DE19920726A1 - Refrigeration system - Google Patents

Abstract

The refrigeration installation has separate refrigerator and freezer circuits each containing a compressor (C1/C2,C3/C4/C5/C with the pressure lines (8,16) leading from the latter combined before a condenser (V) and coupled via a selectively blocked def line (30) with the suction line (10) of the compressor (C3/C4/C5/C6) for the freezer circuit.

Description

The invention relates to a refrigeration system for cooling at least one Temperaturver need by means of a normal cooling circuit and for cooling at least one Refrigeration consumers using a deep-freeze circuit, with each of the circuits having a Compressor unit, only one condenser is provided and the pressure lines from the compressor units are brought together in front of the condenser.

Refrigeration systems are operated, for example, in supermarkets. They supply in there general a variety of refrigeration consumers, such as cold rooms, refrigeration and Freezer. For this purpose, a one- or multi-component circulates in them Refrigerant or refrigerant mixture. Such a refrigeration system - like that from the DE-PS 39 28 430 is known - has a condenser in which the under pressure standing refrigerants through indirect heat exchange, preferably against outside air, is condensed.

The liquid refrigerant from the condenser is fed to a collection container. There must always be as much refrigerant in a refrigeration system as it does at maximum cooling demand, the evaporators of all cooling consumers are filled can. However, since individual evaporators are only partially used when cooling is low are filled or even completely empty, the excess refrigerant must during these times are collected in the designated container.

In principle, however, it is also conceivable that such a container is waived.

The refrigerant is fed to the refrigeration consumers from the collection container.

Every refrigeration consumer has an expansion device, preferably an expan Sionsventil upstream, in which the cold consumer or the or Evaporator of the refrigerant flowing refrigerant is relaxed. That so expanded refrigerant is evaporated in the evaporators of the refrigerant consumers and thus cools the corresponding refrigeration furniture and rooms.  

The refrigerant evaporated in this way is then passed through a suction line Compressor unit supplied. These compressor units can have one or more stages be trained. The individual compressor stages usually have several in parallel switched compressor. These compress and convey the refrigerant a riser in turn to the previously mentioned condenser. While the Compressor unit normally in one, in the basement one Is located in the supermarket, the condenser is on the roof of the supermarket.

If there are so-called normal and so-called freezing points within a market, these are supplied by means of separate refrigerant circuits; so this means that a like refrigeration system described in DE-PS 39 28 430 is present at least twice.

The one required for cooling the normal and deep freeze points of a market However, investment, operating costs and installation costs are considerable.

The object of the present invention is to provide a refrigeration system of the generic type specify the lower investment and operating costs, as well as installation effort required.

To solve this problem, a refrigeration system is proposed, which is thereby distinguishes that the pressure lines from the compressor units via a Defrost line, which is preferably designed to be shut off, with the suction line Compressor unit of the freezer circuit are connected.

The refrigeration system according to the invention and further refinements of the same are explained in more detail with reference to the embodiment shown in FIGS. 1 and 2.

The refrigeration system shown in FIG. 1 has only one condenser or condenser V. According to an advantageous embodiment of the invention, this can be followed by a collecting container S1. The liquid refrigerant from the condenser V is fed via line 1 to the storage tank S1. From this, the refrigerant passes through the liquid lines 2 as well as 3 and 4 to the cold consumers of the normal cooling and freezing cycle. The consumers V1 and V2 shown in FIG. 1 stand for any number of consumers of the normal cooling circuit, while the consumers V3 and V4 shown in FIG. 1 stand for any number of consumers of the deep-freeze circuit.

An expansion valve a to d is connected upstream of each cooling consumer V1 to V4 or assigned in which the in the cold consumer or the evaporator or evaporators the refrigerant flowing refrigerant is relaxed. The so relaxed Refrigerant is evaporated in the evaporators of the refrigerant consumers V1 to V4 and thus cools the corresponding refrigeration furniture and rooms for normal and deep-freeze circuit.

The evaporated in the refrigeration consumers V1 and V2 of the normal cooling circuit medium is fed via a suction line 5 of the compressor unit of the normal cooling circuit. According to a further advantageous embodiment of the refrigeration system according to the invention, this is connected upstream of a suction collecting container S2. As a rule, the compressor unit of the normal cooling circuit has only one stage and has several, preferably three, compressors connected in parallel; For the sake of clarity, only two compressors C1 and C2 connected in parallel are shown in the figure. These suck in via the lines 6 and 7 refrigerant from the suction container S2 and promote the compressed refrigerant via the pressure line 8 to a desuperheater E. After passing through the desuperheater E, the refrigerant is again fed via line 9 to the condenser or condenser V already described .

