooling container for a single-stage operating method, referred to as the Nk operating mode, as claimed in claim 1, wherein the controller is configured such that the combination of the opening and closing positions is constituted in such a manner that the valve devices in the first and in the second controllable bypass line are open and that the third controllable valve device is closed.
  3. The refrigeration system for cooling the interior of a cooling container for a two-stage operating method, referred to as the TK operating mode, as claimed in claim 1, wherein the controller is configured such that the combination of the opening and closing positions of the three valve devices is constituted in such a manner that the valve devices in the first and in the second controllable bypass line are closed and that the third controllable valve device is open.
  4. The refrigeration system for cooling the interior of a cooling container as claimed in claims 1 to 3, wherein the first and the second compressor are of the same type and same size.
  5. The refrigeration system for cooling the interior of a cooling container as claimed in claims 1 to 4, wherein the refrigerant CO2 is present in the refrigeration circuit.
  6. The refrigeration system for cooling the interior of a cooling container as claimed in claims 1 to 2 and 5, wherein the controller is configured such that the features of the NK and TK operating modes successively form a sequence during start-up of the refrigeration system and for rapid cooling.
  7. The refrigeration system for cooling the interior of a cooling container as claimed in claims 3 and 6, wherein the controller is configured such that the pressure, in the TK operating mode, is kept between the first and the second compressor to a desired value by changing the rotational speed of the second compressor.
  8. The refrigeration system for cooling the interior of a cooling container as claimed in claims 1 to 3, wherein the controller is configured such that in the algorithm the NK operating mode for relatively small differential values between the temperature of the heat sink and the usable temperature and the TK operating mode for greater differential values between temperature of the heat sink and the usable temperature are stored.
EP11722022.8A 2010-07-09 2011-05-28 Refrigeration system for cooling a container Active EP2590878B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102010026648.5A DE102010026648B4 (en) 2010-07-09 2010-07-09 Refrigeration system for cooling a container
PCT/EP2011/002649 WO2012003906A2 (en) 2010-07-09 2011-05-28 Refrigeration system for cooling a container

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EP2590878A2 EP2590878A2 (en) 2013-05-15
EP2590878B1 true EP2590878B1 (en) 2020-04-29

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US (1) US9945597B2 (en)
EP (1) EP2590878B1 (en)
CN (1) CN103038146B (en)
DE (1) DE102010026648B4 (en)
WO (1) WO2012003906A2 (en)

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DE102010026648A1 (en) 2012-01-12
EP2590878A2 (en) 2013-05-15
WO2012003906A3 (en) 2012-03-08
US20130104582A1 (en) 2013-05-02
CN103038146B (en) 2015-01-07
WO2012003906A2 (en) 2012-01-12
CN103038146A (en) 2013-04-10
US9945597B2 (en) 2018-04-17
DE102010026648B4 (en) 2015-12-31

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