WO2021084563A1

WO2021084563A1 - Step chiller assembly and water loop refrigeration system including the same

Info

Publication number: WO2021084563A1
Application number: PCT/IT2019/000087
Authority: WO
Inventors: Luigi Nalini; Dimitry RENESTO
Original assignee: Carel Industries S.p.A.
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2021-05-06

Abstract

Step chiller assembly (10) for a refrigeration system (100) with water loop (101) which comprises: - a refrigeration unit (11) having a compressor (12) and an evaporator member (13) configured to exchange heat between a refrigerating fluid and a fluid flowing in a water side (13a) thereof; - an actuating device (16), which is connected to the compressor (12) in order to control the operation and operating safety thereof; - a general control system (18) connected to the refrigeration unit (11) and able to be connected to temperature and pressure transducers and/or sensors; where the general control system (18) is configured and/or programmed to operate the step chiller assembly (10), in particular to activate it, to regulate the refrigerating capacity thereof and to optimize the operation thereof depending on data received from the sensors and/or transducers which, during operation, are incorporated in the step chiller assembly (10) and/or in the refrigeration system (100), in order to detect and monitor the operation thereof. - a pumping unit (17) connected to the water side (13a) of the evaporator member (13) so as to force water to circulate across the water side (13a) and from/into a water loop (101) of a refrigeration system (100) to which the step chiller assembly (10) is connected when in operation; where the step chiller assembly (10) is configured to form a single manufactured unit available independently of a refrigeration system (100) so as to be integrated therein or separate therefrom.

Description

STEP CHILLER ASSEMBLY AND WATER LOOP REFRIGERATION SYSTEM

INCLUDING THE SAME

The present invention relates to a refrigeration system mainly for food storage with a water cooling circuit.

In particular, the present invention relates to the use of one (or more) auxiliary chillers - which will be referred to below as "step chillers" - forming part of a refrigeration system in which a cooling water flow which is kept circulating in a hydraulic circuit absorbs the condensation heat of the refrigeration devices which form the said system and then dissipate it into the atmosphere by means of a fan-assisted radiator.

Alternatively, or in other circumstances where it would be convenient, said heat is transferred to one or more specially provided chillers.

Nowadays it is known that supermarkets are establishments which use large amounts of electrical energy in the commercial sector.

A supermarket may on average use each year even more than one million kWh. For the most part, said energy consumption may be attributed to the refrigeration of perishable goods which are stored in what, below, are called peripheral units or in cold-storage rooms or in display units such as counters, display windows or display cases of various types, which may occupy even up to half of the surface area of the sales outlet.

Generally conventional refrigeration systems use a so-called "multiplexed" system where the refrigerated fluid is distributed and made to evaporate inside heat exchangers (evaporators) installed in the peripheral units, keeping inside the latter the desired temperature for storage of the products. A centralized compression group, called a "compressor rack", draws off the vapour resulting from the evaporation of the refrigerant in the various user appliances by means of a compression unit which increases the pressure thereof and sends it to the condenser where the liquid is converted back into the liquid state and, finally, distributed again to the peripheral units, repeating the cycle.

The compression group is installed in a special room generally provided in premises inside the sales outlet or on the roof thereof.

The nature of the foodstuffs available in a supermarket is such that there must be at least two levels of storage temperature inside the peripheral units: medium temperature "MT" (used to store products in the temperature range of between about +1 °C and 3°C) for fresh food and low temperature "LT" (used to store products in the temperature range of between about -20°C and -28°C) for frozen or deep-frozen foods. Different temperatures may be required for specific cases.

For this reason the compression groups in supermarkets usually have two rows of compressors with saturated intake temperatures which differ very greatly from each other; in fact, on average the compressor racks which serve the MT peripheral units and those which serve the LT peripheral units draw off the refrigeration fluid at a saturated temperature of between about -10°C and -30°C to -35°C or the like.

Obviously this type of system has a network of pipes for conveying the refrigerant which is often very complex.

While the same condensed liquid from the compressor racks may be distributed to both categories of user appliances, namely MT peripheral units and LT peripheral units, the suction pipes are necessarily different for the MT user appliances and LT user appliances.

Owing to the distance between the compression units/condensers and the peripheral user appliances and the consequent pipe length required, huge quantities of refrigerant, equivalent in some cases to more than one thousand kilograms, are required.

The length of the pipe path for joining together the peripheral user appliances and the centralized group, comprising the compression units and condensers, also results in a significant loss of head which results in a major reduction in the overall efficiency of the system.

In addition, such a traditional layout - composed of multiple pipe sections and unions welded together - means that there is significant risk of leaks which, statistically speaking, varies on average between 10% and 25% of the total amount of refrigerant. In this context, nowadays, in order to reduce both the annual energy consumption and, at the same time, the total equivalent warming impact (TEWI) so-called "water loop self-contained systems" (WLSC) are being increasingly more frequently used.

In this type of system each peripheral unit (or small groups of peripheral units) is provided with its own independent refrigeration assembly provided with a compressor preferably of the variable-speed type (normally with an inverter- driven brushless motor BLDC), water condenser and expansion valve; this assembly, which is connected to the evaporator, ensures that each unit is self- sufficient and independent of the other units. Each of these peripheral units is connected to a closed hydraulic circuit containing a liquid (generally water with anti-freeze) and is fed by it such that its condenser is cooled by means of heat exchange with the said liquid which absorbs the condensation heat of the various peripheral units connected and disperses it through a dissipator which consists of an exchanger, situated outside of the supermarket.

According to solutions aimed at optimizing the energy consumption, the heat may not be entirely disposed of externally, but partially recovered for other uses, for example in order to obtain hot water, obviously with complications in terms of circuit design. The dissipator which is most commonly employed is of the type which is generally referred to as a "dry cooler" consisting of a heat exchanger with forced convection by means of fans.

Figures 1-4 show examples of embodiments of conventional systems.