For the sake of clarity, FIG. 1 does not show the required further cooling or subcooling of the refrigerant in the liquid line 4 , which can take place, for example, in indirect heat exchange with the refrigerant conveyed in line 10 .

It is advantageous if - according to a further advantageous embodiment of the refrigeration system according to the invention - the device for subcooling the refrigerant in the liquid line 4 of the freezer circuit is arranged as close as possible to the refrigeration consumers V3 and V4 of the freezer circuit. By means of this configuration of the refrigeration system according to the invention, the loss of performance due to heat absorption from the environment can be minimized.

The refrigerant supplied to the consumers V3 and V4 of the deep-freeze circuit via the liquid line 4 is fed via the suction line 10 to the compressor unit of the deep-freeze circuit. Again, according to a further advantageous embodiment of the refrigeration system according to the invention, the compressor unit of the freezer circuit can be preceded by a low-pressure suction tank S3.

The compressor unit of the deep-freeze circuit is preferably designed at least in two stages, with each compressor stage again being represented by two compressors C3 and C5 and C4 and C6 connected in parallel for the sake of clarity. The 'compressors C3 and C5 of the first compressor stage suck in gaseous refrigerant from the low-pressure suction tank S3 via lines 11 and 12 and convey the refrigerant compressed to an intermediate pressure via line 13 into the intermediate-pressure suction tank S4. From this, the compressors C4 and C6 of the second compressor stage suck in refrigerant via the lines 14 and 15 and then convey the compressed refrigerant via the pressure line 16 likewise before the desuperheater E already mentioned in the line 9 .

Of course - in contrast to the illustration in FIG. 1 - the compressor unit of the freezer circuit can also be designed in three or more stages; in this case, separate suction collecting containers could be connected upstream of the individual compressor stages. It should be pointed out that it is of course also possible to dispense with such suction collecting containers.

The refrigeration system according to the invention has one compared to the known solutions lower investment and operating costs as well as installation costs. she also enables - as will be explained - further constructive designs and procedures that are difficult or impossible with the previous solutions are to be realized.

Refrigeration system or the evaporators arranged in the refrigeration consumers must be in are defrosted at regular intervals because of frosting or icing on the Evaporators lead to a reduction in the efficiency of the evaporators.

One way of defrosting is so-called electrical defrosting. With this the Evaporator defrosted by means of heaters arranged on and / or in them. This  However, the procedure leads to an undesirable increase in electrical consumption Energy.

As an alternative to the electrical defrost described, the so-called compressed gas Defrost on. In this, the condenser is located between the gas space switched collecting container and each evaporator or each evaporator group Compressed gas lines laid and over this gaseous refrigerant, which is a tempera has between 35 ° C and 45 ° C, from the collecting tank to the evaporators or evaporator groups supplied. The installation effort for this compressed gas-Ab Thawing is comparatively high, however, because for every evaporator or evaporator fergruppe a separate compressed gas line must be provided.

In the case of refrigerated cabinets in particular, the work involved is very high because the necessary valve stations are usually arranged on the underside of the refrigerator must be, and these are difficult to access, especially when servicing.

Compared to electrical defrosting, this requires pressurized gas defrost in terms of Pipeline network an additional effort. In addition to the advantage of operating costs Kung is the main advantage of compressed gas defrosting in the lower heat load of goods to see. The temperature of the goods during and immediately after Defrosting is of increasing importance, so that the pressure Gas defrosting in the future may be the only way to meet the requirements of the legislator with regard to the requirement "product temperature" Afford.

In the refrigeration system according to the invention, the pressure lines 8 and 16 from the compressor units C1 / C2 and C3 / C4 / C5 / C6 via a defrost line 30 , the preference as z. B. is formed by a valve e, lockable, connected to the suction line 10 of the compressor unit C3 / C4 / C5 / C6 of the freezer circuit.

During the defrosting phase, the supply of refrigerant from the compressor unit C1 / C2 of the normal cooling circuit to the condenser V is now interrupted, the compressor unit C3 / C4 / C5 / C6 of the freezer circuit is switched off and the heated refrigerant via the opened defrosting line 30 of the suction line 10 and above these are fed to the refrigeration consumers V3 and V4 of the freezer circuit. The flow of the refrigerant during the defrost phase is shown by the large, framed arrows.

