WO2005075901A1

WO2005075901A1 - Refrigerating system and method for operating a refrigerating system

Info

Publication number: WO2005075901A1
Application number: PCT/EP2005/001092
Authority: WO
Inventors: Uwe Schierhorn
Original assignee: Linde Kältetechnik GmbH & Co. KG
Priority date: 2004-02-09
Filing date: 2005-02-03
Publication date: 2005-08-18
Also published as: EP1714094A1; US20070220910A1; DE102004006271A1

Abstract

The invention relates to a novel refrigerating system comprising at least one refrigerating consumer provided with at least one evaporator, at least one supply line and at least one withdrawal line which enable the coolant or the coolant mixture to be supplied to and/or withdrawn from the refrigerating consumer(s). Expansion elements are associated with the evaporator(s). According to the invention, the expansion elements are embodied as modified expansion valves (a, b, c) and/or as modified linear expansion machines or the by-pass lines (4) are associated therewith, and a modified linear compressor (x, y, z) or a traditional compressor (x'), which comprises a by-pass line (5), is associated with each refrigerating consumer (V', V', V''). The modified expansion valve(s) (a, b, c) and/or the modified linear expansion machine(s) and/or the modified linear compressor(s) (x, y, z) have a working position which enables a through-flow without a considerable drop in pressure. The invention also relates to two alternative methods which are used to operate a refrigerating system.

Description

description

Refrigeration system and method for operating a refrigeration system

The invention relates to a refrigeration system with at least one, at least one evaporator cooling consumer, at least one supply and at least one discharge line, via which the refrigerant or refrigerant mixture is supplied to the cold consumer (s) or removed from the cold consumer (s), the evaporator (s) Expansion organs are assigned.

Furthermore, according to a first alternative, the invention relates to a method for operating a refrigeration system, wherein modified expansion valves and modified linear compressors are assigned to the refrigeration consumer (s).

According to a second alternative, the invention relates to a method for operating a refrigeration system, by-pass lines being assigned to the conventional expansion valve and the conventional compressor (s) of the refrigeration consumer.

The term "modified expansion valves" should be understood below to mean all expansion valves which, in addition to the primary function "expansion of a liquid", have the secondary function "realization of a fluid connection". The term "modified compressor" in the following encompasses all compressors which, in addition to the primary function "compression of a gas", enable the secondary function "realization of a fluid connection".

The terms "conventional expansion valves" and "conventional compressors" are to be understood in the following as all known constructions of expansion valves and compressors that do not have the aforementioned secondary function.

Generic refrigeration systems are operated, for example, in supermarkets or wholesale stores. They generally supply a large number of refrigeration consumers, such as cold rooms, refrigerators and / or freezers. For this purpose, a one- or multi-component refrigerant or mixture of refrigerants circulates in them. Such a refrigeration system - as is known from DE-PS 39 28 430 - has a condenser in which the pressurized refrigerant (mixture) is condensed by indirect heat exchange, preferably against outside air.

The liquid refrigerant (mixture) from the condenser is fed to an optional container. There must always be enough refrigerant in a refrigeration system that the evaporators of all refrigeration consumers can be filled even when there is a maximum demand for refrigeration. However, since individual evaporators are only partially filled or even completely empty when the cooling requirement is low, the excess refrigerant (mixture) must be collected in the storage container provided during these times.

The refrigerant (mixture) is fed from the collection container to the cold consumers via at least one liquid line. An expansion device, preferably an expansion valve, is connected upstream of each refrigeration consumer, in which the refrigerant (mixture) flowing into the refrigeration consumer or the evaporator (s) of the refrigeration consumer is expanded. The refrigerant (mixture) which has been expanded in this way is evaporated in the evaporators of the refrigerant consumers and thus cools the corresponding refrigeration cabinets or rooms.

The evaporated refrigerant (mixture) is then fed to a compressor unit via a suction line. These compressor units can be designed in one or more stages. The individual compressor stages usually have several compressors connected in parallel. These compress the refrigerant (mixture) and convey it via a riser to the previously mentioned condenser. While the compressor unit is normally located, for example, in a machine room located in the basement of a supermarket, the condenser is located on the roof of the supermarket.