In particular, Figure 1 shows the simplified configuration of a conventional WLSC system, generally indicated here by means of the reference number 1000, with a water loop circuit 1001 which comprises:

- a pump 1002 which performs circulation of the water; for safety reasons and to ensure operational continuity, a second pump 1002a (for simpler illustration not shown in the attached figures) may be provided in parallel with the first pump; said pump is provided with shut-off members so as to be automatically activated in the event of malfunctioning of the first pump which may thus be replaced without interrupting operation of the system;

- a plurality of peripheral units, or user appliances, which are fed in parallel and comprise both MT peripheral units 1003, i.e. medium temperature units, and LT peripheral units 1004, i.e. low temperature units. - a dry cooler (external fan-assisted radiator) 1005 having the function of dissipating the condensation heat of the user appliances into the atmosphere;

- two motorized valves 1007 coupled together or, alternatively, a three-way mixer valve, not shown, these being driven by a temperature control system having the function of bypassing, if necessary, part of the water flow so as to prevent the output temperature thereof from being lower than a pre-set minimum level should the external atmospheric temperature be too low. Obviously the temperature of the water cooled by the dry cooler is closely related to the temperature of the external environment where, obviously, if the latter increases, the temperature of the water supplying the refrigeration assemblies of the peripheral units 1003 and 1004 increases correspondingly. The physical parameters which influence mainly the refrigeration capacity and the efficiency of a compressor are the saturated condensation pressure and the saturated evaporation pressure which, in the case of food storage, is not subject to major fluctuations. The ratio between saturated condensation pressure and saturated evaporation pressure constitutes the compression ratio.

It is known that each increase by 1°C of the saturated condensation temperature, here due to the increase of the external temperature, causes a decrease both in the refrigeration efficiency and in the energetic efficiency of the compressor by about 2.5%-3%.

In addition, there is a limit value of the compression ratio declared by the manufacturers of the compressors beyond which serious damage may occur.

In particular, it should be noted that, if the refrigeration fluid used in the circuits of the peripheral units is carbon dioxide, CO2 and should the temperature of the cooling water be higher than about 25°C, the operating mode would switch to a transcritical cycle with gradually worsening energy efficiency levels which may be even unsuitable for operation of the low temperature counters owing to both the pressures and the temperatures reached at the compressor outlets. If, on the other hand, the cooling water were to be kept continuously below that threshold or at an even colder temperature, the units would operate constantly in subcritical mode with a lower compression ratio and decidedly better and safer results.

For this reason, in particular, but not only in the case of low temperature counters, often it is useful, if not necessary, to use a chiller in order to allow the condensers of the peripheral units to be supplied throughout the year with water within the maximum limits established depending on the operating mode, the type of compressor and the type of refrigerant.

Figure 2 shows a conventional variant of the WLSC system according to Figure 1 comprising a chiller 1006 which is able to absorb the condensation heat of the peripheral units 1003 and 1004 in the maximum load conditions; with this arrangement, by means of suitable operation of the motorized valves 1007 (set to the closed position) and 1007a (set to the open position), the water flow is deviated towards the chiller, excluding the dry cooler if the temperature of the water cooled by the latter exceeds a pre-set level.

In this way, by controlling the temperature of the water throughout the year, the saturated delivery temperature of the compressors of the peripheral units 1003 and 1004, and therefore the compression ratio, may in any case be limited.

In given conditions it may be convenient to control the water for cooling the condensers of only the LT low temperature peripheral units 1004 where there is the greatest compression ratio.

In this case, as schematically shown in Figure 3, in a conventional manner, the condensers of the MT peripheral units 1003 are connected to the cooled water loop by the dry cooler, while the condensers of the LT peripheral units 1004 are passed through by refrigerated water produced by a special chiller 1010 of the water-water type, also called step chiller.

The step chiller 1010 has a condenser 1010a which is cooled by the water treated by the rad cooler 1005, in parallel with the MT peripheral units 1003, and, throughout the year, produces in its evaporator 1010b a refrigerating power suitable for refrigerating water which is made to circulate, via a special loop circuit 1009, inside the condensers of the LT peripheral units 1004 by means of a special pump 1008; the temperature of this water flow is suitably regulated so as to keep the compression ratio of the LT peripheral units 1004 at an optimum level. An example - still in use today - of a system provided with water-water step chiller is disclosed in the document entitled "Annual energy analysis of a water- loop self-contained refrigeration plant and comparison with multiplex systems in supermarkets" in the name of G. Bagarella, R. Lazzarin and M. Noro, published in the magazine International Journal of Refrigeration No. 45, dated 2014, on pages 55-63.

This document contains a case study of a supermarket built in 2012 in the town of Castiglione dei Pepoli, on the outskirts of Bologna (Italy), where use of a WLSC system, compared with a multiplexed system, for the same surrounding conditions, resulted in a reduction in electrical energy consumption by 12.6%, whereby this figure, with suitable measures based on experience, may be significantly increased.

A further valid conventional alternative solution, shown in Figure 4, consists in division of the system into two completely separate circuits.

In this case, liquid, generally water with anti-freeze, is recycled in a first loop 1001 by means of the pump 1002 between the condensers of the MT peripheral units 1003 and the dry cooler 1005 which dissipates the heat into the atmosphere.

A second loop 1009, completely separate from the first loop 1001, recirculates by means of the pump 1008 the liquid, which is generally water with anti-freeze, between a chiller 1006, which is generally air-cooled and suitably designed in terms of dimensions so as to keep the temperature of the liquid - and consequently the condensation pressure of the LT peripheral units 1004 - at the optimum value for the whole of the year. It is pointed out that the chiller 1006 could coincide with an already existing chiller and be used to air-condition and/or cool the building which houses the system 1000.