The refrigerant flowing through the refrigeration consumers V3 and V4 of the deep-freeze circuit or their evaporators is fed via lines 3 and 4 to the refrigeration consumers V1 and V2 of the normal cooling circuit and then conveyed via the suction line 5 to the compressor unit C1 / C2 of the normal cooling circuit. During defrosting, compressor unit C1 / C2 thus works as a heat pump. As soon as the evaporators of the refrigeration consumers V3 and V4 of the deep-freeze circuit are completely defrosted, the defrost line 30 is closed again by closing the valve e, the compressor unit C3 / C4 / C5 / C6 of the deep-freeze circuit is switched on and switched to cooling mode. The refrigerant now flows again via the pressure lines 8 and 16 and the common pressure line 9 from the compressor units C1 / C2 and C3 / C4 / C5 / C6 to the condenser V.

At the beginning of the defrosting phase, it makes sense if warm refrigerant flows from the storage container S1 via the liquid lines 2 and 4 to the evaporators of the cold consumers V3 and V4 of the freezer circuit. As a result, the evaporators to be defrosted are accumulated with liquid refrigerant, which means that the evaporators to be defrosted are already heating up. As soon as the refrigerant supplied to the evaporators of the refrigeration consumers V3 and V4 by the compressor unit C1 / C2 of the normal cooling circuit via the defrost line 30 flows into the evaporators, the refrigerant previously accumulated therein is displaced. After the pressure has been equalized between the condenser V or the collecting tank S1 and the pressure lines, only more refrigerant is then conveyed into the evaporators of the refrigeration consumers V3 and V4 by means of the compressor unit C1 / C2 via the defrost line 30 and the suction line 10 .

Because different sized evaporators are arranged in different refrigeration units are and / or the evaporators have different degrees of icing this does not simultaneously meet the required defrost end temperature of, for example, 15 ° C.

Another advantageous embodiment of the refrigeration system according to the invention is therefore characterized in that at least one of the refrigeration consumers V3 and V4 of Freezer circuit or the evaporators of these refrigeration consumers a direct control  solenoid valve that connects to the corresponding expansion valve of the refrigeration consumer is arranged in parallel, is connected upstream.

This embodiment of the refrigeration system according to the invention will be explained in more detail below with reference to FIG. 2, which shows the immediate area of the cold consumer V3 shown in FIG. 1; this is the area encircled by a broken line in FIG. 1.

It shows the consumer V3 or its evaporator, the liquid line 4 and suction line 10 shown in FIG. 1 and the expansion valve c assigned to the evaporator of the consumer V3, via which the refrigerant is injected into the evaporator in cooling operation. In cooling mode, refrigerant thus flows from the liquid line 4 via line 40 to the expansion valve c and from there via line 42 into the evaporator of the refrigeration consumer V3.

According to the invention, a directly controlled solenoid valve c 'is now provided in parallel with the expansion valve c in a bypass line 41 . During the defrosting process, the refrigerant flows through the defrosting line 30 (not shown in FIG. 2) and the suction line 10 into the evaporator of the refrigeration consumer V3 and then sends via lines 42 and 41 into the liquid line 4th If the preset defrost end temperature is reached in one of the evaporators - which can be registered, for example, by means of a corresponding defrost probe -, the solenoid valve c 'is closed.

The direct-controlled solenoid valve c 'acts as a check valve when the coil is de-energized with an opening pressure of approx. 1.5 bar, which is due to the valve. By the Closing a solenoid valve at the appropriate end of defrost temperature Defrosting power shifted to those evaporators that still have the final defrost temperature have not reached. An evaporator that has already been defrosted is therefore not unnecessary wise refrigerant, but only those evaporators that have not yet are completely defrosted. This means that they reach the specified one in a shorter time End of defrost temperature.

As soon as all evaporators have reached their end of defrost and their solenoid valves are closed, a pressure difference builds up between the evaporators and the liquid line 4 . As soon as this pressure difference is greater than 1.5 bar, the solenoid valves are flowed through in reverse and the refrigerant liquid in the evaporators is pressed into the liquid line 4 .