Rotary driven, oil-lubricated reciprocating compressors are generally used as compressors. The disadvantage here is that appropriate measures must be taken to enable the oil discharged from the reciprocating compressor to be separated from the refrigerant (mixture). In addition, it must generally be ensured that the separated oil is in turn fed to the reciprocating compressor (s). In order for the oil to be separated, the mixture of refrigerant and oil must be used are first routed to certain points in the circuit, which is why minimum speeds have to be reached in rising suction and pressure lines, otherwise the oil would not be carried along. These minimum speeds make the pipe diameters smaller, which results in additional, undesirable pressure losses and thus energy losses. In order to be able to avoid these pressure and energy losses in riser pipes, pipe splits have to be made, which, however, in turn results in increased installation outlay. Process engineering aspects are therefore undesirably closely linked to economic aspects.

As an alternative to the procedure described above, the system of a cold vapor compressor refrigeration system, in which a distinction is made between subcritical (with re-liquefaction) and supercritical (with gas recooling) operation, so that a "gas cooler" takes the place of the component "condenser" Refrigeration system also circulate a gaseous refrigerant (mixture), which is never available in liquid form under the given boundary conditions (pressure, temperature, etc.) One then speaks of a so-called cold gas refrigeration system, which is called "Joule, Stirling or "Gifford McMahon Plant" is known.

In the following, only the term "condenser" is used. If it is a cold vapor compression process in the two-phase area, a condenser is actually used. In the case of a supercritical driving style or in gas processes, the term "liquefier" stands for a gas cooler. It is essential that heat is removed from the cycle. The liquefaction can be carried out in an air-cooled apparatus, in a medium-pressure separator or by another set in a cascade connection. A cascade connection is always present when there is another chiller that is operated at a higher temperature level and that only releases the heat of condensation to the environment. In this case, the refrigeration unit depends on this refrigeration machine and in turn transfers its heat of condensation to it. For example, a normal chiller can be connected upstream of a freezer, whereby both chillers can have different refrigerants (mixtures).

If there are so-called normal and so-called deep-freeze points within a large or supermarket, these are usually separated by means of separate ones Refrigerant circuits supplied; this means that a refrigeration system as described in DE-PS 39 28 430 is present at least twice.

The refrigeration system or the evaporators arranged in the refrigeration consumers must be defrosted at regular intervals, since frosting or icing of the evaporators leads to a reduction in the efficiency of the evaporators. One way of defrosting is electrical defrosting. In this, the evaporators are defrosted by means of electrical heaters arranged on and / or in them. However, this procedure leads to an undesirable additional consumption of electrical energy.

So-called compressed gas defrosting is an alternative to the above-described electrical defrosting. on. In this case, compressed gas lines are laid between the gas space of the collecting container connected downstream of the condenser and each evaporator or evaporator group and, via these, gaseous refrigerant, which preferably has a temperature between 35 and 45 ° C., is fed from the collecting container to the evaporators or evaporator groups. However, the installation effort for this compressed gas defrost is comparatively high, since either a separate compressed gas line must be provided for each evaporator or each evaporator group or, as is usual with the two-pipe system, changeover valves and a second set with the same refrigerant (mixture) are required , There is also the possibility of defrosting by means of circulating air at temperatures above approx. 2 ° C.

The object of the present invention is to provide a refrigeration system of the generic type which has advantages over the refrigeration systems which belong to the prior art with regard to their investment and operating costs and reliability.

To solve this problem, a refrigeration system is proposed, which is characterized in that the expansion elements are designed as modified expansion valves and / or as modified linear expansion machines or bypass lines are assigned to them, and Each refrigeration consumer is assigned a modified linear compressor or a conventional compressor which has a by-pass line, the modified expansion valve (s) and / or the modified linear expansion machine (s) and / or the modified linear compressor (s) Have working position that allow a flow without significant pressure drop.

Most linear compressors work as oil-free cryo-Stirling coolers at the lowest temperatures and the lowest outputs, i.e. in cold vapor compression. Linear compressors have only been used in cold steam compression for a few years and have only been used to a limited extent. The applicant is only aware of one application in the cooling sector, namely the use of a linear compressor in a household refrigerator. A disadvantage of linear compressors is that their manufacturing costs have so far been significantly higher than those of rotary driven reciprocating compressors, but on a similar scale as

Inverter compressor. For the first time, efforts were made in the 1960s to take advantage of linear compressors. The principle of bearing the piston without friction stems from this time. It was only in the 1990s that improvements in operational safety were achieved thanks to reliable, electronic stroke controls. Care should be taken to ensure that, for example, changing pressures neither lead to the piston striking the cylinder head nor to premature termination of the lifting process at top dead center, combined with too much volume of the displacement and volumetric or energetic disadvantages of back expansion.