It should be pointed out, however, when the outside temperature falls below sufficiently low values (it should be remembered that in temperate climates the outside temperature is lower than 15°C for more than 50% of the hours in a year) the temperature of the water output from the dry cooler 1005 is already suitable for obtaining a suitable compression ratio in both the MT and LT peripheral units 1003 and 1004.

In these circumstances it would become energetically convenient to use for cooling the peripheral units only the water from the dry cooler 1005, deactivating and excluding from the hydraulic circuit the step chiller 1006 in the most convenient manner without complicating the entire system. These advanced systems, with step chillers, have a greater complexity compared to the simpler WLSC systems.

The problem underlying the present invention is that of improving the constructional simplicity of conventional systems. The task of the present invention is therefore to propose a solution to this problem, by providing a step chiller assembly and a water loop refrigeration system including the same, which may maintain a satisfactory operating efficiency also in high ambient temperature conditions, while at the same time being suitable for operation in a wide range of refrigeration capacities according to the load required depending on the seasons and the number of peripheral units in operation.

In connection with this task it is an object of the present invention to propose a step chiller assembly which is substantially easy to install and regulate and which at the same time may be easily excluded from the hydraulic circuit as required.

In connection with this task it is an object of the invention to provide a step chiller assembly which can be easily connected to a system - both pre-existing and in the course of installation - and which may be easily set up for automatic operation. This task, as well as these and other objects which will appear more clearly below, are achieved by a step chiller assembly and water loop refrigeration system including the same according to the attached independent claims. Detailed characteristic features of a step chiller assembly and a refrigeration system with water loop refrigeration system including the same, according to the invention, are described in the dependent claims. Further characteristic features and advantages of the invention will emerge more clearly from the description of a preferred, but not exclusive embodiment of a step chiller assembly and a water loop refrigeration system including the same, according to the invention, illustrated by way of a non-limiting example in the attached sets of drawings in which:

- Figures 1-4 show a simplified diagram of systems according to the prior art;

- Figure 5 shows a simplified diagram of a step chiller assembly according to the invention;

- Figures 6, 7 and 10 show simplified diagrams of variants of the step chiller assembly according to Figure 5;

- Figures 8, 9, 11, 12 show simplified diagrams of refrigeration assemblies according to the present invention.

With particular reference to the cited Figures 5-12, 10 therefore denotes overall a step chiller assembly for a refrigeration system 100 with a water loop 101, which, according to the present invention, comprises:

- a refrigeration unit 11 having at least one compressor 12, or a plurality of compressors 12 arranged in parallel, preferably of the variable speed type, an evaporator member 13 configured to exchange heat between a refrigerating fluid and water flowing in a water-side 13a thereof;

- a pumping unit 17, preferably with a variable speed, for adapting the flowrate to the particular operational requirements, which is connected to the water side 13a of the evaporator member 13, so as to force water to circulate across the water side 13a and from/into a branch of a water loop 101 of a refrigeration system 100 to which it is connected during operation; - an actuating device 16, which is connected to the compressor 12 in order to control the operation and operating safety thereof;

- a general control system 18 which is connected to the refrigeration unit 11 and can be connected to sensors designed to monitor the operation of the said step chiller assembly 10 and the system 100 which, during operation, incorporates it, in a manner conventional per se and not further described.

The general control system 18 is configured and/or programmed to control operation of the step chiller assembly 19 and, in particular, to activate it when required, in order to adjust the refrigerating capacity thereof and optimize operation thereof by employing temperature and pressure sensors and/or transducers which, in a manner conventional per se, may be incorporated in the step chiller assembly 10 and/or in the system 100, in order to detect and monitor the operation of the latter, in a manner conventional per se.

The actuating device 16 may comprise an inverter, in the case of a variable- speed compressor 12, or an ON/OFF actuating member in the case of a fixed- speed compressor 12.

Moreover, the actuating device 16 is configured to act in such a way as to drive the compressor 12 in order to supply the water flow circulating in the water side 13a of the evaporator member 13 with the refrigerating power necessary for compensating for the thermal load emitted by the peripheral units associated with the step chiller assembly 10.

In accordance with the present invention the step chiller assembly 10 has the particular feature of being configured so as to form a single manufactured unit which is available separately from a refrigeration system 100 so that it may be incorporated in or separated from the latter in a simple and easy manner. In this way, the chiller assembly 10 may be easily inserted in already existing refrigeration systems 100 by simply connecting it hydraulically to the water loop 101 for example by means of shut-off cocks 19, shown for example in Figure 5, which also allow easy disconnection thereof in the event of replacement and/or repair.

The step chiller assembly 10 may comprise first hydraulic connectors 24a which are hydraulically connected to the water side 13a of the evaporator member 13 and are configured to connect the latter to a water loop 101 of a refrigeration system 100.

Moreover the step chiller assembly 10, in order to form a single manufactured unit, may comprise a frame or casing to which the following are fixed, directly or indirectly, for example because they are fixed to other components of the step chiller assembly 10:

- a refrigeration unit 11 ,

- the actuating device 16,

- the general control system 18,

- the pumping unit 17 and

- the first hydraulic connectors 24a.

In this way, in fact, the chiller assembly 10 may be easily installed, also incorporating it in already existing systems, by simply connecting it to the water loop 101 by means of the first hydraulic connectors.

The chiller assembly 10, during operation, may thus start operating if the temperature circulating in the water loop is too high to allow efficient operation of the refrigeration system 100 as a whole, as described more fully below.

This is particularly advantageous for refrigeration systems which comprise refrigerating machines which use as refrigerating fluid carbon dioxide, CO2; in fact, in particular during the summer period or, in any case, in too high temperatures of the water in the water loop, the exchange temperature at the condensers/gas coolers of these refrigerating machines tends to be too high for ensuring efficient operation thereof and, in particular, tends to cause them to operate in transcritical and not subcritical conditions.

In the attached sets of drawings, in order to facilitate understanding thereof, the components of the step chiller assembly 10 may be shown not grouped together, although this particular graphical illustration must not be regarded as meaning that the said parts are separated.