After the defrost phase has ended, the evaporators are simultaneously operated via the Ver aspirated from the normal and freezer circuits. Once the vaporizer pressure drops lower than the temperature of T (hermostatic) E (xpansions) V (entile) - Corresponds to the sensor, refrigerant is automatically injected into the evaporator. The evaporators of the freezer circuit are cooled in about 5 minutes. In addition to the performance of the compressors of the freezer circuit, this also includes Performance of the compressors of the normal cooling circuit is available because of the cooling points or cold consumers of the normal cooling circuit during defrosting of the ver Steamer of refrigeration consumers V3 and V4 of the freezer circuit on forced cooling are switched and thereby reach temperatures below the target value. For the entire freezer area can therefore have a significantly shorter defrost time compared to electrical defrost can be achieved.

The implementation of the defrosting process described requires the fiction modern refrigeration system compared to a refrigeration system in which an electrical defrost is carried out, no additional work on pipes and fittings. There for Defrosting the evaporators of the refrigeration consumers V3 and V4 of the freezer circuit no power has to be switched on - as is the case, for example, in In the case of an electrical defrost - the only thing that is cooling is in the energy balance after the defrost phase. The defrosting performance is purer in itself Heat pump operation from the normal cooling composite set or the compressor unit C1 / C2.

Another advantage is that the pipe insulation is poorly ventilated Do not wet the floor ducts and / or under the refrigeration cabinets as they are forced to be heated every 48 hours during the defrosting process.

Furthermore, the goods are exposed to a lower temperature load, since only more three times a week - for example on Tuesdays, Thursdays and Saturdays - must be defrosted. With separate refrigerant circuits and one cold gas  Thawing is not possible because after 48 hours of cooling in the freezer circuit no defrosting power would be available for the first defrosting group.

During the night or closing times, the refrigeration system is operated in a so-called Energy-saving operation driven. Under the term energy-saving operation here to understand those operating conditions in which the on the refrigeration units Night blinds shut down or above, the lights are off, the Cold room doors can no longer be opened and therefore no flow of goods - i.e. the Removal or delivery of goods from or into the refrigeration units or cold rooms - takes place.

The cooling requirement during these times is often so low that it is in the compressor Unit of the normal cooling circuit comes to a so-called pump-down circuit. Under the term "pump-down circuit" is the suction of the evaporator of the refrigeration need to understand. This has the consequence that on the one hand cooling points with a low cooling demand no longer reach the target temperatures and secondly the Switching frequency of the compressors of the normal cooling circuit unnecessary and undesirable becomes high because the increased switching frequency of these compressors leads to a reduction whose lifespan leads.

This is a further advantageous embodiment of the refrigeration system according to the invention characterized in that the freezer circuit is an at least two-stage compressor unit C3 / C4 / C5 / C6 and the suction side of the normal cooling circuit with the or one of the intermediate pressure sides of the freezer circuit is operatively connected. Provided the compressor stages C1 and C2 of the normal cooling circuit and at least one Compressor stages C4 and C6 of the freezer circuit, which is not the first Compressor stages C3 and C5 act, suction collecting tanks S2 and S4 upstream are preferably in operative connection with each other.

This configuration of the refrigeration system according to the invention now enables others advantageous procedures, as they do not or only with the known refrigeration systems can be realized with a corresponding effort.

An active connection between the suction side of the normal cooling circuit and the or one of the intermediate pressure sides of the deep-freeze circuit or between the suction tank of the normal cooling circuit and the or one of the intermediate pressure-suction collecting container of the deep-freeze circuit can be realized according to an advantageous embodiment of the refrigeration system according to the invention via at least one connecting line 20 .

It is conceivable - according to an alternative embodiment of the refrigeration system according to the invention - that the function of the suction collecting container of the normal cooling circuit and one or of the intermediate pressure suction collecting container of the deep-freezing circuit is realized in a common suction collecting container. This embodiment of the refrigeration system according to the invention is not shown in FIG. 1.

By means of this configuration of the refrigeration system according to the invention, it is possible that the compressors of normal cooling during night and / or closing times circuit can be switched off.

