ES2279076T3 - LOW TEMPERATURE REFRIGERATORY INSTALLATION IN PARTICULAR FOR FREEZING, OVERHEATING AND STORAGE OF PRODUCTS, SUCH AS FOOD PRODUCTS. - Google Patents

Abstract

In a first phase a classic circuit which has a axial compressor, closed economizer and matched evaporator is used to freeze a fresh product to -18 degrees C. When the temperature has been attained the evaporator is automatically connected to the low pressure circuit of a booster - 65/- 20 degrees C and the compressor and economizer serve as a high pressure booster stage

Description

Low temperature refrigeration installation in Particular for freezing, freezing and storage of products, such as food products.

The present invention relates to a low temperature refrigeration installation in particular for freezing, over-freezing and storage of products, such as food products according to the preamble of the claim 1. An installation of this type is disclosed to from document EP-A-0 718 568.

Low temperatures, particularly between -20ºC and -60ºC are particularly interesting in the field of Agricultural food In fact, it has been verified since time that keeping food products to these temperatures allow better preservation of organoleptic qualities of these products. Low temperatures like these are also useful, particularly in the field of chemistry or metallurgy. If its use is still limited, it is due to the fact that the refrigeration facilities, which allow to cover large temperature ranges, that is from room temperature up to -60ºC, expensive, complex and overall particularly bulky.

Currently, two families of refrigeration facilities to cover large margins of temperatures as illustrated in particular by the article by O.M. Magnussen "Superfreezing low temperature technology" scanref, Volume 21, No. 4, September 1992, pages 34 to 41.

The first family of refrigeration facilities it is constituted by a double stage facilities with bottle intermediate. These facilities, also called "booster", they consist of a low pressure stage compressor and by a single-stage high pressure compressor, separated or by double stage compressors, called "compound" with screw or with piston. In the partial injection cycle, the flow rate of mass of fluid displaced by the low pressure compressor is subcooled under the condensation pressure in a exchanger submerged in the liquid of the intermediate bottle. Only the difference of the masses at high pressure and low pressure undergoes the expansion of high pressure to pressure intermediate, hence its name of partial injection. As the system It operates at low suction pressures, resulting in use of a large volume of gas that needs some compressors particularly bulky.

Another family of refrigeration facilities has Come to impersonate this first family of facilities. It is about of refrigeration facilities called "cascade". He cascade system features two or more cooling agents different that circulate in individual circuits. These individual circuits are arranged side by side in such so that the capacitor installed in the low circuit temperature is cooled by evaporating refrigerant fluid of the other circuit in which the temperature is higher. A installation of this type is described more particularly in the US-A-2,434,221. Of this mode, in this document, in particular in figure 1, appears clearly a first circuit consisting of a compressor, represented as 1 in the figures, by a capacitor, by a expansion valve 6 and by an evaporator represented as 7. Another refrigerant fluid circuit, called the second circuit, completely independent is represented by references 9 to 20 in which reference 9 represents the compressor, the reference 16 an expansion valve and reference 17 the evaporator used to produce cold in the cold chamber. It is then verified, in a circuit of this type, that the second circuit condenser is constituted by the evaporator of the first circuit. Thus, the fluids of these two circuits circulate in individual independent circuits even if the evaporator of one of the circuits serves as fluid condenser of the other circuit. The facilities of this type are therefore complex because of the presence of two refrigerating fluids and an expansion vessel.

An objective of the present invention is therefore both propose a refrigeration installation whose conception allows cover a wide range of temperatures while allowing use of a single refrigerant fluid inside of a reduced volume installation compared to known double stage or cascade installations until the day of today.

Another objective of the present invention is propose a refrigeration installation whose conception allows the Obtain a reliable installation, with good performance, of reduced volume that presents interesting returns.

For this reason, the invention aims at a low temperature refrigeration installation in particular for freezing, over-freezing and storage of products, in particular foodstuffs, according to claim one.

Thanks to the conception of an installation of this type, the commissioning of the second circuit is carried out in ideal conditions since the refrigeration installation is already at regime at the level of the temperature of the refrigerant fluid, in particular to the temperature level of the economizer bottle and of the evaporation temperature that allows the cold chamber range from now on a temperature of the order of -30 ° C. From In this way, the evaporator passes successively and automatically of a fluid feed by means of a first circuit called freezing or cooling classic food by means of a circuit called over-freezing or subcooling at low temperature. The minor being cooling power of phase 2 than the cooling power of the phase 1, delta T, difference between evaporation temperature and the temperature of the air at the evaporator inlet is reduced by therefore clearly in phase 2, which ensures performance Excellent installation. Moreover, an installation of this type is versatile since it can work permanently in form of a classic cooling installation if the second circuit is never activated.