The refrigeration unit 11 may comprise a condenser member 14, also called a gas cooler, configured to perform heat exchange between the refrigeration fluid and water flowing in a water side 14a of the condenser member 14, where the water side 14a is configured to be connected to a water loop 101 of a refrigeration system 100.

The step chiller assembly 10 may also comprise second hydraulic connectors 24a which are connected hydraulically to the water side 14a of the condenser member 14 and are configured to connect the latter to a water loop 101 of a refrigeration system 100, in order to dissipate heat from said refrigerating fluid to the water flowing in the water side 14a of the condenser member 14.

Moreover, the refrigeration unit 11 may comprise an expansion valve 15, which is preferably electronic driven so as to allow the correct metering of refrigerant injected into the evaporator member 13.

As shown by way of a non-limiting example in Figure 7, the step chiller assembly 10 may also comprise a deviation valve unit 20 connected: - via its first flow path AB to a first one of the second hydraulic connectors 24b which, when the step chiller assembly 10 is connected to a water loop 101, will be connected to the latter so as to receive fluid therefrom;

- via its flow path A, to a first one of the first hydraulic connectors 24a which, when the step chiller assembly 10 is connected to a water loop 101, will be connected thereto so as to introduce refrigerated fluid, from the water side 13a of the evaporator member 13, into the water loop 101 and, specifically, into a low temperature branch 109 thereof;

- via its flow path B, to the water side 14a of the condenser member 14. The deviation valve unit 20 can be selectively operated:

- in a mode AB-A where the flow path AB is connected exclusively to the flow path A, so as to cause bypassing of the step chiller assembly 10 with respect to the hydraulic connectors 24a and 24b which, during operation, connect it to the water loop 101; - in a mode AB-B where the flow path AB is connected exclusively to the flow path B, so as to connect the first of the second hydraulic connectors 24b to the water side 14a of the condenser member 14 so that, during operation, the latter is cooled by the fluid coming from the water loop 101 , by means of the first one of the second hydraulic connectors 24b. The deviation valve unit 20 may comprise a three-way valve or two two-way valves which are coupled together.

Moreover, the deviation valve unit 20 may be connected to the general control system 18 so as to be operated by it.

The general control system 18 may be configured or programmed to operate the deviation valve unit 20 selectively: - in the mode AB-A if, during operation, the general control system 18 receives a reading of the temperature of the fluid flowing in the water loop 101 which is lower than a fixed threshold (or lower than or the same as it);

- in the mode AB-B if, during operation, the general control system 18 receives the reading of a temperature which is higher than or the same as the fixed threshold (or, respectively, higher than it).

With particular reference to Figure 5, the step chiller assembly 10 may comprise shut-off cocks 19, which are arranged upstream or downstream of the hydraulic connectors 24a and/or 24b, so as to connect and disconnect hydraulically said step chiller assembly 10 from a water loop 101 of a refrigeration system.

Clearly, the shut-off cocks 19 may be incorporated in the water loop 101, instead of in the chiller group 10, depending on the particular implementation requirements of the present invention.

Similarly, as shown by way of a non-limiting example in Figure 5, the deviation valve unit 20 may be incorporated in the water loop 101 , instead of in the chiller assembly 10, depending on the particular implementation requirements of the present invention, the present description being applicable to this variation mutatis mutandis.

In this case, for redundancy reasons or in the case of high refrigerating capacities, the step chiller assemblies 10 according to the present invention may be easily mounted in parallel in the same water loop 10 in any desired number.

Figure 6 shows the basic diagram by means of which this configuration may be realized. Obviously, each step chiller assembly 10 may operate or be automatically stopped in the case of a malfunction or depending on the regulation logic by means of a command transmitted by an automatic management mechanism which may be both centralized and spread out depending on a master/slave arrangement. Differently, considering again the solution shown by way of example in Figure 7, this is simplified compared to the solution shown in Fig. 5. It has, as described further above, the step chiller assembly 10 which incorporates inside it also the deviation valve unit 20.

This solution is simpler and more cost-effective, but does not allow removal of the step chiller assembly 10 without stopping the water flow to the peripheral units, associated with it, and therefore without interrupting operation thereof. However, in this case also, it is possible to arrange multiple step chiller assemblies 10 in parallel in a hydraulic arrangement not shown here.

It should be pointed out, however, that since in this case each of the step chiller assemblies 10 is provided with its own deviation valve unit 20, reversal of operation should be simultaneous for the whole series of step chiller assemblies 10 arranged in parallel.

Obviously, in the case of redundancy, one or more of the step chiller assemblies 10 in parallel may be excluded from the circuit by means of special shut-off cocks for any repair work or replacement.

The pumping unit 17, for safety reasons, may comprise, preferably in parallel, at least one primary pump 17a and at least one optional secondary pump 17b designed to be operated in the event of malfunctioning of the primary pump 17a. As described more fully below, during operation, the step chiller assembly 10 is connected to a water loop 101 of a refrigeration system 100 and especially to a low temperature branch 109 of the water loop 101.

The water loop 101 is connected to pumping means 102 which are configured to circulate water in the water loop 101 and may also be connected to a heat dissipator 104, referred to below also as a "rad cooler" or "dry cooler", which is connected to the water loop 101 in order to dissipate heat from water flowing inside it.

The system 100 comprises MT (medium temperature) peripheral units and LT (low temperature) peripheral units, which are respectively indicated by the reference numbers 103 and 104, as already described above with reference to the solutions of the prior art.

The step chiller assembly 10 may also comprise a non-return valve 21 or, alternatively, a motorized two-way valve arranged to prevent bypassing of liquid through the pumping unit 17 and the evaporator unit 13.

The non-return valve 21, in particular, may be provided downstream of the primary pump 17a.