Since in the case of a two-stage compressor unit in the freezer circuit, the intermediate pressure depending on the condensing temperature during the energy saving drive is always lower than the evaporation temperature of the normal cooling circuit, is the required low load of the normal cooling area by the second compression level - the so-called high-pressure compressor stage - of the freezer circuit. The consequence of this is that all refrigeration consumers in the normal cooling circuit have low cooling requirements also reach the required target temperatures can, if all compressors of the normal cooling circuit are switched off. To a Switching on the compressors of the normal cooling circuit can thus be dispensed with; the switching frequency of the compressors of the normal cooling circuit is reduced significantly, which increases the life expectancy of these compressors. Since during the Energy-saving operation the work of the compressors of the normal cooling circuit Compacting the deep freeze cycle is taken over, their improves Workload.

A further embodiment of the refrigerating plant according to the invention is characterized terized in that the intake collecting S2 equal to the lead of the normal refrigeration circuit and the intermediate pressure intake collecting container S4 of the freezing circuit is provided connecting Ölaus 21st

The oil levels of the interconnected suction collectors S2 and S4 can be compensated via this oil compensation line 21 . The effort for such an oil line is low.

The refrigeration system according to the invention thus offers a variety of advantages the known refrigeration systems, especially with regard to the defrosting of the evaporator fer as well as energy saving. It enables this with a reduced installa effort and the associated lower investment costs. Since both the Energy consumption and maintenance costs are reduced also the operating costs. Furthermore, with the described defrosting process Compliance with future legal requirements possible.

It should be noted that the invention could be implemented not only in a refrigeration system with an at least two-stage compressor unit of the freezer circuit - as shown in FIG. 1 - but also with a one-stage compressor unit.

Claims (13)

1.Refrigeration system for cooling at least one cooling consumer by means of a normal cooling circuit and for cooling at least one cooling consumer by means of a freezing circuit, each of the circuits having a compressor unit, only one condenser being provided and the pressure lines from the compressor units being brought together in front of the condenser, characterized that the pressure lines ( 8 , 16 ) from the compressor units (C1 / C2, C3 / C4 / C5 / C6) via a defrost line ( 30 ) with the suction line ( 10 ) of the compressor unit (C3 / C4 / C5 / C6) of the freezer circuit are connected. 2. Refrigeration system according to claim 1, characterized in that the defrost line ( 30 ) can be shut off (e). 3. Refrigeration system according to claim 1 or 2, characterized in that the condenser siger (V) is only connected to a collection container (S1). 4. Refrigeration system according to one of the preceding claims, characterized in that only one liquid line ( 2 ) is arranged between the condenser (u) or the collecting container (S1) and the liquid lines ( 3 , 4 ) of the normal and freezer circuits. 5. Refrigeration system according to one of the preceding claims, characterized in that the device for supercooling the refrigerant in the liquid line ( 4 ) of the freezer circuit spatially as close as possible to the refrigeration consumers (V3, V4) of the freezer circuit is arranged. 6. Refrigeration system according to one of the preceding claims, characterized net that at least one of the refrigeration consumers (V3, V4) of the freezer circuit a directly controlled solenoid valve (c ') the corresponding expansion valve (c) of the refrigeration consumer (V3, V4) is arranged in parallel. 7. Refrigeration system according to one of the preceding claims, characterized net that the condenser (V) has a desuperheater (E) upstream.   8. Refrigeration system according to claim 7, characterized in that the pressure lines ( 8 , 16 ) from the compressor units (C1 / C2, C3 / C4 / C5 / C6) are brought together before the desuperheater (E). 9. Refrigeration system according to one of the preceding claims, characterized net that the freezer cycle an at least two-stage compressor unit (C5 / C4 / C5 / C6) and the suction side of the normal cooling circuit with the or one of the intermediate pressure sides of the freezer circuit is operatively connected. 10. Refrigeration system according to one of the preceding claims, characterized net that at least one compressor stage (C1 / C2) of the normal cooling circuit and a compressor stage (C4 / C6) of the freezer circuit, which is not the first compressor stage (C3 / C5), suction collecting container (S2, S4) preformed are tet and are in operative connection. 11. Refrigeration system according to claim 9 or 10, characterized in that the operative connection is implemented via at least one connecting line ( 20 ). 12. Refrigeration system according to claim 11, characterized in that one of the suction collecting container (S2) of the normal cooling circuit and one or one of the intermediate pressure suction collecting container (S4) of the freezer circuit connecting oil compensation line ( 21 ) is provided. 13. Refrigeration system according to claim 10, characterized in that the function of Suction collecting container (S2) of the normal cooling circuit and the intermediate pressure Suction collection container (S4) of the freezer circuit in a suction collection container is realized.