The invention will become more clearly from manifest from the following description of the examples of realization, referring to the drawings attached in the that:

Figure 1 represents a schematic view of a refrigerating installation according to the invention;

Figures 2A to 2E represent so schematic the detail of a refrigeration installation according to the invention, these figures should be read by arranging them at side of the other in order to rebuild the circuits complete.

As mentioned above, the Refrigeration installation, object of the invention, is intended more particularly freezing, over freezing and product storage, particularly products food. This installation comprises at least two circuits of circulation of refrigerant fluid. These circuits are represented in figure 1, one in continuous line, the other in continuous line with a dashed line consisting of a line and a point. The first circuit serves more particularly for a first cooling phase that constitutes for example a phase of product freezing to a temperature close to -18ºC in the nucleus. This first phase is followed by a second phase in the that the product is subcooled from a temperature of -18ºC at a temperature close to -45ºC. The second circuit therefore allows to reach negative temperatures in absolute value above the temperatures of the first circuit.  When the temperature in the core of the product or the temperature of evaporation of the installation reaches -18ºC, the installation is automatically connect on the second circuit.

The two fluid circulation circuits refrigerator which, in the examples shown, are circuits of the compression type, each comprises, arranged in series, by at least one compressor 2, a condenser 3, an expansion valve 6 and an evaporator 1. Obviously, the expansion valve 6, which it serves to feed the evaporator 1, it could have, of equivalent way to be replaced by a pump or by a thermosiphon system (flood)

As the figures illustrate, these circuits are common in a part of their length and are fed by the same refrigerant fluid suitable for feeding the first circuit and / or the second circuit. These first and second circuits comprise, in their common section that extends between the letters X and Z, taken in the direction of fluid flow in the Figure 1, at least the evaporator 1 used for production of cold. This evaporator 1 common to the two circuits is thus suitable to be fed with fluid by one or the other of the circuits depending on the desired reference temperature.

In the examples shown, these circuits First and second refrigerators are compression type and they comprise at least one evaporator 1, a compressor 2, a condenser 3 and an expansion valve 6 common to both circuits The second circuit is constituted between the evaporator 1 and compressor 2, taken in the direction of fluid flow, by a derivation of the first circuit. The XZ section common to the two circuits implies that the fluid of the first and second circuit circulates at the outlet of compressor 2 through a capacitor 3 associated with a reservoir 4 and then through a economizer 5 or intermediate bottle before flowing into the expansion valve 6 and then in the production evaporator 1 of  cold. At the height of the economizer 5 or the intermediate bottle 5, a joint is provided that returns a part of the fluid to the Compressor for both circuits. However, the conception of this union differs from one circuit to another.

The second circuit is constituted between the evaporator 1 and compressor 2 by a derivation of the first circuit, this derivation corresponding to section ZY. This second circuit is equipped, in its derivation, with a compressor 7 piston connected to the outlet to an intermediate bottle 5, connected in turn shutter to the channel input 10 suction of compressor 2 common to the first and second circuits The compressor 2 common to the first and second circuits it is constituted, as for itself, by a compressor of screw and by an economizer 5. In the examples shown, the economizer 5 serving the first circuit and bottle 5 intermediate of the second circuit are preferably constituted for a single and equal capacity. The screw compressor 2 also It is equipped with a 10 'medium low pressure suction channel pressure that can be sealed, in which the first is connected circuit at the exit of economizer 5 (section WY '). This channel WY 'suction is connected to economizer 5 so that forms in the first circuit a recirculation loop of at minus a part of the fluid leaving the condenser 3 in the direction of the compressor 2. Obviously, these circuits can be activated from selective mode depending on the cooling temperature desired. Activation is preferably obtained by actuation of at least one sealing element 8, 9 placed in at least one of the circuits. In this way, the operation of a refrigeration installation of this type can be describe in general as follows. The refrigerant fluid circulates at the height of the first circuit between the compressor 2, the condenser 3, reservoir 4, economizer 5, valve expansion 6 and evaporator 1. At the outlet of evaporator 1, the fluid returns directly to the inlet of compressor 2 taking the ZY section in figure 1. A part of the vapors contained in economizer 5 re-enters the circuit and feeds meanwhile the 10 'medium pressure suction channel of the compressor. Thus, a part of the fluid of this first circuit circulates again in the part of compressor 2, condenser 3, tank 4, economizer 5 thanks to the WY 'connection between economizer 5 and compressor 2. This union is the type that can be shutter and is equipped with a shutter element 8. This first circuit therefore corresponds to the parts of the circuit equipped with 8 white floodgates that are represented in open position. When the evaporation temperature of the installation reaches a predetermined value or corresponds to a default operating time, the second is activated circuit. The screw compressor part 2 and the bottle 5 economizer serve as a high pressure stage in the booster whose low pressure part is no longer calculated for integrality of the over-freezing but only to ensure the Sub-cooling of the products. During the activation of this second circuit, gate 8, represented blank in figure 1, they are closed while the floodgates 9 black are open. The fluid then follows a route according to what has been represented with a continuous line and a dotted one and a point in figure 1. The fluid at the outlet of the evaporator 1 is carried through a piston compressor 7 after having passed through a closed gate 9 when the first circuit is activated and open when the second circuit is activated. The fluid at the outlet of this compressor 7 of pistons is taken to an intermediate bottle 5. This fluid, at the exit of the intermediate bottle 5, it is taken back to the screw compressor 2 inlet. This part WY between the bottle 5 and the compressor 2 inlet is also equipped with an element 9 shutter to prevent a backflow of the first circuit in the second circuit when the first circuit is activated. To screw compressor 2 outlet, the fluid follows the same path that in the case of the first circuit, namely, passes through of the capacitor 3 then by the tank 4 before reaching the Intermediate bottle or economizer to then pass through the expansion valve 6 and feed the evaporator 1.