From a functional point of view, if the temperature from the dry cooler measured by the general control system 18 is sufficiently low to ensure efficient operation, the general control system 18 will keep the flow path AB-A of the deviation valve unit 20 open in order to supply directly all the MT and LT peripheral units 103 and 104 downstream of the step chiller assembly 10; at the same time the general control system 18 will switch off the step chiller assembly 10 which will remain excluded from the water loop 101 by the third closed flow path B of the same deviation valve unit 20 and by the non-return valve 21 (or alternatively by a motorized two-way valve operated so as to close during this phase) which will prevent the bypassing of liquid through the pumping unit 17 and the evaporator unit 13.

When instead the temperature of the water from the dry cooler circulating in the water loop 101 is too high, the general control system 18 will open the flow path AB-B of the deviation valve unit 20, deviating the flow towards the condenser member 14 of the refrigeration unit 11; the overall flowrate of the pumping means 102 will remain more or less unchanged.

At the same time the central control system 18 will operate the pumping unit 17, namely the primary pump 17a or, if necessary, the secondary pump 17b, in the event of the first pump being ineffective, so as to supply directly the peripheral units 103 and/or 104 associated with the step chiller 10.

Moreover, the central control system 18 will start the compressor 12 via the actuating device 16 so as to keep the temperature of the water sent from the pumping unit 17 into the condensers of the associated peripheral units 103 and/or 104 at the value which is in each case considered to be most convenient; obviously the heat generated in the condenser member 14 of the refrigeration unit 11 will be released to the water flow from the water loop 101 and deviated by the deviation valve unit 20 through its port B.

This is particularly advantageous for refrigeration systems 100 where the LT peripheral units 104 comprise refrigeration machines which use carbon dioxide CO2 as refrigerating fluid.

In fact, in particular during the summer period or, in any case, in conditions where the temperature of the water in the water loop is too high, the compression ratio would tend to become excessive in particular in the LT (low temperature) peripheral units 104 and force the refrigeration cycle to work in transcritical conditions, which are much more unfavourable than the subcritical conditions which can obtained - purely by of way example - with water which is not hotter than 22°C-25°C.

In the event of breakdown of the step chiller 10 detected by the central control system 18, the deviation valve unit 20 will be automatically switched to mode AB-A - if necessary by means of a spring device - so as to allow the water from the dry cooler to pass to the peripheral units.

Moreover, preferably the deviation valve unit 20 will be provided with a device 20a for manual control of the closing element so as to be able to act in an emergency situation in the event of stoppage of the step chiller 10 or breakdown of the motor of the said deviation valve unit 20.

For obvious reasons of ease of transport, verification and installation, the refrigeration unit, the pumping unit and the control systems are preferably mounted in a single frame, casing or container. In general a step chiller assembly 10 according to the present invention may comprise valve members intercepting a connecting branch of the water side 13a of the evaporator member 13 and connected to the general control system 18, so as to be operated by it.

The said control system may be configured or programmed to operate said valve members so as to selectively connect or disconnect the connecting branch to/from a water loop 101 of a system in which said step chiller assembly 10 is incorporated when it is in operation.

In a possible variation of the step chiller assembly 10, indicated by the reference number 10a, according to the present invention, where the condenser member 14 may be configured to exchange heat, instead of with the fluid of a water loop 101, between the refrigerating fluid and the ambient air, by means of forced convection, for example by means of a radiator 22 equipped with at least one fan 23.

This variant is shown by way of example, in a non-limiting manner, in Figure 10 where the step chiller assembly 10a has its associated condenser which consists of a radiator 22, the internal circuit 22a of which has, flowing across it, the refrigerant pumped by the compressor 12 and cooled, during operation, by atmospheric air forced by the fan(s) instead of by the water from the dry cooler 105. Every other function is entirely similar to that of a water-cooled step chiller assembly 10, for example such as that shown in Figure 5, in any case described further above.

In said variant also the step chiller assembly 10 may comprise a deviation valve unit 20 which, however, will be connected to the water side 13a of the evaporator member 13.

The description of the deviation valve unit 20, mutatis mutandis, is applicable to the present variant.

Functionally speaking, the deviation valve unit 20 will admit to the associated peripheral units the water from the dry cooler 105, when it is in the mode A-AB, or the water cooled by the step chiller 1, when it is in the mode B-AB, when the incoming fluid of the water loop 101 has a temperature lower than or respectively higher than the given threshold value.

In the attached sets of drawings, in order to facilitate comprehension thereof, the same reference numbers have been used for components corresponding to or replacing those in the various variants shown in the present refrigeration system 100 or the step chiller assembly 10 or 10a.

It should be noted that, with reference to Figures 5, 7 and 10, in these figures arrows have been used to indicate the directions of outflow of the fluid in the water loop 101 where, on the left of the picture, the arrows show the direction of the fluid coming from (above) and directed towards (below) the dry cooler 104 and, on the right of the picture, the arrows show the direction of the fluid directed towards (above) and coming from (below) the peripheral units 103 and/or 104.

Overall, the refrigeration system 100 with water loop 101, according to the present invention, comprises:

- a medium temperature branch 110 connected to MT peripheral units 103 of the refrigeration system 100, in order to absorb the condensation heat thereof, and a low temperature branch 109 connected to LT peripheral units 104 of the refrigeration system 100, in order to absorb the condensation heat thereof; - pumping means 102 configured to cause circulation of a fluid, generally consisting of water and anti-freeze, in the water loop 101.

The MT peripheral units 103 may comprise refrigeration counters and/or display cases and/or cold-storage chambers for non-frozen products, while the LT peripheral units 104 may be intended to store frozen products or in any case may be intended to store products at a temperature lower than that of the MT peripheral units 103 in a manner per se corresponding to that described in connection with the prior art.

The system 100 also comprises at least one step chiller assembly 10 having the first hydraulic connectors 24a connected to the water loop 101 so that, during operation, the step chiller assembly 10 cools water flowing in the water loop 101.