Linear compressors have the advantage that they allow stepless output control, which is achieved by stroke control. They can also be operated oil-free. In addition, the condensate that inevitably arises during defrosting does not damage them. They are also energetically superior to rotary driven, oil-lubricated reciprocating compressors.

Although they are operated oil-free, the oil-lubricated, rotatively driven compressors are superior in terms of energy. This results on the one hand from the efficient linear motor, and on the other hand from the elimination of the mechanical losses, which are about 80% of the drive value and about 20% of the piston. The piston of one The linear compressor is mounted without contact and can be guided through so-called "flexible bearings" - that is, flexible bearings - which enable axial mobility combined with radial rigidity. Ultimately, it is a combination of springs that unwind and wind up, which, in addition to its periodic translational movement, causes the piston to rotate about its longitudinal axis.

Linear compressors can be operated oil-free because they have no plain bearings. There are a number of advantages to this freedom from oil. In the case of compressed gas defrosting with condensation, the previously comparatively vulnerable bearings can no longer be damaged by liquid refrigerant (mixture). The known acid formation in the lubricating oils, which can lead to the so-called Burπ-Out of the winding in built-in motors, has hitherto been more or less effectively avoided by the use of refrigerant dryers. These molecular sieve dryers can now be omitted, unless the water content is so high that ice loss is to be feared during expansion. Regardless of this, it is advisable to provide dirt filters directly in front of the expansion valves or machines.

Linear compressors also have the advantage that they are not damaged by the pumping of liquid - in contrast to other compressor designs. Pumping liquid is particularly an issue after the end of a defrosting process, as at this point u. U. condensate still remains in the defrosted evaporators, which is sucked in by the compressor when it is restarted. However, it is advisable to ensure that liquid is pumped carefully. This means that small strokes are first started to limit the maximum performance of the compressor during the liquid flow and to protect the working valves and the stroke catcher. A constructive solution has also already been proposed in which a disc valve as a pressure valve replaces the cylinder head; this leads to very high operational reliability.

In contrast to the known refrigeration systems belonging to the prior art, circuits are now possible in which the supply and discharge lines assigned to the refrigeration consumer (s) contain the liquid to be injected and the compressed gas of the compressor (s). On the one hand, this eliminates a central one Suction line and on the other hand, the compressors are no longer spatially separated from the consumer (s), but are located in the immediate vicinity of the cooling consumer (s).

The compressor sets previously to be provided in refrigeration systems can now be omitted, since at least one individual compressor is assigned to each consumer. This means that every consumer can be controlled individually and continuously using his own compressor. In contrast to the known procedures or refrigeration systems, this individual regulation can now take place independently of the temperature level in the return line, since the return or discharge line is no longer the suction line, the pressure of which depends on the evaporation temperature, which determines the temperature of the refrigeration consumers. is dependent, but the pressure line.

Provided that it should not be impossible due to other boundary conditions, freezer furniture can, for example, be used and operated temporarily as normal refrigerated furniture and / or shelves for fresh meat for dairy products. In the simplest case, this changeover is carried out by adjusting a temperature selection button on the respective refrigerated cabinet. Furthermore, a pressure line - compared to the corresponding suction line - has a smaller diameter and does not require any insulation.

As already mentioned at the beginning, the invention further relates to two alternative methods for operating a generic refrigeration system in order to implement a compressed gas defrosting method.

The first alternative of the method according to the invention for operating a refrigeration system is characterized in that during the defrosting phase of the or at least one of the refrigeration consumers, the modified expansion valve (s) and the modified linear compressor (s) of the refrigeration consumer (s) to be defrosted are moved into the working position , in which a flow is possible without any significant drop in pressure.

The second alternative of the method according to the invention for operating a refrigeration system is characterized in that the associated by-pass lines are opened during the defrosting phase of the or at least one of the refrigeration consumers and the associated conventional expansion valve and the associated conventional compressor (s) are taken out of operation.

The refrigeration system according to the invention, the methods according to the invention for operating a refrigeration system and further refinements of the refrigeration system according to the invention and the methods according to the invention are explained in more detail with reference to the exemplary embodiments illustrated in FIGS. 1, 2 and 3.

FIG. 1 shows a refrigeration system according to the invention, by means of which three refrigeration consumers V, V "and V" are supplied. Of course, the number of refrigeration consumers can be as large as desired. The above-mentioned refrigeration consumers are supplied via a (central) feed line 1 and lines 1 ', 1 "-as well as 1'" branching therefrom, the refrigerant or mixture of refrigerants - hereinafter referred to as "refrigerant".