Thus, at the exit of the economizer 5 or of the intermediate bottle, a WY part of the circuit, in the case of second circuit, return the refrigerant fluid to the inlet of the screw compressor 2 at the height of the suction channel 10, while in the case of the first circuit, this same output of bottle 5 or economizer 5 brings the fluid to the inlet of the compressor 2 by means of a suction channel 10 'called medium pressure that also equips screw compressor 2. This circuit part is represented in WY '. The WY part of the second circuit allows screw compressor 2 to operate without economizer becoming the high pressure compressor of a two-stage installation whose first stage is constituted by the compressor 7. The WY 'part of the first circuit allows a aspiration of the gases contained in economizer 5 and its injection into compressor 2 at the height of the suction channel 10 ' medium pressure

In the examples shown, the fluid Refrigerator used common to the first and second circuits is R 404 A. The physical properties of this fluid are described in particular in the work "Ashrae Fundamentals Handbook" of 1997. This fluid allows operation with moderate pressures (18.5 absolute bars for a condensing temperature of -40ºC), which is compatible with all material standards Fridge.

It should be noted that the switching of the first circuit to the second circuit and vice versa is done more beyond a predetermined temperature measured and / or calculated. At second case, the operating time can be taken into account of the first circuit, activating the second circuit beyond a predetermined duration of which it is assumed that it has allowed to reach an evaporation temperature included within a predetermined range.

The detailed conception of an installation of this type will be described hereinafter referring to the Figures 2A to 2E. Thus, Figures 2A to 2E represent the refrigeration scheme of realization of a refrigeration system of a tuna vessel dedicated to deep sea fishing. This type of boats They go fishing for a duration of approximately 15 days. To exit of the port, the warehouses C1, C2 in which the Fish are at room temperature. These wineries should so both reach a temperature close to -60ºC. At During the fishing periods, each of the tunnels with fresh tuna, this tuna being fresh at a temperature ambient. Once the tunnel has been filled, the stage of freezing by activating the first circuit of the installation and then the freeze stage by activation of the second installation circuit. Once the freezing and freezing cycles are over, the tuna is then driven to the storage warehouse to -60 ° C.

The two tunnels are designed for example to present a freezing capacity of 2 tons per cycle at -45 ° C in the core. The wineries, represented here in form winery C1 and winery C2, for their part present some volumes of order of 100 m3 at -60 ° C. The winery C3 of baits presents for its part a volume of 10 m 3 at -20 ° C. The outside temperature is of 35ºC and the external hygrometry is 80%. The coefficient of Thermal insulation of refrigerated rooms K equals 0.2 kCal / hour.m 2.

The detailed thermal balance of a tunnel in phase 1, that is to say with a tuna, whose temperature is brought from + 30ºC to -18 ° C, can be described as follows:

Interior dimensions: 4, 1,3, 6 \ cdoth = 1,7 m.

External dimensions: 4.7, 4.2 \ cdoth = 2.3 m.

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           losses: 23,876 kCal / 21 h

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           air renewal: 908 kCal / 21 h.

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           thermal equivalent of motor fan work: 119,196 Cal / 21 h.

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           2,028 kg of tuna from + 30ºC to -18ºC: 177,855 kCal / 21 h.