The step chiller assembly 10 may be connected exclusively to the low temperature branch 109, as visible for example in Figures 8, 9 and 11, so as to be operated to serve only the latter if the temperature of the fluid flowing in the water loop 101 should be too high to ensure efficient operation of the LT peripheral units 104.

The system 100 may comprise a heat dissipator 105, preferably a rad cooler unit, connected to the water loop 101 in order to dissipate heat from water flowing in the latter. Moreover, as briefly mentioned further above, the system 100 may be configured to connect the low temperature branch 109 selectively, for example by means of the deviation valve unit 20, to the heat dissipator 105 or to the step chiller assembly 10 depending on a temperature of the water circulating in the water loop 101 downstream of the heat dissipator 105. In general, for example, valve members, collectively indicated by the common reference number 107 and visible in the attached figures, may be provided, in a manner conventional per se and described with reference to the prior art.

Clearly, the system 100 may be configured so that, during operation, the fluid of the water loop 101 is cooled exclusively by at least one step chiller assembly 10, the system 100 being without further means for cooling said water.

As mentioned further above, the MT and LT peripheral units 103, 104 could also be designed so as to comprise a refrigeration circuit which uses carbon dioxide CO2 as refrigerating fluid.

In this case, the refrigerating cycle of the MT and LT peripheral units 103, 104 will operate in subcritical mode when the temperature of the cooling water is lower than about 25°C or, with higher temperatures, in transcriticai mode, with increasing compression ratios and gradually decreasing efficiencies.

During operation, the condensers of the MT peripheral units 103 are normally cooled with water from the dry cooler 105 which, during the summer season, may reach temperatures of 40°C and higher, and therefore in all the circuit layouts examined hitherto, these MT peripheral units 102 must be configured so as to be able to operate both in subcritical mode, during cold or temperate seasons, but also in transcriticai mode during hot seasons when the temperature of the fluid/water cooled by the dry cooler 105 rises. Similarly, in a system of the conventional type, as shown in Fig. 1, the LT peripheral units 1004 as well, operating with a CO2 cycle, should be able to be configured to work also in transcriticai mode.

It can therefore be understood how the integration of a step chiller assembly 10 in a refrigeration system 100 allows the peripheral units associated with it to be supplied with water which is sufficiently cold so as to be able to operate always in subcritical mode.

This allows these peripheral units to be designed with a configuration intended to operate only in subcritical mode, and therefore with a simplified structure, which is more efficient and therefore requires an associated compressor which is smaller for the same refrigerating efficiency, with consequent cost savings.

As shown for example in Figures 8, 9 and 11, the step chiller assembly 10 may serve only the LT peripheral units 104, namely be incorporated in a refrigeration system 100 so as to supply refrigerated fluid only to the low temperature branch 109. In this case, the MT peripheral units 103 must be configured to operate also in transcritical mode.

In general, therefore, depending on the implementation requirements of the present invention, the MT peripheral units 103 must be configured to operate also in transcritical mode and the LT peripheral units 104 may be configured to operate always in subcritical mode since they are supplied always with water at a temperature sufficiently cold to obtain an acceptable compromise between the structural complexity of the MT and LT peripheral units and the related costs thereof, while ensuring the operativity of the system.

Only if, due to a constructional defect or unreliability, there is the risk that the step chiller assembly 10 may become inactive or faulty, the LT peripheral units 104 should be configured so as to be able to operate also in transcritical mode since, in the event of inactivity of the step chiller assembly 10, they would be supplied by the water which is cooled only by the dry cooler 105 and which is therefore potentially too hot - in the summer season - to allow operation in subcritical mode.

Clearly, by ensuring that the MT peripheral units are configured to operate in transcritical mode and the LT critical units 104 are configured to operate only in subcritical mode, where they are served by at least one step chiller 10, it is possible to obtain an acceptable compromise between the structural complexity of the MT and LT peripheral units and the related costs thereof, while ensuring the operativity of the system.

The system 100 may comprise: temperature sensor means, not shown, connected to the low temperature branch 109 and/or to the medium temperature branch 110 and to the general control system 18; valve members arranged to selectively connect or disconnect the step chiller assembly 10 from the low temperature branch 109 and/or to the medium temperature branch 110.

As mentioned further above, the general control system 18 may be configured and/or programmed to connect or disconnect the step chiller assembly 10 to/from the low temperature branch 109 and/or the medium temperature branch 110, if a temperature detected by the temperature sensor means is higher than or lower than a threshold temperature.

With particular reference to Figure 8, showing a possible layout of a refrigeration system 100, of the WLSC type, the water loop 101 comprises a low temperature branch 109 to which the LT (low temperature) peripheral units 104 are connected.

The step chiller assembly 10 is connected to the water loop 101, for example in parallel with the low temperature branch 109, so that, during operation, the MT peripheral units 103 are cooled by the liquid from the dry cooler 105, while the step chiller assembly 10 serves the LT peripheral units 104 which are subject to the highest compression ratios - using the regulation method described further above.

With particular reference to Figure 9, a further possible layout of the refrigeration system 100, of the WLSC type, may have the water loop 101 which comprises, in addition to a low temperature branch 109, also a medium temperature branch 110 which forms a loop connected in parallel to the low temperature branch 109 by means of the lines 101a and 101b.

The step chiller assembly 10 may therefore be connected to the low temperature branch 109, for example in parallel with the LT peripheral units 104, so as to serve them, via the low temperature branch 109, where the lines 101a and 101b branch off immediately after the outlet of the dry cooler 105.

The same Figure 9 also shows the possibility of the presence of a second step chiller assembly 10 in parallel with the first one, serving a subassembly 104a of LT peripheral units 104, via a branch-off 109a of the low temperature branch 109. ^'

This system design solution (which may theoretically comprise any desired number of step chiller assemblies in parallel) may be convenient in the case of a layout involving the peripheral units arranged in different sectors of a supermarket (such as, merely by way of example, in the case of the cold- storage rooms).