According to the invention, the evaporator of each refrigeration consumer V, V "and V" is now either upstream of a modified expansion valve a, b or c or - as shown in FIG. 2 - the upstream conventional expansion valve a 'has a by-pass, shown in broken lines - Line 4 on. FIG. 2 shows an example of an embodiment of the refrigeration system according to the invention that is alternative to the embodiment shown in FIG. Instead of the modified expansion valve a, b or c shown in FIG. 1, modified linear expansion machines can also be used.

After expansion in the valves a, b and c or a 'described above, the expanded refrigerant is fed via lines 2', 2 "or 2 '" to the evaporators of the refrigeration consumers V, V "or V" and evaporated therein ,

By means of the modified linear compressors x, y and z, the evaporated refrigerant is then fed back to the (central) return line 3 via the return lines 3 ', 3 "or 3'". Instead of the modified linear compressors x, y and z shown in FIG. 1, it is also possible to provide a conventional compressor x 'which has a by-pass line 5, shown in dashed lines; this Embodiment of the refrigeration system according to the invention is also shown in Figure 2.

If, for example, the refrigeration consumer V or its evaporator is now to be defrosted, the modified linear compressor x and the modified one

Move expansion valve a into the working position in which it is possible for the modified linear compressor x and the modified expansion valve a to flow through the modified linear compressor x without significant pressure loss. According to the invention, the warm refrigerant from the refrigeration consumers V "and / or V" now passes through line 3 'through the opened modified one

Linear compressor x to the evaporator of the refrigeration consumer V and defrosts it. ^' Via line 2', the opened modified expansion valve a and the line, the refrigerant cooled and possibly condensed by the defrosting process is fed back to the (central) supply line 1 and then reaches lines 1 and 1 '' again to the cooling consumers V "and V".

If - as shown in FIG. 2 - by-pass lines 4 and 5 are provided, the conventional expansion valve a 'and the conventional compressor x' go out of operation and the refrigerant required for defrosting the evaporator of the refrigeration consumer V passes through the lines 3 'and 5 to the defrost

Evaporator of the refrigeration consumer V. After defrosting, the refrigerant is then returned to the (central) supply line 1 via lines 2 ', 4 and 1'.

According to an advantageous embodiment of the refrigeration system according to the invention, the refrigeration consumers V, V "and / or V" - as shown in FIG. 1 - can be connected to the supply line 1 and the discharge line 3 by means of couplings, preferably by means of quick couplings K, in particular by means of standardized quick couplings become.

In addition or as an alternative to the procedure shown in FIG. 1, the refrigeration consumers V, V, V ",... Can also - as shown in FIG. 2 - be connected to one another in segments and directly, including the main lines 1 and 3. It is important to ensure that, under certain circumstances, consumers or condensers are at a different level - for example, cold rooms that are located in other floors of a wholesale market - are connected to each other, but a direct coupling or connection is not possible in every case.

The flexibility of the refrigeration system according to the invention can be increased further by means of these advantageous configurations of the refrigeration system according to the invention described above.

Both methods according to the invention for operating a refrigeration system now make it possible for one or more refrigeration consumers to be defrosted at the same time to be defrosted by the other refrigeration consumer (s) in the cooling phase. This is possible without the need for additional pipeline networks and / or additional energy sources - as they were previously required for pressurized gas defrosting.

Further developing the refrigeration system according to the invention it is proposed that - the or at least one of the refrigeration consumers has its own closed refrigerant (mixture) circuit, the refrigerant (mixture) circuits are operatively connected to the supply and discharge lines via at least one condenser and or the refrigerant (mixed) circuits each have modified expansion valves and / or modified linear expansion machines or conventional valves with assigned by-pass lines and modified linear compressors or conventional compressors with assigned by-pass lines, the ^' evaporator of a refrigeration consumer being higher than that Condenser of the refrigeration consumer is arranged.

FIG. 3 shows the aforementioned embodiment of the refrigeration system according to the invention using the refrigeration consumer V as an example.

Here, the refrigeration consumer V, V "or V" has its own

Refrigerant (mixed) circuits 6, 7, 8 and 9. This is in operative connection via the condenser E with the feed line 1 and the discharge line 3. The refrigerant (mixed) circuit 6, 7, 8 and 9 has either a modified expansion valve a and a modified linear compressor x or a modified linear expansion machine or the conventional valve or Conventional expansion machines and the conventional compressor are assigned bypass lines, which are drawn with dashed lines in FIG. 3.

Those line sections and components which are components of the refrigeration consumer itself are surrounded in FIG. 3 by the dash-dotted line. The supply 1 and discharge line 3 can optionally be included here.