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           TOTAL: 321,835 kCal / 21 h

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           that is: 15,325 kCal / h.

The detailed thermal balance of a tunnel in phase 2 corresponding to a sub-cooling stage of tuna from -18ºC to -45ºC, it can be described as follows:

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           losses: 10,000 kCal / 6 h

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           thermal equivalent of the work of motor fans: 22,704 kCal / 6 h.

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           2,028 kg of tuna from -18ºC to -45ºC: 22,450 kCal / 6 h.

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           TOTAL: 55,154 kCal / 6 h

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           that is: 9,192 kCal / h.

The summary of the thermal balance of the different Positions can therefore be established as follows:

Tunnel No. 1 or No. 2: phase 1, freezing at -18 ° C in the core.

Duration: 21 h; Required power: 17.8 kW.

Phase 2: subcooling from -18ºC to -45ºC in the core.

Duration: 6 h, Required power: 10.7 kW.

100 winery m 3: Power required 8.3 kW.

80 winery m 3: Required power 7.5 kW.

10 hold m 3: Required power 1.6 kW.

The installation is also equipped with two low-pressure piston compressors 7 (see Figure 2c), for example Mycom brand, type F8WA. The rotation speed can be of the order of 1,450 rpm, the operating regime of -65ºC / -20ºC with cooling capacities of 16.7 kW and an absorbed power of
16.5 kW

The power regulation of the compressors of This type can be 50, 75 and 100% and motor power Electric drive is 22 kW.

The installation is also equipped with three 2 high pressure screw motor compressors of which one as spare or support. These 2 motocompressors can be branded Bitzer, type OSN5361-K with a speed of 2,900 rpm rotation. When these 2 compressors work with economizer on the first circuit, have a power refrigerator of 34.7 kW and an absorbed power of 23.5 kW. When they work without economizer in cooperation with bottle 5, they have a cooling capacity of 45.3 kW and a power absorbed of 23.1 kW, a power regulation of between 75 and 100% and a power of the electric motor drive form B35 of 30 kW

Each of the tunnels, represented in T1, T2, is equipped with a ventilated battery or evaporator 1, fed in direct expansion and defrosting in the air. Nail electric dampers placed in the liquid lines and of suction allow to automatically pass the first circuit of classic freezing or cooling to the second circuit of intense subcooling In order to avoid the pressure losses, electric suction dampers are motorized integral step gates. Each evaporator 1 is equipped with Liquid-Steam exchanger 18, with so that the temperature of the gases aspirated by the low pressure piston compressors not less than -50 ° C.

Each of the wineries, represented as C1, C2, C3 in the figures, is equipped with a ventilated battery 1 ', fed in direct expansion and electric defrosting. By that is why these batteries are each equipped with a thermostat of safety that cuts the power supply of the resistors in the case high evaporator temperature. Electric gates placed on the liquid and suction lines also allow start lowering the temperature of the cellars to -25ºC before the output to fish using the compressor circuit 2 of screw with economizer 5, before using the low circuit booster pressure to reach the temperature of -60ºC. As that for the tunnels and for the same reasons, each evaporator of The wineries C1, C2 is equipped with an exchanger Liquid-Steam 18.

The C3 cellar is equipped with a battery ventilated 1 'fed in direct expansion and defrosting electric This battery is of course connected only over The screw compressor circuit with economizer. Each of these positions is equipped with a thermostat 12 (thermostat + temperature indication). The cellars at -60ºC are also equipped with a temperature recorder that allows control For the buyer of the freight.

The engine room comprises a series of low pressure compressors corresponding to the 7 piston compressors of the general scheme. These compressors of piston is provided with a shock resistant bottle of liquid 14 with liquid subcooler coil and are each equipped with an oil cooler 15 Powered in direct expansion, with a level controller oil 16 in the crankcase, the eventual excess of oil being in the compressor housings injected into the compressor suction Priority screw, with an oil separator 17.

These 7 compressors work in cooperation with an intermediate bottle economizer 5. The latter is provided of a can of refrigeration of the gases compressed by the low pressure compressors 7, from a liquid feed to high pressure with a liquid level controlled by a float switch 19. A second float switch 20 ensures the safety of the compressors when the level is too high  tall. This intermediate economizer bottle 5 is still provided with a constant pressure gate 21 in order to limit the pressure at -20 ° C in the present case. There are also the classic elements such as safety valves, indicators liquid levels ...