With particular reference to Figure 11 , this shows, merely by way of a nonlimiting example, a refrigeration system 100, of the WSLC type, having a step chiller assembly 10, which is for example air-cooled, as shown by way of example in Figure 10. in this case, functionally speaking, when the step chiller assembly 10 is activated, the fluid flow along the line 101a is interrupted as a result of closing of the flow path A of the deviation valve unit 20.

Likewise, not even the line 101b will be affected by any fluid flow such that the medium temperature branch 110 and the low temperature branch 109 will work in a totally independent manner.

Unlike the case where the step chiller assembly 10 is cooled with fluid from the dry cooler 105, as for example shown in Figures 5 and 7, in the event of activation of the step chiller assembly 10 the flowrate of the pumping means 102 may be reduced by an amount approximately equal to that of the pumping unit 17 with potential energy savings.

The examples illustrated above relate to the use of a step chiller assembly 10 for supplying mainly LT, i.e. low temperature, peripheral units, since they are subject to higher compression ratios and therefore, during the summer season, to greater energy inefficiency.

However, as shown by way of a non-limiting example in Fig. 12, it is possible to apply the use of the step chiller assembly 10 also to all the MT and LT peripheral units 103 and 104, i.e. whether they be of the medium temperature or low temperature type. This may be convenient in general if high external temperature peaks are expected and, in particular, in the case of peripheral units which use carbon dioxide as refrigerating fluid since, by being able to operate constantly in subcritical mode and therefore with a lower delivery pressure, and a lower compression ratio, compared to that which otherwise would be obtained during the hotter hours, it is possible to obtain in each peripheral unit 103 and 104 both a greater energy efficiency and the possibility of using compressors with a smaller engine capacity.

A step chiller assembly 10, according to the present invention, must be studied and designed specifically for each contingent application, in particular: - by designing optimum dimensions of the main components (compressors), pump(s), condenser or gas cooler, in the case of CO2 transcritical cycles, evaporator);

- by providing an internal regulation and control system able to adapt in a precise manner the refrigerating power output to the condensation heat disposal requirements of the user appliances which are connected; - by coordinating the functionalities with the centralized control device of the entire system; and also a constructional design of the hydraulic circuit comprising valves and devices suitable for connecting or disconnecting the chiller in the hydraulic circuit depending on the temperature of the water output from the dry cooler.

It has therefore been shown how the present invention is able to fulfil the predefined task and objects.

The invention thus devised may be subject to numerous modifications and variations, all of which fall within the scope of protection of the attached claims. Moreover, all the details may be replaced by other technically equivalent elements.

In practice, the particular forms and dimensions may be varied depending on the particular requirements and the state of the art.

Where the constructional characteristics and the techniques mentioned in the following claims are followed by reference numbers or symbols, these reference numbers or symbols have been assigned with the sole purpose of facilitating understanding of the said claims and consequently they do not limit in any way the interpretation of each element which is identified, purely by way of example, by said reference numbers or symbols.

Claims

1. Step chiller assembly (10) for a refrigeration system (100) with water loop (101) which comprises:

- a refrigeration unit (11) comprising at least one compressor (12) and an evaporator member (13) configured to exchange heat between a refrigerating fluid and a fluid flowing in a water side (13a) thereof;

- an actuating device (16), which is connected to said compressor (12) in order to control the operation and operating safety thereof;

- a general control system (18) connected to said refrigeration unit (11 ) and able to be connected to temperature and pressure transducers and/or sensors; where said general control system (18) is configured and/or programmed to operate said step chiller assembly (10), in particular to activate it, to regulate the refrigerating capacity thereof and to optimize the operation thereof depending on data received from said sensors and/or transducers which, during operation, are incorporated in said step chiller assembly (10) and/or in said refrigeration system (100), in order to detect and monitor the operation thereof.

- a pumping unit (17) connected to the water side (13a) of said evaporator member (13) so as to force water to circulate across said water side (13a) and from/into a water loop (101) of a refrigeration system (100) to which said step chiller assembly (10) is connected when in operation; where said step chiller assembly (10) is configured to form a single manufactured unit available independently of a refrigeration system (100) so as to be integrated therein or separate therefrom.

2. Step chiller assembly (10) according to claim 1, wherein said actuating device (16) comprises alternatively - at least one inverter, in which case said at least one compressor (12) can be operated at a variable speed upon driving of a respective inverter of said at least one inverter or

- at least one ON/OFF actuating member, in which case said at least compressor (12) is configured to work at a fixed speed.

3. Step chiller assembly (10) according to one of the preceding claims which comprises:

- first hydraulic connectors (24a) hydraulically connected to the water side (13a) of said evaporator member (13) and configured to connect the latter to a water loop (101) of a refrigeration system (100);

- a frame or casing having, fixed thereto, said refrigeration unit (11), said actuating device (16), said general control system (18), said pumping unit (17) and said first hydraulic connectors (24a) so as to form a single manufactured unit. 4. Step chiller assembly (10) according to one of the preceding claims, wherein said refrigeration unit (11) comprises a condenser member (14) configured to exchange heat between said refrigerating fluid and a fluid flowing in a water side (14a) thereof; said step chiller assembly (10) comprising second hydraulic connectors (24b) connected hydraulically to the water side (14a) of said condenser member (14) and configured to connect the latter to a water loop (101) of a refrigeration system (100), in order to dissipate heat from said refrigerating fluid to a fluid flowing in the water side (14a) of said condenser member (14).

5. Step chiller assembly (10) according to claim 4, which comprises a deviation valve unit (20) which can be connected to a water loop (101) of a refrigeration system (100) in order to connect or hydraulically disconnect said step chiller assembly (10) to/from said water loop (101 ).