In order to be able to realize an automatic refrigerant (mixed) circulation in the defrosting operation, it is necessary that the evaporator of the refrigeration consumer V is arranged higher than the heat exchanger E.

With this configuration, the flexibility of the refrigeration system according to the invention can be significantly increased compared to refrigeration systems of the generic type, since this configuration of the refrigeration system according to the invention enables the (subsequent) integration of further refrigeration consumers into the refrigeration system network.

As already mentioned, at least two separate refrigerant (mixed) circuits must be provided in the refrigeration systems belonging to the prior art when both normal and deep-freeze points or consumers are to be supplied with cold. This problem is also eliminated with the refrigeration system according to the invention, since now only one refrigerant (mixture) circuit has to be provided.

The linear compressors to be provided are operated oil-free. In the refrigeration system according to the invention, all of the measures that were previously required that would be required for the separation, return, distribution and storage of the oil are thus eliminated. Since the transportation or distribution of the oil within the pipeline network is no longer an issue, the dimensioning of the individual pipelines or pipe sections can now only be based on economic criteria.

Due to the invention, it is no longer necessary to install so-called cold compound kits. Rather, at least in a comparatively large area, a large number of individual and possibly different cooling consumers can be converted into an existing system Liquid line, gas or pressure line and condenser (retrofitted) can be integrated or removed. This is made possible in particular by the fact that the previously described, previously described compressor sets of the composite refrigeration systems can be dispensed with, since each refrigeration consumer now has his own compressor which is adapted to the respective boundary conditions and conditions of the refrigeration consumer.

Claims

claims

1. Refrigeration system with at least one, at least one evaporator cooling consumer, at least one supply and at least one discharge line, via which the refrigerant or refrigerant mixture is supplied to the cooling consumer (s) or is removed from the cooling consumer (s), the expansion evaporator (s) being assigned to the evaporator (s) are characterized in that - the expansion members are designed as modified expansion valves (a, b, c) and / or as modified linear expansion machines or bypass lines (4) are assigned to them, and - each refrigeration consumer (V, V ", V" ) a modified linear compressor (x, y, z) or a conventional compressor (x ¹ ), which has a by-pass line (5), is assigned, - the or the modified expansion valves (a, b, c) and / or the modified linear expansion machine (s) and / or the modified linear compressor (s) (x, y, z) have a working position that a Allow flow without significant drop in pressure.

2. Refrigeration system according to claim 1, characterized in that - the or at least one of the refrigeration consumers (V, V ", V") has its own closed refrigerant (mixture) circuit (6, 7, 8, 9), - or Refrigerant (mixture) circuits (6, 7, 8, 9) are operatively connected to the supply (1) and discharge line (3) via at least one condenser (E) and - the refrigerant (mixture) circuits (6, 7, 8, 9) respectively modified expansion valves (a, b, c) and / or modified linear expansion machines or conventional valves (a ¹ ) with assigned by-pass lines and modified linear compressors (x, y, z) or conventional compressors with have assigned by-pass lines, - the evaporator of a refrigeration consumer (V, V ", V") each being arranged higher than the condenser (E) of the refrigeration consumer (V, V ", V").

3. Refrigeration system according to claim 1 or 2, characterized in that the refrigeration consumer (V, V ", V") by means of couplings, preferably by means of quick couplings (K), in particular by means of standardized quick couplings, with the feed (1) and the discharge line ( 3) and / or are interconnectable.

4. Refrigeration system according to one of the preceding claims 1 to 3, characterized in that one or more of the cooling consumers (V, V ", V") subcoolers are assigned as internal heat exchangers.

5. A method for operating a refrigeration system according to one of the preceding claims 1 to 4 ^' , wherein the expansion consumer and modified linear valves or modified linear compressors are assigned, characterized in that during the defrosting phase of or at least one of the refrigeration consumers (V, V ", V ") the modified expansion valve (s) (a, b, c) and the modified linear compressor (s) (x, y, z) of the cooling consumer (s, V, V", V ") are moved into the working position, in which a flow is possible without a notable drop in pressure.

6. A method of operating a refrigeration system according to one of the preceding claims 1 to 4, wherein the or the conventional expansion valves and the or the conventional compressors of the refrigeration consumer or by-pass lines are assigned, characterized in that during the defrosting phase of or at least one of the refrigeration consumers (V, V ", V") opens the associated by-pass lines (4, 5) and the associated conventional expansion valve (s ') and the associated conventional compressor (x') except Be put into operation.