The installation also includes three 2 identical screw motor compressors that can also work  during the classic freezing regime adopted during the first phase, that is from + 40ºC to -34ºC with economizer, either in simple stage without economizer at the rate from -20ºC to -40ºC when they ensure the operation of the high pressure stage of the booster, during phase 2 of the tunnels, phase of intense subcooling or when a cooling of the cellars at -60ºC. This unit is equipped with a common oil separator 23, which facilitates the returns of automatic oil and with a single oil cooler 24. The Compressors are also provided with a bottle resistant to liquid blows 25 with subcooler coil liquid. An oil separator 26 placed in the recirculation general allows automatic recovery of dissolved oil in the freon of the intermediate bottle thanks to an ejector system 27.

The installation also includes a condenser 3 multi-tubular condenser type forming a Deposit. Condensation of high pressure expelled gases It is secured by this seawater condenser. This capacitor makes the job of deposit and also allows the thermosiphon feed of the oil cooler.

The refrigeration system obviously allows the simultaneous operation of all positions in all cases that may arise, such as, for example, wineries tuna storage at -60ºC, a bait cellar in service, a tunnel # 1 in sub-cooling phase intense (phase 2) and a tunnel # 2 in the classic freezing phase (phase 1).

The duration of operation of the tunnels in phase 1, open white electric dampers, gates electric black closed according to figure 2a can be regulate with a "coupatan" type watch which, once the set time has run out, it passes the same tunnel to the phase 2. Then the black electric gates open, it the white ones close, according to figure 2a. The regulation of Low pressure compressor power is realized thanks to the pressure sensor 28 according to figure 2b. Power regulation of the 2 high pressure compressors is made thanks to the sensor pressure 29 according to figure 2d. The power regulation of compressors that work with economizer is made thanks to the pressure sensor 30 according to figure 2c. Each of the three screw compressors 2, according to figure 2d, can also operate both at high pressure stage of the booster system, open electric gate 31 (corresponding to item 9 of the Figure 1), gates 32 and 33 closed (corresponding to the elements 8 of figure 1), as in a system with economizer (circuit # 1), open doors 32 and 33 (corresponding to elements 8 of figure 1), electric gate 31 closed (which corresponds to element 9 of figure 1).

Claims (5)

1. Low refrigeration installation particular temperature for freezing, over freezing and  the storage of products, particularly food, said installation comprising at least two circuits refrigerant circulation of refrigerant fluid, serving one of they, called first circuit, for a first cooling up to a temperature preferably preferably close to -18 ° C, the other, called second circuit, for subcooling preferably from -18 ° C to about -45 ° C, comprising each refrigeration circuit of the compression type, arranged in series, at least one compressor (2), a condenser (3) and a evaporator (1) through which a refrigerant fluid circulates, the evaporator (1) being fed by an expansion valve (6) or by means of a pump or thermosiphon, these being common refrigeration circuits in one part (XZ) of its length and being fed by the same refrigerant fluid suitable for alternatively circulate in one or the other of said circuits, these circuits comprising in their common section (XZ) at least a condenser (3), preferably an expansion valve (6), and the evaporator (1) used for cold production, being this evaporator (1) fed with fluid by one or the other of said circuits depending on the desired cooling temperature, characterized in that the first and second refrigeration circuits further comprise a common compressor (2), consisting of a screw compressor and an economizer (5), this screw compressor (2) being in the inlet equipped with a channel (WY ') of medium pressure suction that can be sealed, sealed in the activated state of the second circuit, this suction channel (WY ') being connected to the economizer (5) such that a recirculation loop is formed in the first circuit less a part of the fluid leaving the condenser (3) in the direction of the compressor (2), and because the second circuit is constituted between the evaporator (1) and the compressor (2), taken in the direction of fluid circulation by means of a bypass of the first circuit, this second circuit being equipped, at its branch, with a piston compressor (7) connected at the outlet to an intermediate bottle (5), connected in turn so that it can be sealed to the input d and a compressor suction channel (WY) common to the first and second circuits. 2. Refrigeration installation according to claim 1, characterized in that the first and second circuits can be selectively activated according to the desired cooling temperature, the activation being preferably obtained by actuating at least one element (8, 9) of shutter placed in at least one of the circuits. 3. Refrigeration installation according to one of claims 1 and 2, characterized in that the economizer (5) and the intermediate bottle (5) of the second circuit are constituted by a single and same capacity. 4. Refrigeration installation according to one of claims 1 to 3, characterized in that the first circuit is equipped in the area between the evaporator (1) and the compressor (2), downstream of the branch intended to constitute the second circuit, with a sealing element (8), such as a valve, actuated in the direction of a closure beyond the predetermined temperature measured and / or calculated in particular depending on the operating time of the first circuit. 5. Refrigeration installation according to one of claims 1 to 4, characterized in that the refrigerant fluid used common to the first and second circuits is R 404 A.