6. Step chiller assembly (10) according to claim 5, wherein said deviation valve unit (20) is connected:

- by means of its flow path AB, to a first one of said second hydraulic connectors (24b) which is designed to be connected to said water loop in order to receive fluid therefrom;

- by means of its flow path A, to a first one of said first hydraulic connectors (24a) which is designed to introduce refrigerated fluid, from the water side (13a) of said evaporator member (13), into the water loop (101);

- by means of its flow path B, to the water side (14a) of said condenser member (14); wherein said deviation valve unit (20) can be selectively operated:

- in a mode AB-A where said flow path AB is connected exclusively to said flow path A, so as to cause bypassing of said step chiller assembly (10) with respect to said hydraulic connectors (24a, 24b) which, during operation, connect it to a water loop (101);

- in a mode AB-B where said flow path AB is connected exclusively to said flow path B, so as to connect the first of said second hydraulic connectors (24b) to the water side (14a) of said condenser member (14) such that, during operation, the latter is cooled by fluid supplied from said water loop (101), via the first one of said second hydraulic connectors (24b).

7. Step chiller assembly (10) according to claim 6, wherein said deviation valve unit (20) comprises a three-way valve or two two-way valves which are coupled together.

8. Step chiller assembly (10) according to one of claims 6 and 7, wherein said deviation valve unit (20) is connected to said general control system (18) so as to be operated by it; said general control system (18) being configured or programmed to operate said deviation valve unit (20) selectively:

- in said mode AB-A if, during operation, said general control system (18) receives a reading of a temperature of the fluid flowing in said water loop (101 ) lower than a fixed threshold, or lower than or the same as it;

- in said mode AB-B if, during operation, said general control system (18) receives a reading of a temperature of the fluid flowing in said water loop (101) higher than or the same as said fixed threshold or, respectively, higher than it.

9. Step chiller assembly (10) according to one of claims 1-3, wherein said refrigeration unit (11) comprises a condenser member (14) configured to exchange heat between said refrigerating fluid and the ambient air, by means of forced convection.

10. Step chiller assembly (10) according to one of the preceding claims, comprising shut-off cocks (19) arranged to connect and disconnect hydraulically said step chiller assembly (10) to/from a water loop (101) of a refrigeration system (100). 11. Step chiller assembly (10) according to one of the preceding claims, wherein said pumping unit (17) comprises, in parallel, at least one primary pump (17a) and at least one optional secondary pump (17b) designed to be operated in the event of a malfunction of said primary pump (17a).

12. Step chiller assembly (10) according to one of the preceding claims, comprising a non-return valve (21) or, alternatively, a motorized two-way valve arranged so as to prevent liquid being bypassed through said pumping unit (17) and said evaporator unit (13).

13. Refrigeration system (100) with water loop (101) which comprises:

- a medium temperature branch (110) connected to MT peripheral units (103) of said refrigeration system (100), so as to absorb condensation heat thereof, and a low temperature branch (109) connected to LT peripheral units (104) of said refrigeration system (100), so as to absorb condensation heat thereof;

- pumping means (102) configured to cause the water to circulate in said water loop (101); said system (100) comprising at least one step chiller assembly (10), according to one of the preceding claims, having said first hydraulic connectors (24a) connected to said water loop (101) so that, during operation, said step chiller assembly (10) cools water flowing in said water loop (101).

14. System (100) according to claim 13, wherein said step chiller assembly (10) is connected to the water loop (101) so that, during operation, it serves exclusively said low temperature branch (109) namely provides refrigerating power only to said LT peripheral units (104).

15. System (100) according to one of claims 13 and 14 which comprises a heat dissipator (105), preferably a rad cooler or dry cooler unit, connected to said water loop (101) in order to dissipate heat from the fluid flowing therein.

16. System (100) according to claims 14 and 15, configured to connect said low temperature branch (109) selectively to said heat dissipator (105) or to said step chiller assembly (10) depending on a temperature of the water circulating in said water loop (101) downstream of said heat dissipator (105). 17. System (100) according to one of the preceding claims, wherein said MT and LT peripheral units (103, 104) comprise a CO2 refrigeration circuit and preferably said MT and LT peripheral units (103, 104) are configured to operate using a CO2 refrigerating cycle in subcritical mode or in both subcritical and transcritical operating conditions.

18. System (100) according to one of claims 13 to 17, which comprises:

- temperature sensor means connected to said low temperature branch (109) and/or to said medium temperature branch (110) and to said general control system (18);

- valve members (19, 20) arranged to selectively connect or disconnect said step chiller assembly (10) from said low temperature branch (109) and/or to said medium temperature branch (110); wherein said general control system (18) is configured and/or programmed to connect or disconnect said step chiller assembly (10) from said low temperature branch (109) and/or to said medium temperature branch (110), if a temperature detected by said temperature sensor means is higher than or lower than a threshold temperature, respectively.

19. System (100) according to one of claims 13 to 18, wherein said water loop (101) comprises:

- a low temperature branch (109),

- a medium temperature branch (110) which forms a loop connected in parallel with said low temperature branch (109) by means of lines (101a), (101b); wherein said at least one step chiller assembly (10) is connected to said low temperature branch (109), preferably in parallel with said LT peripheral units (104) so as to serve them, via said low temperature branch 109, where said lines (101a, 101b) branch off immediately downstream of the outlet of said heat dissipator (105).

20. System (100) according to claim 19, which comprises at least one first step chiller assembly (10) and at least one second step chiller assembly (10); wherein said low temperature branch (109) comprises at least one branch (109a) which serves at least one subassembly (104a) of LT peripheral units

(104); wherein said first step chiller assembly (10) is connected to said branch (109a) so as to serve exclusively the subassembly (104a) of said LT peripheral units (104), while the second step chiller (10) is connected to the remaining portion of said low temperature branch (109) so as to serve exclusively LT peripheral units (104) not belonging to said subassembly (104a).